DESCRIPTION
Title of Invention: WIRELESS COMMUNICATION SYSTEM AND
WIRELESS COMMUNICATION METHOD
Technical Field
5 [OOOl]
The present invention relates to a wireless communication system
and a wireless communication method and, more particularly, to a wireless
communication system obtained by separating the functions of a wireless
base station into a wireless control device and a wireless device, and a
10 wireless communication method.
Background Art
[00023
In a wireless communication system which performs
communication using wireless terminals such as mobile phones and
15 smartphones, remote base station equipment has been developed.
Regarding this technique, NPL 1 discloses radio base station equipment for
a remote LTE (Long Term Evolution) system. In NPL 1, radio BDE (Base
Station Digital Processing Equipment) located on the side of the center (for
example, a core network) and a plurality of pieces of RRE (Remote Radio
20 Equipment) located near antennas are connected to each other via optical
fibers using the CPRI (Common Public Radio Interface) scheme.
[0003]
CPRI refers herein to an open specification of an interface between
a wireless control unit (REC: Radio Equipment Control) and a wireless unit
25 (RE: Radio Equipment) in a radio base station and is described in detail in
NPL 2. NPL 3 discloses a C-RAN (Radio Access Network). The
C-RAN is formed by connecting a DU (Digital Unit) cloud located on the
side of the center (for example, a core network) to an RU (Radio Unit)
distributed for each antenna site via a wideband, low-latency transport
2
network. NPL 4 discloses the specifications of an E-UTRAN (Evolved
Universal Terrestrial Radio Access Network) used in LTE.
[0004]
In NPL 1, the pieces of RRE (Remote Radio Equipment) simply
5 execute optical/electrical conversion and RF (Radio Frequency) functions
and the BDE executes other digital signal processing functions (error
correction coding, radio framing, data modulation, frequencyltime
conversion, and MIMO (Multiple Input Multiple Output) processing).
NPL 2 also discloses a configuration obtained by similar function sharing.
10 [0005]
PTL 1 discloses a digital fiber wireless transmission system which
assumes a network architecture connecting a slave station to a radio base
station (master station) over a cable extending from the master station, and
includes a master device connected to a mobile communication network,
15 one or more slave station devices capable of radio communication with a
mobile communication terminal, and a transmission line connected
between the master device and each slave device and capable of
bidirectional digital transmission. Note that in PTL 1, a signal
processing circuit in the master device processes main signals (included in
20 transmission frames) communicated between the signal processing circuit
and the slave device connected to a transmission control circuit, directly as
digital signals by signal processing such as signal demodulation,
encodingldecoding, error detection/correction, and channel
termii~atioi~li~~ultsiepplaer ation according to the radio schcmc and protocol
25 used.
Citation List
Patent Literature
[0006]
PTL 1 : Japanese Unexamined Patent Application Publication No.
Non-patent literature
[0007]
NPL 1: "Development of Wireless Base Station for LTE System Usable
5 with W-CDMA System," NTT DOCOMO Technical Journal Vol. 19, No. 1,
URL:
https://www.nttdocomo.co.jp/corporate/technology/rd/technical journallb
n/vo119~1/020.html
NPL 2: "CPRI Specification V6.0 (2013-08-30)," Common Public Radio
10 Interface (CPRI)
NPL 3: "SUGGESTIONS ON POTENTIAL SOLUTIONS TO C-RAN BY
NGMN ALLIANCE," NGMN Ltd (Next Generation Mobile Networks),
URL:
http://www.ngmn.org/uploads/media/NGMN~CRAN~Suggestion-sP ~ooten
15 ntial - Solutions - to-CRAN.pdf
NPL 4: "3GPP TS 36.300 V12.1.0 (2014-03)," 3GPP (3rd Generation
Partnership Project)
Summary of Invention
Technical Problem
20 [0008]
In the above-mentioned patent literature and non-patent literatures,
the device (for example, the RRE, the RE, and the slave device) on the
antenna side simply performs RF processing and the device (for example,
the BDE, the REC, and the master device) on the center side performs other
25 types of digital signal processing. This increases the rate of data
transmillad bclwccri lhc dcviac un tllc ccntcr side and the device on the
antenna side. Therefore, according to the techniques described in the
above-mentioned patent literature and non-patent literatures,
communication between the device (wireless control device) on the center
side and the device (wireless device) on the antenna side may not be
conducted efficiently.
The present invention is made to solve the above-described problem
5 and object of the present invention is to provide a wireless communication
system and a wireless communication method for efficiently performing
communication between a wireless control device and a wireless device.
Solution to Problem
[OO lo]
10 A wireless communication system according to the present
invention includes a wireless control device, and at least one wireless
device which is connected to the wireless control device via a transmission
line and wirelessly communicates with a wireless terminal, the wireless
control device including wireless resource allocation means for allocating
15 a wireless resource used by the wireless device in wirelessly
communicating with the wireless terminal, and wireless resource
instruction means for sending an instruction for allowing use of the
allocated wireless resource to the wireless device, and the wireless device
including wireless signal processing means for executing processing to
20 perform wireless communication using the allocated wireless resource, on
data to be sent to the wireless terminal, on the basis of the instruction from
the wireless control device, and wireless transmission means for
converting a signal processed by the wireless signal processing means into
a wireless signal and transmitting the wireless signal to the wireless
25 terminal.
[ O O l 11
Another wireless communication system according to the present
invention includes a wireless control device, at least one wireless device
which wirelessly communicates with a wireless terminal, and a relay
5
device which is interposed between the wireless control device and the
wireless device, connected to the wireless control device via a first
transmission line, and connected to the wireless device via a second
transmission line, the wireless control device including wireless resource
5 allocation means for allocating a wireless resource used by the wireless
device in wirelessly communicating with the wireless terminal, and
wireless resource instruction means for sending an instruction for allowing
use of the allocated wireless resource to the relay device, wherein the relay
device executes processing to perform wireless communication using the
10 allocated wireless resource, on data to be sent to the wireless terminal, on
the basis of the instruction from the wireless control device, and the
wireless device converts a signal processed by the wireless signal
processing means into a wireless signal and transmits the wireless signal to
the wireless terminal.
15 [0012]
A wireless communication method according to the present
invention includes, in a wireless control device connected via a
transmission line to at least one wireless device which wirelessly
communicates with a wireless terminal, allocating a wireless resource used
20 by the wireless device in wirelessly communicating with the wireless
terminal, sending an instruction for allowing use of the allocated wireless
resource to the wireless device, in the wireless device, executing
processing to perform wireless communication using the allocated wireless
resource, on data to be sent to the wireless terminal, on the basis of the
25 instruction from the wireless control device, and converting a signal
processed by the wireless signal processing means into a wireless signal
and transmitting the wireless signal to the wireless terminal.
Advantageous Effects of Invention
[00 131
6
The present invention can provide a wireless communication system
and a wireless communication method for efficiently performing
communication between a wireless control device and a wireless device.
Brief Description of Drawings
5 [0014]
[Fig. 11 Fig. 1 is a diagram illustrating an overview of a wireless
communication system according to an exemplary embodiment of the
present invention.
[Fig. 21 Fig. 2 is a diagram illustrating a wireless communication system
10 according to a first exemplary embodiment.
[Fig. 31 Fig. 3 is a diagram illustrating an exemplary user-plane protocol
stack in LTE.
[Fig. 41 Fig. 4 is a diagram illustrating how protocol processing functions
are shared between a center node and an access point according to the first
15 exemplary embodiment.
[Fig. 51 Fig. 5 is a block diagram illustrating the configuration of software
running at the center node according to the first exemplary embodiment.
[Fig. 61 Fig. 6 is a block diagram illustrating the configuration of a
wireless signal processing unit according to the first exemplary
20 embodiment.
[Fig. 71 Fig. 7 is a diagram illustrating a wireless communication system
according to a second exemplary embodiment.
[Fig. 81 Fig. 8 is a diagram illustrating how protocol processing functions
are shared among a center node, a relay node, and a second access point
25 according to the second exemplary embodiment.
[Fig. 91 Fig. 9 is a diagram illustrating an exemplary specific configuration
of software running at a center node according to a third exemplary
embodiment.
[Fig. 101 Fig. 10 is a diagram illustrating an exemplary state in which
7
wireless resources are allocated to a plurality of users.
[Fig. 111 Fig. 11 is a diagram illustrating an exemplary frame format.
[Fig. 121 Fig. 12 is a diagram illustrating a plurality of exemplary
subcarriers.
5 [Fig. 131 Fig. 13 is a diagram illustrating an exemplary specific
- -,
configuration of a wireless signal processing unit according to the third
exemplary embodiment.
[Fig. 141 Fig. 14 is a diagram for explaining the downstream HARQ timing.
[Fig. 151 Fig. 15 is a diagram illustrating an exemplary specific
10 configuration of a wireless signal processing unit according to a fourth
exemplary embodiment.
[Fig. 161 Fig. 16 is a diagram illustrating how protocol processing
functions are shared between a center node and an access point according
to a fifth exemplary embodiment.
15 [Fig. 171 Fig. 17 is a diagram illustrating how protocol processing
functions are shared between a center node and an access point according
to a sixth exemplary embodiment.
[Fig. 181 Fig. 18 is a diagram illustrating how protocol processing
functions are shared among a center node, a relay node, and a second
20 access point according to a seventh exemplary embodiment.
[Fig. 191 Fig. 19 is a diagram illustrating how protocol processing
functions are shared between a center node and an access point according^
to an eighth exemplary embodiment.
[Fig. 201 Fig. 20 is a diagram illustrating how protocol processing
25 functions are shared between a center node and an access point according
to a ninth exemplary embodiment.
Description of Embodiments
[00 151
(Overview of Exemplary Embodiment According to Present Invention)
8
Before a description of exemplary embodiments of the present
invention, an overview of an exemplary embodiment according to the
present invention will be described below. Fig. 1 is a diagram
illustrating an overview of a wireless communication system 1 according to
5 an exemplary embodiment of the present invention. The wireless
communication system 1 includes a wireless control device 20 and at least
one wireless device 30, as illustrated in Fig. 1. The wireless device 30 is
connected to the wireless control device 20 via a transmission line 10 and
wirelessly communicates with at least one wireless terminal 2.
10 [0016]
The wireless control device 20 includes a wireless resource
allocation unit 22 (wireless resource allocation means) and a wireless
resource instruction unit 24 (wireless resource instruction means). The
wireless resource allocation unit 22 allocates a wireless resource used by
15 the wireless device 30 in wirelessly communicating with the wireless
terminal 2. The wireless resource instruction unit 24 sends an instruction
for allowing use of the allocated wireless resource to the wireless device
30.
[00 171
20 The wireless device 30 includes a wireless signal processing unit 32
(wireless signal processing means) and a wireless transmission unit 34
(wireless transmission means). The wireless signal processing unit 32
executes processing to perform wireless communication using the allocated
wireless resource, on data to be sent to the wireless terminal 2, on the basis
25 of the instruction from the wireless control device 20. The wireless
transrnissiorl unit 34 corlverts a signal processed by Lhc wirclcss signal
processing unit 32 into a wireless signal and transmits the wireless signal
to the wireless terminal 2.
[OO 181
9
The wireless communication system 1 and the wireless
communication method according to the exemplary embodiment of the
present invention can reduce the volume of data (rate of data) transmitted
through the transmission line 10 between the wireless control device 20
5 and the wireless device 30. This allows efficient communication between
the wireless control device 20 and the wireless device 30. Even by the
wireless control device 20 or the wireless device 30, efficient
communication between the wireless control device 20 and the wireless
device 30 becomes possible. A relay device may be interposed between
10 the wireless control device 20 and the wireless device 30 and include a
wireless signal processing unit 32 on behalf of the wireless device 30 to
allow efficient communication between the wireless control device 20 and
the wireless device 30 (relay device).
[00 1 91
15 (First Exemplary Embodiment)
Exemplary embodiments will be described below with reference to
the drawings. Although the use of LTE will be taken as an example of the
radio scheme in each following exemplary embodiment, the present
invention is not limited to this. These exemplary embodiments are also
20 applicable to an arbitrary radio access scheme and an arbitrary
combination of a plurality of radio access schemes (for example, a
combination of CDMA (Code Division Multiple Access)/HSPA (High
Speed Packet Access)/LTE/LTE-advanced).
