TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of fast link adaptation in wireless network communication systems.

BACKGROUND

Advanced Wi-Fi standards, such as 802.11ax and 802.11be, support a very high data rate, e.g. 4.8Gbps up to 23Gbps. Link Adaptation (LA) is a mechanism for tuning the transmitting, TX, scheme and parameters, such as the PHY rate, specified by the Modulation Coding Scheme, MCS, the number of streams, and frequency allocation (Resource Unit (RU) choice), etc. The tuning attempts to optimally adapt the parameters to the instantaneous conditions of a radio link, e.g. channel quality and interference, while accommodating other system constraints and requirements.

One of the most popular implementations is the Minstrel algorithm (https://wireless.wiki.kernel.org/en/developers/documentatio n/mac80211/ratecontrol/minstrel).

In the Minstrel algorithm, the rate-defining parameters are slowly varied via a ‘trial and error’ procedure, based on the received acknowledgements, ACKs, on transmitted data packets reported by the receiver, RX. 'Slowly' here pertains to the fact that it may take a very long time for the algorithm to converge to the optimal set of parameters, such that some pre-defined metric target is reached, e.g. a packet error rate PER = 10%. Here the term “optimal” should be understood in the sense of long-time averaging.

On top of the ACKs, several feedback types aiding LA are supported today in the specifications of the WLAN IEEE 802.11 standards, for example: i) Signal to Noise Ratio, SNR, (channel quality indicator, CQI) per resource unit RU: a station, STA, may be instructed to compute and feed back to the originating access point, AP, the SNR for specific RUs, based on the sounding null data packet, NDP. However, the problem arises whether the AP may trust the computations performed at the STA side. For example, the question might arise what is the relationship between the SNR and the link performance, given the specific STA’s receiver implementation, and how it might influence the computations. ii) MCS Feedback (MFB): the STA may indicate which MCS it prefers. This might be an acceptable metric since it takes into consideration the STA’s implementation. However, this approach is often not implemented, and furthermore, the accuracy of the MFB is not mandated/tested by the WLAN specification, WLAN IEEE 802.11. iii) A Control High Efficiency Link Adaptation, A-CTRL HLA: An LA control message is included in the frame header part of any data or management frame sent by the non-AP STA. The specific LA control message may be added in the High-Throughput, HT, Control part, when indicated as High-Efficiency, HE, variant by any HE STA.

In order to reduce the LA convergence time, a new approach is needed. Such new approach should provide the originator as quickly as possible with a reliable estimate of the expected link performance, at least per several combinations of MCS and RU. A focus should be put on coded Bit Error Rate, BER, as the link performance metric fed back from a responding STA to the originator.

SUMMARY

The present disclosure relates to methods and apparatuses for communication in the field of fast link adaptation in wireless network communication systems.

The invention is defined by the scope of the independent claims. Some of the advantageous embodiments are provided in the dependent claims.

According to a first aspect, provided is a method for link adaptation in a wireless communication network comprising at least one originator and one or more responders, the method comprising: transmitting, by the originator, to the one or more responders a training data packet comprising a set of predefined bit sequences, the predefined bit sequences being encoded into codewords and the codewords being modulated using one or more modulation and coding schemes, MCS, wherein each modulated codeword is mapped in a predetermined way onto one or more predefined frequency subbands, the frequency subbands having a predefined number of tones extending over one or more orthogonal frequency-division multiplexing, OFDM, symbols; receiving, by the originator, a feedback report from each of the responders comprising values of a measured link performance metric pertaining to each transmitted codeword to the respective responder; adapting transmission scheme parameters of subsequent data packets over the communication links between the originator and the one or more responders based on the reported feedback.

In the following, it should be understood that N _ss , N_SS and N_SS all may be used to denote the number of spatial streams. Thus, the originator transmits a physical protocol data unit, PPDll, containing a pre-defined, i.e. known set of codewords to the responder(s). The transmitting originator entity should use different MCSs per each Rll out of the one or more allocated Rll(s), i.e. single or multiple Rll(s). In other words, the transmitting originator should use different MCS values within each Rll, The responder should respond with a feedback message providing a measured link performance metric, e.g. the number of bits in error per codeword or the bit error rate, BER. Further, the originator should be able to ‘convert’ the reported link performance metric into PER, if desired. The originator should thus be able to quickly gather some insight into the expected link performance, so it may use a specific combination of Rll, MCS, and number of spatial streams N _ss , whereby this combination meets some desired performance quality. In the above description, Bit Error Rate, BER, is an example for a link performance metric.

Therefore, this method may be used to shorten the convergence time of ACK-based data-only ‘outer-link adaptation’ mechanisms such as Minstrel.

In a possible first implementation form of the method according to the first aspect as such, the wireless communication network is a wireless local access network, WLAN; the originator and responders are WLAN devices; the data packets are physical protocol data units, PPDUs; the predefined frequency subbands are resource units, RUs.

In a possible second implementation form of the method according to any preceding implementation form of the first aspect or the first aspect as such, at least two of the modulated codewords included in the training data packet are transmitted over a different number of spatial streams, N _ss , respectively.

