FIELD OF INVENTION
[0001] The present subject matter relates to device-to-device communication and,
more particularly but not exclusively, to channel resource allocation for device-5 ce-to-device
communication in cellular communication networks.
BACKGROUND
[0002] Communication devices, such as cellular phones, smart phones, personal
digital assistants (PDAs), portable computers, and desktop computers, provide users with a
10 variety of mobile communication services and computer networking capabilities. These
communication services allow data to be exchanged between the network operators and the
users. Usually the communication devices transmit data using various wireless
communication networks, such as Global System for Mobile Communication (GSM)
network, Universal Mobile Telecommunications System (UMTS) network, Wideband Code
15 Division Multiple Access (W-CDMA) network, and Long Term Evolution (LTE).
[0003] In recent times there has been a rapid increase in the use of communication
devices, resulting in increase in the volume of access requests made for accessing the wireless
communication networks. Data transfer over the wireless communication networks may thus
not be a speedy and efficient process. Network operators have thus been involved in
20 development of alternate communication techniques, such as device-to-device (D2D)
communication. D2D communication concerns wireless communications directly between
two communication devices. For example, WiFi Direct is a technique by which devices can
directly communicate over WiFi channels without any intermediary nodes.
[0004] Using D2D communication instead of the conventional wireless network may
25 result in various benefits. For instance, using a wireless communication link established
directly between two communication devices may result in reduction in transmitter power
consumption; improvement in network resource utilization; increased cellular communication
network capacity and coverage; support for additional services, such as heavy data packet
transfer; and peer-to-peer services, such as home entertainment systems and vehicle-to30
vehicle communications.
3
SUMMARY
[0005] This summary is provided to introduce concepts related to systems and
methods for device-to-device communication in a cellular communication network. This
summary is neither intended to identify features of the claimed subject matter nor is it
intended for use in determining or limiting the scope of the claimed subject ma5 tter.
[0006] In one implementation a central controller, such as a base station, for
allocating channel resources for device to device (D2D) communication in a cellular
communication network is described. The central controller may include a processor and a
channel resource allocation module coupled to the processor. The channel resource allocation
10 module may allocate channel resources to D2D users and regular mobile users in a
scheduling interval, based on allocation criteria. Based on the allocation, a scheduling grant
may be provided to one or more transmitters in a cell controlled by the central controller.
Further, the scheduling grant is indicative of availability of the channel resources for D2D
communication in the scheduling interval.
15 [0007] In another implementation, a transmitter in D2D communication with a
receiver in a cellular communication network is described. The transmitter includes a
processor, a resource availability determination coupled to the processor, and a transmission
module coupled to the processor. The resource availability module may ascertain whether
channel resources for D2D communication in a scheduling interval are available, based on a
20 resource availability sensing technique and a received scheduling grant. Further, the
transmission module may determine a number of channel resources available for transmission
in the scheduling interval and construct a data packet, based on the number of channel
resources. The data packet may include a header indicative of the size of the data packet and
a data transmission rate per channel resource. Further, the data packet may be transmitted
25 over one or more scheduling intervals, based on the number of channel resources and a size
of data to be transmitted. Additionally, in an implementation, the transmission module
initiates a back-off procedure, when the channel resources are available, and wherein the data
packet is transmitted based on the back-off procedure.
[0008] In yet another implementation, the resource availability determination module
30 may decode the header of another data packet being transmitted over channel resources
allotted for D2D communication; and ascertain, based on decoding, whether transmission of
4
the another data packet will be completed in the scheduling interval. Based on the
ascertainment, a flag may be set to indicate that the channel resources will be available in the
current scheduling interval, when it is ascertained that the transmission of the another data
packet will be completed in the current scheduling interval.
[0009] In yet another implementation, a receiver in D2D communication with 5 th a
transmitter in a cellular communication network is described. The receiver includes a
processor and a data retrieval module coupled to the processor. The data retrieval module
may decode a received data packet based on a header of the received data packet and transmit
an acknowledgement, based on decoding, on a control channel resource to a transmitter.
10 Further, the control channel resource is reserved by a central controller for transmitting
acknowledgements.
[0010] In an implementation, a method for allocating channel resources for D2D
communication in a cellular communication network is described. The method includes
allocating channel resources to D2D users and regular mobile users in a scheduling interval,
15 based on allocation criteria and providing based on the allocation, a scheduling grant to one
or more transmitters in a cell controlled by a central controller. The scheduling grant is
indicative of availability of the channel resources for D2D communication in the scheduling
interval. Further, the method includes reserving a channel resource from the allocated channel
resources for sharing acknowledgements.
20 [0011] In yet another implementation, a method for transmitting data for D2D
communication in a cellular communication network is described. The method includes
ascertaining whether channel resources for D2D communication in a scheduling interval are
available, based on a resource availability sensing technique and a received scheduling grant.
Based on ascertaining, a number of channel resources available for transmission in the
25 scheduling interval. Further, a data packet may be constructed, based on the number of
channel resources, wherein the data packet comprises a header indicative of the size of the
data packet and a data transmission rate per channel resource. The data packet may be
transmitted over one or more scheduling intervals, based on the number of channel resources
and a size of data to be transmitted.
5
[0012] In an implementation, the method includes initiating a back-off procedure,
when the channel resources are available, wherein the data packet is transmitted based on
execution of the back-off procedure.
[0013] In yet another implementation, the method includes decoding the header of
another data packet being transmitted over channel resources allotted 5 tted for D2D
communication and ascertaining, based on decoding, whether transmission of the another
data packet will be completed in the scheduling interval. Further, a flag may be set to indicate
that the channel resources will be available in the current scheduling interval, when it is
ascertained that the transmission of the another data packet will be completed in the current
10 scheduling interval.
[0014] In yet another implementation, receiving data for D2D communication in a
cellular communication network is described. The method includes decoding a received data
packet based on a header of the received data packet and transmitting an acknowledgement,
based on decoding, on a control channel resource to a transmitter. The control channel
15 resource may be reserved by a central controller for transmitting acknowledgements.
[0015] In yet another implementation, a non-transitory computer-readable medium
having embodied thereon a computer program for executing a method for D2D
communication in a cellular communication network is described. The method includes
ascertaining whether channel resources for D2D communication in a scheduling interval are
20 available, based on a resource availability sensing technique and a received scheduling grant.
Based on ascertaining, a number of channel resources available for transmission in the
scheduling interval. Further, a data packet may be constructed, based on the number of
channel resources, wherein the data packet comprises a header indicative of the size of the
data packet and a data transmission rate per channel resource. The data packet may be
25 transmitted over one or more scheduling intervals, based on the number of channel resources
and a size of data to be transmitted.
BRIEF DESCRIPTION OF THE FIGURES
[0016] The detailed description is described with reference to the accompanying
figures. In the figures, the left-most digit(s) of a reference number identifies the figure in
30 which the reference number first appears. The same numbers are used throughout the figures
6
to reference like features and components. Some embodiments of system or methods in
accordance with embodiments of the present subject matter are now described, by way of
example, and with reference to the accompanying figures, in which:
[0017] Fig. 1 illustrates a cellular communication network for device-to-device
communication, in accordance with an embodiment of the present subject matt5 er;
[0018] Fig. 2 illustrates nodes of the cellular communication network in device to
device communication, in accordance with an embodiment of the present subject matter.
[0019] Fig. 3 illustrates a timing diagram indicating procedures of allocating channel
resources for device-to-device communication in a cellular communication network, in
10 accordance with an embodiment of the present subject matter; and
[0020] Fig. 4 illustrates a method for allocating channel resources for device-todevice
communication in a cellular communication network, in accordance with an
embodiment of the present subject matter; and
[0021] Fig. 5 illustrates a method for transmitting data using a device to device
15 communication technique in a cellular communication network, according to an embodiment
of the present subject matter.
