JP2017011486A - Integrated circuit for radio communication, radio communication terminal, radio communication method, and radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an integrated circuit for radio communication capable of reducing interference from occurring at the receiving side when plural adjacent access points perform a radio communication using an identical frequency.SOLUTION: An integrated circuit for radio communication in an embodiment has a baseband integrated circuit that transmits a signal of a first field which includes a piece of first information specifying a first data stream to a first radio communication terminal and a second information specifying a second data stream to a second radio communication terminal via an RF integrated circuit, transmits the first data stream via the RF integrated circuit, and does not transmit the second data stream.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to an integrated circuit for wireless communication, a wireless communication terminal, a wireless communication method, and a wireless communication system.

  Wireless LAN (Local Area Network) employing CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) is widely known as a wireless communication system that performs communication between a wireless base station device (access point) and a wireless terminal. .

  In single-user MIMO (Multi-Input Multi-Output) technology used in a wireless LAN, one access point and one wireless terminal each have a plurality of antennas. The access point transmits a plurality of data simultaneously from a plurality of antennas. The wireless terminal simultaneously receives the plurality of data with a plurality of antennas and separates the received plurality of data. Thereby, a plurality of data streams can be transmitted and received. As the number of data streams increases, the throughput can be improved as compared to the conventional SISO (Single-Input Single-Output).

  In downlink multi-user MIMO (DL-MU-MIMO) technology, which is an extension of single-user MIMO technology, one access point uses different frequencies from multiple antennas to multiple wireless terminals. Send data simultaneously.

  In the downlink multi-user MIMO technology, a technology called beam forming is used. The beam forming technique is a multi-antenna technique for imparting directivity to radio waves, and can prevent radio wave interference even in communications performed for a plurality of terminals using the same frequency.

  However, in practice, radio wave interference may occur because the propagation path changes as the terminal moves or the surrounding environment changes. For example, when a vehicle that reflects radio waves moves, the radio waves are reflected, and data streams for other wireless devices may be received. Therefore, a wireless terminal that can remove a data stream addressed to another communication device is also known.

  On the other hand, there is a technique (cooperative transmission technique) in which a plurality of access points cooperate to perform communication at the same frequency at the same time, thereby increasing the transmission speed of the entire system. This cooperative transmission technique also uses beamforming. The plurality of access points are synchronized, grasp the position of the wireless terminal belonging to another access point, and perform null steering on the position, thereby suppressing interference with communication terminals under the access point adjacent thereto.

  However, in this case as well, radio wave interference may occur due to changes in the propagation path. And since a communication terminal cannot make the influence of the data stream received from the access point which does not communicate zero, there exists a problem that the data stream from the access point which communicates cannot be received correctly.

JP 2013-1006079 A JP 2014-27368 A

IEEE Std 802.11acTM-2013 IEEE Std 802.11TM-2012

  An embodiment of the present invention aims to reduce interference generated on the receiving side when a plurality of access points perform wireless communication at the same frequency.

  An integrated circuit for wireless communication as an embodiment of the present invention specifies first information for designating a first data stream for a first wireless communication terminal, and designates a second data stream for a second wireless communication terminal The first field signal including the second information to be transmitted is transmitted through the RF integrated circuit, the first data stream is transmitted through the RF integrated circuit, and the second data stream is not transmitted. A baseband integrated circuit is provided.

1 is a block diagram showing an example of a schematic configuration of a wireless communication system according to a first embodiment. The figure which shows an example of the table (group information) regarding a group. The figure which shows an example of the radio communication by downlink multiuser MIMO The figure which shows the frame (VHT PPDU) format in IEEE802.11ac standard. FIG. 3 is a diagram illustrating an example of a schematic configuration of frames of a data stream 1 and a data stream 2. The flowchart of a cooperative transmission process. The figure which shows an example of the collective management of the group information by a parent access point. The figure which shows an example at the time of receiving multiple data streams from different access points in 1st Embodiment. FIG. 2 is a functional block diagram of a wireless communication device mounted on an access point according to the first embodiment. FIG. 2 is a functional block diagram of a wireless communication device mounted on a wireless terminal according to the first embodiment. FIG. 2 is a diagram showing an example of a hardware configuration of a wireless communication device mounted on an access point according to the first embodiment. FIG. 2 is a diagram illustrating an example of a hardware configuration of a wireless communication device mounted on the wireless terminal according to the first embodiment. FIG. 9 is a perspective view of a wireless device according to a third embodiment. The figure which shows the memory card based on 3rd Embodiment. The figure which shows an example of the frame exchange of a contention period.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. IEEE Std 802.11 ^™ -2012 and IEEE Std 802.11ac ^™ -2013, known as wireless LAN standards, are all incorporated herein by reference.

(First embodiment)
FIG. 1 is a block diagram illustrating an example of a schematic configuration of the wireless communication system according to the first embodiment. A wireless communication system according to the first embodiment includes an access point 11, an access point 21, a wireless terminal 1 that performs wireless communication with the access point 11, and a wireless terminal 2 that performs wireless communication with the access point 21. It is a network. An access point is also a form of a wireless terminal.

  Although FIG. 1 shows one wireless terminal communicating with each access point, there may be a plurality of wireless terminals (not shown) communicating with each access point. There may be more than two access points.

  Each of the access points 11 and 21 is equipped with a plurality of antennas and a wireless communication device (see FIG. 9 described later). In the example of FIG. 1, the access point 11 includes four antennas 12A, 12B, 12C, and 12D, and the access point 21 includes four antennas 22A, 22B, 22C, and 22D. The wireless communication device includes a wireless communication unit and a communication control device that controls communication with a plurality of wireless terminals.

  Here, the number of antennas of the access points 11 and 21 is four, but the number of antennas may be any number of two or more. Further, the number of antennas at the access points 11 and 21 may be different. However, the upper limit of the data stream that can be transmitted by the access point is limited by the number of antennas provided. As an example, the upper limit of the data stream that can be transmitted by the access point matches the number of antennas provided.

  Each of the wireless terminal 1 and the wireless terminal 2 is equipped with one or more antennas and a wireless communication device (see FIG. 10 described later). In the example of FIG. 1, it is assumed that the wireless terminal 1 includes one antenna 1A, and the wireless terminal 2 includes one antenna 2A. The wireless communication device includes a wireless communication unit and a communication control device that controls communication with an access point.

  Here, the number of antennas of the wireless terminal 1 and the wireless terminal 2 is 1, but the number of antennas may be an arbitrary number of 1 or more. Further, the number of antennas of the wireless terminal 1 and the wireless terminal 2 may be different.

  Wireless communication from the access point 11 to the wireless terminal 1 and wireless communication from the access point 21 to the wireless terminal 2 can be performed by downlink multi-user MIMO technology defined in the IEEE802.11ac standard. To do. However, wireless communication other than downlink multiuser MIMO technology may be performed. Each access point may perform wireless communication with another wireless terminal in accordance with the IEEE 802.11ac standard, or may perform wireless communication with a communication standard other than IEEE 802.11ac. For example, a wireless terminal (not shown) and the access point 11 or the access point 21 may communicate with a communication standard such as IEEE802.11ac, IEEE802.11n, or IEEE802.11a. Further, communication may be performed using a next-generation communication standard standardized by the IEEE802 committee such as IEEE802.11ax.

  When each access point transmits a plurality of frames to a plurality of terminals, the plurality of frames to be transmitted may be the same or different. As a general expression, when it is expressed that an access point transmits or receives a plurality of frames or a plurality of Xth frames, these frames or the Xth frames may be the same or different. X can be set to any value depending on the situation.

  It is assumed that the access point 11 and the access point 21 are communicatively connected via a wired or wireless connection or via a network such as a WAN or the Internet. Communication between the access point 11 and the access point 21 may be performed by a dedicated interface.

  Next, beam forming which is a function of the access point will be described. Henceforth, when it is only described as an access point, it shall include the access points 11 and 21.

  It is assumed that the access point can perform beam forming with directivity. Beam forming is a multi-antenna technology that gives radio waves directivity. In beam forming, null steering that does not send radio waves in unnecessary directions and beam steering that concentrates radio waves in necessary directions and extends the communication distance than usual are performed.

  In addition, with respect to beam forming, a beam that does not have directivity in radio waves (nondirectionality) and is emitted in all directions is referred to as an omni beam.

  The access point adjusts the communication range by performing beamforming. A white portion surrounded by a dotted line in FIG. 1 indicates a communication range of the access point 11. A gray portion surrounded by a broken line indicates a communication range of the access point 21. The wireless terminal 1 and the wireless terminal 2 exist within the range (communication range) within which the access point 11 and the access point 21 can reach the omni beam. However, the access point 21 adjusts so that the radio wave from the access point 21 does not reach the wireless terminal 1 by null steering. Similarly, the access point 11 adjusts so that the radio wave from the access point 11 does not reach the wireless terminal 2 by null steering.

  It is assumed that the access point grasps in advance propagation path information representing the state of the propagation path from each antenna to each wireless terminal (downlink) in order to perform beam forming. Any method can be used as a method of grasping the propagation path information. For example, there is an Explicit CSI Feedback method that transmits a sounding frame and receives a feedback frame of channel state information (CSI).

