DESCRIPTION
Title of Invention:
PROVIDING A BEAMFORMED PHYSICAL DOWNLINK CONTROL CHANNEL
(PDCCH) ON AN EXTENSION CARRIER OF A MOBILE COMMUNICATION SYSTEM
Technical Field:
The present invention relates to mobile communications devices and networks,
particularly but not exclusively those operating according to the 3rd Generation Partnership
Project (3GPP) standards or equivalents or derivatives thereof. The invention has particular
although not exclusive relevance to the Long Term Evolution (LTE) of UTRAN (called Evolved
Universal Terrestrial Radio Access Network (E-UTRAN)).
Background Art:
It has been decided, as part of the 3GPP standardisation process, that downlink operation
for system bandwidths beyond 20MHz will be based on the aggregation of a plurality of
component carriers at different frequencies. Such carrier aggregation can be used to support
operation in a system both with and without a contiguous spectrum (for example, a non¬
contiguous system may comprise component carriers at 800MHz, 2GHz, and 3.5GHz). Whilst a
legacy mobile device may only be able to communicate using a single, backward compatible,
component carrier, a more advanced multi-carrier capable terminal would be able to
simultaneously use the multiple component carriers.
Carrier aggregation can be particularly beneficial in a heterogeneous network (HetNet),
even when the system bandwidth is contiguous, and does not exceed 20 MHz because multiple
carriers enable interference management between different power class cells as well as open
access and closed subscriber group (CSG) cells. Long-term resource partitioning can be carried
out by exclusively dedicating carriers to a certain power class of cell (Macro/Pico/CSG).
Further, the need for interference management between different cells operating on
component carriers of the same frequency in coincident or overlapping geographic areas has led
to the development of extension carriers (which are not backwards compatible with legacy
devices). Extension carriers may be used as a tool for carrier aggregation based HetNet
operation and improved spectral efficiency. A multi-carrier capable base station is able to
operate at least one of its carriers as an extension carrier, on which a control channel (e.g. a
channel carrying resource scheduling information such as the Physical Downlink Control
Channel (PDCCH)), a Common reference Signal (CRS) (sometimes referred to as a Cell-specific
Reference Signal), and other information cannot be transmitted. More specifically, an extension
carrier may not be used for transmission of any of the following:
• a Physical Downlink Control Channel (PDCCH);
• a Physical Hybrid ARQ Indicator Channel (PHICH);
• a Physical Control Format Indicator Channel (PCFICH);
• a Physical Broadcast Channel (PBCH);
• a Primary Synchronization Signal (PSS);
• a Secondary Synchronization Signal (SSS); or
• a Common Reference Signal / Cell-specific Reference Signal (CRS).
An extension carrier therefore comprises a carrier that cannot be operated as a single
carrier (stand-alone) carrier, but must be a part of a component carrier set where at least one of
the carriers in the set is a stand-alone-capable carrier, which can be used to transmit the
scheduling information (and other control information) for the extension carrier.
Thus, when a first base station is operating a component carrier as an extension carrier,
another base station may operate a component carrier of the same frequency to transmit a control
channel, a CRS and other such information more reliably, in the same general geographic area as
the first base station, without significant interference because there is no corresponding control
channel, CRS and other such information on the extension carrier operated by the first base
station.
However, in communication systems in which extension carriers are employed, the crosscarrier
scheduling from the stand-alone (legacy) component carrier can cause an increase in
control channel (PDCCH) blocking and control channel (PDCCH) capacity can become a
limiting factor of system performance. This is because of the additional control channel
signalling required to schedule resources on multiple component carriers.
Disclosure of Invention:
The invention therefore aims to provide a mobile communication system, a mobile
communication device, a communication node and associated methods which overcomes or at
least mitigates the above issues.
According to one aspect of the present invention, there is provided communication
apparatus for communicating with a plurality of mobile communication devices in a cellular
communication system the communication apparatus comprising: means for operating at least
one communication cell; means for communicating a plurality of subframes with each of a
plurality of communication devices within the at least one cell, wherein: each sub-frame
comprises a plurality of communication resources defining a control region for communicating a
respective control channel and a plurality of communication resources defining a data region for
communicating a respective data channel; and the communicating means is operable to
communicate: a first control channel having a first reference signal pattern (which may also
referred to as a 'sequence') in a control region of a first of the subframes; and a second control
channel having a second reference signal pattern (sequence) in a control region of a second of
the subframes, wherein the second reference signal pattern (sequence) is different from the first
reference signal pattern (sequence).
The means for operating at least one communication cell may be operable to operate a
first cell using a first component carrier and a second cell using a second component carrier, and
the first subframe may be provided using the first component carrier and the second subframe
may be provided using the second component carrier.
The second component carrier may be operated as an extension carrier. The first
component carrier may be operated as a stand-alone carrier. The communicating means may be
operable to focus the second control channel spatially in a direction of a specific communication
device.
The communicating means may be operable to transmit the first control channel
omnidirectionally throughout the at least one cell.
The communication apparatus may further comprise means for determining whether a
specific communication device should receive a first control channel having the first reference
signal pattern, or a second control channel having the second reference signal pattern.
The determining means may be operable to determine whether the specific
communication device should receive the first control channel having the first reference signal
pattern, or the second control channel having the second reference signal pattern, based on a
location of the communication device.
The determining means determining means may be operable to determine whether the
specific communication device should receive the first control channel having the first reference
signal pattern, or the second control channel having the second reference signal pattern, based on
the location of the communication device relative to further communication apparatus.
The determining means may be operable to determine the location of the communication
device relative to the further communication apparatus based on a result of a measurement of a
parameter representing a distance of the communication device from the further communication
apparatus.
The parameter representing a distance of the communication device from the further
communication apparatus may comprise a reference signal received power (RSRP) of a signal
transmitted by the further communication apparatus.
The determining means may be operable to determine that the specific communication
device should receive the first control channel having the first reference signal pattern if a
predefined message has been received from the specific communication device.
The determining means may be operable to determine that the specific communication
device should receive the second control channel having the second reference signal pattern if a
further predefined message has been received from the specific communication device.
The determining means may be operable to determine whether the specific
communication device should receive a the first control channel having the first reference signal
pattern, or the second control channel having the second reference signal pattern, in dependence
on a measurement report received from the specific communication device.
The communication apparatus may comprise a plurality of distributed antennas.
The communicating means may be operable to communicate the first control channel
having a first reference signal pattern using any of the plurality of antennas.
The communicating means may be operable to communicate the second control channel
having a second reference signal pattern using a subset comprising at least one, but not all, of the
plurality of antennas.
The communicating means may be operable to communicate a control channel having a
third reference signal pattern in a third of the subframes using a subset comprising at least one,
but not all, of the plurality of antennas, wherein the third reference signal pattern may be
different from first reference signal pattern and the second reference signal pattern.
The communicating means may be operable to communicate radio frames comprising a
plurality of subfames, each subframe having a different respective subframe location, and
wherein the communicating means may be operable: to communicate the first control channel
having a first reference signal pattern in a subframe at a subframe location, within a radio frame,
selected from a first set of subframe location(s) comprising at least one subframe location; and
may be operable to communicate the second control channel having a second reference signal
pattern in a subframe at a subframe location, within a radio frame, selected from a second set of
subframe location(s) comprising at least one subframe location; wherein the first set of subframe
location(s) may not comprise the same subframe location(s) as the second set of subframe
location(s).
The first control channel having a first reference signal pattern may not be communicated
in a subframe at a subframe location of a multi-media broadcast over a single frequency network
(MBSFN) subframe and/or may not be communicated in a subframe at a subframe location of an
almost blank subframe (ABS).
The second control channel having a second reference signal pattern may be
communicated in a subframe at a subframe location of a multi-media broadcast over a single
frequency network (MBSFN). The second control channel having a second reference signal
pattern may be communicated in a subframe of an almost blank subframe (ABS).
Control information communicated using the first and/or the second may represent a
resource allocation for a communication device. Each reference signal pattern may comprise a
demodulation reference signal pattern OMRS'.
According to one aspect of the present invention, there is provided a communication
device for communicating with communication apparatus of a cellular communication system
said communication device comprising: means for registering said communication device in at
least one communication cell operated by said communication apparatus; means for receiving a
plurality of sub-frames from said communication apparatus, wherein: each sub-frame comprises
a plurality of communication resources defining a control region for communicating a respective
control channel and a plurality of communication resources defining a data region for
communicating a respective data channel; and said receiving means is operable: to receive a first
control channel having a first reference signal pattern in a control region of a first of said
subframes; and to receive a second control channel having a second reference signal pattern in a
in a control region of a second of said subframes, wherein said second reference signal pattern
may be different from said first reference signal pattern; and means for interpreting control
information communicated in said first control channel having a first reference signal pattern,
and for interpreting control information communicated in said second control channel having a
second reference signal pattern.
The receiving means may be operable to receive the first subframe on a first component
carrier of a first frequency band and the second subframe on a the second component carrier of a
second frequency band. The second component carrier may be operated as an extension carrier.
The first component carrier may be operated as a stand-alone carrier.
The receiving means may be operable to receive the second control channel in a radio
beam focussed spatially in a direction of the communication device.
The receiving means may be operable to receive the first control channel in a radio
communication transmitted omnidirectionally throughout the at least one cell.
The communication device may further comprise means for measuring a parameter
representing a distance of the communication device from further communication apparatus.
The parameter representing a distance of the communication device from the further
communication apparatus may comprise a reference signal received power (RSRP) of a signal
transmitted by the further communication apparatus.
The communication device may further comprise means for transmitting a predefined
message to the communication apparatus operating the cell in dependence on a result of the
measurement of the parameter representing a distance of the communication device from the
further communication apparatus.
The predefined message may comprise a measurement report including the result of the
measurement.
The predefined message may comprise information representing an identity of the further
communication apparatus and/or of a cell operated by the further communication apparatus.
The communication device may further comprise means for comparing the parameter
against a predetermined threshold value.
The transmitting means may be operable to transmit the predefined message if the
comparison indicates that the parameter has risen above the threshold value.
The transmitting means may be operable to transmit a further predefined message if the
comparison indicates that the parameter has fallen below the threshold value.
The receiving means may be operable to receive radio frames comprising a plurality of
subfames, each subframe having a different respective subframe location within the radio frame,
and wherein the receiving means may be operable: to receive a first control channel having a
first reference signal pattern in a subframe at a subframe location, within a radio frame, selected
from a first set of subframe location(s) comprising at least one subframe location; and may be
operable to receive a second control channel having a second reference signal pattern in a
subframe at a subframe location, within a radio frame, selected from a second set of subframe
location(s) comprising at least one subframe location; wherein the first set of subframe
location(s) may not comprise the same subframe location(s) as the second set of subframe
location(s).