[0022] It should be appreciated by those skilled in the art that any block diagrams
herein represent conceptual views of illustrative systems embodying the principles of the
present subject matter. Similarly, it will be appreciated that any flow charts, flow diagrams,
20 state transition diagrams, pseudo code, and the like, represent various processes which may
be substantially represented in computer readable medium and so executed by a computer or
processor, whether or not such computer or processor is explicitly shown.
DESCRIPTION OF EMBODIMENTS
[0023] Systems and methods for device-to-device (D2D) communication in a cellular
25 communication network are described. D2D communication, as will be understood, refers to
wireless communication happening directly between two or more communication devices.
For instance, two communication devices in proximity to each other may communicate
directly, instead of communicating via a base station. Transmitting data directly between two
communication devices facilitates reduction in transmission power consumption. Enhanced
7
connectivity using the D2D communication link allows the users to utilize data intensive
multimedia services, such as Push-to-X video calling, live media streaming, and online
gaming.
[0024] Conventionally, D2D communication has only been used in context of
unlicensed spectrum or a dedicated spectrum. However, both the approaches have certai5 n
limitations. For example, implementation of D2D communication mode may require
upgrading the communication devices to operate in the unlicensed spectrum, thus affecting its
acceptance and usage among users. Further, there may be issues regarding quality of service
of the D2D communication and efficiency in terms of spectrum usage.
10 [0025] Further, the implementation of D2D communication in cellular
communication networks may pose certain challenges, which may not be addressed by
existing D2D protocols. For example, in case the D2D communication is used in a cellular
communication network, the cellular communication network will now be shared between
D2D users and regular mobile users, and so channel resources available for the D2D
15 communication may not be fixed. Therefore, D2D protocols, such as CSMA/CA, and
FlashLinQ which are designed for fixed bandwidth systems may not operate in such scenario.
[0026] Moreover, a cellular communication network has a slotted and a synchronous
architecture, while existing D2D protocols, such as CSMA/CA are designed for
asynchronous architecture and thus, may not be able to leverage benefits from the
20 architecture of the cellular communication network. For example, transmission of request to
send (RTS) frames, clear to send (CTS) frames, interframe spacings (IFS), such as, short
interframe spacing (SIFS) and distributed interframe spacings (DIFS), and asynchronous
acknowledgements, such as ACKS and NACKS may result in wastage of channel resources,
which in turn may lower the efficiency of D2D communications. Additionally, absence of
25 any central station for controlling the D2D communication affects the quality of service of
the D2D communication.
[0027] According to an implementation of the present subject matter, systems and
methods for D2D communication in a cellular communication network are described. In one
embodiment, two or more communication devices communicating with each other over a
30 cellular communication network, such as Long Term Evolution (LTE) network or Wideband
Code Division Multiple Access (WCDMA) network, may initiate a D2D communication in
8
order to exchange data using channel resources available in the cellular communication
network. In an implementation, channel resources may be allocated to one or more pairs of
user equipments, each pair of user equipment being referred to as a D2D link. A D2D link
may thus include a transmitting node, i.e., a transmitter, and a receiving node, i.e., a receiver
in direct communication with each other. Further, the transmitter may provide data 5 ta packets to
the receiver over the allocated channel resources.
[0028] In an implementation, a cell of the cellular communication network may
include multiple D2D links and a central controller, such as a base station. Further, channel
resources of the cellular communication network may be shared between regular mobile users
10 and D2D users. Regular mobile users may be understood to include user equipments that use
channel resources for regular cellular services, while D2D users refers to those user
equipments, which have registered for D2D services.
[0029] In an example, the central controller may divide channel resources in a
scheduling interval between regular mobile users and D2D users, based on resource
15 allocation criteria. In an example, the allocation criteria may indicate that regular mobile
traffic is to be prioritized over D2D traffic in some or all of the scheduling intervals. In
another example, the channel resources may be divided in predetermined percentages, for
instance, 70 percent to regular traffic and 30 percent to D2D traffic. Further, a scheduling
interval may be a predetermined time-interval based on type of cellular communication
20 network. For example, the scheduling interval may be 1 millisecond (ms) in LTE and may be
2 ms in WCDMA. Further, each scheduling interval may again comprise multiple symbols,
for example, a scheduling interval in LTE may comprise fourteen symbols.
[0030] Based on the allocation criteria, the channel resources may be allocated for the
D2D users. Further, based on the allocation, a scheduling grant indicative of the availability
25 of the channel resources is transmitted to all transmitters in the cell. For example, in case the
channel resources are not available, the scheduling grant may not be provided to the D2D
users, while in case the channel resources are available for D2D communication, the
scheduling grant indicating the availability of the channel resources and information
pertaining to the available channel resources may be provided. Further, the scheduling grant
30 for a particular scheduling interval may be provided a predetermined number of scheduling
intervals in advance so that the transmitters have sufficient time to construct and transmit data
9
packets in the particular scheduling interval. For example, in LTE, information pertaining to
available channel resources may be provided three scheduling intervals in advance.
[0031] In an implementation, a transmitter that has to transmit data in D2D
communication mode may ascertain whether any channel resources are available for data
transmission in a scheduling interval, based on scheduling grant received for that schedulin5 g
interval. Further, the transmitter may ascertain whether the available channel resources are
free for data transmission in the scheduling interval using a resource availability sensing
technique, such as physical carrier sensing technique and virtual carrier sensing technique.
The resource availability determination technique may be understood as a technique that
10 involves carrier sensing of a medium, by a node prior to transmission, to determine if any
other node is transmitting using the medium.
[0032] In an example, if it is determined that the channel resources are unavailable,
the availability may be checked throughout the scheduling interval, for example, in each
symbol of the scheduling interval.
15 [0033] However, in case it is ascertained that the channel resources are available for
data transmission, a number of channel resources available for transmission in the scheduling
interval may be determined. It will be appreciated that since the channel resources allocated
to D2D users may not be fixed, therefore the number of channel resources available in a
scheduling interval may be different from the number channel resources available in another
20 scheduling interval. Accordingly, based on the number of available channel resources and the
size of data to be transmitted, a data packet may be constructed. Further, the transmission of
the data packet may span over multiple scheduling intervals based on the size of the data to
be transmitted and number of available resources in each of the multiple scheduling intervals.
In case the data packet is not transmitted completely in the current scheduling interval, the
25 remaining portion of the data packet is sent in next scheduling interval based on availability
of channel resources in the next scheduling interval. Further, in such cases, the size of data
blocks, of the data packet, sent subsequently may be reset based on the availability of the
channel resources in the next scheduling intervals.
[0034] Each data packet may include a preamble, a header, and one or more data
30 blocks. The preamble may include reference sequences defined for the type of cellular
communication network, such as LTE, being used. Further, the header may include a size of
10
the data packet, a data transmission rate per channel resource, a source address, and a
destination address. The header information also helps other transmitters in determining
duration of the transmission. For example, another transmitter may decode the header to
obtain the information pertaining to size of the data being transmitted and the data
transmission rate per channel resource. Accordingly, the transmitter may determine whet5 her
the channel resources are available in a given scheduling interval and a duration for which the
channel resources are busy in the scheduling interval, based on the header information. For
example, the transmitter may determine whether or not transmission will finish in a current
scheduling interval. If the transmission can not be completed in the current scheduling
10 interval, the transmitter may check for availability of the channel resources in next scheduling
interval, till the channel resources become available.
[0035] It will be understood that as allocation of the channel resources may vary from
one scheduling interval to next, therefore duration of transmission can not be estimated in
advance. Conventionally, upon determining that channel resources are currently being used
15 by some other transmitter, a contending transmitter obtains data transmission duration from
RTS or CTS frames. The RTS or CTS frames indicate to a transmitter that the channel
resources are currently busy and the transmitter should refrain from sending data for a given
time, i.e., the data transmission duration.
[0036] However, in the present case, since the duration of the transmission can not be
20 known in advance, periodic checking by transmitters, based on the header information help
addressing the concern, without wasting channel resources by transmitting RTS and CTS
frames. Accordingly, the channel resources that are used for sharing RTS/CTS frames may
now be used for data transmission, thereby enhancing the capacity available for and
efficiency of D2D communication in the cellular communication networks.