  The propagation path of a radio wave changes every moment due to a change in a situation caused by movement of a wireless terminal or movement of a vehicle or the like that reflects the radio wave. Therefore, even if beam forming is performed accurately, radio wave interference occurs. In the example of FIG. 1, the transmission radio wave 32 from the access point 21 is adjusted so as not to reach the wireless terminal 1 by beam forming, but the radio wave 33 generated by reflection or the like reaches the wireless terminal 1. . Therefore, the wireless terminal 1 receives a composite signal of the transmission radio wave 31 from the access point 11 and the transmission radio wave 33 from the access point 21.

  The access point according to the first embodiment uses downlink multi-user MIMO technology to eliminate radio wave interference as in the example of FIG. First, communication between the access point and the wireless terminal as a premise will be described.

  The access point 11 and the access point 21 form a wireless network (referred to as a first network and a first B network, respectively) with a connected wireless terminal. Here, it is assumed that the wireless terminal 1 belongs to the first network and the wireless terminal 2 belongs to the 1B network. The access point 11 and the access point 21 may be further connected to other wired or wireless networks (referred to as a second network and a second B network, respectively).

  The access point relays communication between these networks and between wireless terminals in the same network. Each access point can receive a frame addressed to a wireless terminal belonging to its own network from the wireless terminal or each network, hold it in an internal buffer, and control the transmission timing. The access point can transmit the frame addressed to each wireless terminal to each wireless terminal by spatial multiplexing. Spatial multiplexing transmission means that a plurality of data streams are simultaneously transmitted in the same frequency band. These technologies are included in the downlink multi-user MIMO technology.

  The access point creates one or a plurality of groups and registers a combination of communication destination wireless terminals in each group before starting communication using the downlink multi-user MIMO technology. This group is used when the access point performs spatial multiplexing transmission. That is, spatial multiplexing transmission is performed for each group. One wireless terminal may be registered in a plurality of groups. Further, only one wireless terminal may be registered in one group, or a plurality of wireless terminals may be registered.

  FIG. 2 is a diagram illustrating an example of a table (group information) related to a group held by an access point. Group ID represents an identifier of each group. MSA stands for Membership status array and UPA stands for User position array. The MSA indicates whether the wireless terminal belongs to a group. If the member is a member of the group, the MSA is 1, and if not, the MSA is 0. UPA indicates the number of the wireless terminal in the group. If the wireless terminal is not a member of the group, it is represented by N / A. In the example of FIG. 2, since the MSA of Group ID 1 is 0, the wireless terminal 3 does not belong to the group. Therefore, the UPA of Group ID 1 is N / A.

  The access point can notify Group ID, MSA, and UPA for each wireless terminal using a Group ID Management frame. The group ID management frame is one of the management frames defined in IEEE802.11ac, and the Group ID is represented by 8 octets. Since Group ID uses 0 and 63 as defaults, 62 groups can be registered. For each group ID, MSA is defined as 1 bit and UPA is defined as 2 bits.

  The wireless terminal that has received the group ID management frame holds the group IDs of all the groups held by the access point and the information of its own MSA and UPA in each group. These pieces of information are referred to when acquiring the data stream.

  Next, separation of data streams of wireless terminals in downlink multiuser MIMO technology will be described.

  FIG. 3 is a diagram illustrating an example of wireless communication using downlink multi-user MIMO. In the example of FIG. 3, the access point 11 multiplex-transmits the data stream 1 to the wireless terminal 1 and the data stream 2 to the wireless terminal 3 not shown in FIG.

  Based on the propagation path information from each wireless terminal acquired in advance, the access point calculates a directional beam pattern so as to suppress interference of signals addressed to each wireless terminal. Then, beam forming is performed based on the calculated beam pattern. A portion surrounded by a dotted line in FIG. 3 represents beam forming for the wireless terminal 1. A gray portion surrounded by a broken line represents beam forming for the wireless terminal 3. Each data stream is transmitted simultaneously on the same frequency from the antenna of the access point. Even if transmitted simultaneously at the same frequency, interference can be suppressed by beam forming.

  However, even when there is one access point, a data stream addressed to another terminal may be received due to a change in the propagation path. In the example of FIG. 3, the data stream 2 is adjusted so as not to reach the wireless terminal 1. However, even if the radio stream should not reach the wireless terminal 1, the wireless terminal 1 Even if beam forming is applied, interference may occur on the receiving side. For this reason, the wireless terminal 1 has a function of separating data streams transmitted from the same access point.

h11は、アクセスポイント11のアンテナ12Aから無線端末1のアンテナ1Aまでのチャネル応答を示す。h12は、アンテナ12Bからアンテナ1Aまでのチャネル応答を示す。n1は受信信号に生ずるノイズを示す。
なお、1台の無線端末がアンテナ2本を備え、2つのデータストリームを受信する場合は、無線端末の受信信号y1とy2は、次のように表される。

このように、受信アンテナがm個、送信アンテナがn個の場合は、受信信号Yをm×1行列、送信信号Sをn×1行列、各受信アンテナと各送信アンテナの間の伝搬路における各チャネル応答を表す伝搬路応答行列（チャネル行列）Hをm×n行列、ノイズNをn×1行列とすると、次式が成り立つ。

If the transmission signal of the data stream 1 is s1 and the transmission signal of the data stream 2 is s2, the reception signal y1 of the wireless terminal can be expressed by the following equation. Here, to simplify the description, it is assumed that the transmission signal s1 is transmitted from the antenna 12A and the transmission signal s2 is transmitted from the antenna 12B using the two antennas 12A and 12B.

h11 indicates a channel response from the antenna 12A of the access point 11 to the antenna 1A of the wireless terminal 1. h12 represents a channel response from the antenna 12B to the antenna 1A. n1 represents noise generated in the received signal.
When one wireless terminal is provided with two antennas and receives two data streams, the reception signals y1 and y2 of the wireless terminal are expressed as follows.

In this way, when there are m reception antennas and n transmission antennas, the reception signal Y is an m × 1 matrix, the transmission signal S is an n × 1 matrix, and in the propagation path between each reception antenna and each transmission antenna. When a channel response matrix (channel matrix) H representing each channel response is an m × n matrix and noise N is an n × 1 matrix, the following equation is established.

H^Hは、Hのエルミート転置を表す。このウェイトWを受信信号Yに乗算すると、送信信号Sを求めることができる。

また、特定の送信アンテナの送信信号だけを取り出したい場合には、ウェイトWのその送信信号に対応する行を、受信信号Yに掛けることで、所望の送信アンテナの送信信号を取り出すことができる。 The wireless terminal can obtain a transmission signal using the weight matrix W for the received composite signal. There are various types of weight matrices such as ZF method, MMSE method, MBER method, and the like. As an example, a weight matrix W by the ZF (Zero Forcing) method is shown in the following equation.

H ^H represents Hermitian transpose of H. When this weight W is multiplied by the reception signal Y, the transmission signal S can be obtained.

Further, when it is desired to extract only the transmission signal of a specific transmission antenna, the transmission signal of the desired transmission antenna can be extracted by multiplying the reception signal Y by the row corresponding to the transmission signal of weight W.

  In order to obtain the weight, it is necessary to estimate the channel response of each propagation path. In downlink multiuser MIMO, a channel response is estimated using a propagation path estimation preamble incorporated in a data stream by an access point.

  It is assumed that the receiving terminal holds information regarding the propagation path estimation preamble before transmission is started in downlink multiuser MIMO. As a method of acquiring information related to the propagation path estimation preamble, the information may be acquired from the access point when authenticated with the access point, or a notification frame including the information may be periodically received from the access point. Conversely, a preamble to be used may be designated from the receiving terminal side to the access point. Alternatively, the preamble used by the access point and the receiving terminal may be determined in advance.

  The receiving terminal estimates the channel response of each propagation path based on the actually measured value of the received propagation path estimation preamble and the value of the transmitted propagation path estimation preamble. The wireless terminal calculates a weight W based on the estimated channel response of each propagation path, and correctly separates the data stream received from the access point.

  FIG. 4 is a diagram showing a frame (VHT PPDU) format in the IEEE802.11ac standard. The frame consists of L-STF (Legacy-Short Training Field), L-LTF (Legacy-Long Training Field), Non-VHT portion (Legacy Preamble) consisting of L-SIG (Legacy Signal Field), and VHT-SIG-A (Very high Throughput-Signal Field-A), VHT-STF, a plurality of VHT-LTFs (VHT-LTFs), and a VHT portion composed of VHT-SIG-B.

  The Non-VHT portion is a field that can be recognized by a legacy standard such as IEEE802.11a, and stores information such as signal detection, frequency correction, and transmission speed. The Non-VHT portion enables a communication system in which wireless terminals conforming to the IEEE802.11ac standard and wireless terminals conforming to the legacy standard are mixed.

  The VHT portion is a new format adopted in IEEE802.11ac, and is a preamble related to MIMO functions such as MIMO multiple extension and MU-MIMO.

  Non-VHT portion and VHT-SIG-A (Pre-VHT-modulated field) signals are transmitted by an omni beam. Therefore, it can be received by all wireless terminals communicating with the access point.

  A signal of a VHT portion (VHT-modulated field) other than VHT-SIG-A is transmitted using beamforming. Therefore, when the propagation path does not change, a specific wireless terminal receives it.