The first control channel having a first reference signal pattern may not be received in a
subframe at a subframe location of a multi-media broadcast over a single frequency network
(MBSFN) and/or may not be received in a subframe at a subframe location of an almost blank
subframe (ABS). The second control channel having a second reference signal pattern may be
received in a subframe at a subframe location of a multi-media broadcast over a single frequency
network (MBSFN). The second control channel having a second reference signal pattern may be
received in a subframe of an almost blank subframe (ABS).
The control information communicated using the first and/or the second may represent a
resource allocation for the communication device.
The reference signal pattern may comprise a demodulation reference signal pattern
OMRS'.
According to one aspect of the present invention, there is provided a method, performed
by communication apparatus, of communicating with a plurality of mobile communication
devices in a cellular communication system the method comprising: operating at least one
communication cell; communicating a plurality of subframes with each of a plurality of
communication devices within the at least one cell, wherein each sub-frame comprises a plurality
of communication resources defining a control region for communicating a respective control
channel and a plurality of communication resources defining a data region for communicating a
respective data channel; communicating control information using a first control channel having
a first reference signal pattern in a control region of a first of the subframes; and communicating
control information using a second control channel having a second reference signal pattern in a
control region of a second of the subframes, wherein the second reference signal pattern is
different from the first reference signal pattern.
According to one aspect of the present invention, there is provided a method, performed
by a communication device, of communicating with communication apparatus of a cellular
communication system the method:
registering the communication device in at least one communication cell operated by the
communication apparatus;
receiving a plurality of sub-frames from the communication apparatus, wherein each subframe
comprises a plurality of communication resources defining a control region for
communicating a respective control channel and a plurality of communication resources defining
a data region for communicating a respective data channel; receiving a first control channel
having a first reference signal pattern in a control region of a first of the subframes; interpreting
control information communicated in the first control channel having a first reference signal
pattern; receiving a second control channel having a second reference signal pattern in a in a
control region of a second of the subframes, wherein the second reference signal pattern is
different from the first reference signal pattern; and interpreting control information
communicated in the second control channel having a second reference signal pattern.
According to one aspect of the present invention, there is provided a computer program
product comprising instructions operable to program a programmable processor to implement
communication apparatus or a communication device according as recited above.
According to one aspect of the present invention, there is provided communication
apparatus for communicating with a plurality of mobile communication devices in a cellular
communication system the communication apparatus comprising: means for operating at least
one communication cell; means for communicating a plurality of subframes with each of a
plurality of communication devices within the at least one cell, wherein: each sub-frame
comprises a plurality of communication resources defining a control region for communicating a
respective control channel and a plurality of communication resources defining a data region for
communicating a respective data channel; and the communicating means may be operable to
communicate: control information using a first control channel having a first reference signal
pattern in a control region of a first of the subframes; and control information using a second
control channel having a second reference signal pattern in one of the control and data regions of
a second of the subframes, wherein the second reference signal pattern is different from the first
reference signal pattern.
According to one aspect of the present invention, there is provided a communication
device for communicating with communication apparatus of a cellular communication system
the communication device comprising: means for registering the communication device in at
least one communication cell operated by the communication apparatus; means for receiving a
plurality of sub-frames from the communication apparatus, wherein: each sub-frame comprises a
plurality of communication resources defining a control region for communicating a respective
control channel and a plurality of communication resources defining a data region for
communicating a respective data channel; and the receiving means is operable: to receive a first
control channel having a first reference signal pattern in a control region of a first of the
subframes; and to receive a second control channel having a second reference signal pattern in at
least one of a control region and a data region of a second of the subframes, wherein the second
reference signal pattern may be different from the first reference signal pattern; and means for
interpreting control information communicated in the first control channel having a first
reference signal pattern, and for interpreting control information communicated in the second
control channel having a second reference signal pattern.
According to one aspect of the present invention, there is provided a communication
apparatus for communicating with a plurality of mobile communication devices in a cellular
communication system the communication apparatus comprising: means for operating at least
one communication cell; means for communicating a plurality of subframes with each of a
plurality of communication devices within the at least one cell, wherein: the communicating
means is operable to communicate: control information using a first control channel
omnidirectionally throughout the cell; and control information using a second control channel in
a direction spatially focussed towards a communication device for which the control information
is intended.
According to one aspect of the present invention, there is provided a communication
device for communicating with communication apparatus of a cellular communication system
the communication device comprising: means for registering the communication device in at
least one communication cell operated by the communication apparatus; means for receiving a
plurality of sub-frames from the communication apparatus, wherein:the receiving means may be
operable: to receive a first control channel omnidirectionally by the communication apparatus
throughout the cell; and to receive a second control channel transmitted in a direction spatially
focussed towards the communication device; and means for interpreting control information
communicated in the first control channel, and for interpreting control information
communicated in the second control channel.
According to one aspect of the present invention, there is provided communication
apparatus for communicating with a plurality of mobile communication devices in a cellular
communication system the communication apparatus comprising: a cell controller adapted to
operate at least one communication cell; a transceiver operable to communicate a plurality of
subframes with each of a plurality of communication devices within the at least one cell,
wherein: each sub-frame comprises a plurality of communication resources defining a control
region for communicating a respective control channel and a plurality of communication
resources defining a data region for communicating a respective data channel; and the
transceiver ismay be further operable to communicate: control information using a first control
channel having a first reference signal pattern in a control region of a first of the subframes; and
control information using a second control channel having a second reference signal pattern in at
least one of the control and data regions of a second of the subframes, wherein the second
reference signal pattern is different from the first reference signal pattern.
According to one aspect of the present invention, there is provided a communication
device for communicating with communication apparatus of a cellular communication system
the communication device comprising: a cell registration module operable to register the
communication device in at least one communication cell operated by the communication
apparatus; a transceiver operable to receive a plurality of sub-frames from the communication
apparatus, wherein: each sub-frame comprises a plurality of communication resources defining a
control region for communicating a respective control channel and a plurality of communication
resources defining a data region for communicating a respective data channel; and the
transceiver is further operable: to receive a first control channel having a first reference signal
pattern in a control region of a first of the subframes; and to receive a second control channel
having a second reference signal pattern in at least one of the control region and the data region
of a second of the subframes, wherein the second reference signal pattern is different from the
first reference signal pattern; and a processor operable to interpret control information
communicated in the first control channel having a first reference signal pattern, and to interpret
control information communicated in the second control channel having a second reference
signal pattern.
Aspects of the invention extend to computer program products such as computer readable
storage media having instructions stored thereon which are operable to program a programmable
processor to carry out a method as described in the aspects and possibilities set out above or
recited in the claims and/or to program a suitably adapted computer to provide the apparatus
recited in any of the claims.
Each feature disclosed in this specification (which term includes the claims) and/or
shown in the drawings may be incorporated in the invention independently (or in combination
with) any other disclosed and/or illustrated features. In particular but without limitation the
features of any of the claims dependent from a particular independent claim may be introduced
into that independent claim in any combination or individually.
Brief Description of the Drawings:
Embodiments of the invention will now be described by way of example only with
reference to the attached figures in which:
Figure 1 schematically illustrates a telecommunication system;
Figure 2 illustrates a possible subframe configuration for component carriers for the
telecommunication system of Figure 1;
Figure 3 shows a simplified illustration of a resource grid for demodulation reference
signals in the telecommunication system of Figure 1;
Figure 4 shows a simplified block diagram of a first base station for the
telecommunication system of Figure 1;
Figure 5 shows a simplified block diagram of a second base station for the
telecommunication system of Figure 1;
Figure 6 shows a simplified block diagram of a mobile communication device for the
telecommunication system of Figure 1;
Figure 7 shows a simplified flow chart illustrating operation of the telecommunication
system of Figure 1;
Figure 8 schematically illustrates another telecommunication system;
Figure 9 illustrates a possible subframe configuration for component carriers for the
telecommunication system of Figure 8;
Figure 10 illustrates another possible subframe configuration for component carriers for
the telecommunication system of Figure 8;
Figure 11 schematically illustrates another telecommunication system;
Figure 12 illustrates a possible subframe configuration for component carriers for the
telecommunication system of Figure 0 ;
Figure 13 schematically illustrates another telecommunication system;
Figure 14 illustrates a radio frame for the telecommunication system of Figure 13;
Figure 5 illustrates a number of possible subframe configurations for component carriers
for the telecommunication system of Figure 13;
Figure 16 schematically illustrates another telecommunication system; and
Figure 17 illustrates a number of possible subframe configurations for component carriers
for the telecommunication system of Figure 16.
Detailed Description of Exemplary Embodiments:
Overview
Figure 1 schematically illustrates a mobile (cellular) telecommunication system 1 in
which a user of any of a plurality of mobile communication devices 3-1 to 3-7 can communicate
with other users via one or more of a plurality of base stations 5-1, 5-2 and 5-3. In the system
illustrated in Figure , each base station 5 shown is an Evolved Universal Terrestrial Radio
Access Network (E-UTRAN) base station capable of operating in a multi-carrier environment.
In Figure 1, the base station labelled 5-1 comprises a so called 'macro' base station
operating a plurality of relatively geographically large 'macro' cells 7, 8 using respective
component carriers (CCs) CI, C2, of a component carrier set. In this embodiment, the macro
base station 5-1 operates component carrier CI as a primary component carrier on which a
primary cell (PCell) 7 is provided, and component carrier C2 as a secondary component carrier
on which a secondary cell (SCell) 8 is provided. The PCell 7 has a larger geographical coverage
than the SCell 8. The difference in the size of the PCell 7 and SCell 8 may be by design (e.g. as
a result of using a lower transmit power for component carrier C2) or may result from one or
more radio environmental factors affecting the primary carrier C1 and secondary carrier C2 to
different extents (e.g. path loss affecting a lower frequency primary carrier CI to a lesser extent
than a higher frequency secondary carrier C2).
The other base stations 5-2, 5-3 shown in Figure 1 each comprises a so called 'pico' base
station operating a plurality of 'pico' cells 9-2, 9-3, 10-2, 10-3, using a component carrier set
having component carriers (CCs) CI, C2 corresponding in frequency to those used by the macrobase
station 5-1. Each pico base station 5-2, 5-3 operates a respective pico primary cell (PCell)
9-2, 9-3 on component carrier C2 and a respective pico secondary cell (SCell) 10-2, 10-3 on
component carrier CI. Thus, the pico Pcells 9 share substantially the same frequency band as
the macro Scell 8, and the pico Scells 0 share substantially the same frequency band as the
macro Pcell 7. As seen in Figure 1, the power of the carriers CI, C2 used to provide the pico
cells 9, 10 is set such that the geographical coverage of the pico PCells 9, of this example, are
substantially co-incident with the geographical coverage of the pico SCells 10.
