Method for transmitting control and training symbol in multi-user wireless communication system

Abstract

To provide a method and an apparatus for transmitting control and training symbols to improve transmission efficiency in a multi-user wireless communication system.SOLUTION: The method according to one embodiment of the present invention is a method for transmitting control and training symbols in a multi-user wireless communication system. The method comprises the steps of: determining whether a required transmission rate of each data can be satisfied through channel estimation in each of terminals when different data are simultaneously transmitted to each of the terminals; and transmitting a data frame to each of the terminals, the data frame being composed in a manner to be capable of discriminating the control and training symbols in each of the terminals using a combination of time, frequency, and code area when the required transmission rate of each data is not satisfied according to the determined result.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for transmitting control and training symbols to improve transmission efficiency in a multi-user wireless communication system. [Background technology]

[0002] Currently, transmission methods for achieving high transmission speeds in wireless communication systems are being discussed and standardized. In order to achieve such high transmission speeds in wireless LAN systems, a structure with a maximum transmission speed of 600 Mbps, which applies a MIMO system with multiple inputs and outputs, has been standardized in IEEE802.11 TGn. In IEEE802.11 VHT SG, a system with a maximum transmission speed of 1 Gbps at MAC SAP has been discussed, and the IEEE802.11 TGac / TGad Task Group has been formed. In order to achieve such high transmission speeds and maintain frequency efficiency, the AP and STA must support more than four streams supported by TGn, and therefore a large number of antennas are required.

[0003] However, from the STA perspective, it is difficult to support a large number of antennas when considering the complexity and power consumption of the STA. Therefore, multi-user MIMO, in which an AP transmits to multiple STAs simultaneously, is being considered.

[0004] FIG. 1 is a timing diagram for explaining interference between STAs transmitting simultaneously when supporting multi-user MIMO while maintaining a transmission scheme such as TGn.

[0005] As shown in FIG. 1, when different data is transmitted to two or more terminals at the same time, interference may occur in an area such as a reference numeral 101 where the different information transmitted to each terminal is different.

[0006] In addition, the received SINR of each STA differs depending on the channel state and the degree of interference for each STA. However, in the currently considered frame structure, the number of LTFs is determined according to the number of streams, and the MCS of the signal field (SIG) is determined by the minimum transmission rate.

[0007] In IEEE802.11n, there is a mixed PPDU format to provide backward compatibility with 11a / g, and a green field format that only supports IEEE802.11n. Each STA sets the Network Allocation Vector (TXOP) information as the modulation & coding scheme and length information included in the signal field of the frame.

[0008] However, when applying multi-user MIMO, since beamformed frames are received by each STA, there is a problem that some STAs cannot correctly detect the MCS and length information in the signal field, which makes the hidden node problem more serious. Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, the present invention provides an apparatus and method for solving the hidden node problem in a wireless communication system using Multi-user MIMO.

[0010] In addition, the present invention divides the VHT-SIG into a common signal field that can be received by all STAs and a dedicated signal field that contains information about beamformed STAs, and selects appropriate LTF and SIG structures depending on the channel conditions and degree of interference between STAs, thereby providing an apparatus and method for reducing the hidden node problem in Greenfield mode. [Means for solving the problem]

[0011] A method according to one embodiment of the present invention is a method for transmitting control and training symbols in a multi-user wireless communication system, and includes a step of determining whether a required transmission rate of each data is satisfied through channel estimation in each terminal when different data are simultaneously transmitted to each terminal; and a step of constructing a data frame so that the control and training symbols can be distinguished by terminal using a combination of time, frequency, and code domain, and transmitting the data frame to each terminal, if the required transmission rate of each data is not satisfied as a result of the determination.

[0012] A method according to another embodiment of the present invention is a method for transmitting control and training symbols in a multi-user wireless communication system, further comprising: a step of determining whether a required transmission rate of each data is satisfied through channel estimation in each terminal when different data are simultaneously transmitted to each terminal; and a step of constructing a data frame so that the control and training symbols overlap without being divided by terminal and transmitting the data frame to each terminal if the required transmission rate of each data is satisfied as a result of the determination. Effect of the Invention

[0013] The effects of the present invention are as follows.

