First and second communication devices and communication methods

Abstract

The present invention provides a communication device and communication method that improve detection, channel estimation, and interference suppression in receivers. [Solution] In a communication system, a first communication device that transmits data to a second communication device generates a second number of mutual orthogonal sequences, generates one or more third number of spatial streams, each of which transmits payload data, generates a fourth number of transmit training sequences, each of which includes one or more zeros and / or subsets of the specific orthogonal sequences in addition to a specific orthogonal sequence, generates a training field by mapping the transmit training sequence to a first number of training symbols spanning multiple tones, and places the training field before and / or between the payloads of the spatial streams to enable channel estimation by the second communication device.

Description

[Technical Field]

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

[0002] When multiple transmitters access a channel on the same frequency simultaneously, wireless communication is subject to interference. In distributed access technologies such as WLANs, transmitters compete for channels, potentially leading to collisions. Furthermore, in scenarios with high density of stations (STAs) and access points (APs), the basic service set (BSS) can overlap, potentially causing unwanted interference. Additionally, WLANs operate on unlicensed spectrum, meaning other transmitters from other technologies can use the same radio channel. For these reasons, interference can occur during communication between STAs and APs, or between APs and STAs, leading to communication interruptions. This not only reduces reliability but also decreases throughput and increases latency, as receivers may be unable to decode information and transmitters may need to retransmit messages.

[0003] The “Background” section provided herein is intended to provide a general overview of the context of this disclosure. To the extent described in this Background section, the inventors’ research is not explicitly or implicitly considered prior art to this disclosure, in the same manner as any description that would not be considered prior art at the time of filing. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The objective is to improve detection, channel estimation, and interference suppression in receivers, and to provide corresponding communication devices and communication methods. Furthermore, the objective is to provide corresponding computer programs and non-temporary computer-readable recording media for implementing the above communication methods. [Means for solving the problem]

[0005] In one embodiment, a first communication device is provided, configured to transmit data to a second communication device, comprising: a circuit configured to generate a second number of mutual orthogonal sequences; a third number of spatial streams, each of which transmits payload data; a fourth number of transmit training sequences, each of which includes one or more zeros and / or subsets of the particular orthogonal sequences in addition to a particular orthogonal sequence; a first communication device configured to generate a training field by mapping the transmit training sequences to a first number of training symbols spanning multiple tones; and a first communication device configured to position the training field before and / or between the payloads of the spatial streams to enable channel estimation by the second communication device, wherein the first number of training symbols is equal to the length of the transmit training sequence, the first number of training symbols is set to be greater than the third number of spatial streams, and / or, the second number of orthogonal sequences is set to be greater than the third number of spatial streams, and the fourth number of transmit training sequences is set to be greater than or equal to the third number of spatial streams.

[0006] In another embodiment, a second communication device configured to receive data from a first communication device, each comprising a first number of training symbols spanning multiple tones, and based on at least a portion of a training field positioned before and / or between payloads of one or more third number of spatial streams, each transmitting payload data, received from the first communication device, one or more desired channel observations of one or more channels between the first and second communication devices, and a second number of transmission training sequences mapped to the training symbols of the training field. A second communication device is provided, comprising a circuit configured to include mutual orthogonal sequences, perform interference channel estimation of one or more latent interference channels based on other parts of the training field, and perform interference suppression based on interference channel estimation information obtained from the interference channel estimation, wherein the first number of training symbols is equal to the length of the transmission training sequence, the first number of training symbols is greater than the third number of spatial streams, and / or the second number of orthogonal sequences is greater than the third number of spatial streams, and the fourth number of transmission training sequences is greater than or equal to the third number of spatial streams.

[0007] In yet another embodiment, a computer program is provided which, when executed on a computer, includes programming means for causing a computer to perform each step of the method disclosed herein, and a non-temporary computer-readable recording medium for storing a computer program product that causes the method disclosed herein to be performed when executed by a processor.

[0008] Embodiments are defined in the dependent claims. The disclosed communication methods, disclosed computer programs, and disclosed computer-readable recording media will be understood to have further embodiments similar to and / or identical to those defined in the claims and / or disclosed herein.

[0009] One aspect of this disclosure is enabling a receiver (i.e., a second communication device) to acquire observations of the interfering channel. As a result, this disclosure maintains low signaling overhead and high channel estimation quality for the intended transmitter.

[0010] In this context, the terms “intended transmitter” and “intended STA” refer to a device (also referred to in this disclosure as the “first communication device”) that transmits signals that a receiver (e.g., another station or AP; referred to in this disclosure as the “second communication device”) wants to decode. This means that with respect to data units, e.g., PHY protocol data units (PPDUs; also referred to in this disclosure as “data units” in general) transmitted from the intended transmitter, the receiver can achieve synchronization and decode any signaling fields that may precede the training field. “Interfering transmitter” or “interferer” (also referred to in this disclosure as the “third communication device”) refers to another device (e.g., an STA or AP) that transmits signals that interfere with communication between the intended transmitter and the receiver.

[0011] This disclosure enables interference detection, interference channel estimation, and interference suppression in the receiver by designing a sounding method that increases the number of channel observations in the receiver compared to current standard implementations. Different embodiments for increasing the number of channel observations are disclosed, including adding silent symbols (e.g., by adding zeros to the transmit training symbol or by adding one or more zeros to the transmit training sequence) and adding more training symbols (e.g., by adding duplicated elements to the transmit training symbol or by adding a subset of the transmit training sequence). These modifications enable the receiver to improve decoding performance in the presence of interference, increase reliability, and reduce the number of data retransmissions. A reduction in the number of data retransmissions leads to lower latency and improved throughput.

[0012] The above paragraphs are provided for illustrative purposes only and are not intended to limit the scope of the claims. The embodiments described, along with their further advantages, will be best understood by referring to the following detailed description in conjunction with the accompanying drawings.

[0013] A more complete understanding of this disclosure and many of its associated benefits will be readily apparent, as they are better understood by considering the following detailed description in conjunction with the attached drawings. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 shows the three different HE-LTF types defined in the WLAN 802.11 ax modification. [Figure 2] Figure 2 shows an example of orthogonal sequence mapping using four spatial streams. [Figure 3] Figure 3 is a schematic diagram of a generator for generating the sounding field described in WLAN 802.11ax. [Figure 4]Figure 4 is a flowchart illustrating a method for dynamically adjusting the number of training symbols for each data exchange between communication devices. [Figure 5] Figure 5 shows a communication system including a first communication device and a second communication device according to this disclosure. [Figure 6] Figure 6 is a flowchart of a first communication method for a first communication device according to one embodiment of the present disclosure. [Figure 7] Figure 7 is a flowchart of a second communication method for a second communication device according to one embodiment of the present disclosure. [Figure 8A] Figure 8A shows an embodiment that uses multiple silent periods added to the sounding field. [Figure 8B] Figure 8B shows an embodiment that uses multiple silent periods added to the sounding field. [Figure 8C] Figure 8C shows an embodiment that uses multiple silent periods added to the sounding field. [Figure 8D] Figure 8D shows an embodiment that uses multiple silent periods added to the sounding field. [Figure 8E] Figure 8E shows an embodiment that uses multiple silent periods added to the sounding field. [Figure 9] Figure 9 shows an embodiment that uses duplicate symbols added to the sounding field. [Figure 10] Figure 10 shows a matrix containing duplicated columns. [Figure 11] Figure 11 is a schematic diagram of the generator for generating the sounding field shown in Figure 9. [Figure 12] Figure 12 shows the orthogonal sequence mapping matrix defined in the WLAN 802.11 ax standard. [Figure 13] Figure 13 is a flowchart of a first communication method for a first communication device according to another embodiment of the present disclosure. [Figure 14] Figure 14 is a flowchart of a second communication method for a second communication device according to another embodiment of the present disclosure. [Modes for carrying out the invention]

