Patent Description:
Communication systems, e.g. in accordance with IEEE802.11ax, feature orthogonal frequency division multiple access (OFDMA). OFDMA subdivides the channel bandwidth in subsections very efficiently. These subsections are often called resource unit (RU). In IEEE802.11ax different RUs may be allocated to different users (communication devices).

Work of the presently named inventor(s), to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

It is an object to provide communication devices and methods that enable allocation of multiple resource units to a single user and that achieve high diversity with the codes and constellation diagrams, particularly provided by the IEEE <NUM> WLAN standard. It is a further object to provide a corresponding computer program and a non-transitory computer-readable recording medium for implementing the communication methods. The present invention is defined by the attached independent claims. Other preferred embodiments may be found in the dependent claims.

According to IEEE802.11ax, different RUs can be allocated to different users only. However, in some cases, it has been recognized that it may make sense to allocate more than one RU to a single user. One example is an interference scenario: If, as an example, the total channel bandwidth is divided into three RUs, e. the RU in the middle may be disturbed by interference or have a high noise level which may make this noisy RU unusable or undesired for communication. Since communication systems often employ encoding across the bandwidth, a noisy RU may result in an elevated overall error rate, which is dominated by bit errors generated by the noisy RU. Thus, allocation of two RUs, i.e. all except the noisy RU, to a single user may reduce the overall error rate.

According to the present disclosure, an assignment of multiple RUs to a single user (i.e. a single communication device, such as a station (STA), also referred to as "second communication device" herein) may be implemented, the assignment being performed by another communication device (such as another station or an access point (AP), also referred to as "first communication device" herein). The communication devices and methods of the present disclosure are preferably directed to communication via multiple resource units in orthogonal frequency division multiple access (OFDMA).

According to an aspect of the present disclosure bits of a continuous bit stream are allocated to RUs of different sizes. Various options are disclosed that differ in both implementation complexity and diversity achieved. Furthermore, exemplary implementations are provided that consider the definition of RUs of IEEE802.11ax as a baseline and outline the operation of the bit allocation for combination of resource units of various sizes.

The described embodiments, together with further advantages, will be best understood by reference to the folowing detailed description taken in conjunction with the accompanying drawings.

Table <NUM> gives an overview of different RU sizes as used according to IEEE802.11ax. The RU size is determined by the number of tones or subcarriers that reside within this RU. A tone of an RU has a center frequency within the bandwidth of that RU.

RUs are often referred to with their tone size, e.g. <NUM>-tone RU or <NUM>-tone RU, etc. Table <NUM> assumes a total of <NUM> tones in each <NUM>, which is valid for <NUM> ax WLANs. As can be also seen from Table <NUM>, an <NUM>. 11ax device can operate with <NUM> different bandwidths. If multiple RUs can be assigned to a single user, more bandwidths may be supported, e.g. a <NUM>-tone RU + a <NUM>-tone RU achieve <NUM> in total.

<FIG> shows a diagram illustrating a (first) communication device <NUM> (e.g. an AP) according to an aspect of the present disclosure for communicating with, e.g. transmitting data to, another (second) communication device <NUM> (e.g. an STA). Each of the communication devices <NUM>, <NUM> comprises respective circuitry <NUM>, <NUM> configured to perform particular operations. The circuitries may be implemented by a respective processor or computer, i.e. in hardware and/or software, or by dedicated units or elements. For instance, respectively programmed processors may represent the respective circuitries <NUM>, <NUM>.

<FIG> shows a flow chart of a (first) communication method <NUM> according an embodiment of the present disclosure, which may be performed by the circuitry <NUM> of the communication device <NUM> on the transmission side. In a first step <NUM> data words of an input bit stream to be transmitted to the second communication device <NUM> are encoded, e.g. according by an error correction code such as an LDPC code, into code words of an encoded bit stream. In a second step <NUM> the bits of the encoded bit stream, optionally after an additional padding step (not shown), are allocated to two or more resource units assigned to the second communication device <NUM> and covering different subsections of a channel bandwidth. In a third step <NUM> bits of the encoded bit stream allocated to the respective resource units are groupwise mapped, per resource unit, to symbols of a constellation. In a fourth step <NUM> the resource units are assigned to the respective subsection of the channel bandwidth in the frequency domain.

The concept of a so-called tone plan, according to which resource units of different sizes are defined, wherein a fixed number of tones is assigned to each resource unit is generally known from IEEE802.11ax. Hereby, six different resource unit sizes as shown in Table <NUM> are defined in a total channel bandwidth. The size of a resource unit or subsection of the overall bandwidth is defined by number of tones or subcarriers that it is covering. In general, a mixture of different RU sizes may be applied to cover the total channel bandwidth. According to IEEE802.11ax no more than one RU can be assigned to a single user.

