First and second communication devices and communication methods

Abstract

It is an object of the present invention to provide a communication device and a communication method that improve detection, channel estimation and interference suppression in a receiver, and to provide a corresponding computer program and a non-transitory computer-readable recording medium for implementing the communication method. [Solution] 11. A first communications device configured to transmit data to a second communications device, comprising: a circuit configured to generate a second number of mutually orthogonal sequences; generate one or more third number of spatial streams, each carrying payload data; divide each of a first number of training symbols, each spanning a plurality of tones, into a fourth number of tone sets; divide each orthogonal sequence into a fourth number of portions, generate a training field by mapping elements of corresponding portions of the orthogonal sequences to the tone sets of the training symbols; and place the training field before and / or between the payload data of the spatial streams to enable channel estimation by the second communications device.

Description

[Technical Field]

[0001] The present disclosure relates to first and second communication devices configured to communicate with each other and a communication method. [Background technology]

[0002] Wireless communications suffer from interference when multiple transmitters simultaneously access the same frequency channel. In distributed access technologies such as WLAN, transmitters compete for the channel, potentially resulting in collisions. Furthermore, in scenarios with a high density of stations (STAs) and access points (APs), basic service sets (BSSs) may overlap, potentially resulting in unwanted interference. WLAN also operates in unlicensed spectrum, meaning that other transmitters from other technologies can use the same wireless channel. For these reasons, interference can occur during communications between STAs and APs, or between APs and STAs, leading to communication interruptions. This means that the receiver cannot decode the information, forcing the transmitter to retransmit the message, resulting in reduced reliability, reduced throughput, and increased latency.

[0003] The "Background" discussion provided herein is intended to provide a general context for the present disclosure. The inventors' work, to the extent described in this Background section, is not admitted expressly or implicitly as prior art to the present disclosure, as are aspects of the description that are not admitted as prior art at the time of filing. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides a communication device and a communication method that improves detection, channel estimation, and interference suppression in a receiver, and also provides a corresponding computer program and a non-transitory computer-readable storage medium for implementing the communication method. [Means for solving the problem]

[0005] According to one aspect, there is provided a first communications device configured to transmit data to a second communications device, the first communications device comprising: circuitry configured to: generate a second number of mutually orthogonal sequences; generate one or more third number of spatial streams, each of which carries payload data; divide each of a first number of training symbols, each of which spans a plurality of tones, into a fourth number of tone sets; generate a training field by dividing each orthogonal sequence into a fourth number of portions and mapping elements of corresponding portions of the orthogonal sequences to the tone sets of the training symbols; and position the training field before and / or between the payload data of the spatial streams to enable channel estimation by the second communications device.

[0006] According to another aspect, a second communications device configured to receive data from a first communications device, the second communications device comprising: circuitry configured to obtain one or more initial channel observations for one or more channels between the first communications device and the second communications device based on at least a portion of a training field, the training field being disposed before and / or between payload data of one or more third number of spatial streams received from the first communications device, each spatial stream carrying payload data, each of a first number of training symbols being divided into a fourth number of tone sets spanning a plurality of tones, each of a second number of mutually orthogonal sequences being divided into a fourth number of portions, elements of corresponding portions of the orthogonal sequences being mapped to the tone sets of the training symbols; generating a training field; performing interference channel estimation for the one or more potential interference channels based on another portion of the training field; and performing interference suppression based on interference channel estimation information obtained from the interference channel estimation.

[0007] According to yet another aspect, there is provided a computer program comprising program means which, when executed on a computer, causes a computer to perform the steps of the methods disclosed herein, and a non-transitory computer-readable recording medium storing a computer program product which, when executed by a processor, causes a computer to perform the methods disclosed herein.

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

[0009] One aspect of the present disclosure is to enable a receiver (i.e., a second communication device) to obtain observations of an interfering channel, thereby maintaining the intended low transmitter signaling overhead and high channel estimation quality.

[0010] In this context, the terms "intended transmitter" and "intended STA" refer to a device (also referred to in this disclosure as a "first communication device") that transmits a signal that a receiver (e.g., another station or AP; referred to in this disclosure as a "second communication device") wants to decode. This means that the receiver can achieve synchronization on a data unit, e.g., a PHY protocol data unit (PPDU; also generally referred to in this disclosure as a "data unit") transmitted from the intended transmitter and decode a signaling field that may precede a training field. An "interfering transmitter" or "interferer" (also referred to in this disclosure as a "third communication device") refers to another device (e.g., a STA or AP) that is transmitting a signal that disrupts communication between the intended transmitter and the receiver.

[0011] The present disclosure enables interference detection, interference channel estimation, and interference mitigation at a receiver by designing a sounding method that increases the number of channel observations at the receiver compared to current standard implementations. In an embodiment for increasing the number of channel observations, an orthogonal (training) sequence is mapped around several frequency tones. This allows the receiver to improve decoding performance in the presence of interference, increasing reliability and reducing the number of data retransmissions. Reducing the number of data retransmissions reduces latency and improves throughput.

[0012] The foregoing paragraphs have been provided by way of a general introduction and are not intended to limit the scope of the claims. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0013] A more complete understanding of the present disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 illustrates the three different HE-LTF types defined in the WLAN 802.11 ax amendment. [Figure 2] FIG. 2 is a diagram illustrating an example of orthogonal sequence mapping with four spatial streams. [Figure 3] FIG. 3 is a schematic diagram of a generator for generating the sounding field described in WLAN 802.11 ax. [Figure 4] FIG. 4 is a flow chart of a method for dynamically adjusting the number of training symbols per data exchange between communication devices. [Figure 5] FIG. 5 is a diagram illustrating a communication system including a first communication device and a second communication device according to the present disclosure. [Figure 6] FIG. 6 is a flowchart of a first communication method of a first communication device according to an embodiment of the present disclosure. [Figure 7] FIG. 7 is a flowchart of a second communication method of a second communication device according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is a diagram illustrating an example of orthogonal sequence mapping with three spatial streams according to the present disclosure. [Figure 9] FIG. 9 illustrates an example training field with two training symbols according to the present disclosure. [Figure 10] FIG. 10 shows an example of the magnitude and phase of the autocorrelation function between tones of a typical WLAN channel model. [Figure 11] FIG. 11 is a flow chart of a method for selecting the number of mapped adjacent non-empty tones. [Figure 12] FIG. 12 is a flowchart of a first communication method of a first communication device according to another embodiment of the present disclosure. [Figure 13] FIG. 13 is a flowchart of a second communication method of a second communication device according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] The WLAN 802.11 standard allows the transmitter to adapt the modulation and coding scheme (MOS) to the channel conditions in order to control the level of redundancy in the transmitted information, thereby ensuring robustness against interference at the expense of reduced throughput and increased latency.