[0015] According to the WLAN 802.11 standard, the transmitter can adapt the modulation coding scheme (MOS) to the channel state to control the level of redundancy of transmitted information. This ensures robustness against interference at the cost of reduced throughput and increased latency.

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

[0017] A major limitation in WLANs is that only the intended transmitter transmits a sounding signal. There are no established sounding signals or procedures to detect interference from unintended transmitters due to collisions or external sources, or to estimate the interference channel in an ongoing transmission.

[0018] In the latest WLAN 802.11ax modifications, sounding signals are called High Efficiency Long Training Fields (HE-LTFs). These signals are either added within the preamble of the PHY protocol data unit (PPDU) or added between PPDUs as a midamble inserted at a given period to address rapid channel fluctuations.

[0019] Referring to the figures here, similar reference numbers throughout several figures refer to the same or corresponding parts, and Figure 1 shows three different HE-LTF types 1, 2, and 3 as defined in the WLAN 802.11ax amendment. Each HE-LTF corresponds to one OFDM symbol (also referred to herein as the “training symbol” or “HE-LTF symbol”) consisting of many tones across the bandwidth of the channel used. HE-LTF symbols have three types 1, 2, and 3 that differ in duration and the number of tones filled: the first type 1 (referred to as 1xHE-LTF shown in Figure 1A) with a duration of 3.2 μs for each training symbol, the second type 2 (referred to as 2xHE-LTF shown in Figure 1B) with a duration of 6.4 μs for each training symbol, and the third type 3 (referred to as 3xHE-LTF shown in Figure 1C) with a duration of 12.8 μs for each training symbol. The more tones filled, the longer each HE-LTF symbol becomes. The number of HE-LTF symbols is N HE-LTF As shown, N satisfies the following equation 1. sts The selection is based on the total number of spatial streams shown.

[0020]

number

[0021] As shown in Figure 1, each of the training symbols 1, 2, and 3 has 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, a receiver can estimate the MIMO channel between the receiver and the transmitter for each non-empty tone. The channel estimate for an empty tone is implementation-dependent and outside the scope of this disclosure, but is calculated through interpolation techniques commonly known to those skilled in the art. For each non-empty data tone, N HE-LTFThe length N transmitted by the transmitter between individual symbols HE-LTF Based on the orthogonal sequences, the MIMO channel estimation values are calculated at the receiver. These orthogonal sequences are P HE-LTF (also referred to herein as an orthogonal sequence mapping matrix or a HE-LTF mapping matrix) stored in a square matrix (i.e., a matrix with an equal number of rows and columns), and for each spatial stream, N HE-LTF For the case of N = 4, as shown in FIGS. 2 and 3, the rows of this matrix to be transmitted are assigned.

[0023] FIG. 2 is a diagram showing an example of orthogonal sequence mapping by four spatial streams (SS). In this context, the term "orthogonal" means that the matrix multiplication of different rows of P HE-LTF is zero. Therefore, the receiver can obtain the observed values of the channel between each spatial stream transmitted by the receiver and the transmitter without causing interference between the spatial streams.

[0024] [Number]

[0025] More specifically, in this case, the training symbol is called HE-LTF. First, the following parameters are selected: namely, the HE-LTF tone sequence (HELTF), the number of HE-LTF symbols (N HE-LTF ), and the number of spatial streams (N sts ). The orthogonal sequences are obtained as the rows of a square P HE-LTF matrix (i.e., a matrix with an equal number of rows and columns) composed of mutually orthogonal rows. The number of elements in each orthogonal sequence is equal to N HE-LTF . Each orthogonal sequence is assigned to each spatial stream. For each tone (indexed by k and the same procedure for all tones), each orthogonal sequence is multiplied by the corresponding HE-LTF tone sequence in the multiplication module 41. Thereby, for each spatial stream, N HE-LTFN HE-LTF symbols are generated. For example, N sts =2, N HE-LTF If = 2, then equation 3 below holds true.

[0026]

number

[0027] To avoid unintended beamforming effects when transmitting multiple spatial streams, a cyclic time shift is introduced into the signal of each spatial stream in the Cyclic Shift Diversity (CSD) module 42. After the cyclic shift, symbols from all spatial streams are combined with the Q matrix by matrix multiplication in the Combining module 43 to generate symbols transmitted by each transmitting antenna. The Q matrix is ​​generated by the transmitting antenna (N TX )45 The same number of rows and spatial stream (N sts It has the same number of columns as ). Note that a different Q matrix can be selected for each subset of tones, but the mapping procedure remains the same. For each tone, the spatial stream (N sts ) the same number of rows and the number of HE-LTF symbols (N HE-LTF Matrix A having the same number of columns as ) k This shows that training symbols can be represented using this method.

[0028] The transmission symbols of each inverse discrete Fourier transform (IDFT) module 44 and each transmitting antenna 45 are obtained by matrix multiplication QA k It is read from the row of the result. Following the example above, N TX Assuming that Q is the identity matrix and that Q is a direct spatial mapping where each spatial stream is assigned to one antenna, then equation 4 holds.

[0029]

number

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

[0031]

number

[0032]

number

[0033] The maximum number of channels that can be estimated by the receiver is P HE-LTF The number of lines, i.e., the number of HE-LTF symbols in the WLAN 802.11 ax modification, N. HE-LTF This is limited by the number of spatial streams, such as interference channels N. sts To detect and estimate more channels than P HE-LTF This means that the size needs to be increased.

[0034] For MIMO processing to suppress interference signals, the receiver needs to obtain an estimate of the interference channel. This means observing interference without the expected STA present. However, this is not possible in the current implementation of WLAN 802.11 ax because the number of HE-LTF symbols is designed to match the number of spatial streams in most cases. Furthermore, several observations are needed to obtain a good estimate of the interference channel, and the maximum number of unused HE-LTF symbols is 1.

[0035] This disclosure aims to enable interference detection, interference channel estimation, and interference suppression in receivers by designing a novel 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) constructed on a modified HE-LTF signal is envisioned. Several embodiments of such modifications are described below.

[0036]

number

[0037] The number of E-LTF symbols to be transmitted in order to generate an 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 this disclosure, the number of E-LTF symbols is selected to balance time overhead with 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 below.

