Method and system for managing buffered downlink data during seamless roaming in wireless communication network

Abstract

The present disclosure relates to a method and system for managing buffered downlink data during seamless roaming in a wireless communication network. The method includes detecting a roaming request initiated by a client device connected to a serving access point multi-link device, indicating an intended transition to a target access point multi-link device within a seamless mobility domain. Upon detection, a predefined roaming procedure is initiated, wherein the roaming procedure is dynamically selected based on an evaluated rate of degradation in one or more roaming-related key performance indicators associated with the ongoing connection. During execution of the roaming procedure, buffered downlink data is managed by coordinating controlled transfer of the buffered data from the serving access point multi-link device to the target access point multi-link device. The buffered data is preserved and made available at the target access point to ensure continuity of downlink data transmission during the roaming transition.

Description

METHOD AND SYSTEM FOR MANAGING BUFFERED DOWNLINK DATA DURING SEAMLESS ROAMING IN WIRELESS COMMUNICATION NETWORK

[0001] The present disclosure relates to a wireless communication system (or a mobile communication system). More specifically, The present disclosure relates, in general, to the field of data forwarding communication protocols. More specifically, embodiments of the present disclosure relate to a method and system for managing buffered downlink data during seamless roaming in a wireless communication network.

[0002] Wireless local area network (WLAN) is a technology that allows users to access the internet through mobile devices or laptops within a certain distance from the location where an access point (AP) is installed. WLAN systems are evolving to meet various objectives, including improved transmission rates, increased bandwidth, enhanced reliability, reduced errors, and decreased latency. The Institute of Electrical and Electronics Engineers (IEEE) publishes 802.11 standard specifications for WLAN systems, and the Wi-Fi Alliance refers to technologies based on the 802.11 standard specifications as WiFi (or Wi-Fi, Wireless Fidelity).

[0003] Wi-Fi technology has evolved through several generations of 802.11 standards. For example, the 802.11ac standard document addresses improvements for VHT (very high throughput), the 802.11ax standard document addresses improvements for HE (high efficiency), and the 802.11be standard document addresses improvements for EHT (extreme high throughput).

[0004] Meanwhile, with the popularization of terminals, wireless LANs, which have potential as open wireless networks, are rapidly expanding, and Wi-Fi is being used to provide high-speed data services throughout cities, including schools, airports, hotels, and offices. In addition, technologies for providing an improved wireless communication environment in wireless LAN systems are being discussed, and various technologies are being proposed and researched in response to demands for further improving the reliability of wireless LAN systems.

[0005] The background information hereinbelow relates to the present disclosure but is not necessarily prior art.

[0006] Seamless roaming in Wi-Fi 8 Ultra High Reliability (UHR) systems requires the station (STA) to remain authenticated and associated while moving between access point multi-link devices (AP MLDs). As roaming triggers become more frequent due to fluctuating RSSI / SINR conditions, ensuring continuity of downlink (DL) buffered data becomes increasingly important. Buffered packets, often critical for applications such as video streaming or TCP-based transfers, must be preserved and delivered without interruption. The growing demand for stable high-speed connectivity and the expansion of multi-link architectures reinforce the need for robust mechanisms that protect session context and minimize data loss during handovers between serving and target AP MLDs.

[0007] More specifically, seamless mobility architectures such as the Seamless Mobility Domain (SMD) introduce different roaming variants that rely either on distinct MAC-SAP interfaces for AP MLDs or a unified MAC-SAP shared across the domain. These architectural differences create dependencies on how context transfer, DS mapping updates, and buffer preservation are performed. With roaming events increasingly driven by rapid changes in RF conditions, existing procedures often struggle to handle real-time forwarding of DL buffered data. As a result, the absence of clearly defined data-forwarding rules in current drafts introduces ambiguity similar to that observed in prior roaming frameworks.