According to an embodiment of the present disclosure, at least two of the two or more resource units cover subsections of the channel bandwidth having a different number of tones, wherein a number of bits of the encoded bit stream allocated to a resource unit corresponds to the number of tones of the subsection covered by the resource unit. The allocation is done such that bits allocated to the two or more resource units in one cycle are alternately allocated to the two or more resource units in two or more alternations (which may also be called iterations), wherein in each alternation a predetermined number of consecutive bits is allocated to the respective resource unit.

Further, the ratio of the predetermined numbers of consecutive bits alternately allocated to two resource units corresponds to the integer value of the ratio of the number of tones of subsections covered by said two resource units, wherein any potential remainder (that can be calculated in advance) of bits to be allocated to one or more resource units are allocated to the respective resource unit as additional bits in addition to the predetermined number of bits in a first and/or a last alternation of a cycle and/or as pre- and/or post-bits in a pre-assignment and/or post-assignment at the start and/or end of a cycle. The allocation will be explained below in more detail.

Further, in an embodiment of the present disclosure at least two of the two or more resource units cover subsections having a different number of tones, a number of bits of the encoded bit stream allocated to a resource unit is proportional to the number of tones of the subsection covered by the resource unit, and the bits to be allocated to the two or more resource units are alternately allocated to the two or more resource units in a cycle having two or more alternations (generally, in one cycle one RU corresponding to the bits of one symbol (e.g. OFDM symbol) is filled with bits). For a first portion of the bits to be allocated to the two or more resource units in one cycle, a first ratio of the predetermined numbers of consecutive bits alternately allocated to two resource units is based on the number of tones of subsections covered by said two resource units and the modulation order of a modulation of the bits allocated to the respective resource unit, and for a second portion of the bits to be allocated to two or more resource units in one cycle, a second ratio of the predetermined numbers of consecutive bits alternately allocated to two resource units is different from the first ratio.

<FIG> shows a flow chart of a communication method <NUM> according an embodiment of the present disclosure, which may be performed by the circuitry <NUM> of the communication device <NUM> on the reception side. Generally, the communication method <NUM> performs the inverse operations of the communication method <NUM>. In a first step <NUM>, tones of different subsections of a channel bandwidth that are covered by two or more resource units assigned to the second communication device are extracted from a received signal in the frequency domain. In a second step <NUM> bits of an encoded bit stream allocated to the respective resource unit are groupwise demapped, per resource unit, from symbols of a constellation. In a third step <NUM> the bits of the encoded bit stream are retrieved (i.e. deallocated) from two or more resource units. In a fourth step <NUM> code words of the encoded bit stream, optionally after an additional padding removal step (not shown), are decoded into data words of an output bit stream.

It shall be noted that the communication methods <NUM> and <NUM> may, in other embodiments, comprise further steps at the start or end or in between the steps illustrated in <FIG>.

<FIG> shows a schematic diagram of another embodiment of a first communication device <NUM> according to the present disclosure, which may be used as a PHY (physical) layer transmitter. <FIG> illustrates the transmitter operation for a single user (SU) having a single spatial stream but multiple resource units assigned.

The communication device <NUM> comprises a scrambler <NUM> that randomizes the bits of the input bit stream (provided e.g. by a MAC layer) to be transmitted, an LDPC encoder <NUM> that adds parity information to the scrambled bit sequence to obtain code words of an encoded bit stream and a padding unit <NUM> that adds bits such that a certain length of the encoded bit stream is achieved. A multi-RU parser <NUM> allocates the bits to M different Ni-size RUs that are assigned to a single user. A constellation mapper <NUM>, provided per RU, (groupwise) maps qi bits for RUi to a symbol of a constellation and an LDPC tone mapper <NUM>, provided per RU, interleaves symbols over the available tones. The LDPC tone mappers <NUM> are followed by a frequency mapping unit <NUM> that assigns the RUs to their respective location in the frequency domain. An IDFT (inverse discrete Fourier transform) unit <NUM> performs an IDFT operation, followed by GI (guard interval) insertion and windowing of a GI insertion and windowing unit <NUM> and an analog and RF unit <NUM> that up-converts the transmit signal to the desired center frequency.

<FIG> shows a schematic diagram of another embodiment of a first communication device <NUM> according to the present disclosure for a single user (SU) having NSS spatial streams separated by a stream parser <NUM> provided after the padding unit <NUM>. In this configuration, each spatial stream has its own multi-RU parser <NUM>. In the most general case, each constellation mapper <NUM> may have a different number of bits per symbol q and each multi-RU parser <NUM> may have different number of RUs to which it allocates bits. In some cases, it may be applicable to use only one RU, i.e. M=<NUM>, for a certain spatial stream. In this case, the multi-RU parser may be dropped. Furthermore, each multi-RU parser <NUM> has its own frequency mapping unit <NUM> which allocates the RUs in the frequency range.