In a possible third implementation form of the method according to any preceding implementation form of the first aspect or the first aspect as such, the method is further comprising encoding the predefined bit sequences into codewords via LDPC or BCC encoding schemes, respectively, and splitting the coded bits comprising each codeword between number of spatial streams, N _ss , bit streams per respective spatial stream, and further dividing each bit stream into bit subsequences where each bit subsequence consists of N _BPSCS bits, where N _BPSCS is the number of bits per subcarrier per stream, and further modulating the bit subsequences comprising each bit stream into quadrature amplitude modulation, QAM symbol streams comprising together a modulated codeword, and grouping the resulting QAM symbols, one from each QAM symbol stream, into groups of N _ss QAM symbols, wherein each group is mapped onto a single respective tone within the frequency subband, or Rll, onto which the modulated codeword is mapped.

Here, it should be understood that N _BPSCS and N_BPSCS both may be used to denote the number of bits per subcarrier per spatial stream.

In a possible fourth implementation form of the method according to any preceding implementation form of the first aspect or the first aspect as such, the modulated codewords are mapped onto an Rll spanning several OFDM symbols in consecutive order.

In a possible fifth implementation form of the method according to any preceding implementation form of the first aspect or the first aspect as such, the modulated codewords are mapped onto an Rll spanning several OFDM symbols such that each modulated codeword starts at a different OFDM symbol.

In a possible sixth implementation form of the method according to any of the fourth or fifth implementation form of the first aspect, each of the modulated codewords is aligned to the tones such that each tone onto which the modulated codeword is mapped carries exactly the same number of bits per subcarrier per spatial stream, N _BPSCS .

Here, it should be understood that N _BPSCS and N_BPSCS both may be used to denote the number of bits per subcarrier per spatial stream.

In a possible seventh implementation form of the method according to the sixth implementation form of the first aspect, the mapping of modulated codewords to the tones comprises padding with arbitrary QAM symbols unused tones of the frequency subbands within the used OFDM symbols. in a possible eighth implementation form of the method according to any of the fourth or fifth implementation forms of the first aspect, the method further comprises before modulating the codewords, deleting one or more bits at the end of the codeword so as to align with the number of tones of the OFDM symbols such that after modulating the codewords, each tone onto which the modulated codeword is mapped carries exactly the same number of bits per subcarrier per spatial stream, N _BPSCS .

In a possible ninth implementation form of the method according to any one of the first or second implementation forms of the first aspect or the first aspect as such, the method further comprises transmitting the training data packet comprises indicating to the responders which modulated codewords and their respective MCS and N _ss are transmitted within the training data packet by including an overhead.

In a possible tenth implementation form of the method according to the ninth implementation form of the first aspect, the overhead comprises explicitly signaling each MCS value as well as each N _ss value using a predetermined number of bits, respectively.

In a possible eleventh implementation form of the method according to the ninth implementation form of the first aspect, the overhead indicates each combination of MCS and N _ss to be used by indicating a corresponding entry from a predefined table listing some or all PHY rate indices, wherein each PHY rate index is associated in a predefined manner with a unique pair of MCS and N _ss values.

In a possible twelfth implementation form of the method according to the ninth implementation form of the first aspect, the overhead includes, for a single value of N _ss , an indication of the used values of the MCS and the order of the used values of the MCS.

In a possible thirteenth implementation form of the method according to the ninth implementation form of the first aspect, the overhead further including a predefined table indicating the order of modulated codewords with their respective MCS and N _ss combinations, using a field with a predefined number of bits.

In a possible fourteenth implementation form of the method according to any one of the first to third implementation form of the first aspect or the first aspect as such, the method further comprising creating the modulated codewords to be sent over each frequency subband by one or more of: i) defining different predefined bit sequences per frequency subband, and encoding and modulating the different predefined bit sequences to create respective different modulated codewords per frequency subband; ii) defining a first predefined bit sequence and creating further, different bit sequences per frequency subband by applying different predefined cyclic shifts onto the first predefined bit sequence, and furthermore encoding and modulating the different bit sequences to create respective different modulated codewords per frequency subband; iii) defining a first predefined bit sequence and creating further, different bit sequences per frequency subband by applying different predefined scrambling sequences onto the first predefined bit sequence, and furthermore encoding and modulating the different bit sequences to create respective different modulated codewords per frequency subband; iv) encoding and modulating a predefined bit sequence into a first modulated codeword comprising a sequence of QAM symbols, and creating further, different modulated codewords per frequency subband comprising respective different sequences of QAM symbols by applying different, predefined permutations onto the first sequence of QAM symbols; v) defining a first sequence of modulated codewords to be sent over a first frequency subband according to a predefined order of combinations of MCS and N _ss , and creating further, different sequences of modulated codewords to be sent over other frequency subbands by permuting the order of combinations of MCS and N _ss in the first sequence of modulated codewords.

In the previous implementation form, it should be understood that instead of applying different predefined cyclic shifts other predefined bit permutations might be applied as well. For example, a pre-defined interleaving sequence may be applied to the predefined bit sequences.

In a possible fifteenth implementation form of the method according to any one of the first to second implementation form of the first aspect or the first aspect as such, wherein transmitting the training data packet to the one or more responders further comprises transmitting a different predefined bit sequences to each responder or transmitting multiple different predefined bit sequences to the same responder in each training data packet.

In a possible sixteenth implementation form of the method according to the first aspect as such, wherein the adapted transmission scheme parameters of subsequent data packets include one or more of the following: modulation and coding scheme, MCS; number of spatial streams, N _ss ; allocated frequency subbands.

Thus, the present disclosure provides solutions for transmitting codewords using multiple MCS and potentially multiple N _ss values within the same PPDll, and indicates how the codewords should be generated and tone-mapped.