[0038] First, we start with the minimum number of E-LTF symbols and evaluate the boundary of E-LTF symbols that can be transmitted. As mentioned above, N sts The number of spatial streams shown by and at least the same number of orthogonal sequences (i.e., P shown in Figure 2) HE-LTF P is replaced by E-LTF Use the rows of the matrix. Therefore, the minimum number of E-LTF symbols is N sts ×N sts The smallest number of P E-LTF It supports the use of matrices. Additionally, to obtain interference estimates, the number of spatial streams N is required. sts At least one more channel observation than N must be available to the receiver. Based on these conditions, minE-LTF You can set the minimum number of E-LTF symbols indicated by [this symbol].

[0039] The following considerations apply to the maximum number of E-LTF symbols: Since E-LTF symbols are used for channel estimation, the channel must be nearly static for the duration of the PPDU, known as the coherence time, or until the mid-amble is transmitted. This can be estimated in any device based on statistical measurements of the signal (e.g., during the process of associating the device with the 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 fewer training symbols compared to data symbols in order to reduce time overhead and achieve high throughput and / or low latency. Therefore, N maxE-LTF The maximum number of E-LTFs indicated depends on the specific receiver implementation and channel conditions to limit time overhead and achieve the desired throughput and latency performance.

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

[0042] In the first step 101, before the first PPDU exchange, the transmitter sets the number of E-LTF symbols to a minimum value of NminE-LTF. The number of E-LTF symbols can then be increased or decreased based on notifications made by the receiver after evaluating the MIMO interference suppression performance in past 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, allowing the transmitter to confirm and decide in step 102.

[0043] If no notification is received, the interference indicator, averaged over time, will have a margin Δ to the set minimum value. marginIf the value exceeds the sum of (which is confirmed in step 103), in step 105, the transmitter can increase the number of E-LTFs. This indicator can be generated based on one or more of the following: signal-to-interference noise ratio (SINR), received power level, number of active BSSs, and number of past collisions. If the interference indicator averaged over time exceeds the above value, it means that there are many potential interfering devices, and the receiver will benefit from having more E-LTF symbols for interference suppression. Conversely, if the interference indicator averaged over time exceeds a margin Δ from the set minimum, margin If the value obtained by subtracting (which is confirmed in step 104) is less than the number of potential interferences, then the number of E-LTF symbols is reduced in step 106 to reduce time overhead.

[0044] If none of the above conditions are met, the number of E-LTF symbols remains unchanged until the next transmission. As confirmed in step 102, if there is a notification, 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 may, for example, add an indicator to the signaling field of the PHY preamble to show the receiver the number of E-LTF symbols transmitted in PPUD. maxE-LTF , Δ margin , and N margin The values ​​and minimum interference indicators depend on the receiver implementation, channel conditions, target throughput, and / or latency constraints.

[0045] N maxE-LTF Regarding this, it should be noted that the general rule of thumb for MIMO communication, including channel estimation, suggests that 50% of the coherence time should be used for training symbols. Therefore, N maxE-LTF The coherence time must not exceed 70%, N maxE-LTFSetting this to 50% of the coherence time yields good results.

[0046] Δ margin Regarding this parameter, please note that it controls how often the number of E-LTFs changes in the absence of notification. In highly dynamic environments such as shopping malls and airports, it may be desirable to reduce this value so that the number of E-LTFs adapts at a faster pace. Conversely, in more static environments such as private apartments, it is advisable to reduce Δ to avoid unnecessary changes to E-LTFs. margin It may be desirable to set it to a large value. For the exact value, if the interference indicator is based on SINR or power level, Δ margin Small values ​​are approximately 3 dB (meaning coefficient × 2), while large values ​​range from 10 to 20 dB (i.e., coefficient × 10 to × 100). Values ​​less than 1 dB are unrealistic (due to too frequent changes), and above 30 dB, E-LTF can be said to change very little. However, if the indicator is generated based on the number of BSSs or the number of past retransmissions, the margin will be a different value. 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. A general range is given relative to the interference indicator. For example, the range of margin values ​​is 0.5 to 100 times the average interference indicator value.

[0047] Δ margin Note that this number must be a positive integer, because only an integer number of symbols can be added. The range of values ​​is from 1 to N. maxE-LTF It can be set to -1, and the number of E-LTFs can be changed by one at a time or by a large amount. From preliminary results, it was found that doubling the number of E-LTFs yields a considerable gain. Therefore, the typical operation is N marginThis involves setting it to be equal to the coefficient of the previous E-LTF number (e.g., 0.5 to 2 times). Alternatively, since the maximum number of spatial streams allowed in IEEE 802.11ax is 8, the typical operation can be set from 1 to 16.

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

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

[0050] Figure 6 is a flowchart of a first communication method 200 of a first communication device 10 according to one embodiment of the present disclosure. The first communication method 200 may be performed by a circuit 11. In a first step 201, a second number of mutual orthogonal sequences are generated. In a second step 202, one or more third numbers of spatial streams are generated, each transmitting payload data. In a third step 203, a fourth number of transmit training sequences are generated, each containing one or more zeros and / or subsets of the particular orthogonal sequences in addition to a specific orthogonal sequence from the mutual orthogonal sequences. In a fourth step 204, a training field is generated by mapping the transmit training sequences to a first number of training symbols, each spanning multiple tones. In a fifth step 205, the training field is placed before and / or between the payloads of the spatial streams to enable channel estimation by the second communication device. As a result, the first number of training symbols is set to be equal to the length of the transmission training sequence, the first number of training symbols is set to be greater than the third number of spatial streams, and / or the second number of orthogonal sequences is set to be greater than the third number of spatial streams, and the fourth number of transmission training sequences is set to be greater than or equal to the third number of spatial streams.

[0051] Figure 7 is a flowchart of a second communication method 300 for a second communication device 20 according to one embodiment of the present disclosure. The second communication method 300 may be performed by a circuit 21. In a first step 301, the second communication device 20 obtains one or more desired channel observations for one or more channels between the first and second communication devices based on at least a portion of a training field placed before and / or between payloads of one or more third number of spatial streams, each transmitting payload data, received from the first communication device, each including a first number of training symbols spanning multiple tones, and including a second number of mutually orthogonal sequences in a fourth number of transmit training sequences mapped to the training symbols in the training field. In a second step 302, interference channel estimation is performed for one or more latent interference channels based on the rest of the training field. In a third step 303, interference suppression is performed based on the interference channel estimation information obtained from the interference channel estimation. As a result, the first number of training symbols is equal to the length of the transmission training sequence, the first number of training symbols is greater than the third number of spatial streams, and / or the second number of orthogonal sequences is greater than the third number of spatial streams, and the fourth number of transmission training sequences is set to be greater than or equal to the third number of spatial streams.

[0052] The following describes various embodiments and potential implementations of the disclosed communication devices and communication methods.

[0053]

number

[0054] Figure 8 shows how to add multiple silent periods to the sounding field. These periods are multiples of the E-LTF-OFDM symbol and are preferably shorter than SIFS or PIFS. Therefore, the silent period is TS-LTF The duration of the E-LTF-OFDM symbol is T E-LTF-OFDM As shown, the following equation holds true.