[ooao]
25 Fig. 2 is a diagram illustrating a wireless communication system
100 according to a first exemplary embodiment. The wireless
communication system 100 may serve as, for example, a RAN (Radio
Access Network). The wireless communication system 100 includes a
center node 200 and a plurality of access points 300-1 (access point #1)
10
and 300-2 (access point #2). A plurality of wireless terminals 120-1
(wireless terminal #1) and 120-2 (wireless terminal #2) wirelessly
communicate with the wireless communication system 100. In the
following description of a plurality of components such as the access
5 points 300-1 and 300-2 without distinction, they will be simply referred to
as, for example, access points 300 hereinafter. The center node 200
corresponds to a wireless control device. The access point 300
corresponds to a wireless device.
[002 11
10 Although Fig. 2 depicts two access points 300, the present
invention is not limited to this. The number of access points 300 may be
one or three or more. Similarly, although Fig. 2 depicts two wireless
terminals 120, the present invention is not limited to this. The number of
wireless terminals 120 may be one or three or more. The same applies to
15 other exemplary embodiments.
[0022]
The center node 200 is connected to a core network 104 via a
backhaul 102. The center node 200 and the access point 300 are located
at physically spaced positions and connected to each other via a
20 transmission line 110. The wireless terminal 120 serves as a mobile
communication terminal such as a mobile phone or a smartphone. The
wireless terminal 120 transmits/receives wireless signals tolfrom the
access point 300.
[0023]
25 The transmission line 110 serves as a medium for transmitting
information, such as an optical fiber, a metal cable, or radio. Allhough
the transmission line 110 may be compliant with, for example, Ethernet@,
the present invention is not limited to this. The transmission line 110 is
used to transmit user data, and control channelslcontrol signals and the like
11
exchanged between the center node 200 and the access point 300, other
than user data, as will be described later.
[0024]
The center node 200 and the access point 300 are connected to each
5 other via the transmission line 110 formed by one or more media. More
specifically, the transmission line 110 may be formed by only an optical
fiber. Whereas, the transmission line 110 may be formed by an optical
fiber and radio or a metal cable. For example, the transmission line 110
may be formed by routing the center node 200 to the vicinity of the access
10 point 300 by wiring an optical fiber, and routing the remaining several ten
meters via radio or a metal cable, for simplified wiring.
[0025]
Although the transmission line 110 connecting the center node 200
to the access point 300- 1 and the transmission line 11 0 connecting the
15 center node 200 to the access point 300-2 are separate from each other in
FIG. 1, the present invention is not limited to such a configuration.
When the access points 300-1 and 300-2 are adjacent to each other, they
may partially share the transmission line 110. In this case, a distributor
may be placed near the access points 300. Note that the distributor, for
20 example, multiplexes and demultiplexes wavelength-multiplexed signals or
multiplexes and demultiplexes time-multiplexed signals.
[0026]
The center node 200 includes a reference clock generation unit 202,
a general-purpose server 204, and a transmission line interface 206
25 (transmission line IIF (Interface)). The reference clock generation unit
202 generates a reference clock for synchronization processing in the
wireless communication system 100. The reference clock will be
described later.
[0027]
12
The general-purpose server 204 includes one or more computers.
The general-purpose server 204 executes software 21 0. More specifically,
the general-purpose server 204 loads software 210 stored on a recording
medium (not illustrated) into a memory (not illustrated) and executes the
5 software 210 under the control of an arithmetic device (not illustrated)
such as a CPU (Central Processing Unit). In other words, the software
210 runs on the general-purpose server 204. The software 210 will be
described later. The transmission line interface 206 performs processing
according to the standard (for example, Ethernet) of the transmission line
10 110 in exchanging data with the access point 300 via the transmission line
110.
[0028]
The access point 300 includes a transmission line interface 302
(transmission line IIF (Interface)), a wireless signal processing unit 3 10, a
15 wireless transmissionlreception unit 304, and an antenna 306. The
antenna 306 includes a plurality of antennas and may be, for example, an
antenna array including a plurality of antenna elements. The
transmission line interface 302 performs processing according to the
standard (for example, Ethernet) of the transmission line 110 in
20 exchanging data with the center node 200 via the transmission line 110.
The wireless signal processing unit 3 10 and the wireless
transmissionlreception unit 304 will be described later.
[0029]
The wireless Lerrriirial 120 ~urnrnunicatesw ith a radio access
25 network (wireless communication system 100) via one or more access
points 300. When downstream signals (signals from the access poinls
300 to the wireless terminal 120) are transmitted from a plurality of access
points 300 to one wireless terminal 120, each of the plurality of access
points 300 may use mutually different frequencies or the same frequencies.
13
Further, in this case, each of the plurality of access points 300 may
transmit mutually different pieces of data or the same data to one wireless
terminal 120. The information indicating whether the frequencies are the
same and the information indicating whether the data are the same do not
5 correspond to each other. In other words, the same data may be
transmitted using different frequencies or using the same frequencies.
[0030]
Similarly, when one access point 300 simultaneously transmits
downstream signals to a plurality of wireless terminals 120, the access
10 point 300 may transmit downstream signals to the plurality of wireless
terminals 120 using mutually different frequencies or using the same
frequencies. A spatial multiplexing technique such as MU-MIMO
(Multi-User Multiple-Input Multiple-Output) or beam-forming may be
employed as a technique for simultaneously transmitting different pieces
15 of data to the plurality of wireless terminals 120 using the same
frequencies.
[003 11
Specific operations of the center node 200 and the access point 300
will be described below. The center node 200 and the access point 300
20 share and process the functions of a radio base station with each other, as
will be described hereinafter. Although such operations will be described
below mainly assuming the downstream direction (from the center node
200 to the access point 300, and from the access point 300 to the wireless
terminal 120), corresponding operations are obviously also perforined in
25 the upstream direction (from the wireless terminal 120 to the access point
300, and from the access point 300 to the center node 200).
LO0321
Fig. 3 is a diagram illustrating an exemplary user-plane protocol
stack in LTE. Fig. 3 is presented in NPL 4. The user-plane protocol
14
stack is divided into a layer 2 protocol (L2) and a layer 1 (PHY: physical
layer) protocol (Ll), as illustrated in Fig. 3. Layer 2 includes three
sublayers: PDCP (Packet Data Convergence Protocol), RLC (Radio Link
Control), and MAC (Media Access Control). Layers 2 and 1 are
5 connected to each other via a transport channel to transmit MAC-PDU
(Protocol Data Unit) serving as user data.
100331
Layer 2 protocol processing is a function which can be efficiently
implemented by software (general-purpose server). In the present
10 exemplary embodiment, therefore, the layer 2 protocol processing is
implemented by the software 210 running on the general-purpose server
204 of the center node 200. In other words, the general-purpose server
204 (software 210) of the center node 200 mainly performs layer 2
processing of protocol processing on user data directed to each wireless
15 terminal 120.
[0034]
Layer 1 protocol processing is a function hard to efficiently
implement by software (general-purpose server). In the present
exemplary embodiment, therefore, the layer 1 protocol processing is
20 implemented by the wireless signal processing unit 310 of the access point
300. In other words, the wireless signal processing unit 3 10 of the access
point 300 mainly performs layer 1 processing of the protocol processing on
user data directed to each wireless terminal 120.
[UU35]
2 5 Fig. 4 is a diagram illustrating how protocol processing functions
are shared between the center node 200 and the access point 300 according
to the first exemplary embodiment. As described above, an L2
processing function is located at the center node 200 and implemented by
the software 210 running on the general-purpose server 204. An L1
15
processing function is located at the access point 300 and implemented by
the wireless signal processing unit 3 10. MAC-PDU (Transport Block)
serving as user data is transmitted on the transmission line 110 connecting
the center node 200 to the access point 300.
5 [0036]
Fig. 5 is a block diagram illustrating the configuration of the
software 210 running at the center node 200 according to the first
exemplary embodiment. The software 21 0 includes a synchronizing unit
2 12, a radio channel quality management unit 2 14, an access point
10 selection unit 21 6, a wireless resource management unit 21 8, a wireless
resource allocation unit 220, and an access point control unit 222. The
above-mentioned components of the software 210 are merely an example
and are not limited to this.
[0037]
15 The synchronizing unit 2 12 performs synchronization processing
using a reference clock generated by the reference clock generation unit
202. In a radio access network, the radio frequencies need to be
accurately matched in each device. This is called frequency
synchronization. When TDD (Time Division Duplex) is used as a radio
20 scheme, the switching timings of transmission/reception need to be
accurately matched among a plurality of access points 300. This is called
timing synchronization. This timing synchronization is needed in
processing not only at the access point 300 but also at the center node 200.
The synchronizing unit 212 performs processing for sucli Irequency
25 synchronization and timing synchronization. The synchronizing unit 2 12
performs processing to transmit a signal (sync signal) for synchronizing
the access point 300 to the access point 300 via the transmission line
interface 206 and the transmission line 110, using the reference clock.
[0038]
16
The synchronizing unit 212 performs processing to distribute the
reference clock to each access point 300 via the transmission line 110,
using protocols such as Synchronous Ethernet@ and PTP (Precision Time
Protocol) defined in IEEE1588. Synchronous Ethernet is used for
5 frequency synchronization. PTP is used for frequency synchronization
and timing synchronization. The center node 200 may synchronize the
frequencies and timings of each node in the radio access network, using
GNSS (Global Navigation Satellite System) such as GPS (Global
Positioning System) or in combination with the above-mentioned method.
10 [0039]
When FDD (Frequency Division Duplex) is used as a radio scheme,
timing synchronization among the plurality of access points 300 is optional.
However, the timings among the plurality of access points 300 are
preferably synchronized when the plurality of access points 300 perform
15 cooperative operations, as will be described later. The cooperative
operations between the access points may be performed when, for example,
one wireless terminal 120 and the plurality of access points 300
simultaneously perform communication, or the use of the same wireless
resources is avoided to reduce interference between adjacent access points
20 300.
[0040]
The radio channel quality management unit 2 14 manages the radio
channel quality (for example, the propagation loss, the received signal
strength, and the magnitude of noiselinterference) between each wireless
25 terminal 120 and each access point 300. More specifically, the radio
channel quality management unit 214 receives information (radio channel
quality information) concerning the radio channel quality between each
access point 300 and each wireless terminal 120, from this access point 300
via the transmission line 110 and the transmission line interface 206.
17
Each access point 300 may generate radio channel quality information by
receiving information such as a CQI (Channel Quality Indicator) from each
wireless terminal 120.
[0041]
5 The access point selection unit 216 (wireless device selection
means) selects the access point 300 to be wirelessly communicated with the
wireless terminal 120, for each wireless terminal 120. More specifically,
the access point selection unit 216 selects at least one access point 300
corresponding to a best-quality radio channel, using the radio channel
10 quality managed by the radio channel quality management unit 214. The
access point selection unit 216 transmits, to this access point 300, a control
signal for allowing the selected access point 300 to communicate with the
wireless terminal 120 via the transmission line interface 206 and the
transmission line 110. In this manner, the center node 200 communicates
15 with the wireless terminal 120 via a best-quality access point 300. In the
configuration of the present exemplary embodiment, the present invention
is not necessarily limited to such a method.
[0042]
The wireless resource management unit 21 8 manages wireless
20 resources usable at each access point 300. Examples of the wireless
resources include the time slot, the frequency, the transmitted power, and
the space, but the present invention is not limited to these examples.
[0043]
The wireless resource allocation unit 220 scrvcs as, for example, a
25 scheduler and performs processing (scheduling) to allocate wireless
resources to the wireless terminals 120. More specirically, the wireless
resource allocation unit 220 determines with which wireless terminal 120
the center node 200 communicates in using the wireless resources managed
by the wireless resource management unit 218. The wireless resource
18
allocation unit 220 then transmits a wireless resource instruction signal to
the access point 300 via the transmission line interface 206 and the
transmission line 110. The wireless resource instruction signal means
herein an instruction signal indicating, to the access point 300, which
5 wireless resources are used in transmission and reception to and from the
wireless terminal 120 to be communicated, and represents an instruction
for allowing the access point 300 to use the allocated wireless resources.
[0044]
The wireless resource allocation unit 220 performs scheduling to
10 enhance the total throughput while maintaining fairness between the
respective wireless terminals 120. More specifically, the wireless
resource allocation unit 220 determines, for example, the volume of data
(packets) to be sent to each wireless terminal 120, the communication rate
and delay time required in accordance with the type of service (for example,
15 data communication or audio communication), and the transmission state
of each wireless terminal 120. The wireless resource allocation unit 220
allocates wireless resources to each wireless terminal 120 in accordance
with the determination results.
[0045]
20 The access point control unit 222 (wireless device control means)
has the function of monitoring and controlling each access point 300.
The access point control unit 222 transmits a monitoring/controlling signal
for monitoring and controlling the access point 300 to the access point 300
via the transmissivn line interface 206 and the transmission line 110.
