Communication device, control method, and program

Abstract

This communication device functioning as an access point (AP) conforming to the IEEE 802.11 series standard: receives, from another AP, a roaming request without re-association of a station (STA) connected to yet another AP; determines an association identifier (AID) of the STA on the basis of the reception of the request; determines whether to notify the STA of the AID from any of the AP and the other AP; when notifying the STA of the AID from the other AP, notifies the other AP of the AID and an instruction indicating that the AID should be transmitted from the other AP; and notifies the STA of the AID when notifying the STA of the AID from the AP.

Description

Communication device, control method, and program

[0001] The present disclosure relates to a roaming control technique in a wireless LAN.

[0002] The IEEE 802.11 series of standards is known as a communication standard for wireless LANs (Local Area Networks). Here, IEEE stands for Institute of Electrical and Electronics Engineers. Among the IEEE 802.11 series of standards, the IEEE 802.11be standard and its successor, the IEEE 802.11bn standard, are studying methods for reducing communication delays and improving channel utilization efficiency. Patent Document 1 describes a wireless link reconfiguration procedure when a station (STA) roams between physically separate access points (APs).

[0003] US Patent Application Publication No. 2023 / 0380001

[0004] Seamless roaming technology has been studied as a technology for shortening communication interruption periods due to roaming for efficient communication by STAs. This technology eliminates the need for processing such as a four-way handshake between the STA and the roaming AP, thereby shortening communication interruption periods. On the other hand, when roaming is performed, the AP that manages the AID (Association Identifier) ​​is changed, but a method for appropriately setting or managing this AID in seamless roaming has not been studied.

[0005] The present disclosure provides a method for appropriately setting or managing AID when seamless roaming is performed.

[0006] A communication device according to one aspect of the present disclosure functions as an access point (AP) compliant with the IEEE 802.11 series standard, and includes: a receiving means for receiving, from another AP, a roaming request that does not involve reassociation of a station (STA) connected to the other AP; a determining means for determining an association identifier (AID) of the STA based on the received request, and determining whether the AP or the other AP will notify the STA of the AID; and a notifying means for, when notifying the STA from the other AP of the AID, notifying the other AP of the AID and an instruction indicating that the AID should be transmitted from the other AP, and when notifying the STA of the AID from the AP.

[0007] According to the present disclosure, it becomes possible to appropriately set or manage AID when seamless roaming is performed.

[0008] Other features and advantages of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, in which the same or similar components are designated by the same reference numerals.

[0009] The accompanying drawings are included in and constitute a part of the specification, illustrate embodiments of the present disclosure, and are used, together with the description thereof, to explain the principles of the technology of the present disclosure. FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. FIG. 2 is a diagram illustrating an example of the hardware configuration of a communication device. FIG. 3 is a diagram illustrating an example of the functional configuration of a communication device. FIG. 4 is a diagram illustrating an example of the configuration of a MAC frame. FIG. 5A is a diagram illustrating an example of the configuration of a MAC frame. FIG. 5B is a diagram illustrating an example of the configuration of a MAC frame. FIG. 5C is a diagram illustrating an example of the configuration of a MAC frame. FIG. 6A is a diagram illustrating an example of the configuration of a MAC frame. FIG. 6B is a diagram illustrating an example of the configuration of a MAC frame. FIG. 6C is a diagram illustrating an example of the configuration of a MAC frame. FIG. 6D is a diagram illustrating an example of the configuration of a MAC frame. FIG. 6E is a diagram illustrating an example of the configuration of a MAC frame. FIG. 6F is a diagram illustrating an example of the configuration of a MAC frame. FIG. 6G is a diagram illustrating an example of the configuration of a MAC frame. FIG. 6H is a diagram illustrating an example of the configuration of a MAC frame. FIG. 7 is a diagram illustrating an example of the configuration of an AID Response element. FIG. 8 is a diagram illustrating an example of the flow of communication control processing in a wireless communication system. Fig. 9 is a diagram showing another example of the flow of communication control processing in a wireless communication system. Fig. 10A is a diagram showing an example of the flow of processing executed in a roaming destination AP. Fig. 10B is a diagram showing an example of the flow of processing executed in a roaming destination AP. Fig. 11A is a diagram showing an example of the flow of processing executed in a roaming source AP. Fig. 11B is a diagram showing an example of the flow of processing executed in a roaming source AP. Fig. 12 is a diagram showing an example of the flow of processing executed in a STA.

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the claims. Although multiple features are described in the embodiments, not all of these multiple features are required, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0011] (Explanation of Terms) Some technical terms used in this embodiment will be explained below.

[0012] "Collocated": Indicates a state in which devices are physically located in the same housing (same position). For example, the term "non-collocated" indicates a state in which devices are physically located in different housings (different positions). Note that during the process of reviewing the IEEE 802.11 series standards, the term may be written as "(non-) collocated," but the meaning is the same even when this term is used.

[0013] "Seamless roaming": Roaming refers to a station (STA) switching its connection to an AP other than the currently connected access point (AP). Roaming in which communication with the previous AP continues uninterrupted and does not require negotiation for a 4-way handshake or Block Ack for encrypted communication is called seamless roaming. Note that the terms "smooth" and "SMD (Seamless Mobility Domain)" are sometimes used instead of the term "seamless." Furthermore, "roaming" may also be expressed as "transition" or "Link Switch."

[0014] "State 4": This refers to the Authenticated and Associated state after a successful 4-way handshake. Furthermore, the Authenticated and Associated state when RSNA (Robust Security Network Association) is not required is also called "State 4." In the current IEEE 802.11 standard, when (Re)association is performed from this state, a transition to "State 2" is made by executing a Disassociation procedure. Note that State 2 refers to the Authenticated and Unassociated state.

[0015] "Context": This includes a security-related encryption key for unicast or multicast communication, and negotiation parameters for communication procedures such as the ADDBA procedure and the SCS (Stream Classification Service) procedure. The context may also include buffer data addressed to the STA in the AP. By transferring this context and buffer data from the previous AP to the roaming destination AP, the STA can continue to operate smoothly during roaming.

[0016] (System Configuration) FIG. 1 shows an example configuration of a wireless communication system according to this embodiment. This wireless communication system includes communication devices (AP 101, AP 104, and STA 108) that perform wireless communication in accordance with the IEEE 802.11 series standard. AP 101 is a first access point and has, for example, an AP MLD (Multi-Link Device) function in accordance with the IEEE 802.11be standard. AP 101 includes affiliated AP 102 and affiliated AP 103. Here, "affiliated" is a term indicating being related to or constituting an MLD. In the following description, affiliated AP 102 and affiliated AP 103 may be referred to as AP 102 and AP 103, respectively. Furthermore, AP 104 is a second access point having similar functions to AP 101, and includes affiliated AP 105 and affiliated AP 106 (which may be referred to as AP 105 and AP 106, respectively). AP 101 may be referred to as a "collocated AP" because it includes two affiliated APs, AP 102 and AP 103. AP 104 may also be referred to as a collocated AP, like AP 101, because it includes two affiliated APs, AP 105 and AP 106. Note that AP 101 and AP 104 are provided in separate housings located in different locations, and therefore can be said to have a non-collocated relationship.