[0055]

number

[0056] In the formula, N st This is the silent period T S-LTF This is the number of E-LTF-OFDM symbols included. The location where silent periods are inserted compared to normal E-LTF symbols is set by a binary sequence represented by Sp, as shown in Figure 8C. The Sp sequence is N E-LTF It has elements (8 elements in this example), and is indicated by "1" if a silent period exists, and "0" if it does not. If there is no silent period, a regular E-LTF symbol exists at the position corresponding to the E-LTF symbol.

[0057] For compatibility reasons, it is advantageous for all silent periods to be at the end of non-silent E-LTF-OFDM symbols. At the same time, the header of a conventional PPDU indicates the number of LTF symbols, which will be the number of non-silent E-LTF-OFDM symbols.

[0058] The total number of silent periods is determined by the number of E-LTF symbols that can be selected in the manner shown in Figure 4. In this case, the minimum number of E-LTF symbols is N minE-LTF =Nsts+1. This allows the receiver to estimate the channels for all spatial streams and have one silent period to estimate the interfering channel. Here, the Sp sequence has only one "1" at any given position.

[0059] The Sp sequence can be initialized with default values ​​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 SINR). After the transmitter transmits each PPDU, the receiver can evaluate the effectiveness of the interference suppression method (e.g., the SINR level and / or the value of the log-likelihood ratio per decoded symbol) and suggest new values ​​for the Sp sequence to be used in the next PPDU. Indicators in the signaling field of response messages (e.g., Ack or MCS feedback) can be assumed to allow the receiver to suggest other Sp sequences to the transmitter.

[0060] Therefore, as described above, in the first embodiment, the length of the silent period (consecutive silent LTFs) shall not be longer than a predetermined value of the inter-frame space (IFS) (here denoted as E-IFS, which is, for example, SIFS, PIFS, or DIFS). The granularity of the silent period is given in LTF symbol time. For conventional reasons, it is preferable to have a silent period at the end of the training field.

[0061] To mitigate the effects of phase noise, in one embodiment, a non-empty LTF symbol may be placed alongside it. LTF is also used to fine-tune automatic gain control (AGC). AGC is a mechanism used to estimate the average received power of the signal at each antenna (more specifically, the radio frequency chain). AGC may also be used to reduce distortion that occurs in the process of converting analog signals to digital signals. Therefore, to properly tune AGC, it is desirable to have a non-silent LTF symbol alongside it.

[0062] The legacy portion of the PHY header may instruct legacy devices to place silent symbols in the data portion of the PPDU. Non-legacy devices recognize silent symbols as part of the training field, which may be indicated in the non-legacy portion of the PHY header.

[0063] In one embodiment, a hierarchical method may be used to determine where to add silent symbols. If the total duration of the silent symbols is less than or equal to E-IFS (condition i), these silent symbols are added to the end of the training field. If condition i) is not met, the largest number of silent LTFs with a total duration less than or equal to E-IFS are placed to the end of the training field. Then, if the total duration of the remaining silent symbols is less than or equal to E-IFS, these silent symbols are placed before the non-empty LTF symbols (condition ii). If condition ii) is not met, i.e., there are more silent symbols to add (i.e., the total duration of all silent symbols is greater than 2 × E-IFS), the non-silent LTFs are divided into the smallest possible groups that allow for good AGC estimation, have low phase noise effects, and can be inserted consecutively with the remaining silent LTF symbols having a total duration less than or equal to E-IFS.

[0064] Therefore, according to this first embodiment, firstly, the following parameters are set: E-LTF tone sequence (ELTF), number of E-LTF symbols (N E-LTF ; hereinafter also referred to as the “first number” in this specification, and the number of spatial streams (N sts In this specification, a third number (also called the "third number") is selected. The orthogonal sequence is a square P consisting of mutually orthogonal rows. E-LTF It is obtained as a row of a matrix (i.e., a matrix with the same number of rows and columns). The number of elements in each orthogonal sequence is N. col-PE-LTF ≤N E-LTS -1 is satisfied. Each spatial stream is assigned an orthogonal sequence, i.e., Nsts ≤ N col-PE-LTF (N col-PE-LTF (hereinafter also referred to as the “second number”). The transmit training sequence consists of an orthogonal sequence and zero elements (corresponding to silent symbols in this first embodiment). Thus, in this case, the number of transmit training sequences (also referred to as the fourth number) is Nsts Therefore, for each tone, N spatial streams are used for each transmission training sequence. E-LTF The E-LTF tone sequence corresponding to each E-LTF symbol is multiplied.

[0065] In one example, Nsts=2, N col-PE-LTF =2, and N E-LTF The equation = 4 holds true. The number of silent symbols is N E-LTF -N col-PE-LTF = 2. The position of the silent symbol is set as Sp=[1 0 0 1].

[0066]

number

[0067] In this example, there are two transmit training sequences (i.e., the fourth number is 2): SS1=>[0 1 -1 0]; SS2=>[0 1 1 0]. For the k-th tone, the product of the transmit training sequence and the training symbol is shown in the row of the table above. Generally, there is a spatial stream (the third number) used for data transmission and zero or more additional extended spatial streams used only for sounding. Therefore, the fourth number of the transmit training sequence is greater than or equal to the third number.

[0068] In another example shown in Figure 8D, four silent LTFs 4a through 4e and six non-silent LTFs 5 are assumed, and two silent LTFs 4 have a duration equal to the E-IFS. Since two LTF symbols correspond to the E-IFS, there cannot be more than two consecutive silent symbols 4. Therefore, the positions of the silent symbols 4 may be selected as follows: a) Take the maximum number of silent symbols (which means two silent symbols, 4d and 4e) from the total number of silent symbols (five silent symbols 4a to 4e) that fit within an interval of E-IFS or less, and place them at the end. b) Take the maximum number of symbols that fit within an interval of E-IFS or less from the remaining silent symbols (the three remaining silent symbols 4a to 4c) (this means the two silent symbols 4a and 4b) and place them at the beginning. c) If there are more silent symbols to insert (in this case, the remaining one silent symbol 4c) and their total duration is less than or equal to E-IFS, divide the non-silent LTF5 into the minimum number of groups (in this case, two) and insert the silent symbol (in this case, one silent symbol 4c) between them. Thus, the corresponding binary sequence Sp will be as shown in Figure 8E.

[0069] According to the second and third embodiments, the number of E-LTF symbols is increased to be greater than the number of spatial streams. This not only enables interference channel estimation and interference suppression at the receiver, but also improves channel estimation at the intended transmitter. According to the second embodiment, one or more E-LTF symbols are duplicated, and a tone shift is performed in the frequency domain where appropriate. According to the third embodiment, P is used to make more orthogonal sequences available than the number of spatial streams. E-LTF The number of rows in the queue is increased.