The power used to provide pico cells 9, 10 is low relative to the power used for the macro
cells 7, 8 and the pico cells 9, 10 are therefore small relative to the macro cells 7, 8. As shown in
Figure 1, in this example the geographical coverage of each of the pico cells 9, 10 falls
completely within the geographical coverage of the macro PCell 7 and overlaps partially with the
geographical coverage of the macro SCell 8.
Referring to Figure 2, in which the subframe configuration for the component carriers for
each of the cells is illustrated, it will be apparent that there is a potential for relatively high
communication interference between the macro PCell 7 and each of the pico SCells 10. The risk
of interference is high because the macro PCell 7 and pico SCells 10 operate in co-incident
geographical regions and use a common component carrier frequency. Further, the strength of
communication signals from the macro base station 5-1, in the geographical area covered by
each pico Scell 10, may be comparable to communication signals from the respective pico base
station 5-2, 5-3 because of the relatively high power used by the macro base station 5-1
compared to that used by the pico base stations 5-2, 5-3. Whilst there is also the potential for
some interference between the macro SCell 8 and each of the pico PCells 9, any such
interference is likely to be relatively small and restricted to the relatively small geographical
region in which the macro SCell 8 and pico PCells 9 overlap.
In order to alleviate the issue of interference, the component carrier C2 used for the
macro Scell 8 is operated by the macro base station 5-1 as an extension carrier on which the
nature of information that may be transmitted is restricted. Specifically, the component carrier,
when operating as the extension carrier may not be used for transmission of any of the following:
• a Physical Downlink Control Channel (PDCCH);
• a Physical Hybrid ARQ Indicator Channel (PHICH);
• a Physical Control Format Indicator Channel (PCFICH);
• a Physical Broadcast Channel (PBCH);
• a Primary Synchronization Signal (PSS);
• a Secondary Synchronization Signal (SSS); or
• a Common Reference Signal / Cell-specific Reference Signal (CRS).
The macro base station 5-1 operates carrier CI for the PCell 7 as a stand-alone carrier
having a Physical Downlink Control Channel (PDCCH), which can be used to schedule the
resources of its own component carrier CI (as shown by arrow X). The PDCCH of component
carrier CI can also be used to schedule the resources of component carrier C2 ('cross carrier
scheduling') to be used for communication purposes by a mobile communication device 3 when
operating in the macro Scell 8 (as shown by arrow Y). The PDCCH is transmitted
omnidirectionally throughout the cell.
The respective component carrier CI used for each of the pico SCells 10 is also operated
as an extension carrier by the associated pico base station 5-2, 5-3. The respective component
carrier C2 used for each of the pico Pcells 9 is operated, by the associated pico base station 5-2,
5-3, as a stand-alone carrier having an associated PDCCH for scheduling resources within its
own component carrier C2 (as shown by arrow X'). This PDCCH can also be used for cross
carrier scheduling resources of component carrier CI to be used for communication purposes by
a mobile communication device 3 when operating in the associated pico Scell 10 (as shown by
arrow Y').
As illustrated in Figures 1 and 2, in this embodiment whilst a conventional PDCCH is not
provided on the extension carriers, a dedicated Beamformed Physical Downlink Control Channel
(BFed PDCCH) 4-1, 4-2, 4-5 is provided using the extension component carrier C2 of the macro
SCell 8. The BFed PDCCH 4-1, 4-2, 4-5 is directional and can be used selectively to schedule
resources of the extension component carrier C2 for the macro SCell 8 (as shown by arrow Z) for
specific mobile communication devices 3. The BFed PDCCH is used in conjunction with
frequency selective scheduling in which the mobile communication device reports the channel
state information (CSI) such as channel quality indicator (CQI) for each resource block (RB) or
group of RBs in frequency domain of the system bandwidth and the base station selects the best
resource blocks to use to schedule the BFed PDCCH for each terminal.
In this exemplary embodiment, a BFed PDCCH is not provided for the extension
component carrier CI of the pico SCells 10-2, 10-3. Instead each pico base station 5-2, 5-3
operates its respective extension component carrier CI as a completely PDCCH-less component
carrier as shown in Figure 2.
The PDCCH of the primary component carrier CI, operated by the macro base station 5-
1, can thus be used for scheduling resources (e.g. as shown by arrow Y) for a mobile
communication device 3-7, located in the macro SCell 8, but which is in geographical close
proximity to a pico PCell 9-2 being operated on the same component carrier C2 as the macro
SCell 8. Accordingly, interference between the macro SCell 8 and the pico PCell 9-2 is avoided
because, although the macro SCell 8 and the pico PCell 9-2 are being operated using same
component carrier frequency band (C2), the control information for each cell is transmitted using
a different respective component carrier frequency band.
The BFed PDCCH 4-1, 4-2, 4-5 of the extension component carrier C2 for macro SCell 8
can be used selectively to schedule resources for a respective mobile communication device 3-1,
3-2, 3-5, operating within the macro SCell 8, but which is not geographically close to one of the
pico PCells 9-2, 9-3. Accordingly, where interference is not such a significant risk, the capacity
of the PDCCH of the component carrier CI used for the macro Pcell 7 can, beneficially, be
conserved without significantly affecting interference.
For the smaller pico cells in which control channel capacity is not such an issue, the
PDCCH of the respective component carrier C2 operated by each pico base station 5-2, 5-3, can
be used for the cross carrier scheduling of resources for any mobile communication device 3-3,
3-4 located in the respective pico SCell 10-2, 10-3. As described above, the pico cells are
geographically located entirely within the region covered by the macro PCell 7. Accordingly,
the absence of a BFed PDCCH, for the component carrier CI operated by each pico base station
5-2, 5-3, avoids the interference that could otherwise potentially result with the PDCCH of the
macro PCell's component carrier CI.
Beamformed Physical Downlink Control Channel (BFedPDCCH)
A possible implementation of a BFed PDCCH will now be described, in more detail.
The beamforming of the BFed PDCCH 4-1, 4-2, 4-5 is achieved using a multi-layer
beamforming approach that is suitable for a multiple input multiple output (MIMO) based
communication system in which the transmitters and the receivers of the signals have multiple
antennas. Beamforming is achieved using a precoding technique in which the phase (and
possibly gain) of each stream of signals transmitted from each of a plurality of antennas is
independently weighted such that the power of each signal stream is focussed in the direction of
interest (e.g. that of the mobile communication device for which the BFed PDCCH is intended)
to maximise the signal level. Similarly, the power of each stream of signals is minimised in other
directions, including directions in which interference is a potential issue (e.g. that of the pico
cells 9, 10).
In order to beamform successfully, the state of the channel is analysed based on Channel
State Information (CSI) measured by the mobile communication devices 3 and reported to the
macro base station 5-1. The CSI comprises information such as a rank indicator (RI), precoding
matrix indicator (PMI), a channel quality indicator (CQI) and/or the like. Based on this
information, an appropriate type of beamforming is selected. For example, where full CSI is
reliably available a statistical eigenvector beamforming technique may be used. In situations
where a more limited CSI is available, an interpolation technique may be used estimate the CSI
for beamforming. In situations where no CSI is available the CSI may be estimated blindly at
the base station, for example from received signal statistics or uplink signals received from the
terminal.
Figure 3 shows a resource grid for an orthogonal frequency division multiplexing
(OFDM) subframe 30 for the communication system 1 of Figure 1, in which a BFed PDCCH is
provided. The resource grid shown is for a resource block (RB) pair each RB having, for
example, a resource grid similar to that described in section 6.2 of the 3rd Generation Partnership
Project (3GPP) Technical Standard (TS) 36.21 1 V10.2.0 and shown in Figure 6.2.2-1 of that
standard.
As seen in Figure 3, the BFed PDCCH transmission is provided in a set of resource
elements 35 in a control region 3 1 of the subframe 30. The control region 3 1 comprises resource
elements 35 of the first three OFDM symbols of the first slot of the subframe 30, and spans all
twelve subcarrier frequencies of one resource block (RB). The remaining resource elements 35
of the first slot and the resource elements 35 of the second slot form a data region 33 in which
the Physical Downlink Shared Channel (PDSCH) is transmitted. A set of UE specific PDSCH
demodulation reference signals (DMRS) and UE specific BFed PDCCH DMRS are provided in
the data region 33 and control region 31 respectively as illustrated.
The DMRS pattern for the BFed PDCCH is different to that used for a legacy PDCCH.
In the DMRS pattern shown in Figure 3, PDSCH DMRS for antenna ports 7 and 8 are
transmitted in resource elements 35 at three evenly distributed subcarrier frequencies, in each of
the last two symbols of the first slot and in each of the last two symbols of the second slot.
PDSCH DMRS for antenna ports 9 and 0 are also transmitted in resource elements 35 at three
evenly distributed subcarrier frequencies (different to those used for ports 7 and 8), in each of the
last two symbols of the first slot and in each of the last two symbols of the second slot. BFed
PDCCH DMRS for antenna ports x l and x2 are transmitted in resource elements 35 at three
evenly distributed subcarrier frequencies, in each of the first two symbols of the first slot. BFed
PDCCH DMRS for antenna ports x3 and x4 are transmitted in resource elements 35 at three
evenly distributed subcarrier frequencies (different to those used for ports x3 and x4), in each of
the first two symbols of the first slot.
Macro Base Station
Figure 4 is a block diagram illustrating the main components of the macro base station 5-
1 shown in Figure . The macro base station 5- 1 comprises an E-UTRAN multi-carrier capable
base station comprising a transceiver circuit 4 1 which is operable to transmit signals to, and to
receive signals from, the mobile communication devices 3 via a plurality of antennas 433. The
base station 5-1 is also operable to transmit signals to and to receive signals from a core network
via a network interface 435. The operation of the transceiver circuit 43 is controlled by a
controller 437 in accordance with software stored in memory 439.
The software includes, among other things, an operating system 441, a communication
control module 442, a component carrier management module 443, a measurement management
module 445, a control channel management module 446, a direction determination module 447,
a resource scheduling module 448, and a beamforming module 449.
The communication control module 442 is operable to control communication with the
mobile communication devices 3 on the component carriers (CCs) CI, C2, of its component
carrier set. The component carrier management module 443 is operable to manage the use of the
component carriers CI, C2 and, in particular, the configuration and operation of the macro PCell
7 and macro SCell 8 and the operation of the secondary component carrier C2 for the SCell 8 as
an extension carrier. The measurement management module 445 communicates with the mobile
communication device 3 to configure the mobile communication device 3 to initiate
measurement of the CSI and to receive and analyse measurement reports received from the
mobile communication devices 3 to assess the channel state for the purposes of beamforming.
The direction determination module 447 determines the directional position of a mobile
communication device 3, relative to the base station 5-1, for beamforming purposes, from the
uplink signals that the base station 5-1 receives from that mobile communication device 3. The
resource scheduling module 448 is responsible for scheduling the resources of the primary and
extension component carrier CI, C2 to be used by the mobile communication devices 3
operating in the macro cells 7, 8. The beamforming module 449 manages the formation of the
directional 'beam' via which the BFed PDCCH 4-1, 4-2, 4-5 is provided to the respective mobile
communication devices 3-1, 3-2, 3-5.
