JP6308562B2 - Wireless communication system and wireless communication method - Google Patents

Description

  The present invention relates to a radio communication system and a radio communication method in which a plurality of base station apparatuses (hereinafter referred to as AP) perform AP-linked transmission diversity communication with a terminal apparatus (hereinafter referred to as STA) using the same channel.

  In recent years, base station apparatuses (APs) based on the IEEE802.11g standard, the IEEE802.11a standard, and the like have become widespread as high-speed wireless access systems using the 2.4 GHz band or the 5 GHz band. In systems based on these standards, an orthogonal frequency division multiplexing (OFDM) modulation method, which is a technology for stabilizing characteristics in a multipath fading environment, is used, and a maximum transmission rate of 54 Mbps is achieved. doing.

  However, the transmission rate described above is a transmission rate on the physical layer, and is not a data throughput effective for the user. Actually, since the transmission efficiency in the MAC (Medium Access Control) layer is about 50 to 70%, the upper limit of the throughput is about 30 Mbps.

  On the other hand, the communication speed of the wired LAN has been increasing due to the spread of FTTH (Fiber to the home). For this reason, it is assumed that further increase in transmission speed will be required in the wireless LAN in the future. Various spatial signal processing techniques such as MIMO and multi-user MIMO have been studied to increase the throughput of the radio section, but communication frequency bands have been expanded as other methods. In IEEE802.11a, a frequency band of 20 MHz is used for each channel. In IEEE802.11n, a frequency band of 40 MHz is used. In addition, IEEE 802.11ac has been studied up to 160 MHz when options are included. In this way, channel band expansion is progressing.

  Furthermore, as a technique for increasing the transmission rate, a plurality of APs cooperate with each other, and a single or a plurality of antennas mounted on each AP is used to change the phase and amplitude of a signal transmitted from each antenna to cooperate with diversity. An AP-linked transmission diversity technique that improves the received signal power to noise power ratio (SNR) on the STA side by performing transmission has been studied (Non-patent Document 1).

Martin TH Sirait, Yuki Matsumura, Katsuhiro Temma, Koichi Ishihara, BA Hirantha Sithira Abeysekera, Tomoaki Kumagai and Fumiyuki Adachi, “AP Cooperative Diversity in Wireless Network Using Interference-Aware Channel Segregation Based Dynamic Channel Assignment,” IEEE 25th Annual International Symposium on Personal , Indoor and Mobile Radio Communications (PIMRC'14), Washington DC, USA, 2-5 Sept. 2014. S. Jagannathan, H. Aghajan, and A. Goldsmith, “The effect of time synchronization errors on the performance of cooperative MISO systems” IEEE GlobeCom, Dec. 2004.

  However, in the AP-linked transmission diversity technique, when one AP that performs transmission diversity is a master AP and the other one or more APs are slave APs, the transmission rate is different when there is a difference in the transmission timing of each AP. It is known to cause deterioration of non-patent document 2 (Non-Patent Document 2). Causes of transmission timing deviation include time deviation of AP itself, clock frequency deviation, propagation path difference, and the like. There are time synchronization methods using GPS and time synchronization methods via a wired network as a general method for correcting transmission timing deviations, but it is an inexpensive device such as a wireless LAN and operates in an autonomous manner. It is difficult to mount the time synchronization technology in a system to be performed. In the AP-linked transmission diversity technique, the characteristics are dramatically improved when high-precision synchronization is performed. However, when the synchronization is shifted, the characteristics may be deteriorated.

  The present invention provides a wireless communication system and a wireless communication method capable of maximizing the effects of AP-linked transmission diversity without obtaining high-precision synchronization between a master AP and a slave AP. Objective.

  A first invention is a wireless communication method in which AP1 (master AP) and at least one AP2 (slave AP) communicate with an STA using AP-linked transmission diversity using the same channel, and AP1 has a first trigger frame. 1 to the AP 2, AP 2 sends the first test frame to the STA after sending the first trigger frame, and AP 2 sends the second test frame after receiving the first trigger frame. Is transmitted to the STA, and the STA detects the arrival time difference t between the first test frame and the second test frame, and transmits the information on the arrival time difference t to the AP 1. Step 5 of selecting an AP cooperative transmission diversity method based on the time difference t and transmitting the selection information to AP2; AP1 Preliminary AP2 has a step 6 which communicates with STA in the AP collaboration transmit diversity method based on the acquired information at a receiving step 5.