[0014] First, STAs with poor channel conditions can extend the length of the LTF (repetition), apply a lower MCS to the VHT-SIG-D, or repeat the VHT-SIG-D symbols to improve the detection performance of the VHT-SIG-D.

[0015] Second, STAs with excellent channel conditions can transmit VHT-SIG-D in more than one stream and use a high MCS to reduce the number of symbols occupied by VHT-SIG-D, thereby improving transmission efficiency.

[0016] Third, the LTF can be coordinated between STAs to improve channel estimation performance.

[0017] Fourth, the Green-field format can avoid the hidden node problem caused by beamforming. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a timing diagram for explaining interference between STAs transmitting simultaneously when supporting multi-user MIMO while maintaining a transmission scheme such as TGn. [Diagram 2] 1 is an exemplary diagram of a PPDU format in IEEE802.11a / g / n / VHT mixed mode in Mode a. [Diagram 3] 1 is an exemplary diagram of a PPDU format in IEEE 802.11n / VHT mixed mode in Mode a. [Figure 4] 1 is an illustrative diagram of a Green-field PPDU format according to one embodiment of the present invention. [Diagram 5] PPDU in mixed mode format in mode b for STAs that separate LTF. [Figure 6]1 shows a green-field format PPDU in mode b for a STA that separates LTF. [Figure 7a] 1A to 1C are exemplary diagrams illustrating a method of separating LTFs in the cases of mode b-1, mode b-2, mode b-3, and mode b-4, respectively, according to an embodiment of the present invention. [Figure 7b] 1A to 1C are exemplary diagrams illustrating a method of separating LTFs in the cases of mode b-1, mode b-2, mode b-3, and mode b-4, respectively, according to an embodiment of the present invention. [Figure 7c] 1A to 1C are exemplary diagrams illustrating a method of separating LTFs in the cases of mode b-1, mode b-2, mode b-3, and mode b-4, respectively, according to an embodiment of the present invention. [Figure 7d] 1A to 1C are exemplary diagrams illustrating a method of separating LTFs in the cases of mode b-1, mode b-2, mode b-3, and mode b-4, respectively, according to an embodiment of the present invention. [Figure 8a] 1 is an exemplary diagram of a spreading matrix for explaining an LTF matching process according to the present invention; [Figure 8b] 1 is an exemplary diagram of a spreading matrix for explaining an LTF matching process according to the present invention; [Figure 8c] 1 is an exemplary diagram of a spreading matrix for explaining an LTF matching process according to the present invention; [Figure 8d] 1 is an exemplary diagram of a spreading matrix for explaining an LTF matching process according to the present invention; [Figure 8e] 1 is an exemplary diagram of a spreading matrix for explaining an LTF matching process according to the present invention; [Figure 8f] 1 is an exemplary diagram of a spreading matrix for explaining an LTF matching process according to the present invention; [Figure 8g] 1 is an exemplary diagram of a spreading matrix for explaining an LTF matching process according to the present invention; [Figure 8h] 1 is an exemplary diagram of a spreading matrix for explaining an LTF matching process according to the present invention; [Figure 9] 4 is a flowchart for determining a PPDU format according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention will be described below with reference to the accompanying drawings. In describing the present invention, parts that are obvious to those skilled in the art will be omitted so as not to obscure the gist of the present invention. In addition, it should be noted that each terminology described below is used only for the understanding of the present invention, and each manufacturing company or research group may use different terms even for the same purpose.

[0020] First, a transmission / reception signal of multi-user MIMO can be expressed as the following Equation 1.

[0021]

number

[0022] where y is the received signal, H is the channel, W is the precoding matrix at the transmitting end, p is the training sequence value, and n is noise.

[0023] If a ZF precoding scheme that nulls interference between STAs is used, there is no interference between STAs in an ideal environment. However, when a scheme such as MMSE precoding is applied, interference occurs between STAs.