Following the frequency mapping unit <NUM>, NSS spatial streams are allocated spatially by the spatial mapper <NUM>, i.e. each spatial stream or a linear combination of spatial streams is allocated to a transmit chain or a transmit antenna. The configuration of the spatial mapper <NUM> may be done based on feedback from the receiver to achieve high beamforming gain. It may be envisioned that frequency mapping and spatial mapping are done jointly in a single frequency and spatial mapping unit <NUM>. In case spatial separation is sufficient, RUs may overlap in frequency domain, i.e. a frequency mapping unit <NUM> may allocate RUs such that they overlap with the frequency mapping of another frequency mapping unit <NUM>. Within a frequency mapping unit <NUM>, an overlap is not preferred.

<FIG> shows a schematic diagram of another embodiment of a first communication device <NUM> according to the present disclosure in a multi-user (MU) case, according to which data to U users are multiplexed in one PHY protocol data unit (PPDU). In this embodiment, it is assumed that multiplexing is performed in the frequency domain and that only one transmit antenna is present. Multiplexing may also be done in the spatial domain, i.e. in MU-MIMO fashion, which would result in a combination of the first communication devices <NUM> and <NUM>. In this case the spatial mapping unit <NUM> is configured such that each user can extract its data from the spatially multiplexed PPDU. According to <FIG>, however, the scrambler <NUM>, LDPC encoder <NUM> and padding unit <NUM> are duplicated for each of the U users. The frequency mapping unit <NUM> combines the output of each LDPC tone mapper <NUM> of each user. Frequency mapping is non-overlapping such that each RU can be demodulated without interference.

<FIG> shows a schematic diagram of another embodiment of a second communication device <NUM> according to the present disclosure, which may be used as a PHY layer receiver that is designed to demodulate data transmitted by the first communication device <NUM> shown in <FIG> or <NUM> shown in <FIG>. After the received waveform has been down-converted by the analog and RF unit <NUM>, the guard interval is removed in a guard interval removal and windowing unit <NUM> and a DFT unit <NUM> extracts the subcarriers or tones of an entire OFDM symbol. A frequency demapping unit <NUM> extracts the tones of the resource units that are allocated to the specific user. For each RU an LDPC tone demapping unit <NUM> as well as constellation demapping unit <NUM> is provided. A multi-RU deparser <NUM> performs the inverse operation of the multi-RU parser <NUM> of the first communication device <NUM>. The multi-RU parser <NUM> and the multi-RU deparser <NUM> will be explained in more detail below. After padding is removed by a padding removal unit <NUM>, the received bits are LDPC decoded by an LDPC decoder <NUM> and descrambled by a descrambler <NUM> before they are provided to the user's MAC layer for further processing.

In any one of the embodiments of the first communication device described above the constellation mapper <NUM> creates one symbol once qi bits arrived at its input. Once Ni symbols arrived, a Ni size RU of an OFDM symbol is complete. The assignment of a symbol to tone depends on the LDPC tone mapper <NUM>. In case the LDPC tone mapper <NUM> performs a one to one (<NUM>:<NUM>) mapping, each symbol gets assigned to increasing tone index, i.e. from low to high tone center frequency.

It is assumed that M > <NUM> RUs are allocated to a single user and that <NUM> ≤ i ≤ M holds. It is further assumed that RU indices are sorted by increasing frequency, i.e. the frequency range spanned by RU with i = <NUM> is smaller than that of RU with i = <NUM> and so on.

The multi-RU parser <NUM> is generally difficult to design because RU sizes exist that are a non-integer multiple of each other. Furthermore, it is desired that bit allocation for each RU being part of a multi-RU assignment does not overlap the OFDM symbol boundary. This means that the bit allocation operation for each RU finishes after all Ni tones of RU i are supplied with bits to be transmitted. In other words, a bit allocation operation that works over consecutive OFDM symbols, i.e. multiple of Ni tones, is not desired. This is mainly due to complexity reasons since buffers, which are longer than OFDM symbol size, are avoided by the previous constraint.

<FIG> shows a more detailed diagram of an embodiment of the multi-RU parser <NUM> that operates as follows: A total of P bits is assumed at the input of the multi-RU parser <NUM> which originate from the LDPC encoder <NUM> optionally followed by a padding unit <NUM>.