[0016] MIMO technology has been incorporated into WLANs for decades and offers the possibility of combating interference through signal processing without adding significant overhead. If the receiver is equipped with multiple antennas, it can use a sounding signal sent by the transmitter to estimate the channel and suppress interference between different spatial streams sent by one or more other (i.e., third-party) transmitters.

[0017] The main limitation of WLAN is that only the intended transmitter transmits the sounding signal: there are no established sounding signals or procedures to detect the presence of interference in an ongoing transmission or to estimate the interfering channel if interference from an unintended transmitter occurs due to collisions or external sources.

[0018] The sounding signals in the latest WLAN 802.11 ax amendments are called high-efficiency long training fields (HE-LTFs). These signals are added either within the preamble of the PHY protocol data unit (PPDU) or between PPDUs as midambles inserted at given intervals to deal with fast channel variations.

[0019] Referring now to the drawings, where like reference numbers refer to the same or corresponding parts throughout the several views, FIG. 1 illustrates three different HE-LTF types 1, 2, and 3 defined in the WLAN 802.11ax amendment. Each HE-LTF corresponds to one OFDM symbol (also referred to herein as a "training symbol" or "HE-LTF symbol") consisting of many tones across the bandwidth of the channel being used. There are three HE-LTF symbols, types 1, 2, and 3, which differ in duration and number of filled tones: a first type 1 (referred to as 1xHE-LTF, shown in FIG. 1A) with a 3.2 μs duration of each training symbol; a second type 2 (referred to as 2xHE-LTF, shown in FIG. 1B) with a 6.4 μs duration of each training symbol; and a third type 3 (referred to as 3xHE-LTF, shown in FIG. 1C) with a 12.8 μs duration of each training symbol. The more tones filled, the longer each HE-LTF symbol is. The number of HE-LTF symbols is N. HE-LTF and N is set to satisfy the following equation 1. sts The selection is based on the total number of spatial streams, denoted by

[0020]

number

[0021] As also shown in Figure 1, training symbols 1, 2, and 3 each have a number of reserved tones set to "0", empty LTF tones set to "0", and non-empty LTF tones set to "+1" or "-1".

[0022] Based on these designs of the HE-LTF signal, the receiver can estimate the MIMO channel between the receiver and the transmitter at each non-empty tone. The channel estimate corresponding to the empty tone is calculated through an interpolation technique that is implementation-dependent and outside the scope of this disclosure, but is commonly known to those skilled in the art. For each non-empty data tone, N HE-LTFsymbols of length N sent by the transmitter during HE-LTF The MIMO channel estimates are calculated at the receiver based on the orthogonal sequences P HE-LTF (also referred to herein as orthogonal sequence mapping matrix or HE-LTF mapping matrix), and each spatial stream has N HE-LTF The rows of this matrix to be transmitted are assigned as shown in Figures 2 and 3 for the case of =4.

[0023] Figure 2 shows an example of orthogonal sequence mapping with four spatial streams (SS). In this context, the term "orthogonal" refers to HE-LTF This means that the matrix multiplication of different rows of σ is zero. Thus, the receiver can obtain observations of the channel between itself and each spatial stream sent by the transmitter without causing interference between the spatial streams.

[0024]

number

[0025] More specifically, in this case, the training symbols are called HE-LTF. First, the following parameters are determined: HE-LTF tone sequence (HELTF), number of HE-LTF symbols (N HE-LTF ), and the number of spatial streams (N sts ) is chosen. The orthogonal sequence is a square P HE-LTF The number of elements in each orthogonal sequence is taken as the rows of a matrix (i.e., a matrix with equal numbers of rows and columns). HE-LTF Each spatial stream is assigned an orthogonal sequence. For each tone (indexed by k, the procedure is the same for all tones), each orthogonal sequence is multiplied with the corresponding HE-LTF tone sequence in the multiplication module 41. This results in N HE-LTFHE-LTF symbols are generated. For example, N sts =2, N HE-LTF = 2, the following equation 3 holds.

[0026]

number

[0027] After cyclic shifting in a cyclic shift diversity (CSD) module 42, which introduces a cyclic time shift to the signal of each spatial stream to avoid unintended beamforming effects when transmitting multiple spatial streams, the symbols from all spatial streams are combined with a Q matrix by matrix multiplication in a combining module 43 to generate symbols to be transmitted by each transmit antenna. The Q matrix is ​​determined by the number of transmit antennas (N TX ) 45 and the same number of rows as the number of spatial streams (N sts ) and has the same number of columns as the spatial streams (N sts ) and the same number of rows and the number of HE-LTF symbols (N HE-LTF ) and a matrix A with the same number of columns as k It can be seen that the training symbols can be represented by

[0028] The transmitted symbols of each Inverse Discrete Fourier Transform (IDFT) module 44 and each transmit antenna 45 are subjected to a matrix multiplication QA k Following the example above, N TX = 2 and assume direct spatial mapping where each spatial stream is assigned to one antenna, i.e., Q is the identity matrix, then the following holds:

[0029]

number

[0030] The transmission of training symbols per antenna is as follows:

[0031]

number

[0032]

number

[0033] The maximum number of channels that can be estimated at the receiver is P HE-LTF number of rows, i.e., the number of HE-LTF symbols in the WLAN 802.11 ax amendment, N HE-LTF This is limited by the number of spatial streams, N sts To detect and estimate more channels than P HE-LTF This means that the size of

[0034] To suppress interfering signals in MIMO processing, the receiver needs to obtain an estimate of the interfering channel. This means observing the interference in the absence of the intended STA. However, this is not possible in current implementations of WLAN 802.11 ax, since the number of HE-LTF symbols is almost always designed to match the number of spatial streams. Furthermore, several observations are required to obtain a good estimate of the interfering channel, and the maximum number of unused HE-LTF symbols is one.

[0035] The present disclosure aims to enable interference detection, interference channel estimation, and interference suppression at the receiver by designing a new sounding method that increases the number of channel observations compared to current standard implementations. Therefore, for this purpose, an Extended Long Training Field (E-LTF) is envisioned, which is constructed based on a modified HE-LTF signal. Several embodiments for such modifications are described below.