[0024] Assuming that there is an AP that transmits two streams and two STAs that each receive one stream, the transmission and reception signals of a training sequence in multi-user MIMO are expressed as Equation 2 below.

[0025]

number

[0026] Here, the channel estimation of STA 1 and STA 2 can be expressed as Equation 3 below, respectively.

[0027]

number

[0028] As shown in Equation 3, there is mutual interference between terminals, and such interference causes severe errors depending on the degree of channel correlation. To reduce such errors, there are methods to repeat LTF to increase the length, lower the MCS of SIG, increase the symbol length, and transmit LTF separately (coordination). In addition, when the channel condition is excellent, there is a method to increase MCS to reduce overhead and transmit.

[0029] However, the above-mentioned method of reducing errors increases the overhead of LTF in a frame. Therefore, in order to reduce this overhead, a signal field is required to indicate whether LTF repetition is possible, the MCS of the SIG, and whether LTF is separated. Whether LTF is separated is information that all STAs that separate must know. Therefore, it must be transmitted so that all STAs that are not forming a specific beam can receive it. Therefore, it must be divided into common control signals and dedicated control signals of VHT-SIG.

[0030] In the present invention, a field that transmits a common control signal of VHT-SIG is called VHT-SIG-C, and a field that transmits a dedicated control signal of VHT-SIG is called VHT-SIG-D. Also, a mode for STAs that do not separate LTFs is called mode a, and a mode for STAs that separate LTFs is called mode b.

[0031] The mode in which an AP supports 11a / g / n STAs that are not VHT STAs is called 11a / g / n / VHT mixed mode, the mode that supports IEEE802.11n is called 11n / VHT mixed mode, and the mode that does not support IEEE802.11a / g / n is called green-field mode. Each transmission frame format is called a PPDU format. The transmission method for each mode is explained below.

[0032] First, the transmission method in Mode a will be described.

[0033] FIG. 2 is a diagram illustrating an example of a PPDU format in an IEEE 802.11a / g / n / VHT mixed mode in Mode a, and FIG. 3 is a diagram illustrating an example of a PPDU format in an IEEE 802.11n / VHT mixed mode in Mode a.

[0034] In FIG. 2 and FIG. 3, there is a common phase and a dedicated phase. In both cases, the common phase extends up to the VHT-SIG-C field, and the subsequent phase is set as the dedicated phase.

[0035] First, Figures 2(a) and 3(a) show the case where the VHT-SIG-C field 211, 311 is located after the HT-SIG field, and Figures 2(b) and 3(b) show the case where the VHT-SIG-C field 221, 321 is located after the VHT-STF field.

[0036] Next, in Figures 2(b) and 3(b), when a VHT terminal receives an IEEE802.11n frame format, it cannot know whether the frame is an IEEE802.11n frame or a VHT frame before the terminal detects VHT-SIG-C. Therefore, taking into consideration that a VHT-STF for automatic gain control (AGC) may be placed at the symbol position of VHT-SIG-C, a VHT-STF symbol may be transmitted after the HT-SIG, followed by VHT-SIG-C.

[0037] Next, Figures 2(c) and 3(c) show the case where the VHT-SIG-C fields 231, 331 are positioned after the VHT-LTF field. In Figures 2(c) and 3(c), when automatic gain control (AGC) is performed via the VHT-STF, the VHT-LTF is transmitted after the VHT-STF, and then the VHT-SIG-C fields 231, 331 are transmitted, for the sake of VHT-SIG-C demodulation performance.

[0038] Finally, as shown in (d) of Figure 2, it is possible to transmit a VHT-SIG-C field 241 after the L-SIG without the HT-SIG. In addition, various other PPDU formats are possible.

[0039] In addition, in the cases of (a) to (c) of Figure 2, (a) to (c) of Figure 3, and (d) of Figure 2, VHT-SIG-D fields 212, 222, 232, 242, 312, 322, and 332 may be included in the dedicated section.

[0040] FIG. 4 is an exemplary diagram of a Green-field PPDU format according to an embodiment of the present invention.