25 [0046]
The access point control unit 222 performs processing to cviltrol the
parts constituting the center node 200 and to cause the plurality of access
points 300 to perform cooperative operations. More specifically, the
following processing is performed.
19
[0047]
When the access point 300 with the best radio channel quality is
different between the upstream and downstream channels, the access point
control unit 222 may perform control to use different access points 300 in
5 the upstream and downstream channels. For example, the access point
300-2 (access point #2) may receive an ACKINACK signal indicating
whether the wireless terminal 120 has successfully received downstream
data transmitted from the access point 300-1 (access point #1) to the
wireless terminal 120. In this case, the access point control unit 222 may
10 perform control to select access point #1 via the downstream channel and
select access point #2 via the upstream channel. Thus, the center node
200 (access point control unit 222) can determine whether to transmit new
data or to retransmit old data next.
[0048]
15 When a certain wireless terminal 120 is located near the boundary
between the areas (cells) of a plurality of access points 300 (access points
#I and #2), the access point control unit 222 may control the plurality of
access points 300 to simultaneously transmit the same data using the same
frequencies. Since the data redundancy can thus be increased, the
20 reception quality of the wireless terminal 120 can be improved. In this
case, the access point control unit 222 may perform control to match the
methods for using wireless resources at the plurality of access points 300.
The access point control unit 222 may further perform control to distribute
data from thc ccntcr nodc 200 to each access point 300 (access points #I
25 and #2) to enable the respective access points 300 to transmit the same data
at the same timing.
[0049]
When a certain wireless terminal 120 is located near the boundary
between the areas (cells) of a plurality of access points 300 (access points
20
#1 and #2), the access point control unit 222 may perform control to
transmit data from only an access point 300 with the best radio channel
quality. In this case, the access point control unit 222 may control other
access points 300 to stop using a wireless resource which causes
5 interference. This can improve the reception quality of the wireless
terminal 120.
[0050]
When a certain wireless terminal 120 is located near the boundary
between the areas (cells) of a plurality of access points 300 (access points
10 #1 and #2), the access point control unit 222 may perform control to
simultaneously transmit different data using different frequencies from the
plurality of access points 300. The "different data" mean herein
respective pieces of sub-data obtained by dividing user data. This can
implement carrier aggregation between the access points 300 to improve
15 the throughput of the wireless terminal 120.
[005 1 ]
When a certain wireless terminal 120 is located near the boundary
between the areas (cells) of a plurality of access points 300 (access points
#1 and #2), the access point control unit 222 may perform control to
20 simultaneously transmit different data using the same frequencies from the
plurality of access points 300. This can implement MIMO
communication between the access points 300 to improve the throughput of
the wireless terminal 120.
[0052]
2 5 When the position of the wireless terminal 120 is unclear, one
access point 300 with the best quality may not be determined. The case
where the position of the wireless terminal 120 is unclear means herein the
case where, for example, the moving speed of the wireless terminal 120 is
high, a case where a wireless terminal 120 which has not been used for
2 1
communication for a while newly starts communication, or the like. In
such a case, the access point control unit 222 may perform control to
simultaneously transmit the same data using the same frequencies from the
plurality of access points 300. Since the data redundancy can thus be
5 increased, data can be reliably transmitted to the wireless terminal 120.
[0053]
The software 210 performs at least one process associated with the
layer 2 protocol illustrated in Fig. 3 (processes associated with PDCP, RLC,
and MAC) other than the above-mentioned process. Processes such as the
10 above-mentioned access point selection, wireless resource selection, and
cooperative operations between the access points 300 are too complex to be
processed by hardware. In other words, the above-mentioned processing
is suitable as software processing which uses the general-purpose server
204 equipped with a general-purpose processor. In the present exemplary
15 embodiment, therefore, the above-mentioned processing can be efficiently
performed.
[0054]
Fig. 6 is a block diagram illustrating the configuration of the
wireless signal processing unit 3 10 according to the first exemplary
20 embodiment. The wireless signal processing unit 3 10 includes a channel
encoding unit 312, a modulation unit 314, a physical antenna mapping unit
3 16, a physical antenna synthesis unit 322, a demodulation unit 324, and a
channel decoding unit 326.
[0055]
2 5 The wireless signal processing unit 3 10 performs transmission
processing associated with the layer 1 protocol on downstream user data
(MAC-PDU). The wireless signal processing unit 310 converts the user
data into a baseband signal by transmission processing. The wireless
signal processing unit 3 10 then transmits the baseband signal to the
wireless transmission/reception unit 304. More specifically, the channel
encoding unit 3 12 performs channel encoding processing on the
downstream user data (MAC-PDU) received by the transmission line
interface 302 via the transmission line 11 0. The modulation unit 3 14
5 performs modulation processing on the data having undergone the channel
encoding processing. Note that the modulation unit 3 14 may perform
modulation processing using the OFDM (Orthogonal Frequency Division
Multiplexing) scheme.
[0056]
10 The physical antenna mapping unit 3 16 (antenna weighting means)
performs transmission antenna weighting processing for each antenna of
the antenna 306 including a plurality of antennas, for the data having
undergone the modulation processing. The transmission antenna
weighting processing means herein processing for controlling the
15 amplitude/phase for each of a plurality of antenna elements constituting
the antenna 306.
[0057]
The wireless transmission/reception unit 304 converts the baseband
signal having undergone the transmission antenna weighting processing
20 into a wireless signal. The wireless transmission/reception unit 304
transmits a wireless signal to each wireless terminal 120 via the antenna
306.
[OOS 81
The wireless transmission/reception unit 304 receives an upstream
25 signal (wireless signal) from each wireless terminal 120 via the antenna
306. The wireless transmission/reception unit 304 converts the upstream
signal into a digital baseband signal.
[0059]
The wireless signal processing unit 3 10 performs reception
23
processing associated with the layer 1 protocol on the upstream signal
(baseband signal). The wireless signal processing unit 310 converts the
baseband signal into user data (MAC - PDU) by the reception processing
and transmits the user data to the transmission line interface 302.
5 [0060]
More specifically, the physical antenna synthesis unit 322 performs
reception antenna weighting processing for each antenna of the antenna
306 including a plurality of antennas, for the baseband signal. The
reception antenna weighting processing means herein processing for
10 multiplying an amplitudelphase different for each of a plurality of antenna
elements constituting the antenna 306 and then summing signals received
by all antennas. The demodulation unit 324 performs demodulation
processing on the signal having undergone the reception antenna weighting
processing. Note that the demodulation unit 324 may perform
15 demodulation processing using the OFDM scheme. The channel decoding
unit 326 performs channel decoding processing on the signal having
undergone the demodulation processing. The transmission antenna
weighting processing and the reception antenna weighting processing will
be collectively referred to as antenna weighting processing hereinafter.
20 [0061]
Wireless resources used in transmission and reception to and from
each wireless terminal 120 are used in accordance with an instruction from
the center node 200. In other words, the access point 300 receives a
wireless resource instruction signal from the center node 200. The
25 wireless signal processing unit 3 10 and the wireless transmission/reception
unit 304 perform appropriate processing in accordance will1 the received
wireless resource instruction signal.
[0062]
In the present exemplary embodiment, MAC-PDU (Transport
24
Block) serving as user data is transmitted on the transmission line 110
connecting the center node 200 to the access point 300, as described above.
In contrast to this, in the above-mentioned related-art technique, the device
(for example, the BDE, the REC, and the master device) on the center side
5 performs digital signal processing. Therefore, a baseband signal is
transmitted on a transmission line connecting the device on the center side
to the device on the antenna side. The baseband signal has a data volume
larger than that of MAC-PDU.
COO631
10 In the present exemplary embodiment, not the center node 200 but
the access point 300 performs at least one of antenna synthesis processing
(for example, beam forming and MIMO precoding) such as antenna
weighting processing, modulation/demodulation processing, and channel
encodingldecoding processing that result in an increased data rate, as
15 described above. Therefore, in the wireless communication system 100
according to the present exemplary embodiment, the data rate of the
transmission line 11 0 between the center node 200 and the access point 300
can be reduced.
[0064]
20 Hence, even when the radio bandwidth or the number of antennas
considerably increases, a data rate required in the transmission line
between the center node 200 and the access point 300 can be economically
attained using only a small number of optical fibers. In the
above-mentioned related-art technique, accomnioclatiilg strained mobilc
25 data communication may enormously raise the data rate required in the
transmission line between the wireless control unit (for example, REC) on
the center side and the wireless unit (for example, RE) on the antenna side,
thus hindering economical accommodation using only a small number of
optical fibers.
2 5
[0065]
Methods for considerably increasing the radio capacity of mobile
data communication include a method for using a frequency bandwidth
wider than that in the conventional cases, and a method for using antennas
5 larger in number than the conventional cases to increase the order of
spatial multiplexing (for example, beam forming and multi-user MIMO).
In the above-mentioned related-art technique, however, the data rate in the
transmission line between the wireless control unit (for example, REC) on
the center side and the wireless unit (for example, RE) on the antenna side
10 increases in proportion to the product of the bandwidth and the number of
antennas. For example, the specification of an LTE channel bandwidth of
20 MHz12 antennas (2 x 2 MIMO) that is the current standard configuration
requires a data rate of about 2 Gbps. On the other hand, when the
specification increases to 100 MHz1128 antennas, a data rate of 640 Gbps,
15 that is, 2 Gbps x 320 is required. This data rate considerably falls
outside the range in which it can be economically attained, even when
optical fibers are used.
[0066]
As another method for considerably increasing the radio capacity, a
20 method for increasing the number of antenna sites or the like is available.
In this case, the data rate in the transmission line between the wireless
control unit (for example, REC) on one center side and the wireless unit
(for example, RE) on the antenna side remains the same. However, the
rlurrrbert uS uptical fibers c o ~ i ~ ~ e cttoe tdh e wireless coi~trolu i~il( lor
25 example, REC) on the center side increases in proportion to the number of
antenna sites. Therefore, the total data rate per wireless control unit (for
example, REC) on the center side considerably increases.
[0067]
In the present exemplary embodiment, for the specification of an
26
LTE channel bandwidth of 20 MHz12 antennas (2 x 2 MIMO), the peak
throughput of user data is about 150 Mbps. This data rate is considerably
lower than a bit rate of about 2 Gbps that is required in the
above-mentioned related-art technique that employs CPRI as the standard
5 of a transmission line. Especially when the specification increases to a
wide bandwidth (for example, 100 MHz)/multiple antennas (for example,
128 elements), the bit rate becomes about 640 Gbps, thus hindering
economical signal transmission using only a small number of optical fibers,
as described above, in the above-mentioned related-art technique. In
10 contrast to this, in the present exemplary embodiment, since, as described
above, the bit rate can be considerably reduced, 10-Gbps Ethernet (10
GBASE-SRILR) or 40-Gbps Ethernet (40 GBASE-LR4), for example, can
be employed as the specification of a transmission line. This allows
economic data transmission.
15 [0068]
In the present exemplary embodiment, as described above, since the
bit rate in the transmission line 110 between the center node 200 and the
access point 300 can be lowered, the delay in the transmission line can be
reduced. When LTE is used as a radio scheme, user data is scheduled for
20 each subframe having a period of 1 ms. Accordingly, the delay in the
transmission line needs to be sufficiently shorter than 1 ms. This is
because the radio channel quality varies with time due, for example, to
fading. Therefore, even if the center node 200 schedules (selects) the
best access point and wireless resources, it is highly probable that the
25 selected access point and wireless resources will not always be best at the
time of their actual use because of the sigilificant delay.
[0069]
The delay of the transmission line needs to be short for the
following reason as well. In FDD of LTE, HARQ (Hybrid ARQ) uses the
27
stop and wait scheme in eight processes. In this case, when the cycle of
transmission (downstream), an ACKINACK response (upstream), and
retransmission (downstream) exceeds eight subframes (8 ms), it is no
longer possible to continuously transmit data. Thus, the peak throughput
5 per wireless terminal 120 is lowered. When, for example, the
transmission delay of an optical fiber is about 5 pslkm and the maximum
length of the optical fiber is 20 km, the maximum delay is 100 ps.
Therefore, the delay of the transmission line needs to be short. HARQ
will be described later in other exemplary embodiments.
10 [0070]
In the present exemplary embodiment, as a transmission line
interface between the center node 200 and the access point 300, the
medium having a general-purpose specification (for example, Ethernet) is
usable. A general-purpose server (general-purpose server 204) normally
15 includes an interface such as Ethernet. This obviates the need to add a
special transmission line interface circuit. This can reduce the cost of
transmission lines. Similarly, general-purpose components are usable
even for the access points 300.
