Communication device and communication method

Abstract

A first communication device configured to communicate with a second communication device includes: circuitry configured to acquire user data length information indicating a length of one or more data units of user data to be transmitted to the second communication device; acquire at least two transmission parameter sets having one or more different parameter values, each transmission parameter set including a transmission parameter for use in transmitting the user data; determine encoding parameters from the user data length information and the at least two transmission parameter sets, the encoding parameters being the same regardless of which transmission parameter set is used to transmit the user data; encode the user data into transmission data units according to the determined encoding parameters; and modulate the transmission data units according to one of the transmission parameter sets and transmit them to the second communication device.

Description

[Technical Field]

[0001] The present disclosure relates to communication devices and methods, particularly for use in wireless LAN (WLAN) systems. [Background technology]

[0002] WLANs feature Hybrid Automatic Repeat Request (HARQ) Type I, which combines forward error correction (FEC) and automatic repeat request (ARQ) protocols. Any transmitted medium access control (MAC) layer data unit is first provided with a frame check sequence (FCS) and then encoded by a forward error correction encoder, such as a low-density parity check (LDPC) code. Upon reception, the receiver (also referred to herein as the "second communication device") performs FEC decoding and subsequently checks the validity of the FCS. If the FCS is valid, the automatic retransmission request (ARQ) mechanism sends an acknowledgement (ACK) to the transmitter (also referred to herein as the "first communication device") indicating successful reception. If the FCS is invalid, the ARQ mechanism sends a negative acknowledgement (N-ACK) to the transmitter, or sends nothing, indicating that a retransmission of the MAC layer data unit is required. After a certain number of retransmissions, depending, for example, on the data unit's lifetime, the transmission is either successful or not, in which case the MAC layer data unit is discarded at the transmitter. Therefore, in poor channel conditions with weak signal strength, HARQ Type I may not provide reliable communication since the initial (original) transmission and retransmissions may fail.

[0003] Link adaptation is a method to adapt to time-varying channels in order to provide a sustainable and reliable communication system. In IEEE 802.11, the link adaptation mechanism can switch between different physical layer (PHY) parameters, such as modulation and coding scheme (MCS), depending on the pass / fail ratio of acknowledgments received at the transmitter side.

[0004] The "Background" discussion provided herein is intended to generally set forth the context for the present disclosure. The work of the presently named inventors, to the extent that it is described in this Background section, as well as aspects of the present disclosure that would not qualify as prior art at the time of filing, are not admitted expressly or impliedly as prior art to the present disclosure. Summary of the Invention [Means for solving the problem]

[0005] It is an object to provide a communication device and method that can improve link reliability and robustness of wireless communication, and thus improve the overall efficiency of the system, as well as a corresponding computer program and non-transitory computer-readable storage medium for implementing the method.

[0006] According to an aspect, there is provided a first communication device configured to communicate with a second communication device, the first communication device comprising: - obtaining user data length information indicating a length of one or more data units of user data to be transmitted to the second communication device; obtaining at least two transmission parameter sets each including transmission parameters for use in transmitting user data, the transmission parameter sets having one or more different parameter values; determining coding parameters from the user data length information and the at least two transmission parameter sets, the coding parameters being the same regardless of which transmission parameter set is used to transmit the user data; encoding user data into transmission data units in accordance with the determined encoding parameters; - including circuitry configured to modulate and transmit a transmit data unit to the second communication device according to one of the transmit parameter sets.

[0007] According to further aspects, there are provided corresponding communication methods, a computer program comprising program means for causing a computer to perform the method steps disclosed herein when the computer program is run on a computer, and a non-transitory computer readable recording medium having stored therein a computer program product which, when run by a processor, causes the computer to perform the method disclosed herein.

[0008] Embodiments are defined in the dependent claims. It is to be understood that the disclosed communication method, the disclosed computer program, and the disclosed computer-readable recording medium have further embodiments similar and / or identical to the claimed communication devices and those defined in the dependent claims and / or disclosed herein.

[0009] One aspect of the present disclosure is link adaptation in the context of hybrid ARQ soft-combining techniques such as Chase Combining (CC) and / or Incremental Redundancy (IR). To perform soft-combining between initial and retransmissions, the coding structure must remain unchanged between each transmission. A mechanism is disclosed that ensures the same coding structure even if various parameters (e.g., PHY parameters) are changed during the (re)transmission process. More specifically, the length of the data field of a data unit (e.g., PPDU) is selected to have the same size after processing operations, regardless of the applied parameters.

[0010] The foregoing paragraphs have been provided by way of general introduction and are not intended to limit the scope of the claims that follow. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0011] A more complete appreciation of the present disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram showing the relationship between MPDU, PSDU, and PPDU used in current WLAN systems. [Figure 2] FIG. 1 is a schematic diagram of a communication system. [Figure 3] FIG. 1 is a diagram illustrating an encoding method and a decoding method used in a WLAN communication system. [Figure 4] FIG. 1 is a schematic diagram of a conventional communication system. [Figure 5] 1 is a schematic diagram of a PHY transmission procedure according to current WLAN operation. [Figure 6] 1 is a schematic diagram of a conventional transmitter layout; [Figure 7] 1 shows a table of exemplary values ​​for different parameters. [Figure 8] 1 illustrates different codeword structures for initial transmission and retransmission when using a conventional transmission scheme. [Figure 9] 1 illustrates different fields of a PPDU. [Figure 10] FIG. 1 is a schematic diagram illustrating one embodiment of a transmitter according to the present disclosure. [Figure 11] FIG. 10 illustrates the same codeword structure for initial transmission and retransmission when using the transmission scheme of the present disclosure. [Figure 12] FIG. 10 is a diagram showing the codeword structure for a retransmission with a different modulation order from that of the initial transmission. [Figure 13] 1 is a schematic diagram illustrating one embodiment of a communication scheme according to the present disclosure. [Figure 14] FIG. 9 is a schematic diagram of a computing unit 90 according to the present disclosure. [Figure 15] 1 shows a flowchart of a communication scheme according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] Referring now to the drawings, in which like reference numerals indicate the same or corresponding parts throughout the several views, Figure 1 illustrates the relationship between the MAC Protocol Data Unit (MPDU), PLCP (Physical Layer Convergence Protocol) Service Data Unit (PSDU), and Physical Layer Protocol Data Unit (PPDU) used in current WLAN systems. Essentially, the MPDU contains a Frame Check Sequence (FCS), which includes Cyclic Redundancy Check (CRC) bits, allowing the receiver to detect errors in the MPDU. This data unit, along with end-of-field (EOF) padding, is forwarded to the PHY layer as a PPDU, as shown in Figure 1, where it is scrambled and then encoded with a forward error correction code, such as a low-density parity check (LDPC) code.

