FIELD OF THE INVENTION

The invention relates particularly, but not exclusively, to an improved method and device for determining that a signal received on an uplink (UL) at an Uplink Control Information (UCI) receiver in a wireless communications system comprises a linear block encoded signal. The invention also relates to a method and device for improved detection of discontinuous transmission (DTX) on a UL at a UCI receiver particularly for small block encoded signals.

BACKGROUND OF THE INVENTION

In long-term evolution (LTE) communications systems, in a downlink (DL), a data payload is carried by transport blocks which are encoded into codewords which are sent over a DL physical data channel called the Physical Downlink Shared Channel (PDSCH). The scheduling information of the PDSCH codeword(s), including its resource allocation in the subframe and its modulation and coding scheme, is included in the physical control channel, called the Physical Downlink Control Channel (PDCCH). Generally, the receiving UE decodes the messages in PDCCH and, where it finds that a PDSCH has been assigned to it, it decodes the PDSCH codeword(s) according to the scheduling information decoded from the PDCCH.

In order to prevent the loss of transport blocks, LTE has adopted the Hybrid Automatic Repeat Request (HARQ) scheme. In the physical layer of E-UTRA, HARQ is implemented both in the UL and the DL. The acknowledgement message in E-UTRA is denoted as HARQ-ACK.

HARQ-ACK may be transmitted by the UE in response to certain PDSCH transmissions and includes one or several acknowledgements, either positive (ACK) or negative (NACK) in response to transport blocks transmitted in the DL. HARQ-ACK may be transmitted on one of the physical channels Physical Uplink Control Channel (PUCCH) or PUSCH.

If the eNodeB (base station (BS)) detects ACK instead of DTX, a so called ACK false detection, the eNodeB will erroneously consider the corresponding DL transport block as correctly received. Since the transport block has not been correctly received by the UE, corresponding data will not be passed to the Medium Access Control (MAC) layer and from the MAC layer to the Radio Link Control (RLC) layer. Data will hence be missing in the RLC layer. This will cause ARQ retransmissions in the RLC layer which introduce delay and possibly large retransmissions which is very undesirable. Also, if a NACK is detected erroneously that in reality is DTX, the eNodeB will retransmit the packet in such a way that the UE will not be capable of decoding it.

As already indicated, a problem arises when the UE is not aware of the presence of the PDSCH assigned to it if it fails to decode the PDCCH successfully. In this case the user equipment will not generate ACK/NACK information. This situation has been well recognized and the UE response in such case is DTX, that is, neither an ACK nor a NACK signal is transmitted to the eNodeB. Since the eNodeB has no prior knowledge of whether the UE has failed to detect the PDCCH, it expects or deems, that the symbols of the predetermined positions are ACK/NACK symbols and extracts them for the ACK/NACK decoder to decode.

If the eNodeB disregards the possibility of DTX, either an ACK or NACK message will be returned by the ACK/NACK decoder to a higher layer upon the decoding of the extracted symbols, which are, in fact, conveying no information. In general, both ACK and NACK messages are equally likely to be returned.

The consequence of wrongly detecting a DTX as an ACK is more adverse to the system performance than wrongly detecting a DTX into a NACK.

Similarly, in 5G (or new radio (NR)) wireless communication systems, a message feedback scheme is also used for re-transmission control. ACK or NACK (AN) signals are used to indicate whether the signal is received successfully or not by the UE and whether the BS needs to retransmit the data. If the UE misses a DL control signal, the UE may encounter DTX in DL and the UE will not send any message back to the BS. However, the BS needs to detect one of three possible feedback states, i.e. ACK, NACK or DTX, for rearranging a next transmission to the UE.

FIG. 1illustrates a method by which UL signals from the UE to the BS control transmission of payload control data and payload data on the DL from the BS to the UE. In the example ofFIG. 1, it can be seen that, in response to a first “DL control for payload allocation #1” message from the BS to the UE, the UE, in this instance, responds with a UCI “NACK” message. The NACK message is received by the UCI receiver at the BS and, as a consequence, the BS is configured to retransmit to the UE the first “DL control for payload allocation #1” message and its associated first “DL payload data #1” message. In this example, the UE then returns a UCI “ACK” message to the UCI receiver in response to the retransmitted control signal message and, as a consequence, the BS is configured to then transmit to the UE the second “DL control for payload allocation #2” message and its associated second “DL payload data #2” message (not shown inFIG. 1).FIG. 1therefore illustrates how data is retransmitted by the BS to the UE when the UE indicates that is has not successfully received a DL data control message.