[0041] 4(a) and 4(b), the common section and the dedicated section can be distinguished by the fact that the dedicated section starts after the VHT-SIG-C field 411, 421. Therefore, the VHT-SIG-D field 412, 422 required for each dedicated section is located in the dedicated section.

[0042] More specifically, as in the case of (a), information on the VHT-STF2, VHT-LTF1, VHT-SIG-D and VHT-LTF2 fields is transmitted via the VHT-SIG-C field 411 that can be received by all STAs, or as in the case of (b), VHT-LTF1 can be transmitted if no automatic gain control (AGC) is required after the VHT-SIG-C 421.

[0043] FIG. 5 shows a PPDU in a mixed mode format in mode b for a STA that separates LTF, and FIG. 6 shows a PPDU in a green-field format in mode b for a STA that separates LTF.

[0044] 5 and 6, the common section and the dedicated section are divided by the VHT-SIG-C fields 511, 521, 531, 541, 551, 561, 611, 621, 631, and 641. Each dedicated section includes VHT-SIG-D fields 512, 522, 532, 542, 552, 562, 612, 622, 632, and 642. Each of the drawings will be described in more detail below.

[0045] (a), (b), (c), and (d) in FIG. 5 are similar to the three cases in Mode a in FIG. The STA separation can be performed for all K STAs transmitting simultaneously, or for as many as necessary, such as STA a to STA b. FIG. 5(a) shows a case where STA K is separated from STA 2. That is, the VHT-SIG-D fields 522 and 532 can be positioned at any position between the VHT-SIG-C and the data field, and the position can be specified via information in the VHT-SIG-C. In this manner, STAs can be separated in the same manner as in FIG. 5(a) in (b), (c), and (d).

[0046] Next, FIG. 6 will be described. (a) and (b) of FIG. 6 are the same as the three cases in Mode a of FIG. 3. The STA separation can be performed for all K STAs transmitting simultaneously, or for as many as necessary, such as STA a to STA b. (a) of FIG. 6 shows a case where STA K is separated from STA 2. Also, in (b) of FIG. 6, the STAs can be separated in the same manner as in (a) of FIG. 6. In this case, the VHT-SIG-D fields 612, 622, 632, and 642 can be positioned at any position between the VHT-SIG-C and the Data Field, and the position can be specified via information included in the VHT-SIG-C field of the corresponding frame.

[0047] An example of a control message contained in the signal field will be described below.

[0048] The information contained in VHT-SIG1 (common control signal; VHT-SIG-C), which all STAs receive the same information, is as follows:

[0049] VHT-SIG1 (VHT-SIG-C) contains the following information:

[0050] (1) Mode a: STA without LTF separation

[0051] - The following information is required for each STA:

[0052] a) Number of symbols in VHT-LTF1, repetition possible

[0053] b) Number of symbols in VHT-LTF2 (can also be included in VHT-SIG2 (VHT-SIG-D))

[0054] c) MCS of VHT-SIG2 (VHT-SIG-D)

[0055] d) Number of symbols in VHT-SIG2 (VHT-SIG-D), repetition possible

[0056] (2) Mode b: STA that separates LTF

[0057] -STA index for separating LTF

[0058] -How to separate LTF

[0059] - Number of symbols in VHT-LTF1, repetition possible

[0060] - Number of symbols in VHT-LTF2 (can also be included in VHT-SIG2 (VHT-SIG-D))

[0061] - MCS of VHT-SIG2 (VHT-SIG-D)

[0062] -Number of symbols in VHT-SIG2 (VHT-SIG-D), repetition possible

[0063] (3) In the case of Green-field mode, to avoid the problem of hidden nodes due to beamforming, the following information is additionally included for the case of STAs that do not use beamforming:

[0064] -MCS, length information

[0065] -VHT-STF2 availability

[0066] (4) VHT-SIG2 (VHT-SIG-D), in which each STA receives different information, contains the following information:

[0067] -Information for the data area of ​​the STA, such as MCS, bandwidth (BW), length, aggregation, short guard interval (Short GI), etc.