[0008] Furthermore, roaming behaviors vary across scenarios depending on how quickly the serving AP’s signal degrades. Under normal conditions, systems may complete signaling and retrieve buffered data. Under fast drops, the time available for buffer transfer is limited, requiring alternative mechanisms to preserve data before AP loss. In panic cases, the serving AP connection may terminate before signaling completes, forcing the STA to immediately reconnect to the target AP with minimal retained context. These differing conditions highlight non-uniformity in buffer handling and underscore the need for standardized fallback approaches.

[0009] Handling buffered data is essential for ensuring uninterrupted user experience during roaming. When buffers are not efficiently transferred or preserved, the STA may experience data loss, increased latency, or playback interruptions. While various embodiments propose copying buffered data between APs or to an SMD-level shared buffer, unregulated or poorly timed operations may lead to inefficiencies. Without structured rules for signaling and data flow, systems may also experience unnecessary retransmissions, reduced throughput, or additional processing overhead, impacting real-time and high-reliability applications.

[0010] Therefore, there is a need for a well-defined solution that synchronizes roaming signaling, buffer protection, and context transfer across different drop scenarios.

[0011] This summary is provided to introduce a selection of concepts, in a simplified format, which is further described in detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention nor is it intended for determining the scope of the invention.

[0012] In an embodiment, the present disclosure discloses a method for managing buffered downlink (DL) data during seamless roaming in a wireless communication network. The method comprises detecting a roaming request initiated by a client device connected to a serving access point multi-link device (AP MLD) to initiate a transition to a target AP MLD within a seamless mobility domain (SMD). The method also comprises initiating a predefined roaming procedure in response to the detected roaming request. The predefined roaming procedure is selected based on a rate of degradation detected in at least one roaming-related key performance indicators (KPI). The method further comprises managing the buffered downlink data between the serving AP MLD and the target AP MLD for the initiated roaming procedure.

[0013] In another embodiment, the rate of degradation of at least one roaming-related key performance indicators (KPI) is selected from a group consisting of: normal KPI drop, fast KPI drop and rapid KPI drop.

[0014] In yet another embodiment, the at least one roaming-related KPI comprises at least one of: Received Signal Strength Indicator (RSSI) and Signal to Interference and Noise Ratio (SINR).

[0015] In still another embodiment, when the predefined roaming procedure is initiated for the normal KPI drop, the method further comprises copying, by the serving AP MLD, buffered DL data to a buffer in the target AP MLD while continuing transmission to the client device. Further, the method comprises deactivating, by the serving AP MLD, DL data transmission to the client device upon completion of copying and transmitting, by the serving AP MLD, a notification for context update about last acknowledged (ACKed) sequence number (SN) of buffered data being transmitted towards client device, to the target AP MLD.

[0016] In yet another embodiment, when the predefined roaming procedure is initiated for the normal KPI drop, the method further comprises copying, by the serving AP MLD, the buffered DL data to a buffer in the target AP MLD and indicating target AP MLD to initiate transmission of data towards client device in parallel to copying of buffered DL data in the target AP MLD and deleting, by the serving AP MLD, communication link with the client device and resuming transmission of data towards client device from the target AP MLD.

[0017] In still another embodiment, when the predefined roaming procedure is initiated for the fast KPI drop, the method further comprises copying, by the serving AP MLD, the DL buffered data by the serving AP MLD using SMD level MAC buffer. Further, while copying the DL buffered data, the serving AP MLD and the target AP MLD are engaged in data session context transfer and Distributed System mapping change. The method also comprises transmitting, by the serving AP MLD, a message to the client device. The message includes roaming response and a message for deletion of communication link between the client device and the service AP MLD. Thereafter, the method comprises simultaneously transmitting, by the serving AP MLD, message to the target AP MLD to fetch data buffer from the SMD level MAC buffer in order to resume DL data buffer transmission towards the client device.

[0018] In yet another embodiment, the method comprises regulating copying of DL buffered data using SMD level MAC buffer via a standard validity timer (Tv).