In contrast,FIG. 2illustrates what may happen when the UE misses a DL data control message. In this example, the UE has missed the first “DL control for payload allocation #1” message and consequently sends no ACK/NACK message back to the BS in response. This scenario represents a DTX condition. The UCI receiver at the BS only receives noise but processes this as though it comprises a UL UCI signal with the result that, in this example, the UCI falsely detects or determines receipt of an ACK message from the UE and thus outputs a false ACK message. This causes the BS to commence a new control and payload data transmission in response to the false ACK message, e.g. “DL control for payload allocation #2”, etc.

It will be understood that, in the example illustrated byFIG. 2where the UCI receiver has no DTX detection or determination capability, the probability of the UCI receiver falsely detecting an ACK message is 50% with the remaining 50% of occasions resulting in a false NACK message. A false NACK message is less troublesome than a false ACK message but is still undesirable.

It is clear from the example ofFIG. 2that there is room for improvement in detecting or determining ACK or NACK messages from the UE at the UCI receiver and in distinguishing between ACK/NACK messages and DTX conditions.

CN105262568 relates to ACK/NACK and DTX detection in a wireless communication system where the DTX status threshold is calculated based on the statistics of signal-to-noise ratio (SNR). However, it can be challenging to obtain accurate noise estimations.

CN102740316 relates to a method for detecting an uplink DTX state. The method comprises receiving data information from uplink user equipment of the current cell; calculating a confidence value corresponding to the data information, wherein the confidence value is used for reflecting the accuracy of data information decoding carried out by a receiving terminal; comparing the confidence value with a preset DTX judgment threshold; and determining whether the uplink user equipment is in the DTX state or not according to a comparative result. Here, the preset DTX judgment threshold must change for different channel conditions and thus determination of the DTX judgment threshold requires considerable computational effort.

U.S. Pat. No. 8,850,285 relates to ACK/NACK/DTX detection in a wireless communication system disclosing a channel decoding block which receives a signal from the UE and produces a decoded ACK/NACK information vector.

U.S. Pat. No. 8,315,185 relates to ACK/NACK detection in an LTE wireless communication system. The ACK/NACK detector has a soft decoder and decision-maker. A threshold value is used to determine whether the transmitted signal from the UE contains an ACK/NACK transmission when the threshold value is met. If the threshold value is not met, the transmission is determined to be DTX. The threshold value is based on a power estimate of soft data bits.

For 5G UCI, 3GPP TS 38.212 requires the support of two types of channel codes, namely polar code and small block code as illustrated respectively byFIGS. 3 and 4. Polar code relates to the situation where the number of payload bits is greater than 11. Small block code relates to the situation where the number of payload bits is equal to or less than 11.

As shown inFIG. 3, in a conventional polar code-based receiver, a cyclic redundancy check (CRC) may assist in detecting whether or not DTX occurs. The output from the polar code decoder comprises UCI bits but the CRC check function (module) enables the polar code-based receiver to distinguish between DTX on the one hand and UCI bits indicative of ACK or NACK on the other hand.

InFIG. 4which shows a conventional small block code-based receiver where a CRC function is not available, incorrect detection of the ACK, NACK, or DTX signals leads to a waste of resources for retransmission and/or a loss of data packets. In the conventional small block code-based receiver where CRC is not available, ACK and NACK each issue with 50% probability where the UE misses a DL control message and transmits nothing to the UE such that the BS receives only noise. In the small block code-based receiver, the output from the small block code decoder are assumed to be UCI bits leading to possible false ACK or false NACK outcomes. In other word, there is no means for distinguishing between DTX on the one hand and UCI bits indicative of ACK or NACK on the other hand.

What is desired is a method for detecting acknowledgment (ACK), negative acknowledgment (NACK) and discontinuous transmission (DTX) signals more accurately in wireless communication systems. What is also desired is a method of improving detection of DTX on a UL at a UCI receiver and/or a method of determining that a signal received on a UL at a UCI receiver comprises a linear block encoded signal.

OBJECTS OF THE INVENTION

An object of the invention is to mitigate or obviate to some degree one or more problems associated with known methods of determining that signals received on a UL at a UCI receiver comprise linear block encoded signals.

The above object is met by the combination of features of the main claims; the sub-claims disclose further advantageous embodiments of the invention.

Another object of the invention is to provide an improved method of detecting DTX on a UL at a UCI receiver especially for small block encoded signals.

Another object of the invention is to provide an improved UCI receiver and/or UCI decoder.

One skilled in the art will derive from the following description other objects of the invention. Therefore, the foregoing statements of object are not exhaustive and serve merely to illustrate some of the many objects of the present invention.