The present disclosure also provides a second aspect of a method for link adaptation in a wireless communication network comprising at least one originator and one or more responders, the method comprising: receiving, from the originator, by the one or more responders, a training data packet comprising a set of predefined bit sequences, the predefined bit sequences being encoded into codewords and the codewords being modulated using one or more modulation and coding schemes, MCS, wherein each modulated codeword is mapped in a predetermined way onto one or more predefined frequency subbands, the frequency subbands having a predefined number of tones extending over one or more orthogonal frequency-division multiplexing, OFDM, symbols; transmitting to the originator, by the one or more responders, a feedback report from each of the responders comprising values of a measured link performance metric pertaining to each modulated codeword received from the originator by the respective responder.

In a possible first implementation form of the method according to the second aspect as such, the wireless communication network is a wireless local access network, WLAN; the originator and responders are WLAN devices; the data packets are physical protocol data units, PPDUs; the predefined frequency subbands are resource units, RUs.

In a possible second implementation form according to any preceding implementation form of the second aspect or the second aspect as such, at least two of the modulated codewords included in the training data packet are received with a different number of spatial streams, N _ss , respectively.

In a possible third implementation form according to any preceding implementation form of the second aspect or the second aspect as such, receiving the training data packet by the one or more responders further comprises receiving a different modulated codeword by each responder or receiving multiple different codewords by the same responder in each training data packet.

In a possible fourth implementation form according to the second implementation form of the second aspect, receiving the training data packet comprises receiving, from the originator, a different modulated codeword by each responder or receiving multiple different modulated codewords by the same responder in each training data packet.

The present disclosure also provides a third aspect of an apparatus in a wireless communication network, the network comprising one or more responders, the apparatus comprising at least one originator, the originator configured to: transmit to the one or more responders a training data packet comprising a set of predefined bit sequences, the predefined bit sequences being encoded into codewords and the codewords being modulated using one or more modulation and coding schemes, MCS, wherein each modulated codeword is mapped in a predetermined way onto one or more predefined frequency subbands, the frequency subbands having a predefined number of tones extending over one or more orthogonal frequency-division multiplexing, OFDM, symbols; receive a feedback report from each of the responders comprising values of a measured link performance metric pertaining to each modulated codeword transmitted to the respective responder; adapt transmission scheme parameters of subsequent data packets over the communication links between the originator and the one or more responders based on the reported feedback.

In a possible first implementation form of the apparatus according to the third aspect as such, wherein: the wireless communication network is a wireless local access network, WLAN; the originator and responders are WLAN devices; the data packets are physical protocol data units, PPDUs; the predefined frequency subbands are resource units, RUs.

In a possible second implementation form of the apparatus according to any preceding implementation form of the third aspect or the third aspect as such, the originator is configured to transmit a training data packet wherein at least two of the modulated codewords included in the training data packet are transmitted over a different number of spatial streams, N _ss , respectively.

In a possible third implementation form of the apparatus according to any preceding implementation form of the third aspect or the third aspect as such, the originator is further configured to: encode the predefined bit sequences into codewords via LDPC or BCC encoding schemes, respectively, and split the coded bits comprising each codeword between number of spatial streams, N _ss , bit streams per respective spatial stream, dividing each bit stream into bit subsequences where each bit subsequence consists of N _BPSCS bits, where ^N BPSCS is the number of bits per subcarrier per stream, modulate the bit subsequences comprising each bit stream into quadrature amplitude modulation, QAM symbol streams comprising together a modulated codeword, group the resulting QAM symbols, one from each QAM symbol stream, into groups of N _ss QAM symbols, wherein the originator is configured to map each group onto a single respective tone within the frequency subband, or RU, onto which the modulated codeword is mapped.

In a possible fourth implementation form of the apparatus according to any preceding implementation form of the third aspect or the third aspect as such, the originator is configured to map the modulated codewords onto an RU spanning several OFDM symbols in consecutive order. In a possible fifth implementation form of the apparatus according to any preceding implementation form of the third aspect or the third aspect as such, the originator is configured to map the modulated codewords onto an Rll spanning several OFDM symbols such that each modulated codeword starts at a different OFDM symbol.

In a possible sixth implementation form of the apparatus according to the fourth or fifth implementation form of the third aspect, the originator is configured to align each one of the modulated codewords to the tones such that each of the tones onto which the modulated codeword are mapped carries exactly the same number of bits per subcarrier per stream, BPSCS -

In a possible seventh implementation form of the apparatus according to the sixth implementation form of the third aspect, the originator is configured to align the modulated codewords to the tones and to pad with arbitrary QAM symbols unused tones of the frequency subbands within the used OFDM symbols.

In a possible eighth implementation form of the apparatus according to the seventh implementation form of the third aspect, the originator is configured to: before modulating the codewords, delete one or more bits at the end of the codeword so as to align with the number of tones of the OFDM symbols such that after modulating the codewords each tone onto which the modulated codeword is mapped carries exactly the same number of bits per subcarrier per spatial stream, N _BPSCS .

In a possible ninth implementation form of the apparatus according to the first or second implementation form of the third aspect or the third aspect as such, the originator is configured to transmit the training data packet and to indicate to the responders which modulated codewords and their respective MCS and N _ss are transmitted within the training data packet by including an overhead.

