INCORPORATED BY REFERENCE

Applicant's pending utility patent application Ser. No. 16/254,964 filed on 23 Jan. 2019 entitled “Method and an Apparatus for Improving a Determination of HARQ-ACK Messages in a Wireless Communications System”, applicant's pending utility patent application Ser. No. 16/827,883 filed on 24 Mar. 2020 entitled “An Improved Method and Device for Detecting Discontinuous Transmission (DTX) for Small Block Encoded Signals”, applicant's pending utility patent application Ser. No. 16/922,150 filed on 7 Jul. 2020 entitled “Method and an Apparatus for Physical Uplink Control Channel (PUCCH) Discontinuous Transmission (DTX) Determination in a Wireless Communications System”, and applicant's pending utility patent application Ser. No. 17/141,725 filed on 5 Jan. 2021 entitled “A Method and Device For Detecting Partial Discontinuous Transmission (DTX) Using Soft Bits Correlation” are each incorporated herein by way of reference.

FIELD OF THE INVENTION

The invention relates particularly, but not exclusively, to an improved method and device for detection of discontinuous transmission (DTX) on an uplink (UL) at an uplink control information (UCI) receiver device in a wireless communication network using channel estimation data. More specifically, the invention relates to Physical Uplink Control Channel (PUCCH) which carries the UCI feedback from a user equipment (UE) to a base station (BS) if a downlink (DL) control signal is received by the UE from the BS. The invention relates particularly, but not exclusively, to detection of partial DTX in small block encoded signals on the UL.

BACKGROUND OF THE INVENTION

In long-terra evolution (LTE) communications systems, in a 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 user equipment (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 other words, correctly decoding PDCCH is a prerequisite for properly decoding PDSCH.

In order to prevent the loss of transport blocks, LTE has adopted the Hybrid Automatic Repeat Request (HARQ) scheme. In the physical layer of Evolved UMTS Terrestrial Radio Access Network (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 PUCCH or Physical Uplink Shared Channel (PUSCH).

But if the UE is not able to correctly decode the PDCCH, it cannot correctly decode PDSCH, and may even not know that it needs to send the HARQ feedback. This is called Discontinuous Transmission (DTX).

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 UE 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 as 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 device 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 device 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 it 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 state. The UCI receiver device at the BS only receives noise but processes this as though it comprises an 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.

For 5G UCI, 3GPP Technical Specification 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 about 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 is 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.

In the conventional small block code-based UCI receiver device ofFIG. 4, the resource element (RE) demapper output will be treated first by a channel estimation module to provide channel estimation data and then by an equalizer module to generate an equalized signal. The equalized signal will then be treated by a demodulation module to generate a demodulated soft bit sequence (SEQ). The demodulated soft bit SEQ will be handled by a descrambling module to create a descrambled soft bit SEQ. The descrambled soft bit SEQ will then be handled by a rate de-matching module to create a de-matched soft bit SEQ. The de-matched soft bit SEQ will be decoded through a decoder for small block code module to generate UCI bits (ACK/NACK). The soft bits comprise real signal values which differ from hard bits which are resolved to binary values.

As already explained with respect toFIGS. 1 and 2, if a UE loses a DL control signal, the UE will not send UCI ACK/NACK feedback, i.e., a DTX state will occur. The BS treats DTX as an unsuccessful DL transmission. Re-transmission is required if and when DTX occurs. But if the DTX is falsely detected as ACK, re-transmission will not be performed. More especially, DTX may occur only partially, i.e., only part of the UCI payload bits may be missing. Compared with full DTX where all UCI bits are missing, partial DTX is much more difficult to detect. From a perspective of the small block code-based UCI receiver device, a partial DTX codeword still belongs to the set of valid codewords. In view of the fact that the small block code-based UCI receiver device has no CRC check to assist with full or partial DTX detection, there is a need to be able to effectively detect partial DTX, i.e., there is a need to effectively distinguish a partial DTX signal from a non-DTX signal.

