Communication device and communication method for multi-AP joint transmission

Abstract

The access point (AP) includes a circuit that, during operation, generates a frame including joint transmission (JT) data and a JT identifier that uniquely identifies the JT data. The access point further includes a transmitter that, during operation, transmits the frame to one or more APs that jointly transmit the JT data to a communication device.

Description

Technical Field

[0001] The present disclosure generally relates to communication apparatuses and methods for electronic devices and systems, and more particularly to joint transmission in a multi-AP network.

Background Art

[0002] A wireless network that communicates via multi-AP joint transmission enables communication in a network by joint transmission in which an electronic device is transmitted to a plurality of electronic devices. Such a network has advantages over other wireless networks where wireless communication is limited to a single transmission to one electronic device.

Summary of the Invention

[0003] One non-limiting and exemplary embodiment facilitates providing joint transmission communication in a multi-AP network. For example, this communication includes joint transmission from two or more access points (APs) to one or more wireless stations (STAs).

[0004] In one general aspect, the technology disclosed herein features an access point (AP). The access point includes a circuit that generates a frame including joint transmission (JT) data and a JT identifier that uniquely identifies the JT data during operation, and a transmitter that transmits the frame to one or more other APs that jointly transmit the JT data to a communication device during operation.

[0005] It should be noted that the general or specific embodiments may be implemented as a system, method, integrated circuit, computer program, storage medium, or any selective combination thereof.

[0006] Further benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. The benefits and / or advantages may be individually obtained by the various embodiments and features of the specification and drawings, and these need not all be provided in order to obtain one or more of such benefits and / or advantages.

Brief Description of the Drawings

[0007] Like reference numerals refer to the same or functionally similar elements throughout the different figures, and the accompanying drawings, which are incorporated in and constitute a part of the specification together with the following detailed description, illustrate various embodiments and are useful for explaining the various principles and advantages in accordance with the present embodiments.

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Best Mode for Carrying Out the Invention

[0008] Those skilled in the art will recognize that the elements in the figures are shown for simplicity and clarity and need not be shown to scale. An electronic device can be configured to transmit and receive joint transmission (JT) data in a multi-AP network. These electronic devices have more advantages than conventional electronic devices that are limited to a single transmission to a single electronic device. However, performing joint transmission in a multi-AP network has many technical problems.

[0009] Existing 802.11 BSS (Basic Service Set) operates as a stand-alone unit. The AP of each BSS provides wireless communication services only to the wireless stations (STAs) associated with each AP. The data rate that an AP can provide for a wireless link with an associated STA depends on the MCS (Modulation and Coding Scheme) used for the link, which in turn depends on the SINR (Signal-to-Interference-plus-Noise Ratio) of each STA. Typically, a higher MCS is achievable at a higher SINR, while at a lower level of SINR, only a lower MCS may be possible. In a stand-alone BSS, the signal ratio may be controlled by the AP by adjusting the transmission power, but it is much more difficult to control the interference experienced by the STA. This problem exists at the edge of the network and is particularly applicable to STAs within the wireless range of multiple BSSs (also known as the OBSS (Overlapping BSS) zone). A useful signal in one BSS can be substantially interfering to STAs in other BSSs.

[0010] Multi-AP coordination (e.g., coordination between APs of neighboring BSSs) can be utilized as an effective method for improving the SINR of member STAs. Such a scheme becomes possible by the extensive use of APs, such as in a managed network (e.g., enterprise network, stadium setting, etc.) or a home network (e.g., equipped with a multi-AP home mesh network) with a high density of AP deployments.

[0011] Various multi-AP coordination schemes can be divided into two overall groups. The first group includes schemes that attempt to reduce interference to OBSS through transmission power control, cooperative beamforming, cooperative nullforming, cooperative scheduling, etc. The second group includes schemes that attempt to increase the signal level at the STA through synchronous transmission by multiple APs to the same STA. The schemes of the second group may be known as multi-AP joint processing, multi-AP joint transmission, or distributed MU-MIMO.

[0012] Joint transmission not only improves the signal level but also reduces interference by converting interference signals into desired signals. Thus, exemplary embodiments solve the technical problems related to STAs in overlapping BSSs or multi-AP systems by reducing interference to the STA and improving the SINR for the STA. These problems include methods for distributing and synchronizing joint transmission data (joint MU-MIMO data) among slave APs and other problems considered herein.

[0013] Exemplary embodiments include an apparatus and a method for transmitting and receiving joint transmissions in a multi-AP network. Such an apparatus and method include an electronic device comprising a transmitter and / or a receiver such as an AP and an STA. An example embodiment is a circuit that generates a frame during operation, wherein the frame body of the frame includes joint transmission (JT) data and a JT identifier that uniquely identifies the JT data, and a transmitter that transmits the frame to one or more APs that jointly transmit the JT data to a communication device during operation.

[0014] Another exemplary embodiment is an access point (AP) comprising a receiver that receives a frame including joint transmission (JT) data and a JT identifier that uniquely identifies the JT data from the AP during operation, and a local memory that stores the JT data and the JT identifier.

[0015] Another exemplary embodiment is a communication method in which one or more access points (APs) jointly transmit to a communication device. The method includes transmitting a frame whose frame body includes joint transmission (JT) data and a JT identifier that uniquely identifies the JT data from a first AP to one or more second APs, and jointly transmitting the JT data from the one or more second APs to the communication device.

[0016] FIG. 1 is a wireless network by a multi-AP system 100 according to an exemplary embodiment. For example, system 100 includes three BSSs (shown as BSS1, BSS2, and BSS3). Each BSS has at least one AP (shown as AP1, AP2, and AP3). A plurality of STAs (shown as STA1 to STA5) are distributed throughout the system. STA1 is present in a single BSS (BSS1), STA2 is present in three overlapping BSSs (BSS1 to BSS3), STA3 is present in two overlapping BSSs (BSS1 and BSS3), STA4 is present in two overlapping BSSs (BSS2 and BSS3), and STA5 is present in a single BSS (BSS2).

[0017] In FIG. 1, STA2 is associated with AP3, but the three APs (AP1, AP2, and AP3) may coordinate their transmissions to simultaneously transmit to STA2. This simultaneous transmission increases the SINR level at STA2 and facilitates the use of higher MCSs that translate into higher throughput for STA2.

[0018] Multi-AP coordination schemes typically utilize some level of time synchronization among the participating APs, and the level of synchronization utilized is highest for joint transmission, particularly for distributed MU-MIMO. For this reason, in one or more exemplary embodiments, one AP (referred to as the master AP) provides a synchronization signal and the other participating APs (referred to as slave APs) perform joint transmission within the range of the master AP. In FIG. 1, AP3 is the master AP and AP1 and AP2 are slave APs. The master AP may also be known by other names such as a coordinating AP, a joint transmission (JT) AP, or a multi-AP controller, while the slave AP may be known as a multi-AP device or a coordinated AP, etc.