  VHT-SIG-A has a 6-bit Group ID subfield and a 3-bit MU NSTS field (MU [0] NSTS, MU [1] NSTS, MU [2] NSTS, MU [3] NSTS). included. The Group ID subfield stores the Group ID of the group that should receive this frame. Each MU NSTS field is associated with the UPA values 0 to 3 in the Group ID in order from the top (from MU [0] to MU [3]). The MU NSTS field stores the number of data streams to be acquired by the corresponding UPA wireless terminal.

  The wireless terminal determines whether it is a frame to be received based on the group information notified in advance in the group ID management frame. For example, the value of the Group ID subfield stored in the frame of FIG. The wireless terminal 1 that has received the frame refers to the held group information and checks the value of the MSA whose Group ID is 2. According to the group information shown in FIG. 2, when the Group ID is 2, the MSA value of the wireless terminal 1 is 1, and the UPA value is 0. From the MSA value, the wireless terminal 1 determines that it belongs to the group. Since the UPA value is 0, check the MU [0] NSTS field. Since the value of the MU [0] NSTS field is 1, the wireless terminal recognizes that it acquires the first data stream.

  VHT-LTFs is a field used for estimating a channel response matrix, and means that a plurality of VHT-LTFs are included. VHT-LTF requires a different number depending on the number of data streams. The access point stores the propagation path estimation preamble in these VHT-LTFs. The wireless terminal acquires a signal to be received from the received combined signal based on the value stored in the VHT-LTF.

If there are two data streams, two VHT-LTFs are required. For the propagation path estimation preamble, for example, the following orthogonal matrix is used.

For 3 or 4 data streams, 4 VHT-LTFs are required. For the propagation path estimation preamble, for example, the following orthogonal matrix is used.

  The orthogonal matrix has a property that row (or column) vectors representing each row (or each column) are orthogonal to each other. An orthogonal vector means that the inner product is zero.

  FIG. 5 is a diagram illustrating an example of a schematic configuration of a frame transmitted by the access point. The top is the Pre-VHT-modulated field (first field), and the second data stream 1 and the third data stream 2 from the top are data streams that are multiplexed and transmitted from the same access point. . Since the signal of the Pre-VHT-modulated field is transmitted by an omni beam, the data of the Pre-VHT-modulated field received by each wireless terminal is the same. Therefore, the Group ID stored in VHT-SIG-A received by each wireless terminal is the same. That is, data stream 1 and data stream 2 are addressed to wireless terminals belonging to the same group. Here, the Group ID is 2.

  VHT-LTFs include a preamble estimation preamble value. Here, as shown in Equation 6, a set of (1, 1) is stored in the data stream 1, and a set of (1, -1) is stored in the data stream 2.

  According to the group information shown in FIG. 2, the data stream 1 is acquired by the wireless terminal 1 and the wireless terminal 3 whose UPA value is 0 when the Group ID is 2. The data stream 2 is acquired by the wireless terminal 2 whose Group ID is 2 and whose UPA value is 1.

  The radio terminal 1 grasps the value of the propagation path estimation preamble included in the data stream based on the value of the propagation path estimation preamble acquired in advance. Then, a channel response of the propagation path is calculated based on the actually measured value of the received propagation path estimation preamble and the transmitted propagation path estimation preamble value.

したがって、伝達応答行列は、次にように求まる。

The received signal related to the first propagation path estimation preamble is y1, and the received signal related to the second propagation path estimation preamble is y2. In the transmission signal of the first propagation path estimation preamble, the value of data stream 1 is 1, and the value of data stream 2 is 1. In the transmission signal of the second propagation path estimation preamble, the value of data stream 1 is 1, and the value of data stream 2 is -1. Therefore, when substituting into Equation 2, the following equation is obtained. The noise N is ignored here for convenience.

Therefore, the transfer response matrix is obtained as follows.

  Based on the channel response obtained as described above, the wireless terminal calculates a weight W and calculates a transmission signal. Then, the data stream to be received is acquired.

  In this way, the wireless terminal can take out the data stream to be acquired even when the data stream signals from the same access point are received in a state where they overlap at the same time.

  The access point 11 and the access point 21 of the first embodiment utilize the above-described functions of the wireless terminal and perform the following operations, so that the configuration of the wireless terminal is not changed and the like shown in FIG. This makes it possible to separate radio signals from different access points.

  FIG. 6 is a diagram illustrating a flowchart of cooperative transmission performed by an access point. Hereinafter, processing of the access point 11 and the access point 21 will be described.

  To enable data stream separation, communication between the access point 11 and the wireless terminal 1 (first communication) and communication between the access point 21 and the wireless terminal 2 (second communication) are performed simultaneously. Adjusted. The access point 11 and the access point 21 synchronize with respect to the transmission frequency and transmission time of the frame (S101). As a synchronization method, a dedicated notification frame may be transmitted, or information regarding synchronization may be incorporated into a beacon frame or the like. The synchronization timing may be before wireless communication or may be performed periodically, but is assumed to be completely synchronized before transmitting a frame.

  Each of the access point 11 and the access point 21 generates a frame to be transmitted (S102). At this time, the Pre-VHT-modulated field part of the two transmission frames is set to be the same.

  Each of the access point 11 and the access point 21 needs to transmit the signal of the Pre-VHT-modulated field part to all the wireless terminals belonging to the network. When the wireless terminal receives the signal of the Pre-VHT-modulated field part addressed to another wireless terminal, the wireless terminal waits for transmission to the access point until the time set in L-SIG of the Pre-VHT-modulated field elapses. To do. On the contrary, when the signal of the Pre-VHT-modulated field portion is not received, the wireless terminal may send a communication request to the access point, which affects the wireless communication of the access point. Thus, each of the access point 11 and the access point 21 transmits the signal of the Pre-VHT-modulated field part to all the wireless terminals belonging to the network, thereby avoiding the influence on the communication between the wireless terminals 1 and 2.

  Then, the wireless terminals 1 and 2 also receive the signal of the Pre-VHT-modulated field part. And, if the signal of the Pre-VHT-modulated field part transmitted by the access point 11 and the signal of the Pre-VHT-modulated field part transmitted by the access point 21 are different, interference occurs, and the wireless terminals 1 and 2 The data cannot be demodulated correctly. Therefore, in the embodiment of the present invention, the data of the Pre-VHT-modulated field part is set to be the same.

  The L-STF and L-LTF in the Pre-VHT-modulated field do not differ between the two transmission frames as long as the values defined in the IEEE802.11ac standard are set. Also, since the length of the entire transmission frame is stored in L-SIG, there is no difference between the two transmission frames as long as this length is combined. However, VHT-SIG-A of the Pre-VHT-modulated field includes subfields related to the designated data stream, such as the Group ID, the number of data streams acquired by each wireless terminal, and the data frame encoding method. Therefore, the access point 11 and the access point 21 adjust so that the values of these subfields do not differ in each transmission frame. Further, the value of the subfield to be used may be determined in advance.

  The number of data streams acquired by each wireless terminal is specified in each MU NSTS field. The number of data streams acquired by each wireless terminal is the same. Here, since the number of data streams acquired by each wireless terminal is one, 1 is stored in each of the MU [0] NSTS and MU [1] NSTS fields shown in FIG. 4, and MU [3] NSTS In the MU [4] NSTS field, 0 is stored.

  The Group ID value is set to be the same in the two frames, but the UPA corresponding to the specified Group ID is adjusted to be different between the wireless terminal 1 and the wireless terminal 2. This is because the wireless terminal 1 and the wireless terminal 2 acquire different data streams. Here, the UPA of the wireless terminal 1 is 0, and the UPA of the wireless terminal 2 is 1.

  The method for determining the Group ID may be any method. For example, the access point 11 transmits the value of the Group ID to be used and the value of the UPA of the wireless terminal 1 in the group to the access point 21 when synchronizing with the access point 21 regarding the transmission frequency and the transmission time. The access point 21 refers to the group whose Group ID is 2 from the group information held by itself, and checks whether the UPA value of the wireless terminal 2 is different from the transmitted UPA value of the wireless terminal 1. If the values are different, the group with Group ID 2 can be used, but if the values are the same, the group with Group ID 2 cannot be used. The access point 21 returns the reference result to the access point 11. The access point 11 uses the Group ID when it receives a reply result indicating that it can be used, and determines the group to be used again when it receives a reply result that it cannot be used.

  Further, for example, the group ID used when the access point 11 and the access point 21 perform simultaneous transmission may be determined in advance. Further, the access point 11 and the access point 21 may share the group information, and the access point that receives the frame addressed to the wireless terminal 1 or 2 may determine the Group ID. Alternatively, a parent access point (Master) may be determined in advance, and the parent access point may centrally manage group information of child access points (Slave), and determine a Group ID to be used. The parent access point may be prepared separately from the access point 11 and the access point 21. In addition, the parent access point may determine not only the Group ID but also the transmission frequency and transmission time. Further, the parent access point may be a management device such as a server instead of an access point.