[0017] The AP 101 and the AP 104 are configured to be able to communicate with each other via a distribution system (DS107) by utilizing the functions of their respective DSAFs (Distribution System Access Functions). The DS 107 can be configured using a wired communication medium such as Ethernet (registered trademark) or a telephone line, but is not limited to this. For example, the DS 107 may be configured using a wireless communication medium such as LTE (Long-Term Evolution) or WiMAX (Worldwide Interoperability for Microwave Access). The DS 107 may also be configured using other wireless communication media such as a wireless LAN conforming to the IEEE 802.11 series standards.

[0018] The STAs 108 are stations that comply with the IEEE 802.11be standard and can connect to the AP 101 or the AP 104. The STAs 108 include an affiliated STA 109 and an affiliated STA 110. Because the STAs 108 include two affiliated STAs, the STA 109 and the affiliated STA 110, they may be referred to as "collocated non-AP STAs." In one example, a link may be established between the affiliated AP 102 and the affiliated STA 109, and in parallel, a link may be established between the affiliated AP 103 and the affiliated STA 110. In this way, a link is established between the affiliated AP and the affiliated STA, and by establishing multiple such links, multiple links can be established in parallel between the AP 101 and the STA 108.

[0019] In the example of FIG. 1, two links are established between the AP and the STA. However, this is just an example, and three or more links may be established between the AP and the STA. Each link is assigned a Link ID to identify that link. In the IEEE 802.11be Draft standard, the AP can notify Link IDs from 0 to 14 using a Multi-Link element, which will be described later. The AP and the STA may communicate, for example, using frequency bands in the 5 GHz and 6 GHz bands, respectively, over two links. This is just an example, and, for example, two of the multiple links established may use different frequency channels in the same frequency band. Furthermore, the operating frequency of at least one of the links may be in the 2.4 GHz band.

[0020] In this embodiment, in the configuration of FIG. 1 , it is assumed that STA 108 transitions from a state in which it is connected to AP 101 by establishing two links to AP 104 by establishing two links. Conventionally, roaming has been performed by executing a procedure involving reassociation. In this procedure, the roaming destination AP issues an AID (Association Identifier) ​​to the STA, and the STA can communicate with the AP using the AID. On the other hand, in roaming involving reassociation, as described above, the STA transitions to state 2 by executing the disassociation procedure, and therefore a procedure is required to reset the STA to state 4 again. In contrast, in seamless roaming, roaming using a procedure called link reconfiguration is being considered. In this procedure, the STA can roam while maintaining state 4. However, in this procedure, it is not necessarily clear how to set an AID for the roaming STA. In view of this situation, this embodiment provides an (efficient) AID setting procedure for seamless roaming.

[0021] (Device Configuration) Fig. 2 shows an example of the hardware configuration of the communication device (AP 101, AP 104, and STA 108) of this embodiment. As an example of the hardware configuration, the communication device has, for example, a storage unit 201, a control unit 202, a function unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207. Note that these are just examples, and the communication device may have further components not shown in Fig. 2, or some or all of the components shown in Fig. 2 may be replaced with other components having similar functions.

[0022] The storage unit 201 includes one or more memories such as a ROM or a RAM. The storage unit 201 stores various information such as computer programs for performing various operations described below and communication parameters for wireless communication. ROM stands for Read Only Memory, and RAM stands for Random Access Memory. The storage unit 201 may include storage media such as a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memory card, and a DVD, in addition to memories such as a ROM and a RAM. The storage unit 201 may also include storage media such as a plurality of memories.

[0023] The control unit 202 includes one or more processors, such as a CPU or an MPU. The CPU stands for Central Processing Unit, and the MPU stands for Micro Processing Unit. The control unit 202 executes a computer program stored in the storage unit 201 to control the entire communication device. The control unit 202 may control the entire device through cooperation between the computer program stored in the storage unit 201 and an operating system. The control unit 202 may also generate data and signals (radio frames) to be transmitted in communication with other communication devices. The control unit 202 may also include multiple processors, such as multi-core processors, to control the entire communication device. The control unit 202 may also include, for example, an ASIC (application-specific integrated circuit), a DSP (digital signal processor), or an FPGA (field-programmable gate array).

[0024] Furthermore, the control unit 202 controls the functional unit 203 to execute predetermined processes such as wireless communication, image capture, printing, and projection. The functional unit 203 is configured to include hardware that enables the communication device to execute predetermined processes. If the communication device is a printer, the functional unit 203 is a printing device that prints image data acquired via the communication unit 206, for example. If the communication device is a scanner, the functional unit 203 is a reading device that outputs image data generated by scanning to the outside, for example, via the communication unit 206. If the communication device is a camera, the functional unit 203 is configured to include an image sensor and a lens, and outputs image data captured by the camera to the outside, for example, via the communication unit 206. Furthermore, the functional unit 203 may include components for implementing an AP function or an STA function.

[0025] The input unit 204 includes, for example, a touch panel, hard keys, buttons, etc., and accepts various operations from the user. The output unit 205 includes, for example, a display, a speaker, etc., and provides various outputs to the user. Here, the output by the output unit 205 may be a screen display output on a display or an audio output from a speaker. The output unit 205 may also include a vibrator and may output information by vibration output. Note that both the input unit 204 and the output unit 205 may be implemented by a single module, such as a touch panel display. The input unit 204 and the output unit 205 may be built into the communication device or may be implemented by an external input / output device. In this case, the communication device has an input / output interface for connecting to the input / output device.

[0026] The communication unit 206 executes control for wireless communication compliant with the IEEE 802.11 series standards. The communication unit 206 may, for example, control wireless communication compliant with the IEEE 802.11be standard, the IEEE 802.11bn standard, or successor standards thereof, or control wired communication such as a wired LAN. The communication unit 206 controls the antenna 207 to transmit and receive signals for wireless communication generated by the control unit 202. For example, the communication device communicates data such as image data, document data, and video data with a partner device via the communication unit 206. Note that if the communication device supports the NFC standard or Bluetooth standard in addition to the IEEE 802.11 series standards, the communication unit 206 may also control wireless communication compliant with these communication standards. Furthermore, if the communication device is capable of wireless communication compliant with multiple communication standards, separate communication units and antennas corresponding to those communication standards may be provided.

[0027] The antenna 207 is, for example, an antenna capable of detecting and emitting radio waves in the 2.4 GHz band, the 5 GHz band, and the 6 GHz band. The antenna 207 may be configured to be capable of communication in the same frequency band. In this case, the antenna 207 may be, for example, a multi-band antenna capable of communication in multiple frequency bands. While FIG. 2 illustrates an example in which the communication device has only one antenna, multiple antennas may be used depending on the number of available spatial streams. If the communication device has multiple antennas, it may have a communication unit 206 corresponding to each antenna. The antenna 207 may be provided separately from the communication unit 206, or may be configured together with the communication unit 206 as a single module.

