WO2015018617A1 - User device for communcating data and method - Google Patents
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- WO2015018617A1 WO2015018617A1 PCT/EP2014/065296 EP2014065296W WO2015018617A1 WO 2015018617 A1 WO2015018617 A1 WO 2015018617A1 EP 2014065296 W EP2014065296 W EP 2014065296W WO 2015018617 A1 WO2015018617 A1 WO 2015018617A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/0001—Arrangements for dividing the transmission path
- H04L5/0003—Two-dimensional division
- H04L5/0005—Time-frequency
- H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
- H04L1/04—Arrangements for detecting or preventing errors in the information received by diversity reception using frequency diversity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/08—Arrangements for detecting or preventing errors in the information received by repeating transmission, e.g. Verdan system
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/70—Services for machine-to-machine communication [M2M] or machine type communication [MTC]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/20—Control channels or signalling for resource management
- H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/50—Allocation or scheduling criteria for wireless resources
- H04W72/51—Allocation or scheduling criteria for wireless resources based on terminal or device properties
Definitions
- Fourth generation mobile telecommunication systems such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) architecture are able to support more sophisticated services than simple voice and messaging services offered by previous generations of mobile telecommunication systems.
- LTE Long Term Evolution
- 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 available 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 to increase rapidly.
- MTC machine type communication
- 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 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 to 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 combined 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.
- repetition may be useful for example, when it is not possible to alter coding rates or modulation 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 capabilities of intended receiving devices are limited.
- a machine type communications (MTC) device may be unable to perform complex decoding procedures but can receive multiple instance of signal and combine 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 combine when the location of signals representing the user device payload data within the second bandwidth is not yet known.
- MTC machine type communications
- 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 combined to increase the likelihood of correctly recovering the user data.
- the repeated transmission of the signals representing the user data is a repetition of the same signals.
- 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.
- Repeating of signals representing the user device payload data in the same set of resources within different time period means that the channel over the signals propagate may be substantially similar and therefore may simplify the combining 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.
- 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 to receive payload data compared to having a second bandwidth which is separate from the virtual carrier.
- MTC machine type communication
- 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 subframes
- 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 subframes where signal repetition is implemented
- Figure 7 provides a schematic diagram of LTE subframes where signal repetition is implemented in accordance with an embodiment of the present technique
- Figure 8 provides a schematic diagram of LTE subframes where signal repetition is implemented in accordance with an embodiment of the present technique
- Figure 9 provides a schematic diagram of LTE subframes where signal repetition is implemented in accordance with an embodiment of the present technique.
- FIG. 1 provides a schematic diagram of a mobile communications system 100 for transmitting and receiving data to and from one or more user devices, where the communications system may for example operate in accordance with 3GPP Long Term Evolution (LTE).
- the communications system comprises infrastructure equipment 101 such as a base station or enhanced nodeB (eNodeB) which forms part of a mobile communications 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.
- MTC machine type communication
- the infrastructure equipment transmits signals representing the data to the one or more user devices.
- 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
- 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 subcarriers where the su bcarriers form in the time domain OFDM symbols that convey signals which represent data to be transmitted to the user devices.
- OFDM orthogonal frequency division multiplexing
- 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 communicate in the downlink (from
- infrastructure equipment to user device infrastructure equipment to user device
- uplink from user device to infrastructure equipment
- user plane data conveys user device payload data.
- Figure 2 provides a schematic diagram of a simplified receiver that may be found in a user device configured to receive and transmit data in the communications system of Figure 1.
- 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 suitable for the baseband frequencies.
- a synchroniser 204 is then configured to 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.
- FIG. 3 provides a simplified example of downlink resource allocation, which may for example being applicable in an LTE system.
- the downlink resources are temporally divided into periods referred to as su bframes 301 where a time period referred to as a radio frame may be formed from 10 subframes and the subframes may be 1ms in duration.