[0036]

number

[0037] The number of E-LTF symbols to be transmitted to generate the E-LTF signal is defined. In the WLAN 802.11ax amendment, the number of E-LTF symbols is selected based solely on the number of spatial streams. In contrast, according to the present disclosure, the number of E-LTF symbols is selected to balance time overhead and MIMO interference suppression performance. Therefore, in addition to different embodiments of the proposed sounding method, a method for selecting the number of E-LTF symbols is disclosed as described below.

[0038] First, starting from the minimum number of E-LTF symbols, we evaluate the boundaries of the E-LTF symbols that can be transmitted. sts There are at least as many orthogonal sequences (i.e., P shown in Figure 2) as there are spatial streams, as shown in HE-LTF P replaced by E-LTF Therefore, the minimum number of E-LTF symbols is N sts ×N sts The smallest number of P E-LTF It also supports the use of matrices, and the number of spatial streams, N, to obtain an estimate of the interference. sts At least one more channel observation than N must be available at the receiver. Based on these conditions, minE-LTF It is possible to set a minimum number of E-LTF symbols, denoted by

[0039] Regarding the maximum number of E-LTF symbols, the following considerations apply: Because E-LTF symbols are used for channel estimation, the channel must be nearly static for the duration of the PPDU, or until the midamble is transmitted, which is called the coherence time. This can be estimated by any device based on statistical measurements of the signal (e.g., during the device's association process to a BSS). Therefore, the number of E-LTF symbols is such that the duration of the E-LTF is at least one OFDM symbol shorter than the coherence time.

[0040] However, in practice, it is desirable to have a small number of training symbols compared to the data symbols in order to reduce time overhead and achieve high throughput and / or low latency. maxE-LTF The maximum number of E-LTFs, denoted by, depends on the specific receiver implementation and channel conditions to limit the time overhead and achieve the desired performance of throughput and latency.

[0041] The performance of MIMO suppression techniques at a receiver depends on the specific implementation and channel conditions. Therefore, it is desirable to adapt the number of E-LTF symbols to each specific situation. Figure 4 is a flowchart of a method 100 for dynamically adjusting the number of E-LTF symbols per data exchange between communication devices, where N margin is the number of E-LTF symbols added or subtracted in each data exchange, and Δ margin is the interference index margin.

[0042] In a first step 101, before the first PPDU exchange, the transmitter sets the number of E-LTF symbols to a minimum value NminE-LTF. The number of E-LTF symbols can then be increased or decreased based on a notification made by the receiver after evaluating the performance of MIMO interference suppression in previous PPDUs. An indicator in the signaling field of the response message (e.g., Ack or MCS Feedback) can be assumed so that the receiver can indicate to the transmitter whether to increase or decrease the number of E-LTF symbols, for the transmitter to check and decide in step 102.

[0043] In the absence of notification, the interference indicator averaged over time exceeds the configured minimum value by a margin Δ margin(which is confirmed in step 103), the transmitter can increase the number of E-LTF symbols in step 105. This indicator can be generated based on one or more of the following: signal-to-interference-and-noise ratio (SINR), received power level, number of active BSSs, number of past collisions, etc. If the interference indicator averaged over time exceeds the above-mentioned value, it means that there are many potential interfering devices, and the receiver would benefit from having more E-LTF symbols for interference suppression. Conversely, if the interference indicator averaged over time is less than the set minimum value by a margin Δ margin If it is less than the value minus (which is checked in step 104), it means that the number of potential interferences is low, and therefore the number of E-LTF symbols is reduced in step 106 to reduce the time overhead.

[0044] If none of the above conditions are met, the number of E-LTF symbols remains unchanged until the next transmission. If there is a notification, as confirmed in step 102, the number of E-LTF symbols is increased in step 105 or decreased in step 106 according to the notification. To support the method shown in Figure 4, the transmitter can, for example, add an indicator to a signaling field in the PHY preamble to indicate to the receiver the number of E-LTF symbols transmitted in PPUD. N maxE-LTF , Δ margin , and N margin The value of Λ and the minimum interference indicator depend on the receiver implementation, channel conditions, targeted throughput, and / or latency constraints.

[0045] N maxE-LTF Note that for N, a rule of thumb for MIMO communications including channel estimation typically suggests that 50% of the coherence time should be used for training symbols. maxE-LTF must not exceed 70% of the coherence time, and N maxE-LTFSetting is 50% of the coherence time gives good results.

[0046] Δ margin Note that this parameter controls how often the number of E-LTFs is changed in the absence of notification. In highly dynamic environments such as shopping malls or airports, it may be desirable to lower this value so that the number of E-LTFs is adapted at a faster pace. Conversely, in more static environments such as private apartment buildings, it may be desirable to lower Δ margin It may be desirable to set Δ to a large value. As for the exact value, if the interference indicator is based on SINR or power level, then Δ margin Small values ​​of are around 3 dB (meaning a factor of 2), while larger values ​​are between 10 and 20 dB (i.e., a factor of 10 to 100). Values ​​below 1 dB are not feasible (because they would change too frequently), and above 30 dB the E-LTF barely changes. However, if the indicator is generated based on the number of BSSs or the number of past retransmissions, the margin will be different. For example, if high reliability is desired, the number of E-LTFs should be changed after one retransmission or when there is another BSS nearby. Typical ranges are given relative to the interference indicator. For example, the margin value can range from 0.5 to 100 times the average interference indicator value.

[0047] Δ margin Note that for , this number must be a positive integer, since only an integer number of symbols can be added. The value ranges from 1 to N maxE-LTF -1, and the number of E-LTFs can be changed one at a time or in large increments. Preliminary results show that doubling the number of E-LTFs can result in significant gains. Thus, typical operation is N marginThe solution is to set ≡ equal to a factor of the number of previous E-LTFs (e.g., 0.5 to 2 times). Alternatively, since the maximum number of spatial streams allowed in IEEE 802.11 ax is 8, it can be set to 1 to 16 for typical operation.

[0048] 5 is a diagram illustrating a first communication device 10 (also referred to herein as an intended transmitter, e.g., representing a station STA) according to one embodiment of the present disclosure for communicating with a second communication device 20 (also referred to herein as a receiver, e.g., representing an access point AP). The first communication device 10 can exchange (receive and / or transmit) data with the second communication device 20, which may optionally exchange data with another communication device (e.g., another station not shown in FIG. 5). This communication, and in particular one or more channels used for this communication, may be disrupted by interference, for example, interference by a third communication device 30 (also referred to herein as an unintended transmitter or an interfering transmitter, e.g., representing another station).