The multi-RU parser <NUM> operates in a total of C cycles. C is an integer multiple of CO which denotes the number of alternations per OFDM symbol or cycle. In each alternation, p<NUM>(c) consecutive bits are allocated to the first RU of size N<NUM>, followed by another p<NUM>(c) consecutive bits that are allocated to the second RU of size N<NUM>. An alternation ends when pM(c) bits are allocated to the last (Mth) RU of size NM. The number of bits that are allocated to each RU may depend on the actual alternation index c within an OFDM symbol, i.e. <NUM> ≤ c ≤ CO. Thus, alternation cj assigns <MAT> bit to resource units. In case more input bits are present than can be allocated in CO alternations, further cycles, i.e. multiples of CO alternations are executed in the same way as the first CO alternations. Thus, the number of cycles, which equals the number of OFDM symbols, is <MAT> and the number of bits allocated within each OFDM symbol (in CO alternations) is <MAT> <FIG> shows the previously described multi-RU parser operation in bit-wise operation.

The padding unit <NUM> operates such that P is an integer multiple of the number of bits allocated in CO alternations. This means that CO alternations are completed. This causes the number of cycles C to be an integer number. The number of padded bits complements the total number of bits at the output of the LDPC encoder <NUM> in the following sense: <MAT> with <MAT> and <MAT> wherein <MAT> denotes the number of cycles and is derived by rounding Cfrac up to the next integer.

<FIG> depicts a more detailed diagram of an embodiment of the multi-RU deparser <NUM> that operates as follows. In principle, it performs the inverse operation of the multi-RU parser <NUM>. Conceptually, the multi-RU deparser <NUM> has a buffer memory at each input port that stores the bits that originate from each constellation demapper <NUM>. Once the bits of an entire OFDM symbol are available in the memory, the multi-RU deparser <NUM> assembles the output bit stream by concatenating the first p<NUM>(c = <NUM>) bits from the memory of the first N<NUM>-tone RU with the first pi(c = <NUM>) bits from the memory of the ith Ni-tone RU and so on (i = <NUM>,. , M - <NUM>). After the first pM(c = <NUM>) bits from the memory of the MTh NM-tone RU have been concatenated, the next alternation (if present) is triggered and p<NUM>(c = <NUM>) bits with index p<NUM>(c = <NUM>) + <NUM> to p<NUM>(c = <NUM>) + p<NUM>(c = <NUM>) are concatenated to the output bit stream. This process continues until the last alternation CO of the current OFDM symbol is reached. At this time each memory is empty and bits of the next OFDM symbol can be stored. Depending on hardware implementation, an output buffer of the output of the multi-RU deparser <NUM> may be needed on top in order to implement the bit concatenation.

There are several options for pi(c) and CO.

According to a first option continuous bit allocation (CO = <NUM>, pi(c) = pi) may be applied. In an implementation, the multi-RU parser operates such that consecutive output bits of the LDPC encoder <NUM> (or padding unit <NUM>) are allocated consecutively to tone index. Thereby, multiple RUs are thought of lying (virtually) side by side, i.e. the number of available tones in multi-RU is <MAT>. The multi-RU parser <NUM> allocates pi = qi · Ni bits to Ni tones consecutively from i = <NUM>,. As can be seen from equation (<NUM>), CO = <NUM> holds.

Examples illustrating the first option are shown in <FIG>. In <FIG>, for instance, one cycle comprises a single alternation since in a single alternation all bits are allocated to an OFDM symbol of the respective RU.

This first option is simple to implement, but diversity may not fully be exploited. The latter is in particular true if the RUs are non-contiguous, i.e. reside in different regions of the overall bandwidth. Diversity may be enhanced by a single LDPC tone mapper <NUM>' as illustrated in <FIG> showing a schematic diagram of another embodiment of a first communication device <NUM>, instead of RU-distinct LDPC tone mappers <NUM> as used in the embodiments shown in <FIG>. In the embodiment of <FIG> the joint LPDC tone mapper <NUM>' works on tones but not bits, so that a defect tone may affect a block of qi bits that may be hard to correct by the LDPC decoder <NUM> which is in favor of distributed error patterns. Furthermore, a joint LDPC tone mapper <NUM>' comes with delay and high memory complexity because many tones, namely <MAT>, need to be interleaved.

Alternating bit assignment may avoid the drawback of the continuous bit mapping as will be described in the following.

Before going to the details of how pi(c) is selected with alternating bit assignment, it is important to consider the effect of constellation mapping. In WLAN (IEEE802. <NUM>), the constellation mapping is done such that the reliability of bits is sorted in decreasing order and per dimension of the constellation diagram as shown in <FIG> for <NUM>-QAM, i.e. q = <NUM> bits per symbol.

