USER DEVICE FOR COMMUNICATING DATA AND METHOD
Field of the Invention
The present invention relates to users devices for tra nsmitting and receiving data and
methods of transmitting and receiving data.
Background of the Invention
Fourth generation mobile telecommunication systems, such as those based on the 3GPP
defined UMTS and Long Term Evolution (LTE) architecture are able t o support more sophisticated
services than simple voice and messaging services offered by previous generations of mobile
telecommunication systems.
For example, with the improved radio interface and enhanced data rates provided by LTE
systems, a user is able to enjoy high data rate applications such as mobile video streaming and
mobile video conferencing that would previously only have been availa ble via a fixed line data
connection. The demand to deploy fourth generation networks is therefore strong and the coverage
area of these networks, i.e. geographic locations where access to the networks is possible, is
expected t o increase rapidly.
The anticipated widespread deployment of fourth generation networks has led to the
parallel development of a class of devices and applications which, rather than taking advantage of
the high data rates availa ble, instead take advantage of the robust radio interface and increasing
ubiquity of the coverage area. Examples include so-called machine type communication (MTC)
applications, which are typified by semi-autonomous or autonomous wireless communication
devices (i.e. MTC devices) transmitting and receiving small amounts of data on a relatively
infrequent basis. Examples include so-called smart meters which, for example, are located in a
customer's house and periodically transmit information back to a central MTC server data relating to
the customers consumption of a utility such as gas, water, electricity and so on.
The nature of MTC devices may lead t o their disposal in locations where communication
with mobile telecommunications systems such as those mentioned above may prove unrelia ble,
even when taking into accou nt increasing coverage. For instance, MTC devices such as smart meters
may be located in the basement of a house or other hard to reach locations where signals from
mobile telecommunications system may not be received at a sufficient strength because they have
propagated over highly attenuating channels. Consequently, devices such as smart meters may be
una ble t o perform relia ble detection and estimation of data conveyed by the signals. Scenarios such
as this may also occur when devices are near the border of a geographic area served a by mobile
telecommunications system. Overcoming these problems by further extending the coverage of
mobile communications networks would allow an increased number of devices to be supported by
mobile communications networks.
The use of decreased coding rates and reduced order mod ulations schemes present a
potential solution to improving the relia bility of detection and estimation of data at a device.
However, often a restricted set of possible modulation and coding rates are supported by devices,
especially low cost ones such as MTC devices, and therefore improvement via coding changes may
be limited. Recently it has been suggested that transmission repetition may present an alternative
solution to extending coverage to mobile devices which are currently una ble to be relia bly served by
a mobile communications network.
Summary of the Invention
According to an example embodiment, there is provided a user device arranged to transmit
and to receive data to and from an infrastructure equipment via a wireless access interface, the
wireless access interface being provided by the infrastructure equipment using a plurality of
Orthogonal Frequency Division Multiplexing (OFDM) su bcarriers, the plurality of su bcarriers
extending across at least a first bandwidth. The infrastructure equipment transmits repeatedly
signals representing a same instance of user device payload data in a second bandwidth, the second
bandwidth being less than and within the first bandwidth and including a su bset of the OFDM
su bcarriers, and user device is configured t o receive one or more of the signals repeatedly
transmitted across the second bandwidth and to store in a memory signals representing the
repeated ly transmitted signals received across the second bandwidth. The user device is also
configured to com bine the stored signals and t o detect the user device payload data from the
com bined signals, the user device having been provided with an indication of the second bandwidth.
According to another example embodiment, the infrastructure equipment transmits
repeatedly signals representing a same instance of user device control data in the first bandwidth,
the user device control data providing an indication of a location of the signals representing the user
device payload data in the second bandwidth. The user device is configured t o receive one or more
of the repeatedly transmitted signals representing user device control data across the first
bandwidth, store in the memory signals representing the repeatedly transmitted received across the
first bandwidth, combine the stored signals representing the repeatedly transmitted signals received
across the first bandwidth, and detect the user device control data from the combined signals
representing the repeatedly transmitting signals received across the first bandwidth. The detection
of the user device payload data from the com bined signals received across the second bandwidth
being based on the indication of the location of the signals representing the user device payload
data in the second bandwidth.
Repeating transmissions of signals representing user device payload data ena bles a user
device which is una ble to detect and estimate user payload data from a single instance of the signal,
to com bine multiple signal instances. The combined signals may then be utilised to increase the
strength of the received signal or provide additional coding bits and therefore improve an accuracy
of the su bsequent data estimation. The repetition of signals representing a same instance of data
provides an alternative to decreasing a coding rate and or modulation order of data when
attempting to increase the accuracy of data detection and estimation at a receiver of a user device
when attempting, for example, t o increase the coverage of a mobile network. The use of repetition
may be usefu l for example, when it is not possible to alter coding rates or modu lation orders or they
can not be further reduced because of compatibility requirements within a system Repetition may
also present an alternative to coding rates changes, when the capa bilities of intended receiving
devices are limited. For instance, a machine type communications (MTC) device may be una ble to
perform complex decoding procedures but can receive multiple instance of signal and com bine the
received signals. Transmitting repetitions of signals representing user device payload data within a
second bandwidth which is less than and within the first system bandwidth reduces the signals that
a user device is required to store and com bine when the location of signals representing the user
device payload data within the second bandwidth is not yet known. For insta nce, before user device
control data has been detected and estimated, the user device is required t o store signals from the
second bandwidth as opposed to across the first bandwidth. This approach therefore reduces
memory requirements at the user device for storing repeated signals representing user payload data
whilst still allowing the storage and accumulation of the signals representing the user device control
data and the user device payload data to be su bstantially concurrent, therefore reducing the
acquisition time of the user device payload data.
The expression "signals representing a same instance of user device payload data or user
device control data" is used to include various techniques for transmitting data which represent the
same user data, which can be com bined to increase the likelihood of correctly recovering the user
data. In one example the repeated transmission of the signals representing the user data is a
repetition of the same signals. In other examples the user data may be encoded so that incremental
redundancy can be used in which an amount of parity of codeword digits are increased by the
repeated transmission of the signals, such that the repeated signals may be different.
According to another example embodiment, the wireless access interface provided by the
plurality of OFDM su bcarriers is divided into a plurality of time periods and the repeated signals
representing the user device payload data are transmitted in a same set of resources of the wireless
access interface in a first time period and in a second time period, and the user device is configured
to receive the user device payload data in the same set of resources of the wireless access interface
in the first time period and in the second time period
Repeating of signals representing the user device payload data in the same set of resources
within different time period mea ns that the channel over the signals propagate may be su bstantially
similar and therefore may simplify the com bining of the signals. It may also be beneficial because the
user device is only required to detect and estimate data from a particular portion of the second
bandwidth.