SUMMARY OF THE INVENTION

The invention concerns a method for processing a signal received at an uplink control information (UCI) receiver in a wireless communication system. The method comprises processing a signal received on an uplink (UL) at said UCI receiver to transform said received signal into a likelihood calculation of possible transmitted codewords (θ1. . . θi . . . θN). The method includes determining a maximum magnitude θmaxvalue from said likelihood calculation of possible transmitted codewords (θ1. . . θi . . . θN) and then comparing said θmaxvalue to a selected, calculated or predetermined scaled threshold c·τ where τ is the threshold and c is a scaling factor for the threshold T. The comparison is such that, where θmax>c·τ, it is determined that the signal received on the UL at said UCI receiver comprises a linear block encoded signal. Preferably, where θmax≤c·τ, a discontinuous transmission (DTX) signal is outputted.

In some cases, the scaling factor c can be omitted such that the method then comprises comparing said θmaxvalue directly to a unscaled threshold τ wherein, for θmax>τ, it is determined that the signal received on the UL comprises a linear block encoded signal but, for θmax≤τ, a discontinuous transmission (DTX) signal is outputted.

Described is a device for processing a signal received at an uplink control information (UCI) receiver in a wireless communication system. The device comprises a receiver in a wireless communication system which is configured to process a signal received on an uplink (UL) at said UCI receiver to transform said received signal into a likelihood calculation of possible transmitted codewords (θ1. . . θi . . . θN). The likelihood calculation of possible transmitted codewords (θ1. . . θi . . . θN) may comprise a multi-dimensional discrete Fourier transform (DFT) (θ1. . . θi . . . θN) of said received signal. The multi-dimensional may be formed as a Hadamard Transform. The UCI receiver is configured to determine a maximum magnitude θmaxvalue from said likelihood calculation of possible transmitted codewords (θ1. . . θi. . . θN) and then compare said θmaxvalue to a selected, calculated or predetermined scaled threshold c·τ where τ is the threshold and c is a scaling factor for the threshold τ such that, where θmax>c·τ, it is determined that the signal received on the UL at said UCI receiver comprises a linear block encoded signal. In some cases, the scaling factor c can be omitted.

In a first main aspect, the invention provides a method of processing a signal received at an uplink control information (UCI) receiver in a wireless communication system, the method comprising: processing a signal received on an uplink (UL) at said UCI receiver to transform said received signal into a likelihood calculation of possible transmitted codewords (θ1. . . θi. . . θN); determining a maximum magnitude θmaxvalue from said likelihood calculation of possible transmitted codewords (θ1. . . θi. . . θN); and comparing said θmaxvalue to a selected, calculated or predetermined scaled threshold c·τ where c is a scaling factor for the threshold τ and said scaled threshold c·τ is obtained by multiplying the threshold τ by the scaling factor c, the comparison being such that, where θmax>c·τ, the method comprises determining that the signal received on the UL at said UCI receiver comprises a linear block encoded signal.

Preferably, where θmax≤c·τ, the method comprises outputting a discontinuous transmission (DTX) signal.

In one embodiment, the method includes the steps of: generating UCI bits based on a sign and an index of said θmaxvalue; and, where θmax>c·τ, outputting an acknowledgement (ACK) message or a negative-acknowledgement (NACK) message based on said UCI bits.

In another embodiment, the scaling factor c is omitted such that the step of comparing said θmaxvalue to the threshold τ comprises comparing said θmaxvalue directly to the threshold τ. For θmax>τ, the method includes determining that the signal received on the UL at said UCI receiver comprises a linear block encoded signal.

In this embodiment, where θmax≤τ, the method preferably comprises outputting a discontinuous transmission (DTX) signal.

In this embodiment, the method preferably includes the steps of: generating UCI bits based on a sign and an index of said θmaxvalue; and, where θmax>τ, outputting an acknowledgement (ACK) message or a negative-acknowledgement (NACK) message based on said UCI bits.

In a second main aspect, the invention provides an uplink control information (UCI) receiver in a wireless communication system, the receiver comprising: a memory storing machine-readable instructions; and a processor for executing the machine-readable instructions such that, when the processor executes the machine-readable instructions, it configures the receiver to implement the steps of the first main aspect of the invention.

In a third main aspect, the invention provides a non-transitory computer-readable medium storing machine-readable instructions, wherein, when the machine-readable instructions are executed by a processor, they configure the processor to implement the steps of the first main aspect of the invention.

The summary of the invention does not necessarily disclose all the features essential for defining the invention; the invention may reside in a sub-combination of the disclosed features.

The forgoing has outlined fairly broadly the features of the present invention in order that the detailed description of the invention which follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It will be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the invention.