In this exemplary embodiment, the control channel management module 446 determines
which control channel to use for scheduling resources of the extension carrier C2 of the macro
SCell 8 based on trigger messages received from the mobile communication device 3. These
trigger messages indicate either that a mobile communication device is within range of a pico
base station 5-2, 5-3 or that a mobile communication device 3 is no longer within range of a pico
base station 5-2, 5-3.
Specifically, if a mobile communication device 3 has not issued a trigger message
indicating that it is within range of a pico base station 5-2, 5-3, or if it has issued a trigger
message indicating that it is no longer within range of a pico base station 5-2, 5-3, then the
control channel management module 446 determines that the mobile communication device 3
should receive resource scheduling for the extension carrier C2 of the macro SCell 8 via a BFed
PDCCH provided on the extension carrier C2.
If a mobile communication device 3 has issued a trigger message indicating that it is
within range of a pico base station 5-2, 5-3, then the control channel management module 446
determines that the mobile communication device 3 should receive resource scheduling for the
extension carrier C2 of the macro SCell 8 via a PDCCH provided on the primary component
carrier CI of the macro PCell 7.
In the above description, the base station 5-1 is described for ease of understanding as
having a number of discrete modules. Whilst these modules may be provided in this way for
certain applications, for example where an existing system has been modified to implement the
invention, in other applications, for example in systems designed with the inventive features in
mind from the outset, these modules may be built into the overall operating system or code and
so these modules may not be discernible as discrete entities.
Pico Base Station
Figure 5 is a block diagram illustrating the main components of a pico base station 5-2, 5-
3 shown in Figure . Each pico base station 5-2, 5-3 comprises an E-UTRAN multi-carrier
capable base station comprising a transceiver circuit 531 which is operable to transmit signals to,
and to receive signals from, the mobile communication devices 3 via at least one antenna 533.
The base station 5-2, 5-3 is also operable to transmit signals to and to receive signals from a core
network via a network interface 535. The operation of the transceiver circuit 53 is controlled
by a controller 537 in accordance with software stored in memory 539.
The software includes, among other things, an operating system 541, a communication
control module 542, a component carrier management module 543, a cell type identifier module
547 and a resource scheduling module 548.
The communication control module 542 is operable to control communication with the
mobile communication devices 3 on the component carriers (CCs) C1, C2, of its component
carrier set. The component carrier management module 543 is operable to manage the use of the
component carriers CI, C2 and in particular the configuration and operation of the pico PCell 9
and pico SCell 10 and the operation of the secondary component carrier CI for the SCell 10 as
an extension carrier. The cell type identifier module 547 provides information for identifying the
cells controlled by the base station 5-2, 5-3 as pico cells 9, 10. This information is provided to
mobile communication devices 3 that come within (or close to) the coverage area of the pico
Pcell 9. In this exemplary embodiment, for example, the cell type identifier module 547
broadcasts information identifying the cells it controls to be pico cells. The resource scheduling
module 548 is responsible for scheduling the resources of the primary and extension component
carrier C2, CI to be used by the mobile communication devices 3 operating in the pico cells 9,
10.
In the above description, the base station 5-2, 5-3 is described for ease of understanding
as having a number of discrete modules. Whilst these modules may be provided in this way for
certain applications, for example where an existing system has been modified to implement the
invention, in other applications, for example in systems designed with the inventive features in
mind from the outset, these modules may be built into the overall operating system or code and
so these modules may not be discernible as discrete entities.
Mobile Communication Device
Figure 6 is a block diagram illustrating the main components of the mobile
communication devices 3 shown in Figure 1. Each mobile communication device 3 comprises a
mobile (or 'cell' telephone) capable of operating in a multi-carrier environment. The mobile
communication device 3 comprises a transceiver circuit 651 which is operable to transmit signals
to, and to receive signals from, the base stations 5 via at least one antenna 653. The operation of
the transceiver circuit 651 is controlled by a controller 657 in accordance with software stored in
memory 659.
The software includes, among other things, an operating system 661, a communication
control module 662, a measurement module 665, and a cell identification module 667, a cell
proximity detection module 668, and a resource determination module 669.
The communication control module 662 is operable for managing communication with
the base stations 5 on the associated component carriers (CCs) CI, C2. The measurement
module 665 receives measurement configuration information from the base station 5-1 for the
purposes of configuring the mobile communication device 3 to take measurements of the CSI.
The measurement module 665 manages performance of the measurements of CSI (e.g. for the
macro cells 7, 8), generates associated measurement reports and transmits the generated reports
to the macro base station 5-1. The measurement module 665 also determines reference signal
received power (RSRP) for the pico cells 9, 10 for use in determining the proximity of the
mobile communication device 3 to the pico cells. The cell identification module 667 is operable
to determine the type of cell, which the mobile communication device 3 enters, or comes
geographically close to, from information provided by the base station 5-2, 5-3, controlling that
cell. In this exemplary embodiment, for example, the cell identification module 667 is operable
to receive the information for identifying the cell type that is broadcast by a pico base station 5-2,
5-3, and to identify the cell type to be a pico cell from the received information.
The cell proximity detection module 668 uses the measurements of RSRP from the pico
Pcells 9 to determine the proximity of the mobile communication device 3 to the pico Pcells 9 by
comparing the RSRP measurement to a predetermined 'trigger' threshold 663. The trigger
threshold is set such that an RSRP above the trigger threshold indicates that the mobile
communication device 3 is in a geographical location that is close enough to a pico Pcell 9 for
there to be a risk of associated control channel interference between the PDCCH on the primary
carrier (C2) of the pico PCell 9 and the BFed PDCCH on the extension carrier C2 of the macro
SCell 8
Hence, if the RSRP measurement exceeds the threshold value, then the mobile
communication device 3 is deemed to be sufficiently close to (or within) the pico cell for there to
be a risk of interference between any BFed PDCCH transmitted on the extension carrier C2 of
the macro SCell 8 with the PDCCH of transmitted on the extension carrier C2 of the pico PCell 9.
When the trigger threshold 663 is exceeded, the cell proximity detection module 668 triggers a
message to the macro base station 5-1 indicating that the mobile communication device is within
range of a pico base station 5-2, 5-3. When the RSRP measurement drops below the trigger
threshold 663, the cell proximity detection module 668 triggers a message to the macro base
station 5-1 indicating that the mobile communication device is no longer within range of a pico
base station 5-2, 5-3.
The resource determination module 669 determines the resources scheduled for use by
the mobile communication devices 3 for communication purposes by decoding the PDCCH
and/or BFed PDCCH appropriately.
In the above description, the mobile communication device 3 is described for ease of
understanding as having a number of discrete modules. Whilst these modules may be provided
in this way for certain applications, for example where an existing system has been modified to
implement the invention, in other applications, for example in systems designed with the
inventive features in mind from the outset, these modules may be built into the overall operating
system or code and so these modules may not be discernible as discrete entities.
Operation
Figure 7 is a flow chart illustrating typical operation of the communication system 1 to
schedule resources for use by a mobile communication device (MCD) 3 during communications.
In Figure 7, the exemplary operation scenario begins (at SI) when a mobile
communication device 3 starts operating in the Scell 8 of the macro base station 5-1, in a
geographical location that is sufficiently far from the pico Pcells 9 for there to be little risk of
associated control channel to control channel interference. The base station 5-1 determines the
direction of the mobile communication device 3 relative to the base station at S2 and identifies
an appropriate precoding matrix (also referred to as a precoding vector) for use in beamforming
the BFed PDCCH for that mobile communication device 3 in the determined direction. The
macro base station 5-1 schedules the resources for the extension carrier C2 of the macro SCell 8
using within-carrier scheduling via the BFed PDCCH (at S3).
In this example, each pico base station broadcasts information for identifying itself to be
a pico base station 5-2, 5-3 at S4 and the mobile communication device 3 determines, from this
broadcast identity information, that the base station 5-2, 5-3 is a pico base station (at S5). The
mobile communication device 3 identifies the reference signals that it receives from the pico
base stations 5-2, 5-3 and then monitors the reference signal received power (RSRP) of these
reference signals relative to the predetermined trigger threshold (at S6).
In this example, while the RSRP remains below the trigger threshold, the process in steps
S2 to S6 is repeated via loop LI. When the RSRP increases above the trigger threshold it sends
a 'trigger' message to the macro base station 5-1 to indicate that it is in sufficient range of a pico
base station 5-2, 5-3, for control channel interference to be a significant risk at S7. On receipt of
the trigger message, the macro base station 5-1 determines that it should no longer use a BFed
PDCCH for that mobile communication device 3 and schedules the resources for the extension
carrier C2 of the macro SCell 8 using cross-carrier scheduling via the PDCCH of the macro
PCell's primary component carrier CI at S8.
The mobile communication device 3 continues to monitor the reference signal received
power (RSRP) of the reference signals from the pico base station 5-3, 5-3 relative to the
predetermined trigger threshold at S6 (via loop L2). While the RSRP remains above the trigger
threshold, the process in step S8 is repeated via loop L4. When the RSRP drops below the
trigger threshold it sends another 'trigger' message to the macro base station 5-1 to indicate that
it is no longer in sufficient range of a pico base station 5-2, 5-3 for control channel interference
to be a significant risk (at S9 via loop L4). On receipt of the further trigger message, the macro
base station 5-1 determines that it can start to use a BFed PDCCH for that mobile
communication device 3 again and schedules the resources for the extension carrier C2 of the
macro SCell 8 using within-carrier scheduling via the BFed PDCCH of the macro SCell's
extension component carrier C2 (at S3) following appropriate direction finding and beamforming
(at S2).
Application in a communication system in which macro PCell andpico PCell use same carrier
Figure 8 schematically illustrates a further mobile (cellular) telecommunication system
81. The telecommunication system 81 is similar to that of Figure 1 and corresponding parts are
given the same reference numerals.
In the telecommunication system 81, a plurality of mobile communication devices 3-1 to
3-7 can communicate with other users via one or more of a plurality of base stations 5-1, 5-2 and
5-3. In the system illustrated in Figure 1, each base station 5 shown is an Evolved Universal
Terrestrial Radio Access Network (E-UTRAN) base station capable of operating in a multicarrier
environment.
In Figure 8, the base station labelled 5-1 comprises a macro base station operating a
plurality of relatively geographically large macro cells 7, 8 using respective component carriers
(CCs) CI, C2, of a component carrier set. In this embodiment, the macro base station 5-1
operates component carrier CI as a primary component carrier on which a primary cell (PCell) 7
is provided, and component carrier C2 as a secondary component carrier on which a secondary
cell (SCell) 8 is provided. The PCell 7 has a larger geographical coverage than the SCell 8.