  FIG. 7 is a diagram illustrating an example of group management of group information by a parent access point. In the example of FIG. 7, the access point 11 is a parent access point, and the access point 21 and the access point 31 not shown in FIG. 1 are child access points. As shown in the upper right of FIG. 7, the parent access point holds its own group information and child access point group information. The child access point holds only its own group information. The parent access point manages group information of each child access point by a notification frame or the like periodically or every time group information is updated from the child access point.

  Here, since the wireless terminal 1 and the wireless terminal 2 perform simultaneous transmission, the parent access point checks the UPA of the wireless terminal 1 and the wireless terminal 2 of each Group ID. According to the group information on the upper right, the group with Group ID 1 cannot be used because the wireless terminal 2 does not belong to the group. A group with Group ID 2 can be used because the UPA of wireless terminal 1 and wireless terminal 2 is different from 0 and 1, respectively. A group with Group ID 3 can also be used because the UPA of wireless terminal 1 and wireless terminal 2 is different from 1 and 0, respectively. A group with a Group ID of 4 cannot be used because the UPA of both the wireless terminal 1 and the wireless terminal 2 is 1. In this way, the parent access point determines an available group ID. If there are multiple Group IDs that can be used, one can be arbitrarily determined. If the parent access point selects a group with Group ID 2, the UPA of the wireless terminal 1 is 0 and the UPA of the wireless terminal 2 is 1 as before. Also, Group ID 2 is set in the Group ID subfield of VHT-SIG-A.

  The access point 11 and the access point 21 simultaneously transmit a signal in the Pre-VHT-modulated field using the omni beam and at the same frequency (S103). The transmitted two signals are received by the wireless terminal 1 and the wireless terminal 2 at substantially the same timing. In this case, since they have the same frequency and the same data, signals received simultaneously or later can be handled as multipath delayed wave signals sent from the same access point.

  The IEEE802.11 communication standard employs a mechanism that reduces multipath delayed waves. For example, an OFDM (Orthogonal Frequency Division Multiplexing) modulation method used in IEEE802.11ac standardizes a technique for suppressing interference due to a delayed wave, such as a guard interval. Therefore, the wireless terminal can exhibit a function of suppressing interference without distinction from signals received from the same access point even when signals from different access points are received.

  The wireless terminal 1 and the wireless terminal 2 grasp the stream to be acquired from the group ID of the VHT-SIG-A and the value of the MU NSTS field of the acquired frame. As described above, since the wireless terminal 1 and the wireless terminal 2 have selected Group IDs that do not have the same UPA, the wireless terminals 1 and 2 do not acquire the same data stream. For example, when a group with Group ID 2 is selected by the parent access point described above, 2 is stored in the Group ID subfield of VHT-SIG-A. Further, as described above, 1 is stored in each of the MU [0] NSTS and MU [1] NSTS fields, and 0 is stored in each of the MU [3] NSTS and MU [4] NSTS fields. Thereby, the wireless terminal 1 whose UPA is 0 selects the data stream 1, and the wireless terminal whose UPA is 2 selects the data stream 2.

  The access point 11 and the access point 21 simultaneously transmit a data stream (VHT-modulated field) by beam forming at the same frequency (S104). Here, data to be received by the wireless terminal 1 is stored in the VHT-modulated field of the data stream 1 transmitted by the access point 11. Only null data is stored in the VHT-modulated field of the data stream 2 transmitted by the access point 11. On the other hand, only null data is stored in the VHT-modulated field of the data stream 1 transmitted by the access point 21. Data to be received by the wireless terminal 2 is stored in the VHT-modulated field of the data stream 2 transmitted by the access point 21.

  The radio terminal 1 and the radio terminal 2 receive a data stream storing normal data and a data stream storing only null data from each of the access points. That is, each of the wireless terminal 1 and the wireless terminal 2 receives four streams. However, the combined signal received by each of the wireless terminal 1 and the wireless terminal 2 is the same as when the data stream 1 and the data stream 2 are simultaneously transmitted from the same access point and these two data streams are received.

  FIG. 8 is a diagram illustrating an example when a plurality of data streams are received from different access points due to a change in the state of the propagation path. From the access point 11, a data stream 1 (DS1) including data and a data stream 2 including null data, which are indicated by white arrows, are transmitted. From the access point 21, a data stream 1 (DS1) including null data and a data stream 2 (DS2) including data, which are indicated by gray arrows, are transmitted. Each antenna of the wireless terminal 1 and the wireless terminal 2 receives a combined signal in which signals of up to four data streams are combined. However, since the signal related to the data stream 1 is a data stream containing data and the other is a data stream containing only null data, the two combined signals are the same as the signals of the data stream containing data. In addition, since the signal of the data stream 2 is also a data stream including data and the other is a data stream including only null data, the two combined signals are the same as the signals of the data stream including data. Therefore, the result is the same as when the signals of data stream 1 and data stream 2 are received from the same access point shown in FIG.

  The wireless terminal 1 separates the received data stream. The separation method is the same as when two data streams are received from the same access point. Therefore, the radio terminal 1 can extract a necessary data stream by separating from an unnecessary data stream from a different access point without changing the configuration or the like.

  Here, the antenna of the wireless terminal is one, but there is no problem with two antennas. In the case of two, four data streams are used. The wireless terminal 11 stores normal data in the data streams 1 and 2, and stores only null data in the data streams 3 and 4. Conversely, the wireless terminal 21 may store only null data in the data streams 1 and 2 and store normal data in the data streams 3 and 4. Other than that, the wireless terminal has the same antenna.

  Although it is assumed here that wireless communication is performed according to the IEEE802.11ac standard, the communication standard is not limited thereto. For example, in IEEE802.11ac, the frequency band to be used is the 5 GHz band, but the frequency may be a 2.4 GHz band or a 60 GHz band. Since the frequency (number of channels) that can be used is limited in the 2.4 GHz band, it is assumed that there are more scenes in which adjacent access points transmit and receive at the same frequency than in the 5 GHz band. Therefore, the significance of reducing the residual interference with the same frequency is higher in the 2.4 GHz band than in the 5 GHz band.

  As described above, the access point cooperates with other access points, and the frame in which the values of the Pre-VHT-modulated field and the VHT-modulated field (data stream) are adjusted is the same in the transmission signal of the same frequency. By transmitting at the timing, the wireless terminal can separate a data stream received from an access point different from the access point to which the wireless terminal belongs without changing the configuration of the wireless terminal.

  FIG. 9 is a functional block diagram of a wireless communication device mounted on the access point according to the first embodiment. As described above, the access point 11 may be connected to a network different from the first network (second network) in addition to the network on the wireless terminal side (first network). 1 shows the configuration of the wireless communication apparatus. Since the wireless communication apparatus mounted on the access point 21 has the same configuration as that of the access point 1, the description of the access point 21 is omitted.

  The upper layer performs communication processing above the MAC layer, such as TCP / IP and UDP / IP, and processing of the application layer that processes data. The upper layer receives the frame received from the communication device on the first network via the buffer 104. The frame includes a frame for sending to a communication device such as a wireless terminal or a server that exists in a network other than the first network. The buffer 104 is a storage unit for transferring frames between the upper layer and the control unit 101.

  The control unit 101 corresponds to a communication control device that controls communication with a communication device such as the wireless terminal 1 that exists in the first network. As an example, the transmission unit 102 and the reception unit 103 form a wireless communication unit.

  The control unit 101 mainly performs part of the MAC layer processing and physical layer processing (for example, MIMO-related processing). The control unit 101 controls communication with each wireless terminal in the first network by transmitting and receiving frames via the transmission unit 102 and the reception unit 103. Note that the control unit 101 may perform control so that a beacon frame is periodically transmitted. Further, the sounding frame may be periodically transmitted to control the propagation path state information.

  Upon receiving an association request from a wireless terminal, the control unit 101 establishes a wireless link with the wireless terminal through a process such as authentication as necessary. The control unit 101 periodically checks the buffer 104. Alternatively, the control unit 101 confirms the buffer 104 by an external trigger such as the buffer 104. In addition, control is performed so that transmission is performed to the transmission unit at the transmission timing determined in cooperation with the access point 21.

  The control unit 101 determines the transmission frequency and transmission time of the frame, data to be stored in the frame, etc. in cooperation with the access point 21. Also, a frame is generated, and the transmission unit 102 is controlled so that the frame is transmitted at the transmission time.

  Note that all frames need not be transmitted by downlink multi-user MIMO. For example, a management frame such as a group ID management frame and a control frame may not use downlink multiuser MIMO. Various management frames and control frames are also stored in the buffer 104 as necessary, and can be transmitted by the control unit 101 reading out from the buffer 104.

  The control unit 101 may include a clock generation unit that generates a clock, or may include a clock acquisition unit that acquires a clock from the outside. The control unit 101 may manage the internal time based on a clock generated by the clock generation unit or an externally input clock. The control unit 101 may output the clock generated by the clock generation unit to the outside.

  The control unit 101 may access the storage device for information to be transmitted to the base station and read the information, or store the information received from the base station in the storage device. The storage device may be a buffer (internal memory) provided in the control unit 101, a buffer 104 (external memory) provided outside the control unit 101, or a buffer different from the buffer 104. The storage device may be a volatile memory such as DRAM or a non-volatile memory such as NAND or MRAM. In addition to the memory, the storage device may be an SSD, a hard disk, or the like.