[0070]

number

[0071] In duplicate symbols of E-LTF symbols, frequency tone shifts may be added to improve interference channel estimation in other tones. For 1xE-LTF, three frequency shifts are possible, as non-empty tones are placed every four tones (as shown in Figure 1A). For 2xE-LTF, only one frequency shift is possible. Not all tones in an OFDM symbol can be used to transmit the sounding sequence, but there are reserved tones for the guard band and DC frequencies. Therefore, frequency tone shifts must take the following conditions into consideration. i) The tone distance between non-empty tones must be the same unless there is a reserved tone area that simply adds a "0" value. Non-empty tones cannot be closer than a predetermined interval (i.e., every 4 tones for 1xE-LTF, every 2 tones for 2xE-LTF). ii) If the tone shift operation fails to maintain non-empty tones and predetermined tone intervals, non-empty tones corresponding to the reserved area are deleted (i.e., set to "0").

[0072] According to this embodiment, since the first number of E-LTF symbols (four in the example shown in Figure 9) corresponds to the number of spatial streams, the receiver can perform channel estimation for each spatial stream. Then, since the replicated E-LTF symbol 7 contains the same information from the original STA but does not contain information from the interferator, the receiver can create an observed value of the interference channel from the difference between the original symbol 6 and the replicated symbol 7. By optionally selecting a tone shift, a level of diversity can be added to distinguish between the interference channel and the original STA channel.

[0073]

number

[0074] The tone shift depends on the receiver implementation and channel conditions. Therefore, for 1xE-LTF, two bits of indicators per additional E-LTF symbol can be assumed in the PHY signaling field of the preamble to determine which tone shift is used by the transmitter. For 2xE-LTF, one bit of indicator per E-LTF symbol can be assumed in the PHY signaling field. 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 propose a choice of new tone shifts to be used in the next PPDU. Thus, indicators in the signaling field of response messages (e.g., Ack, MCS feedback) can be assumed so that the receiver can propose other tone shift options for replicated E-LTF symbols to the transmitter.

[0075] Therefore, according to the second embodiment, in addition to the selection of parameters as described with respect to the first embodiment, the number of duplicate symbols is N rep =N E-LTF -N col-PE-LTF The following conditions are met. A tone shift may be applied to each duplicated symbol. For each tone, each orthogonal sequence is multiplied by the E-LTF tone sequence corresponding to the non-duplicated E-LTF symbol. This results in N per spatial stream. col-PE-LTF This generates 1 non-duplicated E-LTF symbol. A duplicated E-LTF symbol is a copy of the non-duplicated E-LTF symbol per spatial stream, with any additional tone shifts (if any).

[0076] In one example, N sts =2, N col-PE-LTF =2, N E-LTF The equation = 4 holds true. The number of duplicate symbols is N. rep = 2. The tone shift is selected as

[0013] . That is, the duplicated first E-LTF symbol has one tone shift, and the second duplicated symbol has three tone shifts.

[0077]

number

[0078] The transmission training sequences are as follows: SS1=>[1 -1 1 -1], SS2=>[1 1 1 1]. The product of the transmission training sequence and the training symbol is shown in the row of the table above for the k-th tone. An example of tone shift is as follows:

[0079]

number

[0080]

number

[0081] Similar to the first and second embodiments, the third embodiment adds further time overhead to transmission compared to a conventional training field in a WLAN (e.g., 802.11ax). Therefore, this technique is preferably (but not limited to) applied to 1xE-LTF and 2xE-LTF signals, which have shorter durations compared to 4xE-LTF. However, this embodiment is more flexible than the second embodiment in terms of estimating the intended channel because, P E-LTF Since the matrix can be increased for each symbol, P E-LTF This is because it is not necessary to duplicate all the columns of the matrix.

[0082] Because there is a fixed size set by the standard, to change the size of the number of E-LTF symbols, P E-LTF The matrix needs to be redesigned. By a well-known DFT or a simple operation of the Hadamard matrix, P E-LTF A matrix can be designed. Figure 12 shows the P defined in the WLAN 802.11ax standard. HE-LTFThe matrix is shown. In the following two examples, P is obtained based on the same components existing in the standard. E-LTF A method for obtaining the matrix will be described. In particular, examples of generating the P matrix using any number of E-LTF symbols will be described. For example, E-LTF for N E-LTF with values of a = 4 and b = 2, the matrix P used in the WLAN 802.11 ax standard is given. 6x6

[0083] P E-LTF There are many other variations that can be used to design the P matrix. However, once the number of E-LTF symbols is determined, they remain static. The size of the P matrix is given by N from the first and second embodiments and is not the same as the number of E-LTF symbols. Therefore, N can be explicitly transmitted or inferred from additional information such as the number of E-LTFs or the number of zero or replicated elements. Therefore, it is not necessary to transmit the P matrix (although it can be), and it is agreed in advance which matrix to use for each number of E-LTF symbols, and it is indexed by the value of N. col-PE-LTF col-PE-LTF E-LTF E-LTF

[0084] Generalizing P by the Hadamard matrix means the following. For a positive integer i, when N E-LTF = 2 E-LTF i then for i > 3, P E-LTF = P2 i

[0085]

Number

[0086]

Number

[0087] The total number of E-LTF symbols is selected using the method shown in Figure 4. In this case, the minimum number of E-LTF symbols is N minE-LTF =N sts It becomes like +1. This is P E-LTF This means that at least one row of the matrix is ​​unused, allowing for interference channel estimation at the receiver.

[0088] Therefore, according to the second embodiment, in addition to the parameter selection described with respect to the first embodiment, the number of elements in each orthogonal sequence is N col-PE-LTF =N E-LTF It is equal to . There are more orthogonal sequences than spatial streams. That is, N sts +1≦N col-PE-LTF For each tone, each orthogonal sequence is multiplied by the corresponding E-LTF tone sequence. This results in N per spatial stream. col-PE-LTF =N E-LTF The following E-LTF symbols are generated.

[0089] In one example, N sts =2, N col-PE-LTF =N E-LTF Regarding this, the following equation 18 holds true.

[0090]

number

[0091] Figure 13 shows a flowchart 400 summarizing the main operations performed by the transmitter according to this disclosure. In the first step 401, the E-LTF sequence is defined from several types, for example, three types defined in the IEEE 802.11ax amendment (1xHE-LTF, 2xHE-LTF, and 4xHE-LTF). In the second step 402, the number of E-LTF symbols (N E-LTF N (representing the first number) is defined based on the number of spatial streams and interference conditions. In the third step 403, N for each spatial stream to be transmitted. E-LTFIndividual training symbols (each spanning many tones) are generated. In the fourth step 404, the symbols of each spatial stream are mapped to the transmitting antennas via a spatial mapping defined by the Q matrix as defined in the IEEE 802.11ax standard amendment. In the fifth step 405, OFDM modulation is a standard procedure that involves creating a time-domain signal by combining all frequency tones of each E-LTF symbol. In the sixth step 406, the digital signals assigned to each antenna are converted to analog signals and finally mapped to waveforms transmitted over radio frequency (RF) waves.