The other base stations 5-2, 5-3 shown in Figure 8, each comprises a pico base station
operating a plurality of 'pico' cells 9-2, 9-3, 10-2, 10-3, using a component carrier set having
component carriers (CCs) CI, C2 corresponding in frequency to those used by the macro-base
station 5-1. In this exemplary embodiment, unlike that shown in Figure 1, each pico base station
5-2, 5-3 operates a respective pico primary cell (PCell) 9-2, 9-3 on component carrier CI and a
respective pico secondary cell (SCell) 10-2, 10-3 on component carrier C2.
Thus, unlike the system of Figure 1, the pico Pcells 9 share substantially the same
frequency band as the macro Pcell 7, and the pico Scells 10 share substantially the same
frequency band as the macro Scell 8. The geographical coverage of each of the pico cells 9, 10
falls completely within the geographical coverage of the macro PCell 7. However, the overlap
between the pico cells 9 and 10 and the macro SCell 8 is relatively small.
Referring to Figure 9, in which the subframe configuration for the component carriers for
each of the cells is illustrated, it will be apparent that there is a potential for relatively high
communication interference between the PDCCH of the macro PCell 7 and the PDCCH of each
of the pico PCells 9. In this exemplary embodiment, however, this interference is avoided by
using a time domain solution in which the macro base station 5-1 transmits a PDCCH only in
certain subframes and the pico base stations 5-2, 5-3 transmits a PDCCH in other subframes that
do not overlap in time with the subframes used by the base station 5- .
More specifically, the macro base station 5-1 uses a first predetermined set of subframes
of a radio frame (in this example even numbered subframes) to transmit a PDCCH and each pico
base station 5-2, 5-3 uses a second predetermined set of subframes of a radio frame (in this
example odd numbered subframes) to transmit a respective PDCCH. Accordingly, because the
PDCCH provided by the macro base station 5-1 and the pico base stations 5-2, 5-3, do not
overlap the risk of control channel to control channel interference is avoided. The subframes in
which a particular base station 5 does not transmit a PDCCH are also not used for data (e.g.
PDSCH) transmission by that base station and, accordingly, are referred to as almost blank
subframes (ABS). These ABS may, however, be used for transmission of common / cell-specific
reference signals (CRS).
The potential for any interference between the macro SCell 8 and each of the pico SCells
10 is relatively small.
Each base station 5 operates carrier CI for its PCell 7, 9 as a stand-alone carrier having a
Physical Downlink Control Channel (PDCCH), which can be used to schedule the resources of
its own component carrier C (as shown by arrows X and X'). The PDCCH of each component
carrier CI can also be used to schedule the resources of component carrier C2 ('cross carrier
scheduling') to be used for communication purposes by a mobile communication device 3 when
operating in the corresponding Scell 8, 10 (e.g. as shown by arrow Y).
The respective component carrier C2 used for each of the Scells 8, 10 is operated, by the
associated base station 5, as an extension carrier (as described previously) on which a BFed
PDCCH 4-1, 4-2, 4-3, 4-5, 4-8 can be provided. The BFed PDCCH 4-1, 4-2, 4-3, 4-5, 4-8 is
directional and can be used selectively to schedule resources of the extension component carrier
C2 for each SCell 8, 10 (e.g. as shown by arrows Z and Z') for specific mobile communication
devices 3. The BFed PDCCH of each extension component carrier C2 can also be used to
schedule the resources of the related primary component carrier CI ('cross carrier scheduling')
to be used for communication purposes by a mobile communication device 3 when operating in
the corresponding Pcell 7, 9 (e.g. as shown by arrow W).
The BFed PDCCH 4-1, 4-2, 4-3, 4-5, 4-8 of the extension component carrier C2 for each
SCell 8, 10 can be used selectively to schedule resources for a respective mobile communication
device 3-1, 3-2, 3-3, 3-5, 3-8 operating within in the corresponding SCell 8, 10. Accordingly,
the risk of interference in the region in which the macro SCell 8 and pico SCell 10 does overlap
is significantly reduced because of the geographically localised nature of the BFed PDCCH. The
DMRS pattern for the BFed PDCCH is different to that used for a legacy PDCCH.
Figure 10 shows another possible subframe configuration for the component carriers for
the system of Figure 8. In the configuration shown in Figure 10, the control region of the
subframes provided using component carrier C2 used for each SCell 8, 10 is partitioned into a
BFed PDCCH region in which the BFed PDCCH is provided, and a PDCCH-less region in
which no PDCCH or BFed PDCCH is provided. The regions are generally equal sized and are
partitioned such that the BFed PDCCH region for the macro SCell 8 does not overlap with the
BFed PDCCH region for the pico SCell 10, thereby reducing the small risk of control channel to
control channel interference even further.
Application in a communication system in which only the pico base stations use a BFed
PDCCH
Figure 11 schematically illustrates a further mobile (cellular) telecommunication system
111 and Figure 1 shows a possible subframe configuration for the component carriers for the
system of Figure 1 . The telecommunication system 11 is similar to that of Figure 8 and
corresponding parts are given the same reference numerals.
The communication system is, essentially, the same as that shown in Figure 8 except that
only the pico base stations 5-2, 5-3 provide a BFed PDCCH and, unlike the system of Figure 8,
the macro base station 5-1 provides all resource scheduling for the macro SCell 8 via a PDCCH
provided in the primary component carrier CI for the macro PCell 7 (e.g. as shown by arrow Y
in Figure 12).
More specifically, each base station 5 operates carrier C1 for its PCell 7, 9 as a stand
alone carrier having a PDCCH that can be used to schedule the resources of its own component
carrier CI (as shown by arrows X and X'). The PDCCH of each component carrier CI can also
be used to schedule the resources of component carrier C2 ('cross carrier scheduling') to be used
for communication purposes by a mobile communication device 3 when operating in the
corresponding Scell 8, 10 (e.g. as shown by arrow Y).
The respective component carrier C2 used for each of the Scells 8, 10 is operated, by the
associated base station 5, as an extension carrier as described previously. However, the
component carrier C2 used for the macro Scell 8 is not provided with a PDCCH or a BFed
PDCCH and so can only be scheduled using the PDCCH provided on the primary component
carrier CI . The component carrier C2 used for each pico Scell 10 operated by the associated
pico base station 5-2, 5-3 can be provided with a BFed PDCCH 4-3, 4-8.
The BFed PDCCH 4-3, 4-8 is directional and can be used selectively to schedule
resources of the extension component carrier C2 for each pico SCell 0 (e.g. as shown by arrow
Z') for specific mobile communication devices 3. The BFed PDCCH of the extension
component carrier C2 for each pico SCell 10 can also be used to schedule the resources of the
related primary component carrier CI ('cross carrier scheduling') to be used for communication
purposes by a mobile communication device 3 (e.g. as shown by arrow W).
The BFed PDCCH 4-3, 4-8 of the extension component carrier C2 for each pico SCell 10
can thus be used selectively to schedule resources for a respective mobile communication device
3-3, 3-8 operating within the corresponding SCell 10. Accordingly, the risk of control channel to
control channel interference in the region in which the macro SCell 8 and pico SCell 10 overlaps
is significantly reduced.
Application in a single carrier communication system
Figure 13 schematically illustrates a further mobile (cellular) telecommunication system
131, Figure 14 shows the configuration of a radio frame for the system 131 of Figure 13, and
Figure 15 shows a number of possible subframe configurations for the system of Figure 13. The
telecommunication system 131 has similarities to those described earlier and corresponding parts
are given the same reference numerals. In the system illustrated in Figure 13, each base station 5
shown is an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) base station
capable of operating in a single-carrier environment.
A major difference between the system 131 shown in Figure 13 and those described
earlier is that the telecommunication system 131 is a single component carrier system which has
been adapted in a manner that allows legacy mobile communication devices to use the system as
normal (e.g. those defined by the 3rd Generation Partnership Project (3GPP) release 8, 9 and 10
standards) whilst more advanced mobile communication device can advantageously be
scheduled using a BFed-PDCCH.
In Figure 13, the base station labelled 5-1 comprises a macro base station operating a
relatively geographically large macro cell 7 using a single component carrier CI (e.g. a
backwards compatible or 'legacy' component carrier). The other base stations 5-2, 5-3 shown in
Figure 13 each comprises a pico base station operating a pico cell 9-2, 9-3, using a component
carrier CI of the same frequency as the component carrier used by the macro base station 5-1.
The power used to provide pico cells 9 is low relative to the power used for the macro
cell 7 and the pico cells 9 are therefore small relative to the macro cell 7. As shown in Figure 13,
in this example the geographical coverage of each of the pico cells 9 falls completely within the
geographical coverage of the macro cell 7.
Referring to Figure 14, the configuration of a radio frame 140 for the communication
system 113 is shown. As seen in Figure 14, and as those skilled in the art will readily understand,
each radio frame comprises an E-UTRA radio frame comprising ten subframes 142, 144, a
number of which are reserved for Multi-Media Broadcast over a Single Frequency Network
(MBSFN). In Figure 14, the subframes reserved for MBSFN are referred to as MBSFN
subframes 144.
To allow legacy mobile communication devices to communicate successfully in the
system 131, the non-MBSFN subframes 142 comprise legacy E-UTRA subframes having a
legacy PDCCH (e.g. as defined in the relevant 3GPP release 8, 9 or 10 standards). Thus, older
(e.g. release 8, 9 and 10) mobile communication devices are advantageously able to monitor the
legacy PDDCH in the non-MBSFN subframes 142.
The MBSFN subframes 4 are configured with a BFed PDCCH with a corresponding
new DMRS pattern, as described previously. Newer (e.g. release 11 and beyond) mobile
communication devices 3, such as those shown in Figure 13, are advantageously able to monitor
both the legacy PDDCH in the non-MBSFN subframes 142 and the BFed PDCCH in the
MBSFN subframes 144.
Referring to Figure 15, there are a number of different options (labelled (a) to (c) in
Figure 15) for MBSFN subframe configuration for the system of Figure 13. In the first option
(a), the MBSFN subframes 144 of both the macro base station 5-1 and the pico base stations 5-2,
5-3 are provided with the BFed PDCCH. This option has the advantage of simplicity and the
fact that beamformed control channels 4-1, 4-2, 4-3, 4-5, 4-8 can be used in both the pico and
macro cells 7, 9.
In the second option (b), the MBSFN subframes 144 of both the macro base station 5-1
and the pico base stations 5-2, 5-3 are provided with a partitioned BFed PDCCH region and
PDCCH-less region (similar to that described with reference to Figure 10). The regions are
generally equal sized and are partitioned such that the BFed PDCCH region for the macro cell 7
does not overlap with the BFed PDCCH region for the pico cell 8. This option reduces the risk
of interference and allows beamformed control channels 4-1, 4-2, 4-3, 4-5, 4-8 to be used in both
the pico and macro cells 7, 9.