  The second invention has AP1 (master AP) connected to the centralized control station and at least one AP2 (slave AP), and AP1 and AP2 communicate with each other by STA and AP cooperative transmission diversity using the same channel. In the wireless communication method, the central control station transmits a sequence start signal to AP1, step 1, the AP1 transmits a first trigger frame to AP2 after receiving the sequence start signal, and AP1 The first test frame is transmitted to the STA after transmitting the first trigger frame, the AP 2 transmits the second test frame to the STA after receiving the first trigger frame, and the STA includes the first The arrival time difference t between the test frame and the second test frame is detected, and information on the arrival time difference t is transmitted to AP1. Step 5, AP 1 transmits information of arrival time difference t to the central control station, and the central control station selects an AP cooperative transmission diversity method based on the arrival time difference t, and selects the selection information as AP 1 and Step 7 for transmitting to AP2, and Step 8 for AP1 and AP2 to communicate with the STA by the method of AP cooperative transmission diversity based on the selection information acquired in Step 7.

  In the wireless communication method according to the first or second invention, the AP 1 has a step 9 for transmitting the second trigger frame to the AP 2 after the selection information is acquired, and the AP 1 and the AP 2 transmit and receive the second trigger frame. Later, there is a step 10 in which data frames having the same contents are transmitted to the STA.

  In step 10, when AP1 and AP2 transmit data frames, processing for adjusting the transmission timing of each other and absorbing the arrival time difference t is performed.

  In the wireless communication method of the first or second invention, in addition to the arrival time difference t, at least one of the frequency offset error between AP1 and AP2, the weight generation accuracy for transmission diversity, and the error rate of the test frame is transmitted in conjunction with AP. This is a criterion for selecting a diversity method.

  A third invention is a wireless communication system in which an AP1 (master AP) and at least one AP2 (slave AP) communicate with an STA using AP-linked transmission diversity using the same channel, and the AP1 includes a first trigger frame Is transmitted to AP2, and after the transmission, the first test frame is transmitted to the STA, the information on the arrival time difference t transmitted from the STA is received, and the AP cooperative transmission diversity method is selected based on the arrival time difference t. The AP2 includes means for transmitting the selection information to the AP2, and the AP2 includes means for transmitting the second test frame to the STA after receiving the first trigger frame and receiving the selection information. Means for detecting an arrival time difference t between the test frame and the second test frame, and transmitting information of the arrival time difference t to AP1; When AP2 communicates with the STA by the method of the AP collaboration transmission diversity based on the selected information.

  The fourth invention has AP1 (master AP) connected to the centralized control station and at least one AP2 (slave AP), and AP1 and AP2 communicate with each other by STA and AP cooperative transmission diversity using the same channel. In the wireless communication system, the central control station transmits a sequence start signal to AP1, receives information on arrival time difference t transmitted from STA via AP1, and performs AP-linked transmission diversity method based on the arrival time difference t. And a means for transmitting the selection information to AP1 and AP2, AP1 transmits a first trigger frame to AP2 after receiving the sequence start signal, and transmits a first test frame to the STA after the transmission. And means for transferring the arrival time difference t information transmitted from the STA to the central control station and receiving the selection information. And means for transmitting a second test frame to the STA after receiving the first trigger frame and receiving selection information, and the STA detects an arrival time difference t between the first test frame and the second test frame. And means for transmitting the information of the arrival time difference t to AP1, and AP1 and AP2 communicate with the STA by the AP cooperative transmission diversity method based on the selection information.

  In the wireless communication system of the third or fourth invention, AP1 includes means for transmitting a second trigger frame to AP2 after AP1 acquires the selection information, and AP1 and AP2 include the second trigger frame. After transmission / reception, a data frame having the same content is transmitted to the STA.

  The present invention acquires the mutual synchronization state between the master AP and the STA and between the slave AP and the STA, determines whether AP-linked transmission diversity is possible and selects a transmission diversity method according to the synchronization state. Therefore, it is possible to improve the transmission characteristics by maximizing the effect of AP-linked transmission diversity.

It is a figure which shows the structural example of the radio | wireless communications system of this invention. It is a figure which shows the process sequence of Example 1 of the radio | wireless communications system of this invention. It is a figure which shows the process sequence of Example 2 of the radio | wireless communications system of this invention. It is a time chart which shows the operation example 1 of the radio | wireless communications system of this invention. It is a time chart which shows the operation example 2 of the radio | wireless communications system of this invention.