[007 11
20 In the above-mentioned related-art technique, CPRI is employed as
the standard of a transmission line. CPRI is a dedicated specification
used only at the interface between the wireless control unit (for example,
REC) on the center side and the wireless unit (for example, RE) on the
antenna side, and is incompatible with a standard interface specification
25 (for example, Ethernet) used for various other purposes. Therefore, in
llie above-rnenlioned related-art technique, the need to develop dedicated
hardwarelsoftware entails higher costs of development, and the
impossibility of sharing such hardwarelsoftware with other systems
increases the costs. For example, since a general-purpose server includes
28
no CPRI interface and therefore cannot be used directly, a dedicated CPRI
interface needs to be added.
[0072]
In the present exemplary embodiment, as a transmission line
5 interface between the center node 200 (for example, REC) and the access
point 300 (for example, RE), the medium having a general-purpose
specification is usable, as described above. The costs of development
can thus be lowered while the costs of components can be cut by sharing.
[0073]
10 In the above-mentioned related-art technique, when processing in
the wireless control unit (for example, REC) on the center side, especially
wireless signal processing (layer 1: physical layer processing), is
performed by a general-purpose processor (general-purpose server), the
processing load becomes very high. This poses a problem such as arising
15 of the need of a very large number of processors or the need to wait until
the processing capacity of the general-purpose processor significantly
improves.
[0074]
Signal processing (for example, Turbo error correction processing,
20 FFTIIFFT processing, and matrix operation processing for MIMO) unique
to mobile wireless signal processing is very large in amount. When the
radio bandwidthlnumber of antennas considerably increases, data having a
volume of 640 Gbps per antenna site needs to be handled, as described
above, and memory and bus bottlenecks occur in the processor. In
25 addition, the mobile wireless signal processing includes arithmetic
operations which are bit arithmetic processing very easy (efficiently
executable) in hardware implementation but are not suitable for a
general-purpose processor (lead to a very poor efficiency of use of a 64-bit
arithmetic device), such as error coding processing, bit interleaving, and
2 9
CRC (Cyclic Redundancy Check). Therefore, when these types of
processing are performed by a general-purpose processor (general-purpose
server), the processing load becomes very high.
[0075]
5 In the present exemplary embodiment, the center node 200 (for
example, REC) can be easily implemented by a general-purpose processor
(general-purpose server 204), as described above. In the present
exemplary embodiment, the center node 200 (for example, REC) performs
processing which can be efficiently performed by a general-purpose
10 processor. On the other hand, the access point 300 (or a relay node
described later) implemented as dedicated hardware performs wireless
signal processing performed poorly (with poor processing efficiency) by
the general-purpose server 204. In this manner, functions are shared
between the center node 200 and the access point 300. Thus, the center
15 node 200 (for example, REC) can be easily implemented by a
general-purpose processor (general-purpose server 204). In addition,
implementing functions by the software 21 0 on the general-purpose server
204 enables not only a reduction in cost but also improvements in
scalability, software portability, and functional flexibility. Details will
20 be described later.
[0076]
Again in the present exemplary embodiment, while enjoying the
above-mentioned advantageous effects in the present exemplary
cmbodimcnt, frcc, close cooperative operations between the access points
25 300 can be performed (that is, limitations can be prevented from imposed
on the cooperative operations), as described above. For exanlple, not
only cooperation schemes currently available in the 3GPP standard, such as
inter-site carrier aggregation, CoMP (Coordinated Multi-Point
Transmission/reception), ICIC (Inter-Cell Interference Coordination), and
3 0
Dual Connectivity, but also cooperation schemes expected to be needed in
the future can be freely realized. This is because the wireless resources
can be totally managed in real time at the center node 200 (the advantages
of the conventional remote radio head techniques can be sustained without
5 any change).
[0077]
(Second Exemplary Embodiment)
A second exemplary embodiment will be described next.
Fig. 7 is a diagram illustrating a wireless communication system
10 150 according to a second exemplary embodiment. The wireless
communication system 150 may serve as, for example, a radio access
network. The wireless communication system 150 includes a center node
200, one or more access points 300, one or more relay nodes 400 (relay
devices), and second access points 500-1 (second access point #1) and
15 500-2 (second access point #2). A plurality of wireless terminals 120-1
(wireless terminal #1) and 120-2 (wireless terminal #2) wirelessly
communicate with the wireless communication system 150. The same
reference numerals denote components which are almost the same as those
in the above-described exemplary embodiment, and a description thereof
20 will not be given (the same applies hereinafter).
[0078]
The relay node 400 is interposed between the center node 200 and
the second access point 500. The relay node 400 i s located at a position
physically distanced from the center node 200 and the second access point
25 500. The relay node 400 is connected to the center node 200 via a
transmission line 110. The relay node 400 is further connected to the
second access point 500 via a transmission line 112.
[0079]
Although Fig. 7 depicts two second access points 500, the present
3 1
invention is not limited to this. One or three or more second access
points 500 may be used. Similarly, although Fig. 7 depicts one relay
node 400, the present invention is not limited to this. Two or more relay
nodes 400 may be used. The same applies to other exemplary
5 embodiments.
[OOSO]
The wireless terminal 120 exchanges wireless signals with the
access point 300 and the second access point 500. How to use the
frequencies in the access point 300 and the second access point 500, how to
10 transmit data, how to use the frequencies among the plurality of wireless
terminals 120, and the like are the same as those in the first exemplary
embodiment.
[OOS 11
The relay node 400 includes a transmission line interface 402, a
15 wireless signal processing unit 410, and a transmission line interface 404.
The second access point 500 includes a transmission line interface 502, a
wireless transmission/reception unit 504, and an antenna 506. In other
words, in the second exemplary embodiment, the second access point 500
includes no wireless signal processing unit. Instead, the relay node 400
20 includes a wireless signal processing unit 410.
[0082]
The function of the second access point 500 may be the same as that
of the remote radio equipment (RRE) or the radio equipment (RE)
described in the above-mentioned non-patent literatures. Note, however,
25 that the bandwidthlnumber of antennas and the like applied to the second
access point 500 are not always be the same as those of the remote radio
equipment (RRE) or the radio equipment (RE). When the
bandwidthlnumber of antennas are very large, the function of the wireless
signal processing unit 410 located at the relay node 400 may be partially
32
implemented by the second access point 500.
[0083]
The transmission line interface 402 of the relay node 400 has the
same function as that of the transmission line interface 302 according to
5 the first exemplary embodiment. The wireless signal processing unit 41 0
has the same function as that of the wireless signal processing unit 310
according to the first exemplary embodiment. In other words, the relay
node 400 executes the function of the wireless signal processing unit 3 10
located at the access point 300, in place of the second access point 500.
10 The transmission line interface 404 performs processing according to the
standard of the transmission line 112 in exchanging signals (data) with the
second access point 500 via the transmission line 112.
[0084]
Wireless resources used in transmission and reception to and from
15 each wireless terminal 120 are used in accordance with an instruction from
the center node 200. In other words, the center node 200 transmits a
wireless resource instruction signal to the relay node 400. The relay node
400 receives the wireless resource instruction signal from the center node
200. The wireless signal processing unit 410 performs appropriate
20 processing to enable the second access point 500 to transmit and receive
signals, in accordance with the received wireless resource instruction
signal.
[OOS5]
The transmission line 11 2 serves as a medium for transmitting
25 information, such as an optical fiber, a metal cable, or radio. As
described above, the function of the second access point 500 is the same as
that of the remote radio equipment (RRE) or the radio equipment (RE)
described in the non-patent literatures. Therefore, the transmission line
112 may be compliant with, for example, CPRI to connect the second
3 3
access point 500 to the relay node 400. However, the transmission line
112 may not be compliant with, for example, CPRI. When, for example,
the function of the wireless signal processing unit 410 of the relay node
400 is partially implemented by the second access point 500 (for example,
5 the case illustrated in Fig. 18 (to be described later)), the transmission line
112 may be compliant with Ethernet.
[0086]
The transmission line interface 502 of the second access point 500
performs processing according to the standard of the transmission line 112
10 in exchanging signals (data) with the relay node 400 via the transmission
line 112. The wireless transmission/reception unit 504 has the same
function as that of the wireless transmission/reception unit 304 according
to the first exemplary embodiment. In other words, the wireless
transmission/reception unit 504 converts a digital signal (baseband signal)
15 into a wireless signal (RF) and converts a wireless signal into a digital
signal (baseband signal). The antenna 506 includes a plurality of
antennas and may be implemented in, for example, an antenna array
including a plurality of antenna elements, like the antenna 306 according
to the first exemplary embodiment.
20 [0087]
The operation of the center node 200 is the same as that of the
center node 200 according to the first exemplary embodiment. Note that
the center node 200 performs the above-mentioned processing without
distinction between the access point 300 directly connected to the center
25 node 200 and the second access point 500 connected to the center node 200
via the relay node 400. In other words, the center node 200 can perform
cooperative operations without distinction, even between access points
having different functions, including the access point 300 equipped with
the wireless signal processing unit 310 and the second access point 500
3 4
equipped with no wireless signal processing unit.
[OOSS]
The wireless terminal 120 communicates with a radio access
network (wireless communication system 150) via one or more access
5 points (access point 300 and second access points 500-1 and 500-2). The
operation of the wireless terminal 120 is the same as that of the wireless
terminal 120 according to the first exemplary embodiment. Note that the
wireless terminal 120 performs communication without distinction with the
access point 300 directly connected to the center node 200 and the second
10 access point 500 connected to the center node 200 via the relay node 400.
In other words, the wireless terminal 120 can communicate, without
distinction, with access points having different functions, including the
access point 300 equipped with the wireless signal processing unit 3 10 and
the second access point 500 equipped with no wireless signal processing
15 unit.
[0089]
In the second exemplary embodiment, some or all of the functions
of the wireless signal processing unit 3 10 located at the access point 300
are separated and located at the relay node 400, as described above. This
20 can increase the degrees of freedom of the positions to locate devices, the
data rates of transmission lines, the sharing of processing resources, and
the like. The relay node 400 may be located near the center node 200 or
near the second access point 500 in accordance with, for example, use
purposes.
25 [0090]
The relay node 400 is located near the cenler node 200 to offer the
following advantage: even when the function of the center node is changed
from the function of the radio base station digital processing equipment
(BDE) or the wireless control unit (REC) in the above-mentioned
3 5
related-art technique to function of the center node 200 according to the
present exemplary embodiment, the remote radio equipment (RRE) or the
radio equipment (RE) in the above-mentioned related-art technique can be
continuously used without any change. In this case, although the effect
5 of lowering the bit rate in the transmission line 112 lessens, the bit rate in
the transmission line 112 need not be lowered any more as long as the
existing transmission line poses no problems related to the bit rate.
[0091]
The relay node 400 is located near the plurality of second access
10 points 500-1 and 500-2 to offer the following advantage: the transmission
line (transmission line 11 0) between the center node 200 and the second
access point 500 can be shared between the plurality of second access
points 500-1 and 500-2. This may obviate the need to separately provide
a transmission line, thus reducing the costs. In the transmission line 112
15 between the relay node 400 and the second access point 500, a baseband
signal (IQ sample) having a large data volume is transmitted. Therefore,
the transmission line 112 requires a high bit rate. However, when the
relay node 400 is located near the second access point 500 (for example,
both devices are located on the same floor of one building or in an
20 underground mall passageway), the cost of the transmission line 112 has
less impact.
[0092]
Fig. 8 is a diagram illustrating how protocol processing functions
are shared among the center node 200, the relay node 400, and the second
25 access point 500. As in the first exemplary embodiment, an L2
processing function is located at the center node 200 and inlpleilleilted by
the software 210 running on the general-purpose server 204. An L1
processing function is located at the relay node 400 and implemented by
the wireless signal processing unit 410. Further, MAC-PDU (Transport
36
Block) serving as user data is transmitted on the transmission line 110
connecting the center node 200 to the relay node 400. An
antenna-specific IQ sample (digital baseband signal) is transmitted on the
transmission line 112 connecting the relay node 400 to the second access
5 point 500.
[0093]
The transmission line 11 0 between the center node 200 and the
relay node 400 is compliant with, for example, Ethernet, as described
above. The transmission line 112 between the relay node 400 and the
10 second access point 500 is compliant with, for example, CPRI. In this
case, the remote radio equipment (RRE) or the radio equipment (RE)
described in the non-patent literatures, for example, is usable as the second
access point 500.
[0094]
15 (Third Exemplary Embodiment)
A third exemplary embodiment will be described next. The third
exemplary embodiment exemplifies a specific configuration of each device
according to the above-mentioned exemplary embodiment when LTE is
employed as a radio scheme.