[0019] In still embodiment, the client device includes a cause indicator in the roaming request. The cause indicator indicates the at least one roaming-related KPI responsible for fast degradation of the KPIs.

[0020] In yet another embodiment, when the predefined roaming procedure is initiated for the rapid KPI drop, the method further comprising transmitting a roaming request directly from the client device to the target AP MLD. The roaming request includes serving AP MLD information and a serving AP MLD identifier indicating association of the client device with the serving AP MLD.

[0021] In still another embodiment, the method further comprises transmitting, by the target AP MLD, a STA Context Request to the serving AP MLD including the client device's previous association ID and transmitting, by the serving AP MLD, a STA Context Response to the target AP MLD including data context of the client device.

[0022] In yet another embodiment, the method further comprises transmitting, by the target AP MLD, a roaming response to the client device, receiving, by the target AP MLD, remaining buffered data from the serving AP MLD and resuming, by the target AP MLD, data transmission towards the client device.

[0023] In still another embodiment, the method also comprises transmitting a target access point identifier as part of the roaming request to indicate the target AP MLD to which the client device seeks to roam.

[0024] In still another embodiment, the method further comprises transmitting an association identifier of the client device along with transmission of serving AP MLD identifier to enable the target AP MLD for requesting context information about the associated client device to the serving AP MLD.

[0025] In an embodiment, a system for managing buffered downlink (DL) data during seamless roaming in a wireless communication network is disclosed. The system comprises a memory and at least one processor communicatively coupled to the memory. The at least one processor is configured to detect a roaming request initiated by a client device connected to a serving access point multi-link device (AP MLD) to initiate a transition to a target AP MLD within a seamless mobility domain (SMD), initiate a predefined roaming procedure in response to the detected roaming request. The predefined roaming procedure is selected based on a rate of degradation detected in at least one roaming-related key performance indicators (KPI). Further, the at least one processor is configured to manage the buffered downlink data between the serving AP MLD and the target AP MLD for the initiated roaming procedure.

[0026] In another embodiment, the rate of degradation of the at least one roaming-related key performance indicators (KPI) is selected from a group consisting of: normal KPI drop, fast KPI drop and rapid KPI drop.

[0027] In yet another embodiment, the at least one roaming-related KPI comprises at least one of: Received Signal Strength Indicator (RSSI) and Signal to Interference and Noise Ratio (SINR).

[0028] In still another embodiment, when the predefined roaming procedure is initiated for the normal KPI drop, the at least one processor is further configured to copy, by the serving AP MLD, buffered DL data to a buffer in the target AP MLD while continuing transmission to the client device. Further, the at least one processor is configured to deactivate, by the serving AP MLD, DL data transmission to the client device upon completion of copying. The at least one processor is further configured to transmit, by the serving AP MLD, a notification for context update about last acknowledged (ACKed) sequence number (SN) of buffered data being transmitted towards client device, to the target AP MLD.

[0029] In yet another embodiment, when the predefined roaming procedure is initiated for the normal KPI drop, the at least one processor is further configured to copy, by the serving AP MLD, buffered DL data to a buffer in the target AP MLD and indicating target AP MLD to initiate transmission of data towards client device in parallel to copying of buffered DL data in the target AP MLD and delete, by the serving AP MLD, communication link with the client device and resuming transmission of data towards client device from the target AP MLD.

[0030] In still another embodiment, when the predefined roaming procedure is initiated for the fast KPI drop, the at least one processor is further configured to copy, by the serving AP MLD, the DL buffered data by the serving AP MLD using SMD level MAC buffer. Also, while copying the DL buffered data, the service AP MLD and the target AP MLD are engaged in data session context transfer and Distributed System mapping change, transmit, by the serving AP MLD, a message to the client device. The message includes roaming response and a message for deletion of communication link between the client device and the service AP MLD, and simultaneously transmit, by the serving AP MLD, message to the target AP MLD to fetch data buffer from the SMD level MAC buffer in order to resume DL data buffer transmission towards the client device.