In a possible tenth implementation form of the apparatus according to the ninth implementation form of the third aspect, the overhead comprises explicitly signaling each MCS value as well as each N _ss value using a predetermined number of bits, respectively.

In a possible eleventh implementation form of the apparatus according to the ninth implementation form of the third aspect, wherein the overhead indicates each combination of MCS and N _ss to be used by indicating a corresponding entry from a predefined table listing some or all PHY rate indices, wherein each PHY rate index is associated in a predefined manner with a unique pair of MCS and N _ss values.

In a possible twelfth implementation form of the apparatus according to the ninth implementation form of the third aspect, wherein the overhead includes, for a single value of N _ss , an indication of the used values of the MCS and the order of the used values of the MCS.

In a possible thirteenth implementation form of the apparatus according to the ninth implementation form of the third aspect, the overhead further including a predefined table indicating the order of modulated codewords with their respective MCS and N _ss combinations, using a field with a predefined number of bits.

In a possible fourteenth implementation form of the apparatus according to any one of the first to fourth implementation forms of the apparatus according to the third aspect or the third aspect as such, wherein the originator is configured to create a payload to be sent over each frequency subband within each OFDM symbol, wherein the originator is configured to create the modulated codewords to be sent over each frequency subband by one or more of: i) defining different predefined bit sequences per frequency subband, and encoding and modulating the different predefined bit sequences to create respective different modulated codewords per frequency subband; ii) defining a first predefined bit sequence and creating further, different bit sequences per frequency subband by applying different predefined cyclic shifts onto the first predefined bit sequence, and furthermore encoding and modulating the different bit sequences to create respective different modulated codewords per frequency subband; iii) defining a first predefined bit sequence and creating further, different bit sequences per frequency subband by applying different predefined scrambling sequences onto the first predefined bit sequence, and furthermore encoding and modulating the different bit sequences to create respective different modulated codewords per frequency subband; iv) encoding and modulating a predefined bit sequence into a first modulated codeword comprising a sequence of QAM symbols, and creating further, different modulated codewords per frequency subband comprising respective different sequences of QAM symbols by applying different, predefined permutations onto the first sequence of QAM symbols; v) defining a first sequence of modulated codewords to be sent over a first frequency subband according to a predefined order of combinations of MCS and N _ss , and creating further, different sequences of modulated codewords to be sent over other frequency subbands by permuting the order of combinations of MCS and N _ss in the first sequence of modulated codewords.

In the previous implementation form, it should be understood that instead of applying different predefined cyclic shifts other predefined bit permutations might be applied as well. For example, a pre-defined interleaving sequence may be applied to the predefined bit sequences.

In a possible fifteenth implementation form of the apparatus according to any one of the first to fifth implementation form of the apparatus according to the third aspect or the third aspect as such, wherein the originator is configured to transmit the training data packet to the one or more responders further comprises transmitting a different predefined bit sequence to each responder or transmitting multiple different predefined bit sequences to the same responder in each training data packet.

In a possible sixteenth implementation of the apparatus according to the fifteenth implementation form of the apparatus according to the third aspect, the adapted transmission scheme parameters of subsequent data packets include one or more of the following: modulation and coding scheme, MCS; number of spatial streams, N _ss ; allocated frequency subbands.

The present disclosure also provides a fourth aspect of an apparatus in a wireless communication network, the network comprising at least one originator, the apparatus comprising at least one responder, the responder configured to: receive, from the originator, a training data packet comprising a set of predefined bit sequences, the predefined bit sequences being encoded into codewords and the codewords being modulated using one or more modulation and coding schemes, MCS, wherein each modulated codeword is mapped in a predetermined way onto one or more predefined frequency subbands, the frequency subbands having a predefined number of tones extending over one or more orthogonal frequency-division multiplexing, OFDM, symbols; transmit, to the originator, a feedback report from each of the responders comprising values of a measured link performance metric pertaining to each received codeword received from the originator by the respective responder.

In a possible implementation form of the apparatus according to the fourth aspect as such, the wireless communication network is a wireless local access network, WLAN; the originator and responders are WLAN devices; the data packets are physical protocol data units, PPDlls; the predefined frequency subbands are resource units, Rlls.

In a possible implementation form of the apparatus according to any preceding implementation form of the fourth aspect of the fourth aspect as such, at least two of the modulated codewords included in the training data packet are received with a different number of spatial streams, N _ss , respectively.

The present disclosure also provides a further aspect of a computer program product comprising program code for performing the method according to any one of the preceding implementation forms of the first aspect or the first aspect as such, or the method according to the second aspect as such.

The present disclosure also provides a further aspect of a non-transitory computer-readable medium carrying a program code which, when executed by a computer device, causes the computer device to perform the method according to any one of the preceding implementation forms of the first aspect or the first aspect as such, or the method according to the second aspect as such.

Any of the above-mentioned devices may also be termed apparatuses. Any of the above- mentioned apparatuses may be embodied on an integrated chip.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiments of the invention are described in more detail with reference to the attached figures and drawings, in which

FIG. 1 illustrates schematically an example of a wireless communication system.

FIG. 2 illustrates a method for link adaptation in a wireless communication network according to an embodiment of the present disclosure.

FIG. 3 shows an example for a pattern of mapping, here onto an Rll of ten sub-carriers, SCs, and five OFDM Symbols, of a training data packet comprising a set of predefined bit sequences according an embodiment of the present disclosure.

FIG. 4 shows an example assuming an Rll with ten SCs and a 22-bit CW according to an embodiment of the present disclosure.