[0068] Among the information contained in VHT-SIG1, the structure of VHT-LTF2 can be included in VHT-SIG2.

[0069] There are several methods for separating LTFs depending on the separation of time, frequency, and code domains.

[0070] -Mode b-1: Time domain separation

[0071] -Mode b-2: Frequency domain separation

[0072] -Mode b-3: Time and code region separation

[0073] -Mode b-4: Code, frequency domain separation

[0074] 7a to 7d are exemplary diagrams illustrating a method of separating LTFs in the cases of mode b-1, mode b-2, mode b-3, and mode b-4, respectively.

[0075] As an example of Fig. 7a to Fig. 7d, four STAs are simultaneously transmitted and each STA receives one stream. Fig. 7a is an example of a configuration in which the STAs are divided and transmitted using different symbols, which are values ​​in the time domain, Fig. 7b is an example of a configuration in which the STAs are divided and transmitted using different subcarriers, which are values ​​in the frequency domain, Fig. 7c is an example of a configuration in which the STAs are divided and transmitted using different codes for each STA on the symbol axis, which are values ​​in the time and code domain, and Fig. 7d is an example of a configuration in which the STAs are divided and transmitted using different codes for each STA on the subcarrier axis, which are values ​​in the frequency and code domain.

[0076] In each of the cases shown in Figures 7a to 7d, when each STA receives n streams, the LTF corresponding to each STA is expanded to N and separated for each STA, which can be easily inferred from the case of one stream. In addition to the combinations of Mode b-1 to Mode b-4, a new LTF separation method can be configured from the combination of these modes, and such a configuration can be easily inferred from the existing modes.

[0077] When the LTF is separated, the transmission signal S can be expressed as Equation 4 below.

[0078]

number

[0079] Here, p is an LTF sequence, and n is a symbol index corresponding to the symbol domain. c is a code for spreading the LTF in the time or frequency or time / code or time / frequency domain, and constitutes a spreading matrix. In such a spreading matrix, an orthogonal matrix, a DFT matrix, a unitary matrix, etc. can be used. m is a spatial time stream index corresponding to the spatial domain, and is equal to the total number of spatial time streams when all STAs that wish to transmit simultaneously in MU-MIMO are separated and transmitted. w is a precoding matrix for transmitting MU-MIMO, and g is a transmitting antenna index.

[0080] In the case of OFDM, it can be expanded to a subcarrier, which is a unit of the frequency domain, and the subcarrier index is omitted in Equation 4.

[0081] For example, assuming that spreading is performed in the time domain as in Mode b-1 and the unit of the time domain is a symbol, only the diagonal elements of the spreading matrix have values, and the off-diagonal elements are 0. This is shown in Figure 8a.

[0082] 8A is an example diagram showing a spreading matrix when mode b-1 is spread in the time domain and the time domain unit is assumed to be a symbol. In FIG. 8A, the horizontal axis is a symbol and the vertical axis is a spatial time stream.

[0083] Also, assuming that the frequency domain is spread as in mode b-2 and the frequency domain unit is a subcarrier, the spreading matrix has values ​​only on the diagonal as in the time domain extension, as shown in Figure 8b.

[0084] 8B is an example diagram showing a spreading matrix when mode b-2 is spread in the frequency domain and the frequency domain unit is a subcarrier. In FIG. 8B, the horizontal axis is a subcarrier and the vertical axis is a spatial time stream.

[0085] Also, assuming spreading in the time and code domains, for example, as in mode b-3, and assuming that the unit of the time domain is a symbol, the spreading matrix can be shown as in FIG. 8c.

[0086] 8c is an example diagram showing a spreading matrix when mode b-3 is spread in the time and code domains and the unit of the time domain is a symbol. In FIG. 8c, the horizontal axis is a symbol and the vertical axis is a spatial time stream.

[0087] Also, assuming that the signal is spread in the frequency and code domains, for example, as in mode b-4, and the frequency unit is a subcarrier, the spreading matrix can be shown as in FIG. 8d.