[0031] In yet another embodiment, the at least one processor is configured to regulate copying of DL buffered data using SMD level MAC buffer via a standard validity timer (Tv).

[0032] In still another embodiment, the client device includes a cause indicator in the roaming request. The cause indicator indicates the at least one roaming-related KPI responsible for fast degradation of the KPIs.

[0033] In yet another embodiment, when the predefined roaming procedure is initiated for the rapid KPI drop, the at least one processor is further configured to transmit a roaming request directly from the client device to the target AP MLD. The roaming request includes serving AP MLD information and a serving AP MLD identifier indicating association of the client device with the serving AP MLD.

[0034] In still another embodiment, the at least one processor is further configured to transmit, by the target AP MLD, a STA Context Request to the serving AP MLD including the client device's previous association ID and transmit, by the serving AP MLD, a STA Context Response to the target AP MLD including data context of the client device.

[0035] In yet another embodiment, the at least one processor is further configured to transmit, by the target AP MLD, a roaming response to the client device, receive, by the target AP MLD, remaining buffered data from the serving AP MLD and resume, by the target AP MLD, data transmission towards the client devices.

[0036] In still another embodiment, the at least one processor is further configured to transmit a target access point identifier as part of the roaming request to indicate the target AP MLD to which the client device seeks to roam.

[0037] In yet another embodiment, the at least one processor is further configured to transmit an association identifier of the client device along with transmission of serving AP MLD identifier to enable the target AP MLD to request context information about the associated client device to the serving AP MLD.

[0038] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. For a better understanding of exemplary embodiments of the present invention, together with other and further features and advantages thereof, reference is made to the following description, taken in conjunction with the accompanying drawings.

[0039] According to various embodiments of the disclosure, roaming signaling, buffer protection, and context transfer procedures can be synchronized efficiently.

[0040] The embodiments of the disclosure itself, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings in which:

[0041] Figure 1 is an exemplary flow chart illustrating roaming procedures in conventional systems.

[0042] Figure 2 is an exemplary flow chart illustrating seamless roaming procedures as per an existing prior art.

[0043] Figure 3 is an exemplary illustration of an architecture of SMD roaming with different MAC-SAP as per an existing prior art.

[0044] Figure 4 is an exemplary illustration of an architecture of SMD roaming with a single MAC-SAP as per an existing prior art.

[0045] Figure 5 is an exemplary flow chart illustrating a method in accordance with a first embodiment of the present disclosure.

[0046] Figure 6 is an exemplary flow chart illustrating a method in accordance with a second embodiment of the present disclosure.

[0047] Figure 7 is an exemplary flow chart illustrating a method in accordance with a third embodiment of the present disclosure.

[0048] Figure 8 is an exemplary flow chart illustrating a method in accordance with a fourth embodiment of the present disclosure.

[0049] Figure 9 is an exemplary flow chart illustrating a method in accordance with a fifth embodiment of the present disclosure.

[0050] Figure 10 is an exemplary flow chart illustrating a method for managing buffered downlink (DL) data during seamless roaming in a wireless communication network, in accordance with embodiments of the present disclosure.

[0051] Figure 11 depicts an environment diagram of the devices (viz. a client device (STA) and a WLAN network apparatus) for managing buffered downlink data during seamless roaming in a wireless communication network, and an exemplary system managing of buffered downlink (DL) data during seamless roaming in a wireless communication network.

[0052] Figure. 12 is a block diagram of a station (STA) or a non-AP STA 1200 according to an embodiment of the disclosure.

[0053] Figure. 13 is a block diagram of an access point (AP) 1300 according to an embodiment of the disclosure.

[0054] Figure. 14 is a block diagram of a network entity 1400 according to an embodiment of the disclosure.