[0019] In an exemplary embodiment, as will be described in more detail below, joint transmission includes all participating APs that transmit the same signal to the STA. This includes MAC layer specific fields that are equal for all participating APs.

[0020] FIG. 2A shows a multi-AP system 200 shown as a corporate network according to an exemplary embodiment. For example, the system includes a plurality of APs (shown as AP1 to AP8) that announce by overlapping transmissions. Each AP operates on each channel (Ch) such as AP1 on Ch36, AP2 on Ch52, AP3 on Ch149, AP4 on Ch44, AP5 on Ch56, AP6 on Ch161, AP7 on Ch48, AP8 on Ch60, etc.

[0021] In an enterprise network, the location and frequency allocation of APs are carefully planned during deployment to maximize capacity. As shown in FIG. 2A, adjacent APs use non-overlapping channels to minimize inter-BSS interference. The AP can use a high-gain directional antenna with a narrow beam width. Adjacent APs may not be within each other's wireless range. Multiple APs or all APs can utilize the same service set identifier (SSID). Further, the AP may be connected using Ethernet (registered trademark) and be configured and / or controlled by a central AP controller. Most edge STAs are within the coverage of at least two APs. Inter-AP communication can utilize, for example, Ethernet (registered trademark) or an out-of-band mesh wireless direct link. Even if non-overlapping primary channels are assigned to adjacent APs, when wideband channels are utilized, inter-BSS interference in the OBSS zone is inevitable. Since most enterprise networks are centrally managed and cooperation between APs is easier, the enterprise network here is a major candidate for a joint transmission system.

[0022] FIG. 2B shows a multi-AP system 230 shown as a home or office network according to an exemplary embodiment. For example, the system includes multiple APs (shown as AP1 to AP3) that announce by overlapping transmissions. Each AP operates on each channel such as AP1 on Ch36, AP2 on Ch149, and AP3 on Ch52.

[0023] A multi-AP system (e.g., Wi-Fi EasyMesh) is an example of a configuration for providing Wi-Fi coverage across an area such as a home or office. The positions of the APs and the frequency assignments are planned to maximize coverage. For example, one AP may operate as a multi-AP controller while the remaining APs may operate as multi-AP agents. It can be expected that an AP is within the wireless coverage of at least one other AP. A backhaul BSS is set up for signaling between APs. The backhaul BSS may use a different SSID from the fronthaul SSID. Most edge STAs are within the coverage of at least two APs. Additionally, communication between APs can utilize a wireless direct link or a mix of wireless and wired links. Such a multi-AP home or small office network is also a good candidate for a joint transmission system.

[0024] FIG. 2C is a multi-AP system shown as a master-slave configuration according to an exemplary embodiment. For example, the system includes a master AP 270, two slave APs 280, 282, and a STA 284. Communication between the APs is performed via link 290, and communication between the AP and the STA is performed via link 292.

[0025] Regarding joint transmission, an AP holds transmission data (upper layer data) to be jointly transmitted to a STA before actual joint transmission. However, in one or more exemplary embodiments, holding the transmission data may not be sufficient to achieve the SINR gain of joint transmission. The actual data symbols to be wirelessly transmitted need to be synchronized among participating APs such as multiple APs or all APs. This means that the PHY layer and MAC layer processing of the transmission data are the same among the participating APs. Exemplary embodiments include systems, apparatuses, and methods for distributing and synchronizing data for multi-AP joint transmission.

[0026] In one or more exemplary embodiments, joint transmission is performed in two phases, namely, distribution of JT data to the slave AP and joint transmission to the target STA.

[0027] In the first phase (distribution of joint transmission data to the slave AP), the data to be jointly transmitted is distributed to the participating slave APs before actual joint transmission via an inter-AP link such as link 290 in FIG. 2C. The distribution may be performed via a wireless backhaul link between the APs, or alternatively, it may also be performed via a wired backhaul link between the APs, such as Ethernet (registered trademark). When a wireless backhaul is utilized, the slave AP may be associated with the master AP on another BSS configuration by the master AP for communication purposes between the APs before starting the joint transmission. The wireless channel used for the backhaul link between the APs may be different from the fronthaul link between the AP and the target STA.

[0028] In the second phase (joint transmission to the target STA), the actual joint transmission by two or more participating APs to the target STA is performed via a link such as wireless link 292 in FIG. 2C. The joint transmission may be preceded by a synchronization signal from the master AP via link 290, which may be referred to as a Slave Trigger frame or a Joint Transmission (JT) Trigger frame. In some scenarios, the master AP may also participate in the joint transmission, while in some scenarios, the master AP may not participate in the joint transmission and only the slave APs may participate. Different sets of APs may be involved in joint transmission to different target STAs.

[0029] FIG. 3 is a MAC Protocol Data Unit (MPDU) 300 transmitted by a joint transmission according to an exemplary embodiment. The MPDU includes a MAC Header and a Frame Body. The MAC Header includes Frame Control, Duration, Address 1 (Receiver Address), Address 2 (Transmitter Address), Address 3 (BSSID), Sequence Control, QoS Control, and HT Control. The Frame Body includes Data Payload, MIC, and FCS. The Address 3 field carries the BSSID when the Data frame carries an A-MSDU; otherwise, the Address 3 field carries the Source Address (SA), i.e., the MAC address of the device that is the source of the Data Payload.

[0030] To achieve the SINR gain of joint transmission, the actual data symbols transmitted wirelessly are synchronized among the participating APs. Further, the transmission processing of the PHY layer and the MAC layer is the same among the participating APs. Typically, for normal transmission (e.g., non-joint transmission), the upper layer (e.g., the IP layer) passes the data payload to be transmitted (e.g., an IP packet) to the MAC layer. The MAC layer performs MAC layer processing such as prepending the MAC header, adding the FCS, and MAC padding as needed to generate an MPDU (MAC Protocol Data Unit) 300. When protection is enabled, the data payload may further undergo an encryption procedure that adds a CCMP Header field and a MIC field to the MAC frame body. Then, the MPDU is passed to the PHY layer for PHY layer processing such as prepending the PHY preamble, applying PHY encoding, and adding PHY padding to create a PPDU (PHY Protocol Data Unit), and finally the PPDU is transmitted wirelessly.