[0049] The communication devices 10, 20, and 30 each include circuits 11, 21, and 31 configured to perform certain operations. These circuits may be implemented by respective processors or computers, i.e., as hardware and / or software, or by dedicated units or components. For example, respective programmed processors may represent the respective circuits 11, 21, and 31.

[0050] FIG. 6 is a flowchart of a first communication method 200 of the first communication device 10 according to an embodiment of the present disclosure. The first communication method 200 may be performed by the circuit 11. In a first step 201, a second number of mutually orthogonal sequences are generated. In a second step 202, one or more third number of spatial streams, each carrying payload data, are generated. In a third step 203, each of the first number of training symbols is divided into a fourth number of tone sets, with each training symbol spanning multiple tones. In a fourth step 204, each orthogonal sequence is divided into a fourth number of portions. In a fifth step 205, a training field is generated by mapping elements of corresponding portions of the orthogonal sequences to the tone sets of the training symbols. In a sixth step 206, the training field is placed before and / or between payload data of the spatial streams to enable channel estimation by the second communication device.

[0051] 7 is a flowchart of a second communication method 300 of the second communication device 20 according to an embodiment of the present disclosure. The second communication method 300 may be performed by the circuit 21. In a first step 301, one or more initial channel observations of one or more channels between the first communication device and the second communication device are obtained based on at least a portion of a training field. Accordingly, the training field is placed before and / or between payload data of one or more third spatial streams received from the first communication device, each spatial stream carrying payload data. Each of the first number of training symbols is divided into a fourth number of tone sets spanning multiple tones. Each of the second number of mutually orthogonal sequences is divided into the fourth number of portions. Elements of corresponding portions of the orthogonal sequences are mapped to the tone sets of the training symbols to generate a training field. In a second step 302, interference channel estimation of one or more potential interference channels is performed based on other portions of the training field. In a third step 303, interference suppression is performed based on interference channel estimation information obtained from interference channel estimation.

[0052] For 2xE-LTF and 4xE-LTF signals, the duration of the E-LTF symbol is twice and four times longer than for 1xE-LTF, resulting in two and four times the number of non-empty tones, respectively. This means that the frequency space between non-empty tones is divided by two and four, respectively. The wireless channel varies with frequency depending on the multipath characteristics of the propagation environment. However, the channels experienced on adjacent tones tend to be highly correlated. This means that channel estimation can be performed by combining observations from adjacent tones.

[0053] The number of orthogonal sequences for estimating spatial streams is P E-LTF In standard WLAN operation, P E-LTFThe size of the matrix is ​​equal to the number of E-LTF symbols. In one embodiment, P E-LTF It is proposed to have a matrix whose rows are mapped around non-empty adjacent tones, which allows for more orthogonal sequences (i.e., P E-LTF The matrix rows are generated to provide more observations for channel estimation of the intended STA and the interferer. The sequences are preferably mapped around the non-empty tones, so the number and location of the non-empty tones do not change. The mapping technique is illustrated in Figures 8 and 9. Figure 8 shows a P matrix of size 4x4 with four orthogonal sequences of four elements (one per row). E-LTF The orthogonal sequence is generated by two E-LTF symbols (i.e., N E-LTF =2) and two adjacent non-empty data tones (N wt =2). In this example, the transmission duration corresponds to two E-LTF symbols. Also, the three spatial streams from the intended transmitter are assigned to three orthogonal sequences. Therefore, there is one unused orthogonal sequence that can be used to estimate the interference channel.

[0054]

number

[0055]

number

[0056]

number

[0057] The number of adjacent non-empty data tones to map (N wt), it is important to consider the channel characteristics. A key feature of mapping adjacent tones is that only one channel estimate can be obtained per orthogonal sequence. This means that when mapping several adjacent non-empty tones, the channel estimates are derived from the same observations. Therefore, if the channel varies significantly between tones, the mapping technique may give a poor channel estimate.

[0058] To determine how many adjacent tones the transmitter can map together, it may estimate how correlated the channel between the tones is. This can be done by examining the LTF in the response PPDU message (e.g., Clear to Send (CTS), Ack, MCS Feedback). If no response message is available from a previous transmission, the transmitter can use a default mapping in the first PPDU selected based on initial measurements of interference (e.g., the average received power level and / or the number of active BSSs near the device, and / or the SINR). However, because the channel itself changes rapidly, while the correlation between the tones changes at a slower pace, the transmitter can track this correlation between the tones over a longer period of time.

[0059] Based on a measurement of the channel correlation between tones, the transmitter can determine how many tones it can map. Figure 10 shows an example of the magnitude and phase of the autocorrelation function between tones for a typical WLAN channel model. Figures 10A and 10B show the magnitude and phase of the tone autocorrelation for a random realization of a 20 MHz channel with all 256 tones. Figures 10C and 10D show the magnitude and phase of only the first 16 tones.

[0060]

number

[0061] The exact number of mapped tones can be indicated to the receiver in one of the PHY signaling fields in the PPDU preamble. After each PPDU is transmitted by the transmitter, the receiver can evaluate the effectiveness of the interference suppression method (e.g., SINR level and / or log-likelihood ratio value per decoded symbol) and suggest another number of mapped tones to be used in the next PPDU. An indicator in a signaling field of a response message (e.g., Ack, MCS Feedback) can be assumed to allow the receiver to suggest another number of mapped tones to the transmitter. The selection of the number of mapped tones depends on the receiver implementation and channel conditions. Therefore, the process shown in FIG. 4 for selecting the number of E-LTF symbols can be adapted to select the number of mapped tones as shown in FIG. 11.

[0062] 11 is a flow chart of a method 600 for selecting the number of mapped contiguous non-empty tones. T-margin is the number of mapped tones that are added or subtracted with each data exchange. Before the first PPDU exchange, in a first step 601, the transmitter sets the number of mapped adjacent tones to "2", which is the minimum value for tone mapping that supports longer orthogonal sequences compared to the standard. Then, in step 602, the number of mapped adjacent tones is increased to the maximum value N allowed by the channel. max-Wt It is compared to.

[0063] The number of mapped adjacent tones can then be increased (step 604) or decreased (step 605) based on a notification made by the receiver after evaluating the performance of MIMO interference suppression in previous PPDUs (confirmed in step 603). An indicator in the signaling field of the response message (e.g., Ack, MCS Feedback) can be envisioned to allow the receiver to indicate to the transmitter whether to increase or decrease the number of mapped adjacent tones.