[0028] FIG. 3 illustrates an example of the functional (software) configuration of a communication device (AP 101, AP 104, and STA 108) according to this embodiment. The communication device includes, as its functions, a wireless LAN control unit 301, a multi-link control unit 302, an AID management unit 303, a security control unit 304, a QoS control unit 305, a roaming control unit 306, a storage unit 307, a UI control unit 308, and an antenna control unit 309. Note that these functional configurations are merely examples, and other functions may be added, or the illustrated functions may be modified. For example, one functional block illustrated in FIG. 3 may be divided into multiple blocks, or multiple functional blocks may be integrated into one. Furthermore, some functions may be omitted, or functions not illustrated may be added. In one example, at least some of the functions illustrated in FIG. 3 may be implemented by the control unit 202 executing a program stored in the storage unit 201. Furthermore, at least some of the functions illustrated in FIG. 3 may be implemented using dedicated hardware.

[0029] The wireless LAN control unit 301 includes circuits for transmitting and receiving wireless signals with other wireless LAN communication devices (e.g., other APs or STAs) and programs for controlling these circuits. The wireless LAN control unit 301 generates and transmits frames and receives wireless frames from other communication devices in accordance with the IEEE 802.11 series standard. The multi-link control unit 302 controls multiple wireless LAN interfaces to control communications using multiple links (multi-link communications). The AID management unit 303 manages association identifiers (AIDs) that uniquely identify STAs in the BSS (Basic Service Set) managed by the AP. For example, when connecting with a STA, the AID management unit 303 of the AP assigns an AID to the STA and maintains and manages the AID for subsequent communications. The AID management unit 303 of the STA also holds the AID assigned by the AP. The AID management unit 303 updates the AID by communicating with the other device as necessary. The security control unit 304 executes the RSNA (Robust Security Network Association) procedure. The security control unit 304 mainly executes various key exchanges for data confidentiality and integrity using a 4-way handshake. The QoS control unit 305 performs priority control based on stream communication and data type to control the quality of service for the data being communicated. The roaming control unit 306 determines the need for AP switching and executes various procedures for seamless roaming.

[0030] The storage unit 307 controls storage in storage devices such as a ROM (Read Only Memory) or a RAM (Random Access Memory) that store programs executed by the AP or STA and various data. The UI control unit 308 includes hardware related to a user interface (UI), such as a touch panel or buttons, for accepting operations on the AP or STA by a user (not shown), and a program for controlling these. The UI control unit 308 also has a function for presenting information to the user, such as displaying images or outputting audio. The antenna control unit 309 controls the antenna function.

[0031] (Frame Configuration) Next, an example of the configuration of a MAC (medium access control) frame conforming to the IEEE 802.11 series standard used in this embodiment will be described. An example of the configuration of a MAC frame is shown in Fig. 4. Note that Fig. 4 mainly shows fields particularly related to this embodiment, and the MAC frame naturally includes fields conforming to the IEEE 802.11 series standard (not shown).

[0032] Specifically, Frame Control 401 is configured to include 10 subfields and is a field that stores information indicating the frame type, such as Management / Control / Data, and the direction in which the frame is transmitted. Address 402 is configured to include up to four fields. Address 402 is configured to store addresses such as BSSID (Basic Service Set IDentifier), source, and destination depending on the MAC frame type. Note that Address 402 is omitted for frames of a predetermined type. Sequence Control 403 is a field that stores a sequence number for controlling the order of data. Sequence Control 403 is omitted for control frames. Frame Body 404 stores the data to be transmitted by the frame. If the frame type is a management frame, various IEs (Information Elements) are stored in this field in the Frame Body 404. Note that management frames include, for example, frames such as a Beacon, a Probe Request / Response, and an Action. The FCS 405 is the final field of the MAC frame. Note that FCS stands for Frame Check Sequence.

[0033] 5A to 5C show example configurations of the Frame Body 404 of an Action frame. When the above-mentioned two-octet Frame Control 401 is expressed as B0B1...B14B15, the Action frame is a frame in which B3B2 is set to "00" representing Management, and B7B6B5B4 is set to "1101." Note that the order of bit numbers in the Frame Control 401 and the explanation of the values ​​of each bit is reversed in accordance with the notation of the IEEE 802.11 series standards.

[0034] The Frame Body 404 of the Action frame includes a Category 501 and Action Details 502. The Category 501 indicates a major classification of the Action. As of IEEE 802.11be Draft 5.01, 38 types of classifications are defined, ranging from Code = 0 (Spectrum Management) to Code = 37 (Protected EHT), as shown in Fig. 5B. Note that Fig. 5B shows, as an example, an example in which Code = 38 and Code = 39 for UHR (Ultra High Reliability) and Protected UHR for IEEE 802.11bn, which is currently under standardization consideration, have been added.

[0035] Action Details 502 is a field having a length corresponding to each Action, and is configured to include, for example, Action ID 503, Dialog Token 504, and element 505 corresponding to each Action. Action ID 503 stores a value indicating the type of Action. FIG. 5C shows the correspondence relationship between the value stored in Action ID 503 and the type of Action. As shown in FIG. 5C, when the Action is Link Reconfiguration Notify, which will be described later, "10" is stored in Action ID 503. Similarly, in the case of a Link Reconfiguration Request, "11" is stored in the Action ID 503, and in the case of a Link Reconfiguration Response, "12" is stored in the Action ID 503. The Dialog Token 504 is information used to identify a procedure when multiple Action procedures have been established. The element 505 is an information element in which various information is stored.

[0036] 6A to 6H, the basic configuration of a multi-link element that can be stored as element 505 will be described. A multi-link element is an information element used for management and operations related to multi-links. The following mainly describes matters directly related to this embodiment. In other words, information other than the matters described below may be included in a multi-link element.

[0037] In Fig. 6A, Element ID 601 and Element ID Extension 603 are identifiers for indicating the type of element. As shown in Fig. 6B, when element 505 is a multi-link element, Element ID 601 is set to "255" and Element ID Extension 603 is set to "107". Length 602 stores a value indicating the entire length of this element. Multi-Link Control 604 will be described later. Common Info 605 includes information common to established links. Per-STA Profile 606 will also be described in detail later.

[0038] As shown in Fig. 6C, the Multi-Link Control 604 includes three subfields: a 3-bit Type 611, a 1-bit Reserved 612, and a 12-bit Presence Bitmap 613. The Type 611 indicates the use of the Multi-Link element, and currently, values ​​from 0 to 4 are defined, as shown in Fig. 6D. When setting up a multi-link, that is, for a connection specifying a multi-link, Basic, with a Type 611 value of "0", and Probe Request, with a Type 611 value of "1", are used. If the Type 611 value is "2", it indicates that this element is related to reconfiguration. Reconfiguration can be used to add or delete links after multilink setup. Presence Bitmap 613 is used to indicate the presence or absence of various information in the Common Info 605 field with one bit each. Note that the value of Type 611 defines the information that can be included in the Common Info 605 field, and the content of Presence is determined accordingly.