For each dimension, the most reliable bit is the bit that differentiates between positive and negative axis. In other words, this bit determines if the signal point in the considered dimension has a positive or negative sign. The second most reliable bit is the bit that differentiates within the positive or negative half-space. In other words, this bit determines which amplitude level the signal point in the considered dimension has. The larger the differentiated amplitude levels are, the more reliable the related bit is. As for <NUM>-QAM shown in <FIG> there are just two bits per dimension.

In the following, three different cases of the minimum number of consecutive bits are considered that are allocated per each alternation as a function of qi (when applicable):.

In the following, the three cases are abbreviated by Qi which is <MAT>.

The respective pi(c) may be an integer multiple of Qi and the actual option that is implemented behind the Qi value may be different for each i of a multi-RU allocation, i.e. Qi values may be different for different i although qi is the same. As will be outlined below, these options differ in the diversity that is achieved.

Different levels of diversity are achieved by the different options of Qi. In multi-RU allocation, it is desired to generate distributed bit reliability because this helps the LDPC decoder <NUM> to reconstruct erroneous bits. Thereby, reliability levels imposed by constellation diagram (as shown in <FIG>) as well as reliability levels imposed by multiple RUs may be considered. <FIG> shows the distribution of reliability levels over bit index for four different options. Two RUs, each modulated with <NUM>-QAM and same Qi option, are assumed. <FIG> shows bit reliability for Qi option a), <FIG> shows bit reliability for Qi option b), and shows bit reliability for Qi option c). The level of distribution decreases from <FIG>, which can be readily seen by assuming reliability levels of the second RU being zero.

<FIG> shows another variant that corresponds to the variant shown in <FIG>, but has in inverted bit allocation for RU <NUM>, i.e. the reliability of bits is not high to low but low to high. In the general case with M > <NUM>, every odd allocation is done in consecutive order whereas every second allocation is done in inverse order. For qi ≥ <NUM>, the option in <FIG> may achieve an even higher diversity order as the option in <FIG>. For the inverse operation, the parser operation as shown in <FIG> may be changed as illustrated in <FIG> for the M = <NUM> case. Operation as shown in <FIG> is slightly more complicated to implement, because the parser needs to store bits before they can be output.

According to a second option RU size independent alternating bit allocation (CO > <NUM>, pi(c) e {<NUM>; Qi}) may be applied. In an implementation, the multi-RU parser <NUM> operates such that a group of Q<NUM> consecutive bits of the LDPC encoder <NUM> (or padding unit <NUM>) is allocated to a tone of first RU. After that another group of Q<NUM> bits is allocated to the second RU and so on. Once a group of QM bits has been allocated to Mth RU, the process starts from the beginning. Since the RU sizes Ni may be different, a small size RU of an OFDM symbol is filled earlier than a large size RU which conflicts with the constraint that multi-RU parsing should not be done over multiple OFDM symbols. In order to evite, the bit allocation to a small RU is stopped once it has been filled. Thus, pi(c) has a segment-wise definition: <MAT> wherein <MAT> holds, meaning there are as many alternations as are needed to fill the RU unit that requires the most alternations within a cycle to be completely filled.

Examples illustrating the second option are shown in <FIG>. In <FIG>, for instance, one cycle comprises a <NUM> alternations since in <NUM> alternations all bits are allocated to an OFDM symbol of the respective RU. As can be seen, the <NUM>-tone RU is filled earlier than the <NUM>-tone RU which causes p<NUM>(c) = <NUM> for <NUM> ≤ c ≤ <NUM>. In both examples the first ratio used for allocation of a first portion of the bits (i.e., the bits allocated in the alternations <NUM> to <NUM>) allocated to the two resource units is <NUM>:<NUM> and the second ratio used for allocation of a second portion of the bits (i.e., the bits allocated in the alternations <NUM> to <NUM>) allocated to the two resource units is <NUM>:<NUM>.

According to a third option RU size dependent alternating bit allocation (CO > <NUM>, pi(c) = pi) may be applied. In an implementation, the multi-RU parser <NUM> operates such that consecutive output bits of the LDPC encoder <NUM> are allocated alternating to the RUs. In contrast to the second option, the number of assigned bits per RU is proportional to its number of tones.

This means that a large size RU gets more bits allocated per alternation compared to a small size RU. Prerequisite is that <MAT> is an integer number and that all originate from same option with Qi ≠ <NUM>. In this case all RUs of an OFDM symbol are filled at the same time after <MAT> alternations.

The third option achieves higher diversity than the second option in scenarios where a small size RU is combined with a large size RU, because a weak link quality small size RU can be compensated by a fair link quality large size RU. This is because the bits of small size RU are distributed over the entire OFDM symbol. In addition, each group of Qi weak bits of the small size RU is separated by various groups of Qi fair bits of the large size RU.