20 Fig. 9 is a diagram illustrating an exemplary specific configuration
of software 210 running at a center node 200 according to the third
exemplary embodiment. The configuration illustrated in Fig. 9 is the
configuration of the layer 2 protocol (downstream link) described in NPL 4.
The layer 2 protocol iilcludes no signal processilig (for cxuniple, laycr 1
25 protocol processing) unique to radio. Therefore, the layer 2 protocol
processing described in NPL 4 can be implemented by the software 210
running on a general-purpose server 204 of the center node 200. The
software 210 allocates wireless resources to each user (wireless terminal
120), as illustrated in Fig. 10 (to be described later), by the processing
illustrated in Fig. 9.
[0095]
The software 210 includes a PDCP processing unit 240, an RLC
processing unit 250, and a MAC processing unit 260, as illustrated in Fig.
5 9. The PDCP processing unit 240 performs processing associated with a
PDCP sublayer. The PDCP sublayer includes herein the "ROHC (Robust
Header Compression)" and "Security" functions. In other words, the
PDCP processing unit 240 executes the "ROHC" and "Security" functions.
The RLC processing unit 250 performs processing associated with an RLC
10 sublayer. The RLC sublayer includes herein, for example, the
"Segmentation" and "ARQ (Automatic Repeat Request)" functions. In
other words, the RLC processing unit 250 executes, for example, the
"Segmentation" and "ARQ (Automatic Repeat Request)" functions. The
MAC processing unit 260 performs processing associated with a MAC
15 sublayer. The MAC sublayer includes herein, for example, the
scheduling function ("Unicast Scheduling/Priority Handling" and "MBMS
(Multimedia Broadcast and Multicast Service)" functions), the multiple
division function ("Multiplexing" function) executed when a plurality of
logical channels are used for one wireless terminal 120 (UE), and the
20 "HARQ (Hybrid Automatic Repeat Request) function. In other words, the
MAC processing unit 260 executes, for example, the scheduling, multiple
division, and "HARQ" functions.
[0096]
The MAC scheduling function is the function of determining which
25 wireless resources are used for which wireless terminals, with the subframe
(1 ms) period to enhance the efficiency of use of wireless resources in
consideration of the level of priority and the fairness between users. In
the present exemplary embodiment, the MAC scheduling function is
implemented by the general-purpose server 204 (software 210) of the
3 8
center node 200. In other words, the center node 200 collectively
allocates wireless resources to a plurality of access points (access points
300 or second access points 500). A plurality of hierarchical levels may
be defined for each cell, each access point, inter-access point adjustment,
5 and the like and distributed scheduling may be performed for each level to
allow distributed processing by a plurality of processors.
[0097]
As described above, processing associated with the layer 2 protocol
is implemented by the software 210 running on the general-purpose server
10 204. When processing is too much to be performed using only one
general-purpose server equipped with one or more general-purpose CPUs,
processing associated with the layer 2 protocol may be implemented by the
general-purpose server 204 formed by a group of general-purpose servers
including a plurality of servers. The number of access points 300
15 connected to one center node 200 is not particularly fixed, and the number
of access points 300 increases with an increase in traffic. Hence, with an
increase in number of access points 300, the general-purpose server 204
may be desirably scaled up. Thus, in the present exemplary embodiment,
the number and processing capacity of servers constituting the
20 general-purpose server 204 of the center node 200 can be easily changed.
In other words, the center node 200 according to the present exemplary
embodiment has scalability. Further, in the present exemplary
embodiment, it is easily possible not only to increase the number of servers
constitutirlg the general-purpose server 204 bul alsu to replace thc csisting
25 server with a server having a high processing capacity. In other words,
the center node 200 according to the present exemplary elnbodiiiient has
portability.
[0098]
Individual servers constituting the general-purpose server 204 are
3 9
connected to each other via a network within the center node 200 such as
Ethernet and exhibit a given processing capacity as a whole. The
software 2 10 running on the center node 200 may be allocated to each
physical server or CPU in advance or allocated with dynamic changes in
5 accordance with the traffic. The software 210 can run on a more flexible
processing resource by activating it on a virtual machine virtualized by a
hypervisor.
[0099]
Fig. 10 is a diagram illustrating an exemplary state in which
10 wireless resources are allocated to a plurality of users. Fig. 10 illustrates
an exemplary case where wireless resources (time slot, frequency, and
space) associated with each access point 300 are allocated to a plurality of
users (wireless terminals 120). With the above-mentioned processing of
the software 210, wireless resources are allocated to each user (wireless
15 terminal 120), as illustrated in Fig. 10. Further, wireless resources are
defined by three dimensions: the time slot (subframe), the frequency
(subcarrier), and the space (layer), as illustrated in Fig. 10.
[O 1001
The time slot (subframe) will be described hereinafter.
20 Fig. 11 is a diagram illustrating an exemplary frame format. The
exemplary frame format illustrated in Fig. 11 is employed in LTE. The
length of one radio frame is 10 ms (milliseconds). One radio frame
includes 10 subframes each having a length of 1 ms. The subframe
includes two slots (time slots) each having a length of 0.5 ms. In other
25 words, one radio frame includes 20 slots (#0 to #19). One slot includes
seven OFDM symbols (#0 to #6). One OFDM symbol is formed by adding
a CP (Cyclic Prefix) to effective data. The "slot" is defined as the
minimum unit (corresponding to a resource element (to be described later))
of the allocated wireless resource.
40
[OlOl]
The subcarrier will be described next.
Fig. 12 is a diagram illustrating a plurality of exemplary subcarriers.
LTE uses the OFDM scheme of a plurality of subcarriers, as an example
5 illustrated in Fig. 12. In the example illustrated in Fig. 12, when the
bandwidth is 18 MHz and the interval of subcarriers is 15 kHz, this
bandwidth includes 1,200 subcarriers (because of the use of no center
subcarrier).
[O 1021
10 When the access point 300 includes a plurality of antennas (a
plurality of antenna elements constituting an antenna 306), the "space"
(layer) is also usable as one of wireless resources, using a technique such
as beam forming and MIMO. The "space" that is one of wireless
resources may be allocated to either one user (wireless terminal 120) or a
15 plurality of users (wireless terminals 120), using the SU-MIMO (Single
User MIMO) technique, within the range defined by the number of
reception antennas of the wireless terminal 120.
[0 1031
In the example illustrated in Fig. 10, in a first subframe (length: 1
20 ms), user 1 (wireless terminal 120-1) is allocated with two layers (layers 1
and 2). Similarly, in the first subframe, user 2 (wireless terminal 120-2)
is allocated with two layers (layers 1 and 2). In the first subframe, user 3
(wireless terminal 120-3) is allocated with one layer (layer 3). In the
l'illsl subl'rar~le, user 4 (wireless ter~nillal 120-4) is allvcutcd with one laycr
25 (layer 4). In the first subframe, user 5 (wireless terminal 120-5) is
allocated with two layers (layers 3 and 4).
[0 1 041
Although layer 1 (and layer 2) is allocated to both users 1 and 2,
users 1 and 2 are allocated with different frequencies (different
4 1
subcarriers) to separate wireless resources to be allocated between users 1
and 2. Similarly, although layer 3 is allocated to both users 3 and 5,
users 3 and 5 are allocated with different frequencies (different
subcarriers) to separate wireless resources to be allocated between users 3
5 and 5. The same applies to layer 4. Hence, the spatial multiplicity is 4.
[0 1051
Generally, each access point'300 has degrees of freedom of the
"space" (layer) equal in number to antennas (the number of antenna
elements constituting the antenna 306), and spatial multiplexing at this
10 number of degrees of freedom or less can be performed. However, the
spatial multiplexing order usable in practice varies depending on the
strength of channel correlation with the reception antenna of each wireless
terminal 120, the reception level and the noiselinterference level in this
wireless terminal 120, and the like.
15 [0106]
Fig. 13 is a diagram illustrating an exemplary specific
configuration of a wireless signal processing unit 3 10 according to the
third exemplary embodiment. A wireless signal processing unit 410
(second exemplary embodiment) may have the same configuration.
20 Although Fig. 13 illustrates downstream transmission processing of
processing associated with the layer 1 protocol (physical layer), the
wireless signal processing unit 3 10 may perform upstream reception
processing using a corresponding configuration.
[0107]
25 The wireless signal processing unit 3 10 includes user processing
units 342-1 to 342-N (N: an integer of 1 or more), a control channellsignal
processing unit 344, a resource element mapping unit 352, an OFDM
symbol generation unit 354, and a physical antenna mapping unit 356, as
illustrated in Fig. 13. The user processing units 342-1 to 342-N perform
42
processing associated with a plurality of users (wireless terminals 120),
respectively. In other words, the user processing units 342-1 to 342-N
perform processing associated with users 1 to N (wireless terminals 120-1
to 120-N), respectively. The control channellsignal processing unit 344
5 performs processing associated with control channels and control signals
common for each cell.
[0 1081
The resource element mapping unit 352 and the OFDM symbol
generation unit 354 perform processing for collectively converting the
10 processing result for each of a plurality of users and the processing results
of control channels/signals into signals to be transmitted using each logical
antenna port. The physical antenna mapping unit 356 performs
processing for converting the signal for each logical antenna port into a
signal to be transmitted via an actual physical antenna (antenna 306) and
15 mapping it to each physical antenna. Details will be described below.
[0109]
The user processing unit 342 and the control channellsignal
processing unit 344 include a channel encoding unit 362, a modulation
mapping unit 364, a layer mapping unit 366, and a precoding unit 368.
20 The channel encoding unit 362 performs channel encoding for input data
(MAC-PDU; Transport Block) from the layer 2 processing function
(general-purpose server 204; software 210). Examples of channel
encoding include addition of a CRC (Cyclic Redundancy Check), error
correction encoding, interleaving, and rate matching, but the present
25 invention is not limited to these examples.
[Ol l o ]
The modulation mapping unit 364 maps encoded data (codewords)
encoded by the channel encoding unit 362 to signal points (constellation
points) according to the modulation scheme. Thus, the modulation
43
mapping unit 364 generates a modulation signal. Examples of the
modulation scheme include BPSK (Binary Phase Shift Keying), QPSK
(Quadrature Phase Shift Keying), 16-QAM (Quadrature Amplitude
Modulation), and 64-QAM, but the present invention is not limited to these
5 examples.
[ O l l l ]
The layer mapping unit 366 maps modulation signals generated by
the modulation mapping unit 364 to a plurality of layers (the "spaces
(layers)" illustrated in Fig. 10). The "plurality of layers" are used when,
10 for example, the information rate is improved by spatial multiplexing as in,
for example, MIMO (Multi-Input Multi-Output), or the error rate is
reduced by transmission using a plurality of antennas as in transmission
diversity. The center node 200 (software 210) determines which layers
are to be allocated to which users (wireless terminals 120). In other
15 words, the layer mapping unit 366 performs mapping processing in
accordance with an instruction (for example, a wireless resource
instruction signal) sent from the center node 200. The precoding unit 368
precodes the modulation signals mapped to the plurality of layers and
outputs a signal for each logical antenna port.
20 [0112]
Resource element mapping units 352 equal in number to logical
antenna ports are provided. The resource element mapping unit 352 maps
to the RE (Resource Element), the logical antenna port outputs of the user
processing units 342 associated with a plurality of uscrs and the logical
25 antenna port output of the control channel/signal processing unit 344,
obtained using the same logical antenna port. The resuurce elelllent (RE)
uses one subcarrier (frequency) and one symbol (time) as one unit.
[0113]
The resource element (RE) is defined using the subcarrier
44
illustrated in Fig. 12 as one unit in the frequency direction and the symbol
illustrated in Fig. 11 as one unit in the time direction. The resource
elements are allocated to each user (wireless terminal 120) and control
channelslsignals. The resource element mapping unit 352 maps to each
5 allocated resource element, the logical antenna port output of the user
processing unit 342 associated with each corresponding user (wireless
terminal 120) and the logical antenna port output of the control
channellsignal processing unit 344. In other words, the resource element
mapping unit 352 performs resource element mapping processing for each
10 logical antenna port.
[0114]
"0" is mapped to an unallocated (unused) resource element (RE).
Generally, when the same resource element (RE) is used for a plurality of
users (wireless terminals 120) and control channels/signals (that is, spatial
15 multiplexing is performed), different logical antenna ports are used. In
other words, the same resource element (RE) is not shared between a
plurality of users (wireless terminals 120) and control channelslsignals, for
one logical antenna port. Each resource element mapping unit 352
illustrated in Fig. 13 does not map the same resource element to a plurality
20 of users (wireless terminals 120) and control channeldsignals.
[0115]
The output of the resource element mapping unit 352 represents a
subcarrier, that is, a digital baseband waveform of a frequency region.