In the third option (c), the MBSFN subframes 144 of the of the pico base stations 5-2, 5-3
are provided with a BFed PDCCH region, whilst the MBSFN subframes 144 of the macro base
station 5-1 are not. This option reduces the risk of interference and allows beamformed control
channels 4-3, 4-8 to be advantageously used in the pico cells 9 (for this option, the macro base
station 5-1 does not use the beamformed control channels labelled 4-1, 4-2, 4-5 shown in Figure
13).
Application in a distributed antenna system
Figure 16 schematically illustrates a mobile (cellular) telecommunication system 161 in
which a user of any of a plurality of mobile communication devices 3-1 to 3-7 can communicate
with other users via a macro base station and a local antenna 15-0 at the base station and a
plurality of geographically distributed antennas 15-1, 15-2 and 15-3. Each distributed antenna
15-1 to 15-3 is connected to the base station (for example by a fibre optic link) and the base
station 5 controls reception and transmission via the antenna 15. The base station 5 uses a
common cell identity for communications via each antenna 15 and hence a mobile
communication device 3 being served by any one of the antenna 15 behaves as if it is operating
in a single cell.
In Figure 16, the base station effectively operates, on a first component carrier CI, a
single 'common' primary cell (PCell) 7 that comprises a plurality of primary sub-cells 7-0 to 7-3
each provided using a different respective antenna 15-0 to 15-3. The base station operates, on a
second component carrier C2, an effective secondary cell (SCell) 8 that comprises a plurality of
secondary sub-cells 8-0 to 8-3 each provided using a different respective antenna 15-0 to 15-3.
In the example shown, the 'local' or 'master' primary sub-cell 7-0 operated via the local
antenna 15-0 has a larger geographical coverage than the 'local' or 'master' secondary sub-cell
8-0 operated via the local antenna 15-0. The geographical coverage of each of the 'distributed'
sub-cells 7 - 1 to 7-3 and 8-1 to 8-3 operated via the distributed antennas 15-1 to 15-3 falls
completely within the geographical coverage of the local primary sub-cell 7-0 and overlaps
partially with the geographical coverage of the local secondary sub-cell 8-0. The power of the
carriers CI, C2 used to provide the distributed sub-cells 7 - 1 to 7-3 and 8-1 to 8-3 is set such that
the geographical coverage of the distributed primary sub-cells 7 - 1 to 7-3 (of this example) are
substantially co-incident with the geographical coverage of the distributed secondary sub-cells 8-
1 to 8-3. In the example shown the distributed sub-cell 7-2, 8-2 provided using distributed
antenna 15-2 partially overlaps with the distributed sub-cells 7-1, 7-3, 8-1, 8-3 respectively
provided using the other distributed antennas 15-1, 15-3. It will be apparent, therefore, that there
is a potential for relatively high control channel to control channel interference between the subcells
7, 8 where they overlap with one another.
In this exemplary embodiment, PDCCH to PDCCH interference on the primary
component carrier C2 may be avoided by appropriate time domain separation of the sub-frames
used to communicate the PDCCH (e.g. with ABS for the other sub-frames as described
previously).
Referring to Figure 17, in which the subframe configuration for the component carriers
for the distributed cells is illustrated, control channel to control channel interference on the
secondary carrier C2 is avoided by providing a different control channel (DMRS based PDCCH),
each having a different respective DMRS sequence, in the control regions of respective
subframes for overlapping distributed secondary subcells 8-1 to 8-3. The DMRS sequence
selected for the different DMRS based PDCCHs is selected to be substantially orthogonal.
As shown in Figure 17, a DMRS based PDCCH having a first DMRS sequence (DMRS
based PDCCH 1) is provided in the control region of subframes communicated in the nonoverlapping
secondary subcells 8-1 and 8-3 provided via antennas 15-1 and 15-3. A DMRS
based PDCCH having a second DMRS sequence (DMRS based PDCCH 2) is provided in the
control region of subframes communicated in the secondary subcell 8-2, provided via antenna
15-2, that overlaps with the other secondary subcells 8-1 and 8-2, thereby helping to avoid
control channel to control channel interference in the regions in which the secondary subcells 8
overlap.
The structure of each DMRS based PDCCH is, therefore, similar to that of the BFed
PDCCH of earlier examples. However, in this embodiment, the new PDCCH is transmitted from
a single antenna and is omnidirectional rather than beamformed. The structure of the DMRS
based PDCCH is, therefore similar to the BFed PDCCH as transmitted from a single antenna
port.
Other Modifications and alternatives
Detailed embodiments have been described above. As those skilled in the art will
appreciate, a number of modifications and alternatives can be made to the above embodiments
and variations whilst still benefiting from the inventions embodied therein.
It will be appreciated that although the macro and the pico base stations 5 have each been
described with particular reference to a different set of modules (as shown in Figures 4 and 5) to
highlight the particularly relevant features of the different base stations 5, the macro and the pico
base stations 5 are similar and may include any of the modules described for the other. For
example, each pico base station 5-2, 5-3 may include a measurement management module 445, a
direction determination module 447 and/or a beamforming module 449 as described with
reference to Figure 4. Similarly, the macro base station 5-1 may include a cell type identifier
module 547 as described with reference to Figure 5.
It will be appreciated that although the communication system 1 is described in terms of
base stations 5 operating as macro or pico base stations, the same principles may be applied to
base stations operating as femto base stations, relay nodes providing elements of base station
functionality, home base stations (HeNB), or other such communication nodes.
In the above embodiments, the cell type identifier module has been described as
providing information for identifying the cells controlled by the base station 5-2, 5-3 as pico
cells 9, 10 and that this information is broadcast to mobile communication devices 3 that come
within or close to the coverage area of the pico Pcell 9. It will be appreciated that the
information for identifying the cells provided by the base station 5-2, 5-3 may comprise any
suitable information such as a specific cell type identifier information element, or a cell identity
(Cell ID) from which cell type can be derived. For example, if a HeNB, rather than a pico base
station, operates the low power cells 9, 10, the cell type can be identified from comparing the
cell identity provided by the HeNB to a range of Cell IDs known to be allocated to HeNBs.
Further, whilst in the above description it is the mobile communication device that
determines whether a particular cell is a pico cell for which control channel interference is a risk,
the macro base station could also do this. For example, the macro base station may mandate any
mobile communication device configured with a BFed PDCCH, to carry out RSRP
measurements and to compare the results with predefined threshold value (e.g. similar to the
'trigger' threshold as described). If the results are found to be above that threshold value, the
mobile communication device simply reports the measurement to the base station with cell
identity information (e.g. the Cell ID) for the cell to which the measurements relate. On receipt
of the report, the macro base station (which has access to information identifying the cell IDs for
the pico cells in its coverage area) can avoid using a BFed PDCCH for a mobile communication
device that is close to a pico cell within its coverage area. In the case of HeNBs, the macro base
station is able to identify them, based on their cell IDs, so that the macro base station can avoid
using the BFed PDCCH for a mobile communication device that is close to an identified HeNB
cell.
Referring to the embodiment described with reference to Figure 1, whilst a BFed PDCCH
is not provided for the extension component carrier CI of the pico SCells 10-2, 10-3, it will be
appreciated that such a BFed PDCCH could potentially be provided, albeit at the possible
expense of interference between the PDCCH of the macro PCell 7 and the BFed PDCCH of the
pico SCell 9. It will also be appreciated that whilst it has not been described in significant detail
above, a BFed PDCCH of any of the communication systems could potentially be used for cross
carrier scheduling for any component carrier of that system regardless of whether or not a control
channel is provided for that component carrier.
Whilst a particular DMRS pattern has been described for the BFed PDCCH any suitable
DMRS pattern may be used that is different to that used for a legacy PDCCH.
It will be appreciated that the predetermined trigger threshold may be reconfigurable.
Further, the trigger threshold may be adaptive, for example to allow it to change automatically,
or semi-automatically, based on prevailing radio conditions. The threshold value, and timing of
the trigger message, may vary in dependence on the implementation. The optimum threshold
value for different situations may be arrived at based on simulation.
Where a flow chart shows discrete sequential blocks, this is for the purposes of clarity
only and, it will be appreciated that many of the steps may occur in any logical order, may be
repeated, omitted, and/or may occur in parallel with other steps. For example, referring to step
S4 of the flow chart of Figure 7, the pico base stations may broadcast identification periodically,
in parallel with the other of the steps shown. Similarly, steps S4 and S5 need not be repeated
every iteration of loops LI and L4. Further, the mobile communication device 3 may monitor
the RSRP of received reference signals continuously in parallel with the other steps.
Although the provision a beamformed PDCCH has been described in detail it will be
appreciated that other information, deliberately omitted from transmission on an extension
carrier, may also be provided in a beamformed manner on extension carriers. For example a new
beamformed Physical Hybrid ARQ Indicator Channel (BFed PHICH) may also be provided on
the extension carrier.
Although the terminology used refers to a beamformed PDCCH (BFed PDCCH), any
similar terminology may be used appropriately to refer to a new beamformed PDCCH and/or a
PDCCH having a modified DMRS (for example 'Precoded PDCCH', 'DMRS-based PDCCH',
'Codebook based beamforming PDCCH').
The beamforming may be codebook based in which a 'precoding' vector (for weighting
the transmissions from respective antennas) is selected from a set of predefined precoding
vectors (the 'codebook'). In this case the mobile communication device either knows, or is
informed of, the precoding vector used. The beamforming may be non-codebook based in which
the network applies arbitrary beamforming at the transmitter and the mobile communication
device has no immediate means for determining the nature of the beamforming that has been
applied. In this case a mobile communication device specific reference signal to which the same
beamforming has been applied is transmitted to allow estimation of the channel experienced by
the beamformed transmission. The pico and macro base stations may respectively use different
beamforming techniques (e.g. the pico base station may use codebook based beamforming or and
the macro base station may use non-codebook based beamforming or vice versa).
In the example described with reference to Figure 13, the BFed PDCCH was described as
being provided in the MBSFN subframes of a radio frame whilst the legacy PDCCH was placed
in other subframes. It will be appreciated that whilst using the MBSFN subframes is
advantageous in terms of simplicity of implementation, any appropriate predetermined
subframes may be used (for example ABS subframes). In a particularly advantageous scenario
for example, the subframes used for BFed PDCCH transmission use MBSFN subframes that are
also configured to be ABS subframes. The benefits of this arise because MBSFN subframes are
standardised for 3GPP, Release 8 mobile communication devices, and ABS subframes are
standardised for 3GPP Release 10 mobile communication devices. Thus, for backward
compatibility, Release 8 mobile communication devices are able to interpret MBSFN subframes,
and Release 10 mobile communication devices are able to interpret both MBSFN and ABS
subframes. Accordingly, having MBSFN subframes carrying the new BFed control channel as a
subset of subframes configured for Almost Blank Subframes (ABS) means that the legacy
Release 10 mobile communication devices will be able to effectively ignore them as ABS
subframes carrying no data, Release 8 mobile communication devices will be able to treat them
as MBSFN subframes and newer mobile communication devices, as described for the above
embodiments, will be able to treat them as BFed PDCCH carrying sub-frames.
