Communication apparatus, control method, and storage medium

Abstract

To appropriately set or manage an AID when performing seamlessroaming.SOLUTION: Receiving, from another AP, a request for roaming without Reassociation of a station (STA) connected to the other AP, determining an AssociationIdentifier (AID) of the STA based on the reception of the request, determining which of the AP and the other AP notifies the STA of the AID, and notifying the other AP of the AID and an instruction indicating that the AID is to be transmitted from the other AP in a case where the STA is notified of the AID from the other AP; IEEE802, when the AID is notified from the AP to the STA, the AID is notified to the STA.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a roaming control technique in a wireless LAN. [Background technology]

[0002] The IEEE802.11 series of standards is known as a communication standard for wireless LANs (Local Area Networks). IEEE stands for Institute of Electrical and Electronics Engineers. Among the IEEE802.11 series of standards, the IEEE802.11be standard and its successor, the IEEE802.11bn standard, are studying methods for reducing communication delays and improving channel utilization efficiency. Patent Document 1 describes a procedure for reconfiguring a wireless link when a station (STA) roams between physically separate access points (APs). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2023 / 0380001 Summary of the Invention [Problem to be solved by the invention]

[0004] Seamless roaming technology has been studied as a technique for shortening communication interruption periods due to roaming, which allows for efficient communication by STAs. This technology eliminates the need for processes such as a 4-way handshake between the STA and the AP at the roaming destination, thereby shortening communication interruption periods. However, when roaming occurs, the AP that manages the AID (Association Identifier) ​​changes, but no study has been conducted on how to appropriately set or manage this AID in seamless roaming.

[0005] The present invention provides a method for appropriately setting or managing an AID when seamless roaming is performed. [Means for solving the problem]

[0006] A communication device according to one embodiment of the present invention is a communication device that functions as an access point (AP) compliant with the IEEE 802.11 series standard, and has: 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, based on the received request, an association identifier (AID) of the STA and determining whether the AID will be notified to the STA from the AP or the other AP; and a notifying means for, when notifying the AID from the other AP to the STA, notifying the other AP of the AID and an instruction indicating that the AID should be sent from the other AP, and when notifying the AID from the AP to the STA, notifying the STA of the AID. [Effects of the Invention]

[0007] According to the present invention, it becomes possible to appropriately set or manage AID when seamless roaming is performed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Figure 2] FIG. 2 illustrates an example of a hardware configuration of a communication device. [Figure 3] FIG. 2 illustrates an example of a functional configuration of a communication device. [Figure 4] FIG. 10 is a diagram illustrating an example of the configuration of a MAC frame. [Figure 5] FIG. 10 is a diagram illustrating an example of the configuration of a MAC frame. [Figure 6A] FIG. 10 is a diagram illustrating an example of the configuration of a MAC frame. [Figure 6B] FIG. 10 is a diagram illustrating an example of the configuration of a MAC frame. [Figure 6C] FIG. 10 is a diagram illustrating an example of the configuration of a MAC frame. [Figure 7] FIG. 10 is a diagram illustrating an example of the configuration of an AID Response element. [Figure 8] FIG. 1 is a diagram illustrating an example of the flow of communication control processing in a wireless communication system. [Figure 9] FIG. 10 is a diagram illustrating another example of the flow of communication control processing in the wireless communication system. [Figure 10] FIG. 10 is a diagram illustrating an example of the flow of processing executed in a roaming destination AP. [Figure 11] FIG. 10 is a diagram illustrating an example of the flow of processing executed in a roaming source AP. [Figure 12] FIG. 10 is a diagram illustrating an example of the flow of processing executed in an STA. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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 invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, 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.

[0010] (Terminology explanation) Some technical terms used in this embodiment will be explained below.

[0011] "Colocated": Indicates a state in which devices are physically located in the same housing (same location). For example, the term "non-colocated" indicates a state in which devices are physically located in different housings (different locations). Note that during the review process of the IEEE802.11 series standards, the term "(non-)collocated" is sometimes used, but the meaning is the same even when this term is used.

[0012] "Seamless roaming": Roaming occurs when a station (STA) switches its connection to an access point (AP) other than the one it is currently connected to. Seamless roaming refers to 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. The terms "smooth" and "SMD (Seamless Mobility Domain)" are sometimes used instead of the term "seamless." Roaming is also sometimes expressed as "transition" or "Link Switch."