[0039] The following describes an example where the value of Type 611 is set to "2" (Reconfiguration). In this case, as shown in Fig. 6C, Presence Bitmap 613 includes six bits from MLD MAC Address Present 614 to AID Present 619. Presence Bitmap 613 also includes six reserved bits 620 to 625, each bit assigned a code in preparation for future expansion. The six bits from MLD MAC Address Present 614 to AID Present 619 correspond to MLD MAC Address 632 to AID 637, respectively, of Common Info 605 shown in Fig. 6E. MLD MAC Address Present 614 to AID Present 619 are each set to "1" if corresponding information exists in Common Info 605, and are set to "0" if such information does not exist. For example, MLD MAC Address Present 614 is set to "1" if MLD MAC Address 632 exists. The link during seamless roaming is specified by the combination of MLD MAC Address 632 and Link ID. EML Capabilities Present 615 is set to "1" if EML Capabilities 633 exists. MLD Capabilities And Operations Present 616 is set to "1" if MLD Capabilities And Operations 634 is present.

[0040] Roaming AP MLD MAC Address 635, AP MLD Roaming ID 636, and AID 637 are information newly introduced in this embodiment. Roaming AP MLD MAC Address 635 stores the address of the SAP (Service Access Point) of the MAC layer when seamless roaming is performed. When this information is included in Common Info 605, the value of Roaming AP MLD MAC Address Present 617 is set to "1". The SAP function may be performed by a terminal (not shown) in DS 107 or by AP 101 and AP 104 cooperating with each other. The cooperative operation of AP 101 and AP 104 is controlled by a roaming control unit 306. In either case, the SAP is a MAC layer function or a MAC entity that exists when multiple APs that realize the seamless roaming function are treated as one virtual roaming AP MLD.

[0041] AP MLD Roaming ID 636 stores information identifying an AP MLD included in an AP MLD group that has established a seamless roaming relationship. When this information is included in Common Info 605, AP MLD Roaming ID Present 618 is set to "1". AID 637 stores an AID (Association IDentifier) ​​that is newly assigned when the seamless roaming procedure is completed. When this information is included in Common Info 605, AID Present 619 is set to "1". In this embodiment, AID is assigned on an AP MLD basis and is specified in Common Info.

[0042] Next, the Per-STA Profile 606 will be described with reference to Figures 6F to 6H. The Per-STA Profile 606 includes a Subelement ID 641, a Length 642, and Data 643. The Per-STA Profile 606 includes information for each link. Note that multiple Per-STA Profile 606 fields may be referred to as Link-Info fields.

[0043] In Per-STA Profile 606, Data 643 includes a STA Control field 644, STA Info, and STA Profile. STA Info includes STA Info Length 645 and STA Info 646. STA Profile includes Capability Information 647, Element 648, and Non-Inheritance element 649. STA Profile is not particularly related to the processing according to this embodiment, and therefore detailed description thereof will be omitted.

[0044] The STA Control field 644 is configured to include items from Link ID 650 to NSTR Indication Bitmap Present 657, and Reserved 658 to 659. Here, of the items included in the STA Control field 644, fields marked with "Present" indicate that the actual value is set in the STA Info sequence 646. On the other hand, for items not marked with "Present", the value related to that item itself is set. STA Info Length 645 stores a value indicating the length of the entire STA Info. The STA Info sequence 646 has a configuration as shown in FIG. 6H. Details of the STA Info sequence 646 will be described later.

[0045] In the STA Control field 644, the Link ID 650 stores a value that identifies the affiliated AP / STA in the MLD when setting up a multi-link or reconfiguring a link. That is, a value that specifies the affiliated AP 102, the affiliated AP 105, the affiliated STA 109, etc. is stored in the Link ID 650. The Complete Profile 651 stores a value that indicates whether the STA Info contains all of the information related to the link. That is, the value stored in the Complete Profile 651 specifies whether the STA Info contains partial information related to the link or all of the information related to the link.

[0046] The MAC Address Present 652 is set to "1" if the STA MAC Address 662 is present in the STA Info sequence 646, and is set to "0" if it is not present. The AP Removal Timer Present 653 is set to "1" if the AP Removal Timer 663 is present in the STA Info sequence 646, and is set to "0" if it is not present. The Reconfiguration Operation Type 654 is a 4-bit field, and specifies the type of reconfiguration procedure. Figure 6G shows the correspondence between the values ​​set in the Reconfiguration Operation Type 654 and their meanings. For example, in the case of seamless roaming, the procedure for deleting the roaming source link is specified by setting the value of Reconfiguration Operation Type 654 to "3." Furthermore, the procedure for adding a roaming destination link is specified by setting the value of Reconfiguration Operation Type 654 to "2." When a link is added, all information about the link is included in the frame, and the value of Complete Profile 651 is set accordingly.

[0047] Operation Parameters Present 655 is set to "1" if Operation Parameters 664 is present in the STA Info sequence 646, and is set to "0" if not present. NSTR Bitmap Size 656 stores a value indicating the size of NSTR Indication Bitmap 665 in the STA Info sequence 646. NSTR Indication Bitmap Present 657, when this bit is set to "1", indicates that NSTR Indication Bitmap 665 is present.

[0048] When an AID is assigned on a link-by-link basis, the AID is specified in the Per-STA Profile 606. In this case, AID Present is indicated using one bit of Reserved 658-659 in the STA Control field 644. Then, in the STA Info sequence 646, a two-octet field is added after the NSTR Indication Bitmap 665, and the AID can be indicated in that field.

[0049] 7 shows an example of the configuration of an AID Response element introduced in the IEEE 802.11ah standard. In this element, "211" is set as the value of Element ID 701. A value indicating the length of this element is stored in Length 702. AID / Group AID 703 is a field having a length of 2 octets and storing an AID. AID Switch Count 704 is set with a value specifying the period until the AP sets a new AID for the STA. AID Response Interval 705 stores information indicating the period during which the STA should be active during association.

[0050] Currently, this information element can be used for communication in the 1 GHz band (S1G), but in this embodiment, it is also used for seamless roaming in the 2.4 GHz / 5 GHz / 6 GHz bands (non-S1G). Therefore, while AID values ​​of 1 to 8191 are used in the 1 GHz band, in this embodiment, AID values ​​of 1 to 2007 are used. Note that in non-S1G, different information element names or information elements may be used, but in either case, communication of information elements for performing similar functions is possible.

[0051] In the current standard, this AID Response element is specified to be used in management frames such as (re)Association Response and AID Switch Response. Therefore, if this rule is followed, a new management frame (Action frame) for seamless roaming may be defined.