  The transmission unit 102 includes a transmission system corresponding to each antenna, and performs processing of a desired physical layer such as modulation processing or addition of a physical header to a frame input from the control unit 101 using a specific transmission system. . Further, DA conversion, filter processing for extracting a signal component in a desired band, and frequency conversion (up-conversion) are performed on the frame after processing in the physical layer. Transmitter 102 amplifies the frequency-converted signal and radiates it as a radio wave from any one antenna to the space. A configuration in which a frame is input to a plurality of transmission systems and transmitted from a plurality of antennas is also possible.

  The transmission unit 102 switches the type of beam (omni beam and beam forming) for transmitting a frame based on an instruction from the control unit 101 or a predetermined setting.

  The receiving unit 103 processes a signal received by each antenna for each reception system corresponding to the antenna, and inputs the signal to the control unit 101. The received signal is amplified by the receiving unit 103, subjected to frequency conversion (down-conversion), and a desired band component is extracted by a filering process. Each extracted signal is further converted into a digital signal by AD conversion, subjected to physical layer processing such as demodulation, and then input to the control unit 101.

  The above-described separation of the processes of the control unit 101 and the transmission unit 102 is an example, and other forms are possible. For example, processing up to the digital area may be performed by the control unit 101, and processing after DA conversion may be performed by the transmission unit 102. Similarly for the separation of the processing of the control unit 101 and the receiving unit 103, the processing up to AD conversion is performed by the receiving unit 103, and the processing of the digital area including the processing of the physical layer thereafter is performed by the control unit 101. Good. Carvings other than those described here may be performed.

  All or part of the processing of each part of the access point and the digital area of the upper layer, or the processing of the communication processing device may be performed by software (program) that operates on a processor such as a CPU or by hardware. It may be performed by both of these software and hardware. The terminal may include a processor that performs processing of all or a part of each unit or processing of the communication processing device.

  FIG. 10 is a functional block diagram of a wireless communication device mounted on the wireless terminal according to the first embodiment. Since the wireless communication device mounted on the wireless terminal 2 has the same configuration as the wireless terminal 1, the description of the wireless terminal 2 is omitted.

  The upper layer performs communication processing above the MAC layer, such as TCP / IP and UDP / IP, and processing of the application layer that processes data. The upper layer generates a frame to be transmitted to the communication device on the first network such as the access point 11 and stores it in the buffer 204. Also, the frame received from the communication device on the first network is received via the buffer 204. The buffer 204 is a storage unit for transferring frames between the upper layer and the control unit 201.

  The control unit 201 corresponds to a communication control device that controls communication with a communication device that exists in the first network, such as the access point 11, and the transmission unit 202 and the reception unit 203 form a wireless communication unit as an example.

  The control unit 201 mainly performs MAC layer processing. The control unit 201 controls communication with the access point 11 by transmitting and receiving frames to and from the access point 11 via the transmission unit 202 and the reception unit 203. For example, the control unit 201 receives a beacon frame periodically transmitted from the access point 11 via the antenna 1A and the reception unit 203.

  For example, the control unit 201 receives a beacon signal, makes an association request to the access point 11, and establishes a wireless link with the access point 11 through a process such as authentication as necessary. The control unit 201 periodically checks the buffer 204. Alternatively, the control unit 201 confirms the buffer 204 by an external trigger such as the buffer 204. When the control unit 201 confirms that there is a frame to be transmitted to the access point 11, the control unit 201 reads the frame and transmits it through the transmission unit 202 and the antenna 1A according to the communication method to be used.

  The control unit 201 estimates the downlink channel response of the propagation path based on the preamble set in the VHT-LTF field of the signal input from each reception system. Further, the control unit 201 calculates a weight based on the downlink propagation path response matrix obtained by the estimation, and separates the data stream based on the weight. As a result, the wireless terminal 1 can receive the data frame transmitted from the access point at the same time without interference.

  Note that the control unit 201 may include a clock generation unit that generates a clock, or may include a clock acquisition unit that acquires a clock from the outside. The control unit 201 may manage the internal time based on a clock generated by the clock generation unit or an externally input clock. The control unit 201 may output the clock generated by the clock generation unit to the outside.

  The control unit 201 may access the storage device for information to be transmitted to the base station and read the information, or store information received from the base station in the storage device. The storage device may be a buffer (internal memory) provided in the control unit 201, a buffer 204 (external memory) provided outside the control unit 201, or a buffer different from the buffer 204. The storage device may be a volatile memory such as DRAM or a non-volatile memory such as NAND or MRAM. In addition to the memory, the storage device may be an SSD, a hard disk, or the like.

  The transmission unit 202 performs desired physical layer processing such as modulation processing and addition of a physical header to the frame input from the control unit 201. Further, DA conversion, filter processing for extracting a signal component in a desired band, and frequency conversion (up-conversion) are performed on the frame after processing in the physical layer. Transmitter 202 amplifies the frequency-converted signal and radiates it as a radio wave from the antenna.

  The reception unit 203 processes a signal received by the antenna for each reception system corresponding to the antenna, and inputs the signal to the control unit 201. The reception signal is amplified by the reception unit 203, subjected to frequency conversion (down-conversion), and a desired band component is extracted by a filering process. Each extracted signal is further converted into a digital signal by AD conversion, subjected to physical layer processing such as demodulation, and then input to the control unit 201.

  The above-described separation of the processes of the control unit 201 and the transmission unit 202 is an example, and other forms are possible. For example, processing up to the digital domain may be performed by the control unit 201, and processing after DA conversion may be performed by the transmission unit 202. Similarly for the separation of the processing of the control unit 201 and the reception unit 203, the processing up to AD conversion is performed by the reception unit 203, and the processing of the digital area including the subsequent physical layer processing is performed by the control unit 201. Good. Carvings other than those described here may be performed.

  All or a part of the processing of each part of the wireless terminal and the digital domain of the upper layer, or the processing of the communication processing device may be performed by software (program) that operates on a processor such as a CPU or by hardware. It may be performed by both of these software and hardware. The terminal may include a processor that performs processing of all or a part of each unit or processing of the communication processing device.

  As described above, in this embodiment, an access point cooperates with other access points to transmit frames with the pre-VHT-modulated field and the VHT-modulated field (data stream) adjusted in the same frequency. By transmitting the signal at the same timing, the wireless terminal can separate the data stream received from the access point different from the access point to which the wireless terminal belongs without changing the configuration of the wireless terminal.

(Second embodiment)
FIG. 11 shows an example of the hardware configuration of the wireless communication device mounted on the access point according to the first embodiment. This configuration example is an example, and the present embodiment is not limited to this. Since the basic operation is the same as that of the wireless communication apparatus shown in FIG. 9, the description will focus on the difference in configuration, and a duplicate description will be omitted.

  This wireless communication apparatus includes a baseband unit 111, an RF unit 121, and antennas 12A to 12D.

  The baseband unit 111 includes a control circuit (protocol stack) 112, a transmission processing circuit 113, a reception processing circuit 114, DA conversion circuits 115 and 116, and AD conversion circuits 117 and 118. The RF unit 121 and the baseband unit 111 may be configured by a one-chip IC (Integrated Circuit).

  The baseband unit 111 is, for example, a baseband LSI or a baseband IC. As another example, the baseband unit 111 may include an IC 132 and an IC 131. At this time, the IC 132 may include the control circuit 112, the transmission processing circuit 113, and the reception processing circuit 114, and the IC 131 may include the DA conversion circuits 115 and 116 and the AD conversion circuits 117 and 118.

  The control circuit 112 corresponds to, for example, a communication control device that controls communication or a control unit that controls communication. At this time, the wireless communication unit may include a transmission processing circuit 113 and a reception processing circuit 114. Further, the wireless communication unit may include DAs 115 and 116 and DAs 117 and 118 in addition to the transmission processing circuit 113 and the reception processing circuit 114. Further, the wireless communication unit may include a transmission circuit 122 and a reception circuit 123 in addition to the transmission processing circuit 113, the reception processing circuit 114, the DA 115 and 116, and the AD 117 and 118. The integrated circuit according to the present embodiment includes all or part of processing of the baseband unit 111, that is, all or part of the control circuit 112, transmission processing circuit 113, reception processing circuit 114, DA115, 116 and DA117, 118. A processor that performs processing may be provided.

  Alternatively, the IC 132 may correspond to a communication control device that controls communication. At this time, the wireless communication unit may include a transmission circuit 122 and a reception circuit 123. Further, the wireless communication unit may include DAs 115 and 116 and ADs 117 and 118 in addition to the transmission circuit 122 and the reception circuit 123.

  The control circuit 112 in the baseband unit 111 includes the buffer 104 in FIG. 9, and performs processing such as a MAC layer. The control circuit 112 may include a clock generation unit. The transmission processing circuit 113 performs desired physical layer processing such as modulation processing and addition of a physical header, and generates, for example, two types of digital baseband signals (hereinafter, digital I signal and digital Q signal). In the case of MIMO transmission, two types of digital baseband signals are generated for each stream. The DA conversion circuits 115 and 117 DA convert the signal input from the transmission processing circuit 113. More specifically, the DA conversion circuit 215 converts the digital I signal into an analog I signal, and the DA conversion circuit 216 converts the digital Q signal into an analog Q signal. Note that there may be a case where the signal is transmitted as it is without a quadrature modulation. In this case, only one DA conversion circuit is required. Further, in the case where one or a plurality of transmission signals are distributed and transmitted by the number of antennas, a number of DA conversion circuits corresponding to the number of antennas may be provided.