[0055] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

[0056] It should be appreciated by those skilled in art that any block diagrams herein represent conceptual views of illustrative devices embodying the principles of the present subject matter. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudo code, and the like represent various processes which may be substantially represented in computer readable medium and executed by a computer or processor, whether or not such computer or processor is explicitly shown.

[0057] Hereinafter, embodiments of the disclosure will be described in detail with reference to the accompanying drawings.

[0058] In describing the embodiments, while numerous details are set forth for the purpose of illustration, it is understood that some aspects of the disclosure may be practiced with less than all of these details. Numerous variations and alternatives to the details provided herein are possible and are considered within the scope of the disclosure. In some instances, descriptions related to technical contents well-known in the art may be omitted so as to not obscure an understanding of the disclosure, and such omitted descriptions are understood to be within the scope of the disclosure.

[0059] For the same reason, in the accompanying drawings, some elements may be exaggerated, omitted, or schematically illustrated. Further, the size of each element does not completely reflect the actual size. In the drawings, identical or corresponding elements are provided with identical reference numerals or different reference numerals.

[0060] The advantages and features of the disclosure and ways to achieve them will be apparent by making reference to embodiments as described herein in detail in conjunction with the accompanying drawings. However, the disclosure is not limited to the embodiments set forth herein, but may be implemented in various different forms. Other features, aspects, and advantages of the subject matter described herein will become apparent from the disclosure. The following embodiments are merely examples to aid in an understanding of the disclosure and should not be construed to narrow the scope or spirit of the subject matter described herein in any way, but on the contrary, the disclosure covers all modifications, equivalents and alternatives falling within the spirit and scope of the subject matter as defined by the appended claims and equivalents thereof. Throughout the specification, the same or like reference numerals designate the same or like elements. Furthermore, terms which will be described herein are terms defined in consideration of the functions in the disclosure, and may be different according to users, intentions of the operators, or customs. Therefore, the definitions of the terms should be made based on the contents throughout the specification.

[0061] Herein, it will be understood that each block of flowchart illustrations, and combinations of blocks in the flowchart illustrations, may be performed based on computer program instructions. These computer program instructions may be loaded collectively onto at least one processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which perform through any one of, or in any combination of, the at least one processor of the computer or other programmable data processing apparatus, create means for performing the functions specified in the flowchart block(s). These computer program instructions may also be stored in a non-transitory computer usable or computer-readable memory that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer usable or computer-readable memory produce an article of manufacture including instruction means that perform the function specified in the flowchart block(s). The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable data processing apparatus to produce a computer executed process such that the instructions that perform on the computer or other programmable data processing apparatus provide steps for executing the functions specified in the flowchart block(s).

[0062] Further, each block may represent a module, segment, or portion of code, which includes one or more executable instructions for executing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order. For example, two blocks(or functions) shown in succession may in fact be performed substantially concurrently or the blocks may sometimes be performed in the reverse order, depending upon the functionality involved.

[0063] As used in embodiments of the disclosure, a "~unit / module" may refer to a software element or a hardware element, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), which performs a predetermined function. However, the term including the word "~unit / module" does not always have a meaning limited to software or hardware. The "~unit / module" may be constructed either to be stored in an addressable storage medium or to execute one or more processors. Therefore, the "~unit / module" includes, for example, software elements, object-oriented software elements, components such as class elements and task elements, processes, functions, properties, procedures, sub-routines, segments of a program code, drivers, firmware, micro-codes, circuits, data, database, data structures, tables, arrays, and parameters. The components and functions provided by the "~unit / module" may be either combined into a smaller number of components and a "~unit / module," or divided into additional components and a "~unit / module." Moreover, the components and "~units / modules" may be implemented to reproduce one or more central processing units (CPUs) within a device or a security multimedia card. Further, in the embodiments, the "～unit / module" may include one or more processors.

[0064] The entirety of the one or more computer programs may be stored in a single memory device or the one or more computer programs may be divided with different portions stored in different multiple memory devices.