[0052] (Flow of communication processing) Next, an example of the flow of communication control processing according to this embodiment will be described. Fig. 8 shows an example of the flow of communication processing executed in the wireless communication system according to this embodiment. In the following, it is assumed that AP 101 is the AP (source AP) from which STA 108 roams, and AP 104 is the AP (target AP) to which STA 108 roams.

[0053] 8, first, AP 101 and AP 104 search for other APs in the vicinity that can perform seamless roaming (S801). Here, it is assumed that AP 101 discovers AP 104, and AP 104 discovers AP 101. AP 101 then broadcasts information about seamless roaming (S802). AP 101 broadcasts information about seamless roaming by notifying its capabilities using the capabilities element of the management frame or by notifying its operating status using the operation element. AP 104 also broadcasts similar information. Here, the information about seamless roaming may include, for example, information that the own device (AP 101 or AP 104) is capable of executing seamless roaming, and information about surrounding APs that are capable of executing seamless roaming.

[0054] Thereafter, the AP 101 executes a connection procedure in response to a request from the STA 108, for example, and establishes a connection with the STA 108 (S803). This connection procedure includes an exchange of an Association Request and an Association Response, in which the value of the Type 611 of the Multi-Link element is set to "0" (Basic). This results in a multi-link setup between the AP 101 and the STA 108. Note that in this case, the information contained in the Presence Bitmap 613 and Common Info 605 of the Multi-Link element is different from that in the case of Reconfiguration, in which the Type 611 is "2." That is, in this case, the Multi-Link element includes a Link ID, an AP MLD ID, MLD Capabilities and Operations, etc. The MLD Capabilities and Operations include information indicating whether seamless roaming is supported. That is, by receiving this information, the STA can determine whether the affiliated AP identified by the Link ID supports seamless roaming. The STA can then select and connect to, for example, an affiliated AP that supports seamless roaming. In order to ensure the quality of service (QoS) of the application operated by the STA 108, the STA 108 negotiates a Stream Classification Service (SCS) with the AP 101 to which it is connected (S804). The STA 108 also negotiates a Block Ack with the AP 101 (S805). After completing these negotiations, the STA 108 performs data communication (S806).

[0055] Then, during the connection, the AP 101 and the STA 108 notify each other of information that can be used to determine the necessity of roaming (S807). This information includes, for example, information on radio wave strength (e.g., whether the radio wave strength is above or below a predetermined value), movement of the AP 101 or the STA 108, and whether the AP 101 is satisfying the QoS required by the STA 108. The AP 101 and the STA 108 determine the necessity of roaming based on the exchanged information. In one example, it may be determined that roaming is necessary when the radio wave strength falls below a predetermined value, when the QoS required by the STA 108 is no longer satisfied, or when the distance between the AP 101 and the STA 108 exceeds a predetermined distance.

[0056] When the AP 101 or the STA 108 determines that roaming is necessary, it transmits a Link Reconfiguration Notify to the other device (the STA 108 from the AP 101's perspective, and the AP 101 from the STA 108's perspective) (S808). The Link Reconfiguration Notify is an Action frame in which the above-mentioned Action ID 503 is set to "10", and also has the meaning of a recommendation for reconfiguration of the multi-link. The Link Reconfiguration Notify includes one Per-STA Profile for each affiliated AP. Then, the (Basic) Multi-Link element used when establishing a connection in S803 can be used to indicate the addition or deletion of a link to the set up multi-link configuration. At this time, the link is specified by a combination of the MAC address and Link ID of the AP MLD. For example, the link corresponding to AP 102 can be specified by the MAC address of AP 101 and Link ID = 0, and the link corresponding to AP 103 can be specified by the MAC address of AP 101 and Link ID = 1. Furthermore, the link corresponding to AP 105 can be specified by the MAC address of AP 104 and Link ID = 0, and the link corresponding to AP 106 can be specified by the MAC address of AP 104 and Link ID = 1. Here, the characteristics / capabilities of each link are indicated by a Per-STA Profile 606. Note that the Link Reconfiguration Notify is transmitted only in either the direction from the AP 101 to the STA 108 or from the STA 108 to the AP 101. However, since this frame may be transmitted from either the AP 101 or the STA 108, the transmission and reception of this frame are indicated by a bidirectional arrow in Fig. 8. Furthermore, this frame may include a BSS Transition Candidate List used in the BSS Transition Management Query procedure of the IEEE 802.11 standard.This frame may also include AP information in the (Reduced) Neighbor Report. Thereafter, the AP 101 (Source AP) and the AP 104 (Target AP) establish a relationship that enables seamless roaming between them (S809).

[0057] Thereafter, STA108 transmits a link reconfiguration request to AP101 (S810). This is an Action frame with Action ID 503 of "11". The MAC address of STA108 is set in the MLD MAC Address of the Common Info in the Multi-Link element of this frame. In this sequence, for example, it is assumed that STA108 accepts the addition and deletion of links notified by the Link Reconfiguration Notify from AP101 and decides to perform roaming. Note that if STA108 desires a different roaming destination, STA108 transmits a Multi-Link probe request before S810. Then, the AP 101 can notify the STA 108 of information about other APs by using a Multi-Link probe response. At this time, the AP 101 transmits the Multi-Link probe response including information about other APs with which a relationship capable of performing seamless roaming in S809 has been established.

[0058] The AP 101 transmits a Seamless Roaming Request to the AP 104, the roaming destination determined by the procedure up to S810 (S811). This frame is an Action frame, which is newly defined in this embodiment. Upon receiving this frame, the AP 104 may transmit a response frame to the AP 101. However, this response may be omitted, for example, on the condition that the AP 104 is ready to accept the roaming request as a result of the processing of S809. Furthermore, this response does not always need to be transmitted. After the roaming request, the AP 101 transfers data buffered for the STA 108 to the AP 104 (S812). The AP 101 also transfers a context including, for example, AID (Association IDentifier) ​​information set for the STA 108 (S813). Here, the context may include, for example, information indicating the results of the QoS and Block Ack (BA) negotiations in S804 and S805. Note that, since the AID can be independently determined by the AP 104 as described below, the context notified from the AP 101 does not need to include the AID information. Also, the AID may be included in, for example, a Seamless Roaming Request, in which case the AID information does not need to be included in the context.

[0059] The AP 104 determines the AID value and determines the notification method (S814). At this time, the AP 104 may decide to continue using the AID notified by the AP 101. The AP 104 also determines the notification method: whether the AP 104 notifies the STA 108 of the AID itself, or whether the AP 101 notifies the STA 108 of the AID. Note that the notification method may be determined in advance, in which case the AP 104 may only determine the AID. Thereafter, the AP 104 transmits a Seamless Roaming Response to the AP 101 (S815). This frame is an Action frame newly defined in this embodiment. In FIG. 8, it is assumed that the AID information newly assigned by the AP 104 is included in this frame.