[0014] On the receiving side, after receiving the PPDU, it is decoded by an LDPC decoder and forwarded to the MAC layer. The decoded data unit is checked for bit errors by the FCS. If the FCS is valid, the receiver sends a positive acknowledgment to the transmitter, acknowledging that the data unit was received correctly. If the FCS fails, the ARQ protocol sends a negative acknowledgment to the transmitter, triggering a retransmission of the same data unit or information related to that data unit. Incorrectly received data units are generally discarded entirely at the receiver.

[0015] 2 is a schematic diagram of a communication system 1 including a transmitter 2 (e.g., an access point (AP)) and a receiver 3 (e.g., a station (STA)) configured to communicate with each other via a communication channel 4. For example, the transmitter 2 transmits data units of user data contained in PPDUs to the receiver 3, which responds by transmitting an acknowledgement (Ack) or a non-acknowledgement (N-Ack).

[0016] Traditionally, based on the pass / fail ratio of acknowledgments received from the receiver 3, the transmitter 2 performs link adaptation and selects an appropriate MCS for transmitting a data unit. Typically, the transmitter 2 maintains a table containing, in the ideal case, the success rate and estimated throughput for each PHY parameter setting. Based on this table, the transmitter selects PHY parameters according to the needs of the current data transmission. For example, a high throughput setting is used for the first transmission, and a high success rate setting is used for retransmissions. Often, the table is updated on a trial-and-error basis; that is, PPDUs are transmitted ad hoc with specific PHY settings to explore the performance of a particular setting.

[0017] The encoding and decoding scheme used in the WLAN communication system 1 is shown schematically in Figure 3 for LDPC codes. A source provides scrambled data of payload bits and FCS (CRC bits). These data are then coded, OFDM modulated, and transmitted over a wireless channel. LDPC codes operate on the codeword length. Therefore, if the size of the user data is variable, pre-processing and post-processing are required to fit a variable number of bits into one or more codewords. The LDPC coding process in WLAN simultaneously fits the scrambled bits into the minimum required number of OFDM symbols and an integer number of codewords.

[0018] The pre-processing unit 11 determines the required minimum number of OFDM symbols (N SYM ) This unit also determines the codeword (CW) length (L LDPG ) and determine the number of codewords (N CW ) is calculated from the total number of scrambled data before encoding.CW If the information part of the codeword cannot be completely filled, the required shortening bits (N shrt ) is calculated. Shortened bits are fixed-value bits that are added to the information part of each codeword before encoding, but are discarded before transmission. The receiver includes these fixed-value bits before decoding. These shortened bits are not necessarily evenly distributed among the number of codewords. Therefore, the first mod(N shrt , N CW ) codeword contains one more shortened bit than the rest of the codewords. The minimum number of shortened bits per codeword is N spcw =[N shrt / N CW ] will be inserted.

[0019] The output of the pre-processing unit 11 is systematically encoded by an LPDC encoder 12 at a code rate (R) specified for each modulation coding scheme (MCS) to obtain a codeword. The post-processing unit 13 removes shortening bits inserted in the information part of the codeword and either punctures the parity part of the codeword (if there are more coded bits than can be transmitted in an OFDM symbol) or repeats the information part of the codeword (if there are not enough coded bits to fit in an OFDM symbol). If the total number of parity bits punctured to fit in an OFDM symbol is too large, coding performance will be degraded. To avoid this, an OFDM symbol is added if either of the following two conditions is met: Total number of punctured bits (N punc ) is more than 30% of the total number of parity bits:

number

number

[0020] The output of the post-processing unit 13 is then modulated per MCS and undergoes IFFT in the modulation IFFT unit 14 before being transmitted as an OFDM signal over the wireless channel 4. In the receiver, after FFT processing and demodulation in the FFT demodulation unit 20, the inverse post-processing unit 21, LDPC decoder 22, and inverse pre-processing unit 23 reverse the encoding procedure to extract the payload bits, which are provided to the sink 24. In the WLAN, the LDPC decoder 22 uses a belief propagation algorithm to decode the binary systematic LDPC code using the soft-decision bit-wise log-likelihood ratio (LLR) values ​​from the demodulator 20 as input. After passing through the demodulator 20, the received signal is sampled to measure real values ​​for soft-decision demapping. These real values ​​are soft-decision values ​​of the received bits for the corresponding bits of the M-ary modulated constellation points, and are called bit-wise LLR values.

[0021] The maximum likelihood method searches for the constellation point with the highest probability to estimate the LLR for each received bit of the received signal. The LLR is the probability ratio of a transmitted 0 bit to a transmitted 1 bit for the received signal, and can be expressed as equation (1): where b is the transmitted bit (one of the k bits in the M-ary symbol) and r is the received signal with coordinates (x, y) in the constellation diagram.

number

[0022] After applying Bayes' rule and assuming that all symbols are equally probable, the LLR value of the code bits after passing the signal over additive white Gaussian noise (AWGN) is given by Equation (2), where S0 / S1 are the constellation points with bits 0 / 1 at the given bit positions, S x / S y are the in-phase / quadrature coordinates of the constellation points, σ 2 is the noise variance of the baseband signal.

number

[0023] In summary, the LLR value is a real number that indicates the reliability of each bit. The more positive the value, the more likely it is that a 0 bit was detected, and the more negative the value, the more likely it is that a 1 bit was detected. An LLR value of 0 means that both bits are equally likely to be detected.