FIG. 5 illustrates a predefined table of possible combinations of MCS and N _ss values and their associated PHY rate indices according to a further embodiment of the present disclosure. FIG. 6 illustrates a predefined list of options for the case of a single spatial stream and a two-bit index of MCS ordering option, according to another option of the further embodiment of the present disclosure.

FIG. 7 illustrates an example of a predefined order of codewords MCS and N _ss combinations, using a two bit index, according to another option of the further embodiment of the present invention.

FIG. 8 illustrates a method for link adaptation in a wireless communication network according to a further embodiment of the present disclosure.

FIG. 9 illustrates a further embodiment according to the present disclosure, including an apparatus in a wireless communication network.

FIG. 10 illustrates a further embodiment according to the present disclosure. Including an apparatus in a wireless communication network

DESCRIPTION

In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the invention or specific aspects in which embodiments of the present invention may be used. It is understood that embodiments of the invention may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

For instance, it is understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps, e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps, even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units, e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units, even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless specifically noted otherwise. FIG. 1 shows an example of a wireless communication system 100. The communication system 100 includes an access point, AP, 105 that is serving one or more of stations, STAs, 110, 112, 114, 116, and 118. Within the meaning of the present disclosure, an AP may also be referred to as an originator, e.g. of a specific request. Likewise, the one or more of STAs may also be referred to as one or more responders. The AP 105 typically controls aspects of communication with or among its associated stations such as radio frequency channel, transmission power limit, authentication and security. In some cases, in the communication system 100 the wireless resources for both uplink transmissions, i.e. links from STAs to APs, and downlink transmissions, i.e. links from APs to STAs, may be accessed by transmitters based on a distributed contention mechanism commonly referred to as carrier sensing multiple access with collision avoidance (CSMA/CA). In some examples, APs are referred to as Node Bs, evolved Node Bs (eNBs), next generation (NG) Node Bs (gNBs), master eNBs (MeNBs), secondary eNBs (SeNBs), master gNBs (MgNBs), secondary gNBs (SgNBs), network controllers, control nodes, base stations, access nodes, transmission points (TPs), transmission-reception points (TRPs), cells, carriers, macro cells, femtocells, pico cells, and so on, while STAs may also be commonly referred to as user equipment (UEs), mobile stations, mobiles, terminals, users, subscribers, stations, and the like. APs may provide wireless access in accordance with one or more wireless communication protocols, e.g., Wi-Fi 802.11a/b/g/n/ac/ad/ax/ay/be, the Third Generation Partnership Project (3GPP) long term evolution (LTE), LTE advanced (LTE-A), 5G, 5G LTE, 5G NR, High Speed Packet Access (HSPA), etc. While it is understood that communication systems may employ multiple APs capable of communicating with a number of stations, only one AP 105 and five stations 110- 118 are illustrated in Figure 1 for simplicity.

In IEEE 802.11 , a data payload is encoded in the physical (PHY) layer to provide efficient transmission, error detection capability, error correction capability, or a combination thereof. In IEEE 802.11 compliant wireless networks, the data payload may be encoded using either binary convolutional coding (BCG) or low-density parity check (LDPC) encoding. In the case of BCG encoding, the whole stream of information bits is fed sequentially into a generator that generates coded bits. Each contiguous subset of coded bits is a function of the information bits currently residing in the buffer of the generator, which is typically approximately 6 bits in size. In the case of LDPC encoding, several codeword sizes are defined. The information bits are divided into separate, non-overlapping portions. The portions undergo separate encoding. In order to align with the predefined LDPC codeword sizes, the information bits may be padded with so-called shortening bits, pre-forward error correcting (FEC) padding, or may be fully or partially repeated. Embodiment 1

According to a first embodiment of the present disclosure, codewords, CWs, are modulated consecutively, i.e. both in frequency and in time, one codeword after the other. Here, several CWs per MCS may be used as well, e.g. a larger number of CWs, each occupying fewer tones, for higher MCSs.

FIG. 2 illustrates a method for link adaptation in a wireless communication network according to of the present disclosure. The method for link adaptation in a wireless communication network comprises at least one originator and one or more responders. The method comprises the following steps: a step 251 of transmitting, by the originator, to the one or more responders, a training data packet comprising a set of predefined bit sequences, the predefined bit sequences being encoded into codewords and the codewords being modulated using one or more modulation and coding schemes, MCS, wherein each modulated codeword is mapped in a predetermined way onto one or more predefined frequency subbands, the frequency subbands having a predefined number of tones extending over one or more orthogonal frequency-division multiplexing, OFDM, symbols. Step 253 of receiving, by the originator a feedback report from each of the responders comprising values of a measured link performance metric pertaining to each codeword transmitted to the respective responder. Step 255 of adapting transmission scheme parameters of subsequent data packets over the communication links between the originator and the one or more responders based on the reported feedback.