[0060] Upon receiving the Seamless Roaming Response, the AP 101 transmits a Link Reconfiguration Response, which corresponds to a response to the frame of S810, to the STA 108 (S816). This frame is an Action frame in which the Action ID 503 is set to "12." In this embodiment, the Link Reconfiguration Response is transmitted with the AID information determined by the AP 104 included. Here, this Link Reconfiguration Response is a frame that can be received by a STA in state 4. The AP 101 transmits a Link Reconfiguration completion notification to the AP 104 (S817). This frame is an Action frame newly defined in this embodiment. When the AP 104 receives this notification, if it holds data addressed to the STA 108, it transmits a beacon containing a bitmap of a TIM (Traffic Indication Message) indicating the presence of such data. The STA 108 then switches its communication partner to the AP 104 and continues communication.

[0061] In the above processing example, the STA 108 receives notification of the AID from the AP 101, which is the destination of the Link Reconfiguration Request. This allows the STA 108 to receive a frame related to the STA 108, including AID information, from the roaming destination AP 104 at an early stage. Note that after S809, information exchange and negotiation may be performed using a Multi-Link Probe Request from the STA 108 to the AP 101 and a Multi-Link Probe Response from the AP 101 to the STA 108.

[0062] In the above processing example, an example in which the AP 101 notifies the AID determined by the AP 104 has been described. Next, with reference to Fig. 9, an example in which the AP 104 itself notifies the STA 108 of the AID determined by the AP 104 will be described. In Fig. 9, the processing of S801 to S814 is the same as in Fig. 8. It is assumed that the AP 104 selects a method in which the AP 104 itself notifies the AID as the notification method in S814.

[0063] In this case, the AP 104 transmits a Seamless Roaming Response that does not include AID information to the AP 101 (S901). Then, the AP 101 transmits a Link Reconfiguration Response that does not include AID information to the STA 108 (S902). In this case, the STA 108 treats its own device as if its AID has not yet been assigned. With this AID not assigned, the STA 108 executes link switching to make the AP 104 its communication partner. The AP 101 transmits a Link Reconfiguration completion notification to the AP 104, as in S817 (S903). Then, the AP 104 notifies the STA 108, which has performed the link switching, of the AID (S904). This notification is performed using the AID Switch Response Action frame introduced in the IEEE 802.11ah standard, as described in FIG. 7 . This frame is an Action frame with a Category Code value set to "22" and may include the AID Switch element described above. Alternatively, a new Action frame that can be received by the STA 108 in state 4 may be used for this notification. A new Action ID for the Action frame for UHR may be defined for this frame. Once the AID of the STA 108 is set, the AP 104 transmits the TIM bitmap in a Beacon if data addressed to the STA 108 exists, as in FIG. 8 (S818).

[0064] 9 , the STA 108 receives the AID from the roaming destination AP 104. In this case, as described above, the STA 108 receives the Link Reconfiguration Response, and after being connected to the roaming destination AP 101, receives notification of the AID and becomes able to communicate using that AID.

[0065] As shown in Figures 8 and 9, in this embodiment, the AP for notifying the AID and the timing of the notification frame are determined by the AP 104 of the roaming destination using seamless roaming. In one example, if the STA 108 can manage another AID before connecting to the AP 104 of the roaming destination, i.e., while maintaining connection with the AP 101 of the roaming source, the AP 101 notifies the STA 108 of the AID managed by the AP 104. Also, if the STA 108 cannot manage another AID while maintaining connection with the AP 101 of the roaming source, the AP 104 may notify the AID. That is, depending on whether the STA 108 can manage multiple AIDs, it may be determined whether the AP 101 or the AP 104 should notify the STA 108 of the AID to be used for communication with the AP 104 after roaming. Alternatively, the AP 101 may notify the STA 108 if the AID does not change before and after roaming, and the AP 104 may notify the STA 108 if the AID changes. Furthermore, if the period until the transmission timing of a beacon including a TIM from the roaming destination AP 104 is short, the AID may be notified from the AP 101 as shown in FIG. 8 , and if the period is long, the AID may be notified from the AP 104 as shown in FIG. 9 . In this manner, when the time for the AP 104 to transmit a beacon including a TIM is approaching, the AID can be quickly notified to the STA 108 via the AP 101. Furthermore, the AP to notify the AID after roaming may be determined based on other criteria (e.g., the capabilities and communication conditions of the STA 108). This prevents the STA from being unable to notify the AID due to its capabilities or conditions, and allows the AID to be set and managed appropriately. As a result, the BSS can be managed appropriately when seamless roaming is performed. While the above example illustrates an example in which the AP to notify the AID is determined by the roaming destination AP 104, this determination may also be made by the roaming source AP 101. In this case, for example, the result of the decision can be notified from AP 101 to AP 104 together with the context.

[0066] Next, an example of the flow of processing executed by the AP (AP 104) at the roaming destination will be described with reference to Figures 10A and 10B. Note that the flow of processing shown below is an example, and the order of the processing steps may be changed as necessary, or some steps may be omitted. Further, additional steps may be added.

[0067] This process is executed in a state where the establishment of a seamless roaming relationship with the roaming source AP (AP 101) has been completed in S809. In this state, the AP 104 executes the following process in response to receiving a Seamless Roaming Request from the roaming source AP (AP 101) (S1001). Here, the AP 104 unconditionally accepts the roaming request received in S1001 without sending a response. However, this is just an example, and the AP 104 may also confirm the contents of the request and determine whether to accept the request, and then send a response to the AP 101 according to the result of the determination.

[0068] Thereafter, the AP 104 determines whether AID information indicating the AID of the roaming STA (STA 108) has been received from the AP 101 (S1002). The AID information may be included in the request received in S1001, or may be received separately from the request as context information as shown in FIGS. 8 and 9. The context information shown in FIGS. 8 and 9 may be included in the request and transmitted. If the AID is received via the context, the process of S1006 (described below) may be executed before the determination of S1002. If the AP 104 determines that the AID information has been received (YES in S1002), it determines whether the AID indicated by the AID information needs to be changed (S1003). If the AP 104 determines that an AID change is necessary (YES in S1003), it determines an AID to be newly assigned to the STA 108 (S1004). If it determines that a change is not necessary (NO in S1003), it determines to use the received AID as is. Furthermore, if the AP 104 has not received AID information (NO in S1002), it determines an AID to be newly assigned to the STA 108 (S1004). The AP 104 receives buffered data addressed to the STA 108 from the AP 101 (S1005) and receives the context of the STA 108 (S1006). The context may include, for example, information regarding QoS and BA negotiation.