[0013] "State 4": This refers to the authenticated and associated state after a successful 4-way handshake. 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 the disassociation procedure. State 2 refers to the authenticated and unassociated state.

[0014] "Context": This refers to the encryption key for unicast or multicast communication related to security, and negotiation parameters for communication procedures such as the ADDBA procedure and the SCS (Stream Classification Service) procedure. The context item 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.

[0015] (System Configuration) FIG. 1 shows an example of the configuration of a wireless communication system according to this embodiment. The 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 of standards. 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 that the AP is related to or constitutes an MLD. In the following description, affiliated AP 102 and affiliated AP 103 may be referred to as AP 102 and AP 103, respectively. AP 104 is a second access point that has the same function as 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 called a "colocated AP" because it includes two affiliated APs, 102 and 103. AP 104 may also be called a colocated AP, like AP 101, because it includes two affiliated APs, 105 and 106. Note that AP 101 and AP 104 are provided by separate housings located in different locations, and therefore can be said to be in a non-colocated relationship.

[0016] The AP 101 and the AP 104 are configured to be able to communicate with each other via a distribution system (DS107) using the functions of their respective DSAFs (Distribution System Access Functions). The DS107 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 DS107 may be configured using a wireless communication medium such as LTE (Long-Term Evolution) or WiMAX (Worldwide Interoperability for Microwave Access). The DS107 may also be configured using other wireless communication media such as a wireless LAN conforming to the IEEE 802.11 series standards.

[0017] 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 affiliated STA 109 and the affiliated STA 110, they may be referred to as "colocated 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 may be established between the affiliated AP and the affiliated STA, and multiple such links may be established, thereby allowing multiple links to be established in parallel between the AP 101 and the STAs 108.

[0018] 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 the 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 the 5 GHz and 6 GHz frequency bands in two links, respectively. This is just an example, and, for example, two of the multiple established links may use different frequency channels in the same frequency band. Furthermore, the operating frequency of at least one of the links may be the 2.4 GHz band.

[0019] In this embodiment, in the configuration of FIG. 1 , it is assumed that the STA 108 transitions from a state in which it is connected to the AP 101 by establishing two links to the AP 104 by establishing two links. Conventionally, roaming has been performed by executing a procedure involving reassociation. In this procedure, the AP at the roaming destination 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 execution of the disassociation procedure transitions the STA's state to state 2, and a procedure is required to reset the STA to state 4. In contrast, in seamless roaming, roaming using a procedure called link reconfiguration is being considered. This procedure allows the STA to roam while maintaining state 4. However, in this procedure, it is not necessarily clear how to set an AID for the roaming STA. In consideration of these circumstances, this embodiment provides an (efficient) AID setting procedure for seamless roaming.

[0020] (Device configuration) 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.

[0021] The storage unit 201 is configured to include 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 be configured to 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 be configured to include storage media such as a plurality of memories.

[0022] 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 in cooperation with an operating system and the computer program stored in the storage unit 201. 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 an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a field-programmable gate array (FPGA), etc.

[0023] 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.

[0024] 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 performs 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.

[0025] The communication unit 206 executes control for wireless communication compliant with the IEEE 802.11 series of standards. The communication unit 206 may control, for example, wireless communication compliant with the IEEE 802.11be standard, the IEEE 802.11bn standard, or successor standards thereof, or 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 standards such as the NFC standard and the Bluetooth standard in addition to the IEEE 802.11 series of standards, the communication unit 206 may 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 compatible with those communication standards may be provided.

[0026] Antenna 207 is an antenna capable of detecting and emitting radio waves in, for example, the 2.4 GHz band, the 5 GHz band, and the 6 GHz band. Antenna 207 may be configured to be capable of communication in the same frequency band. In this case, 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 according to the number of available spatial streams. If the communication device has multiple antennas, it may have a communication unit 206 corresponding to each antenna. Antenna 207 may be provided separately from communication unit 206, or may be configured together with communication unit 206 as a single module.

[0027] FIG. 3 illustrates an example of a 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 block. 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.

[0028] The wireless LAN control unit 301 includes circuits for transmitting and receiving wireless signals to and from 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 a basic service set (BSS) managed by the AP. For example, the AID management unit 303 of the AP assigns an AID to a STA when connecting with 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 as needed through communications with the other device. The security control unit 304 executes a robust security network association (RSNA) 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.