[0092] As proposed in accordance with this disclosure, it is also possible to transmit more spatial streams by adding more orthogonal sequences, for example, to support 16 spatial streams for IEEE 802.11be. Furthermore, in the case of overlapping BSSs (OBSS), if there is consistency between BSSs to start PPDUs simultaneously, orthogonal sequences can be assigned so that the BSSs use different sequences to mitigate mutual interference.

[0093] The following describes receiver configurations related to interference channel estimation and interference channel suppression.

[0094] The PPDU preamble includes several legacy training and signaling fields, in addition to the corresponding signaling fields that correspond to the latest standard revisions. This means that before receiving the E-LTF symbol, the receiver will have established synchronization and successfully decoded all the parameters necessary to process the E-LTF symbol.

[0095]

number

[0096]

number

[0097]

number

[0098]

number

[0099]

number

[0100]

number

[0101]

number

[0102]

number

[0103]

number

[0104] In another variation, the intended channel is removed by subtracting the channel estimate of the intended transmitter. This operation yields the following:

[0105]

number

[0106]

number

[0107] In another variation, the intended channel is removed by subtracting the channel estimate of the intended transmitter. This operation yields the following:

[0108]

number

[0109]

number

[0110]

number

[0111]

number

[0112] Accordingly, according to this disclosure, the transmit training sequence includes a specific orthogonal sequence. The transmit training sequence is mapped to training symbols, thereby forming a training field. Each spatial stream is identified by a specific orthogonal sequence mapped to a training symbol. Since 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 already identified sets of training symbols are then mapped to the transmit antenna along with the payload data for each spatial stream.

[0113] Number of training symbols (N) E-LTF ), the number of orthogonal sequences (hereinafter, N col This is shown by the number of columns in the P matrix, and the number of spatial streams (N). sts The relationship between N and N is as follows: sts To estimate the number of spatial streams, N col ≥N stsIt needs to be N col To send N orthogonal sequences, E-LTF ≥N col It is necessary that the minimum condition for supporting interference channel estimation in the disclosed method is N E-LTF ≥N sts It is +1, which is N E-LTF >N col =N sts or N E-LTF =N col >N sts This could mean...

[0114] In methods using silent symbols, N E-LTF >N col >N sts There are cases where this holds true. For example, N sts =Two spatial streams are N col =Mapped to 4 orthogonal sequences, N E-LTF Two silent symbols are added so that = 6. Similarly, in the method of adding duplicate training symbols (which may include tone shifts), N E-LTF >N col >N sts There are cases where this holds true. For example, N sts =Two spatial streams are N col =Mapped to 4 orthogonal sequences, N E-LTF Two silent symbols are added so that =6. On the other hand, the method of adding training symbols to support a larger P matrix always uses N E-LTF N col > and N col >N sts They are distinguished in such a way that...

[0115] The receiver can extract two types of information from the training field. The first type of information is intended for the channel estimation of the target transmitter, obtained from orthogonal sequences mapped to each spatial stream, and the second type of information refers to unused orthogonal sequences, zero sequences, or duplicate sequences. Once these two types of information are available, the receiver can i) perform MIMO receive coupling and interference suppression, or ii) use the target channel estimate (first type of information) to remove it from the second type of information to create an interference channel estimate, and then perform MIMO receive coupling and interference suppression.

[0116] This disclosure offers one or more of the following advantages: Adding more channel observations for interference allows the receiver to estimate the interfering channel and perform MIMO interference suppression. This improves communication robustness, avoids retransmissions, and reduces latency. Adding more orthogonal sequences allows for channel sounding of more spatial streams, and interference between OBSSs can be reduced by coordinating orthogonal sequence assignments between BSSs.

[0117] As described above, the above description discloses and illustrates exemplary embodiments of the present disclosure. As those skilled in the art will understand, the present disclosure may be implemented in other specific forms without departing from its spirit or essential features. Therefore, the present disclosure is for illustrative purposes only and does not limit the claims and other claims of the present disclosure. The present disclosure partially defines the scope of the terms of the claims above, including modifications readily recognizable in the teachings herein, so as not to provide the subject matter of the invention to the general public.

[0118] In the claims, the term “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude plural. A single element or other unit may perform the function of several items described in the claims. The mere fact that certain means are described in different dependent claims does not imply that combinations of these means cannot be used advantageously.

[0119] To the extent that embodiments of the disclosure have been described as being implemented by at least partially software-controlled data processing devices, it will be understood that non-transient machine-readable media such as optical discs, magnetic discs, and semiconductor memory that hold such software are also considered to represent embodiments of the disclosure. Furthermore, such software may be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0120] The disclosed elements of devices, apparatus, and systems may be implemented by corresponding hardware and / or software elements, such as appropriate circuits. A circuit is a structural assembly of electronic components, including conventional circuit elements, integrated circuits such as application-specific integrated circuits, standard integrated circuits, application-specific standard products, and field-programmable gate arrays. A circuit also includes central processing units, graphics processing units, and microprocessors programmed or configured according to software code. A circuit includes the aforementioned hardware that runs the software, but does not include pure software. A circuit may be implemented by a single device or unit, multiple devices or units, multiple chipsets, or multiple processors.