FIG. 1 shows a configuration example of a wireless communication system of the present invention.
In FIG. 1, a plurality of STAs 40 and APs 30 exist, and each AP 30 is connected to the centralized control station 10 via the network 20. The centralized control station 10 and the network 20 and the AP 30 will be described on the assumption that they are connected by wire, but they are not necessarily connected by wire, and are connected by other wireless communication means such as cellular. Also good. Also, as an example, a wireless LAN system based on CSMA / CA such as IEEE802.11a / b / g / n / ac is assumed, but it can be easily applied to other wireless communication systems.

  Here, assuming the downlink traffic from the AP to the STA, the APs that perform AP cooperative transmission diversity are the master AP 30M and the slave AP 30S, and the STAs to be received are the STA 40T. The master AP 30M is a main AP when performing AP cooperative transmission diversity, and synchronizes with the slave AP 30S by transmitting a trigger signal shown below. The slave AP is an AP that performs transmission diversity in cooperation with the master AP.

  As a method for determining the master AP 30M, for example, in the communication destination STA 40T, in consideration of the load balance of traffic from the AP having the shortest distance, the AP having the large received signal power RSSI, or the traffic from the centralized control station 10 and the number of assigned terminals The determined AP is used. As a method of determining the slave AP 30S, for example, in the communication destination STA 40T, except for the master AP 30M, the APs with the closest distances or the top N when the received signal power RSSI is arranged in descending order (N is an integer greater than 1) Or an AP determined from the centralized control station 10 in consideration of the traffic load balance and the balance of the number of assigned terminals. In the following description, N = 1 is set for simplicity.

Example 1
FIG. 2 shows a processing procedure of the first embodiment of the wireless communication system of the present invention. In the first embodiment, the master AP 30M determines whether or not to allow AP-linked transmission diversity and selects a transmission diversity method without using the centralized control station 10 illustrated in FIG.

  In FIG. 2, the processing procedure of the first embodiment is divided into an inter-AP synchronization step section A and a data transmission step section B.

  First, the master AP 30M spontaneously transmits a trigger frame to the slave AP 30S (S11). The master AP 30M transmits a test frame to the STA 40T after T1 (> 0) that transmitted the trigger frame (step S12). When the slave AP 30S receives the trigger frame (step S13) and recognizes that it is a trigger frame, the slave AP 30S transmits the test frame to the STA 40T after T2 (> 0) after it is ready to transmit the test frame. (S14). The relationship between T1 and T2 will be described with reference to FIGS. 4 and 5 described later.

  The STA 40T receives each test frame transmitted from the master AP 30M and the slave AP 30S (S15), calculates an arrival time difference t of each test frame, and transmits a frame including information on the arrival time difference t to the master AP 30M (S16). . Here, the test frames transmitted by the master AP 30M and the test frames transmitted by the slave AP 30S do not overlap in frequency spectrum, for example, so that the carrier component has only a positive component and only a negative component with respect to the center frequency. (Reference: FIGS. 6 and 7 of Japanese Patent Laid-Open No. 2014-22834). Regarding the frequency offset between APs, the frequency offset can be compensated by calculating the frequency offset from the trigger frame received by the slave AP 30S from the master AP 30M, and correcting and transmitting the slave AP 30S based on the calculation result.

  The master AP 30M receives a frame including information on the arrival time difference t of each test frame (S16), determines whether or not AP-linked transmission diversity is possible based on the arrival time difference t, and selects a transmission diversity method if possible. The determination / selection result is transmitted to the slave AP 30S (S17), and the slave AP 30S receives it (S18). Note that the transmission diversity method has one of three options, for example, maximum ratio combining diversity, cyclic delay diversity, and no diversity. In addition, any of those that can be used as an AP-linked transmission diversity method can be used, such as equal gain combining transmission diversity, space-time code diversity, transmission diversity using a minimum mean square error weight, and the like.