Thus, in this embodiment, CWs are normally generated without shortening or repetition. However, shortening or repetition may be required, as explained below. FIG. 3 shows an example for a training data packet comprising a set of predefined bit sequences. The predefined bit sequences are being encoded into 22-bit codewords and the codewords are being modulated using one or more MCS value(s). The modulated CWs are mapped onto predefined subbands. In FIG. 3, it is assumed using an Rll with 10 tones spanning 5 OFDM symbols, and using a single spatial stream. In other words, FIG. 3 shows a mapping pattern of contiguous 22-bit modulated CWs onto an Rll with 10 tones. Here, it should be understood that the 10 tones and a 22-bit CW are selected for illustrative purposes, only, and that a different number of tones and a different number of bits in the CW and a different number of CWs might be selected. There are two options for aligning CWs to tones, such that each tone uses exactly a specified number of bits per subcarrier per stream, N _BPSCS bits, where N _BPSCS is an integer larger than zero: • No puncturing of the symbol, but padding several bits at the end of the last symbol; or else

• Puncturing several bits at the end of the last symbol.

The suggested CW mapping is carried out before Low Density Parity Check, LDPC, tone mapping, i.e. before interleaving on the sequence of Quadrature Amplitude Modulation, QAM, symbols (or a sequence of QAMs, for short).

In more detail, the example in FIG. 3 illustrates an Rll, here RU_0, with ten subcarriers (SC) I tones and five OFDM symbols. FIG. 3 illustrates the usage of modulation coding schemes MCS 0, MCS 1 , MCS 3, MCS 5, MCS 8 and MCS 10 for encoding and modulating a predefined bit sequence. There are 22 QAMs corresponding to the first modulated CW for which MCS 0 is used, i.e. MCS0_0, MCS0_1 , ... , MCS0_21 , which consecutively occupy OFDM Symbol 0 (SC 0 : SC 9), OFDM Symbol 1 (SC 0 : SC 9), and OFDM Symbol 2 (SC 0 : SC 1). The QAMs of the second modulated CW for which MCS 1 is used directly follow, i.e. MCS1_0, ... MCS1_10, starting from OFDM Symbol 2 (SC 2 : SC 9) and OFDM Symbol 3 (SC 0 : SC 2). The QAMs of MCS 3 directly follow, i.e. MCS3_0, ... MCS3_5, starting from OFDM Symbol 3 (SC 3 : SC 8). The QAMs of MCS 5 directly follow, i.e. MCS5_0, ... , MCS5_3, starting from OFDM Symbol 3 (SC 9), and continuing in OFDM Symbol 4 (SC 0 : SC 2). The QAMs of MCS 8 directly follow, starting from OFDM Symbol 4 (SC 3 : SC 5). The QAMs of the sixth (and last, in this example) modulated CW for which MCS 10 is used directly follow, starting from OFDM Symbol 4 (SC 6 : SC 8). The tone of OFDM Symbol 4 (SC 9) is padded. In this example, MCS 0 and MCS 1 include 0 padded bits; MCS 3, MCS 5 and MCS 8 each include two padded bits; MCS 10 includes 8 padded bits.

It should be understood that it is possible to transmit each CW or CWs, which is/are constructed with a different MCS, with a different N _ss : For this, the originator needs to modify the power per stream per tone, such that sum power per OFDM symbol is maintained fixed regardless of the varied number of spatial streams N _ss .

Further, the number of long training fields, LTFs, in particular extremely high throughput long training fields, EHT-LTFs, will reflect the maximum number of streams. As a result, in timefrequency regions within the training frame where the number of streams is less than the maximal N _ss , the receiver will need to account for the difference in power per stream relative to the (EHT)-LTFs. Embodiment 2

In a similar setup when compared with FIGs. 2 and 3, a further embodiment according to the present disclosure discloses that each modulated codeword, CW, begins in a different OFDM symbol. Here, several CWs per MCS may be used as well, for example a larger number of CWs for higher MCS. In this embodiment, CWs are generated without shortening or repetition.

FIG. 4 shows an example assuming an Rll with 10 tones and a 22-bit CW. Again, it should be understood that the 10 tones and a 22-bit CW are selected for illustrative purposes, only, and that a different number of tones and a different number of bits in the CW might be selected. In this embodiment, there are two options for aligning CWs to tones, such that each tone uses exactly a specified number of bits per subcarrier per stream, N _BPSCS bits, where N _BPSCS is an integer larger than zero:

• No puncturing of the symbols is used; instead, padding of several bits at the end of the respective OFDM symbol is used; or else

• Puncturing several bits at the end of the respective OFDM symbol.

It is possible to transmit each CW- which is constructed with a certain MCS - using a different number of spatial streams (namely with a different value of N _ss ).