[0064]

number

[0065] P HE-LTF The HE-LTF sequence and the orthogonal sequence in the matrix are designed separately. HE-LTF The matrix must have orthogonal rows, and its design is done to facilitate separation of channels from different spatial streams. HE-LTF sequences are designed to reduce PAPR, and in standard implementations, the same orthogonal sequences (i.e., P HE-LTF matrix rows) are replicated for all non-empty tones and then multiplied by the HE-LTF sequence (e.g., as shown in Figure 3, all HE-LTF symbols on the k-th tone are multiplied by the same HE-LTF sequence). k This ensures that the variation in tone values ​​is determined solely by the HE-LTF sequence and that the PAPR remains within acceptable levels.

[0066] P E-LTF When mapping orthogonal sequences of matrices between adjacent non-empty tones, the E-LTF sequence may be changed, which may result in a change in PAPR performance, for example, the E-LTF sequence of the second E-LTF symbol.

[0067] To avoid modifying the structure of the E-LTF sequence or to mitigate this effect on the PAPR, P E-LTF The matrix can be formed in blocks based on the Hadamard method. E-LTF The matrix design creates blocks that are replicated across rows and columns (possibly with negative multiplication), meaning that each block row has N wt This means that the E-LTF sequence remains unchanged even after the mapping is performed, and therefore the PAPR performance remains unchanged if the number of spatial streams is less than the number of E-LTF symbols.

[0068]

number

[0069] Therefore, according to the above embodiment, the following parameters are first selected: E-LTF tone sequence (ELTF), number of E-LTF symbols (N E-LTF ) (“first number”), and the number of spatial streams (N sts ) ("third number"). An orthogonal sequence is a square P consisting of mutually orthogonal rows. E-LTF The orthogonal sequence is obtained as rows of a matrix (i.e., a matrix with equal numbers of rows and columns). The orthogonal sequence is divided into several ("fourth number") parts and mapped to different frequency tones of different tone sets. The number of parts is N times the number of mapped tones. wt (the "fourth number"), the number of elements in each part is N E-LTF The total number of elements in each orthogonal sequence (the "second number") is N col-PE-LTF =N wt N E-LTF Each spatial stream is assigned an orthogonal sequence. There are more orthogonal sequences than spatial streams. That is, N sts +1≦N col-PE-LTF is.

[0070] In an exemplary implementation of the disclosed mapping method, N wt A set of tones is defined for each part of the orthogonal sequence. E-LTF The corresponding sets of tones of the E-LTF symbols are multiplied.

[0071] In one example, N sts =2, N E-LTF =2, N wt =2, N col-PE-LTF =N wt N E-LTF = 4. N defined as even and odd tones wt There are 2 sets of tones. The odd-numbered tones are, for example, PE-LTF The first two columns of the matrix, which are the even-numbered tones, are, for example, P E-LTF It may be the last two columns of the matrix. For odd tones (indexed by k), Equation 14 below holds:

[0072]

number

[0073] For even tones (indexed by k+1), Equation 15 below holds:

[0074]

number

[0075] In other examples, N sts =2, N E-LTF =1, N wt =4, N col-PE-LTF =N wt N E-LTF = 4. N defined by modulo arithmetic wt =There are 4 sets of tones.

[0076]

number

[0077] The part of tone set 1 is, for example, P shown in FIG. E-LTF It may be the first column of the matrix, and the part of tone set 1 may be, for example, P E-LTF It may be the first column of the matrix. For k in tone set 1, Equation 17 below holds:

[0078]

number

[0079] For k in tone set 2, Equation 18 below holds:

[0080]

number

[0081] For k in tone set 3, Equation 19 below holds:

[0082]

number

[0083] For k in tone set 4, Equation 20 below holds:

[0084]

number

[0085] Thus, according to the present disclosure, each spatial stream is identified by a specific orthogonal sequence that is mapped to training symbols. Because there may be multiple spatial streams, after mapping the specific orthogonal sequence with the training symbols, there is a specific set of training symbols, one for each spatial stream. The previously identified set of training symbols is then mapped to the transmit antennas along with the payload data for each spatial stream.

[0086] Different parts of each orthogonal sequence are mapped to different tones, and the complete orthogonal sequence must always be mapped to adjacent tones. For example, if an orthogonal sequence is divided into four parts, any set of four adjacent (non-reserved) tones must have all parts mapped to it.

[0087] Any group of adjacent tones that includes all parts of an orthogonal sequence should experience similar channel realizations. Therefore, to determine the maximum number of parts (also referred to herein as the fifth number), one may check how similar the channels between adjacent tones are, which may be done by measuring the channel correlation between the tones. For example, if the channel correlation is measured and the channel changes very little between four adjacent tones, one may divide the orthogonal sequence into four parts. However, if the channel changes significantly between eight adjacent tones, it may be desirable not to use eight parts.

[0088] The channel correlation between tones gradually changes as the tones become farther apart. Thus, if there is little channel variation between four adjacent tones, as in the example above, the optimal number of mapped tones may be, for example, two, three, or four. Then, perhaps after five or six tones, the correlation begins to decrease, and at eight tones, the channel correlation may be too low. Thus, the maximum number of mapped tones (the "fifth number") may be set to, for example, four, five, or six tones.

[0089] The fifth number represents the maximum number of adjacent tones to which different portions of the orthogonal sequence can be mapped. That is, the fifth number may be the maximum value that the fourth number can take. If the orthogonal sequence is divided into four portions, each tone set will contain all four portions if it does not contain any reserved tones.

[0090] Adjacent tones refer to tones that are adjacent to each other in frequency. An OFDM symbol consists of many tones, each with a frequency value. Tones are often indexed by a series of integers. For example, 256 tones are indexed from -127 to +128 (including 0). Thus, a group of four adjacent tones may refer to the sets [9 10 11 12], [-23 -22 -21 -20], [31 32 33 34], etc.

[0091] 12 shows a flowchart 400 summarizing the main operations performed in a transmitter according to the present disclosure. In a first step 401, E-LTF sequences are defined from several types, for example, three types defined in the IEEE 802.11ax amendment (1xHE-LTF, 2xHE-LTF, and 4xHE-LTF). In a second step 402, the number of E-LTF symbols (N E-LTF , which represent the first number) is defined based on the number of spatial streams and interference conditions. In a third step 403, N E-LTF training symbols (each spanning many tones) are generated. In a fourth step 404, the symbols of each spatial stream are mapped to the transmit antennas via spatial mapping defined by the Q matrix defined in the IEEE 802.11ax standard amendment. In a fifth step 405, OFDM modulation is a standard procedure that involves creating a time-domain signal that combines all the frequency tones of each E-LTF symbol. In a sixth step 406, the digital signals assigned to each antenna are converted to analog signals and ultimately mapped to a waveform that is transmitted via radio frequency (RF) waves.