According to another example embodiment, the user device is configured to receive the
indication of the second bandwidth from the infrastructure equipment prior t o receiving the
repeated transmissions of the signals representing the user device control data.
Transmitting an indication of the second bandwidth t o the user device prior to the
transmission of control data allows the user device t o reduce the bandwidth across which it receives
signals that may include user device payload data t o the second bandwidth without having first to
have received signals representing the user device control data. Consequently, the signals
representing the user device control data and the signals representing the user device payload data
may be received and stored simultaneously.
According to another example embodiment, the user device is configured to receive user
device payload data within a virtual carrier of a predetermined bandwidth, the second bandwidth
being approximately equal to the predetermined bandwidth, and the predetermined bandwidth
includes a set of the OFDM su bcarriers that is su bstantially similar to the OFDM su bcarriers that
form the su bset of the OFDM su bcarriers included in the second bandwidth.
Configuring the second bandwidth to be approximately equal to a virtual carrier bandwidth
allows the repetition of signals to be integrated with the virtual carrier concept for user devices such
as machine type communication (MTC) devices. This allows the operation of such devices to be
simplified because it reduces the bandwidth that MTC devices operate t o receive payload data
compared to having a second bandwidth which is separate from the virtual carrier.
Various further aspects and features of the present invention are defined in the appended
claims, including but not limited to, methods of communicating between a user device and an
infrastructure equipment.
Brief Description of the Drawings
Em bodiments of the present disclosure will now be described by way of example only with
reference to the accompanying drawing in which like parts are provided with corresponding
reference numerals and in which:
Figure 1 provides a schematic diagram of a wireless communications system;
Figure 2 provides a schematic diagram of a receiver of a user device of the communications
system of Figure 1;
Figure 3 provides a schematic diagram of LTE su bframes;
Figure 4 provides a schematic diagram of LTE su bframes where signal repetition is
implemented;
Figure 5 provides a schematic diagram of a receiver of a user device configured to receive
repeated signals;
Figure 6 provides a schematic diagram of LTE su bframes where signal repetition is
implemented;
Figure 7 provides a schematic diagram of LTE su bframes where signal repetition is
implemented in accordance with an embodiment of the present technique;
Figure 8 provides a schematic diagram of LTE su bframes where signal repetition is
implemented in accordance with an embodiment of the present technique;
Figure 9 provides a schematic diagram of LTE su bframes where signal repetition is
implemented in accordance with an embodiment of the present technique; and
Figure 10 provides a schematic diagram of LTE su bframes where signals repetition and
windowed signal reception is implemented in accordance with an embodiment of the present
technique.
Detailed Description of Example Embodiments
Mobile Communications System
Figure 1 provides a schematic diagram of a mobile communications system 100 for
transmitting and receiving data t o and from one or more user devices, where the communications
system may for example operate in accordance with 3GPP Long Term Evolution (LTE). The
commu nications system comprises infrastructure equipment 101 such as a base station or enhanced
nodeB (eNodeB) which forms part of a mobile commu nications network and is configured to provide
a wireless access interface to one or more user devices 102 103. The user devices 102 103 may for
example be mobile phones, machine type communication (MTC) devices such as smart meters or
information aggregation devices in cars or medical devices, or tablet computers. Within the wireless
access interface the infrastructure equipment transmits signals representing the data to the one or
more user devices. In Figure 1 user devices 103 provides an example of a smart meter located in the
basement of a house. The infrastructure equipment 101 is communicatively linked via
commu nication link 104 t o a core network 105 which may in turn be linked to further infrastructure
equipment 106 and other commu nications networks and systems, where the further infrastructure
equipment may itself be linked to one or more user devices 102.
In exa mples where the system 100 is an LTE system, the wireless access interface will be
provided in accordance with orthogonal frequency division multiplexing (OFDM) where downlink
resources are temporally divided in a plurality of time periods and divided in frequency into a
plurality of su bcarriers where the su bcarriers form in the time domain OFDM sym bols that convey
signals which represent data to be transmitted to the user devices. The data transmitted to the users
devices may consist of control plane data and user plane data where the control plane data coveys
control data required by the user devices in order to commu nicate in the downlink (from
infrastructure equipment to user device) and uplink (from user device to infrastructure equipment)
with the infrastructure equipment, and user plane data conveys user device payload data. Further
discussion of the wireless access interface is presented below.
User Device Receiver
Figure 2 provides a schematic diagram of a simplified receiver that may be fou nd in a user
device configured t o receive and transmit data in the communications system of Figure 1. In an
example where the system 100 is an LTE system, the receiver may for example be an OFDM receiver.
An antenna 201 receives signals transmitted from the infrastructure equipment over a channel and
passes them to a baseband converter 202 which down converts the received signal to baseband
frequencies. The baseband signal is then sampled by a sampler 203 at a sampling rate suita ble for
the baseband frequencies. A synchroniser 204 is then configured t o detect the timing of the control
plane data and user plane data before processing of the synchronised signal by a control data
estimator 205 and a payload data estimator 206. The control data estimator estimates user device
control data from signals representing the control data and provides information to payload data
estimator which is required t o estimate the user device payload data from the signals representing
the user device payload data. As mentioned above, Figure 2 provides a simplified OFDM receiver and
therefore a number of elements of an OFDM have not been included. For example, frequency offset
correction, transformation of the received signal into the frequency domain for equalisation and
data estimation, guard interval removal etc. However, the processes performed by these elements
and further elements may be performed using any suita ble processing means known in the art.
Downlink Resource Allocation
Figure 3 provides a simplified exa mple of downlink resource allocation, which may for
example being applica ble in an LTE system. The downlink resou rces are temporally divided into
periods referred t o as su bframes 301 where a time period referred to as a radio frame may be
formed from 10 su bframes and the su bframes may be 1ms in duration. The downlink resources are
divided in frequency into a plurality of subcarriers, where the number of su bcarriers may vary
between approximately 128 and 2048 dependent upon the bandwidth of the downlink resources,
where possible downlink bandwidths may include for example 1.25M Hz, 2.5M Hz, 5MHz, 10M Hz,
15M Hz and 20M Hz. Each su bframe may be further divided in time into two 0.5ms slots where a slot
comprising 12 su bcarriers may be referred t o as a resource block.