[0029] 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 programs 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 antenna functions.

[0030] (Frame composition) Next, an example of the configuration of a MAC (Medium Access Control) frame conforming to the IEEE 802.11 series standards 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 relevant to this embodiment, and the MAC frame naturally includes fields conforming to the IEEE 802.11 series standards (not shown).

[0031] Frame Control 401, specifically, is configured with 10 subfields and is a field that stores information indicating the frame type (e.g., Management / Control / Data) and the direction in which the frame is transmitted. Address 402 is configured with up to four fields. Depending on the MAC frame type, addresses such as the BSSID (Basic Service Set IDentifier), source, and destination are set in Address 402. Note that Address 402 is omitted for frames of a certain 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 Frame Body 404. Note that management frames include, for example, frames such as Beacon, Probe Request / Response, and Action. FCS 405 is the final field of the MAC frame. Note that FCS stands for Frame Check Sequence.

[0032] 5(A) to 5(C) 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," which indicates Management, and B7B6B5B4 is set to "1101." Note that the order of the bit numbers in the Frame Control 401 and the explanation of the values ​​of each bit is reversed in accordance with the notation in the IEEE 802.11 series standards.

[0033] 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 the time of IEEE802.11be Draft 5.01, 38 types of classifications have been defined, ranging from Code=0 Spectrum Management to Code=37 Protected EHT, as shown in Fig. 5(B). Note that Fig. 5(B) shows, as an example, an example in which Code=38 and Code=39 for UHR (Ultra High Reliability) and Protected UHR for IEEE802.11bn, which is currently under standardization consideration, have been added.

[0034] 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 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 (described later), "10" is stored in Action ID 503. Similarly, in the case of Link Reconfiguration Request, "11" is stored in Action ID 503, and in the case of Link Reconfiguration Response, "12" is stored in Action ID 503. Dialog Token 504 is information used to identify the procedure when multiple Action procedures have been established. Element 505 is an information element in which various information is stored.

[0035] 6A to 6C, 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. Note that 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.

[0036] In (A) of Fig. 6A, Element ID 601 and Element ID Extension 603 are identifiers for indicating the type of element. As shown in (B) of Fig. 6A, 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 contains information common to established links. Per-STA Profile 606 will also be described in detail later.

[0037] As shown in (A) of FIG. 6B, Multi-Link Control 604 includes three subfields: a 3-bit Type 611, a 1-bit Reserved 612, and a 12-bit Presence Bitmap 613. Type 611 indicates the use of the Multi-Link element, and currently, values ​​from 0 to 4 are defined, as shown in (B) of FIG. 6B. When setting up a multi-link, i.e., 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. A Type 611 value of "2" indicates that this element is related to reconfiguration. Reconfiguration can add or delete links after multi-link setup. Presence Bitmap 613 is used to indicate the presence or absence of various pieces of information in the Common Info 605 field, each with one bit. Note that the information that can be included in the Common Info 605 field is defined by the value of Type 611, and the content of Presence is determined accordingly.

[0038] In the following, an example will be described in which the value of Type 611 is set to "2" (Reconfiguration). In this case, Presence Bitmap 613 includes six bits, from MLD MAC Address Present 614 to AID Present 619, as shown in (A) of FIG. 6B. Presence Bitmap 613 also includes six bits, Reserved 620 to 625, in which one code is assigned to one bit in preparation for future expansion. The six bits, from MLD MAC Address Present 614 to AID Present 619, respectively correspond to MLD MAC Address 632 to AID 637 in Common Info 605 shown in (C) of FIG. 6B. MLD MAC Address Present 614 to AID Present 619 are 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 identified by the combination of the MLD MAC Address 632 and the Link ID. The EML Capabilities Present 615 is set to "1" if the EML Capabilities 633 exists. The MLD Capabilities And Operations Present 616 is set to "1" if the MLD Capabilities And Operations 634 exists.

[0039] 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 may be performed by AP 101 and AP 104 working together. The collaborative operation of AP 101 and AP 104 is controlled by roaming control unit 306. In either case, SAP is a MAC layer function or MAC entity that exists when multiple APs that realize the seamless roaming function are treated as a single virtual roaming AP MLD.