[0092] Adding more orthogonal sequences as proposed in accordance with the present disclosure also allows for transmitting more spatial streams, e.g., supporting 16 spatial streams for IEEE 802.11be. Furthermore, in the case of overlapping BSSs (OBSS), orthogonal sequences can be assigned such that the BSSs use different sequences to mitigate mutual interference when there is coordination between the BSSs to start PPDUs at the same time.

[0093] In the following, receiver aspects relating to interference channel estimation and suppression are described.

[0094] The PPDU preamble contains some legacy training and signaling fields in addition to the corresponding signaling fields corresponding to the latest standard amendments, which means that before receiving the E-LTF symbols, the receiver must establish synchronization and successfully decode all parameters necessary to decode the E-LTF symbols.

[0095]

number

[0096]

number

[0097]

number

[0098]

number

[0099]

number

[0100]

number

[0101] In another variation, the desired channel is removed by subtracting the channel estimate of the desired transmitter, which results in Equation 27 below.

[0102]

number

[0103]

number

[0104]

number

[0105]

number

[0106] The demapping operation applied by the receiver can work as follows (as an example): Assume eight tones numbered from -3 to 4 (i.e., [-3 -2 -1 0 1 2 3 4]), where the first, last, and middle tones are reserved; i.e., the tones indexed with -3, 0, and 4 are not used. The number of tone sets (the fourth number) is 2, equal to the number of parts of the orthogonal sequence. The mapping done at the transmitter side was such that odd tones are part 1 and even tones have part 2.

[0107] A table for referencing tone indices with portions of the orthogonal sequence is as follows: Tone index: [-3 -2 -1 0 1 2 3 4] Mapped part: [1 2 1 2 1 2 1 2] The mapping of reserved tones is not important because they are not transmitted. Since the number of symbols (first number) is 2, the number of orthogonal sequences (second number) is 4 (the product of the first number and the fourth number), and each sequence also has four elements.

[0108] Demapping at the receiver needs to find which tones and symbols to use to obtain a channel observation for each tone. The details of the demapping to obtain such a channel observation for each tone index are as follows (note that reserved tones are not processed): For a channel observation for tone index -2, extract part 1 from tone -1 in both symbols and part 2 from tone -2 in both symbols. For a channel observation for tone index -1, extract part 1 from tone -1 in both symbols and part 2 from tone -2 in both symbols. For a channel observation for tone index 1, extract part 1 from tone 1 in both symbols and part 2 from tone 2 in both symbols. For a channel observation for tone index 2, extract part 1 from tone 1 in both symbols and part 2 from tone 2 in both symbols. For a channel observation for tone index 3, extract part 1 from tone 3 in both symbols and part 2 from tone 2 in both symbols. The channel observation for each tone consists of four samples (the same size as the elements of the orthogonal sequence) taken from two symbols per tone (demapped using two tones, so the fourth number is 2 in this case).

[0109] The previously demapped per-tone channel observations (four samples in this example) are processed as follows to extract two parts (one for the desired channel estimate and one for the interference channel estimate): The part for the desired channel estimate is extracted by projecting the channel observations on the orthogonal sequences transmitted by each spatial stream; The part for the interference channel estimate is extracted by projecting the channel observations on the orthogonal sequences that were not transmitted (the orthogonal sequences that were left unused); In a variant, the desired channel estimates are used to improve the interference channel estimate by subtracting the desired signal from the channel observations.

[0110] According to the present disclosure, it is assumed that the number of orthogonal sequences (the second number) is greater than the number of spatial streams (the third number), thereby providing unused orthogonal sequences that can be used for interference channel estimation.

[0111] Therefore, according to the present disclosure, the transmit training sequence includes a specific orthogonal sequence. The transmit training sequence is mapped to training symbols, resulting in a training field. Each spatial stream is identified by the specific orthogonal sequence mapped to the training symbols. Because there may be multiple spatial streams, after mapping the specific orthogonal sequence with the training symbols, there is a specific set of training symbols, one for each spatial stream. The previously identified set of training symbols is then mapped to the transmit antennas along with the payload data for each spatial stream.

[0112] The present disclosure may achieve one or more of the following advantages: Adding more channel observations of interference allows the receiver to estimate the interfering channel and perform MIMO interference suppression, thereby improving communication robustness, avoiding retransmissions, and reducing latency. Adding more orthogonal sequences also allows channel sounding of more spatial streams with the same time overhead, and can reduce inter-BSS interference by coordinating orthogonal sequence allocation between BSSs.

[0113] As such, the foregoing description discloses and describes exemplary embodiments of the present disclosure. As will be understood by those skilled in the art, the present disclosure may be embodied in other specific forms without departing from its spirit or essential characteristics. Accordingly, the present disclosure is intended to be illustrative and not limiting of the scope of the present disclosure and other claims. The present disclosure defines in part the scope of the following claim terms so as not to provide the public with the subject matter of the invention, including variations readily discernible in the teachings herein.

[0114] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0115] To the extent that embodiments of the present disclosure have been described as being implemented at least in part by a software-controlled data processing apparatus, it will be understood that non-transitory machine-readable media, such as optical disks, magnetic disks, semiconductor memories, and the like, bearing such software are also considered to represent embodiments of the present disclosure. Such software may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0116] The elements of the disclosed devices, apparatus, and systems may be implemented by corresponding hardware and / or software elements, e.g., appropriate circuitry. A circuit is a structural collection of electronic components, such as conventional circuit elements, integrated circuits such as application-specific integrated circuits, standard integrated circuits, application-specific standard products, field-programmable gate arrays, etc. A circuit also includes a central processing unit, a graphics processing unit, and a microprocessor programmed or configured according to software code. A circuit includes the above hardware that executes software, but does not include pure software. A circuit may be implemented by a single device or unit, multiple devices or units, chipset(s), or processor(s).