[0069] The AP 104 decides to use the notified AID as is, or after determining a new AID, decides whether to notify the AID itself or have the roaming source AP 101 notify it. The AP 104 makes this determination, for example, based on the length of time until the transmission timing of the beacon (S1007, S1008, S1009). For example, if the period until the transmission timing of the beacon including the TIM is equal to or shorter than a predetermined length (YES in S1007), the AP 104 decides to have the AP 101 notify the STA 108 of the AID (S1008). On the other hand, if the period until the transmission timing of the beacon including the TIM exceeds the predetermined length (NO in S1007), the AP 104 decides to notify the STA 108 of the AID from the AP 104 itself (S1009). As described above, whether the AID is notified from AP 101, which is the roaming source AP (source AP), or AP 104, which is the roaming destination AP (target AP), may be determined based on other criteria.

[0070] Thereafter, the AP 104 transmits a response to the seamless roaming request to the AP 101 (S1010). If the AP 104 determines in S1008 that the AP 101 should notify the STA 108 of the AID, the AP 104 transmits an AID notification instruction including AID information in the response. The AP 104 may also transmit an AID notification instruction separately from the response. The AP 104 also receives a Link Reconfiguration completion notification from the AP 101 (S1011). If the AP 104 determined in S1009 that the AP 104 should notify the AID (YES in S1012), the AP 104 notifies the STA 108 of the AID (S1013). This notification may be performed, for example, using an Action frame. The AP 104 then starts transmitting a frame including data addressed to the STA (S1014). For example, a beacon including a TIM bitmap indicating that data addressed to the STA 108 exists is transmitted.

[0071] In addition, the determination in S1007 may take into consideration the transmission timing of frames other than the beacon. For example, a frame whose PHY header includes information corresponding to the AID of the STA 108 (e.g., STA_ID information) may be taken into consideration in the determination in S1007. For example, a trigger frame, an NDP (Null Data Packet) Announcement frame, or an MU PPDU (Multi User Physical Layer Protocol Data Unit) frame may be taken into consideration. In the case of the IEEE 802.11ax standard, the STA_ID is the lowest 11 bits of the AID.

[0072] Next, an example of the flow of processing executed by the roaming source AP 101 will be described with reference to Figures 11A and 11B. Note that the flow of processing shown below is an example, and the order of processing steps may be changed as necessary, some steps may be omitted, or further steps may be added.

[0073] This process is executed after the establishment of a seamless roaming relationship with the roaming destination AP (AP 104) has been completed in S809. AP 101 transmits information about seamless roaming using a management frame (S1101). AP 101 transmits this information, for example, as information elements for capabilities (UHR Capabilities) and operation (UHR Operation) in a beacon or a probe response, which is a response to a probe request from a STA. AP 101 then establishes a connection with STA 108 (S1102). This connection procedure also includes negotiation regarding whether AP 101 will enable seamless roaming for STA 108. Furthermore, in this connection procedure, the AP 101 may notify the STA 108 of a list of candidate APs to roam to. The AP 101 then executes the SCS procedure with the STA 108 to accept the QoS request of the STA 108 (S1103), and further negotiates a Block Ack with the STA 108 (S1104). The Block Ack negotiation is performed by transmitting and receiving an ADDBA request and an ADDBA response.

[0074] Thereafter, the AP 101 determines whether or not roaming of the connected STA 108 is necessary (S1105). The AP 101 may determine that roaming of the STA 108 is necessary, for example, when the wireless quality or throughput, such as the RSSI (Receive Signal Strength Indicator) of a frame from the STA 108, falls below a predetermined value. The AP 101 may receive information on the wireless quality and throughput of the STA 108 from the STA 108, and determine that roaming of the STA 108 is necessary when the wireless quality or throughput falls below a predetermined value. If the AP 101 determines that roaming is necessary, it transmits a Link Reconfiguration Notify to the STA 108 (S1106). Alternatively, when the STA 108 determines that roaming is necessary, the AP 101 receives a Link Reconfiguration Notify from the STA 108 (S1106). When the AP 101 transmits a Link Reconfiguration Notify to the STA 108, the AP 101 may transmit information about candidate APs for roaming in the notification.

[0075] Thereafter, when the AP 101 receives a Reconfiguration Request from the STA 108 (S1107), it transmits a Seamless Roaming Request to the roaming destination AP 104 (S1108). The AP 101 also transfers data addressed to the STA 108 that is stored in its own buffer to the AP 104 (S1109), and transmits the context of the STA 108 (S1109). The AP 101 retains the buffered data and context without discarding them until roaming is complete.

[0076] Thereafter, the AP 101 receives a response to the roaming request from the AP 104 (S1111), and determines whether the response includes an AID notification instruction (S1112). If the AP 101 determines that the response includes an AID notification instruction (YES in S1112), the AP 101 sets an AID value field in the Link Reconfiguration Response and stores the AID value in that field. Note that the AID value here is notified by the AP 104. The AP 101 then transmits a Link Reconfiguration Response including the AID value to the STA 108 (S1114). On the other hand, if the AP 101 determines that the response does not include an AID notification instruction (NO in S1112), it transmits a Link Reconfiguration Response that does not include an AID value to the STA 108 (S1114). The AP 101 also transmits a Link Reconfiguration completion notification to the AP 104 (S1115). The AP 101 then determines that roaming is complete in response to the completion of the processing of S1115, and discards the buffered data and context addressed to the STA 108 that were maintained after being transmitted to the AP 104 in S1109 and S1110.

[0077] 12 illustrates an example of the flow of processing executed by the STA 108. Note that the flow of processing shown below is an example, and the order of the processing steps may be changed as necessary, or some steps may be omitted. Further, additional steps may be added.

[0078] First, the STA 108 connects to the AP 101 (S1201). At this time, the STA 108 may determine the AP to connect to based on whether the AP supports seamless roaming. The STA 108 then performs an SCS procedure with the AP 101 to set QoS (S1202) and negotiates a Block Ack (S1203). Thereafter, the STA 108 continuously determines whether roaming is necessary while communicating with the AP 101 (S1204). Whether roaming is necessary is also determined by the AP 101, as described above, and roaming is performed depending on whether either the AP 101 or the STA 108 determines that roaming is necessary. If the STA 108 determines that roaming is necessary, it transmits a Link Reconfiguration Notify to the AP 101 (S1205). Furthermore, when the AP 101 determines that roaming is necessary, the STA 108 receives a Link Reconfiguration Notify from the AP 101 (S1205). The STA 108 determines the AP to roam to based on the result of the roaming necessity determination or the AP information included in the received Link Reconfiguration Notify. After determining the AP to roam to, the STA 108 transmits a Link Reconfiguration Request to the AP 101 (S1206) and receives a Link Reconfiguration Response from the AP 101 (S1207). The STA 108 can thereby obtain the AP MLD MAC address of the roaming destination AP contained in the Link Reconfiguration Response. The STA 108 then determines whether the Link Reconfiguration Response contains AID information (S1208). If the Link Reconfiguration Response does not contain AID information (NO in S1208), the STA 108 waits for a notification of AID information from the roaming destination AP 104 (S1209).For example, the STA 108 waits for an AID notification frame from the AP having the AP MLD MAC address acquired in S1207. If the STA 108 does not receive the AID notification frame within a predetermined time, it may output an error and terminate the process. When the STA 108 receives the AID notification frame (YES in S1209), it updates the AID it manages using the AID information notified by the frame (S1210). If the Link Reconfiguration Response contains AID information (YES in S1208), the STA 108 updates the AID it manages using the AID information (S1210). The STA 108 then begins receiving frames that specify the updated AID and contain information addressed to the STA 108 (S1211).