- the downlink resources are divided in frequency into a plurality of subcarriers, where the number of subcarriers may vary between approximately 128 and 2048 dependent upon the bandwidth of the downlink resources, where possible downlink bandwidths may include for example 1.25MHz, 2.5M Hz, 5MHz, 10M Hz, 15MHz and 20M Hz.
- Each subframe may be further divided in time into two 0.5ms slots where a slot comprising 12 subcarriers may be referred to as a resource block.
- Each subframe 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 subcarriers, slots and timing within the subframes, 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 to 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.
- PDSCH physical downlink shared channel
- 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
- PDCCH physical downlink control channel
- PDSCH physical downlink shared channel
- 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 subframe in order establish whether it has been allocated resources in the PDSCH of the corresponding subframe.
- 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 subsequently estimate the user payload data from the received signals.
- the resources 306 in the PDSCH allocated to a user device may not extend over all the subcarriers in the subframe and/or over the full temporal length of the PDSCH in the subframe. This, along with the control data conveyed by signals transmitted across the PDCCH allows for the allocation of resources in the PDSCH to 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 number of factors, for instance, knowledge of the location of the signals representing the payload data in a subframe 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.
- 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 unable 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.
- 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 subsequent subframe, 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 variable channels due to mobility for instance, because poor channel conditions may improve in the near future. Consequently, subsequent 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.
- the above described procedure is unlikely to be sufficiently robust.
- 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 subframes where an example 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 subframes or frames.
- the signals may be in a substantially similar position or in substantially similar set of resources of the wireless access interface in each of the subframes or frames so that they propagate over a substantially similar channel.
- the repeated signals may be transmitted in different resources in each subframe or frame where differences in channel across which the signals are transmitted are mitigated for example by equalisation.
- the signals may be repeated within a same subframe or frame.
- the receiver of the user device is then configured 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 combines the stored signals, by summation or averaging for example, so that the relative received strength of the combined signals representing the user device control data and payload data is increased or additional coding bits are available for data estimation and correction.
- the user device then proceeds to 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.
- 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 indication of the location in the PDSCH of signals representing the user device's payload data 404.
- the user device stores and accumulates the signals received from the indicated location 404 of the PDSCH in the next three subframes.
- the user device then recovers an estimate of its payload data from the accumulated PDSCH signal at 405.
- 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 example user device receiver which is configured to receive repeated data transmissions.
- the structure of the receiver is substantially 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 number of repeated signals have been received or when the accumulated signals achieve an amplitude, via summation for example, sufficient to enable reliable detection and estimation of the data to be achieved.
- the exact process by which the received signals are combined 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 to configure the elements to store and accumulate signals from the relevant portions of the PDSCH as indicated by recovered control data.
- 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.
- 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 combined after initial detection and estimation has taken place, an additional estimator stage(s) may be required or the organisation of the receiver adapted accordingly.
- the user device may require an indication of commencement of the repetition so that it can begin to store the relevant received signals.
- 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 number 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 to the correlation between the repeated signals representing the user data and the lack of correlation between the portions of the frames or subframes which are not repeated i.e.
- Another alternative is for the infrastructure to continue to 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.
- the repetition scheme depicted in Figure 4 provides a number of advantages, there are also associated costs. For example, 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 communication 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.
- control data indicating where user device payload data is located in the corresponding PDSCH there may have to 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 to be transmitted or the corresponding resources not used by another user device because the control data corresponding to 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 to 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 to the commencement of any repetition.
- the entirety of the frames or subframes may have to be repeated in a substantially identical manner. This therefore decreases flexibility and further reduces efficiency.
- 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 to be accumulated at the user device. Consequently, because 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 subframes is large i.e.
- the payload data may be recovered.
- the subframes are 1ms in duration, a 200 subframe delay may result in a delay of 0.2s, which may be unacceptable in some scenarios or to some user devices.
- user devices may have to be in a receiving mode for a significant period of time as opposed to 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 number of different methods for accumulating and combining received repeated signals.