[0117] Below is a list of further embodiments of the disclosed subject matter. 1. A first communication device configured to transmit data to a second communication device, generating a mutually orthogonal sequence of second numbers; generating one or more third number of spatial streams, each of which carries payload data; dividing each of the first number of training symbols, each spanning multiple tones, into a fourth number of tone sets; Dividing each orthogonal sequence into a fourth number of parts; generating a training field by mapping elements of corresponding portions of the orthogonal sequence to the tone set of the training symbol; The training field is positioned before and / or between the payload data of the spatial stream to enable channel estimation by the second communication device. The circuit is configured as follows: A first communication device. 2. A first communications device as defined in any of the above embodiments, The product of the first number and the fourth number is equal to or greater than the third number. A first communication device. 3. A first communications device as defined in any of the above embodiments, The number of elements in each orthogonal sequence is equal to the product of the first number and the fourth number. A first communication device. 4. A first communications device as defined in any of the above embodiments, The circuitry is configured to map a first portion of each orthogonal sequence to a first set of tones of the training symbol and to map a second portion of each orthogonal sequence to a second set of tones of the training symbol. A first communication device. 5. A first communications device as defined in any of the above embodiments, The circuitry is configured to map a first portion of each orthogonal sequence to a first tone set including odd-numbered tones of the training symbol and to map a second portion of each orthogonal sequence to a second tone set including even-numbered tones of the training symbol. A first communication device. 6. A first communications device as defined in any of the above embodiments, The circuitry is configured to map elements of a first portion of an orthogonal sequence and elements of a second portion of the same orthogonal sequence to adjacent tones of the training symbol. A first communication device. 7. A first communications device as defined in any of the above embodiments, The circuitry is configured to determine a fifth number of adjacent tones that form a group of adjacent tones onto which portions of the orthogonal sequence can be mapped by measuring channel correlation between the tones. A first communication device. 8. A first communications device as defined in any of the above embodiments, The circuitry is configured to obtain signaling information from the second communication device, the signaling information including information indicating whether to increase or decrease a fifth number of groups of adjacent tones onto which portions of the orthogonal sequence can be mapped, and / or indicating the first number and / or the fourth number. A first communication device. 9. A first communications device as defined in any of the above embodiments, The circuitry is configured to identify spatial streams by a particular orthogonal sequence, and the training field includes a particular set of a third number of training symbols mapped with the particular orthogonal sequence. A first communication device. 10. The first communication device defined in embodiment 9, The circuitry is configured to map the training symbols and corresponding sets of payload data for each spatial stream directly or indirectly to transmit antennas using multiple-input multiple-output (MIMO) techniques. A first communication device. 11. A second communication device configured to receive data from a first communication device, obtaining one or more intended channel observations of one or more channels between the first communication device and the second communication device based at least in part on a training field, the training field being disposed before and / or between payload data of one or more third number of spatial streams received from the first communication device, each spatial stream carrying payload data, each of the first number of training symbols being divided into a fourth number of tone sets spanning a plurality of tones, each of the second number of mutually orthogonal sequences being divided into a fourth number of portions, elements of corresponding portions of the orthogonal sequences being mapped to the tone sets of the training symbols to generate a training field; performing interference channel estimation for the one or more potential interference channels based on other portions of the training field; Interference suppression is performed based on interference channel estimation information obtained from the interference channel estimation. The circuit is configured as follows: A second communication device. 12. The second communication device defined in embodiment 11, The circuitry is configured to demap a first portion of the orthogonal sequence from a first set of tones of the training symbol and a second portion of the orthogonal sequence from a second set of tones of the training symbol to obtain the desired channel observation and optionally an interfering channel observation. A second communication device. 13. The second communication device defined in embodiment 11 or 12, The circuitry is configured to transmit signaling information from the second communication device, the signaling information including information indicating whether to increase or decrease a fifth number of groups of adjacent tones onto which portions of the orthogonal sequence can be mapped, and / or indicating the first number and / or the fourth number. A second communication device. 14. The second communication device defined in any one of embodiments 11 to 13, The circuitry is configured to obtain one or more interference channel observations for one or more potential interference channels based on other portions of the training field. A second communication device. 15. The second communication device defined in any one of embodiments 11 to 14, The circuitry is configured to perform an initial channel estimation for the one or more channels based on the obtained initial channel observations and / or to decode data from the received spatial streams. A second communication device. 16. The second communication device defined in any one of embodiments 11 to 15, The circuitry is configured to use the interference channel estimate to calculate an estimate of an interference channel covariance matrix that describes the spatial direction in which the interference occurs, and to generate a spatial filter to combine signals from the receive antennas such that the spatial direction affected by the interference covariance matrix is ​​suppressed. A second communication device. 17. The second communication device defined in any one of embodiments 11 to 16, The circuitry is configured to extract the first portion of the training field used for intended channel estimation by projecting channel observations on the orthogonal sequences transmitted by each spatial stream, and / or to extract the other portion of the training field used for interference channel estimation by projecting the channel observations on the orthogonal sequences not transmitted. A second communication device. 18. A first communication method for transmitting data to a second communication device, comprising: generating a mutually orthogonal sequence of second numbers; generating one or more third number of spatial streams, each of which carries payload data; dividing each of the first number of training symbols, each spanning multiple tones, into a fourth number of tone sets; Dividing each orthogonal sequence into a fourth number of parts; generating a training field by mapping elements of corresponding portions of the orthogonal sequence to the tone set of the training symbol; The training field is positioned before and / or between the payload data of the spatial stream to enable channel estimation by the second communication device. The first communication method. 19. A second communication method for receiving data from a first communication device, comprising: acquiring one or more intended channel observations of one or more channels between the first communication device and the second communication device, the training field being positioned before and / or between payload data of one or more third number of spatial streams received from the first communication device based at least in part on the training field, each spatial stream carrying payload data; each of the first number of training symbols being divided into a fourth number of tone sets spanning a plurality of tones; each of the second number of mutually orthogonal sequences being divided into a fourth number of portions, elements of corresponding portions of the orthogonal sequences being mapped to the tone sets of the training symbols to generate a training field; performing interference channel estimation for the one or more potential interference channels based on other portions of the training field; Interference suppression is performed based on interference channel estimation information obtained from the interference channel estimation. Second communication method. 20. A non-transitory computer-readable recording medium storing a computer program product which, when executed by a processor, causes the second communication method of claim 18 or 19 to be performed. 21. A computer program comprising program code means for causing a computer to perform the steps of the second communication method according to embodiment 18 or 19 when the computer program is run on the computer.