An example illustrating the second option is shown in <FIG>. In <FIG> one cycle comprises a <NUM> alternations since in <NUM> alternations all bits are allocated to an OFDM symbol of the respective RU.

According to a fourth option RU size dependent bit assignment including non-alternating bit assignment may be applied. In an implementation, the third option is applied together with pre- and post-bit assignment. The operation is shown in <FIG>. The consecutive bits that are allocated in the pre-bit assignment before the alternating operation are labeled with si, whereas the consecutive bits that are allocated in the post-bit assignment after the alternating operation are labeled with ti. Inbetween the pre- and post-bit assignment, alternating bit assignment as shown in <FIG> is performed. <FIG> shows the operation for a single OFDM symbol. Thus, if si = ti = <NUM>, the same behavior as before is achieved. The pre- and post-assignment can be flexibly applied, i.e. the post-assignment for example may be done in the middle of the alternating operation, i.e. after <MAT> alternations. This may be important to avoid long bit allocations to single RU in case of OFDM symbol transitions.

Pre- and post-bit assignment may be used in case pi of the third option e.g. results in a non-integer number. In this case, pi is rounded to the closest integer number and the remaining bits that are missing to complete an OFDM symbol are computed.

Any ri ≠ <NUM> needs to be allocated before the next OFDM symbol starts. In WLAN case and for most other applicable communication systems, ri ≥ <NUM> holds. This is because larger RUs have more available tones per frequency unit than small RUs, hence the nominal spectral efficiency increases with RU size.

It is desirable to equally distribute ri bits either via pre- and post-bit assignment and/or via alternating bit assignment. Thus, several options exists to implement ri > <NUM>:.

In case of pi(c) being variable, any pi(c) pattern may be envisioned as long as the total number of allocated bits does not change. In examples, it is assumed that the pi(c) pattern are sorted in descending order in sub-cycles.

In any case, it is desired that si equals ti whenever possible. Thus, if the number of bits to be represented by pre- and post-bit assignment is an even integer, si = ti holds otherwise, si = ti + <NUM> or ti = si + <NUM> holds. The operation shown in <FIG> changes equations (<NUM>) to (<NUM>) as follows: <MAT> <MAT> <MAT> <MAT>.

Examples illustrating the fourth option are shown in <FIG>. In <FIG>, for instance, one cycle comprises a <NUM> alternations plus a pre-assignment and a post-assignment since in <NUM> alternations plus the pre-assignment and the post-assignment all bits are allocated to an OFDM symbol of the respective RU.

In the example of <FIG>, generally per alternation (of <NUM> alternations) <NUM> bit is allocated to the first RU and <NUM> bits are allocated to the second RU. Then, there are <NUM> remainder bits that still have to be allocated to the second RU. This is done such that in each of a pre-assignment and a post-assignment <NUM> bits are allocated to the second RU (i.e. six remainder bits in total) and that in each eleventh allocation (starting e.g. with the first allocation; each group of eleven consecutive alternations forming a sub-cycle one additional bit (i.e. <NUM> remainder bits in total) in addition to the regular four bits is allocated to the second RU (i.e. five bits per allocation).

In the example shown in <FIG> the first ratio used for allocation of a first portion of the bits (i.e., the bits allocated in the alternations <NUM> to <NUM>) allocated to the two resource units is <NUM>:<NUM> and the second ratio used for allocation of a second portion of the bits (i.e., the bits allocated in the pre- and post-assignments) allocated to the two resource units is <NUM>:<NUM>. In the example shown in <FIG> the first ratio used for allocation of a first portion of the bits (i.e., the bits allocated in the alternations <NUM> to <NUM>) allocated to the two resource units is <NUM>:<NUM> and the second ratio used for allocation of a second portion of the bits (i.e., the bits allocated in the pre- and post-assignments) allocated to the two resource units is <NUM>:<NUM>. In the example shown in <FIG> the first ratio used for allocation of a first portion of the bits (i.e., the bits allocated in the alternations <NUM> to <NUM>) allocated to the two resource units is <NUM>:<NUM> and the second ratio used for allocation of a second portion of the bits (i.e., the bits allocated in the pre- and post-assignments) allocated to the two resource units is <NUM>:<NUM>. In the example shown in <FIG> the first ratio used for allocation of a first portion of the bits (i.e., the bits allocated in the alternations <NUM> to <NUM>, <NUM> to <NUM>, etc.) allocated to the two resource units is <NUM>:<NUM>, the second ratio used for allocation of a second portion of the bits (i.e., the bits allocated in the alternations <NUM>, <NUM>, <NUM>, etc.) allocated to the two resource units is <NUM>:<NUM>, and a third ratio used for allocation of a third portion of the bits (i.e., the bits allocated in the pre- and post-assignments) allocated to the two resource units is <NUM>:<NUM>.