CN104168095 discloses a UCI receiver device which is configured to decode the descrambled sequence to obtain a received UCI b. It then obtains a canonical sequence by selecting a sub-sequence with 32 soft bits from the descrambled sequence. It decodes the canonical sequence to obtain a canonical UCI r. It then compares the received UCI with the canonical UCI r to determine if a DTX state has occurred. This is a highly complex solution which requires a high signal to noise ratio (SNR) to decode UCI. It is difficult to select a suitable canonical sequence.

CN 105491591 discloses a UCI receiver device which is configured to divide the descrambled sequence into N blocks each containing 32 soft hits. It then compares the signs of soft bits in a first block with all other N-1 blocks. It computes the number of same sign pairs as a, and the number of different sign pairs as b. It compares the ratio a/b with a predetermined DTX threshold value Th. If a/b is less than or equal to Th then a DTX state is determined to have occurred, but, if a/b is greater than Th, then no DTX state is determined to have occurred. The DTX decision is a hard decision based on the signs of the soft bits. The decision is sensitive to the noise or UL channel impairment. If the number of non-DTX blocks of the N blocks is much higher than the number of DTX blocks then the ratio a/b can still be high meaning that it is hard to determine if a DTX state has occurred using this metric. It is therefore difficult to detect DTX if only some RBs in any of the N blocks suffer DTX. Furthermore, different DTX scenarios between RBs within a 32-bit block are not considered.

CN103037396 discloses a signal detection method in LIE ascending control channel. The method comprises obtaining noise power estimate and channel response power estimate for at least one antenna. A Decision Variable (DV) is obtained by combining the noise power estimate and the channel response power estimate of at least one antenna. However, this reference fails to teach or suggest determining per-resource block (RB) DTX metrics.

CN 104283821 discloses obtaining control information and reference signalras well as a local reference signal (LocalRS) and subsequently deriving frequency domain channel estimate Ĥ by a least square (LS) estimation from Ĥ=r/LocalRS. This reference teaches calculating combined power Pkby combining all the power associated with the same tap of an antenna within all time slots which are associated with the average of frequency domain channel estimate Ĥ53 i Bof all antennas. However, it fails to teach calculating per-RB DTX metrics.

Among other things, what is therefore desired is a method for distinguishing a partial DTX signal from a non-DTX signal. There is also a need to effectively distinguish partial DTX from the non-DTX signal with low false alarm rate (FAR) and missed detection rate (MDR), There is also a need to detect a DTX state or a partial DTX state at an earlier stage of the workflow of UCI receiver devices.

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 or detecting DTX on a UL at a UCI receiver device in a wireless communication network.

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 a method of distinguishing a partial DTX signal from a non-DTX signal on a UL at a UCI receiver device in a wireless communication network.

Another object of the invention is to provide an improved UCI receiver device.

A further object of the invention is to provide an improved small block code-based UCI receiver device.

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 relates to a method for determining DTX an PUCCH which carries the UL UCI feedback from a UE to a BS if a DL control signal is received by the UE from the BS. Particularly, it provides a method which can effectively and efficiently distinguish between a partial DTX state and a non-DTX state. It is particularly useful for partial DTX detection in certain PUCCH formats such as PUCCH Format 2 with one Orthogonal Frequency Division Multiplexing (OFDM) symbol and only one RB not validly used due to occurrence of a full or partial DTX state, i.e., a ‘dropped’ RB.

In a first main aspect, the invention provides a method and device for detecting a discontinuous transmission state (DTX) at an uplink control information (UCI) receiver device in a wireless communication system. The method involves receiving a linear block encoded signal on an uplink (UL) at said UCI receiver device and processing the received linear block encoded signal after resource element (RE) demapping to obtain channel estimation data. The method includes determining from said channel estimation data a DTX metric for one or more selected resource blocks (RBs) and determining if a DTX state has occurred by comparing the determined DTX metric to a calculated, selected, or predetermined threshold.

In a second main aspect, the invention provides a UCI receiver device in a wireless communication system, the UCI receiver device 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 UCI receiver device to implement the method 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 of a UCI receiver device in a wireless communication system, they configure the processor to implement the method 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 an 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.