Here, the criteria for determining whether or not AP-linked transmission diversity is possible and the selection criteria for the transmission diversity method are determined in accordance with the length of the arrival time difference t and the variation in t (a variance value, etc.) when a test frame is transmitted a plurality of times. For example, depending on the length of the arrival time difference t,
| T | ≦ t1: Maximum ratio combining diversity t1 <| t | ≦ t2: Cyclic delay diversity t2 <| t |: No transmission diversity (transmitted only by master AP)

  When there are two or more slave APs, there are a plurality of arrival time differences t. In this case, transmission diversity is performed using only the maximum absolute value as a slave AP.

  The set values of t1 and t2 can be set as t1 = Ts and t2 = 8Ts, for example, when the reception sampling interval of the OFDM signal of the wireless LAN is Ts and the guard interval length is 16Ts. This is because the maximum ratio combining diversity requires the condition of the arrival time difference within the sampling interval, whereas the cyclic delay diversity has an accuracy of about half of the guard interval if the interval from the preceding wave to the maximum delay wave is 8Ts. This is because an improvement in characteristics due to AP-linked transmission diversity can be expected.

  In steps S17 and S18, the master AP 30M and the slave AP 30S acquire, based on the determination / selection result corresponding to the arrival time difference t, whether to perform AP-linked transmission diversity, and if so, which transmission diversity to perform. Can do. The above is the inter-AP synchronization step section A.

Next, the data transmission step section B will be described.
A trigger frame is transmitted from the master AP 30M to the slave AP 30S (S19). The master AP 30M transmits a data frame to the STA 40T after T1 ′ (> 0) that transmitted the trigger frame (step S20). When the slave AP 30S receives the trigger frame (step S21) and recognizes that it is a trigger frame, the slave AP 30S transmits the data frame to the STA 40T after T2 ′ (> 0) after it is ready to transmit the data frame. (S22). The relationship between T1 ′ and T2 ′ will be described with reference to FIGS. 4 and 5 described later.

  The STA 40T receives each data frame transmitted by the AP cooperative transmission diversity from the master AP 30M and the slave AP 30S (S23).

(Example 2)
FIG. 3 shows a processing procedure of the second embodiment of the wireless communication system of the present invention. In the second embodiment, the centralized control station 10 shown in FIG. 1 determines whether or not AP-linked transmission diversity is possible and selects a transmission diversity method. Therefore, unlike the first embodiment, the centralized control station 10 can collectively manage and adjust the AP-linked transmission diversity determination criterion and the transmission diversity method selection criterion. Further, information transmission using radio resources (S17 to S18 in FIG. 2) is not required between the master AP 30M and the slave AP 30S in addition to the transmission / reception of the trigger frame. However, the central control station 10 is basically the same as the first embodiment except for determining whether or not AP-linked transmission diversity is possible and selecting a transmission diversity method.

  In FIG. 3, the processing procedure of the wireless communication system according to the second embodiment is divided into an inter-AP synchronization step section A and a data transmission step section B.

First, the centralized control station 10 transmits to the master AP 30M a sequence start signal for starting a sequence for determining whether or not AP-linked transmission diversity is possible / determined (S31). When the master AP 30M receives the sequence start signal (S32), it transmits a trigger frame to the slave AP 30S (S33).
The master AP 30M transmits a test frame to the STA 40T after T1 (> 0) that transmitted the trigger frame (step S34). When the slave AP 30S receives the trigger frame (step S35) and recognizes that it is a trigger frame, the slave AP 30S transmits the test frame to the STA 40T after T2 (> 0) after it is ready to transmit the test frame. (S36). The relationship between T1 and T2 will be described with reference to FIGS. 4 and 5 described later.

  The STA 40T receives each test frame transmitted from the master AP 30M and the slave AP 30S (S37), calculates an arrival time difference t of each test frame, and transmits a frame including information on the arrival time difference t to the master AP 30M (S37). .

  The master AP 30M receives a frame including information on the arrival time difference t of each test frame, and transmits the frame to the centralized control station 10 (S38). The centralized control station 10 receives a frame including information on the arrival time difference t (S39), determines whether or not AP-linked transmission diversity is possible based on the arrival time difference t, and if so, selects a transmission diversity method and determines the determination. / The selection result is transmitted to the master AP 30M and the slave AP 30S (S40).

  Each of the master AP 30M and the slave AP 30S receives the determination / selection result transmitted from the centralized control station 10 (S41, S42), and whether or not to perform AP-linked transmission diversity, and if so, which transmission diversity to perform. Can be obtained. The above is the inter-AP synchronization step section A.