25 [0037] Further, header information of the transmitted data packet may also be used by
a receiving node, also referred to as a receiver, to identify the data packet to be received. For
example, the receiver in a D2D link identifies a data packet meant for it by determining the
destination address in the header. Upon receiving the complete data packet, the received data
packet may be decoded to retrieve the data. Further, based on decoding, an acknowledgement
30 message indicating successful decoding or unsuccessful decoding may be sent. In an
example, instead of sending the acknowledgement message on a regular data channel, the
11
acknowledgement message is sent over a control channel resource, which may be reserved
for nodes to send acknowledgements.
[0038] Since, acknowledgement messages may be now sent on a separate
synchronized control channel and RTS/ CTS may not be shared among nodes, SIFS and
DIFS intervals, which are periods of silence in which no node makes transmissions, may 5 be
removed, which in turn may result in more efficient utilization of channel resources. Thus,
the present subject matter provides for efficient utilization of channel resources, which may
be shared between the regular and D2D users.
[0039] It should be noted that the description and figures merely illustrate the
10 principles of the present subject matter. It will thus be appreciated that those skilled in the art
will be able to devise various arrangements that, although not explicitly described or shown
herein, embody the principles of the present subject matter and are included within its spirit
and scope. Furthermore, all examples recited herein are principally intended expressly to be
for pedagogical purposes to aid the reader in understanding the principles of the present
15 subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to
be construed as being without limitation to such specifically recited examples and conditions.
Moreover, all statements herein reciting principles, aspects, and embodiments of the present
subject matter, as well as specific examples thereof, are intended to encompass equivalents
thereof.
20 [0040] It will also be appreciated by those skilled in the art that the words during,
while, and when as used herein are not exact terms that mean an action takes place instantly
upon an initiating action but that there may be some small but reasonable delay, such as a
propagation delay, between the initial action and the reaction that is initiated by the initial
action. Additionally, the words “connected” and “coupled” are used throughout for clarity of
25 the description and can include either a direct connection or an indirect connection.
[0041] The manner in which the systems and the methods of device-to-device
communication in a cellular communication network may be implemented has been
explained in details with respect to the Figures 1 to 5. While aspects of described systems and
methods for device-to-device communication in a cellular communication network can be
30 implemented in any number of different computing systems and transmission environments,
the embodiments are described in the context of the following system(s).
12
[0042] Fig. 1 illustrates a cell 100 of a cellular communication network, which may
be used for device-to-device communication according to an embodiment of the present
subject matter. The cellular communication network may be, for example, LTE and
WCDMA. The communication network includes one or more user equipments
communicating with each other and a central controller 102 over one or more 5 channel
resources allocated by the central controller 102 for D2D communication. D2D
communication, as will be understood, is a mode of communication used for communication
between two user equipments, say, a transmitter and a receiver proximate to each other.
[0043] The user equipments may be implemented as one or more of cellular phones,
10 smart phones, personal digital assistants (PDAs), portable computers, desktop computers,
tablet computers, tablets, and the like. Further, the user equipments include one or more
transmitters 104-1, 104-2, 104-3…, 104-n, hereinafter collectively referred to as transmitters
104 and individually referred to as transmitter 104, and one or more receiving nodes 106-1,
106-2,106-3 …, 106-n, hereinafter collectively referred to as receiving nodes 106 and
15 individually referred to as receiving node 106. In one implementation, each transmitter 104
may be communicating with a corresponding receiver 106 over allocated channel resources
thus forming a pair of equipment devices, hereinafter referred to as a D2D link. For instance,
the transmitter 104-1 and the receiver 106-1 may communicate with each other forming a
D2D link 108-1. Similarly, the transmitter 104-2 and the receiver 106-2 may form a D2D link
20 108-2 and the transmitter 104-n and the receiver 106-n may form a D2D link 108-n. The D2D
links 108-1, 108-2, 108-3, 108-4, …, 108-n may be hereinafter collectively referred to as
D2D links 108 and individually referred to as D2D link 108. For the sake brevity, only D2D
user equipments have been illustrated; however it will be understood that the cell 100 may
include other user equipments, which are not using D2D communication.
25 [0044] In an implementation, the channel resources available in a given scheduling
interval may be allotted by the central controller 102 to regular mobile users and D2D users.
In an example, the central controller 102 may be a base station, such as an eNodeB (eNB) in
LTE. The central controller 102 allocates channel resources to the user equipments in a cell
controlled by it. Further, the user equipments, i.e., the transmitters 104 and the receivers 106,
30 may register with the central controller 102 to operate in D2D mode. The central controller
102, among other things, may include a processor 110, interfaces, memory, modules and
data.
13
[0045] The processor 110 may be implemented as one or more microprocessors,
microcomputers, microcontrollers, digital signal processors, central processing units, logic
circuitries, and/or any devices that manipulate signals based on operational instructions.
Among other capabilities, the processor(s) is configured to fetch and execute computerreadable
instructions stored in the memory5 .
[0046] The functions of the various elements shown in the figure, including any
functional blocks labeled as “processor(s)”, may be provided through the use of dedicated
hardware as well as hardware capable of executing software in association with appropriate
software. When provided by a processor, the functions may be provided by a single dedicated
10 processor, by a single shared processor, or by a plurality of individual processors, some of
which may be shared. Moreover, explicit use of the term “processor” should not be construed
to refer exclusively to hardware capable of executing software, and may implicitly include,
without limitation, digital signal processor (DSP) hardware, network processor, application
specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory
15 (ROM) for storing software, random access memory (RAM), non-volatile storage. Other
hardware, conventional and/or custom, may also be included.
[0047] The interface(s) may include a variety of software and hardware interfaces that
allow the central controller 102 to interact with the transmitters 104, the receivers 106, and
other communication and computing devices, such as web servers and external repositories.
20 [0048] The memory may be coupled to the processor 110 and may include any
computer-readable medium known in the art including, for example, volatile memory (e.g.,
RAM), and/or non-volatile memory (e.g., EPROM, flash memory, etc.)
[0049] The modules include routines, programs, objects, components, data structures,
and the like, which perform particular tasks or implement particular abstract data types. The
25 modules further include modules that supplement applications on the central controller 102,
for example, modules of an operating system.
[0050] Further, the modules can be implemented in hardware, instructions executed
by a processing unit, or by a combination thereof. The processing unit can comprise a
computer, a processor, such as the processor 110, a state machine, a logic array or any other
30 suitable devices capable of processing instructions. The processing unit can be a general14
purpose processor which executes instructions to cause the general-purpose processor to
perform the tasks or, the processing unit can be dedicated to perform the functions.
[0051] In another aspect of the present subject matter, the modules may be machinereadable
instructions (software) which, when executed by a processor/processing unit,
perform any of the described functionalities. The machine-readable instructions may 5 be
stored on an electronic memory device, hard disk, optical disk or other machine-readable
storage medium or non-transitory medium. In one implementation, the machine-readable
instructions can be also be downloaded to the storage medium via a network connection. The
data serves, amongst other things, as a repository for storing data that may be fetched,
10 processed, received, or generated by one or more of the modules.
[0052] In an implementation, the modules of the central controller 102 include a
channel resource allocation module 112. The channel resource allocation module 112 may
assign a unique id, such as a radio network temporary identity (RNTI) to each of the user
equipments registered for D2D communications and a common id, say D2D_RNTI,
15 indicating D2D communication mode. The central controller 102 may communicate
D2D_RNTI to all the user equipments and multicast a message by addressing the user
equipments with D2D_RNTI. Alternatively, the cellular controller 102 may individually
broadcast a message to each of the user equipments.
[0053] Further, the channel resource allocation module 112 may allocate the channel
20 resources between the regular users and D2D users, based on allocation criteria. In an
example, the allocation criteria may indicate that regular mobile traffic is to be given priority
over D2D traffic in some or all the scheduling intervals. In other examples, the channel
resources may be shared in predetermined ratio among regular mobile users and D2D users.