Each su bframe includes control or signalling data which may for example be transmitted
over a physical channel such as a physical downlink control channel (PDCCH) in LTE, where the
control data indicates which downlink resources, in terms of su bcarriers, slots and timing within the
su bframes, have been allocated to each of the user devices currently being served by the
infrastructure equipment via the wireless access interface. Payload data is transmitted in the
downlink over a data channel such as a physical downlink shared channel (PDSCH) in LTE, where the
control data indicates t o a user device a location in the data channel in which its payload data will be
transmitted and the parameters required to estimate the payload data. Payload data may for
example include uplink resource allocations, a request for information from the infrastructure
equipment or information for an application running on the user device In Figure 3, three downlink
su bframes of an LTE system are illustrated where control data is transmitted over the physical
downlink control channel (PDCCH) and user device payload data is transmitted across the physical
downlink shared channel (PDSCH). In an example reception routine, a user device, such as an MTC
device, detects signals representing control data transmitted across the PDCCH 302 303 at the
beginning of each su bframe 301. The user device will then estimate the control data received across
the PDCCH of each su bframe in order esta blish whether it has been allocated resources in the PDSCH
of the corresponding su bframe. If within the control data of the PDCCH there is no indication of user
payload data intended for the user device i.e. PDCCH 302, the user device will not attempt to receive
signals which from the following PDSCH i.e. PDSCH 304. However, if the estimated control data
indicates to the user device that there is data intended for it in the PDSCH i.e. PDCCH 305, the user
device will receive signals that form the relevant portion 306 of the following PDSCH 307 that the
control data has specified, and su bsequently estimate the user payload data from the received
signals. As can be seen from Figure 3, the resources 306 in the PDSCH allocated to a user device may
not extend over all the su bcarriers in the su bframe and/or over the full temporal length of the
PDSCH in the su bframe. This, along with the control data conveyed by signals transmitted across the
PDCCH allows for the allocation of resources in the PDSCH t o a plurality of user devices.
A user device is configured to detect and estimate payload data conveyed in the PDSCH.
Accurate detection and estimation of data is dependent on a num ber of factors, for instance,
knowledge of the location of the signals representing the payload data in a su bframe and reception
of the signals representing the user payload data at a sufficient signal strength and quality. In turn,
knowledge of the location of the signals representing the payload data is dependent upon receiving
the signals across the PDCCH at a sufficient signal strength and quality so that the user device
control data can be detected and accurately estimated. Consequently, receiving signals representing
user device control data and payload data at a sufficient signal strength are both required in order to
detect and recover payload data in the downlink of an LTE communication system or any other
equivalent communications system.
During conventional operation of a user device in an LTE network, if the user device control
data cannot be accurately estimated and recovered from the signals transmitted and received across
the PDCCH and/or the user device payload data cannot be accurately estimated and recovered from
the PDSCH, the user device data is una ble to be received by the user device. This may occur for
example when the channel between the infrastructure equipment and the user device is highly
attenuating thus resulting in highly attenuated signals being received at the receiver. In such a case,
the user device may indicate to the infrastructure equipment that the user payload data has or has
not been received correctly via an ACK or NACK message and the infrastructure equipment will
prepare to resend the payload data. The data may be retransmitted in a su bsequent su bframe,
where each of the instances of the user device control data and associated payload data are
independent from one another and may be transmitted in different portions of the PDCCH and
PDSCH, respectively. This procedure may be sufficiently robust for user devices which experience
varia ble channels due to mobility for instance, because poor channel conditions may improve in the
near future. Consequently, su bsequent transmission(s) of signals representing the user device
control data and payload data may be able to be received at a sufficient strength and quality that
the user device control data and payload data can be accurately detected and estimated. However,
in the case of user devices which are not mobile and/or are unlikely to experience channel
conditions sufficient for relia ble detection and estimation of control and or payload data, the above
described procedure is unlikely to be sufficiently robust. The use of reduced coding rates and
reduced order modulation schemes may be able to mitigate the effects of some poor channels, but
it is likely that there will still be channels of poor enough quality that user devices are una ble to
relia ble detect and estimate control and or payload data from received signals. Furthermore, there
may be limits within a system that restrict the coding rates and modulation orders that may be used.
For example, user device capa bilities, compatibility issues and system parameters may lead to
minimum coding rates which are supported by the system, thus limiting the gains in estimation
accuracy that obtained by limiting the coding rate. Furthermore, devices such as MTC devices, which
are low complexity and low power, may not have the capability to perform decoding of data which
has been encoded with complex encoding techniques.
User device 103 of Figure 1 is an example of a non-mobile user device which may not
experience channel conditions sufficient for accurate detection and estimation of control and or
payload data from received signals. As can be seen from Figure 1, user device 103 is stationary and
located in the basement of a house and therefore signals representing user device control data and
payload data may be received at a signal strength and or quality which is not sufficient for accurate
data detection and estimation, even with the use of low codes rates and modulation orders.
Consequently, smart meter 103 provides an example of a user device where the above described
reception routine may be insufficient to achieve the accurate recovery of user device control and
payload data. As well as user devices in hard to reach locations i.e. basements, user device which are
near the border of a cell served by infrastructure equipment may also experience similar problems
due to reception of highly attenuated signals.
Signal Repetition
In order t o address the above highlighted deficiencies and problems, it has been previously
proposed that a form of signal repetition may be utilised in order t o improve the strength and or
quality of the signal received at user devices. In particular, when the received signal strength of a
single instance of signals representing data is insufficient to ena ble relia ble data detection and
estimation. Repeating transmission of signals representing data provides a more simple
arrangement for improving the detection and estimation of communicated data without significantly
increasing processing power requirements and can be used for low data rate and delay tolerant
applications. Fu rthermore, repetition can use coding, modulation and other communications
parameters which are determined by a standard, such as LTE, and therefore may be compatible with
that standard.