[0031] For joint transmission, participating APs need to recognize the MAC and PHY parameters applied to the data payload. Further, at the MAC layer, there are several fields generated locally. Some fields such as Frame Control, Address 2 (TA), Address 3 (BSSID), QoS Control, HT Control may be overwritten by the slave AP's MAC layer to match the fields generated by the master AP, while some fields such as Sequence Control, CCMP Header are different for each MPDU and are typically generated locally at each AP. Thus, it is more difficult to synchronize such fields among APs. Also, multiple MPDUs may be aggregated at the MAC layer to form an A-MPDU (Aggregated MPDU), or alternatively, one MPDU may constitute an S-MPDU (Single MPDU). To synchronize the data jointly transmitted among the MAC layers of all participating APs, the master AP may generate the actual MAC layer A-MPDU or S-MPDU and distribute it to all participating slave APs. The Sequence Control field in the MPDU is also generated by the master AP, and the same number space is used for the Sequence Number subfield of the Sequence Control field for both direct transmission from the master AP to the target STA (i.e., single AP transmission) and joint transmission. When encryption is enabled, the master AP also encrypts the Data Payload and adds the MIC field. In this case, the joint transmission (JT) Data refers to the MAC layer data jointly transmitted.

[0032] In some cases, the master AP may not need to participate in the actual joint transmission phase (for example, only the slave APs may participate in the joint transmission). This can happen when the master AP is implemented as a central controller and is far from the target STA. In this case, the target STA is associated with one of the slave APs instead of the master AP.

[0033] In such a case where the target STA is associated with a slave AP, during the data distribution phase, the master AP sets the MAC Header fields of the MPDU 300 so that it appears that the MPDU is generated by the slave AP with which the target STA is associated. For example, the Address 2 (TA) field and the Address 3 (BSSID) are set to the MAC address of the slave AP. The master AP also queries the slave AP for the next Sequence Control to be used, and optionally, the CCMP Packet Number (PN) and the encryption Key ID used for transmission to the target STA, and sets each field of the MPDU 300. The Sequence Control field of the MPDU in this case is generated by the slave AP, and the same number space is used for the Sequence Number subfield of the Sequence Control field for both direct transmission from the slave AP to the target STA (i.e., single AP transmission) and joint transmission.

[0034] Figure 4 is a message sequence 400 in the joint transmission of a multi - AP system according to an exemplary embodiment.

[0035] In a distributed wireless network such as an 802.11 WLAN, access to the wireless channel is controlled by CSMA / CA, and it is difficult to predict the exact transmission time. Similarly, transmission failures and retransmissions make it difficult to maintain the order of transmissions. For this reason, it may be advantageous to separate the data distribution phase and the joint transmission phase for joint transmission.

[0036] As shown in FIG. 4, joint transmission is performed in two phases: distribution of joint transmission data to slave APs and joint transmission to one or more target STAs. In the first phase, one or more joint transmission data (JT Data) are distributed to slave APs (e.g., via a wireless backhaul). A unique ID is assigned to each joint transmission data. In the second phase, the master AP starts joint transmission by transmitting a JT Trigger frame. This frame carries a unique ID that identifies the joint transmission data to be jointly transmitted by all participating APs.

[0037] FIG. 4 shows an exemplary message sequence related to joint transmission in which the data distribution phase 410 is separated from the joint transmission phase 420. During the data distribution phase 410, the master AP distributes one or more joint transmission data (JT Data) to slave APs. The JT Data in this case may be the actual S-MPDU or A-MPDU to be jointly transmitted, or encapsulated in another Data frame addressed to the slave AP. To reduce the overhead of distributing JT Data, the encapsulated Data frame may be transmitted to the slave AP as a multicast transmission instead of a unicast transmission. The master AP may utilize the multi-user (MU) PPDU format to simultaneously distribute different JT Data to different slave APs.

[0038] To uniquely identify each JT Data, the master AP assigns a unique ID, which can be called the JT Packet ID, to each JT Data. When each slave AP receives the encapsulated JT Data, it decrypts and stores the JT Data in the local memory indexed by the JT Packet ID. To ensure that the slave AP stores the JT Data instead of immediately transferring it to the target STA, the RA is set to the MAC address of the slave AP, so that the data frame encapsulating the JT Data can be addressed to the slave AP. When a 4-address MAC Header is used for the data frame to the slave AP, both the RA (Address 1) and the DA (Address 3) can be set to the MAC address of the slave AP. Due to the strict time synchronization requirements for joint transmission and fast extraction, the JT Data frame may be stored in a different memory (e.g., different from the local EDCA queue).

[0039] In the joint transmission phase 420, the master AP starts joint transmission by sending a JT Trigger frame to the slave AP. The JT Trigger frame provides time synchronization to the slave AP. Further, the JT Trigger frame also carries the JT Packet ID of the JT Data to be jointly transmitted. When each slave AP receives the JT Trigger frame, it extracts the JT Data from the local memory corresponding to the JT Packet ID and transmits a JT PPDU composed of the JT Data.

[0040] Figures 5A and 5B are data frames used to encapsulate JT Data according to an exemplary embodiment.

[0041] Figure 5A shows Data frame 500 transmitted by the master AP that encapsulates JT Data, which is an S-MPDU in this case, within the frame body of data frame 500. The S-MPDU is composed of an MPDU Delimiter, the actual MPDU, and padding as required. A unique ID (JT Packet ID) is assigned to each joint transmission data (JT Data). In this case, the JT Packet ID uniquely identifies the S-MPDU.

[0042] Figure 5B shows Data frame 550 transmitted by the master AP that encapsulates JT Data, which is an A-MPDU in this case, within the frame body of data frame 550. The A-MPDU is composed of two or more A-MPDU sub-frames and, if necessary, EOF (End-of-Frame) padding. Each A-MPDU sub-frame shares the same format as the S-MPDU. In this case, the JT Packet ID uniquely identifies the A-MPDU.

[0043] When encryption is enabled, each MPDU in JT Data is also encrypted by the master AP before being encapsulated in Data frame 500 or 550.

[0044] Upon receiving the encapsulated JT Data, each slave AP decrypts and stores the JT Data in local memory indexed by the JT Packet ID. Due to the strict time synchronization requirements for joint transmission, for faster extraction, the JT Data frame may be stored in a different memory (e.g., different from the local EDCA queue).

[0045] The slave AP does not immediately transfer the received JT Data to the target STA. To ensure this, when a 4-address MAC Header is used for the Data frame to the slave AP, both RA (Address 1) and DA (Address 3) are set to the MAC address of the slave AP.

[0046] Figure 6 shows a data frame 600 according to an exemplary embodiment, a first table 610 showing the encoding of the Payload Type field, and a second table 620 showing the encoding of the AP Coodination Packet Type field.

[0047] The Data frame 600 encapsulates JT Data during the data distribution phase (e.g., as described at 410 in FIG. 4). In this example, the frame body of the data frame 600 carries an Ethertype 89-0d frame with a Payload Type field set to 5 “AP Coordination” to distinguish it from other encapsulation types. Ethertype 89-0d is the Ethertype initially assigned for the encapsulation of IEEE 802.11 frames within an Ethernet frame. The Payload of the Ethertype 89-0d frame when the Payload Type is set to “AP Coordination” may carry JT Data within the Packet Content field when the AP Coordination Packet Type field is set to 0, 1, or 2 as shown in Table 620. The Destination MAC Address carries the MAC Address of the target STA (e.g., the target of joint transmission). The JT Packet ID is a unique ID assigned to the JT Data, while the Packet Length field indicates the size of the JT Data carried in the Packet Content field. When the 802.11 Data frame is exclusively used to encapsulate JT Data, the Sequence Number subfield 630 in the Sequence Control field 632 of the host 802.11 data frame may be used as an implicit JT Packet ID, and the JT Packet ID field may be omitted in the Ethertype89-0d frame body.