[0024] FIG. 4 is a schematic diagram of a conventional communication scheme used by the communication system 1 shown in FIGS. 2 and 3, whereby the PHY parameter MCS is changed for retransmissions, for example, based on the pass / fail ratio of past ACKs. In particular, in an exemplary embodiment, the original (first) transmitted PPDU 30 is retransmitted twice as PPDUs 30a and 30b, each time using a different MCS (denoted MCS, MCS', and MCS"). In other embodiments, only one or more retransmissions may be performed. At the receiver, the erroneously received data units 40, 40a (indicated in FIG. 4 by the presence of an error bit 45 in the information portions 41, 41a of the received data units 40, 40a) and their LLR values ​​L (0) , L (1) In response to an N-ACK, which represents an indication of at least one erroneous data unit that was not successfully received or decoded at the receiver, the transmitter retransmits the same data unit 30 (in this case, twice, denoted as data units 30a and 30b) to retransmit another erroneously received data unit 40a and the LLR value L (2) and a correctly received data unit 40b having the same data unit 31 as the previous data unit 40b (indicated by the absence of error bits in the information section 41b of each re-received data unit 40b). This is confirmed by sending an ACK to the transmitter. The transmitter then sends the next (different) data unit 31. After a certain number of re-transmissions depending on the lifetime of the data unit, it is determined whether the transmission was successful or not, and if so, the data unit is also discarded by the sender.

[0025] Instead of discarding an erroneously received data unit at the receiver, it can be stored and used to extract relevant information that may be useful for decoding the data unit in successive retransmissions. Soft-combining is a technique that combines the LLR values ​​of the stored erroneous data unit with the retransmitted data unit, helping the decoder to decode it correctly. Furthermore, link adaptation can be performed during retransmissions by changing PHY parameters such as MCS, for example, from a higher modulation scheme to a more robust lower modulation scheme, further increasing the chances of successful decoding.

[0026] The combination of link adaptation and HARQ soft combining can provide more reliable and robust communications, but implementing both procedures together may require some special requirements to be compatible with current WLAN standard specifications according to IEEE 802.11.Link adaptation with HARQ soft combining is performed only when there is a retransmission of information identical to or related to a data unit received in error at the receiver.

[0027] Figure 5 is a schematic diagram of the PHY transmission procedure according to current WLAN operation. When the transmission process is initiated, the MAC layer provides the PHY layer with the desired length (A_PEP_LENGTH in bytes) of one or more data units to be transmitted. This request also includes the PHY parameters to be used for the upcoming transmission. A_PEP_LENGTH and the PHY parameters are included in the PHY-TXSTART.request primitive within the TXVECTOR. The PHY layer then begins the process and calculates the actual length (PSDU_LENGTH in bytes) that can be transmitted. This length, indicated in the PHY-TXSTART.confirm primitive, may differ (greater than or equal to) A_PEP_LENGTH depending on A_PEP_LENGTH and the PHY parameters. The MAC layer then pads to fill the PSDU_LENGTH. As shown in Figure 5, data exchange between the MAC and PHY layers occurs via zero or more PHY-DATA.request and PHY-DATA.response exchanges. PHY padding by the PHY layer is shown as "Pre-FEC PHY padding" in Figure 5, while MAC padding by the MAC layer is shown as "EOF padding included" and affects the number of PHY-DATA.request / response exchanges that occur at the end.

[0028] The reason PSDU_LENGTH is a function of A_PEP_LENGTH and PHY parameters is because there are two objectives that the PHY layer must fulfill: first, to encode a data unit with an integer number of LDPC codewords, and second, to modulate an integer number of OFDM symbols.

[0029] In general, PSDU_LENGTH (bytes) is

number

number

number

number

[0030] The number of payload bits to be encoded is N pld and

number

[0031] 6 is a schematic diagram of the layout of a conventional transmitter 5 to explain the transmission process, and in particular the padding process, in more detail. The transmitter 5 is composed of a MAC layer processing unit 6 and a PHY layer processing unit 7. The MAC layer processing unit 6 is composed of a MAC control unit 60 that instructs a TXVECTOR 80 to a PHY control unit 70 of the PHY layer processing unit 7, which returns a PSDU_LENGTH 81 that determines the pre-FEC MAC and pre-FEC PHY padding. The actual transmit data 62 is concatenated with the pre-FEC MAC padding bits 61 in a MAC concatenation unit 63. As a result, the data 82 is passed to the PHY layer 7, where the PHY concatenation unit 73 concatenates the pre-FEC PHY padding bits 71 to form a N-bit field for the service field 72. service = 16 bits. These concatenated bitstreams are coded in coding unit 74 per MCS. After coding, post-FEC PHY padding bits 75 are added in adder 76, and if necessary the bitstream is padded into the last OFDM symbol, which is finally modulated and transmitted by modulator and transmitter 77. A pipeline process is often implemented, meaning that padding is added as needed while data is already being transmitted; i.e., there may not be memory to store all the data before transmission.

[0032] For soft combining, the contents of the data field of the PPDU must not be changed between the original transmission and the retransmission (i.e., the original and retransmitted PPDUs must contain identical data fields). Furthermore, the coding structure is not changed. Thus, soft combining of the above example, where 16-QAM is used in the initial transmission (MCS:4) and QPSK is used in the retransmission (MCS:2), would involve changing the PSDU_LENGTH and pre-FEC padding to encode the data field N. pld Since the lengths of the sigma and sigma are different, this does not work even if the coding rate is the same.

[0033] FIG. 7 shows a table (Table 1) of exemplary values ​​for different parameters, in particular for the same A_PEP_LENGTH data field (N pld ) (all in bits). From the example above, for A_PEP_LENGTH=2280 bits, the calculated N pld and the number of coding bits available for transmission, the codeword size is L LDPC = 1944, the number of codewords required N CW is 2. At a coding rate R=3 / 4, the information part requires 1458 bits to be coded.

[0034] N for first transmission and retransmission pld Since the difference is different, the shortening bits (N spcw ) are 225 bits and 270 bits, respectively. After systematic encoding, a parity part P is generated. The codewords are formed as shown in Figure 8, which shows different codeword structures for the initial transmission (first row) and retransmission (second row). Therefore, the codeword structures for the initial transmission and retransmission are changed so that they cannot be soft-combined.