  The RF unit 121 is, for example, an RF analog IC or a high frequency IC. The transmission circuit 122 in the RF unit 121 uses a transmission filter that extracts a signal of a desired band from the signal of the frame after DA conversion, and a signal of a constant frequency supplied from the oscillation device, and converts the filtered signal to a radio frequency. Includes a mixer for up-conversion and a preamplifier (PA) for amplifying the signal after up-conversion.

  The receiving circuit 123 in the RF unit 121 uses an LNA (low noise amplifier) that amplifies the signal received by the antenna, and uses a constant frequency signal supplied from the oscillation device to downconvert the amplified signal to baseband. And a receiving filter for extracting a signal in a desired band from the signal after down-coating. More specifically, the reception circuit 123 performs quadrature demodulation on a reception signal amplified by a low-noise amplifier (not shown) using a carrier wave that is 90 ° out of phase with each other to obtain an I (In-phase) signal having the same phase as the reception signal. ) Signal and a Q (Quad-phase) signal whose phase is delayed by 90 ° therefrom. These I signal and Q signal are output from the receiving circuit 123 after the gain is adjusted.

  AD conversion circuits 117 and 118 in the baseband unit 111 AD convert the input signal from the reception circuit 123. More specifically, the AD conversion circuit 117 converts the I signal into a digital I signal, and the AD conversion circuit 118 converts the Q signal into a digital Q signal. There may be a case where only one system signal is received without performing quadrature demodulation. In this case, only one AD conversion circuit is required. When a plurality of antennas are provided, the number of AD conversion circuits corresponding to the number of antennas may be provided. The reception processing circuit 114 performs physical layer processing, demodulation processing, and the like. The control circuit 112 performs processing such as a MAC layer on the demodulated frame.

  Note that a switch for switching the antennas 12A to 12D to any one of the transmission circuit 122 and the reception circuit 123 may be disposed in the RF unit. By the switch control, the antennas 12A to 12D are connected to the transmission circuit 122 during transmission, and the antennas 12A to 12D are connected to the reception circuit 123 during reception.

  Details of the processing of each part described above are self-evident from the description of FIG.

  FIG. 12 shows an example of a hardware configuration of a wireless communication device mounted on the wireless terminal according to the first embodiment. This configuration example is an example, and the present embodiment is not limited to this. Since the basic operation is the same as that of the wireless communication apparatus shown in FIG. 10, the description will focus on the difference in configuration, and a duplicate description will be omitted.

  This wireless communication apparatus includes a baseband unit 211, an RF unit 221, and an antenna 1A. The RF unit 221 and the baseband unit 211 may be configured by a one-chip IC.

  The baseband unit 211 includes a control circuit (protocol stack) 212, a transmission processing circuit 213, a reception processing circuit 214, DA conversion circuits 215 and 216, and AD conversion circuits 217 and 218.

  The baseband unit 211 is, for example, a baseband LSI or a baseband IC. As another example, the baseband unit 211 may include an IC232 and an IC231. At this time, the IC 232 may include a control circuit 212, a transmission processing circuit 213, and a reception processing circuit 214, and the IC 231 may include DA conversion circuits 215 and 216 and AD conversion circuits 217 and 218.

  The control circuit 212 corresponds to, for example, a communication control device that controls communication or a control unit that controls communication. At this time, the wireless communication unit may include a transmission processing circuit 213 and a reception processing circuit 214. Further, the wireless communication unit may include DA 215 and 216 and DA 217 and 218 in addition to the transmission processing circuit 213 and the reception processing circuit 214. Further, the wireless communication unit may include a transmission circuit 222 and a reception circuit 223 in addition to the transmission processing circuit 213, the reception processing circuit 214, the DA 215 and 216, and the DA 217 and 218. The integrated circuit according to this embodiment includes all or part of the processing of the baseband unit 211, that is, all or part of the control circuit 212, transmission processing circuit 213, reception processing circuit 214, DA215, 216 and DA217, 218. A processor that performs processing may be provided.

  Alternatively, the IC 232 may correspond to a communication control device that controls communication. At this time, the wireless communication unit may include a transmission circuit 222 and a reception circuit 223. Further, the wireless communication unit may include DA 215 and 216 and DA 217 and 218 in addition to the transmission circuit 222 and the reception circuit 223.

  The control circuit 212 in the baseband unit 211 includes the buffer 204 in FIG. 10 and performs processing such as a MAC layer. The control circuit 212 may include a clock generation unit. The transmission processing circuit 213 performs desired physical layer processing such as modulation processing and addition of a physical header, and generates, for example, two types of digital baseband signals (hereinafter, digital I signal and digital Q signal). In the case of MIMO transmission, two types of digital baseband signals are generated for each stream. The DA conversion circuits 215 and 216 DA convert the signal input from the transmission processing circuit 213. More specifically, the DA conversion circuit 215 converts the digital I signal into an analog I signal, and the DA conversion circuit 216 converts the digital Q signal into an analog Q signal. Note that there may be a case where the signal is transmitted as it is without a quadrature modulation. In this case, only one DA conversion circuit is required. Further, in the case where one or a plurality of transmission signals are distributed and transmitted by the number of antennas, a number of DA conversion circuits corresponding to the number of antennas may be provided.

  The RF unit 221 is, for example, an RF analog IC or a high frequency IC. The transmission circuit 222 in the RF unit 221 uses a transmission filter that extracts a signal in a desired band from the signal of the frame after DA conversion, and a signal with a constant frequency supplied from the oscillation device, and converts the filtered signal to a radio frequency. Includes a mixer for up-conversion and a preamplifier (PA) for amplifying the signal after up-conversion.

  The receiving circuit 223 is an LNA (low noise amplifier) that amplifies the signal received by the antenna, a mixer that downconverts the amplified signal to baseband using a signal of a constant frequency supplied from the oscillation device, and down A reception filter that extracts a signal in a desired band from the signal after the conversion is included. More specifically, the reception circuit 223 performs quadrature demodulation on a reception signal amplified by a low-noise amplifier (not shown) using a carrier wave that is 90 ° out of phase with each other to obtain an I (In-phase) in-phase with the reception signal. ) Signal and a Q (Quad-phase) signal whose phase is delayed by 90 ° therefrom. These I and Q signals are output from the receiving circuit 223 after the gain is adjusted.

  The AD conversion circuits 217 and 218 in the baseband unit 211 AD convert the input signal from the reception circuit 223. More specifically, the AD conversion circuit 117 converts the I signal into a digital I signal, and the AD conversion circuit 118 converts the Q signal into a digital Q signal. There may be a case where only one system signal is received without performing quadrature demodulation. In this case, only one AD conversion circuit is required. When a plurality of antennas are provided, the number of AD conversion circuits corresponding to the number of antennas may be provided. The reception processing circuit 214 performs physical layer processing, demodulation processing, and the like. The control circuit 212 performs processing such as a MAC layer on the demodulated frame.

  When the wireless terminal includes a plurality of antennas and supports MIMO, the control circuit 212 also performs processing related to MIMO. For example, propagation path estimation processing, transmission weight calculation processing, stream separation processing, and the like are performed.

  Note that a switch for switching the antenna 1A to one of the transmission circuit 222 and the reception circuit 223 may be disposed in the RF unit 221. By switch control, the antenna 1A is connected to the transmission circuit 222 during transmission, and the antenna 1A is connected to the reception circuit 223 during reception.

  Details of the processing of each unit described above are self-explanatory from the description of FIG.

(Third embodiment)
FIG. 13A and FIG. 13B are perspective views of a wireless terminal according to the third embodiment, respectively. The wireless terminal in FIG. 13A is a notebook PC 301, and the wireless terminal in FIG. 13B is a mobile terminal 321. The notebook PC 301 and the mobile terminal 321 are equipped with wireless communication devices 305 and 315, respectively. As the wireless communication devices 305 and 315, the wireless communication device (FIGS. 10 and 12 etc.) mounted on the wireless terminal described so far, or the wireless communication device mounted on the access point 11 (FIGS. 9 and 11) Etc.) can be used. A wireless terminal equipped with a wireless communication device is not limited to a notebook PC or a mobile terminal. For example, TV, digital camera, wearable device, tablet, smartphone, game device, network storage device, monitor, digital audio player, web camera, video camera, project, navigation system, external adapter, internal adapter, set top box, gateway, It can also be installed in printer servers, mobile access points, routers, enterprise / service provider access points, portable devices, handheld devices, and the like.

  In addition, a wireless communication device mounted on a wireless terminal or access point can also be mounted on a memory card. FIG. 14 shows an example in which the wireless communication device is mounted on a memory card. The memory card 331 includes a wireless communication device 355 and a memory card main body 332. The memory card 331 uses a wireless communication device 335 for wireless communication with an external device (such as a wireless terminal or an access point). In FIG. 14, description of other elements in the memory card 331 (for example, a memory) is omitted.