Figure 4 provides a schematic illustration of a series of su bframes where an exa mple signal
repetition procedure is implemented. The principle of signal repetition is signals that represent a
same instance of control and/or payload data for a user device are repeatedly transmitted by the
infrastructure equipment over one or more su bfra mes or frames. The signals may be in a
su bstantially similar position or in su bstantially simila r set of resources of the wireless access
interface in each of the su bframes or frames so that they propagate over a su bstantially similar
channel. However in some examples the repeated signals may be transmitted in different resources
in each su bframe or frame where differences in channel across which the signals are transmitted are
mitigated for example by equalisation. In other examples the signals may be repeated within a same
su bframe or frame. The receiver of the user device is then configu red to receive each of the
repeated signals and to store signals representing the repeated signals in a memory, where the
stored signals may take the form of sampled un-demodulated baseband signals, soft estimates of
the data, or hard estimates of the data. The receiver then aggregates, accumulates or com bines the
stored signals, by summation or averaging for example, so that the relative received strength of the
com bined signals representing the user device control data and payload data is increased or
additional coding bits are availa ble for data estimation and correction. The user device then
proceeds t o estimate the control data from the combined signal, where the control data indicates
the location of the payload data in the combined signal representing the payload data intended for
the user device. By the following this procedure it is then possible for the accuracy of detection and
estimation of the user control and payload data to be increased. Returning to Figure 4, signals
representing control data are repeated in the PDCCH 401 of three consecutive subframes. The
repeated signals of the PDCCH 401 which represent control data are stored and then accumulated
402 and the control data intended for the user device estimated from the accumulated PDCCH at
403. The estimated control data provides the user device with an ind ication of the location in the
PDSCH of signals representing the user device's payload data 404. The user device then stores and
accu mulates the signals received from the indicated location 404 of the PDSCH in the next three
su bframes. The user device then recovers an estimate of its payload data from the accumulated
PDSCH signal at 405. In this manner an increased likelihood of a correct estimation of the payload
data can be achieved without su bstantially altering parameters of the signals and data such as
transmit power, coding rates and or modulation schemes. Accordingly, a transmitter and a receiver
performing the above describe repetition can be compatible with other LTE devices because signal
transmission characteristics such as coding rates have not been modified.
Figure 5 provides a simplified schematic diagram of an exa mple user device receiver which is
configured to receive repeated data transmissions. The structure of the receiver is su bstantially
similar to that illustrated in Figure 2 but further includes a memory 501 such as a buffer memory
which is configured to store received repeated signals. The memory 501 stores the received signals
representing the user device control data and the payload data, and under the control of a controller
502, passes the signals to the signal data estimator 205 and the payload data estimator 206. The
signals may be passed to the relevant estimator when a predetermined num ber of repeated signals
have been received or when the accumulated signals achieve an amplitude, via summation for
example, sufficient to ena ble relia ble detection and estimation of the data to be achieved. However,
the exact process by which the received signals are com bined may vary and is discussed in more
detail below. The controller may also be communicatively linked to the other elements of the
receiver in order t o configure the elements to store and accumulate signals from the relevant
portions of the PDSCH as indicated by recovered control data. For example, the controller may
require information from the control data estimator in order to configure the receiver to receive and
store signals representing data from appropriate parts of the PDSCH. The memory 501 may include
separate memories for the storage and accumulation of signals representing the control data the
payload data or other forms of data. Furthermore the configuration of the functional elements of
the receiver may vary depending on the form of repetition being utilised. For example, for repetition
techniques where signals are com bined after initial detection and estimation has taken place, an
additional estimator stage(s) may be required or the organisation of the receiver adapted
accordingly.
In order for the repetition structure of Figure 4 to be implemented, the user device may
require an indication of commencement of the repetition so that it can begin to store the relevant
received signals. However, this may cause problems if the indication signal itself cannot be received
without repetition. An alternative implementation is to configure the memory 501 to be a buffer
type memory that stores a maximum num ber of instances of signals and once the limit is reached,
discards the oldest signal instance and stores the most recently received signal instance. This process
can continue for example until the accumulated signal reaches a signal strength which is sufficient
for accurate data detection and estimation, thus indicating the buffer is predominantly made up of
the desired repeated signals. This may occur for example due t o the correlation between the
repeated signals representing the user data and the lack of correlation between the portions of the
frames or su bframes which are not repeated i.e. portions of the PDCCH which do not apply to the
user device and therefore change between frames or su bframes in which the signals for the user
device are repeated . Another alternative is for the infrastructure to continue t o repeat signals until
an acknowledgment is received from the user device indicating that the data represented by the
repeated signals has been accurately detected and estimated.
Although, the repetition scheme depicted in Figure 4 provides a num ber of advantages,
there are also associated costs. For exa mple, increased resources are utilised in order to send data
to the user device, where in Figure 4 approximately three times the normal resources are utilised to
transmit the payload data to the user device. Although this is an obvious disadvantage, it may be
mitigated by the fact that commu nication involving repetition may be predominantly used in off
peak periods where usage of the communications system is low, for example, during the night. This
also fits in with the properties of low cost MTC devices such as smart meters which are likely to have
delay tolerant data and therefor transmit data during off peak periods.
In LTE systems, in order to maintain compatibility with legacy LTE user devices that do not
support repetition, there may have t o be a one-to-one correspondence between control data
indicating where user device payload data is located in the corresponding PDSCH and the actual
location of the payload data. For example, even though the payload data transmitted in 406 is not
detected by the user device, the payload still has t o be transmitted or the corresponding resources
not used by another user device because the control data corresponding t o 406 will still specify that
there is data for the user device in portion 406 of the PDSCH. If this were not the case, it may be
possible for the scenario where two different portions of the control data specify that payload data
for two different user devices are at the same location in the PDSCH. The requirement of one-to-one
mapping of PDSCH resources t o one user device therefore results in an inefficient use of downlink
resources. However, in some examples the one-to-one mapping may be broken by signalling the
change prior t o the commencement of any repetition.
In some exa mples of signal repetition, in addition to transmitting signals representing
identical control data and payload data for a particular user device in a su bstantially identical
location in each frame or su bframe, the entirety of the frames or su bframes may have to be
repeated in a su bstantially identical manner. This therefore decreases flexibility and further reduces
efficiency. Furthermore, in some examples where channel conditions or coding rates etc. for
transmitting data to a user device are poor and or high, a large number of repetitions may be
required for a signal of sufficient strength/ or sufficient information t o be accu mulated at the user
device. Consequently, beca use the accumulation of the signals representing the control data and the
payload data are not performed concurrently, the delay in receiving the payload data may be
significant. For example, if a required number of repetitions in terms of su bfra mes is large i.e. 100, it
may be up to 200 su bframes before the payload data can be recovered. In such an example, if the
su bframes are 1ms in duration, a 200 su bframe delay may result in a delay of 0.2s, which may be
unaccepta ble in some scenarios or t o some user devices. Further still, with large repetition num bers
user devices may have to be in a receiving mode for a significant period of time as opposed t o a
reduced power mode, therefore consuming an increased amount of power. This may be particularly
problematic for low power, battery power devices such as MTC devices, whose time spent receiving
and transmitting signals should be kept to a minimum if possible.