[0088] 8D is an example diagram showing a spreading matrix when mode b-4 is spread in the frequency and code domain and the frequency unit is a subcarrier. In FIG. 8D, the horizontal axis is a subcarrier and the vertical axis is a spatial time stream.

[0089] The above-described method can be combined to easily expand the spreading matrix to a symbol / subcarrier form in which a symbol and a subcarrier are combined. If it is assumed that the total spatial time stream to be transmitted is assigned to each STA, it can be illustrated as shown in FIG. 8e.

[0090] FIG. 8e shows a case where the total space-time streams to be transmitted are allocated to each terminal.

[0091] To illustrate the example of Figure 8e, STA 1 uses two spatial time streams, STA 2 uses three spatial time streams, and STA K uses one spatial time stream. As shown in Figure 8e, it is not necessary for all STAs to use the same number of spatial time streams.

[0092] For example, if three STAs each use two spatial time streams out of a total of six spatial streams and a discrete Fourier transform (DFT) matrix is ​​used as the spreading matrix, the allocation of spreading matrices for each STA can be shown as shown in Figure 8f.

[0093] As shown in FIG. 8f, the horizontal axis is the spatial time stream, and the vertical axis is the symbol, subcarrier, or symbol / subcarrier. In the spreading matrix of FIG. 8f, the values ​​of the first row and the first column are both 1. Also,

number

[0094] In addition, for example, if four STAs each use two spatial time streams out of a total of eight spatial time streams and a unitary matrix having real values ​​is used as a spreading matrix, the allocation of spreading matrices for each STA can be illustrated as shown in Figure 8g.

[0095] In Fig. 8g, the horizontal axis is the spatial time stream, and the vertical axis is the symbol, subcarrier, or symbol / subcarrier. As shown in Fig. 8g, each element value of the spreading matrix can have any value, and as described above, the spreading matrix can be a discrete Fourier transform matrix (DFT matrix) or a unitary matrix.

[0096] Assuming that the number of spatial time streams to be transmitted simultaneously in MU-MIMO is four and two STAs each transmit two spatial time streams, only four symbols are required in the time domain, so a 4x4 submatrix, which is a part of the 8x8 matrix, can be applied to perform the spreading matrix calculation as shown in Figure 8h.

[0097] FIG. 9 is a flow chart for determining a PPDU format according to a preferred embodiment of the present invention.

[0098] The AP collects channel information of each STA through sounding or feedback information in step 900. Thereafter, the AP applies a precoding algorithm, for example, ZF, MMSE, Sphere encoder, etc., to the STA-specific channels collected in step 902, and then estimates the inter-STA interference.

[0099] After estimating interference in this way, the AP checks whether the STA meets the required performance in step 904. This check is performed to distinguish STAs that do not meet the required performance due to an increase in channel estimation error caused by an increase in interference between STAs. That is, STAs that do not meet the required performance separate LTFs, and STAs that meet the required performance do not separate LTFs.

[0100] If the test result in step 904 is satisfied, i.e., if the VHT-LTF is not separated, the AP operates in Mode a, in which case the AP proceeds to step 906 to determine the MCS of the VHT-SIG-D using the estimated SINR of the STA. If the estimated SINR is high, a higher MCS is applied to the VHT-SIG-D instead of BPSK, and if the estimated SINR is low, the lowest MCS is transmitted.

[0101] On the other hand, if the test result of step 904 is not satisfied, i.e., when separating a VHT-LTF, the AP operates in Mode b. In this case, the AP proceeds to step 908 and can select an appropriate separation mode (coordination mode) using information such as the mobility, delay spread, and signal interference to noise ratio (SINR) of the STA to be separated by the AP.

[0102] For example, if the delay spread is large, the AP applies Mode b-3, and if the delay spread is small, the AP applies Mode b-4. Also, if the SNR is low and the delay spread is large, the AP can reduce the number of simultaneous transmission users and apply Mode b-3 to obtain gains from despreading.