- Two example repetition techniques are chase combining and incremental redundancy, which may be implemented as part of hybrid ACK procedures.
- Chase combining 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 combining may be viewed as increasing the signal-to-interference-plus -noise ratio (SINR) of the received signal.
- SINR signal-to-interference-plus -noise ratio
- 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.
- methods that may be used to accumulate or combine the received repeated signals. For example, in chase combining stored sampled baseband signals that represent the repeated signals may be combined via equal- gain combining or maximum-ratio combining. The combining may also be performed either pre- equalisation or post-equalisation.
- 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, combining of baseband signals may not be possible due to the differing repeated signals and therefore combining of signals representing soft or hard decisions may be more appropriate.
- the aforementioned repetition and combining methods are merely examples and any suitable 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 to be performed at a frequency and with a number of quantisation levels that are sufficient to 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 (SNR).
- SNR signal-to-noise ratio
- signals are combined post-equalisation and or -post-demodulation, then memory requirements may be reduced.
- 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 symbol in memory corresponds to one received symbol, whereas in chase combing one symbol in memory may be a summation of multiple repeated symbols.
- 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.
- estimation of the data contained therein may be performed at any point after reception, independent of the combining method. This approach is possible by virtue of information on the location of control information in frame or subframe 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.
- Figure 6 whilst the signals transmitted across the PDCCH 601 are being accumulated all the signals transmitted across the PDSCH 602 are buffered.
- the payload data may be detected and estimation from the buffered accumulated 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.
- Narrow Bandwidth Signal Repetition may reduce acquisition delays, it requires a significant amount of memory in order to store and accumulate all or a substantial 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.
- Figure 7 illustrates an example embodiment of a repetition procedure 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.
- signals representing the user device payload data are transmitted using chase combining 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 subframe 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.
- 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
- the second bandwidth could be formed by a Virtual carrier arrangement.
- 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 subdivides frequency spectrum in a similar manner to OFDM.
- data transmitted on the virtual carrier can be received and decoded without needing to process the full bandwidth of the downlink OFDM host carrier.
- 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 reliability, 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
- a sufficient number 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. Subsequently, if a sufficient number 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 to 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 substantial portion of the PDSCH. Therefore improvements in the speed of data acquisition may be achieved compared to the procedure described with reference to Figure 4, whilst also reducing the memory requirements compared to the procedure described with reference to Figure 6. For example, if the PDSCH is 128 subcarriers in bandwidth and the predetermined bandwidth is 12 subcarriers, 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 numbers of repetitions and use of the reception techniques described above, coverage of a mobile
- communications network may be extended to areas where user devices receive a weak signal which would normally 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 example which require both their costs and energy consumption to be reduced and therefore may not be suited to existing repetition techniques.
- the second bandwidth may be hardcoded into repetition compatible user devices.
- the infrastructure equipment may be configured to select an appropriate second bandwidth based on for example resource allocation demands, channel conditions, the number of device requiring repetition etc.
- the second bandwidth may be equivalent to or substantially similar to a predetermined bandwidth of a virtual carrier (VC), which has been proposed in order to simplify the operation of MTC devices.
- VC virtual carrier
- 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.
- 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 subframe.
- the second bandwidth may be defined relative to the first bandwidth or the bandwidth of the PDSCH of each subframe. In such an embodiment the number of subcarriers in a radio frame or subframe or even OFDM symbol to OFDM symbol may change without the infrastructure having to re signal the second bandwidth.
- the second bandwidth may be defined as subcarriers 36 to 60 or the subcarriers 5/8xS t to 6/8xS t where S t is the total number of subcarriers.
- S t is the total number of subcarriers.
- control information required to 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 subframe.
- 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.
- a larger number of instances of signals representing payload data may be required to be received compared to signals representing control data if the payload data is to be detected and estimated accurately.
- control data may be transmitted with lower coding rates and lower order modulations schemes compared to payload data.