[0048] To ensure that the slave AP stores the JT Data instead of immediately forwarding it to the target STA, the data frame 600 encapsulating the JT Data is addressed to the slave AP by setting the RA field of the MAC Header to the MAC address of the slave AP. When a 4 - address MAC Header is used, both RA (Address 1) and DA (Address 3) are set to the MAC address of the slave AP.

[0049] Figure 7 shows a joint transmission 700 among a master AP, a slave AP, and a target STA according to an exemplary embodiment.

[0050] In the joint transmission phase (e.g., as described at 420 in FIG. 4), the master AP starts joint transmission by sending a JT Trigger frame 710 to the slave AP. In addition to the PHY and MAC parameters used for synchronization, the JT Trigger frame also carries the JT Packet ID of the JT Data to be jointly transmitted. When the MAC layer of each slave AP receives a JT Trigger frame that identifies the slave AP as an AP participating in joint transmission, it extracts the JT Data from the local memory corresponding to the JT Packet ID and passes it to the PHY layer. The PHY layer constructs a JT PPDU from the JT Data and transmits it after a SIFS (Short Interframe Space) from the end of the JT Trigger frame. The master AP also constructs a JT PPDU from the JT Data corresponding to the JT Packet ID and transmits the JT PPDU after a SIFS from the end of the JT Trigger frame. Since the channel state may be different for different APs, each slave AP may need to transmit the JT PPDU only if it considers the channel state and determines that the channel is idle during the SIFS after the end of the JT Trigger frame. However, the NAV (Network Allocation Vector) set due to the transmission of the master AP or the target STA may be ignored. Regarding the target STA, when receiving the JT Data, it may not even notice that multiple APs were involved in the transmission. As far as the target STA is concerned, this is just another transmission to it from the master AP, or an AP whose MAC Address appears in the TA Address (Address 2) field of the frame. If the reception is successful, the target STA sends an acknowledgment frame (ACK or Block Ack) to the AP whose MAC Address appears in the TA Address (Address 2) field.

[0051] Figure 8 is a JT Trigger frame 800 according to an exemplary embodiment. Each User Info field carries information for a set of a slave AP and a target STA.

[0052] The MAC Address of Slave APs field identifies the slave APs participating in joint transmission for a particular set of STAs. If only a single slave AP is involved in joint transmission, this may be omitted and the slave AP is identified by the RA field in the MAC Header. The AID12 field within each User Info field may be set to a special value (e.g., 2047) to distinguish the JT Trigger frame from other Trigger frames used to request uplink OFDMA transmission.

[0053] The JT Packet ID field identifies the (stored) MPDU carried in the JT PPDU. In the case of an S-MPDU, this may be the value of the Sequence Control field of the S-MPDU. If the same data is jointly transmitted (transmission diversity), the field value may be the same for different slave APs. Alternatively, if different data is jointly transmitted (D-MIMO), the field value may be different for different slave APs.

[0054] Furthermore, Joint Transmission PHY Layer Info specifies additional PHY parameters used for encoding of the JT PPDU. Target STA Information carries information related to joint transmission by the slave AP to one or more target STAs. Joint Transmission Information identifies the stored data to be transmitted and the spatial streams for the target STAs.

[0055] Furthermore, the Spatial Stream Allocation field indicates the spatial streams allocated to each target STA and exists only in the case of MIMO joint transmission. The Starting Spatial Stream field indicates the first spatial stream allocated to the STA, and the Number of Spatial Stream field indicates the total number of consecutive spatial streams including the first spatial stream allocated to the STA.

[0056] Figure 9 is a message sequence 900 for a joint transmission session between a master AP and a slave AP in a multi-AP system according to an exemplary embodiment.

[0057] If joint transmission is expected to be performed for two or more frames, the exemplary embodiment sets up a joint transmission session between the master AP and the participating slave APs before the actual joint transmission. During the joint transmission session negotiation, the master AP and the slave APs exchange information about the target STAs involved in the joint transmission. The master AP and the slave APs also specify joint transmission parameters expected to be used throughout the session, such as the channel to be used, the PPDU format (such as HT, VHT, or HE), the precoding scheme for MU-MIMO, etc. Each joint transmission session is identified by a unique Session ID. The master AP starts the setup of the joint transmission session by sending an AP Coordination Session Request frame to the slave AP. If the slave AP accepts the request, it sends back an AP Coordination Session Response frame with the Status Code field set to Accept to the master AP. The master AP repeats this process for each slave AP participating in the joint transmission. To end the session, the master AP sends an AP Coordination Session Teardown frame to the slave AP.

[0058] Figure 10 shows an AP Coordination Action frame exchanged between APs to negotiate or tear down an exemplary joint transmission session. The figure shows an AP Coordination Session Request 1000, an AP Coordination Session Response 1002, an AP Coordination Session Teardown 1004, a table 1010 with AP Coordination Session Action field values, and a table 1020 with AP Coordination Type field values.

[0059] A new category of Action frames is defined for multi-AP coordination and is indicated in the Category field. Five new Action frames are defined for the purpose of inter-AP communication related to multi-AP coordination, three of which are used for session setup / teardown (indicated by the values of the "AP Coordination Session Action" field listed in table 1010). Sessions are set up for various types of multi-AP coordination schemes and are indicated by the values of the "AP Coordination Type" field in the AP Coordination Session Request frame listed in table 1020. For example, for a joint transmission session, it is set to 2. The "Target STA information" field in the AP Coordination Session Request frame 1000 lists the MAC Addresses of one or more target STAs expected to participate in the joint transmission.

[0060] The "Type Specific parameters" field in the AP Coordination Session Request frame 1000 carries additional session parameters specific to the AP Coordination Type. For example, for Joint Transmission, this field may specify the Channel information for joint transmission. The Channel information may exist when the master AP and the slave AP are operating on different front-haul channels. The "Type Specific parameters" field may also indicate the start time at which joint transmission is expected to begin. In a high-density network, it is common for neighboring APs to operate on different channels to reduce inter-BSS interference. If the channel specified by the Channel information is different from the operating channel of the slave AP and the slave AP accepts the AP Coordination Session Reqeust, the slave AP is expected to switch channels to the specified joint transmission channel before the indicated joint transmission start time.

[0061] As another example, for Joint Transmission, if encryption is enabled for joint transmission and is executed locally at each AP, the "Type Specific parameters" field may also include the security key (e.g., PTK) used for encryption.