Furthermore, in the example described with reference to Figure 13, by using co-ordinated
scheduling in which the macro base station 5-1 and pico base station 5-2, 5-3 exchange
information on when the BFed PDCCH is to be scheduled, collision between the BFed PDCCHs
transmitted by those base stations 5 can be avoided.
In yet another advanced variation of the example described with reference to Figure 13,
the macro base station 5-1 and pico base station 5-2, 5-3 can use the same resource for BFed
PDCCHs where orthogonal communication streams are applied based on CSI information
exchanged between the macro base station 5-1 and pico base station 5-2, 5-3.
In the exemplary embodiments described above, each new control channel having a new
DMRS pattern has been described as being provided in a control region of a subframe. It will be
appreciated that whilst this is particularly beneficial, the control channel could be provided in a
data region of a subframe or partially in a control region and partially in a data region whilst still
benefiting from many of the advantages provided by the invention. Nevertheless, despite the
fact that there may be a reluctance to reuse a region normally reserved for the existing PDCCH
because of the perceived technical difficulties in doing so, providing the new control channel(s)
having the new DMRS in the control region, as opposed to the data region does provide some
notable advantages. Firstly, for example, decoding a control channel in the region of a subframe
reserved as a control region is significantly quicker than decoding a control channel in the region
of a subframe reserved as a data region because mobile communication devices look at the
control region before the data region. Secondly, for similar reasons, decoding a control channel
in the region of a subframe reserved as a control region uses less battery power than decoding a
control channel in the region of a subframe reserved as a data region. Further, when no data
resources are allocated by the control channel, having the control channel in the control region
allows the mobile communication device to ignore the data region completely, with the power
and speed advantages that follow from such an arrangement.
In the above exemplary embodiments, a mobile telephone based telecommunications
system was described. As those skilled in the art will appreciate, the signalling techniques
described in the present application can be employed in other communications system. Other
communications nodes or devices may include user devices such as, for example, personal
digital assistants, laptop computers, web browsers, etc. As those skilled in the art will appreciate,
it is not essential that the above described relay system be used for mobile communications
devices. The system can be used to extend the coverage of base stations in a network having one
or more fixed computing devices as well as or instead of the mobile communicating devices.
In the exemplary embodiments described above, the base stations 5 and mobile
communication devices 3 each include transceiver circuitry. Typically, this circuitry will be
formed by dedicated hardware circuits. However, in some exemplary embodiments, part of the
transceiver circuitry may be implemented as software run by the corresponding controller.
In the above exemplary embodiments, a number of software modules were described. As
those skilled in the art will appreciate, the software modules may be provided in compiled or uncompiled
form and may be supplied to the base station or the relay station as a signal over a
computer network, or on a recording medium. Further, the functionality performed by part or all
of this software may be performed using one or more dedicated hardware circuits.
Various other modifications will be apparent to those skilled in the art and will not be
described in further detail here.
This application is based upon and claims the benefit of priority from United Kingdom
patent application No. 1112752.9, filed on July 25, 201 1, the disclosure of which is incorporated
herein in its entirety by reference.
WO 2013/015445 PCT/JP2012/069523
CLAIMS
. Communication apparatus for communicating with a plurality of mobile communication
devices in a cellular communication system said communication apparatus comprising:
means for operating at least one communication cell;
means for communicating, via a plurality of antenna ports, a plurality of subframes with
each of a plurality of communication devices within said at least one cell, wherein:
each sub-frame comprises a plurality of communication resources defining a
control region for communicating a respective control channel and a plurality of
communication resources defining a data region for communicating a respective
data channel; and
said communicating means is operable to communicate:
first control information using a first reference signal pattern and using a
first antenna port; and
second control information using a second reference signal pattern and
using a second antenna port.
2. A communication device for communicating with communication apparatus of a cellular
communication system said communication device comprising:
means for registering said communication device in at least one communication cell
operated by said communication apparatus;
means for receiving a plurality of sub-frames transmitted from said communication
apparatus via a plurality of antenna ports, wherein:
each sub-frame comprises a plurality of communication resources defining a
control region for communicating a respective control channel and a plurality of
communication resources defining a data region for communicating a respective
data channel; and
said receiving means is operable:
first control information communicated using a first reference signal
pattern and using a first antenna port by said communication apparatus;
and
second control information communicated using a second reference signal
pattern and using a second antenna port by said communication apparatus;
and
means for interpreting said control information communicated using said first reference
signal pattern, and for interpreting control information communicated using said second
reference signal pattern.
Communication apparatus for communicating with a plurality of mobile communication
devices in a cellular communication system said communication apparatus comprising:
means for operating at least one communication cell;
means for communicating a plurality of subframes with each of a plurality of
communication devices within said at least one cell, wherein:
each sub-frame comprises a plurality of communication resources defining a
control region for communicating a respective control channel and a plurality of
communication resources defining a data region for communicating a respective
data channel; and
said communicating means is operable to communicate:
a first control channel having a first reference signal pattern in a control
region of a first of said subframes; and
a second control channel having a second reference signal pattern in a
control region of a second of said subframes, wherein said second
reference signal pattern is different from said first reference signal pattern.
Communication apparatus according to claim 3 wherein said means for operating at least
one communication cell is operable to operate a first cell using a first component carrier
and a second cell using a second component carrier, and wherein said first subframe is
provided using said first component carrier and said second subframe is provided using
said second component carrier.
Communication apparatus according to claim 4 wherein said second component carrier is
operated as an extension carrier.
Communication apparatus according to claim 4 or 5 wherein said first component carrier
is operated as a stand-alone carrier.
Communication apparatus according to any of claims 3 to 6 wherein said communicating
means is operable to focus said second control channel spatially in a direction of a
specific communication device.
Communication apparatus according to any of claims 3 to 7 wherein said communicating
means is operable to transmit said first control channel omnidirectionally throughout said
at least one cell.
Communication apparatus according to any of claims 3 to 8 further comprising means for
determining whether a specific communication device should receive a first control
WO 2013/015445 PCT/JP2012/069523
channel having said first reference signal pattern, or a second control channel having said
second reference signal pattern.
10. Communication apparatus according to claim 9 wherein said determining means is
operable to determine whether said specific communication device should receive said
first control channel having said first reference signal pattern, or said second control
channel having said second reference signal pattern, based on a location of said
communication device.
11. Communication apparatus according to claim 10 wherein said determining means is
operable to determine whether said specific communication device should receive said
first control channel having said first reference signal pattern, or said second control
channel having said second reference signal pattern, based on the location of said
communication device relative to further communication apparatus.
12. Communication apparatus according to claim 11 wherein said determining means is
operable to determine the location of said communication device relative to said further
communication apparatus based on a result of a measurement of a parameter representing
a distance of said communication device from said further communication apparatus.
13. Communication apparatus according to claim 1 wherein said parameter representing a
distance of said communication device from said further communication apparatus
comprises a reference signal received power (RSRP) of a signal transmitted by said
further communication apparatus.
14. Communication apparatus according to any of claims 9 to 13 wherein said determining
means is operable to determine that said specific communication device should receive
said first control channel having said first reference signal pattern if a predefined
message has been received from the specific communication device.
15. Communication apparatus according to any of claims 9 to 14 wherein said determining
means is operable to determine that said specific communication device should receive
said second control channel having said second reference signal pattern if a further
predefined message has been received from the specific communication device.
16. Communication apparatus according to any of claims 9 to15 wherein said determining
means is operable to determine whether said specific communication device should
receive a said first control channel having said first reference signal pattern, or said
second control channel having said second reference signal pattern, in dependence on a
measurement report received from the specific communication device.
17. Communication apparatus according to claim 3 or 4 wherein said communication
WO 2013/015445 PCT/JP2012/069523
apparatus comprises a plurality of distributed antennas.
18. Communication apparatus according to claim 17 wherein said communicating means is
operable to communicate said first control channel having a first reference signal pattern
using any of said plurality of antennas.
19. Communication apparatus according to claim 17 or 18 wherein said communicating
means is operable to communicate said second control channel having a second reference
signal pattern using a subset comprising at least one, but not all, of said plurality of
antennas.
20. Communication apparatus according to claim 17, 18 or 19 wherein said communicating
means is operable to communicate a control channel having a third reference signal
pattern in a third of said subframes using a subset comprising at least one, but not all, of
said plurality of antennas, wherein said third reference signal pattern is different from
first reference signal pattern and said second reference signal pattern.
1. Communication apparatus according to claim 3 wherein said communicating means is
operable to communicate radio frames comprising a plurality of subfames, each subframe
having a different respective subframe location, and wherein said communicating means
is operable:
to communicate said first control channel having a first reference signal pattern in
a subframe at a subframe location, within a radio frame, selected from a first set
of subframe location(s) comprising at least one subframe location; and
to communicate said second control channel having a second reference signal
pattern in a subframe at a subframe location, within a radio frame, selected from a
second set of subframe location(s) comprising at least one subframe location;
wherein said first set of subframe location(s) does not comprise the same subframe
location(s) as said second set of subframe location(s).
22. Communication apparatus according to claim 3 or 2 1 wherein said first control channel
having a first reference signal pattern is not communicated in a subframe at a subframe
location of a multi-media broadcast over a single frequency network (MBSFN) subframe
and/or is not communicated in a subframe at a subframe location of an almost blank
subframe (ABS).
23. Communication apparatus according to claim 3, 2 1 or 22 wherein said second control
channel having a second reference signal pattern is communicated in a subframe at a
subframe location of a multi-media broadcast over a single frequency network (MBSFN).
24. Communication apparatus according to any of claims 3 or 2 to 23 wherein said second
WO 2013/015445 PCT/JP2012/069523
control channel having a second reference signal pattern is communicated in a subframe
of an almost blank subframe (ABS).
25. Communication apparatus according to any of claims 3 to 24 wherein control
information communicated using said first and/or said second represents a resource
5 allocation for a communication device.
26. Communication apparatus according to any of claims 3 to 25 wherein each said reference
signal pattern comprises a demodulation reference signal pattern OMRS'.