[0035] Figure 9 shows the different fields of a PPDU. The HARQ soft combining technique is only applied to the data field of the PPDU. Therefore, in retransmission, the data field (N pld ) must be the same as in the initial transmission, along with the same state of the scrambler unit. The following disclosure describes an implementation of a link adaptation protocol with HARQ soft combining using LDPC coding under the current WLAN IEEE 802.11 standard specification.

[0036] A necessary and sufficient condition for achieving the same coding structure is that the PSDU_LENGTH should be the same between retransmissions. Since the (user) data should be the same in each transmission, its A_PEP_LENGTH, and therefore the pre-FEC MAC and PHY padding, should also be the same, which allows the data field N pld The same length is ensured.

[0037] However, when switching from one set of PHY parameters to another in a retransmission, the length of the data field may vary, which may result in different values ​​for PSDU_LENGTH and pre-FEC PHY padding, even when selected from the same code rate family, as shown in the example in Table 1 in Figure 7 for the example of changing MCS.

[0038] Below we provide an overview of the encoding mechanism in the IEEE 802.11 standard specifications for 802.11ax and 802.11be. The N number of OFDM symbols required to transmit the data coming from the MAC layer is given by A_PEP_LENGTH. SYM,init The initial number is calculated according to equation (5).

number

[0039] Therefore, while preparing the data field of the PPDU to fill the OFDM symbols, additional pre-FEC padding bits (on the MAC layer and / or PHY layer) may be added depending on A_PEP_LENGTH. DBPS Sometimes you need to add when dividing by the factor N, and sometimes you don't. DBPS is calculated as in equation (6), and the data subcarrier N SD The number of coded bits per single carrier, N BPSCS Number of spatial streams, N SS It depends on PHY parameters such as the number of N, bandwidth, resource unit (RU) size, and coding rate R. Other parameters also affect NDBPS may have a nonlinear effect on

number

[0040] For example, IEEE 802.11be EHT242-tone RU(N SD =234) and N SS If =1, N DBPS is given in Table 2 below (MCSs are grouped by the same code rate). [Table 1] Table 2 These different N DBPS can be included in the TXVECTOR, which can support link adaptation with HARQ soft combining.

[0041] In link adaptation with soft combining, the PPDU transmission procedure is modified as follows: When the PHY layer is triggered to transmit a PPDU with the TXVECTOR to be applied, the MAC layer provides other PHY parameter sets for which the current transmission should be "soft-combinable." Logically, multiple TXVECTORs may be provided, each representing a different PHY parameter set. Based on this information, the PHY layer calculates a common PSDU_LENGTH that is the same for all PHY parameter sets and performs padding accordingly. Pre-FEC padding at the PHY and MAC layers is as defined above, but for soft combining, it must be identical, e.g., standardized, between transmissions.

[0042] Once a common PSDU_LENGTH and associated padding have been defined, an initial transmission is made, followed by one or more retransmissions with the same PSDU content and padding. Each transmission process of the same data field for soft combining must be accompanied by all PHY parameter sets that may currently or previously be used for this particular data field. Not all of the PHY parameters attached may be used, either because the transmission is successful or because the PHY parameter set proves to be impractical. However, attaching too many PHY parameter sets is undesirable, as this would result in excessive padding for each transmission, reducing spectral efficiency.

[0043] 10 is a schematic diagram of one embodiment of a transmitter 100 according to the present disclosure to explain in more detail the transmission process according to the present disclosure, and in particular the current padding process. The same reference numerals as in FIG. 6 are used to indicate various elements and some of the data used by the transmitter 100.

[0044] According to the modified layout of transmitter 100 shown in FIG. 10, unlike the MAC Control Unit 60 of the conventional transmitter 5 shown in FIG. 6, MAC Control Unit 60 not only provides the PHY Layer 7 with TXVECTOR 80 to be used for the current transmission, but also provides one or more TXVECTOR'(n) (n=1, 2 in FIG. 10) 83 indicating PHY parameters for past or possible future transmissions. TXVECTOR' 83 may differ from TXVECTOR 80 in that it does not have A_PEP_LENGTH information 84. In any case, it is identical for each transmission. Moreover, TXVECTOR' 83 only holds PHY parameters that differ from the current transmission defined in TXVECTOR 80. This mechanism requires that TXVECTOR 80 and TXVECTOR' 83, if present, provide specific data fields of the same length and content for each transmission.

[0045] The A_PEP_LENGTH_Exact calculation unit 78 in the PHY layer processing unit 7 receives as input a TXVECTOR 80, 83 containing an A_PEP_LENGTH 84 desired by the MAC layer with different PHY parameters. For example, the different PHY parameter sets can be used for link adaptation with HARQ soft combining using different MCSs (different N) from the same code rate family as shown in Table 1 in FIG. 7. DBPS For a given TXVECTOR 80, 83, the A_PEP_LENGTH_Exact calculation unit 78 calculates all the different N vectors that allow soft-combining of retransmissions. DBPS To calculate A_PEP_LENGTH_Exact79 without pre-FEC padding, which provides a common PSDU_LENGTH for

[0046] In the first step, for each PHY parameter set provided in TXVECTOR 80, 83, N DBPS In the second step, each N DBPS is factored. In the third step, all N DBPS By taking the LCM (least common multiple) of the 2 and the coefficient 8 for calculating in bits, we get the special coefficient N DBPS、maxdiv In the fourth step, A_PEP_LENGTH_Exact79, which does not require PHY padding, is calculated using the following equation (7):

number

[0047] For example, if the desired A_PEP_LENGTH is 2000 bytes, and three PHY parameter sets with MCS=13, 11, and 7 are used, then DBPSWhen is used as shown in Table 3 below, the special coefficient N DBPS、max,div is for all N DBPS It can be calculated as LCM and factor 8. [Table 2] Table 3

[0048] Therefore, A_PEP_LENGTH_Exact79 in bytes can be calculated as in equation (7). A_PEP_LENGTH_Exact=2923 bytes No Pre-FEC padding (N PAD, Pre-FEC =0), after calculating A_PEP_LENGTH_Exact79, all N DBPS The common PSDU_LENGTH 81 for can be calculated from equation (3).

number

[0049] This common PSDU_LENGTH 81 can also be achieved using a fixed pre-FEC padding p' for other A_PEP_LENGTHs below this A_PEP_LENGTH_Exact due to the ceiling calculation in equation (5). Therefore, a range of A_PEP_LENGTHs including A_PEP_LENGTH_Exact can provide the same PSDU_LENGTH. Therefore, all N DBPS Data field (N pld The length of the ) is calculated as in equation (4). N pld =N service +8*PSDU_LENGTH=16+8*2923=23400 bits

[0050] N pldThe codeword structures of the initial transmission (first row) and retransmission (second row) of =23400 bits are shown in Figure 11. As can be seen from Figure 11, the codeword structures are identical and therefore soft-combinable.