Repetition has been described in general terms up to this point, however, there are a
number of alternative implementations of repetition and therefore a num ber of different methods
for accumulating and com bining received repeated signals. Two example repetition techniques are
chase com bining and incremental redu ndancy, which may be implemented as part of hybrid ACK
procedures. Chase com bining includes repeatedly transmitting a same instance of signals or portions
of a same instance of signals that represent a same instance of data and then combing these signals
at the receiver either pre or post demodulation. Consequently, chase com bining may be viewed as
increasing the signal-to-interference-plus -noise ratio (SIN R) of the received signal. Incremental
redundancy includes repeating signals which are different but represent a same instance of data, for
example different coded versions or different code bits of all or part of a same instance of data may
be transmitted during each repetition. Consequently, incremental redundancy may be viewed as
increasing the strength of the error correction coding at the receiver with the reception of each
repeated signal. At a user device receiving repeated signals, there are a variety of methods that may
be used to accumu late or combine the received repeated signals. For example, in chase combining
stored sampled baseband signals that represent the repeated signals may be combined via equalgain
com bining or maximum-ratio com bining. The combining may also be performed either preequalisation
or post-equalisation. In another example, combining of the signals may occur once soft
or hard decisions have been performed on each of the received equalised repeated signals. For
instance, an average may be taken over the soft decision from each instance of the repeated signals
and then a hard decision taken to estimate the data. Alternatively, a majority vote system may be
employed with hard decisions from each of the repeated signals. For incremental redundancy,
com bining of baseband signals may not be possible due t o the differing repeated signals and
therefore combining of signals representing soft or hard decisions may be more appropriate.
The aforementioned repetition and com bining methods are merely exa mples and any
suita ble methods known in the art may be used. Different methods of repetition and of combining
the received repeated signals each have their own advantages and disadvantages. For instance, if
sampled baseband signals are combined, it is the received signals representing the user device
control data and the payload data that are required to be stored as opposed to the data estimates
themselves. Therefore, it is sampled versions of portions of the baseband signal that are stored.
Storing signals in this manner may require significantly more memory than storage of signals
representing estimates of the underlying data as sampling has t o be performed at a frequency and
with a num ber of quantisation levels that are sufficient t o achieve a combined signal from which
control data and or payload data can be accurately detected and estimated. The actual sampling
frequency will be dependent on, among other things, the baseband frequencies via the sampling
theorem, and the number of quantisation levels is likely to be dependent on, among other things, at
least the modulation scheme, coding rates, and the required signal-to-noise ratio (SN R). However, if
signals are combined post-equalisation and or -post-demodulation, then memory requirements may
be reduced. In another example, if incremental redu ndancy is utilised, different coding bits are
transmitted with each repetition and so cannot merely be combined via summation. This approach
may therefore require increased memory compared to chase combining of soft or hard decisions
because one sym bol in memory corresponds to one received symbol, whereas in chase combing one
symbol in memory may be a summation of multiple repeated symbols. In exa mples where
com bining of signals representing the user payload data is performed post-equa lisation and after
preliminary soft or hard estimates, it may be required that user device control data has already been
detected and estimated. The user device control data may be required because it includes
information on the location and coding etc. of the user payload data that is necessary to detect and
estimate the user device payload data. Consequently, such a method may be suited to examples of
signal repetition where control data is received and estimated prior to reception of the repeated
signals representing the user payload data. With regards to repeated signals representing user
device control data, estimation of the data contained therein may be performed at any point after
reception, independent of the com bining method . This approach is possible by virtue of information
on the location of control information in frame or su bframe and any coding of the control data being
predefined and therefore known by the user device prior to reception.
Figure 6 provides an alternative implementation of signal repetition which may decrease the
acquisition time of the payload data. In contrast to Figure 4 where accumulation of signals
representing control data and payload data is done during different su bframes, in Figure 6 whilst the
signals transmitted across the PDCCH 601 are being accumulated all the signals transmitted across
the PDSCH 602 are buffered. Once the location of the signals representing the user device payload
data in the PDSCH is known and the parameters of the payload data are known, the payload data
may be detected and estimation from the buffered accu mulated signal at 604. If further
accumulation is required after estimation of the control data, the receiver can store and accumulate
only the relevant part of the PDSCH signals 605 indicated by the recovered control data. Although
this implementation may reduce acquisition delays, it requires a significant amount of memory in
order to store and accumulate all or a su bstantial proportion of the signals which represent the
PDSCH data prior to detection and estimation of the user device control data. In the case of low cost
and reduced power devices such as MTC devices, this may not be a practical solution.
Narrow Bandwidth Signal Repetition
Figure 7 illustrates an example embodiment of a repetition procedu re in accordance with
the present technique. Repetition of signals representing user device control data 701, using for
example chase combining or incremental redundancy as previously described, is performed within
the system bandwidth or first bandwidth of the system in a manner similar to that described with
reference to Figures 4 or 6. However, signals representing the user device payload data are
transmitted using chase com bining or incremental redundancy for example, within a predetermined
second bandwidth 702 within the PDSCH, where the second bandwidth is narrower than the first
bandwidth of the system or current su bframe and is also within the first bandwidth. The signals
representing the user device payload data may or may not extend across the entirety of the second
bandwidth and signals representing payload data for other user device(s) may also be transmitted
across the second bandwidth. Consequently, a su bset of the su bcarriers of the data channel PDSCH
are utilised for transmitting the repeated signals representing the user device payload data. A
receiver as illustrated in Figure 5 may therefore store and accumulate signals representing the
received signals or the control data contained therein whilst simultaneously storing and
accumulating signals representing received signals or the payload data contained therein without
storing and/or accumulating signals transmitted across the entirety or a significant portion of the
PDSCH bandwidth or first bandwidth. This is in contrast t o existing techniques as previously
described with reference to Figure 6.
In some example embodiments the second bandwidth could be formed by a Virtual carrier
arrangement. To support MTC terminals, it has been proposed to introduce a "virtual carrier"
operating within a bandwidth of one or more "host carriers": the proposed virtual carrier concept
preferably integrates within the communications resources of conventional OFDM based radio
access technologies and su bdivides frequency spectrum in a similar manner t o OFDM. Unlike data
transmitted on a conventional OFDM type downlink carrier, data transmitted on the virtual carrier
can be received and decoded without needing t o process the full bandwidth of the downlink OFDM
host carrier. Accordingly, data transmitted on the virtual carrier can be received and decoded using
a reduced complexity receiver unit: with concomitant benefits such as increased simplicity,
increased relia bility, reduced form-factor and lower manufacturing cost. The virtual carrier concept
is described in a number of co-pending patent applications (including GB 1101970.0 [2], GB
1101981.7 [3], GB 1101966.8 [4], GB 1101983.3 [5], GB 1101853.8 [6], GB 1101982.5 [7], GB
1101980.9 [8] and GB 1101972.6 [9]), the contents of which are incorporated herein by reference.