- Figure 8 provides an illustration of a repetition procedure in accordance with the present technique where a larger number 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.
- the receiver of the user device 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 subframes 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.
- the receiver may continue to buffer signals from the entirety of the second bandwidth until subframe 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.
- 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 substantial 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 to detection and estimation of the payload data in the second bandwidth.
- the ePDCCH may convey information relating to uplink criteria and therefore should be received in a similar manner to signals transmitted over the PDSCH.
- 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 accumulated.
- Such an indication may be transmitted at a low code rate and modulation order so that the probability that it can be received without the need for repetition is maximised.
- 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 subframes are then buffered in the window 1002.
- the window then moves or slides by one subframe as each subframe is received as represented by windows 1003 and 1004, where a movement of one subframes represents the oldest received signals from a subframe being replaced in the buffer memory by relevant signals received from the most recent subframe.
- a movement of one subframes represents the oldest received signals from a subframe being replaced in the buffer memory by relevant signals received from the most recent subframe.
- 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 accumulated. 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 number of repetitions have been stored may be indicated by the accumulated signals passing an amplitude threshold for example or substantially error-free decoding of the transmitted data.
- 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.
- different repetition techniques and or combining techniques to those described above may also be used in conjunction with embodiments of the present technique.
- 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) subcarriers, the plurality of subcarriers 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 subset of the OFDM subcarriers, and user device is configured
- OFDM Orthogonal Frequency Division Multiplexing
- a user device 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
- the detection of the user device payload data from the combined 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.
- a communications system according to clauses 1 or 2, wherein the wireless access interface provided by the plurality of OFDM subcarriers 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.
- a user device 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.
- a user device 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 subcarriers that is substantially similar to the OFDM subcarriers that form the subset of the OFDM subcarriers included in the second bandwidth.
- a number of repeated signals combined to detect the user device payload data is greater than a number of repeated signals combined to detect the user device control data.
- a user device according to any of clauses 1 to 6, wherein the user device is compliant with 3GPP LTE.
- a user device configured to combine the stored signals in accordance with an incremental redundancy repetition scheme or a chase combining scheme.
- OFDM Orthogonal Frequency Division Multiplexing
- the detection of the user device payload data from the combined 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.
- a method according to clause 10 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.
- the predetermined bandwidth includes a set of the OFDM subcarriers that is substantially similar to the OFDM subcarriers that form the subset of the OFDM subcarriers included in the second bandwidth.
- a user device according to any of clauses 10 to 13, the method comprising combining a greater number of repeated signals to detect the user device payload data than to detect the user device control data.
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Abstract
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EP14739461.3A EP3031157B1 (en) | 2013-08-06 | 2014-07-16 | User device for communicating data and method |
JP2016532292A JP6485816B2 (en) | 2013-08-06 | 2014-07-16 | User equipment and method for communicating data |
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KR1020167003063A KR20160040558A (en) | 2013-08-06 | 2014-07-16 | User device for communicating data and method |
EP20190037.0A EP3767856A1 (en) | 2013-08-06 | 2014-07-16 | User device for communicating data and method |
US15/953,862 US10560231B2 (en) | 2013-08-06 | 2018-04-16 | User device for communicating data and method |
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US20180234218A1 (en) | 2018-08-16 |
US20160149677A1 (en) | 2016-05-26 |
KR20160040558A (en) | 2016-04-14 |
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US9973308B2 (en) | 2018-05-15 |
JP6485816B2 (en) | 2019-03-20 |
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CN105453470B (en) | 2019-05-03 |
JP2016534613A (en) | 2016-11-04 |
CA2919920A1 (en) | 2015-02-12 |
EP3031157A1 (en) | 2016-06-15 |
TWI663857B (en) | 2019-06-21 |
CN105453470A (en) | 2016-03-30 |
EP3031157B1 (en) | 2020-09-09 |
TW201513617A (en) | 2015-04-01 |
CA2919920C (en) | 2021-10-26 |
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