In yet another example, in some of the scheduling intervals regular mobile traffic may be
25 given priority, while in some others D2D traffic may be give be priority, and in few others
the channel resources may be shared in a predetermined ratio. Thus, based on the allocation
criteria, in a given scheduling interval, the channel resources may be divided between regular
mobile users and the D2D users. It will be understood that, based on the allocation criteria
being implemented, the channel resources allocated for D2D communication may change
30 every scheduling interval. Therefore, the channel resource allocation module may allocate
channel resources for D2D communications in the given cell in each scheduling interval,
15
based on the allocation criteria. Also, the channel resources allocated for D2D
communications may not be contiguous and may be spread out in frequency.
[0054] Additionally, the channel resource allocation module 112 may reserve a
channel resource, such as a control channel for sharing acknowledgments. It will be
understood that the control channel will be a synchronized channel. Also, the allocation of th5 e
channel resources may be performed in advance to provide the transmitters 104 with
sufficient time to construct data packets. For example, allocation of channel resources may be
performed a predetermined number scheduling intervals in advance.
[0055] In an example, based on the allocation, a scheduling grant may be provided to
10 the user equipments that have registered for D2D communications. For example, if in a
scheduling interval, all the channel resources are allocated to the regular mobile users and
there are no unused channel resources, it may be determined that no channel resources are
available for D2D communication in the scheduling interval. In such a case, no scheduling
grant may be provided and the channel resource allocation module 112 may perform the same
15 check in next scheduling interval. Alternatively, in case it is determined that the channel
resources are available, the scheduling grant indicating the same and including information
pertaining to available channel resources, such as what are the resources that are available
and which channel resource is reserved as control channel, may be provided to the user
equipments that have registered for D2D communications. The user equipments that have
20 registered for D2D communication mode may be identified by their corresponding RNTI.
Further, the scheduling grant may be provided as a unicast or a multi-case message.
[0056] Further, it will be understood that a scheduling interval may be a
predetermined time-interval based on a type of cellular communication network in which the
D2D communication is being implemented. For example, the scheduling interval may be 1
25 millisecond (ms) in LTE and may be 2 ms in WCDMA. Additionally, the channel resource
that is to be considered for allocation may also be based on the type of cellular
communication network. For example, the smallest allocable channel resource in LTE is a
Physical Resource Block (PRB). One PRB comprises 12 subcarriers, where each subcarrier
has width of 15 kHz, hence a PRB has a width of 180 kHz. Further, a PRB is spread over a
30 single subframe, which 1 ms long, and each subframe comprises 14 Orthogonal Frequency
Division Multiple Access (OFDMA) symbols.
16
[0057] Again referring to LTE, the central controller 102, which may be eNB, may
use existing Physical Downlink Control Channel (PDCCH) to communicate the assignment
of the channel resources, which are PRBs, to D2D users. As mentioned before, the central
controller 102 may address all the D2D users using D2D_RNTI. Further, D2D
communications may take place in uplink spectrum as generally it is less used 5 ed compared to
the downlink spectrum and therefore may be efficiently used for D2D communication.
[0058] Further, as mentioned before, the allocation of the channel resources may be
done in advance. In LTE the assignment of PRBs on PDCCH channel for the uplink channel
may be announced three subframes, i.e., three scheduling intervals in advance. This gives
10 D2D user equipments sufficient time to construct their data packet according to the number
of PRBs that are available D2D communication.
[0059] In an example, any transmitter 104 that wants to make a transmission, first
checks if the channel resources are free for transmitting data in the scheduling interval, based
on the scheduling grant and a resource availability sensing technique. For the purpose, the
15 transmitter 104 may determine whether any channel resources are allocated for D2D
communications, if the scheduling grant is received. Further, if it is determined that the
channel resources are allocated for D2D communication in the scheduling interval, it may be
determined whether the channel resources are free for transmitting data using the resource
availability sensing technique, such as physical carrier sensing technique and virtual carrier
20 sensing technique. The resource availability sensing technique may be performed throughout
the scheduling interval.
[0060] The transmitter 104 may continue to determine the availability of the channel
resources, till the channels resources become available. Once it is determined that the channel
resources are now available, the transmitter 104 may initiate a back-off procedure, which
25 may be implemented to share the channel resources equitably among all the competing
transmitters 104. Further, based on the back-off procedure, the transmitter 104 may prepare
and transmit a data packet for transmission to the receiver 106. The back-off procedure,
preparation, and transmission of the data packet has been explained in detail with reference to
description of Fig. 2. The data packet may include a preamble followed by a header and the
30 data to be transmitted. The header includes information, such as size of data packet, data
transmission rate per channel resource, and addresses of source and destination.
17
[0061] Based on the header of the data packet being transmitted, a corresponding
receiver 106 identifies the data packet as being meant for it and decodes the same. Further,
the receiver 106 may determine whether the decoding was successful or not and may send an
acknowledgement message, which may indicate a decoding status. The decoding status may
indicate whether the data packet was decoded successfully or not. The receiver 106 may 5 send
the acknowledgement message on the control channel resource, reserved by the central
controller 102 for sharing acknowledgements.
[0062] Fig. 2 illustrates various components of the transmitter 104 and the receiver
106 for D2D communication in the cellular communication network, according to an
10 embodiment of the present subject matter. Similar to central controller 102, the transmitter
104 and the receiver 106 may respectively include processor(s) 202-1 and 202-2, interface(s)
204-1 and 204-2, memory 206-1 and 206-2, modules 208-1 and 208-2, and data 210-1 and
210-2.,
[0063] The processors 202-1 and 202-2 may be similar to the processor 110. The
15 interface(s) 204-1 and 204-2 may include a variety of software and hardware interfaces that
allow the transmitters 104 and the receivers 106 to interact with each other, the central
controller 102, and other computing and communication devices. Further, the memory 206-1
and 206-2 may be coupled to the processor 202-1 and 202-2 respectively and may include
any computer-readable medium known in the art including, for example, volatile memory
20 (e.g., RAM), and/or non-volatile memory (e.g., EPROM, flash memory, etc.)
[0064] Further, the module 208-1 and 208-2 may include routines, programs, objects,
components, data structures, and the like, which perform particular tasks or implement
particular abstract data types. The modules 208-1 and 208-2 can be implemented in hardware,
instructions executed by a processing unit, or by a combination thereof. The processing unit
25 can comprise a computer, a processor, such as the processor 202-1 and 202-2, a state
machine, a logic array or any other suitable devices capable of processing instructions. The
processing unit can be a general-purpose processor which executes instructions to cause the
general-purpose processor to perform the tasks or, the processing unit can be dedicated to
perform the functions.
30 [0065] In another aspect of the present subject matter, the modules 208-1 and 208-2
may be machine-readable instructions (software) which, when executed by a
18
processor/processing unit, perform any of the described functionalities. The machinereadable
instructions may be stored on an electronic memory device, hard disk, optical disk
or other machine-readable storage medium or non-transitory medium. In one implementation,
the machine-readable instructions can be also be downloaded to the storage medium via a
network connecti5 on.
[0066] In an implementation, the modules 208-1 of the transmitter 104 may include a
resource availability determination module 212, a transmission module 214, and other
modules 216-1. Further, the module 208-2 may include a data retrieval module 218 and other
modules 216-2. The other modules 216-1 and 216-2 supplement applications on the
10 transmitter 104 and receiver 106 respectively, for example, modules of an operating system.
[0067] Referring to data 210-1 and 210-2, it may be understood that data 210-1 and
210-2 serve, amongst other things, as a repository for storing data that may be fetched,
processed, received, or generated by one or more of the modules 208-1 and 208-2.