[0121] The following 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, Generate a mutually orthogonal sequence of the second number, Each generates one or more third spatial streams through which the payload data is transmitted. Each generates a fourth number of transmission training sequences, each containing one or more zeros and / or subsets of the aforementioned specific orthogonal sequences, in addition to a specific orthogonal sequence from the aforementioned mutual orthogonal sequences. Each generates a training field by mapping the above transmission training sequence to a first number of training symbols that span multiple tones. The above training field is placed before and / or between the payloads of the spatial stream to enable channel estimation by the second communication device. It comprises a circuit configured as follows: The first number of the above training symbols is equal to the length of the above transmission training sequence, The first number of the above training symbols is set to be greater than the third number of the above spatial streams, and / or the second number of the above orthogonal sequences is set to be greater than the third number of the above spatial streams. The fourth number of the above transmission training sequences is set to be greater than or equal to the third number of the above spatial streams. The first communication device. 2. The first communication device as defined in Embodiment 1, The circuit is configured to transmit first signaling information indicating one or more of the following: the first number of training symbols, the second number of orthogonal sequences, the third number of spatial streams, the fourth number of transmit training sequences, the presence, number, and / or position of zero, and / or duplicated elements represented by the subset of the particular orthogonal sequences in the transmit training sequence. The first communication device. 3. A first communication device as defined in any of the embodiments described above, The circuit described above is configured to acquire second signaling information from the second communication device, the second signaling information indicating whether the first number of training symbols and / or the second number of orthogonal sequences should be increased or decreased. The first communication device. 4. The first communication device as defined in Embodiment 3, The above circuit acquires one or more of the following as the second signaling information: the maximum number of training symbols, the interference indicator, the interference margin, and the number of training symbols and / or orthogonal sequences to add or remove. The first communication device. 5. A first communication device as defined in any of the embodiments described above, The above circuit is configured to add one or more zeros between the first, last, and / or non-zero elements of a particular orthogonal sequence in the above transmission training sequence. The first communication device. 6. The first communication device as defined in Embodiment 5, The above circuit is configured to limit the number of consecutively placed zeros in the above transmission training sequence such that the time length of the consecutively placed zeros is shorter than the inter-frame space. The first communication device. 7. A first communication device as defined in any of the embodiments described above, The above circuit is configured to add one or more duplicated elements to the above transmission training sequence, wherein the tone of the training symbol mapped to the duplicated element is frequency-shifted compared to the tone of the corresponding element in the original orthogonal sequence. The first communication device. 8. The first communication device as defined in Embodiment 7, The above circuit is configured to perform tone shifting without altering the periodicity of the reserved tone region and / or the original training symbol. The first communication device. 9. A first communication device as defined in Embodiment 7 or 8, The above circuit is configured to transmit first signaling information indicating whether a tone shift is applied to the duplicated elements of the above transmission training sequence, and which tone shift is applied. The first communication device. 10. A first communication device as defined in any one of Embodiments 7 to 9, The above circuit is configured to acquire second signaling information from the second communication device, and the second signaling information indicates a change in tone shift. The first communication device. 11. A first communication device as defined in any of the embodiments described above, The above circuit is configured to generate the training field by multiplying the transmission training sequence by the training symbol for each element and / or tone. The first communication device. 12. A first communication device as defined in any of the embodiments described above, The above circuit identifies spatial streams by a specific orthogonal sequence, and the training field includes a specific set of a third number of training symbols mapped by the specific orthogonal sequence, and is configured to map the training symbols and corresponding sets of payload data for each spatial stream directly or indirectly to a transmitting antenna using multiple-input multiple-output (MIMO) technology. The first communication device. 13. A second communication device configured to receive data from a first communication device, Based on at least a portion of a training field positioned before and / or between payloads of one or more channels between the first and second communication devices, each containing a first number of training symbols spanning multiple tones, and receiving from the first communication device, one or more desired channel observations of one or more channels between the first and second communication devices are obtained, and a second number of mutually orthogonal sequences are included in a fourth number of transmit training sequences mapped to the training symbols of the training field. Based on the rest of the training field described above, perform interference channel estimation for one or more latent interference channels. Interference suppression is performed based on the interference channel estimation information obtained from the above interference channel estimation. It comprises a circuit configured as follows: The first number of the above training symbols is equal to the length of the above transmission training sequence, The first number of the above training symbols is greater than the third number of the above spatial streams, and / or the second number of the above orthogonal sequences is greater than the third number of the above spatial streams. The fourth number of the above transmission training sequences is set to be greater than or equal to the third number of the above spatial streams. A second communication device. 14. A second communication device as defined in Embodiment 13, The above circuit is configured to obtain the desired channel observations from a portion of the training field by extracting the desired channel observations from the orthogonal sequence mapped to the training symbols, and to improve the interference channel estimation by performing the desired channel estimation of one or more channels based on the obtained desired channel observations. A second communication device. 15. A second communication device as defined in Embodiment 13 or 14, The above circuit is configured to acquire interference channel observations based on the rest of the training field and to perform interference channel estimation of one or more latent interference channels based on the acquired interference channel observations. A second communication device. 16. A second communication device as defined in any one of embodiments 13 to 15, The circuit described above is configured to obtain the interference channel observations from the rest of the training field by extracting the interference channel observations from one or more zero and / or specific orthogonal sequences, as well as from a subset of the specific orthogonal sequences included in the transmit training sequence. A second communication device. 17. A second communication device as defined in any one of embodiments 13 to 16, The circuit is configured to receive first signaling information from the first communication device, the first signaling information indicating one or more of the following: a first number of training symbols, a second number of orthogonal sequences, the presence, number, and / or position of zeros, and / or duplicated elements represented by a subset of a particular orthogonal sequence in the transmission training sequence, and whether and which tone shift is applied to the duplicated elements of the transmission training sequence. A second communication device. 18. A second communication device as defined in any one of embodiments 13 to 17, The above circuit is configured to transmit second signaling information, which indicates whether the first number of training symbols and / or the second number of orthogonal sequences should be increased or decreased. A second communication device. 19. A second communication device as defined in any one of embodiments 13 to 18, The above circuit is configured to continue receiving data without discarding payload data during silent periods. A second communication device. 20. A second communication device as defined in any one of embodiments 13 to 19, The above circuit is configured to decode data from the received spatial stream. A second communication device. 21. A first communication method configured to transmit data to a second communication device, Generate a mutually orthogonal sequence of the second number, Each generates one or more third spatial streams through which the payload data is transmitted. Each generates a fourth number of transmission training sequences, each containing one or more zeros and / or subsets of the aforementioned specific orthogonal sequences, in addition to a specific orthogonal sequence from the aforementioned mutual orthogonal sequences. Each generates a training field by mapping the above transmission training sequence to a first number of training symbols that span multiple tones. The above training field is placed before and / or between the payloads of the spatial stream to enable channel estimation by the second communication device. The first number of the above training symbols is equal to the length of the above transmission training sequence, The first number of the above training symbols is set to be greater than the third number of the above spatial streams, and / or the second number of the above orthogonal sequences is set to be greater than the third number of the above spatial streams. The fourth number of the above transmission training sequences is set to be greater than or equal to the third number of the above spatial streams. The first method of communication. 22. A second communication method configured to receive data from a first communication device, Based on at least a portion of a training field positioned before and / or between payloads of one or more channels between the first and second communication devices, each containing a first number of training symbols spanning multiple tones, and receiving from the first communication device, one or more desired channel observations of one or more channels between the first and second communication devices are obtained, and a second number of mutually orthogonal sequences are included in a fourth number of transmit training sequences mapped to the training symbols of the training field. Based on the rest of the training field described above, perform interference channel estimation for one or more latent interference channels. Based on the interference channel estimation information obtained from the above interference channel estimation, interference suppression is performed. The first number of the above training symbols is equal to the length of the above transmission training sequence, The first number of the above training symbols is greater than the third number of the above spatial streams, and / or the second number of the above orthogonal sequences is greater than the third number of the above spatial streams. The fourth number of the above transmission training sequences is set to be greater than or equal to the third number of the above spatial streams. A second method of communication. 23. A non-temporary computer-readable recording medium for storing a computer program product that, when executed by a processor, causes the second communication method described in Embodiment 21 or 22 to be executed. 24. A computer program that includes program code means for causing the computer to perform the steps of the second communication method described in Embodiment 21 or 22 when the computer program is executed on the computer.

Claims

1. A first communication device configured to transmit data to a second communication device, Generate a mutually orthogonal sequence of the second number, Each generates one or more third spatial streams through which the payload data is transmitted. Each generates a fourth number of transmission training sequences, each containing one or more zeros and / or subsets of the aforementioned mutual orthogonal sequences, in addition to a specific orthogonal sequence from the aforementioned mutual orthogonal sequences. A training field is generated by mapping the transmitted training sequence to a first number of training symbols, each spanning multiple tones. The training field is placed before and / or between the payloads of the spatial stream to enable channel estimation by the second communication device. It comprises a circuit configured as follows: The first number of training symbols is equal to the length of the transmitted training sequence, The first number of training symbols is set to be greater than the third number of spatial streams, and / or the second number of orthogonal sequences is set to be greater than the third number of spatial streams. The fourth number of the transmission training sequences is set to be greater than or equal to the third number of the spatial streams. The first communication device.