[0103] Thereafter, the AP may proceed to step 910 to determine whether and how many times the VHT-LTF / VHT-SIG may be repeated. That is, when the LTF is separated, the AP may repeat the LTF in order to further improve the channel estimation performance, so the AP determines the number of times for this. In addition, the AP may repeat the VHT-SIG-D to increase the detection probability of the dedicated control signal.

[0104] As described above, when the mode and repetition for transmission are determined in step 906 or step 910, the AP proceeds to step 912 to determine a PPDU format and configures and transmits a PPDU accordingly.

[0105] As shown in FIG. 2, in Mode a, the receiving end in 11a / g / n / VHT mixed mode operates as follows.

[0106] First, FIG. 2(a) will be described.

[0107] 1) The receiving end performs carrier sensing, automatic gain control (AGC), timing sync, and coarse frequency offset estimation through the L-STF.

[0108] 2) Thereafter, the receiving end performs fine frequency offset estimation and channel estimation via the L-LTF.

[0109] 3) The receiving end then demodulates the L-SIG using the channel estimate obtained using the L-LTF.

[0110] 4) Thereafter, the receiving end detects the HT-SIG using a method for detecting the HT-SIG (BPSK phase rotation) and demodulates it using the channel estimation value of the L-LTF.

[0111] 5) After performing the above process, the receiving end detects the VHT-SIG-C using a method for detecting the VHT-SIG-C (BPSK phase rotation) and demodulates it using the channel estimation value of the L-LTF.

[0112] 6) The receiving end also performs automatic gain control (AGC) of the beamformed multi-user MIMO signal using the VHT-STF.

[0113] 7) Thereafter, the receiving end estimates a multi-user MIMO channel via the VHT-LTF using information on the structure of the VHT-LTF in the VHT-SIG-C.

[0114] 8) After that, the receiving end demodulates the VHT-SIG-D based on the information on the VHT-SIG-D indicated by the VHT-SIG-C and the channel estimation value using the VHT-LTF.

[0115] 9) The receiving end then demodulates the data using information on the VHT-SIG-D data.

[0116] Next, Fig. 2(b) will be described. Here, when comparing Fig. 2(b) with Fig. 2(a), steps 1) to 4) are the same, so only the subsequent steps will be described.

[0117] 5) After demodulating the L-SIG, the receiving end performs AGC using the VHT-STF.

[0118] 6) After that, the receiving end detects the VHT-SIG-C using a method for detecting the VHT-SIG-C (BPSK phase rotation) and demodulates it using the channel estimation value of the L-LTF.

[0119] 7) The receiving end then performs AGC on the beamformed multi-user MIMO signal using the VHT-STF.

[0120] 8) Also, the receiving end estimates a multi-user MIMO channel via the VHT-LTF using information on the structure of the VHT-LTF in the VHT-SIG-C.

[0121] 9) After that, the receiving end demodulates the VHT-SIG-D based on the information on the VHT-SIG-D indicated by the VHT-SIG-C and the channel estimation value using the VHT-LTF.

[0122] 10) The receiving end demodulates the data using information on the data of the VHT-SIG-D.

[0123] Next, Fig. 2(c) will be described. Since steps 1) to 4) of Fig. 2(c) are similar to those of Fig. 2(a), they will be omitted.

[0124] 5) After demodulating the L-SIG, the receiving end performs AGC using the VHT-STF.

[0125] 6) After that, the receiving end performs channel estimation using the VHT-LTF.

[0126] 7) The receiving end detects VHT-SIG-C using a method for detecting VHT-SIG-C (BPSK phase rotation) and demodulates it using the channel estimation value of the VHT-LTF.

[0127] 8) The receiving end then performs AGC on the beamformed multi-user MIMO signal using the VHT-STF.

[0128] 9) Thereafter, the receiving end estimates a multi-user MIMO channel via the VHT-LTF using information on the structure of the VHT-LTF in the VHT-SIG-C.

[0129] 10) The receiving end demodulates the VHT-SIG-D based on the information for the VHT-SIG-D indicated by the VHT-SIG-C and the channel estimation value using the VHT-LTF.