[0079] As described above, in this embodiment, when a STA performs seamless roaming, whether the AP that notifies the STA of the AID is the roaming source AP or the roaming destination AP is selected depending on the situation. According to this, for example, if the period until a frame using the post-roaming AID to be received by the STA is transmitted is short, the AID is transmitted to the STA before the roaming connection is completed, allowing the STA to receive the frame. Furthermore, if the period until transmission of such a frame is sufficiently long, the AID is transmitted after the connection with the roaming destination AP is established, thereby preventing a situation in which a connection cannot be established with the AP for which the AID is set. Furthermore, the AP that transmits the post-roaming AID may be determined based on other conditions, making it possible to set the AID in a format suitable for various conditions.

[0080] The present disclosure can also be realized by a process in which a program that realizes one or more functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present disclosure can also be realized by a circuit (e.g., an ASIC) that realizes one or more functions.

[0081] The technical ideas derived from this disclosure are not limited to the disclosed exemplary embodiments, but are intended to encompass various modifications to the exemplary embodiments, or the replacement of equivalent structures or functions, etc. The scope of the following claims should be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0082] This application claims priority based on Japanese Patent Application No. 2024-106884, filed July 2, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A communications device that functions as an access point (AP) conforming to the IEEE 802.11 series standards, comprising: a receiving means for receiving, from another AP, a request for roaming that does not involve reassociation of a station (STA) connected to the other AP; a determining means for determining, based on the received request, an association identifier (AID) of the STA and determining whether the AP or the other AP will notify the STA of the AID; and a notifying means for, when notifying the STA from the other AP of the AID, notifying the other AP of the AID and an instruction indicating that the AID should be transmitted from the other AP, and when notifying the STA of the AID from the AP, notifying the STA of the AID.

2. The communication device according to claim 1, wherein the determination means, when receiving from the other AP an AID used for communication between the other AP and the STA, determines whether to continue using the AID or to set a new AID.

3. The communication device according to claim 2, wherein said receiving means receives said request including an AID used in communication between said other AP and said STA.

4. The communication device according to claim 2, wherein said receiving means receives context information relating to said STA, including an AID used in communication between said other AP and said STA.

5. The communication device according to any one of claims 1 to 4, wherein when the AID is notified from the AP to the STA, the notifying means notifies the STA of the AID by an AID Switch Response Action frame in the IEEE 802.11ah standard.

6. A communication device according to any one of claims 1 to 5, wherein when the AID is notified from the AP to the STA, the notification means notifies the STA of the AID after the STA connects to the AP without having the AID.

7. The communication device according to claim 1, wherein the roaming without reassociation is seamless roaming.

8. The communication device according to claim 7, wherein the seamless roaming is roaming in which negotiation for 4-way handshake and Block Ack is not performed when the STA roams from the other AP to the AP.

9. A communication device according to any one of claims 1 to 8, wherein the determination means determines to notify the STA of the AID from the other AP when the length of the period until the timing of transmitting a frame using the determined AID to the STA is less than a predetermined length in the AP.

10. A communications device that functions as an access point (AP) compliant with the IEEE 802.11 series standards, comprising: a determination means for determining whether to perform roaming without reassociation of a station (STA) connected to the AP; a transmission means for transmitting a roaming request of the STA to another AP at the roaming destination when it is determined that roaming should be performed; and a notification means for notifying the STA of an association identifier (AID) of the STA determined by the other AP and an instruction indicating that the AP will notify the AID when the communication device receives the AID from the other AP.

11. The communication device according to claim 10, wherein said transmitting means transmits to said other AP an AID used in communication between said STA and said AP.

12. The communication device according to claim 11, wherein said transmission means transmits the request to said other AP including an AID used in communication between said STA and said AP.

13. The communication device according to claim 11, wherein the transmitting means transmits to the other AP the AID used in communication between the STA and the AP, included in context information relating to the STA.

14. The communication device according to any one of claims 10 to 13, wherein the roaming without reassociation is seamless roaming.

15. The communication device according to claim 14, wherein the seamless roaming is roaming in which negotiation for a 4-way handshake and a Block Ack is not performed when the STA roams from the AP to the other AP.

16. A communications device that functions as a station (STA) conforming to the IEEE 802.11 series standard, comprising: a receiving means for receiving, when roaming from a connected first AP to a second AP without reassociation, an association identifier (AID) to be used for communication with the second AP from either the first AP or the second AP, determined by the second AP; and a communications means for communicating with the second AP using the AID.

17. The communication device according to claim 16, wherein the receiving means, when receiving the AID from the first AP, receives the AID before a connection with the second AP is established, and when receiving the AID from the second AP, receives the AID after a connection with the second AP is established.

18. The communication device according to claim 16 or 17, wherein the roaming without reassociation is seamless roaming.

19. The communication device of claim 18, wherein the seamless roaming is roaming in which negotiation for a 4-way handshake and a Block Ack is not performed when the STA roams from the first AP to the second AP.

20. A control method executed by a communication device functioning as an access point (AP) compliant with the IEEE 802.11 series standards, comprising: receiving, from another AP, a request for roaming that does not involve reassociation for a station (STA) connected to the other AP; determining, based on the received request, an association identifier (AID) for the STA and determining whether the AID will be notified to the STA from the AP or the other AP; when notifying the STA of the AID from the other AP, notifying the other AP of the AID and an instruction indicating that the AID should be transmitted from the other AP; and when notifying the STA of the AID from the AP, notifying the STA of the AID.

21. A control method executed by a communication device that functions as an access point (AP) compliant with the IEEE 802.11 series standards, comprising: determining whether to perform roaming without reassociation of a station (STA) connected to the AP; if it is determined that roaming should be performed, transmitting a roaming request of the STA to another AP at the roaming destination; and if an association identifier (AID) of the STA determined by the other AP and an instruction indicating that the AP will notify the AID are received from the other AP, notifying the STA of the AID.

22. A control method executed by a communication device functioning as a station (STA) conforming to the IEEE 802.11 series standard, comprising: when roaming from a first AP to which a connection is currently established to a second AP without reassociation, receiving an Association Identifier (AID) to be used for communication with the second AP from either the first AP or the second AP, as determined by the second AP; and communicating with the second AP using the AID.

23. A program for causing a computer to function as a communication device according to any one of claims 1 to 15.

24. A program for causing a computer to function as a communication device according to any one of claims 16 to 19.

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