[0040] AP MLD Roaming ID 636 stores information for identifying an AP MLD included in a group of AP MLDs that have established a seamless roaming relationship. If 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. If this information is included in Common Info 605, AID Present 619 is set to "1". In this embodiment, AIDs are assigned on an AP MLD basis and are specified in Common Info.

[0041] Next, the Per-STA Profile 606 will be described with reference to Fig. 6C. 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 a plurality of Per-STA Profile 606 fields may be referred to as a Link-Info field.

[0042] In the Per-STA Profile 606, Data 643 includes an STA Control field 644, STA Info, and an STA Profile. The STA Info includes an STA Info Length 645 and STA Info 646. The STA Profile includes Capability Information 647, an Element 648, and a Non-Inheritance element 649. The STA Profile is not particularly related to the processing according to this embodiment, and therefore a detailed description thereof will be omitted.

[0043] 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, among 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 (C) of Fig. 6C. The STA Info sequence 646 will be described in detail later.

[0044] 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 identifies the affiliated AP 102, affiliated AP 105, 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 about the link. That is, the value stored in the Complete Profile 651 specifies whether the STA Info contains partial information about the link or all of the information about the link.

[0045] MAC Address present 652 is set to "1" if STA MAC Address 662 is present in STA Info sequence 646, and is set to "0" if it is not present. AP Removal Timer Present 653 is set to "1" if AP Removal Timer 663 is present in STA Info sequence 646, and is set to "0" if it is not present. Reconfiguration Operation Type 654 is a 4-bit field, and specifies the type of reconfiguration procedure. (B) of FIG. 6C shows the correspondence between the values ​​set in Reconfiguration Operation Type 654 and their meanings. For example, in the case of seamless roaming, setting the value of Reconfiguration Operation Type 654 to "3" specifies a procedure in which the roaming source link is deleted. Also, setting the value of Reconfiguration Operation Type 654 to "2" specifies a procedure in which the roaming destination link is added. When a link is added, all information related to that link is included in the frame, and the value of Complete Profile 651 is set accordingly.

[0046] Operation Parameters Present 655 is set to "1" if Operation Parameters 664 are present in the STA Info sequence 646, and is set to "0" if they are 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.

[0047] 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.

[0048] Fig. 7 shows an example of the configuration of an AID Response element introduced in the IEEE802.11ah standard. This element has an Element ID 701 value set to "211". Length 702 stores a value indicating the length of this element. AID / Group AID 703 is a two-octet field in which an AID is stored. AID Switch Count 704 is set to a value specifying the period until the AP assigns a new AID to the STA. AID Response Interval 705 stores information indicating the period during which the STA should be active during association.

[0049] 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 executable.

[0050] 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.

[0051] (Communication processing flow) 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 from which STA 108 roams (source AP), and AP 104 is the AP to which STA 108 roams (target AP).

[0052] 8, first, AP101 and AP104 search for other APs in the vicinity that are capable of seamless roaming (S801). Here, it is assumed that AP101 discovers AP104, and AP104 discovers AP101. Then, AP101 broadcasts information about seamless roaming (S802). AP101 broadcasts information about seamless roaming by notifying its capabilities using a capabilities element in a management frame or by notifying its operating status using an operation element. Note that AP104 also broadcasts similar information. Here, the information about seamless roaming may include, for example, information that the own device (AP101 or AP104) is capable of seamless roaming, and information about surrounding APs that are capable of seamless roaming.

[0053] 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 exchanging an Association Request and an Association Response, in which the value of Type 611 of the Multi-Link element is set to "0" (Basic). This sets up a multi-link between the AP 101 and the STA 108. Note that the information included in the Presence Bitmap 613 and Common Info 605 of the Multi-Link element in this case is different from that included in the Reconfiguration in which Type 611 is "2." That is, the Multi-Link element in this case includes a Link ID, an AP MLD ID, MLD Capabilities and Operations, and the like. The MLD Capabilities and Operations includes 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 an affiliated AP that supports seamless roaming, for example. The STA 108 negotiates Stream Classification Service (SCS) with the AP 101 to which it is connected (S804) to ensure quality of service (QoS) for the application it is running. The STA 108 also negotiates Block Ack with the AP 101 (S805). After completing these negotiations, the STA 108 performs data communication (S806).

[0054] Then, while connected, the AP 101 and the STA 108 notify each other of information that can be used to determine the need for 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 need for roaming based on the exchanged information. For 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.