[0065] Any of the functions or operations described herein can be processed by one processor or a combination of processors. The one processor or the combination of processors is circuitry performing processing and includes circuitry like an application processor (AP, e.g. a CPU), a communication processor (CP, e.g., a modem), a graphics processing unit (GPU), a neural processing unit (NPU) (e.g., an artificial intelligence (AI) chip), a Wi-Fi chip, a Bluetooth® chip, a global positioning system (GPS) chip, a near field communication (NFC) chip, connectivity chips, a sensor controller, a touch controller, a finger-print sensor controller, a display driver integrated circuit (IC), an audio CODEC chip, a universal serial bus (USB) controller, a camera controller, an image processing IC, microprocessors, microcontrollers, digital signal processors, FPGA, ASIC, a microprocessor unit (MPU), a system on chip (SoC), an IC, or the like. The one processor or the combination of processors executes instructions that can be stored in a memory, such as the operating system, in order to control the overall operation of the device. Also, the one processor or the combination of processors is also capable of executing other processes and programs resident in the memory, such as processes for the disclosure.

[0066] It will be appreciated that various embodiments of the disclosure according to the claims and description in the specification can be realized in the form of hardware, software or a combination of hardware and software.

[0067] Any such software may be stored in non-transitory computer readable storage media. The non-transitory computer readable storage media store one or more computer programs (software modules), the one or more computer programs include computer-executable instructions that, when executed by one or more processors of an electronic device individually or collectively, cause the electronic device to perform a method of the disclosure. Additionally, or alternatively, such software may be a computer program [product] comprising instructions which, when executed by one or more processors of an electronic device individually or collectively, cause the electronic device to perform a method of the disclosure.

[0068] Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like read only memory (ROM), whether erasable or rewritable or not, or in the form of memory such as, for example, random access memory (RAM), memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a compact disk (CD), digital versatile disc (DVD), magnetic disk or magnetic tape or the like. It will be appreciated that the storage devices and storage media are various embodiments of non-transitory machine-readable storage that are suitable for storing a computer program or computer programs comprising instructions that, when executed, implement various embodiments of the disclosure. Accordingly, various embodiments of the present disclosure may provide a program comprising code for implementing apparatus or a method as claimed in any one of the claims of this specification and a non-transitory machine-readable storage storing such a program.

[0069] Hereinafter, the determination of priority between A and B in the present disclosure may refer to various actions such as selecting the one having a higher priority based on a predefined priority rule and performing an operation corresponding thereto, or omitting or dropping an operation corresponding to the one having a lower priority.

[0070] Hereinafter, "A or B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0071] In addition, "at least one of A, B, and C" as described in the present disclosure may be understood to include A, or B, or C, or any combination of A, B, and C.

[0072] In addition, "at least one of A, B, or C" as described in the present disclosure may be understood to include A, or B, or C, or any combination of A, B, and C.

[0073] Furthermore, "A / B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0074] Furthermore, "A, B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0075] Furthermore, "A and B" as described in the present disclosure may be understood as "A and / or B," which may include A, or B, or both A and B.

[0076] Furthermore, "if condition A and condition B are satisfied," as described in the present disclosure, may not be limited to a case where both condition A and condition B are satisfied, but may be understood to include a case where either condition A or condition B is individually satisfied, both condition A and condition B are satisfied, or one or more additional conditions are satisfied in combination.

[0077] Furthermore, throughout this disclosure, ordinal terms such as "first," "second," "third," etc., (and similar qualifiers) are used merely to distinguish between different instances, occurrences, configurations, messages, stages, elements or aspects of elements, operations, or information as described herein. Unless the context clearly dictates otherwise, the use of such ordinal terms does not itself require that the elements, operations, or information distinguished by these terms be structurally different, numerically distinct, or substantively dissimilar. For example, a "first signal" and a "second signal" may refer to instances of the same signal transmitted at different times or containing the same core information despite minor variations, or they may refer to signals with different content or characteristics, depending on the specific context. Similarly, a "first value" and a "second value" may represent the same magnitude but measured or applied in different circumstances, or they may represent different magnitudes. The interpretation should be guided by the specific technical context, function, and relationship described in the relevant portion of the specification and claims.