Once a sufficient num ber of instances of the repeated signals representing the control data,
and in particular the user device control data, have been accumulated and combined, the user
device control data is detected and estimated 703. In this case, a sufficient num ber of instances may
for example refer to accumulating signals until the data can be detected, until a predetermined
number of signals have been accumulated, or until the infrastructure equipment ceases repeating
the relevant signals. Su bsequently, if a sufficient num ber of repetitions of signals representing the
user device payload have been accumulated and combined, the user device payload data is detected
and estimated 704 from the appropriate location in the accumulated signals from the second
bandwidth. This procedure enables accumulation of the signals representing the user device payload
data t o be performed concurrently with the accumulation of the signals representing the user device
control data without buffering or storing signals transmitted and received across all of or a
su bstantial portion of the PDSCH. Therefore improvements in the speed of data acquisition may be
achieved compared to the procedure described with reference t o Figure 4, whilst also reducing the
memory requirements compared to the procedure described with reference t o Figure 6. For
example, if the PDSCH is 128 su bcarriers in bandwidth and the predetermined bandwidth is 12
su bcarriers, the user device may require approximately 90% less memory to store signals that
include signals representing the user device payload data compared to storing all signals received
from across the first bandwidth or the PDSCH. Consequently, by the use of large num bers of
repetitions and use of the reception techniques described above, coverage of a mobile
commu nications network may be extended to areas where user devices receive a weak signal which
would norma lly not be sufficient for communicating with the network, without significantly
increasing the memory requirements, costs or battery consumption of the user devices. This may be
particularly relevant for battery powered devices such as MTC devices for exa mple which require
both their costs and energy consumption to be reduced and therefore may not be suited t o existing
repetition techniques.
In order for a user device to have knowledge of the second bandwidth, additional signalling
indicating the second bandwidth may be required to be transmitted to the user device prior t o
commencement of repetition, for example, when a user device enters the coverage of an
infrastructure equipment such as a base station or eNB. Alternatively, the second bandwidth may be
hardcoded into repetition compatible user devices. In the former case, the infrastructure equipment
may be configured to select an appropriate second bandwidth based on for exa mple resource
allocation demands, channel conditions, the num ber of device requiring repetition etc. As
mentioned above, in some embodiments of the present technique, the second bandwidth may be
equivalent to or su bstantially similar to a predetermined bandwidth of a virtual carrier (VC), which
has been proposed in order t o simplify the operation of MTC devices. In such an embodiment a
separate second bandwidth in addition to the VC may not be required and therefore signalling of the
second bandwidth may not be necessary, thus leading to improvements in system efficiency. In
other embodiments of the present technique, the same predefined bandwidth may be allocated to
multiple user devices requiring repeated signals. In this case, multiple different signals may be
repeated within the second bandwidth of each su bframe. In further embodiments the second
bandwidth may be defined relative to the first bandwidth or the bandwidth of the PDSCH of each
su bframe. In such an embodiment the num ber of su bcarriers in a radio frame or su bframe or even
OFDM symbol t o OFDM sym bol may change without the infrastructure having to re signal the
second bandwidth. For example, the second bandwidth may be defined as su bcarriers 36 to 60 or
the su bcarriers 5/8xS t t o 6/8xS t where St is the total number of su bcarriers. However, regardless of
the means by which the second bandwidth is ind icated to the user device, improvements in power
consumption and memory requirements can be achieved at the user device when large repetition
num bers are utilised to extend the coverage of a mobile communications network.
In other embod iments, control information required t o be received by the user device may
be represented by signals which are transmitted over a bandwidth smaller than the first bandwidth
or the available bandwidth of the su bframe. The signals representing user device payload data may
also be repeated separately from signals representing user device control data, such as, in systems
where a one-to-one mapping from control data to the location of user device payload data is not
required. This embodiment would therefore further simplify the reception routine of the user device
and the cost and complexity of the user device because it will be required to operate over a reduced
bandwidth.
In some embodiments, due to low coding rates, increased transmission power, increased
frequency diversity etc., a larger number of instances of signals representing payload data may be
required t o be received compared to signals representing control data if the payload data is t o be
detected and estimated accurately. For instance, in some networks control data may be transmitted
with lower coding rates and lower order modulations schemes compared t o payload data. Figure 8
provides an illustration of a repetition procedure in accordance with the present technique where a
larger num ber instances of signals representing payload data are required to be accumulated
compared to signals representing control data. In Figure 8, three repetitions of signals forming the
PDCCH 801 and representing user device control data are required to be stored and accumulated
whereas five instances of the signals representing the payload 802 data are required. Whilst the
signals received across the PDCCH are being accumulated, knowledge of the location of the signals
representing the payload data with the second bandwidth is unknown and therefore the receiver of
the user device stores and accumulates signals from the entirety or a significant proportion of the
second bandwidth 702 of su bframes 803. Once the control data has been detected and estimated
from the accumulated signals representing the control data, and the location of the signals
representing the payload data known, the receiver commences storing and accumulating only the
signals from the specified location within the second bandwidth of frames 804. In some examples,
because of the time taken t o estimate the control data from the accumulated and com bined control
signals, the receiver may continue t o buffer signals from the entirety of the second bandwidth until
su bframe three of Figure 8 because knowledge of the location of the payload data signals within the
predetermined bandwidth is not known until after the commencement of the PDSCH of frame three.
Figure 9 provides an illustration of a repetition procedure in accordance with an example of
the present technique where additional control information is transmitted outside of the PDCCH, for
example, in an enhanced PDCCH (ePDCCH) in an LTE system. In this case the ePDCCH 901 may be
located within the second bandwidth 702 so that the user device is able to receive the control data
represented by signals transmitted over the ePDCCH without having to receive signals transmitted
across the entirety or a su bstantial portion of the first bandwidth. The ePDCCH may convey
additional control data required in order to detect and estimate the user device payload data and
therefore may be required to be detected and estimated prior t o detection and estimation of the
payload data in the second bandwidth. Alternatively, the ePDCCH may convey information relating
to uplink criteria and therefore should be received in a similar manner to signals transmitted over
the PDSCH.
As previously described, the user device may require an indication of when signal repetition
is set to commence so that the appropriate signals from the PDCCH and PDSCH can be stored and
accu mulated. Such an indication may be transmitted at a low code rate and mod ulation order so
that the proba bility that it can be received without the need for repetition is maximised. However, in
embodiments where an indication is not provided or cannot be relia bly detected and estimated, a
buffering procedure as previously described and shown in Figure lOmay be used. In Figure 10,
buffering of the signals transmitted across the PDCCH and the predetermined bandwidth 702 begins
at 1001. Three instances of the signals representing the user device control data and payload data
are required to be accumulated and therefore the next three su bframes are then buffered in the
window 1002. The window then moves or slides by one su bframe as each su bframe is received as
represented by windows 1003 and 1004, where a movement of one su bframes represents the oldest
received signals from a su bframe being replaced in the buffer memory by relevant signals received
from the most recent su bframe. During the window represented by 1004, three instances of the
PDCCH and PDSCH signals that include signals representing the user device control data 1005 and
payload data 1006 have been stored and accu mulated. Therefore the control data and the payload
data may be detected and estimated, and the current accumulation procedure halted. The point at
which a required num ber of repetitions have been stored may be indicated by the accumulated
signals passing an amplitude threshold for example or su bstantially error-free decoding of the
transmitted data.