[0055] When the AP 101 or the STA 108 determines that roaming is necessary, it transmits a Link Reconfiguration Notify to the peer device (the STA 108 for the AP 101, and the AP 101 for the STA 108) (S808). The Link Reconfiguration Notify is an Action frame with the above-mentioned Action ID 503 set to "10," and also indicates a recommendation for reconfiguring the multi-link. The Link Reconfiguration Notify includes one Per-STA Profile for each affiliated AP. The (Basic) Multi-Link element used when establishing the 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 identified by the MAC address of AP 104 and Link ID=0, and the link corresponding to AP 106 can be identified 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 AP 101 to STA 108 or from STA 108 to AP 101. However, since this frame may be transmitted from either AP 101 or STA 108, the transmission and reception of this frame are indicated by a bidirectional arrow in FIG. 8. This frame may also 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 a (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).

[0056] Thereafter, the STA 108 transmits a link reconfiguration request to the AP 101 (S810). This is an Action frame with Action ID 503 set to "11." The MAC address of the STA 108 is set in the MLD MAC Address of Common Info in the Multi-Link element of this frame. In this sequence, for example, it is assumed that the STA 108 accepts the link addition and deletion notified by the Link Reconfiguration Notify from the AP 101 and decides to perform roaming. Note that if the STA 108 desires to roam to another destination, the STA 108 transmits a Multi-Link probe request before S810. Then, the AP 101 can notify the STA 108 of information about other APs by a Multi-Link probe response. At this time, the AP 101 transmits information about other APs with which a seamless roaming relationship has been established in S809, by including the information about the other APs in the Multi-Link probe response.

[0057] The AP 101 transmits a Seamless Roaming Request to the AP 104, the roaming destination determined by the procedures up to S810 (S811). This frame is an Action frame newly defined in this embodiment. Note that the AP 104 may transmit a response frame to the AP 101 upon receiving this frame. 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 performed in S804 and S805. As will be described later, the AID can be independently determined by the AP 104, and therefore the AID information does not need to be included in the context notified from the AP 101. The AID may also be included in, for example, a Seamless Roaming Request, and in this case, the AID information does not need to be included in the context.

[0058] The AP 104 determines an AID value and determines a notification method (S814). At this time, the AP 104 may decide to continue using the AID notified by the AP 101. Furthermore, the AP 104 determines the notification method, whether the AP 104 itself notifies the STA 108 of the AID, 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 AID information newly assigned by the AP 104 is included in this frame.

[0059] 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 AID information determined by the AP 104 included. Here, the 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 that is newly defined in this embodiment. Then, upon receiving this notification, if the AP 104 holds data addressed to the STA 108, the AP 104 transmits a Beacon containing a TIM (Traffic Indication Message) bitmap indicating the presence of such data. The STA 108 then switches its communication partner to the AP 104 and continues communication.

[0060] 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.

[0061] In the above processing example, an example has been described in which the AP 101 notifies the AID determined by the AP 104. Next, an example in which the AP 104 itself notifies the STA 108 of the AID determined by the AP 104 will be described with reference to Fig. 9. 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.

[0062] 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 AID as not yet 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 that has switched the link 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 the Category Code value set to "22," and may include the AID Switch element described above. Also, 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 a Beacon containing a TIM bitmap if there is data addressed to the STA 108, as in FIG. 8 (S818).

[0063] 9, the STA 108 receives an AID from the roaming destination AP 104. In this case, as described above, the STA 108 receives a Link Reconfiguration Response and becomes connected to the roaming destination AP 101, and then receives notification of the AID, and is able to communicate using that AID.

[0064] As shown in FIGS. 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 by 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 AID managed by the AP 104. Also, if the STA 108 cannot manage another AID while maintaining connection with the AP 108 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 from either the AP 101 or the AP 104 whether the AID to be used for communication with the AP 104 after roaming should be notified. Also, the AP 101 may notify the AID when the AID does not change before and after roaming, and the AP 104 may notify the AID when the AID changes. Furthermore, if the period until the transmission timing of a Beacon including a TIM in the roaming destination AP 104 is short, the AP 101 may notify the AID as shown in FIG. 8 , and if the period is long, the AP 104 may notify the AID as shown in FIG. 9 . This allows the AP 104 to quickly notify the STA 108 of the AID via the AP 101 when the time for the AP 104 to transmit a Beacon including a TIM is approaching. The AP to notify the AID after roaming may also be determined based on other criteria (e.g., the capabilities or communication conditions of the STA 108). This prevents the STA 108 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 this determination, along with the context, may be notified from the AP 101 to the AP 104.