The OFDM syillbol generation unit 354 uses IFFT (Inverse Fast Fourier
25 Transform) or a circuit configuration equivalent to it to convert a digital
baseband waveform of a frequency region into a digital baseband waveform
of a time region. The OFDM symbol generation unit 354 then adds a
cyclic prefix (CP) and outputs a continuous time waveform. OFDM
symbol generation units 354 equal in number to logical antenna ports are
provided.
[0116]
The physical antenna mapping unit 356 associates logical antenna
ports with physical antenna elements (antenna 306). This association is
5 closely related to antenna directivity control and spatial multiplexing.
Assume, for example, that the number of antenna elements constituting the
antenna 306 of the access point 300 is 128, and the number of reception
antennas of the wireless terminal 120 is 2. Then, since spatial
multiplexing can be performed up to a maximum of 2 x 2 MIMO for each
10 user (wireless terminal 120), one or two logical antenna ports are provided
for each user.
[0117]
The physical antenna mapping unit 356 multiplies the signal from
each logical antenna port by an antenna weighting factor, sums the
15 obtained signals, and outputs the result from each physical antenna (each
antenna element constituting the antenna 306). When the antenna port is
different between users (wireless terminals 120), the physical antenna
mapping unit 356 selects an antenna weighting factor to adjust the
directivity to a user (wireless terminal 120) targeted for transmission.
20 An antenna beam is thus formed for each user (wireless terminal 120).
As in antenna ports to which control channelslsignals are transmitted, for
antenna ports to which signals need to be transmitted in all directions
within the cell, the physical antenna mapping unit 356 selects an antenna
weighting factor which for~lisa directivity wide enough to cover the entire
25 cell. The same applies to antenna ports intended for users (wireless
terminals 120) that are not to undergo beam forming. 111 Lliis case, the
users (wireless terminals 120) may be identified using different resource
elements (REs).
[0118]
46
The wireless transmission/reception unit 304 converts the output of
the physical antenna mapping unit 356 into a wireless signal for each
physical antenna (physical antenna port). The wireless
transmission/reception unit 304 amplifies and filters the signal as
5 appropriate, and the like. The wireless transmission/reception unit 304
transmits a wireless signal from each antenna element constituting the
antenna 306.
[0119]
Since upstream reception processing is symmetrical about
10 transmission processing, a detailed description thereof will not be given.
Reception signals are influenced by, for example, wireless channel
variations such as noise, interference, and fading and are more likely to be
erroneously received. Therefore, to reduce the reception error rate of
upstream data, a plurality of access points 300 receive the same data and
15 the center node 200 (software 210) performs processing for selecting and
synthesizing reception data received by the plurality of access points 300.
When the output of a channel decoding unit 326 of each access point 300 is
hard decision output, correct data is selected by a CRC in the selection and
synthesis processing at the center node 200. When the output of the
20 channel decoding unit 326 of each access point 300 is soft decision output,
decoding results obtained by the plurality of access points 300 are
synthesized to perform final determination in the selection and synthesis
processing at the center node 200. Thus, even when CRCs at all access
points 300 are wrong, correct reception data may be obltlined.
25 [0120]
The downstream HARQ timing will be described hereinafter.
Fig. 14 is a diagram for explaining the downstream HARQ timing.
In FDD of LTE, an eighth-order stop and wait HARQ scheme is employed,
as described above. When retransmission or new data transmission is
47
determined at an interval of eight subframes, downstream transmission
directed to the same wireless terminal 120 can be continuously performed
to attain a peak rate needed by the wireless terminal 120. As illustrated
in Fig. 14, the wireless terminal 120 needs to send an ACKINACK response
5 to the base station side (center node 200 and access point 300) four
subframes after downstream reception. On the other hand, the base
station side (center node 200 and access point 300) can transmit
retransmission data four subframes after NACK reception. Note,
however, that on the base station side, the data in question is not
10 necessarily determined to be retransmitted exactly after four subframes and
may be freely scheduled to be retransmitted later than four subframes.
For example, the base station side may allocate wireless resources to other
wireless terminals 120 to maintain fairness to the other wireless terminals
120, or scheduling may be performed later than four subframes when the
15 processing time on the base station side is missed.
[0121]
Referring to Fig. 14, on the base station side (access point 300 and
center node 200), the access point 300 performs upstream data
demodulation processing and channel decoding processing including
20 ACKINACK. The center node 200 performs scheduling processing of a
final method for using wireless resources, including determination as to
whether retransmission or new data transmission is to be performed. The
access point 300 performs encoding processing and modulation processing,
converts data into a wireless signal, and transmits it, in accordance with
25 the finally determined transmission data (retransmission/new data) and
method for using wireless resources.
[O 1221
In LTE, since the frame format illustrated in Fig. 11 is employed,
encoding processing needs to be performed on data having the subframe
4 8
length and ended before the start of modulation processing on OFDM
symbols including relevant data. Modulation processing needs to be
performed on data having the OFDM symbol length and ended before the
start of physical antenna mapping processing of IQ samples including
5 relevant data. The physical antenna mapping processing is processing for
each IQ sample, which needs to be ended before a relevant IQ sample is
output to the wireless transmission/reception unit 304. In this manner, in
LTE, in response to the need to shorten the delay, the delay can be reduced,
as described above, in the present exemplary embodiment so that the
10 above-mentioned HARQ processing can be performed at an appropriate
timing.
[0 1231
(Fourth Exemplary Embodiment)
Fig. 15 is a diagram illustrating an exemplary specific
15. configuration of a wireless signal processing unit 3 10 according to a fourth
exemplary embodiment. A wireless signal processing unit 41 0 (second
exemplary embodiment) may have the same configuration. Although Fig.
15 illustrates downstream transmission processing of processing associated
with the layer 1 protocol (physical layer), the wireless signal processing
20 unit 3 10 may perform upstream reception processing using a corresponding
configuration, as in Fig. 13.
[0 1241
The wireless signal processing unit 3 10 includes user processing
units 342-1 to 342-N, a control channellsignal processing unit 344, a
25 resource element mapping unit 372, and an OFDM symbol generation unit
374, as illustrated in Fig. 15. The user processing unit 342 and the
control channellsignal processing unit 344 include a channel encoding unit
362, a modulation mapping unit 364, a layer mapping unit 366, a precoding
unit 368, a physical antenna mapping unit 376, and a beam forming unit
378.
[0 1251
The physical antenna mapping unit 376 maps signals precoded by
the precoding unit 368 to physical antennas (antenna elements constituting
5 an antenna 306) by the same processing as in the physical antenna mapping
unit 356. The beam forming unit 378 performs processing associated
with beam forming, on the signals mapped to the physical antennas. The
precoding unit 368, the physical antenna mapping unit 376, and the beam
forming unit 378 are integrated by, for example, their implementation in a
10 common circuit. In other words, precoding processing, processing for
mapping to physical antennas, and beam forming processing are
collectively performed.
[0 1261
The difference between the fourth exemplary embodiment and the
15 third exemplary embodiment (Fig. 13) lies in that in the former, precoding
and beam forming are collectively performed for each physical antenna
port without going through a logical antenna port. Both precoding and
beam forming are processing for multiplication by an antenna-specific
weighting factor. Therefore, precoding and beam forming can be
20 implemented in a common circuit. In other words, since a signal output
from the layer mapping unit 366 is a signal of a frequency region, it is also
possible to regard this processing as multiplication by a beam forming
coefficient in the frequency region.
[0 1271
25 Resource element mapping units 372 equal in number to physical
antenna ports are provided. The resource element mapping unit 372
performs the same processing as in the resource element mapping unit 352
to map to the resource element (RE), the physical antenna port outputs of
the user processing units 342 associated with a plurality of users and the
5 0
physical antenna port output of the control channellsignal processing unit
344, obtained using the same physical antenna port.
[0 1281
The output of the resource element mapping unit 372 represents a
5 subcarrier, that is, a digital baseband waveform of a frequency region.
The OFDM symbol generation unit 374 uses IFFT (or a circuit equivalent
to it) to convert a digital baseband waveform of a frequency region into a
digital baseband waveform of a time region. The OFDM symbol
generation unit 374 then adds a cyclic prefix (CP) and outputs a continuous
10 time waveform. OFDM symbol generation units 374 equal in number to
physical antenna ports are provided.
[0 1291
The numbers of resource element mapping units 352 and OFDM
symbol generation units 354 according to the third exemplary embodiment
15 are equal to the number of logical antenna ports, as described above. The
numbers of resource element mapping units 372 and OFDM symbol
generation units 374 according to the fourth exemplary embodiment are
equal to the number of physical antenna ports. Therefore, when the
number of logical antenna ports is larger than the number of physical
20 antenna ports, the required numbers of resource element mapping units and
OFDM symbol generation units can be made smaller in the fourth
exemplary embodiment than in the third exemplary embodiment. When
spatial multiplexing is performed for a plurality of users (wireless
tcrminals 120) by bcam forming or MU-MIMO, this condition is often
25 satisfied because respective users are mapped to different (logical) antenna
ports.
[0130]
(Other Exemplary Embodiments)
The following exemplary embodiments provide examples different
5 1
from the above-described exemplary embodiments in terms of function
sharing of layer 2 processing and layer 1 processing between a center node
200 and an access point 300. Wireless resource management functions
(for example, a wireless resource management unit 21 8 and a wireless
5 resource allocation unit 220) and functions (for example, a radio channel
quality management unit 214 and an access point selection unit 216) for
selecting an access point 300 to perform transmission and reception to and
from a wireless terminal 120 are always located at the center node 200. A
wireless transmission/reception unit 304 (and a wireless
10 transmission/reception unit 504) and an antenna 306 (and an antenna 506)
are always located at the access point 300 (and the second access point
500). Accordingly, a description of these components will be omitted in
the following exemplary embodiments as appropriate. A description of a
wireless resource instruction signal transmitted from the center node 200
15 to the access point 300 (second access point 500) will also be omitted as
appropriate.
[0131]
(Fifth Exemplary Embodiment)
Fig. 16 is a diagram illustrating how protocol processing functions
20 are shared between a center node 200 and an access point 300 according to
a fifth exemplary embodiment. In the fifth exemplary embodiment, an
HARQ buffer 380 is located at the access point 300, as illustrated in Fig.
16. The HARQ buffer 380 stores transmission data (Transport Block)
transmitted from the center node 200. With such a configuration, when
25 retransmission is required in the HARQ, the center node 200 need only
transmit a pointer indicating which data (Transport Block) is to be
retransmitted. Upon receiving the pointer from the center node 200, the
access point 300 can retransmit the data indicated by the pointer of the
transmission data stored in the HARQ buffer 380. Therefore, when
5 2
retransmission is required in the HARQ, it is unnecessary to transmit
retransmission data from the center node 200 to the access point 300 again.
[0 1321
(Sixth Exemplary Embodiment)
5 Fig. 17 is a diagram illustrating how protocol processing functions
are shared between a center node 200 and an access point 300 according to
a sixth exemplary embodiment. As illustrated in Fig. 17, in the sixth
exemplary embodiment, not only an L2 processing function but also a
channel encoding processing functionlchannel decoding processing
10 function of an L1 processing function and a symbol division function are
located at the center node 200. A modulation/demodulation processing
function of the L1 processing function is located at the access point 300.
[0133]
The center node 200 uses the channel encoding processing function
15 to perform channel encoding of transmission data (downstream data) for all
channels (all users) corresponding to one subframe. The center node 200
then uses the symbol division function to divide all encoded data
(Codewords) for each symbol that is the unit of modulation processing.
The center node 200 sequentially transmits the encoded data divided for
20 each symbol to the access point 300 to complete transmission of all
necessary data before the start of modulation processing of each symbol.
The access point 300 performs modulation processing, precoding/beam
forming, and OFDM symbol generation processing for each symbol, on the
encoded data received from the center node 200.
25 [0134]
Compared to transmission of MAC - PDU for each subframe,
encoded data divided for each symbol can be transmitted with a smaller
unit. In the sixth exemplary embodiment, therefore, the time taken for
data transmission of one unit can be shortened. The time to wait until the
5 3
completion of transmission at the access point 300 can, in turn, be
shortened to enhance the operation ratio of the circuit that executes the L1
processing function.
[0135]
5 Although function division may be similarly performed for
upstream reception data processing, the effect is different from that in the
above-mentioned case of downstream transmission. In upstream
reception, the output of demodulation processing represents likelihood
information including the reliability of data discrimination and is
10 represented by a plurality of bits (for example, six bits) for 1-bit
transmission data. The upstream transmission rate rises. On the other
hand, the center node 200 can perform channel decoding processing
(especially error correction processing) by synthesizing signals received
by a plurality of access points 300 by weighted summation. The
15 reception characteristics can thus be improved.