Next, the data transmission step section B will be described.
A trigger frame is transmitted from the master AP 30M to the slave AP 30S (S43). The master AP 30M transmits a data frame to the STA 40T after T1 ′ (> 0) that transmitted the trigger frame (step S44). When the slave AP 30S receives the trigger frame (step S45) and recognizes that it is a trigger frame, the slave AP 30S transmits the data frame to the STA 40T after T2 ′ (> 0) after it is ready to transmit the data frame. (S46). The relationship between T1 ′ and T2 ′ will be described with reference to FIGS. 4 and 5 described later.

  The STA 40T receives each data frame transmitted by the AP cooperative transmission diversity from the master AP 30M and the slave AP 30S (S47).

  Hereinafter, the relationship between T1, T2, T1 ′, T2 ′ and the arrival time difference t of the test frame in the STA 40T will be described with reference to FIGS. It is common to Example 1 and Example 2.

FIG. 4 shows an operation example 1 of the wireless communication system of the present invention.
In FIG. 4, the master AP 30M transmits a trigger frame to the slave AP 30S and transmits a test frame (M test) to the STA 40T after T1. The slave AP 30S receives and demodulates the trigger frame, and after T2, transmits a test frame (S test) to the STA 40T.

  Here, it is assumed that the propagation delay between the master AP 30M and the slave AP 30S is T4, and the length of the preamble of the trigger frame and the processing delay for demodulating in the slave AP 30S are T3. Therefore, a delay of T3 + T4 has already occurred between the timing at which the master AP 30M transmits the test frame and the timing at which the slave AP 30S transmits the test frame. In this state, if T1 = T2, the arrival time difference t when the STA 40T receives each test frame includes a delay of T3 + T4 in addition to the propagation delays between the master AP 30M and the slave AP 30S and the STA 40T. become.

  In the present invention, whether or not AP-linked transmission diversity is possible is determined and a transmission diversity method is selected according to the arrival time difference t including T3 + T4. Thereafter, the master AP 30M transmits a trigger frame to the slave AP 30S and after T1 ′, while the slave AP 30S receives the trigger frame and T2 ′ after demodulation, and then transmits a data frame to the STA 40T by the selected transmission diversity method. To do. At this time, if T1 = T1 ′ = T2 = T2 ′, the situation is the same as when the test frame is transmitted. Therefore, the arrival time difference t of the data frame in the STA 40T is almost the same, and the selected transmission diversity method is used. Corresponding reception processing is performed.

  Here, when the master AP 30M and the slave AP 30S transmit data frames, for example, the master AP 30M close to the STA 40T adjusts the transmission timing T1 ′ by the arrival time difference t and sets T1 ′ = T1 + t in the state of FIG. It is. In this case, the arrival time difference t of data frames in the STA 40T is almost zero. However, each propagation delay between the propagation delay T4, the processing delay T3, the master AP 30M and the slave AP 30S and the STA 40T varies depending on the clock accuracy of the master AP 30M and the slave AP 30S, and the arrival time difference t of the data frame is always There is no guarantee of zero. Therefore, the AP cooperative transmission diversity determination and the transmission diversity method selection process according to the arrival time difference t of the test frames function effectively.

FIG. 5 shows an operation example 2 of the wireless communication system of the present invention.
The parameters T1, T2, T3, T4, t, T1 ′, and T2 ′ shown in the operation example 2 are based on the same definition as the operation example 1 in FIG.

  Here, when the processing delay T3 in the slave AP 30S is known in advance, the timing at which the master AP 30M and the slave AP 30S transmit the test frame is adjusted as T1 = T2 + T3. Thereby, only the propagation delay T4 is added to the arrival time difference t when the STA 40T receives each test frame, in addition to the propagation delays between the master AP 30M and the slave AP 30S and the STA 40T.

  In this case, since the processing delay T3 of the slave AP 30S is excluded from the arrival time difference t, the arrival time difference t is a smaller value than in the case of the operation example 1. Subsequent processing is the same as in Operation Example 1, but it is possible to increase the estimation accuracy of the arrival time difference t, and accurately determine whether AP-linked transmission diversity is available and select a transmission diversity method according to the arrival time difference t. be able to.