[0068] As mentioned before, the central controller 102 may allocate channel
15 resources for D2D communication in a scheduling interval and may accordingly provide a
scheduling grant to the transmitter 104. In an implementation, the resource availability
determination module 212 may receive scheduling grant and determine whether any channel
resources are free for data transmission. For example, based on receipt of the scheduling
grant, the resource availability determination module 212 may determine whether any
20 channel resources have been allotted for the D2D communication. Upon determining that the
channel resources are allotted for the D2D communication, it may be ascertained using the
resource availability sensing technique whether the allocated channel resources are free for
transmission or not. The resource availability sensing technique may be understood as a
technique that involves carrier sensing of a medium, by a node prior to transmission, to
25 determine if any other node is transmitting using the medium.
[0069] For example, the resource availability sensing technique may be a physical
carrier sensing technique used in CSMA/CA. Accordingly, the resource availability
determination module 212 may perform out carrier sensing on the channel resources that are
allotted for D2D communications in the scheduling interval. For instance, the resource
30 availability determination module 212 may measure energy in a given set of channel
resources to ascertain if some other transmitter is making a transmission on the same set of
19
channel resources. If the channel resources for D2D communications are not free in the
current symbol of the scheduling interval, then the resource availability determination module
212 may check again in the next symbol in the same scheduling interval and may repeat the
procedure till the channel resources becomes free. Further, a bandwidth over which the
transmitter 104 does carrier sensing may vary in each scheduling interval as the number 5 er of
channel resources allocated for D2D communications may not be constant. In order to
improve robustness of the resource availability sensing technique, carrier sensing may be
performed over multiple symbols to verify the presence of a signal.
[0070] In another example, the resource availability sensing technique may be a
10 virtual carrier sensing technique. Similar to physical carrier sensing technique, the virtual
carrier sensing technique may be performed throughout the scheduling interval. In said
technique, the resource availability determination module 212 may decode a header of a data
packet being transmitted. Upon decoding, the size of the data packet and a data transmission
rate per channel resource may be determined. Based on the size of the packet and the
15 transmission rate, the resource availability determination module 212 may compute the
duration of transmission of the data packet and check if all of the data packet will be
completely transmitted in the current scheduling interval or not.
[0071] Further, the resource availability determination module 212 may determine
whether the transmission will be completed in the current scheduling interval or not by
20 computing the bandwidth allocated to D2D communication in the current scheduling interval,
channel resources available from amongst the allocated bandwidth, and by accounting for the
bits that were transmitted in the previous scheduling interval, in case transmission span
multiple scheduling intervals. It will be understood that if more channel resources are
available, then the number of symbols required to complete the transmission, i.e., duration of
25 transmission appropriately scales down. Additionally, it may be assumed that the data
transmission rate per channel resource remains constant throughout the duration of the data
packet’s transmission.
[0072] In case it is determined that transmission of the data packet will not be over in
the current scheduling interval, the resource availability determination module 212 may set a
30 flag, say, network allocation vector (NAV) to indicate that no channel resources are available
20
in the current scheduling interval. Further, in such cases, the same check may be performed in
a subsequent scheduling intervals, till the channel resources become available.
[0073] However, in case it is determined that the allocated channel resources will
become available in the current scheduling interval, the resource availability determination
module 212 may set the flag to indicate that the channel resources are available after th5 e
completion of transmission of the data packet currently being transmitted in the scheduling
interval.
[0074] It will be appreciated that in the present subject matter, the duration of the
transmission may be computed, in each scheduling interval, based on the header of the data
10 packet being transmitted and number channel resources available in the scheduling interval,
instead of using RTS or CTS as is done in traditional D2D systems. Such a provision not only
aids in efficient utilization of the channel resources but also addresses the issue of fluctuating
bandwidth that is available for D2D communications, as the transmitter 104 determines the
availability of channel resources in each scheduling interval and transmits only when the
15 channel resources become available.
[0075] Further, the resource availability determination module 212 may provide a
resource availability indication to the transmission module 214. The resource availability
indication may indicate whether the channel resources are available or not. The transmission
module 214 may initiate the back-off procedure, when the channel resources are available.
20 The back-off procedure may involve identification of a predetermined width of a contention
window, CW, for each of a first transmission and a subsequent retransmission of the data
packet. For example, the contention window for the first transmission may have a first
predetermined width, say, CWmin. For every subsequent retransmission, the width of the
contention window may be twice of the width of a previous contention window. Further, a
25 threshold width value, CWmax, of the contention window may also be determined. CWmin and
, CWmax may be predefined constants that are selected depending on the traffic in the network
and the data rate requirements of the D2D links. In an example, the threshold width value and
the first predetermined width may be chosen by the central controller 102 and communicated
to the transmitter 104.
30 [0076] Upon identifying the predetermined width, the transmission module 214, may
determine a back-off time counter in a predetermined range, say in a range of 0 and the
21
predetermined width of the contention window, i.e., [0, CW]. Further, the transmission
module 214 may ascertain whether the current symbol is available for transmission, based on
the channel resource availability indication provided by the resource availability
determination module 212. It will be understood that in parallel to the back-off procedure, the
resource availability determination module 212 continues to check the availability 5 of the
channel resources for next symbol or next scheduling interval.
[0077] Based on the channel resource availability indication, the transmission module
214 may periodically decrement the back-off time counter for each available symbol in the
current scheduling interval, the available symbol being a symbol, which is available for
10 transmission. In case it is determined that the channel resources are busy in the current
symbol, the transmission module 214 may freeze or suspend the back-off time counter till a
next available symbol is detected. It will be appreciated that based on available symbols in a
scheduling interval and the value of back-off time counter, the back-off procedure may span
over multiple scheduling intervals.
15 [0078] Further, when the transmission module 214 determines that the back-off time
counter has decremented to one or below one, it may initiate data packet preparation process.
The transmission module 214 may construct the data packet based on a number of allotted
channel resources for the current scheduling interval. In an example, the transmission module
214 may encode the data packet with modulation and coding scheme (MCS). Further,
20 transmission of the data packet may span over multiple scheduling intervals based on the size
of data to be transmitted and number of available resources in the current scheduling interval.
In case the transmitter 104 is not able to send the data packet in the current scheduling
interval, the data packet may be sent in a subsequent scheduling interval based on availability
of channel resources in the subsequent scheduling interval.
25 [0079] The data packet may comprise multiple data blocks, where a data block sent in
one scheduling interval may have a different size as compared to a data block sent in another
scheduling interval, based on the size of the data to be transmitted and the available channel
resources in corresponding scheduling interval. Accordingly, the transmission module 214
may reset the size of data blocks based on the availability of the channel resources in the next
30 scheduling interval.
22
[0080] Each data packet may include a preamble followed a header and one or more
data blocks. The preamble helps the receiver 106 and other nodes to synchronize with the
transmitter’s clock. The preamble may occupy one or more symbols depending on the desired
robustness and other details, such as bandwidth allocated for D2D communication. In an
example, the preamble may scale in frequency, i.e., bandwidth5 .
[0081] For example, in LTE, reference sequences defined in LTE can be used as the
preamble. The reference sequences are used to construct the sounding reference signal (SRS)
among others. Further, the reference sequences for longer lengths may be modified Zadoff-
Chu sequences. Each channel resource or, to say, PRB in LTE contains 12 subcarriers and the
10 length of a reference sequence is a multiple of 12, starting from a minimum length of 24.
Hence if one symbol is allocated for sending the preamble, then at least two PRBs may be
allocated for D2D communications in every scheduling interval or subframe.
[0082] In addition to preamble, the data packet may include the header. The header
instead of including overall rate of the data packet, as in traditional D2D systems, includes
15 details, such as size of the data packet, which may be in bytes, data transmission rate per
channel resource, the MCS, and source and destination addresses. Since the number of
channel resources can change every scheduling interval, the transmission module 214
specifies the data transmission rate per channel resource to enable other transmitters 104 to
compute the overall rate of the data packet in every scheduling interval.
20 [0083] Upon constructing the data packet, the transmission module 114 may transmit
the data packet over the available channel resources and release the channel resources so that
they may now be used by other transmitter 104. Based on the header of the data packet, the
data retrieval module 218 may determine whether the receiver 106 is the intended recipient.