[0065] Next, an example of the flow of processing executed by the AP (AP 104) of the roaming destination will be described with reference to Fig. 10. Note that the flow of processing shown below is an example, and the order of processing steps may be changed as necessary, or some steps may be omitted. Furthermore, further steps may be added.

[0066] This process is executed in a state where the establishment of a seamless roaming relationship with the roaming source AP (AP101) 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 (AP101) (S1001). Here, it is assumed that the AP 104 unconditionally accepts the roaming request received in S1001 without transmitting a response. However, this is just an example, and the AP 104 may check the contents of the request and determine whether or not to accept the request, and transmit a response to the AP 101 according to the result of the determination.

[0067] 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 as context information separately from the request 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 in the context, the process of S1006, which will be described later, 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 the AID needs to be changed (YES in S1003), it determines an AID to be newly assigned to the STA 108 (S1004). If the AP 104 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). Note that the context may include, for example, information related to QoS and BA negotiation.

[0068] The AP 104 decides to use the notified AID as is, or determines a new AID, and then decides whether to notify the AID itself or have the roaming source AP 101 notify it. The AP 104 makes this determination, for example, depending on the length of time until the transmission timing of a Beacon (S1007, S1008, S1009). For example, if the length of the period until the transmission timing of a Beacon including 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 length of the period until the transmission timing of a Beacon including 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 AP101, which is the source AP of roaming, or AP104, which is the target AP of roaming, may be determined based on other criteria.

[0069] 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). Then, 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 using, for example, 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.

[0070] Note that the determination in S1007 may take into consideration the transmission timing of frames other than Beacons. 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. Note that, in the case of the IEEE 802.11ax standard, the STA_ID is the lowest 11 bits of the AID.

[0071] Next, an example of the flow of processing executed by the roaming source AP 101 will be described with reference to Fig. 11. Note that the flow of processing shown below is an example, and the order of processing steps may be changed as necessary, or some steps may be omitted. Furthermore, further steps may be added.

[0072] This process is executed after the establishment of a seamless roaming relationship with the roaming destination AP (AP 104) has been completed in S809. The AP 101 transmits information about seamless roaming using a management frame (S1101). The AP 101 sends this information, for example, as information elements of capabilities (UHR Capabilities) and operation (UHR Operation) in a Beacon or a Probe Response, which is a response to a Probe Request from the STA. The AP 101 then establishes a connection with the STA 108 (S1102). This connection procedure also includes negotiation regarding whether the AP 101 will enable seamless roaming for the STA 108. The AP 101 may also notify the STA 108 of a list of candidate APs for roaming during this connection procedure. Then, the AP 101 accepts the QoS request of the STA 108 by executing the SCS procedure with the STA 108 (S1103), and further negotiates a Block Ack with the STA 108 (S1104). The Block Ack negotiation is performed by sending and receiving an ADDBA request and an ADDBA response.

[0073] Thereafter, the AP 101 determines whether or not roaming of the currently connected STA 108 is necessary (S1105). For example, the AP 101 may determine that roaming of the STA 108 is necessary when the wireless quality or throughput, such as a receive signal strength indicator (RSSI) of a frame from the STA 108, falls below a predetermined value. The AP 101 may receive information on the wireless quality or 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, if the STA 108 determines that roaming is necessary, the AP 101 receives a Link Reconfiguration Notify from the STA 108 (S1106). If the AP 101 transmits a Link Reconfiguration Notify to the STA 108, the AP 101 may transmit information on candidate APs as roaming destinations.

[0074] Thereafter, when AP 101 receives a Reconfiguration Request from STA 108 (S1107), it transmits a roaming request (Seamless Roaming Request) to the roaming destination AP 104 (S1108). AP 101 also transfers data addressed to STA 108 that is stored in its own buffer to AP 104 (S1109), and transmits the context of STA 108 (S1109). Note that AP 101 retains the buffered data and context without discarding them until roaming is complete.

[0075] 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 from 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), the AP 101 transmits a Link Reconfiguration Response without an AID value to the STA 108 (S1114). The AP 101 also transmits a Link Reconfiguration completion notification to the AP 104 (S1115). Then, upon completion of the process of S1115, the AP 101 determines that roaming is complete, 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.