[0051] Figure 12 shows the codeword structure for the initial transmission and retransmissions with different modulation orders. As shown in Figure 12, the payload bits in the data field of the PPDU are scrambled and coded with the same code rate R for the initial transmission and retransmissions. Only the modulation scheme is changed, i.e., M' is used for the initial transmission and M" is used for the retransmissions. As a result, the number of OFDM symbols also changes.

[0052] FIG. 13 is a schematic diagram of one embodiment of a communication scheme according to the present disclosure. In particular, it illustrates an exemplary link adaptation protocol using HARQ soft combining. The same reference numerals as in FIG. 4 are used. According to this communication scheme, based on received unacknowledged or unacknowledged feedback, the transmitter lowers its MCS from the same code rate family (MCS 13, 11, and 7 in this example) for each retransmission to adapt the link. As with the conventional communication scheme shown in FIG. 4, different MCSs are selected (particularly by the MAC layer) for the initial transmission and two retransmissions 30a and 30b of the PPDU 30. However, according to the communication scheme according to the present disclosure, the different MCSs used for transmission 30 and retransmissions 30a and 30b all belong to the same code rate family, i.e., the code rate is the same (e.g., 5 / 6) for all three transmissions 30, 30a, and 30b.

[0053] At the receiver side, the erroneously received PPDUs 40, 40a are stored for HARQ soft combining. The LLR values ​​L of these erroneous data units 40, 40a are stored. (0) , L (1) is the LLR value L of the newly retransmitted PPDU40b. (2)(If Chase combining is applied, as shown in FIG. 13), or only the additional parity information of the newly retransmitted PPDU 40b is used (as incremental redundancy) together with the stored erroneously received PPDU 40, 40a to decode the PPDU (in other embodiments, the concepts of Chase combining and incremental redundancy can be used together).

[0054] According to the IEEE 802.11 EHT standard, there are specific MCSs with the same code rate as 5 / 6, 3 / 4, or 1 / 2, as shown in Table 4 below. Therefore, while adapting the link for soft combining, only the modulation scheme may change in successive retransmissions, as indicated by the Tx count, starting from 0 for the first transmission, 1 for the first retransmission, etc. The numbering of the Tx count is exemplary, and different settings are applicable in different scenarios. It is also possible to consider only a subset of the MCSs for a particular code rate set, for example, only MCS11 and MCS9. [Table 3] Table 4

[0055] In addition to changing the MCS for different transmissions (subject to the above restrictions), one or more of the following PHY parameters may also be subject to change: - Number of spatial streams (N SS ) -Bandwidth (BW) -Resource unit (RU) size -Space-Time Block Coding (STBC) -Dual Carrier Modulation (DCM) -PPDU format - Number of OFDM subcarriers All the above parameters are calculated for OFDM symbol N DBPS For example, the number of spatial streams N SS When the number of ,doubly doubles, as shown in equation (4), NDBPS will double.

[0056] In principle, any combination is possible. For example, the PHY parameter set for soft combination of data payloads is (MCS: 13, N ss :2), (MCS:11, N SS :2), (MCS:13, N SS :1) A combination of the above can be used. In general, it can be changed. DBPS These parameters are transparent to the assumed mechanism and can include one or more of the following: guard interval length, length of the channel estimation field (LTF: Long Learning Field), beamforming, presence of midamble, spatial reuse parameters, etc.

[0057] Below, we will explain some example cases based on the same code rate family but with different MCS PHY parameters.

[0058] In the first case, the following parameters are used: (R, N SS , N SD )=(5 / 6, 1, 234). For the code rate R=5 / 6 family, under the assumption that all MCSs may be used for link adaptation, N DBPS,まxDiv can be calculated as shown in Table 5 below. [Table 4] Table 5

[0059] As shown in Table 6, when A_PEP_LENGTH=2000 bytes, A_PEP_LENGTH_Exact=2923 bytes, which is the same as the common PSDU_LENGTH and the length of the data field N pld = 2925 bytes. The range of A_PEP_LENGTH is 2890-2923 bytes, and all MCSs have the same PSDU_LENGTH and N pldprovides the same pre-FEC padding p' bytes to [Table 5] Table 6

[0060] In the above example, we assume that all MCSs in the code rate 5 / 6 family may be used in retransmissions. For example, if MCS 11 is not used, then N DBPS、maxdiv = 39 * 5 * 3 * 2 * 2 * 2 = 4680 bits, A_PEP_LENGTH_Exact = 2338 bytes, which is significantly less than the previous 2923 bytes. Therefore, if 1024-QAM is excluded from the MCS and may be used for link adaptation for soft combining of certain data fields, the PPDU length can be quantized lower to create a PPDU. In this regard, the selection of PHY parameters that can be used for link adaptation for soft combining should be done carefully.