[0062] As yet another example, for Joint Transmission, the "Type Specific parameters" field may also include the size of the buffer space requested by the master AP to be allocated by the slave AP for storing JT Data frames.

[0063] Figure 11 shows frame 1100 in which an Ethernet frame encapsulates an AP Coordination Action frame together with JT Data according to an exemplary embodiment.

[0064] The master AP encapsulates a Joint Transmission Data frame (the entire S-MPDU or A-MPDU carrying the Joint Transmission Data payload) within an 802.3 (Ethernet) frame and transmits it to the slave AP via the Ethernet (registered trademark) link. If encryption is used, the encrypted frame is encapsulated.

[0065] When an Ethernet frame is used to exchange AP Coordination information between APs, Ethertype 89-0d may also be used to encapsulate an AP Coordination Action frame, for example, to set up or tear down an AP coordination session. In this case, the Payload Type field is set to "AP Coordination", and the payload of the Ethertype 89-0d frame carries the AP Coordination Action frame. The "AP Coordination Packet Type" field in this case is set to the AP Coordination Action frame (set to 3 as shown in table 620 of figure 6), the Packet Content field carries the AP Coordination Action frame, while other fields in the payload are omitted.

[0066] The Destination Address in the MAC Header ensures that the slave AP does not immediately forward the received JT Data frame to the target STA. For example, the subfield is set to the MAC address of the slave AP and not to the MAC address of the target STA.

[0067] Transmissions to different slave APs may not be temporally synchronized in a wired or hybrid backhaul scenario and may be performed simultaneously or at different times. The JT Packet ID is used to synchronize the content of Joint Transmission.

[0068] FIG. 12 shows a Trigger frame 1200 for joint transmission to a target STA according to an exemplary embodiment.

[0069] The Joint Transmission Trigger frame 1200 includes an AP Coordination Session ID 1210. The session ID is included in the JT Trigger frame to indicate which joint transmission session is being triggered. Based on the session ID, the slave AP that receives the JT Trigger frame extracts the common parameters negotiated during session setup. Such pre-negotiated parameters are omitted in the JT Trigger frame if the master AP does not explicitly override any of the parameters. The overhead of joint transmission control signaling over the wireless medium is reduced.

[0070] Furthermore, if all slave APs corresponding to the Session ID are participating in the joint transmission, the MAC Address field of the slave AP can be skipped. The Destination MAC Address field may also be omitted if the target STA is obvious from the Session ID.

[0071] FIG. 13 shows a communication interaction 1300 in which the master AP does not participate in joint transmission according to an exemplary embodiment.

[0072] As described above, in some cases, the master AP may not need to participate in the actual joint transmission phase, and only the slave APs may participate in the joint transmission. This can be done when the master AP is implemented as a central controller and is far from the target STA, or when the master AP is not even an actual AP but a multi-AP controller device in the core network. In this case, the target STA is associated with one of the slave APs instead of the master AP. The communication between the slave AP and the master AP including the JT Trigger frame may be performed via a wired backhaul (e.g., Ethernet (R)). When there is no wireless link between the master AP and the slave AP, even the JT Trigger frame is encapsulated within an Ethernet frame. Due to the strict time synchronization requirements for joint transmission and the fact that the JT Trigger frame is used for time synchronization between slave APs, the use of a wired backhaul for the transmission of the JT Trigger frame is possible only when it is guaranteed that all participating slave APs can receive the JT Trigger frame simultaneously. In this case, the Payload Type field is set to "AP Coordination", and the payload of the Ethertype 89-0d frame carries the JT Trigger frame. The "AP Coordination Packet Type" field in this case is set to the JT Trigger frame (set to 4 as shown in Table 620 of FIG. 6), the Packet Content field carries the JT Trigger frame, while other fields in the payload are omitted. This type of deployment removes the constraint that the slave APs need to be within the wireless range of the master AP, enables joint transmission on a much larger scale, and allows the master AP at a centralized location to remotely manage joint transmission at multiple physical locations. However, if it cannot be guaranteed that all participating slave APs can receive the JT Trigger frame simultaneously, the JT Trigger frame is transmitted via the wireless medium.

[0073] If the target STA is not associated with the master AP, the master AP may not know the value used for the Sequence Control field or the CCMP Packet Number (PN) locally generated by the slave AP. For example, if the target STA is associated with slave AP1, before the data distribution phase 1320, the master AP starts the information query phase 1310 and then queries slave AP1 for the Sequence Control to be used next, and optionally the CCMP Packet Number (PN) and the encryption key ID used for transmission to the target STA. When the entire MPDU is distributed to the slave AP, the master AP uses the queried information to set each field of the encapsulated JT Data, or if the MPDU for joint transmission is locally generated by the slave AP, the information is distributed to the slave AP.

[0074] At some point before the data distribution phase 1320, the master AP also configures the upper layer data to be routed through itself instead of through slave AP1. This may be done by temporarily updating the routing table of the network router device that transfers the data payload to the AP so that the master AP is recorded as the service AP for the target STA.

[0075] During the data distribution phase 1320, the master AP sets the MAC Header field of the encapsulated JT Data so that it appears that the data is generated by the slave AP1 associated with the target STA. For example, the Address 2 (TA) field of the jointly transmitted MPDU is set to the MAC address of the slave AP1. Also, the Sequence Number subfield of the Sequence Control field of the (JT Data) MPDU is used as an implicit JT Identifier, and an explicit JT Packet ID is not assigned to the JT Data. During the joint transmission phase 1330, the master AP still initiates the joint transmission by sending a JT Trigger frame, but only the slave AP participates in the actual joint transmission. To the target STA, the transmission appears to be initiated by the slave AP1.

[0076] Figure 14 shows an Action frame 1400 used by an AP in an information query phase to collect information from another AP according to an exemplary embodiment.

[0077] The AP Coordination Info Request frame includes a Requested Information bitmap indicating information about slave AP parameters for the target STA requested by the master AP. The slave AP uses the AP Coordination Info Response frame to report the requested information to the master AP, and the information included is indicated by the Reported Information bitmap.

[0078] The master AP can start the request, but the slave AP can also start the request. The AP Coordination Info Request frame 1410 includes a Requested Information bitmap indicating information about the parameters of the receiving AP for the target STA requested by the transmitting AP. The receiving AP uses the AP Coordination Info Response frame 1420 to report the requested information to the requesting AP, and the information fields included are indicated by the Reported Information bitmap. If a bit is set to 1 in the Reported Information bitmap, the corresponding field is included in the AP Coordination Info Response frame 1420; otherwise, it does not exist.

[0079] Figure 15 shows a frame 1500 for data sharing from a master AP to a slave AP according to an exemplary embodiment.