Although embodiments of the present technique have been described with reference t o the
physical channels PDCCH and PDSCH of an LTE wireless commu nications interface, embodiments
may also be applied to other physical channels of an LTE system, either ind ividually or in
com bination with other channels. Likewise, although embodiments have been described with
reference to a LTE systems and wireless access interfaces, embodiments of the present technique
are not limited to LTE systems and may be implemented in any systems which have wireless access
resources divided into temporal periods and or resources which may be divided up for the provision
of a multiple access interface. Similarly, different repetition techniques and or com bining techniques
to those described above may also be used in conjunction with embodiments of the present
technique.
Various further aspects and features of the present technique are defined in the appended
claims and various com binations of the features of the dependent claims may be made with those of
the independent claims other than the specific combinations recited for the cla im dependency.
Modifications may also be made to the embodiments hereinbefore described without departing
from the scope of the present invention. For instance, although a feature may appear to be
described in connection with particular embodiments, one skilled in the art would recognise that
various features of the described embodiments may be combined in accordance with the disclosure.
The following num bered clauses define further example aspects and features of the present
disclosure:
1. A user device arranged to transmit and t o receive data t o and from an infrastructure
equipment via a wireless access interface, the wireless access interface being provided by the
infrastructure equipment using a plurality of Orthogonal Frequency Division Multiplexing (OFDM)
su bcarriers, the plurality of su bcarriers extending across at least a first bandwidth, the infrastructure
equipment transmitting repeatedly signals representing a same instance of user device payload data
in a second bandwidth, the second bandwidth being less than and within the first bandwidth and
including a su bset of the OFDM su bcarriers, and user device is configured
to receive one or more of the signals repeatedly transmitted across the second bandwidth,
to store in a memory signals representing the repeatedly transmitted signals received across
the second bandwidth,
to com bine the stored signals, and
to detect the user device payload data from the com bined signals, the user device having
been provided with an indication of the second bandwidth.
2. A user device according to clause 1, wherein the infrastructure equ ipment transmits
repeatedly signals representing a same instance of user device control data in the first bandwidth,
the user device control data providing an indication of a location of the signals representing the user
device payload data in the second bandwidth, and the user device is configured
to receive one or more of the repeatedly transmitted signals representing user device
control data across the first bandwidth,
to store in the memory signals representing the repeatedly transmitted received across the
first bandwidth,
to com bine the stored signals representing the repeatedly transmitted signals received
across the first bandwidth, and
to detect the user device control data from the com bined signals representing the
repeatedly transmitting signals received across the first bandwidth, the detection of the user device
payload data from the com bined signals received across the second bandwidth being based on the
indication of the location of the signals representing the user device payload data in the second
bandwidth.
3. A communications system according t o clauses 1 or 2, wherein the wireless access
interface provided by the plurality of OFDM su bcarriers is divided into a plurality of time periods and
the repeated signals representing the user device payload data are transmitted in a same set of
resources of the wireless access interface in a first time period and in a second time period, and the
user device is configured t o receive the user device payload data in the same set of resources of the
wireless access interface in the first time period and in the second time period.
4. A user device according to clause 2, wherein the user device is configured t o receive
the indication of the second bandwidth from the infrastructure equipment prior to receiving the
repeated transmissions of the signals representing the user device control data.
5. A user device according to any of clauses 1 to 4, wherein the user device is
configured to receive user device payload data within a virtual carrier of a predetermined
bandwidth, the second bandwidth being approximately equal t o the predetermined bandwidth, and
the predetermined bandwidth includes a set of the OFDM su bcarriers that is su bstantially similar to
the OFDM su bcarriers that form the su bset of the OFDM su bcarriers included in the second
bandwidth.
6. A user device according to any of clauses 2 to 5, wherein a number of repeated
signals com bined to detect the user device payload data is greater than a number of repeated
signals com bined to detect the user device control data.
7. A user device according to any of clauses 1 to 6, wherein the user device is
compliant with 3GPP LTE.
8. A user device according to any of clauses 1 to 7, wherein the user device is
configured to com bine the stored signals in accordance with an incremental redundancy repetition
scheme or a chase combining scheme.
9. A method of receiving data at a user device arranged t o transmit and to receive data
to and from an infrastructure equipment via a wireless access interface, the wireless access interface
being provided by the infrastructure equ ipment using a plurality of Orthogonal Frequency Division
Multiplexing (OFDM) su bcarriers, the plurality of su bcarriers extending across at least a first
bandwidth, the infrastructure equipment repeatedly transmitting signals representing a same
instance of user device payload data in a second bandwidth, the second bandwidth being less than
and within the first bandwidth and including a su bset of the OFDM su bcarriers, the method
comprising
receiving one or more of the repeatedly transmitted signals across the second bandwidth,
storing in a memory signals representing the repeatedly transmitted signals received across
the second bandwidth,
com bing the stored signals, and
detecting the user device payload data from the com bined signals, the user device having
been provided with an indication of the second bandwidth.
10. A method according t o cla use 9, wherein the infrastructure equipment transmits
repeated ly signals representing a same instance of user device control data in the first bandwidth,
the user device control data providing an indication of a location of the signals representing the user
device payload data in the second bandwidth, the method comprising
receiving one or more of the repeatedly transmitted signals representing user device control
data across the first bandwidth,
storing in the memory signals representing the repeatedly transmitted received across the
first bandwidth,
com bining the stored signals representing the repeatedly transmitted signals received across
the first bandwidth, and
detecting the user device control data from the combined signals representing the
repeatedly transmitting signals received across the first bandwidth, the detection of the user device
payload data from the com bined signals received across the second bandwidth being based on the
indication of the location of the signals representing the user device payload data in the second
bandwidth.
11. A method according t o cla uses 9 or 10, wherein the wireless access interface
provided by the plurality of OFDM su bcarriers is divided into a plurality of time periods and the
repeated signals representing the user device payload data are transmitted in a same set of
resources of the wireless access interface in a first time period and in a second time period, the
method comprising
receiving the user device payload data in the same set of resources of the wireless access
interface in the first time period and in the second time period.