27. A communication device for communicating with communication apparatus of a cellular
communication system said communication device comprising:
0 means for registering said communication device in at least one communication cell
operated by said communication apparatus;
means for receiving a plurality of sub-frames from said communication apparatus,
wherein:
each sub-frame comprises a plurality of communication resources defining a
15 control region for communicating a respective control channel and a plurality of
communication resources defining a data region for communicating a respective
data channel; and
said receiving means is operable:
to receive a first control channel having a first reference signal pattern in a
?0 control region of a first of said subframes; and
to receive a second control channel having a second reference signal
pattern in a in a control region of a second of said subframes, wherein said
second reference signal pattern is different from said first reference signal
pattern; and
25 means for interpreting control information communicated in said first control channel
having a first reference signal pattern, and for interpreting control information
communicated in said second control channel having a second reference signal pattern.
28. A communication device according to claim 27 wherein said receiving means is operable
to receive said first subframe on a first component carrier of a first frequency band and
30 said second subframe on a said second component carrier of a second frequency band.
29. A communication device according to claim 28 wherein said second component carrier is
operated as an extension carrier.
30. A communication device according to claim 28 or 29 wherein said first component
carrier is operated as a stand-alone carrier.
WO 2013/015445 PCT/JP2012/069523
31. A communication device according to any of claims 27 to 30 wherein said receiving
means is operable to receive said second control channel in a radio beam focussed
spatially in a direction of said communication device.
32. A communication device according to any of claims 27 to 31 wherein said receiving
means is operable to receive said first control channel in a radio communication
transmitted omnidirectionally throughout said at least one cell.
33. A communication device according to any of claims 27 to 32 further comprising means
for measuring a parameter representing a distance of said communication device from
further communication apparatus.
34. A communication device according to claim 33 wherein said parameter representing a
distance of said communication device from said further communication apparatus
comprises a reference signal received power (RSRP) of a signal transmitted by said
further communication apparatus.
35. A communication device according to claim 33 or 34 further comprising means for
transmitting a predefined message to said communication apparatus operating said cell in
dependence on a result of said measurement of said parameter representing a distance of
said communication device from said further communication apparatus.
36. A communication device according to claim 35 wherein said predefined message
comprises a measurement report including said result of said measurement.
37. A communication device according to claim 35 or 36 wherein said predefined message
comprises information representing an identity of said further communication apparatus
and/or of a cell operated by said further communication apparatus.
38. A communication device according to claim 35, 36 or 37 further comprising means for
comparing said parameter against a predetermined threshold value.
39. A communication device according to claim 38 wherein said transmitting means is
operable to transmit said predefined message if said comparison indicates that said
parameter has risen above said threshold value.
40. A communication device according to claim 38 or 39 wherein said transmitting means is
operable to transmit a further predefined message if said comparison indicates that said
parameter has fallen below said threshold value.
4 1. A communication device according to claim 23 wherein said receiving means is operable
to receive radio frames comprising a plurality of subfames, each subframe having a
different respective subframe location within the radio frame, and wherein said receiving
means is operable:
to receive a first control channel having a first reference signal pattern in a
subframe at a subframe location, within a radio frame, selected from a first set of
subframe location(s) comprising at least one subframe location; and
to receive a second control channel having a second reference signal pattern in a
subframe at a subframe location, within a radio frame, selected from a second set
of subframe location(s) comprising at least one subframe location;
wherein said first set of subframe location(s) does not comprise the same subframe
location(s) as said second set of subframe location(s).
A communication device according to claim 23 or 4 1 wherein said first control channel
having a first reference signal pattern is not received in a subframe at a subframe
location of a multi-media broadcast over a single frequency network (MBSFN) and/or is
not received in a subframe at a subframe location of an almost blank subframe (ABS).
A communication device according to claim 23, 4 1 or 42 wherein said second control
channel having a second reference signal pattern is received in a subframe at a subframe
location of a multi-media broadcast over a single frequency network (MBSFN).
A communication device according to any of claims 23, or 4 1 to 43 wherein said second
control channel having a second reference signal pattern is received in a subframe of an
almost blank subframe (ABS).
A communication device according to any of claims 23 to 44 wherein said control
information communicated using said first and/or said second represents a resource
allocation for the communication device.
A communication device according to any of claims 23 to 45 wherein each said reference
signal pattern comprises a demodulation reference signal pattern OMRS'.
A method, performed by communication apparatus, for communicating with a plurality
of mobile communication devices in a cellular communication system, the method
comprising:
operating at least one communication cell;
communicating, via a plurality of antenna ports, a plurality of subframes with each of a
plurality of communication devices within said at least one cell, wherein each sub-frame
comprises a plurality of communication resources defining a control region for
communicating a respective control channel and a plurality of communication resources
defining a data region for communicating a respective data channel;
communicating first control information using a first reference signal pattern and using a
first antenna port; and
communicating second control information using a second reference signal pattern and
using a second antenna port.
A method, performed by a communication device for communicating with
communication apparatus of a cellular communication system, the method comprising:
registering said communication device in at least one communication cell operated by
said communication apparatus;
receiving a plurality of sub-frames transmitted from said communication apparatus via a
plurality of antenna ports, wherein each sub-frame comprises a plurality of
communication resources defining a control region for communicating a respective
control channel and a plurality of communication resources defining a data region for
communicating a respective data channel;
receiving first control information communicated using a first reference signal pattern
and using a first antenna port by said communication apparatus;
interpreting said control information communicated using said first reference signal
pattern;
receiving second control information communicated using a second reference signal
pattern and using a second antenna port by said communication apparatus; and
interpreting control information communicated using said second reference signal pattern.
A method, performed by communication apparatus, of communicating with a plurality of
mobile communication devices in a cellular communication system said method
comprising:
operating at least one communication cell;
communicating a plurality of subframes with each of a plurality of communication
devices within said at least one cell, wherein each sub-frame comprises a plurality of
communication resources defining a control region for communicating a respective
control channel and a plurality of communication resources defining a data region for
communicating a respective data channel;
communicating control information using a first control channel having a first reference
signal pattern in a control region of a first of said subframes; and
communicating control information using a second control channel having a second
reference signal pattern in a control region of a second of said subframes, wherein said
second reference signal pattern is different from said first reference signal pattern.
A method, performed by a communication device, of communicating with
communication apparatus of a cellular communication system said method:
registering said communication device in at least one communication cell operated by
said communication apparatus;
receiving a plurality of sub-frames from said communication apparatus, wherein each
sub-frame comprises a plurality of communication resources defining a control region for
communicating a respective control channel and a plurality of communication resources
defining a data region for communicating a respective data channel;
receiving a first control channel having a first reference signal pattern in a control region
of a first of said subframes;
interpreting control information communicated in said first control channel having a first
reference signal pattern;
receiving a second control channel having a second reference signal pattern in a in a
control region of a second of said subframes, wherein said second reference signal
pattern is different from said first reference signal pattern; and
interpreting control information communicated in said second control channel having a
second reference signal pattern.
A computer program product comprising instructions operable to program a
programmable processor to implement communication apparatus according to any of
claims 3 to 26 or a communication device according to any of claims 27 to 46
Communication apparatus for communicating with a plurality of mobile communication
devices in a cellular communication system said communication apparatus comprising:
means for operating at least one communication cell;
means for communicating a plurality of subframes with each of a plurality of
communication devices within said at least one cell, wherein:
each sub-frame comprises a plurality of communication resources defining a
control region for communicating a respective control channel and a plurality of
communication resources defining a data region for communicating a respective
data channel; and
said communicating means is operable to communicate:
control information using a first control channel having a first reference
signal pattern in a control region of a first of said subframes; and
control information using a second control channel having a second
reference signal pattern in one of said control and data regions of a second
of said subframes, wherein said second reference signal pattern is different
from said first reference signal pattern.
A communication device for communicating with communication apparatus of a cellular
communication system said communication device comprising:
means for registering said communication device in at least one communication cell
operated by said communication apparatus;
means for receiving a plurality of sub-frames from said communication apparatus,
wherein:
each sub-frame comprises a plurality of communication resources defining a
control region for communicating a respective control channel and a plurality of
communication resources defining a data region for communicating a respective
data channel; and
said receiving means is operable:
to receive a first control channel having a first reference signal pattern in a
control region of a first of said subframes; and
to receive a second control channel having a second reference signal
pattern in at least one of a control region and a data region of a second of
said subframes, wherein said second reference signal pattern is different
from said first reference signal pattern; and
means for interpreting control information communicated in said first control channel
having a first reference signal pattern, and for interpreting control information
communicated in said second control channel having a second reference signal pattern.
Communication apparatus for communicating with a plurality of mobile communication
devices in a cellular communication system said communication apparatus comprising:
means for operating at least one communication cell;
means for communicating a plurality of subframes with each of a plurality of
communication devices within said at least one cell, wherein:
said communicating means is operable to communicate:
control information using a first control channel omnidirectionally
throughout said cell; and
control information using a second control channel in a direction spatially
focussed towards a communication device for which the control
information is intended.
A communication device for communicating with communication apparatus of a cellular
communication system said communication device comprising:
means for registering said communication device in at least one communication cell
operated by said communication apparatus;
means for receiving a plurality of sub-frames from said communication apparatus,
wherein:
said receiving means is operable:
to receive a first control channel omnidirectionally by the communication
apparatus throughout said cell; and
to receive a second control channel transmitted in a direction spatially
focussed towards said communication device; and
means for interpreting control information communicated in said first control channel,
and for interpreting control information communicated in said second control channel.
Communication apparatus for communicating with a plurality of mobile communication
devices in a cellular communication system said communication apparatus comprising:
a cell controller adapted to operate at least one communication cell;
a transceiver operable to communicate a plurality of subframes with each of a plurality of
communication devices within said at least one cell, wherein:
each sub-frame comprises a plurality of communication resources defining a
control region for communicating a respective control channel and a plurality of
communication resources defining a data region for communicating a respective
data channel; and
said transceiver is further operable to communicate:
control information using a first control channel having a first reference
signal pattern in a control region of a first of said subframes; and
control information using a second control channel having a second
reference signal pattern in at least one of said control and data regions of a
second of said subframes, wherein said second reference signal pattern is
different from said first reference signal pattern.
A communication device for communicating with communication apparatus of a cellular
communication system said communication device comprising:
a cell registration module operable to register said communication device in at least one
communication cell operated by said communication apparatus;
a transceiver operable to receive a plurality of sub-frames from said communication
apparatus, wherein:
each sub-frame comprises a plurality of communication resources defining a
control region for communicating a respective control channel and a plurality of
communication resources defining a data region for communicating a respective
data channel; and
said transceiver is further operable:
to receive a first control channel having a first reference signal pattern in a
control region of a first of said subframes; and
to receive a second control channel having a second reference signal
pattern in at least one of said control region and said data region of a
second of said subframes, wherein said second reference signal pattern is
different from said first reference signal pattern; and
a processor operable to interpret control information communicated in said first control
channel having a first reference signal pattern, and to interpret control information
communicated in said second control channel having a second reference signal pattern.