In more detail, the example in FIG. 4 illustrates an Rll, here RU_0, with ten subcarriers I tones and eight OFDM symbols. Similar to the example shown in FIG. 3, the example in FIG. 4 illustrates usage of modulation coding schemes MCS 0, MCS 1 , MCS 3, MCS 5, MCS 8, MCS 10. In the example in FIG. 4, when using MCS 0 the single modulated CW comprises 22 QAMs, i.e. MCS0_0, MCS0_1 , ... , MCS0_21 , which consecutively occupy Symbol 0 (SC 0 : SC 9), Symbol 1 (SC 0 : SC 9), and Symbol 2 (SC 0 : SC 1). The QAMs of MCS 1 , i.e. MCS1_0, ... MCS1_10, start from the symbol immediately following Symbol 2. Here, in this example, this is Symbol 3, i.e. Symbol 3 (SC 0 : SC 9) and then Symbol 4 (SC 0). The rest of Symbol 4 may be padded or may be filled with an additionally punctured CW. The QAMs of MCS 3, i.e. MCS3_0, ... MCS3_5, start from the symbol immediately following Symbol 4. Here, in this example, this is Symbol 5 (SC 0 : SC 5). The rest of Symbol 5 may be padded or may be filled with an additionally punctured CW. In the example in FIG. 4 two CWs using MCS 5 are transmitted, with the QAMs corresponding to the second CW being further indicated by the suffix ‘b’. The QAMs of MCS 5, i.e. MCS5_0, ... , MCS5_3, MCS5_0b, MCS5_1b, MCS5_2b, MCS5_3b start from the symbol immediately following Symbol 5. Here, in this example, this is Symbol 6 (SC 0 : SC 7). The rest of Symbol 6 may be padded. The QAMs of three CWs for which MCS 8 is used, i.e. MCS8_0, MCS8_1 , MCS8_2, MCS8_0b, MCS8_1b, MCS8_2b, MCS8_0c, MCS8_1c, MCS8_2c, start from the symbol immediately following Symbol 6. Here, in this example, this is Symbol 7 (SC 0 : SC 8). The rest of Symbol 7 may be padded. The QAMs of four CWs for which MCS10 is used, i.e.. MCS10_0, ... , MCS10_2, MCS10_1b, MCS_10_2b, MCS10_1c, MCS10_2c, MCS10_1d_MCS10_2d start from the symbol immediately following Symbol 7. Here, in this example, this is Symbol 8 (SC 0 : SC 8). The rest of Symbol 8 may be padded.

Thus, in this embodiment we have illustrated an example using 22 coded bits per CW. MCS 0 and MCS 1 have 0 padded bits. MCS 3 has 2 padded bits. MCS 5 has 2 CWs and 4 padded bits. MCS 8 has 3 CWs and six padded bits. MCS 10 has 4 CWs and 2 padded bits.

Unlike in embodiment 1 , in embodiment 2 a problem with varying power per stream between different tones in the same OFDM symbol is avoided. Further, for embodiment 2, the number of (EHT-)LTFs will reflect the maximum number of streams. As a result, in OFDM symbols where the number of streams is less than the maximal N _ss , the receiver will have to account for the difference in power.

Embodiment 3

In a further embodiment according to the present disclosure, a binary convolutional code, BCC, is used instead of LDPC. Here, a pre-defined length of a 'BCC Block' such as for example a length of 1944 bits may be used. It should be noted that BCC does not operate on blocks of information bits like LDPC. In this embodiment, in analogy to embodiment 2, one or more ‘BCC Blocks' per each combination of MCS and N _ss will be mapped to separate OFDM symbols.

An alternative design of embodiment 3 is to transmit codewords coded using BCC on entire OFDM symbols, such as a pre-defined number of OFDM symbols for each combination of MCS and N _ss .

Embodiment 4

In a further embodiment according to the present disclosure, the transmitting of the training data indicates to the responder which codewords, CWs, and their respective MCS and N _ss are transmitted within the training data packet, i.e. the PPDU, by including an overhead. This way, also indicators of the respective position of the CWs and their respective MCS and N _ss are transmitted. For the overhead, the following options may be selected:

Option 1 : According to the first option for this embodiment, the overhead may comprise explicitly signaling each MCS value as well as N _ss value using a predetermined number of bits. This may be done via an extremely high throughput signal field, EHT-SIG/LA-SIG. In particular, 4 bits may be used to indicate each MCS value and 2 or 3 bits to indicate the number of spatial streams, N _ss . It should be understood, that also different numbers of bits might be used.

Option 2: According to the second option for this embodiment, the overhead may indicate each combination of MCS and N _ss to be used by indicating a corresponding entry from a predefined table. The predefined table may list some or all PHY rate indices, wherein each PHY rate index is associated in a predefined manner with a unique pair of MCS and N _ss values. In particular, the table may rank all combinations of MCS and N _ss in ascending order of PHY throughput, for example requiring 16*8=128 combinations, and may indicate each combination from this list, for example using 7 bits per index.

FIG. 5 illustrates the second option by showing ten out of 128 possible combinations of MCS and N _ss , as an example. In more detail, FIG. 5 illustrates a table showing ten columns indexed 0, 1 , ... 9 with possible combinations of MCS and N _ss and indicating the number of bits per tone for each of the ten combinations. The MCS values in the table in FIG. 5 follow the conventions of the IEEE 802.11 WLAN standard, each value indicating a specific modulation type and coding rate.

Option 3: According to the third option for this embodiment, the table as described for the second option may be further shortened to include only a subset of the combinations shown in FIG. 5, but omitting impractical combinations, for example MCS 0 with N _ss =2 from the table. Thereby, the table may be significantly shorter than the table for option 2; for example, the table may only include 32 combinations instead of 128 combinations.

Option 4: According to the fourth option for this embodiment, the overhead may include for a single value of N _ss , an indication of the used values of the MCS and the order of the used values of the MCS. In other words, according to this option, the overhead may include an index referring to one out of a predefined list of options, for a single value of N _ss , indicating the values of MCS and the order of the MCSs.

FIG. 6 shows an example for a predefined list of options with N _ss = 1 and a 2-bit index, i.e. four options altogether. Thus, for a single value, N _ss = 1, for seven MCSs, the indexes and used values of the MCS may be found in this table given the signaled 2-bit option index.

Option 5: According to the fifth option for this embodiment, the overhead may include an index pointing to a specific entry in a predefined table indicating the order of modulated codewords with their respective MCS and N _ss combinations, using a field with a predefined number of bits. In other words, the overhead may include an indicator to an entry in a predefined table specifying the order of CWs with MCS and N _ss combinations.