For example, the data retrieval module 218 may obtain the destination address from the
25 header to determine if the receiver 106 is the intended recipient. On determining the receiver
106 is the intended recipient, the data retrieval module 218 may decode the data packet,
based on the MCS indicated by the header. Upon decoding the data packet, the data retrieval
module 218 may send an acknowledgement message indicating whether the data packet has
been successfully decoded or not. For example, if the decoding is successful, the data
30 retrieval module may send an ACK, else it may send a NACK. Further acknowledgement
message may be sent over the control channel reserved by the central controller 102.
23
[0084] The acknowledgement message may be received by the transmission module
214 of the transmitter 104 to perform a further action, based on the back-off procedure. In an
example, the transmission module 214 may ascertain whether the data transmission was
successful, based on the acknowledgement message received from the receiving node 106. In
case it is ascertained that the data transmission is successful, the transmitter 104 ma5 y
determine the availability of the channel resources, in case another data packet is to be sent.
However, if it is ascertained that the data transmission was unsuccessful, the transmission
module 214 may determine whether the width of the contention window is greater than a
threshold width, CWmax. For example, if it is the first transmission, the width of the
10 contention window may be of the first predetermined width, CWmin, and accordingly it may
be determined that the width of the contention window is not greater than the threshold width.
When it is determined that the width of the contention window is not greater then the
threshold width, the transmission module 214 may retransmit the data packet based on the
availability of channel resources as explained before.
15 [0085] However, if even after retransmission, the data transmission fails, the
transmission module 214 may again determine whether the width of the contention window is
greater than the threshold width. As mentioned earlier, if the data packet is retransmitted, the
width of the contention window may be twice the width of the previous contention window
and therefore, with every retransmission of the data packet, the width of content window may
20 increase.
[0086] In case, it is determined that the width of the contention window is greater
than the threshold width, the transmission module 214 may drop the data packet. In other
words, the data packet may not be retransmitted.
[0087] Fig. 3 represents a timing diagram 300 indicating procedures of D2D
25 communication in a cellular communication network, in accordance with an embodiment of
the present subject matter. In many cases, multiple network entities besides those shown may
lie between the entities, including switching stations, although these have been omitted for
clarity. Similarly, various acknowledgement and confirmation network responses may also be
omitted for clarity. Although the description of Fig.3 has been made in considerable detail
30 with respect to an LTE network, it will be understood that the procedures of allocating
24
channel resources for D2D communication may implemented for other networks as well,
albeit with few modifications.
[0088] For the sake of explanation, the timing diagram 300 has been explained
considering that a transmitter, say, the transmitter 104-1 is transmitting data over the channel
resources allocated for D2D communications to a receiver, say, the receiver 5 er 104-1 and
another transmitters, say, the other transmitter 104-3, is contending for the channel resources.
[0089] As indicated, the transmitter 104-1 may transmit a data packet 302 with a
preamble and a header 304 to the receiver 106-1. As mentioned earlier, the preamble may aid
in time synchronization and the header may include transmission information, such as size of
10 the data packet, data transmission rate per channel resource, source and destination addresses,
and MCS. Further, based on size of data to be transmitted and available channel resources,
the data packet may be sent over multiple scheduling intervals. Further, the receiver 106-1 on
successfully receiving and decoding the data packet 302 may send an acknowledgement
message, such as an ACK 306. The acknowledgement message may be sent over a separate
15 control channel. In an example, if the receiver 106-1 sends a NACK, then the transmitter 104-
1 may resend the data packet 302, based on the availability of the channel resources. In other
words, the transmitter 104-1 may contest with the transmitter 104-3 for the channel resources
to retransmit the data packet.
[0090] While the data is being transmitted by the transmitter 104-1, the other
20 transmitter 104-3 may also have to transmit data. Prior to transmitting data, the other
transmitter 104-3 may check for the availability of the channel resources. Accordingly, the
other transmitter 104-3 may determine whether any channel resources are allocated for D2D
communication and if yes, using resource availability sensing technique, it may be
determined if the channel resources are free. For example, the other transmitter 104-3 may
25 overhear the data packet 302 being transmitted and may decode the preamble and header to
determine that some other transmitter is currently using the channel resources. Accordingly,
the other transmitter 104-3 may set a Flag 308, such as NAV to indicate that the channel
resources are not available in current scheduling interval.
[0091] The other transmitter 104-3 periodically checks for availability of the channel
30 resources, and when it is determined that the channel resources are available, the other
transmitter 104-3 may initiate a back-off procedure, indicated as back-off 310 in Fig. 3.
25
Accordingly, based on the availability of channel resources in each of subsequent symbols
312, a back-off time counter may be decremented by one. As the back-off counter is
decremented to one or below, the other transmitter 104-3 transmits another data packet 314
with a preamble and header 316.
[0092] Fig. 4 illustrates a method 400 for channel resource allocation 5 n for D2D
communication in a cellular communication network, and Fig. 5 illustrates a method for data
transmission in D2D communication mode in the cellular communication network according
to an embodiment of the present subject matter. The order in which the methods is described
is not intended to be construed as a limitation, and any number of the described methods
10 blocks can be combined in any order to implement the methods or any alternative methods.
Additionally, individual blocks may be deleted from the methods without departing from the
spirit and scope of the subject matter described herein. Furthermore, the methods can be
implemented in any suitable hardware, software, firmware, or combination thereof.
[0093] The methods may be described in the general context of computer executable
15 instructions. Generally, computer executable instructions can include routines, programs,
objects, components, data structures, procedures, modules, functions, etc., that perform
particular functions or implement particular abstract data types. The methods may also be
practiced in a distributed computing environment where functions are performed by remote
processing devices that are linked through a communications network. In a distributed
20 computing environment, computer executable instructions may be located in both local and
remote computer storage media, including memory storage devices.
[0094] A person skilled in the art will readily recognize that steps of the methods can
be performed by programmed computers. Herein, some embodiments are also intended to
cover program storage devices or computer readable medium, for example, digital data
25 storage media, which are machine or computer readable and encode machine-executable or
computer-executable programs of instructions, where said instructions perform some or all of
the steps of the described methods. The program storage devices may be, for example, digital
memories, magnetic storage media, such as a magnetic disks and magnetic tapes, hard drives,
or optically readable digital data storage media. The embodiments are also intended to cover
30 both communication network and communication devices to perform said steps of the
methods.
26
[0095] Referring to Fig. 4, in an example the method 400 may be performed by the
channel resource allocation module 112 of the central controller 102, such as a base station.
[0096] At block 402, channel resources in a scheduling interval may be allocated to
regular mobile users, based on allocation criteria. The allocation criteria may indicate rules
on the basis of which the channel resources are to be divided between regular mobile 5 users
and D2D users.
[0097] At block 404, it is ascertained whether any channel resources are available for
the D2D users, based on the allocation criteria and the allocation of the resources to the
regular mobile users. In case it is ascertained that no channel resources are available, the
10 method 400 branches back to (‘No’ branch) block 402, where channel resources are allocated
in next scheduling interval.
[0098] In an example, based on the allocation criteria and upon allocating channel
resources to the regular mobile users, it may be ascertained that there are unused channel
resources, and the unused channel resources may be allocated to the D2D users. Further, in
15 case it is determined that the channel resources are allocated to the D2D users, the method
400 may proceed to (‘Yes’ branch) block 406.
[0099] At block 406, from the allocated channel resources, a channel resource may
reserved for sharing acknowledgements. The channel resource may function as a control
channel. Further, the control channel may be a synchronous channel and may occupy a
20 smaller bandwidth as compared to a regular data channel.
[00100] At block 408, a scheduling grant is provided to various nodes, such as
transmitters 104, in a cell controlled by a central controller, such as the central controller 102.