  In addition, when transmitting each test frame in steps S12 and S14 of the first embodiment and steps S34 and S36 of the second embodiment, transmission may be performed using transmission diversity weights. For example, when transmission is performed using a transmission diversity weight of maximum ratio combining diversity, on the receiving side, ideally, only one strong direct wave arrives for the number of cooperative diversity antennas. Therefore, the arrival delay time difference between strong direct waves is calculated, and the estimation accuracy of the arrival time difference t is improved.

  In addition, since the bit error rate (BER) and the packet error rate (PER) can be calculated by transmitting and receiving a known test frame, the calculation result can be returned to the master AP 30M instead of the arrival time difference t. Good. In this case, whether or not AP-linked transmission diversity is possible and selection of a transmission diversity method in step S17 of the first embodiment and step S40 of the second embodiment are determined based on whether the BER or PER satisfies the required BER or the required PER. To do. For example, when the required BER = P, if it is equal to or less than P, the transmission diversity used when transmitting in the test frame is used, and if not, another transmission diversity is not selected or transmission diversity is not performed.

  Further, whether or not AP-linked transmission diversity is possible and selection of a transmission diversity method in step S17 of the first embodiment and step S40 of the second embodiment are performed by the centralized control station 10 or the master AP 30M, but are determined by the STA 40T. You can also In this case, when the arrival time difference t of each test frame is calculated in step S15 of the first embodiment and step S37 of the second embodiment, the determination / selection is performed at the same time, and the master AP 30M includes information on the determination / selection result. Send a frame.

  Further, by repeating the inter-base station synchronization step section A a plurality of times and then shifting to the data transmission step section B, the synchronization accuracy can be improved. In addition, once the inter-base station synchronization step interval A is performed, the data transmission step interval B is repeated, and the overhead is reduced by returning to the inter-base station synchronization step interval A again at a certain time or when the surrounding environment changes. Reduction is possible.

  Further, whether or not AP-linked transmission diversity is determined in step S17 of the first embodiment and step S40 of the second embodiment and the selection of the transmission diversity method are performed based on the arrival time difference t. Since the estimation / compensation accuracy of the frequency offset also has an effect on the characteristics, the determination may be made in an integrated manner by taking them into consideration. For example, in a test frame transmitted by the master AP 30M and a test frame transmitted by the slave AP 30S, transmission is performed after performing transmission diversity and transmission frequency offset compensation, so that an error remains with respect to a known test frame on the reception side. In the STA 40T, the error rate, EVM (Eigen Vector Magnitude), arrival time difference, frequency offset, and the like are measured and transmitted to the master base station 30M and the centralized control station 10 in an integrated manner. Can be judged.

In this case, the determination may be made based on the following criteria. For example, the absolute value | f | of the frequency offset estimated value is as follows.
| F | ≦ f 1: Maximum ratio combining diversity f 1 <| f | ≦ f 2: Cyclic delay diversity f 2 <| f |: No transmission diversity (transmitted only by master AP)

  In addition, the transmission of the trigger frame and the transmission of the frame including the arrival time difference t information are not necessarily transmitted on the communication channel. If the channel for exchanging the control information is available on another channel, the transmission is performed on that channel. Also good.

  The centralized control apparatus 10 in the wireless communication system of the present invention can be realized by a communication interface with an AP, a computer, and a computer program that performs the above processing. This computer program can be stored in a computer-readable storage medium or provided via a network.

10 central control station 20 network 30 base station equipment (AP)
30M Master AP
30S Slave AP
40 Terminal equipment (STA)
40T Terminal device communicating with master AP and slave AP

Claims (8)