Claims

1. a first communication device configured to transmit data to a second communication device, generating a mutually orthogonal sequence of second numbers; generating one or more third number of spatial streams, each of which carries payload data; dividing each of the first number of training symbols, each spanning a plurality of tones, into a fourth number of tone sets; Dividing each of the orthogonal sequences into the fourth number of portions; generating a training field by mapping elements of corresponding portions of the orthogonal sequence to the tone set of the training symbols; placing the training field before and / or between the payload data of the spatial streams to enable channel estimation by the second communication device after transmission of data to the second communication device; The present invention provides a circuit configured as follows: The circuitry is configured to map a first portion of each of the orthogonal sequences to a first set of tones of the training symbols and to map a second portion of each of the orthogonal sequences to a second set of tones of the training symbols. A first communication device.

2. 10. The first communication device of claim 1, the product of the first number and the fourth number is equal to or greater than the third number A first communication device.

3. 10. The first communication device of claim 1, The number of elements in each of the orthogonal sequences is equal to the product of the first number and the fourth number. A first communication device.

4. 10. The first communication device of claim 1, The circuitry is configured to map a first portion of each of the orthogonal sequences to a first tone set including odd-numbered tones of the training symbols and to map a second portion of each of the orthogonal sequences to a second tone set including even-numbered tones of the training symbols. A first communication device.

5. 10. The first communication device of claim 1, The circuitry is configured to map elements of a first portion of an orthogonal sequence and elements of a second portion of the same orthogonal sequence to adjacent tones of the training symbol. A first communication device.

6. 10. The first communication device of claim 1, The circuitry is configured to determine a fifth number of adjacent tones that form a group of adjacent tones onto which portions of the orthogonal sequence can be mapped by measuring channel correlation between the tones. A first communication device.

7. 10. The first communication device of claim 1, The circuitry is configured to obtain signaling information from the second communication device, the signaling information including information indicating whether a fifth number, which is a maximum number of adjacent tones onto which portions of the orthogonal sequence can be mapped, should be increased or decreased, and / or indicating the first number and / or the fourth number. A first communication device.

8. 10. The first communication device of claim 1, The circuit is configured to identify spatial streams by specific orthogonal sequences, and the number of specific sets of training symbols mapped with the specific orthogonal sequences included in the training field is the third number. A first communication device.

9. 9. A first communication device according to claim 8, The circuitry is configured to map the training symbols and corresponding sets of payload data for each spatial stream directly or indirectly to transmit antennas using multiple-input multiple-output (MIMO) techniques. A first communication device.

10. a second communication device configured to receive data from the first communication device, obtaining one or more intended channel observations of one or more channels between the first communication device and the second communication device based at least in part on a training field; performing an interference channel estimate for the one or more potential interference channels based on another portion of the training field; Interference suppression is performed based on interference channel estimation information obtained from the interference channel estimation. The present invention provides a circuit configured as follows: In the data received from the first communication device, the training field is disposed before and / or between payload data of one or more third number of spatial streams received from the first communication device; Each spatial stream carries payload data; each of the first number of training symbols is divided into a fourth number of tone sets and spans a plurality of tones; each of the mutually orthogonal sequences of the second number is divided into a fourth number of portions; elements of corresponding portions of the orthogonal sequences are mapped to tone sets of the training symbols to generate a training field; A second communication device.

11. 11. A second communication device according to claim 10, The circuitry is configured to demap a first portion of the orthogonal sequence from a first set of tones of the training symbols and a second portion of the orthogonal sequence from a second set of tones of the training symbols to obtain the desired channel observation and an interference channel observation. A second communication device.

12. 11. A second communication device according to claim 10, The circuitry is configured to transmit signaling information from the second communication device, the signaling information including information indicating whether a fifth number, which is a number of adjacent tones onto which portions of the orthogonal sequence can be mapped, should be increased or decreased, and / or indicating the first number and / or the fourth number. A second communication device.

13. 11. A second communication device according to claim 10, The circuitry is configured to obtain one or more interference channel observations for one or more potential interference channels based on other portions of the training field. A second communication device.

14. 11. A second communication device according to claim 10, The circuitry is configured to perform an intended channel estimate for the one or more channels based on the obtained intended channel observations and / or decode data from the received spatial streams. A second communication device.

15. 11. A second communication device according to claim 10, The circuitry is configured to use the interference channel estimate to calculate an estimate of an interference channel covariance matrix that describes the spatial direction in which interference occurs, and to generate a spatial filter to combine signals from receive antennas such that the spatial direction affected by the interference covariance matrix is ​​suppressed. A second communication device.

16. 11. A second communication device according to claim 10, The circuitry is configured to extract a first portion of the training field used for intended channel estimation by predicting channel observations with orthogonal sequences transmitted by each spatial stream, and / or to extract the other portion of the training field used for interference channel estimation by predicting the channel observations with the orthogonal sequences not transmitted. A second communication device.

17. 1. A first communication method for transmitting data to a second communication device, comprising: generating a mutually orthogonal sequence of second numbers; generating one or more third number of spatial streams, each of which carries payload data; dividing each of the first number of training symbols, each spanning a plurality of tones, into a fourth number of tone sets; Dividing each of the orthogonal sequences into the fourth number of portions; generating a training field by mapping elements of corresponding portions of the orthogonal sequence to the tone set of the training symbols; The training field is positioned before and / or between the payload data of the spatial streams to enable channel estimation by the second communication device after transmission of data to the second communication device. This includes: generating the training field Mapping a first portion of each of the orthogonal sequences to a first set of tones of the training symbols and mapping a second portion of each of the orthogonal sequences to a second set of tones of the training symbols. Including First communication method.

18. A second communication method for receiving data from a first communication device, comprising: obtaining one or more intended channel observations of one or more channels between the first communication device and the second communication device based at least in part on a training field; performing an interference channel estimate for the one or more potential interference channels based on another portion of the training field; Interference suppression is performed based on interference channel estimation information obtained from the interference channel estimation. This includes: In the data received from the first communication device, the training field is disposed before and / or between payload data of one or more third number of spatial streams received from the first communication device; Each spatial stream carries payload data; each of the first number of training symbols is divided into a fourth number of tone sets and spans a plurality of tones; each of the mutually orthogonal sequences of the second number is divided into a fourth number of portions; elements of corresponding portions of the orthogonal sequences are mapped to tone sets of the training symbols to generate a training field; A second communication method.

19. A non-transitory computer-readable recording medium storing a computer program product which, when executed by a processor, causes the first communication method of claim 17 or the second communication method of claim 18 to be performed.

Images