[0080] Instead of encapsulating the entire MAC layer frame (MPDU or A-MPDU), the master AP only encapsulates the upper layer data payload (also known as MSDU (MAC Service Data Unit)) and other related fields of the MAC header within the Payload field of the Ethertype 89-0d frame body. If multiple data payloads are included, the Sequence Control field and the CCMP Header (if included) carry the starting Sequence Number (SN) and Packet Number (PN) respectively. Based on this, each slave AP generates the jointly transmitted MPDU or A-MPDU. If required, data encryption is performed by each slave AP.

[0081] Copies of the Frame Control, Duration / ID, QoS Control, and HT Control fields are utilized by the slave AP to generate the MAC Header of the locally generated MPDU. Alternatively, some or all of these fields may also be assigned during JT session setup if these fields remain the same throughout the JT session.

[0082] When the "Protected Frame" bit in the Frame Control field 1520 is set, the CCMP Header field 1510 is present. The CCMP Header field 1510 carries the Packet Number (PN) that is used to encrypt the first MPDU by subsequent MPDUs using sequentially increasing PNs.

[0083] The Sequence Control field 1520 carries the Sequence Number (SN) used for locally created A-MPDUs. This is used as the start SN for the first MPDU and sequentially increases for subsequent MPDUs in the A-MPDU.

[0084] The Packet Content field 1530 carries only the upper layer payload (also known as the MSDU). Each slave AP adds the locally generated MAC header to the upper layer payload to generate the MPDU for joint transmission.

[0085] FIG. 16 shows a JT Data frame 1600 as an Aggregated MAC Protocol Data Unit (A-MPDU) according to an exemplary embodiment.

[0086] Each slave AP locally generates a Joint Transmission Data frame 1600 and stores it in the memory. For example, each slave AP generates a jointly transmitted MPDU or A-MPDU based on the information 1602 received from the master AP. The arrows in FIG. 16 mean that fields are simply copied to the locally generated MPDU, except for some fields that require addition. The initially generated MPDU directly uses the Sequence Control field received from the master AP, while each subsequent MPDU increments the Sequence Number subfield in the Sequence Control field 1620 by one. The MPDU or A-MPDU may be generated as soon as the encapsulated data is received from the master AP and stored in the memory. If encryption is required (indicated by the "Protected Frame" bit in the Frame Control field 1610), each slave AP also encrypts the data payload, generates an MIC, and adds it to the payload. The initially encrypted MPDU directly uses the CCMP Header field received from the master AP, while each subsequent MPDU increments the PN subfield in the CCMP Header field by one. The encrypted MPDU is stored in the memory and indexed by the JT Packet ID 1630.

[0087] Alternatively, if the slave AP has a fast enough processor, during the data distribution phase, the received MAC parameters and payload may be stored in the memory, and the generation of the MPDU (and encryption if necessary) may be performed only after the reception of the JT Trigger frame.

[0088] In FIG. 16, the Address 2 (TA) field 1622 in the MPDU of the JT Data frame 1600 created locally is also copied from the corresponding Address 2 (TA) field 1630 in the information 1602 received from the master AP. The Address 2 (TA) field 1630 is set to one of the MAC address of the master AP or the MAC address of the slave AP according to the AP to which the target STA is associated. The remaining fields (MPDU delimiter, Padding, FCS, etc.) of each A-MPDU subframe are generated locally together with the EOF padding. Further, in the CCMP Encryption frame, when the "Protected Frame" bit in the Frame Control field 1610 is set, CCMP encryption is performed by the slave AP.

[0089] One advantage of the frame 1600 is that the overhead of data transfer via the backhaul is reduced.

[0090] FIG. 17 shows a frame 1700 as an Aggregated MAC Protocol Data Unit (A-MPDU) used for data sharing with a slave AP according to an exemplary embodiment.

[0091] The master AP distributes JT Data to the slave AP using an 802.11 Data frame 1700 in the 4 Address MAC Header format (without using the encapsulation of Ethertype 89-0d). This distribution scheme may be used, for example, when the slave AP is associated with the master AP in a Wi-Fi EasyMesh deployment.

[0092] When the slave AP receives joint transmission data from the master AP, it generates MPDUs to be jointly transmitted. The Sequence Number within the Sequence Control field 1734 in the MAC header of the generated MPDU is used as implicit JT Identifiers.

[0093] Consider an example of a deployment where the target STA is associated with the master AP and the master AP also participates in actual joint transmission. The master AP transmits the A-MDPU 1700 to the slave AP and distributes the JT Data. Each Data frame within the MPDU of the A-MPDU uses the 4-address MAC Header format, and the Frame Body of the MPDU 1710 carries the actual Data Payload 1720 to be jointly transmitted (optionally encrypted and including the CCMP Header field and the MIC field). In this case, the JT Data refers to the Data Payload 1720 (optionally encrypted and including the CCMP Header field and the MIC field). Since the final destination of the Data Payload 1720 is not the slave AP, both the "To DS" and "From DS" bits in the Frame Control field 1712 are set to 1 to distinguish between transmissions from the AP to the STA or from the STA to the AP. The HE Control field 1714 is also extended for the use of EHT, and new Control IDs are defined for AP coordination. The Control field may be used to carry control signals for various multi-AP coordination schemes, and the AP Coordination Type 1716 indicating the coordination scheme may be set to 2 for joint transmission where the subsequent field of the HE Control field is used to carry the JT Sequence Control 1718. The JT Sequence Control field 1718 carries the Sequence Control field 1734 of the actual MPDU to be jointly transmitted.

[0094] When the master AP receives an A-MPDU 1710 that carries the HE Control field 1714 for AP coordination, the addressed slave AP (indicated by Address 1 (RA)) generates an MPDU or A-MPDU to be jointly transmitted based on the information received from the master AP, instead of forwarding the A-MPDU to the target STA (indicated by Address 3 (DA)). The generated MPDU 1730 is an 802.11 Data frame that uses the 3-address MAC Header format.

[0095] In FIG. 17, the arrows indicate that fields are copied from the received MPDU to the generated MPDU, except that in the generated MPDU, the “To DS” bit in the Frame Control field 1732 is set to 0 and the “From DS” bit is set to 1. The Sequence Control field 1734 of the generated MPDU is copied from the JT Sequence Control 1718 received from the master AP. The Duration field, Address 2 (TA) field, and QoS Control field are copied without being changed. On the other hand, the Address 3 (DA) field is copied to the Address 1 (RA) field, and the Address 4 (SA) field is copied to the Address 3 (SA) field in the generated MPDU. The HE Control field that carries the JT Sequence Control field is omitted in the generated MPDU. The frame body of the generated MPDU is copied directly from the MPDU 1710 received from the master AP (i.e., without further processing). However, the FCS field 1738 is locally generated by the slave AP. When the Data Payload 1720 is encrypted, an important aspect to note here is that CCMP encryption is performed for use at the target STA, and thus the MAC header parameters used for encryption are based on the MAC header fields included in the actual MPDU 1730 that is jointly transmitted, rather than based on the MAC Header field of the MPDU 1710. Specifically, in the CCMP encapsulation procedure, the master AP uses the Frame Control field 1732, Address 1 (RA) field 1740, Address 2 (TA) field 1742, Address 3 (SA) field 1744, Sequence Control field 1746, and QoS Control field 1748 to construct the additional authentication data (AAD) used for CCMP encryption as if it were generated by the slave AP. The Address 4 field is not included in the AAD.The CCMP Header field, the encrypted Data Payload1720, and the generated MIC are included in the frame body of MPDU1710 and are directly copied by the slave AP into the frame body of MPDU1730 without further processing. This significantly reduces the processing overhead associated with the encryption of the slave AP.