[0130] 11) The receiving end then demodulates the data using information about the data in the VHT-SIG-D.

[0131] Next, the case of Fig. 2(d) will be described. Since the steps 1) to 3) of Fig. 2(d) are the same as those of Fig. 2(a), they will be omitted.

[0132] 4) After demodulating the L-SIG, the receiving end detects the VHT-SIG-C using a method for detecting VHT-SIG-C (BPSK phase rotation) and demodulates it using the channel estimation value of the L-LTF.

[0133] 5) Thereafter, the receiving end performs AGC of the beamformed multi-user MIMO signal using the VHT-STF.

[0134] 6) Then, the receiving end estimates a multi-user MIMO channel via the VHT-LTF using information on the structure of the VHT-LTF in the VHT-SIG-C.

[0135] 7) The receiving end demodulates the VHT-SIG-D based on the information for the VHT-SIG-D indicated by the VHT-SIG-C and the channel estimation value using the VHT-LTF.

[0136] 8) The receiving end then demodulates the data using information about the data in the VHT-SIG-D.

[0137] As described above, the receiving methods of 11n / VHT mixed mode / VHT Greenfield mode in Mode a and mixed mode and Greenfield mode in Mode b can be easily configured from the above-mentioned operating structure.

[0138] It is used to transmit training symbols in high speed wireless communication systems.

Claims

1. 1. A method for wireless communication, the method comprising: receiving a legacy short training field; receiving a legacy long training field; receiving a legacy signal field; receiving a first non-legacy signal field; receiving a second non-legacy signal field using first information of the first non-legacy signal field, the first information indicating a modulation and coding scheme of the second non-legacy signal field; receiving a non-legacy long training field; receiving a data field; Equipped with the first non-legacy signal field further includes second information indicating a number of symbols of the non-legacy long training field; 11. The method of claim 10, wherein at least one of the first non-legacy signal field, the second non-legacy signal field, and the non-legacy long training field is used to support multi-user-multiple-input multiple-output (MU-MIMO).

2. The method of claim 1 , wherein the non-legacy long training field is used to estimate a multiple-input multiple-output (MIMO) channel.

3. The method of claim 1 , wherein the first non-legacy signal field further includes third information indicating a number of symbols in the second non-legacy signal field.

4. The method of claim 3 , wherein the second non-legacy signal field includes first information indicating a modulation and coding scheme for the data field.

5. The method of claim 4 , wherein the second non-legacy signal field further includes second information indicating bandwidth information of the data field.

6. The method of claim 1 , wherein the first non-legacy signal field includes common control information that applies to multiple stations.

7. A communication device for a station, the communication device including a circuit, the circuit comprising: causing the station to receive a legacy short training field; causing the station to receive a legacy long training field; causing said station to receive a legacy signal field; causing the station to receive a first non-legacy signal field; having the station receive a second non-legacy signal field using first information of the first non-legacy signal field, the first information indicating a modulation and coding scheme of the second non-legacy signal field; causing the station to receive a non-legacy long training field; configured to cause the station to receive a data field; the first non-legacy signal field further includes second information indicating a number of symbols of the non-legacy long training field; 23. The communications device, wherein at least one of the first non-legacy signal field, the second non-legacy signal field, and the non-legacy long training field is used to support multi-user-multiple-input multiple-output (MU-MIMO).

8. The communications device of claim 7 , wherein the non-legacy long training field is used to estimate a multiple-input multiple-output (MIMO) channel.

9. The communication device of claim 7 , wherein the first non-legacy signal field further includes third information indicating a number of symbols in the second non-legacy signal field.

10. The communications device of claim 9 , wherein the second non-legacy signal field includes first information indicative of a modulation and coding scheme for the data field.

11. The communications device of claim 10 , wherein the second non-legacy signal field further includes second information indicating bandwidth information of the data field.

12. The communications device of claim 7 , wherein the first non-legacy signal field includes common control information that applies to multiple stations.

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