[0061] In the second case, the following parameters are used: (R, N SS , N SD )=(3 / 4,1,234). For the code rate R=3 / 4 family, under the assumption that all MCSs can potentially be used for link adaptation, N DBPS、maxdiv can be calculated as shown in Table 7 below. [Table 6] Table 7

[0062] As shown in Table 8, when A_PEP_LENGTH=5000 bytes, A_PEP_LENGTH=5263 bytes, which is the common PSDU_LENGTH and the length of the data field N pld = 5265 bytes. The A_PEP_LENGTH range of 5253-5263 bytes is equivalent to the same PSDU_LENGTH and N pld , providing the same pre-FEC padding, p' bytes. [Table 7] Table 8

[0063] In the third case, the following parameters are used: (R, N SS , N SD )=(1 / 2, 1,234). For the code rate R=1 / 2 family, under the assumption that all MCSs can potentially be used for link adaptation, N DBPS、maxdiv can be calculated as shown in Table 9 below. [Table 8] Table 9

[0064] As shown in Table 10, when A_PEP_LENGTH=100 bytes, A_PEP_LENGTH=115 bytes, which is the common PSDU_LENGTH and the length of the data field N pld = 117 bytes. The A_PEP_LENGTH range of 112-115 bytes is equivalent to the same PSDU_LENGTH and N pld , providing the same pre-FEC padding, p' bytes. [Table 9] Table 10

[0065] Therefore, RU and N SS After the selection of A_PEP_LENGTH, any of the above cases for the same code rate MCS (if necessary) can be selected for link adaptation with HARQ soft combining with a particular A_PEP_LENGTH, which can be calculated as above.

[0066] As shown in the three examples above, a low N is used to avoid coarsely quantized PSDU lengths that can cause excessive padding. DBPS、maxdivTo achieve this, the selection of potentially usable PHY parameters should be carefully chosen. Furthermore, not only a single A_PEP_LENGTH is supported, but also a range, which may help to avoid or reduce padding.

[0067] 14 is a schematic diagram of a calculation unit 90 configured to recommend a range for A_PEP_LENGTH. The calculation unit 90 calculates N DBPS、maxdiv Such a unit may reside in the PHY layer 7 or MAC layer 6 of the transmitter 100 shown in Figure 10. Its input interface is a set of PHY parameters (e.g., TXVEC-TORS) 83 and / or A_PEP_LENGTH 81, and its output interface is N DBPS、maxdiv 85, and / or A_PEP_LENGTH_range86.

[0068] Essentially, calculation unit 90 is a kind of recommendation unit that recommends a range 86 for A_PEP_LENGTH so that MAC Layer 6 can try to fill A_PEP_LENGTH as well as possible. In one embodiment, calculation unit 90 replaces or can be included in A_PEP_LENGTH_Exact unit 78, except that it determines a range of A_PEP_LENGTH that results in the same PSDU_LENGTH. Without this calculation unit, MAC Layer 6 may need to do excessive padding, especially if PSDU_LENGTH is much larger than A_PEP_LENGTH, but with this calculation unit 90, for example, additional MAC layer data units may be added so that padding is minimized.

[0069] 15 shows a flowchart of a communication method 200 according to the present disclosure. The communication method 200 is performed by a transmitter (first communication device) configured to communicate with a receiver (second communication device), such as the transmitter 100 shown in FIG. 10 (in particular, the A_PEP_LENGTH_Exact calculation unit 78). The transmitter generally comprises circuitry (e.g., a processor, a computer, dedicated processing hardware, etc.) for performing the steps of the communication method, but may instead include separate units for performing different steps. In an embodiment, the communication method is implemented in software as a computer program running on a corresponding computer or processor.

[0070] The first step 201 of the communication method 200 involves, inter alia, obtaining (receiving or retrieving) user data length information (A_PEP_LENGTH 84 in the embodiment shown in FIG. 10) from the MAC layer 6. The user data length information indicates the length of one or more data units of user data to be transmitted to the receiver.

[0071] A second step 202 of the communication method 200 involves obtaining at least two transmit parameter sets (TXVECTOR80 and TXVECTOR83 in the embodiment shown in FIG. 10) each containing transmit parameters for use in transmitting user data, the at least two transmit parameter sets having one or more different parameter values.

[0072] A third step 203 of the communication method 200 involves determining, from the user data length information and the at least two transmission parameter sets, coding parameters (e.g., code rate, shortened bits, etc.) that are the same regardless of which transmission parameter set is used to transmit the user data. Thus, the initial transmission and potential retransmissions use the same coding parameters, but the retransmissions have modified modulation parameters (specified by the MCS) compared to previous retransmissions of the same data unit as the initial transmission. The identical coding parameters may be determined in the A_PEP_LENGTH_Exact calculation unit 78 (see FIG. 10), and in practice the A_PEP_LENGTH Exact value preferably causes the PHY control unit 70 to calculate the identical coding parameters.

[0073] In a fourth step 204 of the communication method 200, the user data is encoded into transmission data units (also called codewords, and in rare cases there may be only one single transmission data unit / codeword) according to the determined encoding parameters.

[0074] A fifth step 205 of the communication method 200 involves modulating and transmitting a transmit data unit to the second communication device according to one of the transmit parameter sets (in the embodiment shown in FIG. 10, one of TXVECTOR80 and TXVECTOR83). The modulation depends on one of the transmit parameter sets, and the encoding depends on at least two transmit parameter sets. Thus, the transmit data unit generally represents a codeword (i.e., the output of the encoder), and not an OFDM symbol (i.e., the output of the modulator).

[0075] In summary, according to the present disclosure, link adaptation is proposed in the context of hybrid ARQ soft-combining techniques such as Chase Combining (CC) and / or Incremental Redundancy (IR). To implement the soft-combining of retransmissions and initial transmissions, the coding structure is kept unchanged between each transmission. Thus, a mechanism is presented that ensures the same coding structure even if one or more PHY parameters are changed in the (re)transmission process. More specifically, the length of the data field of the PPDU is selected to always have the same size after the PHY processing operation, regardless of the PHY parameters applied.

[0076] Thus, the foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. As will be understood by those skilled in the art, the present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. Accordingly, the disclosure of this disclosure, as well as the other claims, are intended to be illustrative, not limiting, of the scope of the disclosure. This disclosure defines in part the scope of the preceding claim terms, so as to prevent the public from releasing subject matter that includes readily discernible variations of the teachings herein.