(Fourth embodiment)
In the fourth embodiment, a bus, a processor unit, and an external interface unit are provided in addition to the configuration of the wireless communication apparatus (such as FIG. 12 or FIG. 13) according to any one of the first to third embodiments. The processor unit and the external interface unit are connected to the buffer via the bus. Firmware operates in the processor unit. As described above, by configuring the firmware to be included in the wireless communication device, it is possible to easily change the function of the wireless communication device by rewriting the firmware. The processor unit on which the firmware operates may be a processor that performs processing of the communication control device or the control unit according to the present embodiment, or another processor that performs processing related to function expansion or change of the processing. Also good. The access point or wireless terminal according to the present embodiment may include a processor unit on which firmware operates. Alternatively, the processor unit may be provided in an integrated circuit in a wireless communication device mounted on an access point or an integrated circuit in a wireless communication device mounted on a wireless terminal.

(Fifth embodiment)
In the fifth embodiment, in addition to the configuration of the wireless communication device (access point wireless communication device or wireless terminal wireless communication device) according to any one of the first to third embodiments, a clock generation unit is provided. The clock generation unit generates a clock and outputs the clock from the output terminal to the outside of the wireless communication device. Thus, the host side and the wireless communication apparatus side can be operated in synchronization by outputting the clock generated inside the wireless communication apparatus to the outside and operating the host side with the clock output to the outside. It becomes possible.

(Sixth embodiment)
In the sixth embodiment, in addition to the configuration of the wireless communication device (access point wireless communication device or wireless terminal wireless communication device) according to any one of the first to third embodiments, a power supply unit, a power supply control unit, And a wireless power feeder. The power supply control unit is connected to the power supply unit and the wireless power supply unit, and performs control to select a power supply to be supplied to the wireless communication device. As described above, by providing the wireless communication apparatus with the power supply, it is possible to perform a low power consumption operation by controlling the power supply.

(Seventh embodiment)
In the seventh embodiment, a SIM card is included in addition to the configuration of the wireless communication apparatus according to the sixth embodiment. The SIM card is connected to a transmission unit (102 or 202), a reception unit (103 or 203), or a control unit (101 or 201) in the wireless communication apparatus. As described above, the authentication process can be easily performed by providing the wireless communication apparatus with the SIM card.

(Eighth embodiment)
The eighth embodiment includes a moving image compression / decompression unit in addition to the configuration of the wireless communication apparatus according to the fourth embodiment. The moving image compression / decompression unit is connected to the bus. As described above, by providing the wireless communication device with the moving image compression / decompression unit, it is possible to easily transmit the compressed moving image and expand the received compressed moving image.

(Ninth embodiment)
The ninth embodiment includes an LED unit in addition to the configuration of the wireless communication device (access point wireless communication device or wireless terminal wireless communication device) according to any one of the first to third embodiments. The LED unit is connected to the transmission unit (102 or 202), the reception unit (103 or 203), or the control unit (101 or 201). As described above, by providing the wireless communication device with the LED unit, it is possible to easily notify the user of the operation state of the wireless communication device.

(Tenth embodiment)
In the tenth embodiment, in addition to the configuration of the wireless communication device (access point wireless communication device or wireless terminal wireless communication device) according to any one of the first to third embodiments, a vibrator unit is included. The vibrator unit is connected to the transmission unit (102 or 202), the reception unit (103 or 203), or the control unit (101 or 201). As described above, by providing the radio communication device with the vibrator unit, it is possible to easily notify the user of the operation state of the radio communication device.

(Eleventh embodiment)
The thirteenth embodiment includes a display in addition to the configuration of the wireless communication apparatus (access point wireless communication apparatus or wireless terminal wireless communication apparatus) according to any one of the first to fifth embodiments. The display may be connected to the control unit 101 or the control unit 201 of the wireless communication apparatus via a bus (not shown). Thus, it is possible to easily notify the user of the operation state of the wireless communication device by providing the display and displaying the operation state of the wireless communication device on the display.

(Twelfth embodiment)
In this embodiment, [1] frame type in the wireless communication system, [2] connection disconnection method between wireless communication apparatuses, [3] access method of wireless LAN system, and [4] wireless LAN frame interval will be described.
[1] Frame types in a communication system Generally, frames handled in a radio access protocol in a radio communication system are roughly classified into three types: a data frame, a management frame, and a control frame. These types are usually indicated by a header portion provided in common between frames. As a display method of the frame type, three types may be distinguished by one field, or may be distinguished by a combination of two fields.

  The management frame is a frame used for managing a physical communication link with another wireless communication apparatus. For example, there are a frame used for setting communication with another wireless communication device, a frame for releasing a communication link (that is, disconnecting), and a frame related to a power saving operation in the wireless communication device. .

  The data frame is a frame for transmitting data generated inside the wireless communication device to the other wireless communication device after establishing a physical communication link with the other wireless communication device. Data is generated in an upper layer of the present embodiment, for example, generated by a user operation.

  The control frame is a frame used for control when a data frame is transmitted / received (exchanged) to / from another wireless communication apparatus. When the wireless communication apparatus receives a data frame or a management frame, the response frame transmitted for confirmation of delivery belongs to the control frame.

  These three types of frames are sent out via the antenna as physical packets through processing as required in the physical layer. In the connection establishment procedure, a connection request frame and a connection acceptance frame are management frames, and a response frame of a control frame can be used as a confirmation frame for the connection acceptance frame.

[2] Methods for disconnecting connections between wireless communication devices There are explicit and implicit methods for disconnecting connections. As an explicit method, one of the connected wireless communication apparatuses transmits a frame for disconnection. This frame is classified as a management frame. The frame for disconnection may be called a release frame in the sense that, for example, the connection is released. Usually, the wireless communication device that transmits the release frame determines that the connection is disconnected when the release frame is transmitted and the wireless communication device that receives the release frame receives the release frame. Thereafter, the process returns to the initial state in the communication phase, for example, the state of searching for the wireless communication device of the communication partner. This is because when a frame for disconnection is transmitted, a physical radio link may not be secured such that a radio signal cannot be received or decoded due to a communication distance away from the connection destination radio communication device. Because.

  On the other hand, as an implicit method, a frame transmission (transmission of a data frame and a management frame, or transmission of a response frame to a frame transmitted by the own device) is detected from a wireless communication device of a connection partner that has established a connection for a certain period of time. If not, it is determined whether the connection is disconnected. There is such a method in the situation where it is determined that the connection is disconnected as described above, such that the communication distance is away from the connection-destination wireless communication device, and the wireless signal cannot be received or decoded. This is because a wireless link cannot be secured. That is, it cannot be expected to receive a release frame.

  As a specific example of determining the disconnection by an implicit method, a timer is used. For example, when transmitting a data frame requesting a delivery confirmation response frame, a first timer that limits the retransmission period of the frame is started (for example, a retransmission timer for a data frame), and until the first timer expires (that is, If a delivery confirmation response frame is not received (until the desired retransmission period elapses), retransmission is performed. The first timer is stopped when a delivery confirmation response frame for the frame is received.

  On the other hand, when the first timer expires without receiving a delivery confirmation response frame, for example, it is confirmed whether the other party's wireless communication device still exists (within the communication range) (in other words, a wireless link has been secured). And a second timer for limiting the retransmission period of the frame (for example, a retransmission timer for the management frame) is started at the same time. Similar to the first timer, the second timer also performs retransmission if it does not receive an acknowledgment frame for that frame until the second timer expires, and determines that the connection has been disconnected when the second timer expires .

  Alternatively, when a frame is received from the connection partner wireless communication device, the third timer is started. Whenever a new frame is received from the connection partner wireless communication device, the third timer is stopped and started again from the initial value. When the third timer expires, a management frame is transmitted to confirm whether the other party's wireless communication device still exists (within the communication range) (in other words, whether the wireless link has been secured) as described above. At the same time, a second timer (for example, a retransmission timer for management frames) that limits the retransmission period of the frame is started. In this case as well, retransmission is performed if a delivery confirmation response frame to the frame is not received until the second timer expires, and it is determined that the connection is disconnected when the second timer expires. The latter management frame for confirming whether the wireless communication apparatus of the connection partner still exists may be different from the management frame in the former case. In the latter case, the same timer as used in the former case is used as the second timer for limiting the retransmission of the management frame. However, a different timer may be used.

[3] Wireless LAN system access method For example, there is a wireless LAN system that is assumed to communicate or compete with a plurality of wireless communication devices. In IEEE802.11 (including extended standards) wireless LANs, CSMA / CA is the basic access method. In the method of grasping the transmission of a certain wireless communication device and performing transmission after a fixed time from the end of the transmission, the transmission is performed simultaneously by a plurality of wireless communication devices grasping the transmission of the wireless communication device, and as a result The radio signal collides and frame transmission fails. By grasping the transmission of a certain wireless communication device and waiting for a random time from the end of the transmission, the transmissions by a plurality of wireless communication devices that grasp the transmission of the wireless communication device are stochastically dispersed. Therefore, if there is one wireless communication device that has drawn the earliest time in the random time, the frame transmission of the wireless communication device is successful, and frame collision can be prevented. Since acquisition of transmission rights is fair among multiple wireless communication devices based on random values, the method employing Carrier Avoidance is a suitable method for sharing wireless media among multiple wireless communication devices. be able to.