[0076] 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 processing steps may be changed as necessary, or some steps may be omitted. Furthermore, further steps may be added.

[0077] The STA 108 first 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 the SCS procedure with the AP 101 to set QoS (S1202) and negotiates Block Ack (S1203). Thereafter, the STA 108 continuously determines whether roaming is necessary while communicating with the AP 101 (S1204). Note that, as described above, the determination of whether roaming is necessary is also made by the AP 101, and roaming is performed depending on whether either the AP 101 or the STA 108 determines that roaming is necessary. Here, 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). This allows the STA 108 to obtain the AP MLD MAC address of the AP to roam to, which is included in the Link Reconfiguration Response. The STA 108 also determines whether AID information is included in the Link Reconfiguration Response (S1208). If the Link Reconfiguration Response does not contain AID information (NO in S1208), the STA 108 waits for reception of notification of AID information from the AP 104 of the roaming destination (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). Furthermore, if the Link Reconfiguration Response contains AID information (YES in S1208), the STA 108 updates the AID it manages using the AID information (S1210). Then, the STA 108 starts receiving a frame that specifies the updated AID and contains information addressed to the STA 108 (S1211).

[0078] 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 to 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.

[0079] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0080] (Summary of the embodiment) At least some of the above-described embodiments can be summarized as follows. (Item 1) A communication device that functions as an access point (AP) conforming to the IEEE 802.11 series standard, A receiving means for receiving a roaming request from another AP without reassociation of a station (STA) connected to the other AP; A determination means for determining an association identifier (AID) of the STA based on the received request, and determining whether the AID is to be notified to the STA from the AP or the other AP; a notification means for notifying the other AP of the AID and an instruction indicating that the AID should be transmitted from the other AP when the AID is notified from the other AP to the STA, and for notifying the STA of the AID when the AID is notified from the AP to the STA; A communication device comprising: (Item 2) The communication device described in item 1 is characterized in that, when the decision means receives from the other AP an AID used for communication between the other AP and the STA, it decides whether to continue using the AID or to set a new AID. (Item 3) 3. The communication device according to item 2, wherein the receiving means receives the request including an AID used in communication between the other AP and the STA. (Item 4) 3. The communication device according to item 2, wherein the receiving means receives context information relating to the STA including an AID used in communication between the other AP and the STA. (Item 5) The communication device described in any one of items 1 to 4, characterized in that when the AID is notified from the AP to the STA, the notification means notifies the AID to the STA using an AID Switch Response Action frame in the IEEE 802.11ah standard. (Item 6) The communication device described in any one of items 1 to 5, characterized in that 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. (Item 7) 7. The communication device according to any one of items 1 to 6, wherein the roaming without reassociation is seamless roaming. (Item 8) 8. The communication device according to item 7, 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 other AP to the AP. (Item 9) The communication device described in any one of items 1 to 8, characterized in that the decision means decides to notify the STA of the AID from the other AP when the period length until the timing of transmitting a frame using the determined AID to the STA is shorter than a predetermined length in the AP. (Item 10) A communication device that functions as an access point (AP) conforming to the IEEE 802.11 series standard, a determination means for determining whether to perform roaming without reassociation of a station (STA) currently connected to the AP; a transmitting means for transmitting the roaming request of the STA to another AP as a roaming destination when it is determined that the roaming is to be performed; a notification means for notifying the STA of an association identifier (AID) determined by the other AP when the other AP receives an instruction indicating that the AP notifies the AID; A communication device comprising: (Item 11) Item 11. The communication device according to item 10, wherein the transmitting means transmits to the other AP an AID used in communication between the STA and the AP. (Item 12) Item 12. The communication device according to item 11, wherein the transmitting means includes an AID used in communication between the STA and the AP in the request and transmits the request to the other AP. (Item 13) The communication device described in item 11, characterized in that the transmitting means includes the AID used in communication between the STA and the AP in context information related to the STA and transmits it to the other AP. (Item 14) 14. The communication device according to any one of items 10 to 13, wherein the roaming without reassociation is seamless roaming. (Item 15) The communication device described in item 14, characterized in that the seamless roaming is roaming in which negotiation for 4-way handshake and Block Ack is not performed when the STA roams from the AP to the other AP. (Item 16) A communication device that functions as a station (STA) conforming to the IEEE 802.11 series standard, a receiving means for receiving, when roaming from a first AP to which a connection is currently made to a second AP without reassociation, an association identifier (AID) to be used for communication with the second AP from one of the first AP and the second AP, which is determined by the second AP; a communication means for communicating with the second AP using the AID; A communication device comprising: (Item 17) Item 17. The communication device according to item 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. (Item 18) 18. The communication device according to item 16 or 17, wherein the roaming without reassociation is seamless roaming. (Item 19) The communication device described in item 18, characterized in that the seamless roaming is roaming in which negotiation for 4-way handshake and Block Ack is not performed when the STA roams from the first AP to the second AP. (Item 20) A control method executed by a communication device functioning as an access point (AP) conforming to the IEEE 802.11 series standard, comprising: receiving a roaming request from another AP without reassociation of a station (STA) connected to the other AP; Based on the reception of the request, determining an association identifier (AID) of the STA, and determining whether the AID is to be notified to the STA from the AP or the other AP; When notifying the AID from the other AP to the STA, notify the other AP of the AID and an instruction indicating that the AID should be transmitted from the other AP, and when notifying the AID from the AP to the STA, notify the STA of the AID; A control method comprising: (Item 21) A control method executed by a communication device functioning as an access point (AP) conforming to the IEEE 802.11 series standard, comprising: determining whether to perform roaming without reassociation of a station (STA) currently connected to the AP; When determining that the roaming is to be performed, transmitting the roaming request of the STA to another AP of a roaming destination; When receiving from the other AP an association identifier (AID) of the STA determined by the other AP and an instruction indicating that the AP notifies the AID, notifying the AID to the STA; A control method comprising: (Item 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 one of the first AP and the second AP, the association identifier being determined by the second AP; communicating with the second AP using the AID; A control method comprising: (Item 23) 16. A program for causing a computer to function as the communication device according to any one of items 1 to 15. (Item 24) 20. A program for causing a computer to function as the communication device according to any one of items 16 to 19.