[0078] Furthermore, the terms "first ~", "second ~", etc., as described in the present disclosure with respect to various elements (e.g., information, objects, operation, sequences, or the like), should not limit those elements. These terms may only be intended to distinguish one element from another, and may not be intended to indicate a specific order. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element.

[0079] Furthermore, even if "first ~" and "second ~" are described in the present disclosure, it may be understood that element(s) referred to by "first ~" and "second ~" may be the same or different. For example, in case of element(s) being information, first information and second information may both be same information and, in some cases, are separate and different information.

[0080] In addition, the terms "if ~" and "in case that ~" as used in the disclosure or claims may be interpreted to include the meanings of "when (or upon) ~," "in response to ~," "based on ~," or "according to ~," and may be used interchangeably with these expressions. In addition, expressions other than those exemplified herein may also be used, as long as they have substantially the same meaning and do not impair the technical features of the present disclosure. If a method step (e.g. transmit a signal) is performed according to the disclosure of the application in connection with one of the above terms (such as "in case that ~" or the like), it may be interpreted to include the meanings (disclosure) of a prior determination that a feature has a specific state "~" (e.g. a bit length is above X), and then perform the method step in response to said determination.

[0081] In addition, the term "not perform" as used in the present disclosure or claims may, in context, be understood to mean that the corresponding step is omitted or skipped. Such a term may be replaced with other terms having the same or substantially equivalent meaning.

[0082] In addition, "transmitting a message including A and B" as described in the present disclosure, may be understood as encompassing both (i) transmitting A and B in a single message, and (ii) transmitting A and B separately via multiple messages (e.g., transmitting a first message including A and a second message including B). This interpretation may also apply to messages that include two or more items (e.g., A, B, C), transmitted either together or separately.

[0083] In addition, "transmitting a message including A and transmitting a message including B" may also be interpreted as transmitting a message including A and B in a single message.

[0084] In the embodiments of the present disclosure described herein, terms or components included in the disclosure may be expressed in singular or plural form depending on the specific embodiments presented. However, such singular or plural expressions are selected appropriately for convenience of description, and the present disclosure is not limited to a singular or plural number of components. A component expressed in the plural form may be implemented as a single component, and a component expressed in the singular form may be implemented as multiple components.

[0085] The drawings or flowcharts described herein illustrate example methods that may be implemented according to the principles of the present disclosure, and various modifications may be made to the methods illustrated in the flowcharts of the present disclosure. For example, although illustrated as a series of steps, various steps in each drawing or flowchart may overlap, occur in parallel, occur in a different order, or be repeated. In other examples, any step may be omitted or replaced with another step.

[0086] The process of the flowchart may be performed by a device. One or more of the steps of the flowchart can be implemented by one or more processors / computer programs executing instructions to perform the noted functions.

[0087] The methods and apparatuses proposed in the embodiments of the present disclosure may be disclosed in connection with drawings disclosing flowcharts to illustrate example methods that may be implemented according to the principles of the present disclosure. Such flowcharts may contain different branches and / or sub-branches. It is understood that the principles of the present disclosure do not only contain the combination of all branches / sub-branches disclosed in the embodiment, but the present disclosure also contains at least one isolated branch / isolated sub-branch, in particular to a single branch / single sub-branch.

[0088] The methods and apparatuses proposed in the embodiments of the present disclosure are not limited to each embodiment individually, but may also be applied in combination of all or some of the embodiments proposed in the disclosure. Therefore, the embodiments of the present disclosure may be modified and applied without significantly departing from the scope of the present disclosure, as would be understood by those skilled in the art.