[0077] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0078] To the extent that embodiments of the present disclosure have been described as being implemented, at least in part, by software-controlled data processing apparatus, it will be understood that non-transitory machine-readable media having such software thereon, such as optical disks, magnetic disks, semiconductor memories, etc., are also considered to represent embodiments of the present disclosure. Moreover, such software may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0079] The elements of the disclosed devices, apparatus, and systems can be implemented by corresponding hardware and / or software elements, e.g., appropriate circuitry. A circuit is a structural collection of electronic components, including integrated circuits, including conventional circuit elements, application-specific integrated circuits, standard integrated circuits, application-specific standard products, and field-programmable gate arrays. Furthermore, a circuit includes a central processing device, a graphics processing device, or a microprocessor that is programmed or configured according to software code. A circuit includes the hardware described above that executes software, but does not include pure software.

[0080] Below is a list of further embodiments of the disclosed subject matter: 1.- Obtaining user data length information indicating a length of one or more data units of user data to be transmitted to a second communication device; obtaining at least two transmission parameter sets each including transmission parameters for use in transmitting the user data, the transmission parameter sets having one or more different parameter values; - determining coding parameters from the user data length information and the at least two transmission parameter sets, the coding parameters being the same regardless of which transmission parameter set is used to transmit the user data; - encoding the user data into a transmission data unit in accordance with the determined coding parameters; a first communications device configured to communicate with the second communications device, the first communications device including circuitry configured to modulate and transmit the transmission data unit to the second communications device in accordance with one of the transmission parameter sets; 2. The circuit is determining a combined user data length based on the at least two transmission parameter sets or all transmission parameter sets; - A first communication device as described in embodiment 1, configured to use the aggregate user data length in determining the same encoding parameter. 3. The circuit 3. The first communication device of embodiment 2, configured to generate a user data unit having the determined aggregate user data length from the user data, and encode the generated user data unit into the transmission data unit. 4. A first communications device as in any one of the preceding embodiments, wherein the at least two transmission parameter sets indicate at least the same code rate. 5. The first communication device of embodiment 1 or 3, wherein the circuitry is configured to add padding bits to the user data and / or the generated user data unit and / or the encoded user data unit. 6. Transmission parameter set -Modulation and Coding Scheme (MCS), - Number of spatial streams (N SS ), -Bandwidth (BW), -Resource unit (RU) size, -Space-Time Block Coding (STBC), -Dual Carrier Modulation (DCM), -data unit format, and - Number of subcarriers 10. The first communication device of any one of the preceding embodiments, 7. A first communication device as in any one of the preceding embodiments, wherein the circuitry is configured to retransmit the same user data of the same user data length using one of the at least two transmission parameter sets that is different from the transmission parameter set used in the original transmission of the user data. 8. The first communications device of embodiment 7, wherein the circuitry is configured to use the same padding in the retransmission as was used before the original transmission. 9. A first communications device as described in embodiment 7 or 8, wherein the circuit is configured to retransmit the same user data in response to an indication from the second communications device indicating at least one data unit that was unsuccessfully received or decoded by the second communications device, in particular in response to not receiving an acknowledgment or receiving a negative acknowledgment after the original transmission. 10. A first communication device as described in any one of embodiments 7 to 9, wherein the circuit is configured to include in the retransmission a retransmission instruction indicating that the retransmission is for a soft combination of the originally transmitted user data and the retransmitted user data, in particular to include the retransmission instruction in a preamble of the transmitted data unit together with parameters of the used transmission parameter set. 11. A first communication device as described in any one of embodiments 7 to 10, wherein the circuit is configured to perform one or more further retransmissions of the same user data of the same user data length each time using one of the at least two transmission parameter sets different from the transmission parameter set used for the original transmission of the user data. 12. The circuit calculates the total user data length by: - from the at least two transmission parameter sets, select an OFDM symbol bit number (N DBPS ) is determined, The determined number of OFDM symbol bits (N DBPS ) and factorize it. - the number of OFDM symbol bits (N DBPS) factorization number (N DBPS.maxDiv ), and - the factorization number (N DBPS.maxDiv 3. The first communications device of embodiment 2, configured to determine the aggregate user data length by determining the aggregate user data length from 13. A first communications device as in any one of the preceding embodiments, wherein the circuitry is configured to determine a range of possible user data lengths that provide the same aggregate user data length. 14. The circuitry includes a medium access control (MAC) layer circuitry and a physical (PHY) layer circuitry; the MAC layer circuitry is configured to determine at least two sets of transmission parameters and pass them to the PHY layer circuitry; 10. A first communications device as in any one of the preceding embodiments, wherein the PHY layer circuitry is configured to determine the user data length information, encode the user data, and modulate and transmit the transmission data unit. 15. A first communication device as described in embodiment 14, wherein the MAC layer circuit is configured to transmit to the PHY layer circuit only parameters of the transmission parameter set used for retransmission that are different from the transmission parameter set used for the original transmission. 16. The circuitry receives from the second communication device: - an acknowledgement indicating the reception status of one or more MAC layer data units included in the transmission data unit transmitted to the second communication device; and / or 10. A first communications device as in any one of the preceding embodiments, configured to receive no acknowledgement or no acknowledgement at all within a predetermined time from transmitting the transmission data unit to the second communications device. 17. The first communications device of any one of the preceding embodiments, wherein the circuitry is configured to include in the retransmitted data unit one or more of the same MAC header, frame body, frame check sequence (FCS), end-of-frame (EOF) padding, same service field, same zero or more delimiters, and, if included, same physical layer (PHY) padding field as included in the corresponding originally transmitted data unit. 18. The circuitry is included in or with the original transmitted data unit or the retransmitted data unit at the second communications device. - If soft combining is applicable, -Soft combining type, the originally transmitted data unit corresponding to the retransmitted data unit; the first code rate, and the transmission parameter set used for the original transmission and / or the transmission parameter set used for the retransmission 10. A first communication device as in any one of the preceding embodiments, configured to transmit decoding information indicative of one or more of: 19.- Obtain user data length information indicating a length of one or more data units of user data to be transmitted to the second communication device; obtaining at least two transmission parameter sets, each including transmission parameters to be used in transmitting the user data, and each having one or more different parameter values; - determining coding parameters from the user data length information and the at least two transmission parameter sets, the coding parameters being the same regardless of which transmission parameter set is used to transmit the user data; - encoding the user data into the transmission data unit in accordance with the determined encoding parameters; - a first communication method of a first communication device configured to communicate with the second communication device, comprising modulating the transmission data unit in accordance with one of the transmission parameter sets and transmitting it to the second communication device. 20. A non-transitory computer-readable recording medium having stored therein a computer program product that, when executed by a processor, causes the method of embodiment 19 to be performed. 21. A computer program comprising program code means for causing a computer to carry out the steps of the method according to embodiment 19 when the computer program is run on the computer.