12. A method according t o cla use 10, the method comprising
receiving the indication of the second bandwidth from the infrastructure equipment prior to
receiving the repeated transmissions of the signals representing the user device control data.
13. A method according t o any of clauses 9 to 12, the method comprising
receiving user device payload data within a virtual carrier of a predetermined bandwidth,
the second bandwidth being approximately equal to the predetermined bandwidth, and the
predetermined bandwidth includes a set of the OFDM su bcarriers that is su bstantially simila r to the
OFDM su bcarriers that form the su bset of the OFDM su bcarriers included in the second bandwidth.
14. A user device according to any of clauses 10 to 13, the method comprising
com bining a greater num ber of repeated signals to detect the user device payload data than to
detect the user device control data.

Claims
1. A user device arranged to transmit and t o receive data t o and from an infrastructure
equipment via a wireless access interface, the wireless access interface being provided by the
infrastructure equipment using a plurality of Orthogonal Frequency Division Multiplexing (OFDM)
su bcarriers, the plurality of su bcarriers extending across at least a first bandwidth, the infrastructure
equipment transmitting repeatedly signals representing a same instance of user device payload data
in a second bandwidth, the second bandwidth being less than and within the first bandwidth and
including a su bset of the OFDM su bcarriers, and user device is configured
to receive one or more of the signals repeatedly transmitted across the second bandwidth,
to store in a memory signals representing the repeatedly transmitted signals received across
the second bandwidth,
to com bine the stored signals, and
to detect the user device payload data from the com bined signals, the user device having
been provided with an indication of the second bandwidth.
2. A user device as claimed in Claim 1, wherein the infrastructure equipment transmits
repeatedly signals representing a same instance of user device control data in the first bandwidth,
the user device control data providing an indication of a location of the signals representing the user
device payload data in the second bandwidth, and the user device is configured
to receive one or more of the repeatedly transmitted signals representing user device
control data across the first bandwidth,
to store in the memory signals representing the repeatedly transmitted received across the
first bandwidth,
to com bine the stored signals representing the repeatedly transmitted signals received
across the first bandwidth, and
to detect the user device control data from the com bined signals representing the
repeatedly transmitting signals received across the first bandwidth, the detection of the user device
payload data from the com bined signals received across the second bandwidth being based on the
indication of the location of the signals representing the user device payload data in the second
bandwidth.
3. A communications system as claimed in Claim 1, wherein the wireless access
interface provided by the plurality of OFDM su bcarriers is divided into a plurality of time periods and
the repeated signals representing the user device payload data are transmitted in a same set of
resources of the wireless access interface in a first time period and in a second time period, and the
user device is configured t o receive the user device payload data in the same set of resou rces of the
wireless access interface in the first time period and in the second time period.
4. A user device as described in Claim 2, wherein the user device is configured to
receive the indication of the second bandwidth from the infrastructure equipment prior to receiving
the repeated transmissions of the signals representing the user device control data.
5. A user device as claimed in any of Claims 1 t o 4, wherein the user device is
configured to receive user device payload data within a virtual carrier of a predetermined
bandwidth, the second bandwidth being approximately equal t o the predetermined bandwidth, and
the predetermined bandwidth includes a set of the OFDM su bcarriers that is su bstantially similar to
the OFDM su bcarriers that form the su bset of the OFDM su bcarriers included in the second
bandwidth.
6. A user device as claimed in any of Claims 2 t o 5, wherein a num ber of repeated
signals com bined to detect the user device payload data is greater than a number of repeated
signals com bined to detect the user device control data.
7. A user device as claimed in any of Claims 1 t o 6, wherein the user device is compliant
with 3GPP LTE.
8. A user device as claimed in any of Claims 1 t o 7, wherein the user device is
configured to com bine the stored signals in accordance with an incremental redundancy repetition
scheme or a chase combining scheme.
9. A method of receiving data at a user device arranged t o transmit and to receive data
to and from an infrastructure equipment via a wireless access interface, the wireless access interface
being provided by the infrastructure equ ipment using a plurality of Orthogonal Frequency Division
Multiplexing (OFDM) su bcarriers, the plurality of su bcarriers extending across at least a first
bandwidth, the infrastructure equipment repeatedly transmitting signals representing a same
instance of user device payload data in a second bandwidth, the second bandwidth being less than
and within the first bandwidth and including a su bset of the OFDM su bcarriers, the method
comprising
receiving one or more of the repeatedly transmitted signals across the second bandwidth,
storing in a memory signals representing the repeatedly transmitted signals received across
the second bandwidth,
com bing the stored signals, and
detecting the user device payload data from the com bined signals, the user device having
been provided with an indication of the second bandwidth.
10. A method as claimed in Claim 9, wherein the infrastructure equipment transmits
repeated ly signals representing a same instance of user device control data in the first bandwidth,
the user device control data providing an indication of a location of the signals representing the user
device payload data in the second bandwidth, the method comprising
receiving one or more of the repeatedly transmitted signals representing user device control
data across the first bandwidth,
storing in the memory signals representing the repeatedly transmitted received across the
first bandwidth,
com bining the stored signals representing the repeatedly transmitted signals received across
the first bandwidth, and
detecting the user device control data from the combined signals representing the
repeatedly transmitting signals received across the first bandwidth, the detection of the user device
payload data from the com bined signals received across the second bandwidth being based on the
indication of the location of the signals representing the user device payload data in the second
bandwidth.
11. A method as claimed in Claims 9 or 10, wherein the wireless access interface
provided by the plurality of OFDM su bcarriers is divided into a plu rality of time periods and the
repeated signals representing the user device payload data are transmitted in a same set of
resources of the wireless access interface in a first time period and in a second time period, the
method comprising
receiving the user device payload data in the same set of resources of the wireless access
interface in the first time period and in the second time period.
12. A method as claimed in Claim 10, the method comprising
receiving the indication of the second bandwidth from the infrastructure equipment prior to
receiving the repeated transmissions of the signals representing the user device control data.
13. A method as claimed in any of Claims 9 to 12, the method comprising
receiving user device payload data within a virtual carrier of a predetermined bandwidth,
the second bandwidth being approximately equal to the predetermined bandwidth, and the
predetermined bandwidth includes a set of the OFDM su bcarriers that is su bstantially simila r to the
OFDM su bcarriers that form the su bset of the OFDM su bcarriers included in the second bandwidth.
14. A user device as claimed in any of Cla ims 10 to 13, the method comprising
com bining a greater num ber of repeated signals to detect the user device payload data than to
detect the user device control data.
15. A user device as su bstantially hereinbefore described with reference t o the
accompanying drawings.