[4] Wireless LAN frame interval
The frame interval of IEEE 802.11 wireless LAN will be described. Frame intervals used in IEEE 802.11 wireless LAN are distributed coordination function interframe space (DIFS), arbitration interframe space (AIFS), point coordination function interframe space (PIFS), short interframe space (SIFS), and extended interframe space (EIFS). There are 6 types of reduced interframe space (RIFS).

  In the IEEE802.11 wireless LAN, the frame interval is defined as a continuous period that should be opened after confirming carrier sense idle before transmission, and a strict period from the previous frame is not discussed. Therefore, in the description of the IEEE802.11 wireless LAN system here, the definition follows. In IEEE802.11 wireless LAN, the waiting time for random access based on CSMA / CA is the sum of fixed time and random time, and it can be said that such a definition is used to clarify the fixed time.

  DIFS and AIFS are frame intervals used when attempting to start frame exchange during a contention period competing with other wireless communication devices based on CSMA / CA. DIFS is used when priority according to traffic type (Traffic Identifier: TID) is provided when priority is not distinguished by traffic type.

  Since the operations related to DIFS and AIFS are similar, the following description will be made mainly using AIFS. In the IEEE802.11 wireless LAN, access control including the start of frame exchange is performed at the MAC layer. Further, when QoS (Quality of Service) is supported when data is transferred from an upper layer, the traffic type is notified together with the data, and the priority of the data is classified based on the traffic type. This access class is called an access category (AC). Therefore, an AIFS value is provided for each access category.

  PIFS is a frame interval for enabling access having priority over other competing wireless communication devices, and has a shorter period than either value of DIFS and AIFS. SIFS is a frame interval that can be used when a response control frame is transmitted or when frame exchange is continued in a burst after acquiring the access right. EIFS is a frame interval that is triggered when frame reception fails.

  RIFS is a frame interval that can be used when a plurality of frames are continuously transmitted to the same wireless communication device in bursts after acquiring the access right. While using RIFS, from the wireless communication device of the transmission partner Do not request a response frame.

  Here, FIG. 15 shows an example of a frame exchange during a contention period based on random access in the IEEE802.11 wireless LAN.

  A case is assumed in which when a transmission request for a data frame (W_DATA1) is generated in a certain wireless communication apparatus, the medium is recognized as a busy medium as a result of carrier sense. In this case, a fixed time AIFS is vacated after the carrier sense becomes idle, and then a data frame W_DATA1 is transmitted to the communication partner when a random time (random backoff) is vacant.

  The random time is obtained by multiplying a pseudo-random integer derived from a uniform distribution between contention windows (CW) given by an integer from 0 to a slot time. Here, the CW multiplied by the slot time is called the CW time width. The initial value of CW is given by CWmin, and every time retransmission is performed, the value of CW is increased until it reaches CWmax. Both CWmin and CWmax have values for each access category similar to AIFS. When the wireless communication device as the transmission destination of W_DATA1 succeeds in receiving the data frame, it transmits a response frame (W_ACK1) after SIFS from the reception end time. The wireless communication apparatus that has transmitted W_DATA1 can transmit the next frame (for example, W_DATA2) after SIFS if W_ACK1 is received and within the transmission burst time limit.

  AIFS, DIFS, PIFS, and EIFS are functions of SIFS and slot time. SIFS and slot time are defined for each physical layer. In addition, parameters that have a value for each access category such as AIFS, CWmin, and CWmax can be set for each communication group (Basic Service Set (BSS) in IEEE802.11 wireless LAN), but default values are set. .

  For example, in the 802.11ac standard formulation, SIFS is 16 μs and slot time is 9 μs, so that PIFS is 25 μs, DIFS is 34 μs, AIFS access category is background (AC_BK) frame interval is default value is 79 μs, BEST The default frame interval for EFFORT (AC_BE) is 43 μs, the default frame interval for VIDEO (AC_VI) and VOICE (AC_VO) is 34 μs, and the default values for CWmin and CWmax are 31 and 1023 for AC_BK and AC_BE, respectively. Let AC_VI be 15 and 31, AC_VO be 7 and 15. Note that EIFS is the sum of the time lengths of response frames when transmitting at the slowest required physical rate with SIFS and DIFS.

  The terms used in this embodiment should be interpreted widely. For example, the term “processor” may include general purpose processors, central processing units (CPUs), microprocessors, digital signal processors (DSPs), controllers, microcontrollers, state machines, and the like. In some situations, a “processor” may refer to an application specific integrated circuit, a field programmable gate array (FPGA), a programmable logic circuit (PLD), or the like. The “processor” may refer to a combination of a plurality of processors exemplified here. For example, it may refer to a combination of a DSP and a microprocessor, or a combination of a DSP core and one or more microprocessors.

  As another example, the term “memory” may encompass any electronic component capable of storing electronic information. “Memory” means random access memory (RAM), read only memory (ROM), programmable read only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable PROM (EEPROM), non-volatile It may refer to random access memory (NVRAM), flash memory, magnetic or optical data storage. They can be read and / or written by the processor. At this time, it can be said that electrical communication is performed between the processor and the memory. The memory may be located within the processor, and again, it can be said that the processor and memory are in electrical communication.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

11, 21: Access point (wireless terminal)
12A, 12B, 12C, 12D, 22A, 22B, 22C, 22D: Antenna
1,2,3: Wireless terminal
1A, 2A, 3A: Antenna
31, 32, 33, 34: Transmitted radio wave
101, 201: Control unit
102, 202: Transmitter
103, 203: Receiver
104, 204: Buffer
111, 211: Baseband part
121, 221: RF section
122, 222: Transmitter circuit
123, 223: Receiver circuit
112, 212: Control circuit
113, 213: Transmission processing circuit
114, 214: Reception processing circuit
115, 116, 215, 216: DA conversion circuit
117, 118, 217, 218: AD conversion circuit
301: Notebook PC
305, 315, 355: Wireless communication devices
321: Mobile terminal
331: Memory card
332: Memory card body

Claims (13)

A first field signal including first information designating a first data stream for the first wireless communication terminal and second information designating a second data stream for the second wireless communication terminal, Transmitted through an RF integrated circuit,
An integrated circuit for wireless communication, comprising: a baseband integrated circuit that transmits the first data stream via the RF integrated circuit and does not transmit the second data stream. The baseband integrated circuit includes third information designating a third data stream for the second radio communication terminal and fourth information designating a fourth data stream for the first radio communication terminal. The first field signal is transmitted at the same frequency and at the same time as the transmission of the second field signal by the third wireless communication terminal, and the third data stream is transmitted by the third wireless communication terminal. The integrated circuit for wireless communication according to claim 1, wherein the first data stream is transmitted at the same frequency and at the same time. The baseband integrated circuit includes fifth information representing an indication of time and / or frequency for transmitting the signal of the first field and transmitting the first stream from the third wireless communication terminal or another terminal. The integrated circuit for wireless communication according to claim 2, wherein the first field signal is transmitted according to the fifth information, and the first data stream is transmitted. The baseband integrated circuit receives, from the third wireless communication terminal or another terminal, sixth information specifying a data stream used by the first and second wireless communication terminals, and based on the sixth information, The integrated circuit for wireless communication according to claim 2 or 3, wherein the first field is generated. The integrated circuit for wireless communication according to any one of claims 2 to 4, wherein the signal of the first field is the same as the signal of the second field. The first information and the second information are received by the first wireless communication terminal and the second wireless communication terminal, respectively, on information relating to a group to which the first wireless communication terminal and the second wireless communication terminal belong in common. The integrated circuit for wireless communication according to any one of claims 1 to 5, including information on the number of data streams to be processed. The wireless communication integrated circuit according to any one of claims 1 to 6, further comprising the RF integrated circuit. The integrated circuit for wireless communication according to any one of claims 1 to 7, wherein communication is performed in accordance with the IEEE 802.11 standard. At least one antenna;
A wireless communication unit for transmitting and receiving signals via the antenna;
A signal in a field including first information designating a first data stream to the first radio communication terminal and second information designating a second data stream to the second radio communication terminal is transmitted to the radio A wireless communication terminal comprising: a control unit that transmits via a communication unit, transmits the first data stream via the wireless communication unit, and does not transmit the second data stream. The wireless communication terminal according to claim 9, which communicates according to the IEEE 802.11 standard. The first information and the second information are received by the first wireless communication terminal and the second wireless communication terminal, respectively, on information relating to a group to which the first wireless communication terminal and the second wireless communication terminal belong in common. The wireless communication terminal according to claim 9 or 10, comprising information on the number of data streams to be processed. A first field signal including first information designating a first data stream to the first radio communication terminal and second information designating a second data stream to the second radio communication terminal is transmitted. And steps to
Transmitting the first data stream and not transmitting the second data stream;
A wireless communication method comprising: A third data stream is designated to the second wireless communication terminal at the same time as the time at which the first field is transmitted and at the same frequency as the frequency at which the signal in the first field is transmitted. Transmitting a second field signal including information and fourth information designating a fourth data stream to the first wireless communication terminal;
The third data stream is transmitted at the same time as the time at which the first data stream is transmitted at the same frequency as the frequency at which the first data stream is transmitted, and the fourth data stream is not transmitted. The wireless communication method according to claim 12, further comprising:

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