A first base station apparatus (hereinafter referred to as AP1) and at least one second base station apparatus (hereinafter referred to as AP2) communicate with a terminal apparatus (hereinafter referred to as STA) using AP-linked transmission diversity using the same channel. In a wireless communication method for performing
Step 1 where the AP1 transmits a first trigger frame to the AP2,
The AP1 transmits a first test frame to the STA after transmitting the first trigger frame; and
The AP 2 transmits a second test frame to the STA after receiving the first trigger frame; and
The STA detects an arrival time difference t between the first test frame and the second test frame, and transmits information on the arrival time difference t to the AP 1; and
Step 5 in which the AP1 selects the AP cooperative transmission diversity method based on the arrival time difference t, and transmits the selection information to the AP2.
The AP 1 and the AP 2 have a step 6 of communicating with the STA by the AP cooperative transmission diversity method based on the selection information acquired in the transmission / reception of the step 5. There is a first base station apparatus (hereinafter referred to as AP1) connected to the centralized control station and at least one second base station apparatus (hereinafter referred to as AP2), and AP1 and AP2 use the same channel and are terminal apparatuses (Hereinafter referred to as STA) and a wireless communication method for communicating with AP-linked transmission diversity,
Step 1 in which the central control station transmits a sequence start signal to the AP1;
Step 2 in which the AP1 transmits a first trigger frame to the AP2 after receiving the sequence start signal;
The AP1 transmits a first test frame to the STA after transmitting the first trigger frame; and
The AP2 transmitting a second test frame to the STA after receiving the first trigger frame; and
The STA detects an arrival time difference t between the first test frame and the second test frame, and transmits information of the arrival time difference t to the AP 1; and
Step 6 in which the AP1 transmits information on the arrival time difference t to the central control station;
Step 7 in which the central control station selects the AP cooperative transmission diversity method based on the arrival time difference t, and transmits the selection information to the AP1 and the AP2.
The wireless communication method according to claim 8, wherein the AP1 and the AP2 communicate with the STA by the AP cooperative transmission diversity method based on the selection information acquired in the step 7. The wireless communication method according to claim 1 or 2,
After the AP1 acquires the selection information, the AP1 has a step 9 for transmitting a second trigger frame to the AP2,
The wireless communication method according to claim 10, further comprising a step 10 in which the AP1 and the AP2 each transmit a data frame having the same content to the STA after transmitting and receiving the second trigger frame. The wireless communication method according to claim 3,
The step 10 performs a process of adjusting the transmission timing of each other and absorbing the arrival time difference t when the AP1 and the AP2 transmit the data frame. The wireless communication method according to claim 1 or 2,
In addition to the arrival time difference t, at least one of the frequency offset error between the AP1 and the AP2, the transmission diversity weight generation accuracy, and the error rate of the test frame is used as a criterion for selecting the AP-linked transmission diversity method. A wireless communication method characterized by the above. A first base station apparatus (hereinafter referred to as AP1) and at least one second base station apparatus (hereinafter referred to as AP2) communicate with a terminal apparatus (hereinafter referred to as STA) using AP-linked transmission diversity using the same channel. In a wireless communication system that performs
The AP1 transmits a first trigger frame to the AP2, transmits a first test frame to the STA after the transmission, receives information on an arrival time difference t transmitted from the STA, and receives the arrival time difference t. A method for selecting the AP cooperative transmission diversity method based on the information and transmitting the selection information to the AP 2;
The AP2 includes means for transmitting a second test frame to the STA after receiving the first trigger frame and receiving the selection information,
The STA includes means for detecting an arrival time difference t between the first test frame and the second test frame, and transmitting information on the arrival time difference t to the AP1.
The wireless communication system, wherein the AP1 and the AP2 communicate with the STA by the AP cooperative transmission diversity method based on the selection information. There is a first base station apparatus (hereinafter referred to as AP1) connected to the centralized control station and at least one second base station apparatus (hereinafter referred to as AP2), and AP1 and AP2 use the same channel and are terminal apparatuses (Hereinafter referred to as STA) in a wireless communication system that communicates with AP-linked transmission diversity,
The central control station is
A sequence start signal is transmitted to the AP1, information on the arrival time difference t transmitted from the STA is received via the AP1, the AP cooperative transmission diversity method is selected based on the arrival time difference t, and the selection is performed. Means for transmitting information to the AP1 and the AP2,
The AP1 transmits a first trigger frame to the AP2 after receiving the sequence start signal, transmits a first test frame to the STA after the transmission, and receives the arrival time difference t information transmitted from the STA. Means for transferring to the central control station and receiving the selection information;
The AP2 includes means for transmitting a second test frame to the STA after receiving the first trigger frame and receiving the selection information,
The STA includes means for detecting an arrival time difference t between the first test frame and the second test frame, and transmitting information on the arrival time difference t to the AP1.
The wireless communication system, wherein the AP1 and the AP2 communicate with the STA by the AP cooperative transmission diversity method based on the selection information. The radio communication system according to claim 6 or 7,
The AP1 includes means for transmitting a second trigger frame to the AP2 after the AP1 obtains the selection information;
The wireless communication system, wherein the AP1 and the AP2 each transmit a data frame having the same contents to the STA after transmitting and receiving the second trigger frame.

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