Generally, the behavior of the bit allocation to the cycles is such that, from cycle to cycle, the same number of bits is assigned to the corresponding alternations of the respective cycles. For instance, if in a first cycle, a cycle has <NUM> alternations, wherein <NUM> bit is assigned to RU1 and <NUM> bits are assigned to RU2 in each alternation, the subsequent cycles follow the same allocation of bits (e.g. in the second cycle there are also <NUM> alternations, wherein <NUM> bit is assigned to RU1 and <NUM> bits are assigned to RU2 in each alternation).

<FIG> shows examples illustrating a fifth option for multi-RU allocation using different modulation orders. For instance, in the example shown in <FIG> QPSK (modulation order <NUM>) is used for modulation of the bits allocated to the first RU (having <NUM> tones) and BPSK (modulation order <NUM>) is used for modulation of the bits allocated to the second RU (having <NUM> tones). In this case, Qi (defining the minimum number of consecutive bits that are allocated per each alternation as a function of qi) is selected according to the above-described case c), i.e. Qi = qi bits per alternation, meaning that Q<NUM> = <NUM> and Q<NUM> = <NUM>. Hence, for the first RU two bits are assigned to each tone and for the second RU one bit is assigned to each tone. Then, as described above with respect to the third option, per alternation (of <NUM> alternations of one cycle) two bits are allocated to the first RU and two bits are allocated to the second RU.

In the example shown in <FIG> QPSK (modulation order <NUM>) is used for modulation of the bits allocated to the first RU (having <NUM> tones) and <NUM>-QAM (modulation order <NUM>) is used for modulation of the bits allocated to the second RU (having <NUM> tones). In this case, Qi is selected according to the above-described case c), i.e. Qi = qi bits per alternation, meaning that Q<NUM> = <NUM> and Q<NUM> = <NUM>. Hence, for the first RU two bits are assigned to each tone and for the second RU four bits are assigned to each tone. Then, per alternation (of <NUM> alternations) two bits are allocated to the first RU and sixteen bits are allocated to the second RU. The remainder of eight bits to be allocated to the second RU is assigned to a pre-assignment at the start of the cycle and to a post-assignment at the end of the cycle. In the example shown in <FIG> the first ratio used for allocation of a first portion of the bits (i.e., the bits allocated in the alternations <NUM> to <NUM>) allocated to the two resource units is <NUM>:<NUM> and the second ratio used for allocation of a second portion of the bits (i.e., the bits allocated in the pre- and post-assignments) allocated to the two resource units is <NUM>:<NUM>.

In the example shown in <FIG> QPSK (modulation order <NUM>) is used for modulation of the bits allocated to the first RU (having <NUM> tones) and <NUM>-QAM (modulation order <NUM>) is used for modulation of the bits allocated to the second RU (having <NUM> tones). In this case, Qi is selected according to the above-described case b), i.e. <MAT> bits per alternation, meaning that Q<NUM> = <NUM> and Q<NUM> = <NUM>. Hence, for the first RU one bit is assigned to each tone and for the second RU eight bits are assigned to each tone. Then, per alternation (of <NUM> alternations) one bit is allocated to the first RU and eight bits are allocated to the second RU. The remainder of eight bits to be allocated to the second RU is assigned to a pre-assignment at the start of the cycle and to a post-assignment at the end of the cycle. In the example shown in <FIG> the first ratio used for allocation of a first portion of the bits (i.e., the bits allocated in the alternations <NUM> to <NUM>) allocated to the two resource units is <NUM>:<NUM> and the second ratio used for allocation of a second portion of the bits (i.e., the bits allocated in the pre- and post-assignments) allocated to the two resource units is <NUM>:<NUM>.