[0136]
As described above, applying the configuration according to the
sixth exemplary embodiment to upstream reception data processing has not
only disadvantages but also advantages. Therefore, the functional
20 arrangement of upstream reception processing need not be identical to that
of downstream transmission processing. For example, functions may be
shared such that channel encoding processing is located at the center node
200 for downstream transmission processing, as in the sixth exemplary
embodiment, while channel decoding processing is located at the access
25 point 300 for upstream reception processing, as in, for example, the first
exemplary embodiment.
[0137]
(Seventh Exemplary Embodiment)
Fig. 18 is a diagram illustrating how protocol processing functions
54
are shared among a center node 200, a relay node 400, and a second access
point 500 according to a seventh exemplary embodiment. As illustrated
in Fig. 18, in the seventh exemplary embodiment, 'an L2 processing
function is located at the center node 200, as in, for example, the second
5 exemplary embodiment. A channel encoding processing functionlchannel
decoding processing function of an L1 processing function and a symbol
division function are located at the relay node 400. A
modulationldemodulation processing function of the L1 processing
function is located at the second access point 500.
10 [0138]
MAC-PDU is transmitted between the center node 200 and the relay
node 400, as in, for example, the second exemplary embodiment.
Channel-encoded data (downstream transmission data) divided for each
symbol is transmitted between the relay node 400 and the second access
15 point 500, as in transmission between the center node 200 and the access
point 300 in the sixth exemplary embodiment. Like the access point 300
according to the sixth exemplary embodiment, the second access point 500
performs modulation processing, precodinglbeam forming, and OFDM
symbol generation processing for each symbol, on the encoded data
20 received from the relay node 400.
[0139]
As in the sixth exemplary embodiment, in the seventh exemplary
embodiment, the same function sharing need not be performed in
downstream transmission processing and upstream reception processing.
25 In the seventh exemplary embodiment, as in, for example, the first
exemplary embodiment, since the center node 200 includes no wireless
signal processing function, processing in a general-purpose server 204 is
not complicated and can be easily implemented by, for example, a
general-purpose processor. In addition, since the unit of data
55
transmission between the relay node 400 and the second access point 500 is
small (because it is the symbol unit), the time to wait in data transmission
can be shortened.
[0 1401
5 (Eighth Exemplary Embodiment)
Fig. 19 is a diagram illustrating how protocol processing functions
are shared between a center node 200 and an access point 300 according to
an eighth exemplary embodiment. As illustrated in Fig. 19, in the eighth
exemplary embodiment, a PDCP processing function and MAC scheduling
10 function of an L2 processing function are located at the center node 200.
An RLC processing function and MAC packet decomposition/composition
function of the L2 processing function, and an L1 processing function are
located at the access point 300. In the eighth exemplary embodiment, a
data buffer 382 is further located at the access point 300.
15 [0141]
Upon performing PDCP processing by the PDCP processing
function, the center node 200 transmits PDCP - PDU (transmission data
main body) to the access point 300 before performing scheduling (at least
before the end of scheduling). The access point 300 stores PDCP-PDU
20 transmitted from the center node 200 in the data buffer 382.
[0 1421
The center node 200 performs scheduling processing in parallel
with PDCP PDU transmission. The center node 200 sends a scheduling
result instruction signal to the access point 300. The scheduling result
25 instruction signal represents a scheduling result indicating which data are
transmitted to which users (wireless terminals 120) (for example, to which
user a specific subframe is to be transmitted, whether retransmission or
new data transmission is to be performed, and the data size at this time).
The scheduling result signal includes, for example, a pointer and a data
size.
[0 1431
Note that the pointer indicates the start position of data
corresponding to a subframe to be transmitted to a user (wireless terminal
5 120) targeted for transmission in the transmission data main body
(PDCP-PDU) stored in the data buffer 382. In other words, the
scheduling result instruction signal represents data for identifying a user
(wireless terminal 120) targeted for transmission in the subframe, and the
start position (pointer) of data targeted for transmission and the size of the
10 data. The center node 200 sends a wireless resource instruction signal to
the access point 300, as in, for example, the first exemplary embodiment.
[0 1441
The access point 300 composes RLC - PDU and MAC-PDU in
accordance with a scheduling result instruction signal for a corresponding
I5 subframe, using the data (transmission data main body; PDCP-PDU)
received and stored in the data buffer 382 in advance. The access point
300 performs channel encoding processing, modulation processing, and
precodinglbeam forming processing in accordance with the wireless
resource instruction signal. The access point 300 converts a generated
20 baseband signal into a wireless signal and transmits the wireless signal to
the wireless terminal 120 targeted for transmission via an antenna 306.
[0 1451
After data (MAC-PDU) to be actually transmitted in each subframe
is determined, the center node 200 starts to transmit the data to the access
25 point 300. In this case, when data having a large unit is transmitted, the
time from the start of data transmission until the completion of data
transmission is prolonged. During the time to wait until the data
transmission is completed, the access point 300 cannot start the next
processing. Generally, in a specific subframe, which user (wireless
57
terminal 120) is set as a target for transmission, whether the data to be
transmitted will be retransmitted or transmitted as new data, the data size
at this time, and the like, are finally determined only after scheduling is
completed.
5 [0146]
In the eighth exemplary embodiment, the transmission data itself is
stored in the data buffer 382 of the access point 300 in advance.
Accordingly, at the time of the completion of scheduling, the center node
200 need not transmit the transmission data main body to the access point
10 300. In other words, the center node 200 need only indicate to the access
point 300, data for identifying a user targeted for transmission in the
subframe, and the data start positionlsize. In this manner, transmitting
the transmission data main body to the access point 300 in advance allows
considerable shortening of the time to wait in data transmission. This is
15 because the size of data (scheduling result instruction signal) required to
indicate data representing a user targeted for transmission and the data
start positionlsize is smaller than that of the transmission data main body.
Setting the priority of transmission of a transmit instruction (scheduling
result instruction signal) higher than that of transmission of the
20 transmission data main body prevents the transmission instruction
(scheduling result instruction signal) from interrupting the transmission
data main body transmitted in advance.
[0 1471
In the above-described eighth exemplary embodiment, as a method
25 for indicating transmission data, a scheduling result instruction signal
indicating the user identifier of a target for transmission and the start
positionlsize of transmission data is used, but the present invention is not
limited to this. For example, the present invention is not limited to the
above-mentioned method as long as the method used can indicate data
5 8
actually transmitted from the data stored in the data buffer 382 of the
access point 300 in advance.
[0 1481
Function sharing of downstream transmission processing and
5 function sharing of upstream reception processing are the same in Fig. 19,
but they may be different from each other. In other words, an upstream
signal whose wait time needs to be shortened is a signal indicating an
ACKINACK response to downstream data and whether upstream data have
been successfully received (CRC check result). The data size of the
10 signal indicating an ACKINACK response and a CRC check result is
relatively small. Setting the priority of transmission for these data to be
high achieves a sufficiently short time to wait for transmission completion.
Therefore, functions may be shared differently between downstream
transmission processing and upstream reception processing such that an L2
15 reception processing function is located at the center node 200 and an L1
reception processing function is located at the access point 300, for
upstream reception processing, as in, for example, the first exemplary
embodiment.
[0 1491
20 (Ninth Exemplary Embodiment)
Fig. 20 is a diagram illustrating how protocol processing functions
are shared between a center node 200 and an access point 300 according to
a ninth exemplary embodiment. As illustrated in Fig. 20, in the ninth
exemplary embodiment, an L2 processing function, and a channel encoding
25 functionlchannel decoding function and modulationldemodulation function
of an L1 processing function are located at the center node 200. A
physical antenna mapping function of the L1 processing function is located
at the access point 300. The physical antenna mapping function is the
function of mapping logical antenna ports to physical antenna ports. The
59
physical antenna mapping function is the same as the function of the
physical antenna mapping unit 356, described with reference to Fig. 13 in
the third exemplary embodiment, and performs weighted summation
processing for each antenna. The effective amount of information
5 corresponding to logical antenna ports is smaller than that corresponding
to physical antennas. Therefore, compared to CPRI transmission
according to the above-mentioned related-art technique, the amount of
information in the transmission line between the center node 200 and the
access point 300 can be reduced.
10 [0150]
Although functions are shared between the center node 200 and the
access point 300 in Fig. 20, the present invention is not limited to this.
Functions may be assigned to a relay node 400, as in the second or seventh
exemplary embodiment. In this case, only an L2 processing function may
15 be located at the center node 200, and a channel encoding function and
modulation/demodulation function of an L1 processing function may be
located at the relay node 400.
[0151]
(Modification)
20 The present invention is not limited to the above-described
exemplary embodiments and may be changed as appropriate without
departing from the spirit of the present invention. The configuration of
each exemplary embodiment is applicable to other exemplary embodiments.
For example, the configuration of the second exemplary embodiment is
25 also applicable to the third exemplary embodiment.
[0152]
In addition, although the present invention has been described as
hardware configuration in the above-described exemplary embodiments,
the present invention is not limited to this. In the present invention, the
60
processing of each circuit in each device constituting the wireless
communication system can also be implemented by causing a CPU (Central
Processing Unit) to execute a computer program.
[0153]
5 In the above-mentioned example, the program is stored using a
variety of non-transitory computer readable media and can be supplied to
the computer. The non-transitory computer readable media include a
variety of tangible storage media. Examples of the non-transitory
computer readable media include magnetic recording media (for example, a
10 flexible disk, a magnetic tape, and a hard disk drive), magnetooptical
recording media (for example, a magnetooptical disk), a CD-ROM (Read
Only Memory), a CD-R, a CD-RIW, and semiconductor memories (for
example, a mask ROM, a PROM (Programmable ROM), an EPROM
(Erasable PROM), a flash ROM, and a RAM (Random Access Memory)).
15 The program may be supplied to the computer using a variety of transitory
computer readable media. Examples of the transitory computer readable
media include electrical signals, optical signals, and electromagnetic
waves. The transitory computer readable media can supply the program
to the computer via wired communication paths such as electrical wires and
20 optical fibers or wireless communication paths.
[0 1543
A part or all of the above-described exemplary embodiments may be
described as in the following supplementary notes, but they are not limited
thereto.
25 [0155]
(Supplementary Note 1)
A wireless communication system comprising:
a wireless control device; and
at least one wireless device which is connected to the wireless
6 1
control device via a transmission line and wirelessly communicates with a
wireless terminal,
wherein the wireless control device includes:
wireless resource allocation means for allocating a wireless
5 resource used by the wireless device in wirelessly communicating with the
wireless terminal; and
wireless resource instruction means for sending an instruction for
allowing use of the allocated wireless resource to the wireless device, and
the wireless device includes:
10 wireless signal processing means for executing processing to
perform wireless communication using the allocated wireless resource, on
data to be sent to the wireless terminal, on the basis of the instruction from
the wireless control device; and
wireless transmission means for converting a signal processed by
15 the wireless signal processing means into a wireless signal and
transmitting the wireless signal to the wireless terminal.
(Supplementary Note 2)
The wireless communication system according to supplementary
note 1, wherein
20 the wireless device includes a plurality of wireless devices,
the wireless control device further includes wireless device
selection means for selecting the wireless device to wirelessly
communicate with the wireless terminal, and
the selected wireless device wirelessly communicates with the
25 wireless terminal.
(Supplementary Note 3)
The wireless communication system according to supplementary
note 2, wherein
the wireless control device further includes wireless device control
62
means for controlling the plurality of wireless devices to perform a
cooperative operation, and
the plurality of wireless devices performs a cooperative operation
under the control of the wireless device control means.
5 (Supplementary Note 4)
The wireless communication system according to any one of
supplementary notes 1 to 3, wherein
the wireless device includes a plurality of antennas, and
the wireless signal processing means performs antenna weighting
10 processing for each of the plurality of antennas.
(Supplementary Note 5)
The wireless communication system according to any one of
supplementary notes 1 to 4, wherein the wireless signal processing means
performs channel encoding processing and channel decoding processing,
15 and modulation processing and demodulation processing.
(Supplementary Note 6)
The wireless communication system according to any one of
supplementary notes 1 to 4, wherein
the wireless control device performs channel encoding processing
20 on transmission data, divides the transmission data having undergone the
channel encoding processing, for each symbol that is a unit of modulation
processing, and transmits the transmission data to the wireless device, and
the wireless device performs modulation processing for each
symbol, on the transmission data transmitted from the wireless control
25 device.