FIG. 7 illustrates an example of a predefined list of possible orders of CWs with seven combinations of MCS and N _ss , using a 2-bit index, i.e. four options altogether. In the table of FIG. 7, columns of the table indicate values #1 to value #7 pertaining to the respective combination of MCS and N _ss used by the signaled option, indexed 0, 1 , 2, or 3, out of four as listed in each row.

Embodiment 5

In a further embodiment according to the present disclosure, it is expected that an originator will transmit an LA training frame, i.e. known codewords, in several RUs, for example in every 242-tone Rll.

The motivation for this expectation is that the expected link performance for a wider BW, e.g. 996-tone Rll, may be extrapolated from the expected link performance in several more narrow BW portions, e.g. four 242-tone Rlls. However, the opposite scenario would not work out.

One option is that the content per Rll of the LA training frame remains essentially the same, independent of the RU location in frequency. This may simplify the feedback information reported by the responder and it may allow it to have the same meaning or format per RU.

However, transmitting the same replicated frequency-domain signal in multiple RUs may lead to a repetition in time within an OFDM symbol and possibly an undesirably high peak to average power ratio, PAPR, so a remedy is required.

Several different solutions for this problem, according to this embodiment, are listed, below:

• Solution #1 : defining different predefined bit sequences, to be used as the payload to be sent over each RU, within each OFDM symbol.

• Solution #2: defining a single predefined bit sequence, and generating different ones from it per RU by applying different, predefined cyclic shifts, or some other predefined permutations, on it, such as applying a pre-defined interleaving sequence to the predefined bit sequence

• Solution #3: similar as solution #2, but replacing the applied different cyclic shifts by different scrambling sequences, possibly defined by different seeds of some Linear Feedback Shift Register, LFSR, e.g. the same LFSR which is already defined by the IEEE 802.11 WLAN standard for other purposes.

• Solution #4: applying different, predefined cyclic shifts, or some other predefined permutations on the modulated QAMs before or after LDPC tone mapping.

• Solution #5: changing the order of the combinations of MCS and N _ss per Rll; for example, if the order of the MCS values in the first Rll is 0,1 ,2,3 then the order in the second Rll is 1 ,2, 3,0.

Embodiment 6

In a further embodiment according to the present disclosure, the originator may choose to use multiple potential codewords to transmit, and may therefore indicate to the responder(s) which codeword is being used in the LA transmission. The originator may choose to transmit a different codeword to each responder, or it may transmit a different codeword to the same responder in each training PPDU.

According to a further embodiment of the present disclosure, FIG. 8 illustrates a method for link adaptation in a wireless communication network according to of the present disclosure. The method for link adaptation in a wireless communication network comprises at least one originator and one or more responders. The method comprises the following steps: a step 351 of receiving, from the originator, by the one or more responders, a training data packet comprising a set of predefined bit sequences, the predefined bit sequences being encoded into codewords and the codewords being modulated using one or more modulation and coding schemes, MCS, wherein each modulated codeword is mapped in a predetermined way onto one or more predefined frequency subbands, the frequency subbands having a predefined number of tones extending over one or more orthogonal frequency-division multiplexing, OFDM, symbols. A step 353 transmitting to the originator, by the one or more responders, a feedback report from each of the responders comprising values of a measured link performance metric pertaining to each modulated codeword received from the originator by the respective responder.

FIG. 9 illustrates a further embodiment according to the present disclosure. FIG. 9 illustrates an apparatus 20 in a wireless communication network, the network comprising one or more responders, the apparatus comprising at least one originator, the originator comprising: a transmitting unit 2501 configured to transmit to the one or more responders a training data packet comprising a set of predefined bit sequences, the predefined bit sequences being encoded into codewords and the codewords being modulated using one or more modulation and coding schemes, MCS, wherein each modulated codeword is mapped in a predetermined way onto one or more predefined frequency subbands, the frequency subbands having a predefined number of tones extending over one or more orthogonal frequency-division multiplexing, OFDM, symbols; a receiving unit 2503 configured to receive a feedback report from each of the responders comprising values of a measured link performance metric pertaining to each modulated codeword transmitted to the respective responder; and a adapting unit 2505 configured to adapt transmission scheme parameters of subsequent data packets over the communication links between the originator and the one or more responders based on the reported feedback.

FIG. 10 illustrates a further embodiment according to the present disclosure. FIG. 10 illustrates an apparatus in a wireless communication network, the network comprising at least one originator, the apparatus comprising at least one responder, the responder comprising: a receiving unit 3501 configured to receive, from the originator, and compute link performance metrics pertaining to the received codeword(s) included in a training data packet comprising a set of predefined bit sequences, the predefined bit sequences being encoded into codewords and the codewords being modulated using one or more modulation and coding schemes, MCS, wherein each modulated codeword is mapped in a predetermined way onto one or more predefined frequency subbands, the frequency subbands having a predefined number of tones extending over one or more orthogonal frequency-division multiplexing, OFDM, symbols; and a transmitting unit 3502 configured to transmit, to the originator, a feedback report from the responder comprising values of a measured link performance metric pertaining to each received codeword received from the originator.

Summarizing, in general, as described earlier, since practical and prevalent link adaptation mechanisms such as Minstrel are very slow in terms of convergence, solutions such as presented here in the present disclosure will lead to significantly faster convergence of the LA procedure and increased system efficiency.