Claims

1. - obtaining user data length information indicating the length of one or more data units of user data to be transmitted to the second communication device; - obtaining at least two transmission parameter sets each including transmission parameters for use in transmitting said user data, said transmission parameter sets having one or more different parameter values; - determining coding parameters from said user data length information and said at least two transmission parameter sets, which are the same regardless of which transmission parameter set is used to transmit said user data; - encoding said user data into transmission data units according to said determined coding parameters; a first communications device configured to communicate with said second communications device, said first communications device including a circuit configured to modulate said transmission data unit in accordance with one of said transmission parameter sets and transmit it to said second communications device;

2. The circuit comprises: determining a combined user data length based on the at least two or all transmission parameter sets; A first communications device according to claim 1, configured to use the aggregate user data length in determining the same coding parameters.

3. The circuit comprises:

3. The first communication device of claim 2, configured to generate a user data unit having the determined aggregate user data length from the user data, and to encode the generated user data unit into the transmission data unit.

4. The first communications device of claim 1 , wherein the at least two transmission parameter sets indicate at least the same code rate.

5. 4. The first communications device of claim 1 or 3, wherein the circuitry is configured to add padding bits to the user data and / or the generated user data unit and / or the encoded user data unit.

6. The transmission parameter set is - modulation and coding scheme (MCS), - Number of spatial streams (N ＳＳ ), - bandwidth (BW), Resource unit (RU) size, Space-Time Block Coding (STBC), Dual Carrier Modulation (DCM), - the format of the data unit, and - Number of subcarriers The first communication device of claim 1 , comprising one or more of:

7. 2. The first communications device of claim 1, wherein the circuitry is configured to retransmit the same user data of the same user data length using one of the at least two transmission parameter sets that is different from the transmission parameter set used for the original transmission of the user data.

8. 8. The first communications device of claim 7, wherein the circuitry is configured to use the same padding in the retransmission as was used before the original transmission.

9. 8. The first communications device of claim 7, wherein the circuitry is configured to retransmit the same user data in response to an indication from the second communications device indicating at least one data unit that was unsuccessfully received or decoded by the second communications device, in particular in response to no acknowledgement or a negative acknowledgement received after the original transmission.

10. 8. The first communications device of claim 7, wherein the circuitry is configured to include in the retransmission a retransmission indication indicating that the retransmission is for a soft combination of the originally transmitted user data and the retransmitted user data, in particular to include the retransmission indication together with parameters of the used transmission parameter set in a preamble of the transmitted data unit.

11. 8. The first communications device of claim 7, wherein the circuitry is configured to perform one or more further retransmissions of the same user data of the same user data length, each time using one of the at least two transmission parameter sets different from the transmission parameter set used for the original transmission of the user data.

12. The circuitry calculates the aggregate user data length as - from said at least two transmission parameter sets, a number of OFDM symbol bits (N ＤＢＰＳ ) is determined, - the determined number of OFDM symbol bits (N ＤＢＰＳ ) is factorized, - the number of OFDM symbol bits (N ＤＢＰＳ ) factorization number (N ＤＢＰＳ．ｍａｘＤｉｖ ) and - the factorization number (N ＤＢＰＳ．ｍａｘＤｉｖ 3. The first communications device of claim 2, configured to determine the aggregate user data length by determining the aggregate user data length from:

13. The first communications device of claim 1 , wherein the circuitry is configured to determine a range of possible user data lengths that provide the same aggregate user data length.

14. the circuitry includes a medium access control (MAC) layer circuitry and a physical (PHY) layer circuitry; the MAC layer circuitry is configured to determine at least two sets of transmission parameters and pass them to the PHY layer circuitry; The first communication device of claim 1 , wherein the PHY layer circuitry is configured to determine the user data length information, encode the user data, and modulate and transmit the transmission data unit.

15. 15. The first communication device of claim 14, wherein the MAC layer circuitry is configured to transmit to the PHY layer circuit only parameters of the transmission parameter set used for the retransmission that differ from the transmission parameter set used for the original transmission.

16. The circuitry receives from the second communication device: an acknowledgement indicating the reception status of one or more MAC layer data units contained in the transmission data unit sent to the second communication device; and / or A first communications device according to claim 1, configured to receive no acknowledgement or no acknowledgement at all within a predetermined time of sending the transmit data unit to the second communications device.

17. 2. The first communications device of claim 1, wherein the circuitry is configured to include in a retransmitted data unit one or more of the same MAC header, frame body, frame check sequence (FCS), end-of-frame (EOF) padding, same service field, same zero or more delimiters, and, if included, same physical layer (PHY) padding field as included in the corresponding originally transmitted data unit.

18. The circuitry may be included in or with the original transmitted data unit or the retransmitted data unit at the second communication device. - if soft combining is applicable, - Type of soft combining, the originally transmitted data unit corresponding to the retransmitted data unit, the first code rate, and the transmission parameter set used for the original transmission and / or the transmission parameter set used for the retransmission 10. The first communication device of claim 1, configured to transmit decoding information indicative of one or more of:

19. - obtaining user data length information indicating the length of one or more data units of user data to be transmitted to the second communication device; - obtaining at least two transmission parameter sets, each containing transmission parameters to be used for transmitting said user data, and having one or more different parameter values; - determining coding parameters from said user data length information and said at least two transmission parameter sets, which coding parameters are the same regardless of which transmission parameter set is used to transmit said user data; - encoding said user data into said transmission data units according to said determined encoding parameters; - a first communication method of a first communication device configured to communicate with said second communication device, comprising modulating said transmission data unit in accordance with one of said transmission parameter sets and transmitting it to said second communication device;

20. 20. A non-transitory computer readable storage medium having stored therein a computer program product which, when executed by a processor, causes the method of claim 19 to be performed.

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