[0096] An MPDU or A-MPDU may be generated immediately by the slave AP in response to the reception of data from the master AP and stored in memory. The MPDU is stored in memory indexed by the Sequence Number subfield of the Sequence Control field 1734. Alternatively, if the slave AP has a fast enough processor, during the data distribution phase, the received MPDU / A-MPDU may be stored in memory unchanged, and the generation of MPDUs (for joint transmission) may be performed only after the JT Trigger frame has been received.

[0097] Figure 18 shows a Joint Transmission Trigger frame 1800 according to an exemplary embodiment.

[0098] The JT Trigger frame includes a list of Sequence Numbers of the MPDUs to be jointly transmitted. The slave AP constructs an A-MPDU from the stored MPDUs as needed.

[0099] For example, the Sequence Number subfield in the Sequence Control field of an MPDU (JT Data), such as 1620 in FIG. 16 or 1732 in FIG. 17, is used as an implicit JT Identifier. This allows for greater flexibility in selecting the content of the JT Data during actual joint transmission by the master AP (by indicating specific sequence numbers in the Sequence Number Information field 1810 of the JT Trigger frame 1800).

[0100] This flexibility can be implemented, for example, during joint retransmission where only the failed MPDUs are retransmitted. The Sequence Number Information field 1810 identifies the MPDUs to be jointly transmitted. Bits set to 1 in the Sequence Number Bitmap subfield indicate the sequence numbers of the included MPDUs, with the first bit (n = 1) corresponding to the Starting Sequence Number (SSN) subfield and the nth bit corresponding to (SSN + n - 1).

[0101] FIG. 19 is an example of distributed MU-MIMO Joint Transmission 1900 for two STAs both associated with a master AP according to an exemplary embodiment.

[0102] References 1910 and 1912 indicate data distribution to slave APs. JT Data is distributed to the slave APs destined for STA1 and STA2 respectively. For example, JT Data 1910 and 1912 may be A-MPDU 1700 in FIG. 17. Upon receiving JT data 1910 and 1920, the slave AP may generate MPDU 1730 for joint transmission by copying the necessary fields from the received JT Data. The slave AP may further aggregate locally generated MPDUs into a single A-MPDU and store the A-MPDU in a specified local buffer. Reference 1914 indicates a Joint Transmission Trigger frame used to initiate joint transmission to the target STA. JT Trigger frame 1914 initiates MU joint transmission using two spatial streams. Reference 1920 indicates joint transmission to STA1 (using Spatial Stream 1 to send S.N 1 - 5 to STA1). Reference 1922 indicates joint transmission to STA2 (using Spatial Stream 2 to send S.N 11 - 15 to STA2). References 1920 and 1922 occur simultaneously but use different spatial streams.

[0103] Figure 20 is an example of an electronic device 2000 according to an exemplary embodiment.

[0104] The electronic device 2000 includes a power supply 2010, a memory 2020, a central processing unit (CPU) 2030, a secondary storage device 2040, and a wireless I / F 2050 (including a transmitter and / or a receiver). The wireless I / F 2050 includes a MAC 2052 and a PHY 2060 that communicate with an antenna 2070. The MAC 2052 further includes a JT Identity generator 2054, a JT Data buffer 2056, and a JT Data encapsulation / de-encapsulation 2058.

[0105] Consider an exemplary embodiment where the electronic device 2000 is an AP such as a master AP or a slave AP (note that the JT Identity generator 2054 only exists in the master AP).

[0106] The electronic device 2000 includes a circuit that operates to generate a frame including JT Data and a JT Identity that uniquely identifies the JT Data. For example, the JT Identity generator 2054 is responsible for generating a JT Identity corresponding to the JT Data distributed to the slave AP. The JT Data encapsulation / decapsulation block 2058 is used by the master AP to encapsulate the JT Data within an 802.11 Data frame or an 802.3 Ethernet frame during the data distribution phase. This block is used by the slave AP to decapsulate the JT Data received from the master AP. The JT Data buffer 2056 stores the JT Data used for joint transmission. In the master AP, this may be a shared buffer that stores all output data frames rather than a separate buffer. In the slave AP, this may be a separate buffer that is only used to store the data frames used for joint transmission. The electronic device 2000 further includes a circuit such as a wireless transmitter and / or antenna 2070 that enables the AP to transmit data frames to one or more communication devices such as one or more STAs in a wireless network.

[0107] The present disclosure can be implemented by software, hardware, or software in conjunction with hardware. Each functional block used in the description of each of the above-described embodiments can be partially or entirely realized by an LSI such as an integrated circuit, and each process described in each embodiment may be partially or entirely controlled by the same LSI or a combination of LSIs. The LSI may be formed as an individual chip, or one chip may be formed to include part or all of the functional blocks. The LSI may include data input / output coupled thereto. Here, the LSI can be called an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. However, the technology for realizing the integrated circuit is not limited to the LSI, and it may be realized using an application-specific circuit, a general-purpose processor, or an application-specific processor. Further, an FPGA (Field Programmable Gate Array) that can be programmed after manufacturing an LSI or a reconfigurable processor in which the connection and setting of circuit cells arranged inside the LSI are reconfigurable may be used. The present disclosure can be realized as digital processing or analog processing. As a result of the progress of semiconductor technology and other derivative technologies, when future integrated circuit technology replaces the LSI, the functional blocks can be integrated using future integrated circuit technology. Biotechnology can also be applied.

[0108] The present disclosure can be implemented by any type of device, apparatus, or system having a communication function, referred to as a communication device.

[0109] The communication device may have a transceiver and a processing / control circuit. The transceiver may include and / or function as a receiver and a transmitter. The transceiver such as the transmitter and the receiver may include an RF module including an amplifier, an RF (Radio Frequency) modulator / demodulator, etc., and one or more antennas.

[0110] Some non-limiting examples of such communication devices include telephones (e.g., mobile (cell) phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, netbooks), cameras (e.g., digital still / video cameras), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smartwatches, tracking devices), game consoles, digital book readers, remote health / telemedicine devices, and vehicles that provide communication capabilities (e.g., automobiles, airplanes, ships), as well as various combinations thereof.