The scheduling grant may be indicative of availability of the channel resources for D2D
communication in the scheduling interval and may include information pertaining to the
25 allocated channel resources, such as what channel resources are allocated for D2D
communication and which channel resource is reserved for sharing acknowledgements. In an
example, if it is determined that the channel resources are available, the scheduling grant may
indicate the same and may also provide information pertaining to available channel resources
for data transmission and the control channel.
27
[00101] Referring to Fig. 5, the method 500 may be performed by a transmitter, such
as the transmitter 104, in a cell controlled by a central controller, such as the central
controller 102.
[00102] At block 502, a scheduling grant indicative of availability of channel resources
in a scheduling interval is received. In an example, the scheduling grant may 5 be provided by a
central controller, such as the central controller 502, a predetermined scheduling intervals in
advance. In an example, the scheduling grant may be received by the resource availability
determination module 212.
[00103] At block 504, it may be ascertained whether any channel resources are
10 available for data transmission in a scheduling interval. The availability of channel resources
may be determined based on the scheduling grant received for the scheduling interval and
using a resource availability determination technique, such as physical carrier sensing and
virtual carrier sensing. In an example, resource availability determination module 212 checks
for the availability of channel resources. In case it is ascertained that the channel resources
15 are not available in the scheduling interval, the availability of the channel resources may be
checked periodically till the channel resources become available.
[00104] However, in case it is ascertained that the channel resources are available in
the scheduling interval, the method 500 may proceed to block (‘Yes’ branch) block 506. At
block 506, upon ascertaining the availability of channel resources, a back-off procedure may
20 be initiated. As part of the back-off procedure, back-off time counter may be triggered. In an
example, the transmission module 214 may initiate the back-off procedure.
[00105] At block 508, it is ascertained whether the back-off time counter has
decremented to a threshold counter value. For instance, the threshold counter value may be
one. In an example, the transmission module 214 checks for the availability of the channel
25 resources in each symbol of a scheduling interval and may accordingly decrement the backoff
time counter. In case it is determined that the back-off time counter has not decremented
to the threshold counter value, the method 500 may branch back to block (‘No’ branch) to
block 508.
28
[00106] However, in case it is determined that the back-off time counter has
decremented to the threshold counter value, the method 500 may proceed to block (‘Yes’
branch) to block 510.
[00107] At block 510, a data packet is transmitted to a receiver, when the back-off time
counter decrements to the threshold counter value. The data packet may include a preamble, 5 , a
header, and one or more data blocks. Further, based on size of data to be transmitted and
available channel resources in a scheduling interval, the data packet may be transmitted over
one or more scheduling intervals. In an example, the transmission module 214 transmits the
data packet over the channel resources.
10 [00108] At block 512, it may be ascertained, whether the data packet was transmitted
successfully. In an example, successful transmission of the data packet may be ascertained
based on an acknowledgement provided by the receiver. If it is ascertained that the data
packet was transmitted successfully, the method 500 branches to (‘Yes’ branch) block 502.
[00109] However, if at block 512, it is ascertained that the data transmission was not
15 successful, as part of the back-off procedure, the method 500 proceeds to (‘No’ branch) block
514.
[00110] At block 514, it is determined whether width of a content window for the
transmission of the data packet is greater than a predetermined maximum width. If it is
determined that the width of the contention window is not greater than the predetermined
20 maximum width, the method branches (‘No’ branch) to block 502 and the data packet is
transmitted again, based on the availability of channel resources.
[00111] However, if at block 514, it is determined that contention window is greater
than the predetermined width, the method branches (‘Yes’ branch) to block 516. At block
516, the data packet is dropped and is not transmitted again.
25 [00112] Although embodiments for D2D communication in cellular communication
networks have been described in a language specific to structural features or method(s), it is
to be understood that the invention is not necessarily limited to the specific features or
method(s) described. Rather, the specific features and methods are disclosed as embodiments
for D2D communication in cellular communication networks.
30
29
I/We claim:
1. A central controller (102) for allocating channel resources for device to device (D2D)
communication in a cellular communication network, the central controller (102)
comprising:
5 a processor (110); and
a channel resource allocation module (112) coupled to the processor (110) to:
allocate channel resources to D2D users and regular mobile users in a
scheduling interval, based on allocation criteria; and
provide, based on the allocation, a scheduling grant to one or more
10 transmitters (104) in a cell (100) controlled by the central controller (102), wherein
the scheduling grant is indicative of availability of the channel resources for the
D2D communication in the scheduling interval.
2. A transmitter (104) for transmitting data in D2D communication mode in a cellular
communication network, the transmitter (104) comprising:
15 a processor (202-1);
a resource availability determination module (212) coupled to the processor (202-
1) to:
ascertain whether channel resources for D2D communication in a
scheduling interval are available, based on a resource availability sensing technique
20 and a scheduling grant; and
a transmission module (214) coupled to the processor (202-1) to:
determine a number of channel resources available for transmission in the
scheduling interval;
construct a data packet, based on the number of channel resources, wherein
25 the data packet comprises a header indicative of the size of the data packet and a
data transmission rate per channel resource; and
30
transmit the data packet over one or more scheduling intervals, based on the
number of channel resources and a size of the data to be transmitted.
3. The transmitter (104) as claimed in claim 2, wherein the resource availability
determination module (212):
ascertains whether the data can be completely transmitted in the scheduli5 ng
interval, based on the number of available channel resources and the size of the
data to be transmitted;
determines, when the data packet can not be completely transmitted, a
subsequent number of channel resources available for transmission in a subsequent
10 scheduling interval; and
constructs a first data block to be transmitted in the scheduling interval
based on the number of available channel resources, and a subsequent data block to
be transmitted in the subsequent scheduling interval, based on the subsequent
number of available channel resources, wherein the first data block and the
15 subsequent data block form the data packet.
4. The transmitter (104) as claimed in claim 2, wherein the resource availability
determination module (212):
decodes the header of another data packet being transmitted over channel
resources allotted for D2D communication;
20 ascertains, based on decoding, whether transmission of the another data packet
will be completed in the scheduling interval; and
sets a flag to indicate that the channel resources will be available in the current
scheduling interval, when it is ascertained that the transmission of the another data packet
will be completed in the current scheduling interval.
25 5. The transmitter (104) as claimed in claim 4, wherein the resource availability
determination module (212):
sets, based on the ascertainment, the flag to indicate that the channel resources
will be not be available in the current scheduling interval; and
31
ascertains, in a next scheduling interval, whether transmission of the another data
packet will be completed in the next scheduling interval.
6. The transmitter (104) as claimed in claim 2, wherein the transmission module (214):
initiates a back-off procedure, when the channel resources are available, and
wherein the data packet is transmitted based on the 5 back-off procedure.
7. A receiver (106) in D2D communication with a transmitter (104) in a cellular
communication network, the receiver (106) comprising:
a processor (202-2); and
a data retrieval module (218) coupled to the processor to:
10 decode a received data packet based on a header of the received data
packet; and
transmit an acknowledgement, based on decoding, on a control channel
resource to a transmitter (104), wherein the control channel resource is reserved
by a central controller (102) for transmitting acknowledgements.
15 8. A method for allocating channel resources for D2D communication in a cellular
communication network, the method comprising:
allocating channel resources to D2D users and regular mobile users in a
scheduling interval, based on allocation criteria; and
providing based on the allocation, a scheduling grant to one or more
20 transmitters (104) in a cell (100) controlled by a central controller (102), wherein
the scheduling grant is indicative of availability of the channel resources for the
D2D communication in the scheduling interval.
9. The method as claimed in claim 8, wherein the method further comprises reserving a
channel resource from the allocated channel resources for sharing acknowledgements.