2. A first communication device according to claim 1, The circuit is configured to transmit first signaling information indicating one or more of the following: a first number of training symbols, a second number of orthogonal sequences, a third number of spatial streams, a fourth number of transmit training sequences, the presence, number, and / or position of zeros, and / or duplicated elements represented by the subset of the particular orthogonal sequences in the transmit training sequence. The first communication device.

3. A first communication device according to claim 1, The circuit is configured to acquire second signaling information from the second communication device, the second signaling information indicating whether the first number of training symbols and / or the second number of orthogonal sequences should be increased or decreased. The first communication device.

4. The first communication device according to claim 3, The circuit acquires one or more of the following as the second signaling information: the maximum number of training symbols, an interference indicator, an interference margin, and the number of training symbols and / or orthogonal sequences to add or remove. The first communication device.

5. A first communication device according to claim 1, The circuit is configured to add one or more zeros between the first, last, and / or non-zero elements of a particular orthogonal sequence in the transmit training sequence. The first communication device.

6. The first communication device according to claim 5, The circuit is configured to limit the number of consecutively placed zeros in the transmission training sequence such that the time length of the consecutively placed zeros is shorter than the inter-frame space. The first communication device.

7. A first communication device according to claim 1, The circuit is configured to add one or more duplicated elements to the transmit training sequence, wherein the tone of the training symbol mapped to the duplicated element is frequency-shifted compared to the tone of the corresponding element in the original orthogonal sequence. The first communication device.

8. The first communication device according to claim 7, The circuit is configured to perform tone shifting without altering the periodicity of the reserved tone region and / or the original training symbol. The first communication device.

9. The first communication device according to claim 7, The circuit is configured to transmit first signaling information indicating whether a tone shift is applied to the duplicated elements of the transmission training sequence, and which tone shift is applied. The first communication device.

10. The first communication device according to claim 7, The circuit is configured to acquire second signaling information from the second communication device, the second signaling information indicating a change in tone shift. The first communication device.

11. A first communication device according to claim 1, The circuit is configured to generate the training field by multiplying the transmit training sequence by the training symbol for each element and / or tone. The first communication device.

12. A first communication device according to claim 1, The circuit identifies spatial streams by a specific orthogonal sequence, and the training field includes a specific set of a third number of training symbols mapped by the specific orthogonal sequence, and is configured to map the training symbols and corresponding sets of payload data for each spatial stream directly or indirectly to a transmitting antenna using multi-input multiple-output (MIMO) technology. The first communication device.

13. A second communication device configured to receive data from a first communication device, Based on at least a portion of a training field positioned before and / or between payloads of one or more third spatial streams, each transmitting payload data, received from the first communication device, one or more desired channel observations of one or more channels between the first and second communication devices are obtained, and a fourth number of transmit training sequences mapped to the training symbols in the training field include a second number of mutually orthogonal sequences. Based on the other parts of the training field, interference channel estimation is performed for one or more latent interference channels. Interference suppression is performed based on the interference channel estimation information obtained from the aforementioned interference channel estimation. It comprises a circuit configured as follows: The first number of training symbols is equal to the length of the transmitted training sequence, The first number of training symbols is greater than the third number of spatial streams, and / or the second number of orthogonal sequences is greater than the third number of spatial streams. The fourth number of the transmission training sequences is set to be greater than or equal to the third number of the spatial streams. A second communication device.

14. A second communication device according to claim 13, The circuit is configured to obtain the desired channel observations from a portion of the training field by extracting the desired channel observations from the orthogonal sequence mapped to the training symbols, and to improve the interference channel estimation by performing the desired channel estimation of one or more channels based on the obtained desired channel observations, and / or to obtain interference channel observations from another portion of the training field, and to perform interference channel estimation of one or more latent interference channels based on the obtained interference channel observations. A second communication device.

15. A second communication device according to claim 13, The circuit is configured to obtain the interference channel observations from the rest of the training field by extracting the interference channel observations from one or more zero and / or specific orthogonal sequences, as well as from a subset of the specific orthogonal sequences included in the transmit training sequence. A second communication device.

16. A second communication device according to claim 13, The circuit is configured to receive first signaling information from the first communication device, the first signaling information indicating one or more of the following: a first number of training symbols, a second number of orthogonal sequences, the presence, number, and / or position of zeros, and / or duplicated elements represented by a specific subset of orthogonal sequences in the transmitted training sequence, and whether and which tone shift is applied to the duplicated elements of the transmitted training sequence, and / or to transmit second signaling information, the second signaling information indicating whether the first number of training symbols and / or the second number of orthogonal sequences should be increased or decreased. A second communication device.

17. A second communication device according to claim 13, The circuit is configured to continue receiving data without discarding payload data during silent periods, and / or to decode data from the received spatial stream. A second communication device.

18. A first communication method configured to transmit data to a second communication device, Generate a mutually orthogonal sequence of the second number, Each generates one or more third spatial streams through which the payload data is transmitted. Each generates a fourth number of transmission training sequences, each containing one or more zeros and / or subsets of the aforementioned mutual orthogonal sequences, in addition to a specific orthogonal sequence from the aforementioned mutual orthogonal sequences. A training field is generated by mapping the transmitted training sequence to a first number of training symbols, each spanning multiple tones. The training field is placed before and / or between the payloads of the spatial stream to enable channel estimation by the second communication device. The first number of training symbols is equal to the length of the transmitted training sequence, The first number of training symbols is set to be greater than the third number of spatial streams, and / or the second number of orthogonal sequences is set to be greater than the third number of spatial streams. The fourth number of the transmission training sequences is set to be greater than or equal to the third number of the spatial streams. The first method of communication.

19. A second communication method configured to receive data from a first communication device, Based on at least a portion of a training field positioned before and / or between payloads of one or more third spatial streams, each transmitting payload data, received from the first communication device, one or more desired channel observations of one or more channels between the first and second communication devices are obtained, and a fourth number of transmit training sequences mapped to the training symbols in the training field include a second number of mutually orthogonal sequences. Based on the other parts of the training field, interference channel estimation is performed for one or more latent interference channels. Based on the interference channel estimation information obtained from the aforementioned interference channel estimation, interference suppression is performed. The first number of training symbols is equal to the length of the transmitted training sequence, The first number of training symbols is greater than the third number of spatial streams, and / or the second number of orthogonal sequences is greater than the third number of spatial streams. The fourth number of the transmission training sequences is set to be greater than or equal to the third number of the spatial streams. A second method of communication.

20. A non-temporary computer-readable recording medium for storing a computer program product that, when executed by a processor, causes to perform the second communication method according to claim 18 or 19.

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