[0111] The communication device is not limited to being portable or mobile, and may include any type of device, apparatus or system that is non-portable or fixed, such as smart home devices (e.g., home appliances, lighting, smart meters, control panels), vending machines, and any other "things" in a network of the "Internet of Things (IoT)".

[0112] Communication may include, for example, exchanging data via cellular systems, wireless LAN systems, satellite systems, etc., and various combinations thereof.

[0113] The communication device may also include a device such as a controller or sensor coupled to a communication device that performs the communication functions described in the present disclosure. For example, the communication device may include a controller or sensor that generates a control signal or data signal used by a communication device that performs the communication functions of the communication device.

[0114] The communication device may also include an infrastructure facility such as a base station, access point, and any other device, apparatus or system that communicates or controls with a device such as those in the above non-limiting examples.

[0115] Although some features of the various embodiments have been described with reference to the device, it will be understood that the corresponding features also apply to the methods of the various embodiments, and vice versa.

[0116] Those skilled in the art will understand that numerous variations and / or modifications can be made to the present disclosure as shown in the specific embodiments without departing from the spirit or scope of the present disclosure as broadly described. Accordingly, the present embodiments should be considered illustrative in all respects and not restrictive.

[0117] Other exemplary embodiments include, but are not limited to, the following specific examples.

[0118] One example embodiment is an access point (AP) having a circuit that generates a frame during operation, the frame body of the frame including joint transmission (JT) data and a JT identifier that uniquely identifies the JT data, and a transmitter that transmits the frame to one or more APs that jointly transmit the JT data to a communication device during operation.

[0119] According to the access point, the circuit generates a JT trigger frame that includes the JT identifier of the JT data during operation, and the transmitter transmits the JT trigger frame to one or more APs during operation.

[0120] According to the access point, the JT trigger frame includes the MAC address of the communication device.

[0121] According to the access point, the JT data is carried as the payload of an Ethertype 89-0d frame body.

[0122] According to the access point, the frame is one of an IEEE 802.11 data frame and an Ethernet frame.

[0123] According to the access point, JT data is one or more MAC protocol data units (MPDUs) addressed to a communication device.

[0124] According to the access point, the JT identifier is one of a uniquely assigned JT packet ID, the value of the Sequence Number subfield within the Sequence Control field of an encapsulated IEEE 802.11 data frame, and the value of the Sequence Number subfield within the Sequence Control field of an MPDU within JT Data.

[0125] According to the access point, JT data locally constructs one or more MAC protocol data units (MPDUs) jointly transmitted to a communication device, and has fields common to the upper layer payload required by the receiving AP.

[0126] According to the access point, JT data is carried as the payload of an IEEE 802.11 Data frame using a 4-address MAC header format. The MAC header of the IEEE 802.11 Data frame includes a control field indicating the Sequence Control field of the jointly transmitted IEEE 802.11 Data frame, and the JT identifier includes the value of the Sequence Number subfield within the Sequence Control field.

[0127] According to the access point, the access point negotiates an AP cooperation session with one or more APs. The AP cooperation session designates an AP cooperation scheme as joint transmission, and the AP cooperation session is identified by a session ID.

[0128] According to the access point, the access point transmits a PHY protocol data unit (PPDU) composed of JT data after a fixed time from the end of the JT trigger frame.

[0129] Another example of an embodiment is an access point (AP) having a receiver that receives, from an AP, a frame including joint transmission (JT) data and a JT identifier that uniquely identifies the JT data during operation, and a local memory that stores the JT data and the JT identifier.

[0130] According to the access point, the receiver is further operative to receive, from the AP, a JT trigger frame carrying the JT identifier of the JT data, and the access point extracts the JT data having a matching JT identifier from the memory and transmits a physical layer protocol data unit (PPDU) composed of the JT data after a fixed time from the end of the JT trigger frame.

[0131] Another example of an embodiment is a communication method in which one or more access points (APs) perform joint transmission to a communication device. The method includes transmitting, from a first AP to one or more second APs, a frame in which a frame body includes joint transmission (JT) data and a JT identifier that uniquely identifies the JT data, and jointly transmitting the JT data to the communication device from the one or more second APs.

[0132] The method further includes synchronizing PHY and MAC parameters in two or more transmitting APs so that transmission signals received by the communication device from the two or more transmitting APs are exactly the same.

Claims

1. A circuit that generates a frame including encapsulating joint transmission (JT) data during operation and the encapsulated JT data and a JT identifier that uniquely identifies the encapsulated JT data; A transmitter that transmits the frame to one or more other APs that jointly transmit the JT data to a communication device during operation; The encapsulated JT data and the JT identifier in the JT packet ID field are included in separate fields of the frame; The JT data is one or more MAC protocol data units (MPDUs) addressed to the communication device, and the MPDU includes a sequence number different from the JT identifier; An access point (AP).

2. The circuit generates a JT trigger frame including the JT identifier of the JT data during operation, and the transmitter transmits the JT trigger frame to the one or more other APs during operation. The access point according to claim 1.

3. The JT trigger frame includes the MAC address of the communication device. The access point according to claim 2.

4. The JT data is carried as the payload of an Ethernet type 89-0d frame body. The access point according to claim 1.

5. The frame is one of an IEEE 802.11 data frame and an Ethernet frame. The access point according to claim 1.

6. The JT identifier is a uniquely assigned JT packet ID. The access point according to claim 1.

7. JT data has a field common to the upper layer payload required by the receiving AP in order to locally configure one or more MAC protocol data units (MPDUs) jointly transmitted to the communication device. The access point according to claim 1.

8. The JT data is carried as the payload of an IEEE 802.11 Data frame using a 4-address MAC header format, and the MAC header of the IEEE 802.11 Data frame includes a control field indicating the Sequence Control field of the jointly transmitted IEEE 802.11 Data frame. The JT identifier includes the value of the Sequence Number subfield within the Sequence Control field. The access point according to claim 1.

9. The access point negotiates an AP cooperation session with the one or more other APs, the AP cooperation session designates an AP cooperation scheme as joint transmission, and the AP cooperation session is identified by a session ID. The access point according to claim 1.

10. The access point transmits a PHY protocol data unit (PPDU) composed of the JT data after a fixed time from the end of the JT trigger frame. The access point according to claim 1.

11. In a first access point (AP), a step of generating a frame including encapsulated joint transmission (JT) data and a JT identifier that uniquely identifies the encapsulated JT data; A step of transmitting the frame from the first AP to one or more second APs that jointly transmit the JT data to a communication device; The encapsulated JT data and the JT identifier in the JT packet ID field are included in separate fields of the frame; The JT data is one or more MAC protocol data units (MPDUs) addressed to the communication device, and the MPDU includes a sequence number different from the JT identifier. Communication method.

12. The communication method according to claim 11, further comprising a step of synchronizing PHY and MAC parameters in the one or more APs such that the JT data received by the communication device from the one or more APs is exactly the same.

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