In the example shown in <FIG> <NUM>-QAM (modulation order <NUM>) is used for modulation of the bits allocated to the first RU (having <NUM> tones) and QPSK (modulation order <NUM>) is used for modulation of the bits allocated to the second RU (having <NUM> tones). In this case, Qi is selected according to the above-described case b), i.e. Qi = qi bits per alternation, meaning that Q<NUM> = <NUM> and Q<NUM> = <NUM>. Hence, for the first RU six bits are assigned to each tone and for the second RU <NUM> bits are generally assigned to each tone. Then, per alternation (of most of the <NUM> alternations) <NUM> bits are allocated to the first RU and eight bits are allocated to the second RU. The remainder of <NUM> bits to be allocated to the second RU is allocated as follows: <NUM> bits are allocated to a pre-assignment at the start of the cycle, <NUM> bits are allocated to a post-assignment at the end of the cycle, and additional two bits are allocated to each first allocation of each sub-cycle comprising eleven alternations (i.e. to each eleventh alternation <NUM> bits instead of <NUM> bits are allocated). This option achieves higher diversity because the remaining bits are distributed over the entire OFDM symbol by the altnerations <NUM>, <NUM>, <NUM>, etc. This minimizes number of bits in pre- and post-assignment which is one of the optimization goals. In the example shown in <FIG> the first ratio used for allocation of a first portion of the bits (i.e., the bits allocated in the alternations <NUM> to <NUM>, <NUM> to <NUM>, etc.) allocated to the two resource units is <NUM>:<NUM>, the second ratio used for allocation of a second portion of the bits (i.e., the bits allocated in the alternations <NUM>, <NUM>, <NUM>, etc.) allocated to the two resource units is6:<NUM>, and a third ratio used for allocation of a third portion of the bits (i.e., the bits allocated in the pre- and post-assignments) allocated to the two resource units is <NUM>:<NUM>.

<FIG> shows Table <NUM> that gives examples for pi, si, and ti for various combinations of RUs of Table <NUM> as well as for various options.

The order of RUs is exemplary and may change depending of the actual location of a RU within the frequency band as outlined above. The bit allocation sticks however to the particular RU size. The entries in Table <NUM> (<FIG>) are valid under the following assumptions: Entries according to option <NUM> are always valid. Entries according to options <NUM>, <NUM>, and <NUM> are valid, when Qi is always selected from same option a), b), or c) for each RU. If selected according to option a), i.e. Qi = <NUM>, qi = qj for all i ≠ j, i.e. all RUs have the same constellation mapping order, shall be additionally fulfilled. In the following some of the entries in Table <NUM> will be explained by way of examples.

For the type <NUM>-tone RU + <NUM>-tone RU (according to row <NUM> of Table <NUM>, with Q=q) the following bit allocations apply:.

For the type <NUM>-tone RU + <NUM>-tone RU (according to row <NUM> of Table <NUM>, with Q=q/<NUM>) the following bit allocations apply:.

For the type <NUM>-tone RU + <NUM>-tone RU (according to row <NUM> of Table <NUM>, with Q=<NUM>; the Q=<NUM> case is basically different because of varying vector length and the need of the same modulation order for all RUs) the following bit allocations apply (in this case each RU must have same modulation order, i.e. q<NUM>=q<NUM>=q):.

For the type <NUM>-tone RU + <NUM>-tone RU (according to row <NUM> of Table <NUM>, with Q=<NUM>) the following bit allocations apply:.

For the type <NUM>-tone RU + <NUM>-tone RU (according to row <NUM> of Table <NUM>, with Q=<NUM>; in this case each RU must have same modulation order, i.e. q<NUM>=q<NUM>=q) the following bit allocations apply:.

The present disclosure provides the advantages that the bit parser operation for allocation of multiple resource units to a single user achieves high diversity with the error correction codes, e.g. LDPC codes, and constellation diagrams provided e.g. by IEEE <NUM> WLAN standard. Further, in requires a bit parser operation with low memory requirements that simplifies implementation and enables low latency decoding. Still further, optional bit padding can be adapted to the needs for the multi-RU bit parser operation.

Further, such a software may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Claim 1:
First communication device configured to communicate with a second communication device, the first communication device comprising circuitry configured to
- encode data words of an input bit stream to be transmitted to the second communication device into code words of an encoded bit stream;
- allocate the bits of the encoded bit stream to two or more resource units assigned to the second communication device and covering different subsections of a channel bandwidth,
wherein at least two of the two or more resource units cover subsections having a different number of tones,
wherein a number of bits of the encoded bit stream allocated to a resource unit is proportional to the number of tones of the subsection covered by the resource unit,
wherein the bits to be allocated to the two or more resource units are alternately allocated to the two or more resource units in a cycle having two or more alternations,
wherein, for a first portion of the bits to be allocated to the two or more resource units in one cycle, a first ratio of predetermined numbers of consecutive bits alternately allocated to two resource units is based on the number of tones of subsections covered by said two resource units and the modulation order of a modulation of the bits allocated to the respective resource unit, and
wherein, for a second portion of the bits to be allocated to the two or more resource units in one cycle, a second ratio of predetermined numbers of consecutive bits alternately allocated to two resource units is different from the first ratio, wherein the second ratio is formed by a remainder of bits that are not allocated to the two or more resource units as first portion of bits according to the first ratio,
- groupwise map, per resource unit, bits of the encoded bit stream allocated to the respective resource unit to symbols of a constellation, and
- assign the resource units to the respective subsection of the channel bandwidth in the frequency domain.