(Supplementary Note 7)
The wireless communication system according to any one of
supplementary notes 1 to 4, wherein
the wireless control device
63
transmits the transmission data to the wireless device before end of
scheduling processing, and
sends a scheduling result instruction signal indicating a scheduling
result to the wireless device after the end of the scheduling processing, and
5 the wireless device
stores the transmission data transmitted from the wireless control
device, and
transmits to the wireless terminal, a wireless signal representing
data to be sent to the wireless terminal of the stored transmission data, on
10 the basis of the scheduling result instruction signal.
(Supplementary Note 8)
A wireless communication system comprising:
a wireless control device;
at least one wireless device which wirelessly communicates with a
15 wireless terminal; and
a relay device which is interposed between the wireless control
device and the wireless device, connected to the wireless control device
via a first transmission line, and connected to the wireless device via a
second transmission line, wherein
20 the wireless control device includes:
wireless resource allocation means for allocating a wireless
resource used by the wireless device in wirelessly communicating with the
wireless terminal; and
wireless resource instruction means for sending an instruction for
25 allowing use of the allocated wireless resource to the relay device,
wherein the relay device executes processing to perform wireless
communication using the allocated wireless resource, on data to be sent to
the wireless terminal, on the basis of the instruction from the wireless
control device, and
64
the wireless device converts a signal processed by the wireless
signal processing means into a wireless signal and transmits the wireless
signal to the wireless terminal.
(Supplementary Note 9)
5 The wireless communication system according to supplementary
note 8, wherein the relay device performs channel encoding processing and
channel decoding processing, and modulation processing and demodulation
processing.
(Supplementary Note 10)
10 The wireless communication system according to supplementary
note 8, wherein
the relay device performs channel encoding processing on
transmission data, divides the transmission data having undergone the
channel encoding processing, for each symbol that is a unit of modulation
15 processing, and transmits the transmission data to the wireless device, and
the wireless device performs modulation processing for each
symbol, on the transmission data transmitted from the wireless control
device.
(Supplementary Note 11)
20 A wireless communication method for a wireless communication
system comprising: a wireless control device; and at least one wireless
device which is connected to the wireless control device via a transmission
line and wirelessly communicates with a wireless terminal, the method
comprising:
25 in the wireless control device,
allocating a wireless resource used by the wireless device in
wirelessly communicating with the wireless terminal; and
sending an instruction for allowing use of the allocated wireless
resource to the wireless device, and
65
in the wireless device,
executing processing to perform wireless communication using the
allocated wireless resource, on data to be sent to the wireless terminal, on
the basis of the instruction from the wireless control device; and
5 converting a signal processed by the wireless signal processing
means into a wireless signal and transmitting the wireless signal to the
wireless terminal.
(Supplementary Note 12)
A wireless control device connected via a transmission line to at
10 least one wireless device which wirelessly communicates with a wireless
terminal, the wireless control device comprising:
wireless resource allocation means for allocating a wireless
resource used by the wireless device in wirelessly communicating with the
wireless terminal; and
15 wireless resource instruction means for sending an instruction for
allowing use of the allocated wireless resource to the wireless device.
(Supplementary Note 13)
The wireless control device according to supplementary note 12,
further comprising:
20 wireless device selection means for selecting the wireless device to
wirelessly communicate with the wireless terminal from a plurality of the
wireless devices.
(Supplementary Note 14)
The wireless coiltrol device according lo suppleilleiltary note 13,
25 further comprising:
wireless device control means for controlling the plurality of .
wireless devices to perform a cooperative operation.
(Supplementary Note 15)
A wireless device which wirelessly communicates with a wireless
6 6
terminal and is connected to a wireless control device via a transmission
line, the wireless device comprising:
wireless signal processing means for executing processing to
perform wireless communication using a wireless resource used by the
5 wireless device in wirelessly communicating with the wireless terminal, on
data to be sent to the wireless terminal, on the basis of an instruction
configured to allow use of the wireless resource and sent by the wireless
control device; and
wireless transmission means for converting a signal processed by
10 the wireless signal processing means into a wireless signal and
transmitting the wireless signal to the wireless terminal.
(Supplementary Note 16)
The wireless device according to supplementary note 15, further
comprising:
15 a plurality of antennas,
wherein the wireless signal processing means performs antenna
weighting processing for each of the plurality of antennas.
(Supplementary Note 17)
A relay device
20 being interposed between a wireless control device and at least one
wireless device which wirelessly communicates with a wireless terminal,
being connected to the wireless control device via a first
transmission line and connected to the wireless device via a second
transmission line, and
25 configured to execute processing to perform wireless
communication using a wireless resource used by the wireless device in
wirelessly communicating with the wireless terminal, on data to be sent to
the wireless terminal, on the basis of an instruction configured to allow use
of the wireless resource and sent by the wireless control device.
67
(Supplementary Note 18)
A wireless communication method for a wireless control device
connected via a transmission line to at least one wireless device which
wirelessly communicates with a wireless terminal, the method comprising:
5 allocating a wireless resource used by the wireless device in
wirelessly communicating with the wireless terminal; and
sending an instruction for allowing use of the allocated wireless
resource to the wireless device.
(Supplementary Note 19)
10 A wireless communication method for a wireless device which
wirelessly communicates with a wireless terminal and is connected to a
wireless control device via a transmission line, the method comprising:
executing processing to perform wireless communication using a
wireless resource used by the wireless device in wirelessly communicating
15 with the wireless terminal, on data to be sent to the wireless terminal, on
the basis of an instruction configured to allow use of the wireless resource
and sent by the wireless control device; and
converting a processed signal into a wireless signal and
transmitting the wireless signal to the wireless terminal.
20 (Supplementary Note 20)
A wireless communication method for a relay device interposed
between a wireless control device and at least one wireless device which
wirelessly communicates with a wireless terminal, the method comprising:
executing processing to perform wireless communication using a
25 wireless resource used by the wireless device in wirelessly communicating
will1 the wireless lerrninal, ~ IcIla la lu be sell1 lu the wireless lerrnil~al,u n
the basis of an instruction configured to allow use of the wireless resource
and sent by the wireless control device.
[0156]
6 8
Although the present invention has been described above with
reference to the above-described exemplary embodiments, the present
invention is not limited thereto. Various changes which would be
understood by those skilled in the art may be made to the configurations
5 and details of the present invention within the scope of the invention.
[0157]
This application claims priority based on Japanese Patent
Application No. 20 14- 134 1 1 1 filed on June 30, 20 14, the disclosure of
which is incorporated herein in its entirety.
10 Reference signs List
[0158]
1 wireless communication system
10 transmission line
20 wireless control device
15 22 wireless resource allocation unit
24 wireless resource instruction unit
3 0 wireless device
32 wireless signal processing unit
34 wireless transmission unit
20 100 wireless communication system
102 backhaul
104 core network
1 10 transmission line
1 12 transmission line
25 120 wireless terminal
150 wireless cvrrirriur~icativrs~y stem
200 center node
202 reference clock generation unit
204 general-purpose server
206 transmission line interface
210 software
2 12 synchronizing unit
214 radio channel quality management unit
5 2 16 access point selection unit
21 8 wireless resource management unit
220 wireless resource allocation unit
222 access point control unit
240 PDCP processing unit
10 250 RLC processing unit
260 MAC processing unit
300 access point
302 transmission line interface
304 wireless transmission/reception unit
15 306 antenna
3 10 wireless signal processing unit
3 12 channel encoding unit
3 14 modulation unit
3 16 physical antenna mapping unit
20 322 physical antenna synthesis unit
324 demodulation unit
326 channel decoding unit
342 user processing unit
344 control channellsignal processing unit
25 352 resource element mapping unit
354 OFDM symbol generation unit
356 physical antenna mapping unit
362 channel encoding unit
364 modulation mapping unit
I
70
366 layer mapping unit
368 precoding unit
372 resource element mapping unit
374 OFDM symbol generation unit
5 376 physical antenna mapping unit
378 beam forming unit
380 HARQ buffer
382 data buffer
400 relay node
10 402 transmission line interface
404 transmission line interface
410 wireless signal processing unit
500 second access point
502 transmission line interface
15 504 wireless transmission/reception unit
506 antenna
CLAIMS
(Claim 1)
A wireless communication system comprising:
a wireless control device; and
5 at least one wireless device which is connected to the wireless
control device via a transmission line and wirelessly communicates with a
wireless terminal,
wherein the wireless control device includes:
wireless resource allocation means for allocating a wireless
10 resource used by the wireless device in wirelessly communicating with the
wireless terminal; and
wireless resource instruction means for sending an instruction for
allowing use of the allocated wireless resource to the wireless device, and
the wireless device includes:
15 wireless signal processing means for executing processing to
perform wireless communication using the allocat.ed wireless resource, on
data to be sent to the wireless terminal, based on the instruction from the
wireless control device; and
wireless transmission means for converting a signal processed by
20 the wireless signal processing means into a wireless signal and
transmitting the wireless signal to the wireless terminal.
(Claim 2)
'l'he wireless communication system according to Claim I ,
25 wherein the wireless device includes a plurality of wireless devices,
wherein the wireless control device further includes wireless device
sclection mcans for sclccting thc wirclcss dcvicc to wirclcssly
coillilluilicate wit11 the wireless terminal, aiid
wherein the selected wireless device wirelessly communicates with
the wireless terminal
(Claim 3)
The wireless communication system according to Claim 2,
5 wherein the wireless control device further includes wireless device
control means for controlling the plurality of wireless devices to perform a
cooperative operation, and
wherein the plurality of wireless devices performs a cooperative
operation under the control of the wireless device control means.
10
(Claim 4)
The wireless communication system according to any one of Claims
1 to 3,
wherein the wireless device includes a plurality of antennas, and
15 the wireless signal processing means performs antenna weighting
processing for each of the plurality of antennas.
(Claim 5)
The wireless communication system according to any one of Claims
20 1 to 4,
wherein the wireless signal processing means performs channel
encoding processing and channel decoding processing, and modulation
processing and demodulation processing.
25 (Claim 6)
The wireless communicalion syslem according lo ariy orit: o l Clairris
1 to 4, wherein
the wireless control device performs channel encoding processing
on transmission data, divides tlie transmission data having undergone the
73
channel encoding processing, for each symbol that is a unit of modulation
processing, and transmits the transmission data to the wireless device, and
the wireless device performs modulation processing for each
symbol, on the transmission data transmitted from the wireless control
5 device.
(Claim 7)
The wireless communication system according to any one of Claims
1 to 4, wherein
10 the wireless control device
transmits the transmission data to the wireless device before end of
scheduling processing, and
sends a scheduling result instruction signal indicating a scheduling
result to the wireless device after the end of the scheduling processing, and
15 the wireless device
stores the transmission data transmitted from the wireless control
device, and
transmits to the wireless terminal, a wireless signal representing
data to be sent to the wireless terminal of the stored transmission data,
20 based on the scheduling result instruction signal.
(Claim 8)
A wireless communication system comprising:
a wireless control device;
at least one wireless device which wirelessly communicates with a
wireless terminal; and
a relay device which is interposed between the wireless control
device and the wireless device, connected to the wireless control device
via a first transmission line, and connected to the wireless device via a
74
second transmission line, wherein
the wireless control device includes:
wireless resource allocation means for allocating a wireless
resource used by the wireless device in wirelessly communicating with the
5 wireless terminal; and
wireless resource instruction means for sending an instruction for
allowing use of the allocated wireless resource to the relay device,
wherein the relay device executes processing to perform wireless
communication using the allocated wireless resource, on data to be sent to
10 the wireless terminal, based on the instruction from the wireless control
device, and
the wireless device converts a signal processed by the wireless
signal processing means into a wireless signal and transmits the wireless
signal to the wireless terminal.
15
(Claim 9)
The wireless communication system according to claim 8,
wherein the relay device performs channel encoding processing on
transmission data, divides the transmission data having undergone the
20 channel encoding processing, for each symbol that is a unit of modulation
processing, and transmits the transmission data to the wireless device, and
wherein the wireless device performs modulation processing for
each symbol, on the transmission data transmitted from the wireless
control device.
25
(Claim 10)
A wireless communication method for a wireless communication
system comprising: a wireless control device; and at least one wireless
device which is connected to the wireless control device via a transmission
7 5
line and wirelessly communicates with a wireless terminal, the method
comprising:
in the wireless control device,
allocating a wireless resource used by the wireless device in
5 wirelessly communicating with the wireless terminal; and
sending an instruction for allowing use of the allocated wireless
resource to the wireless device, and
in the wireless device,
executing processing to perform wireless communication using the
10 allocated wireless resource, on data to be sent to the wireless terminal,
based on the instruction from the wireless control device; and
converting a signal processed by the wireless signal processing
means into a wireless signal and transmitting the wireless signal to the
wireless terminal.