[0081] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0082] 301: Wireless LAN control unit, 303: AID management unit, 306: Roaming control unit

Claims

1. A communication device that functions as an access point (AP) conforming to the IEEE 802.11 series standard, A receiving means for receiving a roaming request from another AP without reassociation of a station (STA) connected to the other AP; a determining means for determining an association identifier (AID) of the STA based on receiving the request, and determining whether the AID is to be notified to the STA from the AP or the other AP; a notification means for notifying the other AP of the AID and an instruction indicating that the AID should be transmitted from the other AP when the AID is to be notified from the other AP to the STA, and for notifying the STA of the AID when the AID is to be notified from the AP to the STA; A communication device comprising:

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

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

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

5. 2. The communication device according to claim 1, wherein the notifying unit, when notifying the AID from the AP to the STA, notifies the STA of the AID by an AID Switch Response Action frame in the IEEE 802.11ah standard.

6. 2. The communication device according to claim 1, 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. 8. The communication device according to claim 7, 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 other AP to the AP.

9. The communication device according to claim 1, characterized in that the determination means determines to notify the STA of the AID from the other AP when the period until the timing of transmitting a frame using the determined AID to the STA is shorter than a predetermined period in the AP.

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

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

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

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

14. The communication device according to claim 10, wherein the roaming without reassociation is seamless roaming.

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

17. 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, wherein the roaming without reassociation is seamless roaming.

19. 19. The communication device according to 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) conforming to the IEEE 802.11 series standard, comprising: receiving a roaming request from another AP without reassociation of a station (STA) connected to the other AP; determining an association identifier (AID) of the STA based on receiving the request, and determining whether the AID will be notified to the STA from the AP or the other AP; When notifying the AID from the other AP to the STA, 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 AID from the AP to the STA, notifying the STA of the AID; A control method comprising:

21. A control method executed by a communication device functioning as an access point (AP) conforming to the IEEE 802.11 series standard, comprising: determining whether to perform roaming without reassociation of a station (STA) currently connected to the AP; When it is determined that the roaming is to be performed, transmitting a request for the roaming of the STA to another AP as a roaming destination; When receiving, from the other AP, an association identifier (AID) of the STA determined by the other AP and an instruction indicating that the AP notifies the AID, notifying the STA of the AID; A control method comprising:

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 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, the association identifier being determined by the second AP; communicating with the second AP using the AID; A control method comprising:

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

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

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