25 10. A method for transmitting data for D2D communication in a cellular communication
network, the method comprising:
32
ascertaining whether channel resources for the D2D communication in a
scheduling interval are available, based on a resource availability sensing technique
and a received scheduling grant;
determining, based on the ascertaining, a number of channel resources
available for transmission in the scheduling interval5 ;
constructing a data packet, based on the number of channel resources,
wherein the data packet comprises a header indicative of the size of the data packet
and a data transmission rate per channel resource; and
transmitting the data packet over one or more scheduling intervals, based
10 on the number of channel resources and a size of the data to be transmitted
11. The method as claimed in claim 10, wherein the ascertaining further comprises:
decoding the header of another data packet being transmitted over channel
resources allotted for D2D communication;
ascertaining, based on decoding, whether transmission of the another data packet
15 will be completed in the scheduling interval; and
setting a flag to indicate that the channel resources will be available in the current
scheduling interval, when it is ascertained that the transmission of the another data packet
will be completed in the current scheduling interval.
12. The method as claimed in claim 11, wherein the method further comprises:
20 setting the flag to indicate that the channel resources will be not be available in the
current scheduling interval, when it is ascertained that the transmission of the another data
packet will not be completed in the scheduling interval; and
ascertaining, in a next scheduling interval, whether transmission of the another
data packet will be completed in the next scheduling interval.
25 13. The method as claimed in claim 10, wherein the method further comprises:
initiating a back-off procedure, when the channel resources are available, wherein
the data packet is transmitted based on execution of the back-off procedure.
33
14. A method for receiving data for D2D communication in a cellular communication
network, the method comprising:
decoding a received data packet based on a header of the received data packet; and
transmitting an acknowledgement, based on decoding, on a control channel
resource to a transmitter (104), wherein the control channel resource is reserved by 5 a
central controller (102) for transmitting acknowledgements.
15. A non-transitory computer-readable medium having embodied thereon a computer
program for executing a method for D2D communication in a cellular communication
network, the method comprising:
10 ascertaining whether channel resources for the D2D communication in a
scheduling interval are available, based on a resource availability sensing technique
and a received scheduling grant;
determining a number of channel resources available for transmission in the
scheduling interval;
15 constructing a data packet, based on the number of channel resources,
wherein the data packet comprises a header indicative of the size of the data packet
and a data transmission rate per channel resource; and
transmitting the data packet over one or more scheduling intervals, based
on the number of channel resources and a size of data to be transmitted.

CLIAMS:
1. A central controller (102) for allocating channel resources for device to device (D2D) communication in a cellular communication network, the central controller (102) comprising:
a processor (110); and
a channel resource allocation module (112) coupled to the processor (110) to:
allocate channel resources to D2D users and regular mobile users in a scheduling interval, based on allocation criteria; and
provide, based on the allocation, a scheduling grant to one or more transmitters (104) in a cell (100) controlled by the central controller (102), wherein the scheduling grant is indicative of availability of the channel resources for the D2D communication in the scheduling interval.
2. A transmitter (104) for transmitting data in D2D communication mode in a cellular communication network, the transmitter (104) comprising:
a processor (202-1);
a resource availability determination module (212) coupled to the processor (202-1) to:
ascertain whether channel resources for D2D communication in a scheduling interval are available, based on a resource availability sensing technique and a scheduling grant; and
a transmission module (214) coupled to the processor (202-1) to:
determine a number of channel resources available for transmission in the scheduling interval;
construct a data packet, based on the number of channel resources, wherein the data packet comprises a header indicative of the size of the data packet and a data transmission rate per channel resource; and
transmit the data packet over one or more scheduling intervals, based on the number of channel resources and a size of the data to be transmitted.
3. The transmitter (104) as claimed in claim 2, wherein the resource availability determination module (212):
ascertains whether the data can be completely transmitted in the scheduling interval, based on the number of available channel resources and the size of the data to be transmitted;
determines, when the data packet can not be completely transmitted, a subsequent number of channel resources available for transmission in a subsequent scheduling interval; and
constructs a first data block to be transmitted in the scheduling interval based on the number of available channel resources, and a subsequent data block to be transmitted in the subsequent scheduling interval, based on the subsequent number of available channel resources, wherein the first data block and the subsequent data block form the data packet.
4. The transmitter (104) as claimed in claim 2, wherein the resource availability determination module (212):
decodes the header of another data packet being transmitted over channel resources allotted for D2D communication;
ascertains, based on decoding, whether transmission of the another data packet will be completed in the scheduling interval; and
sets a flag to indicate that the channel resources will be available in the current scheduling interval, when it is ascertained that the transmission of the another data packet will be completed in the current scheduling interval.
5. The transmitter (104) as claimed in claim 4, wherein the resource availability determination module (212):
sets, based on the ascertainment, the flag to indicate that the channel resources will be not be available in the current scheduling interval; and
ascertains, in a next scheduling interval, whether transmission of the another data packet will be completed in the next scheduling interval.
6. The transmitter (104) as claimed in claim 2, wherein the transmission module (214):
initiates a back-off procedure, when the channel resources are available, and wherein the data packet is transmitted based on the back-off procedure.
7. A receiver (106) in D2D communication with a transmitter (104) in a cellular communication network, the receiver (106) comprising:
a processor (202-2); and
a data retrieval module (218) coupled to the processor to:
decode a received data packet based on a header of the received data packet; and
transmit an acknowledgement, based on decoding, on a control channel resource to a transmitter (104), wherein the control channel resource is reserved by a central controller (102) for transmitting acknowledgements.
8. A method for allocating channel resources for D2D communication in a cellular communication network, the method comprising:
allocating channel resources to D2D users and regular mobile users in a scheduling interval, based on allocation criteria; and
providing based on the allocation, a scheduling grant to one or more transmitters (104) in a cell (100) controlled by a central controller (102), wherein the scheduling grant is indicative of availability of the channel resources for the D2D communication in the scheduling interval.
9. The method as claimed in claim 8, wherein the method further comprises reserving a channel resource from the allocated channel resources for sharing acknowledgements.
10. A method for transmitting data for D2D communication in a cellular communication network, the method comprising:
ascertaining whether channel resources for the D2D communication in a scheduling interval are available, based on a resource availability sensing technique and a received scheduling grant;
determining, based on the ascertaining, a number of channel resources available for transmission in the scheduling interval;
constructing a data packet, based on the number of channel resources, wherein the data packet comprises a header indicative of the size of the data packet and a data transmission rate per channel resource; and
transmitting the data packet over one or more scheduling intervals, based on the number of channel resources and a size of the data to be transmitted
11. The method as claimed in claim 10, wherein the ascertaining further comprises:
decoding the header of another data packet being transmitted over channel resources allotted for D2D communication;
ascertaining, based on decoding, whether transmission of the another data packet will be completed in the scheduling interval; and
setting a flag to indicate that the channel resources will be available in the current scheduling interval, when it is ascertained that the transmission of the another data packet will be completed in the current scheduling interval.
12. The method as claimed in claim 11, wherein the method further comprises:
setting the flag to indicate that the channel resources will be not be available in the current scheduling interval, when it is ascertained that the transmission of the another data packet will not be completed in the scheduling interval; and
ascertaining, in a next scheduling interval, whether transmission of the another data packet will be completed in the next scheduling interval.
13. The method as claimed in claim 10, wherein the method further comprises:
initiating a back-off procedure, when the channel resources are available, wherein the data packet is transmitted based on execution of the back-off procedure.
14. A method for receiving data for D2D communication in a cellular communication network, the method comprising:
decoding a received data packet based on a header of the received data packet; and
transmitting an acknowledgement, based on decoding, on a control channel resource to a transmitter (104), wherein the control channel resource is reserved by a central controller (102) for transmitting acknowledgements.
15. A non-transitory computer-readable medium having embodied thereon a computer program for executing a method for D2D communication in a cellular communication network, the method comprising:
ascertaining whether channel resources for the D2D communication in a scheduling interval are available, based on a resource availability sensing technique and a received scheduling grant;
determining a number of channel resources available for transmission in the scheduling interval;
constructing a data packet, based on the number of channel resources, wherein the data packet comprises a header indicative of the size of the data packet and a data transmission rate per channel resource; and
transmitting the data packet over one or more scheduling intervals, based on the number of channel resources and a size of data to be transmitted.
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