[0089] In this case, even if certain wordings are described differently across embodiments, they may be used interchangeably or in substitution or in combination if their underlying concepts are equivalent. For example, for the same or equivalent concept, even if one embodiment uses the expression "A" and another embodiment uses the expression "B", such expressions may be understood interchangeably, in substitution, or in combination.

[0090] Furthermore, hereinafter, 5G mobile communication technologies (e.g., 5G new radio (NR)), 6th generation (6G) mobile communication technologies may be described by way of example, but the embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, newly evolved mobile communication systems developed after 5G and 6G may be included. Furthermore, based on determinations by those skilled in the art, the embodiments of the present disclosure may also be applied to other communication systems (e.g., Wi-Fi systems) through some modifications without significantly departing from the scope of the present disclosure

[0091] The terminology used in the following description to identify devices, to identify access nodes, to refer to network entities, to refer to messages, to refer to interfaces between network entities, and to refer to various identification information is provided for the sake of convenience in explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms denoting objects with equivalent technical meaning may be used. Furthermore, these terms may be replaced with terms defined in 802.11-related standard documents or other standard documents, where appropriate.

[0092] Hereinafter, expressions in this disclosure or the claims indicating that information may be configured from another device may, depending on the context, mean that a particular device receives such information from another device via physical layer signaling or higher layer signaling, and such expressions may be replaced with other terms having the same or substantially similar meaning.

[0093] The examples of the present disclosure can be applied to various wireless communication systems. For example, the examples of the present disclosure can be applied to WLAN systems. For example, the examples of the present disclosure can be applied to WLAN systems based on IEEE 802.11a / g / n / ac / ax / be standard documents. Furthermore, the examples of the present disclosure may also be applied to wireless LAN systems based on the newly discussed IEEE 802.11bn (or UHR (ultra high reliability)) standard documents. Additionally, the examples of the present disclosure may also be applied to wireless LAN systems based on next-generation standard documents following IEEE 802.11bn.

[0094] Hereinafter, the operational principle of the present disclosure will be described in detail with reference to the accompanying drawings.

[0095] To define standard set of procedure to achieve seamless data roaming is an important requirement of Wi-Fi8 Ultra High Reliability standards. In standards, seamless roaming is defined as the concept of a "non-access point multi link device (non-AP MLD) or station (STA)(i.e. client device) moving from a serving AP MLD to a target AP MLD such that the client device remains in an authenticated and associated state after the roaming procedure is completed, as shown in Figure 1.

[0096] One of the most crucial aspects of seamless roaming is to preserve and transfer an ongoing data session context to ensure a seamless handoff of data path from serving to target AP MLD while minimizing the data loss to achieve a near lossless handover. Also, the interruption time while roaming from serving AP to target AP should be minimized to zero (ideally) and < 10ms practically. According to recent developments and agreements in the standards , the basic building blocks for seamless roaming procedure have been agreed and awaiting the next level details. As shown in Figure 2, apart from discussions on enhancement to existing baseline roaming procedure such as Fast Transition (FT), another important candidate solution which is agreed between industry players is the concept of roaming between AP MLDs belonging to a Seamless Mobility Domain (SMD) which incorporates the following criteria to support a lossless seamless roaming of the client device:-

[0097] a. Seamless roaming of a client can take place between AP MLDs belonging to (i.e. affiliated to) same SMD domain.

[0098] b. For lossless data handover between serving and target AP MLDs, some form of data session context needs to be shared.

[0099] c. At the time of roaming initiation, for lossless data handover between serving and target AP MLDs, some mechanism needs to be defined to handle the Downlink (DL) buffered data at serving AP MLD (which is intended to be delivered to the client).

[0100] d. One of the possible mechanisms to handle DL buffered data is to define a system to forward this buffered data from serving AP MLD to target AP MLD and then to be delivered to the intended roaming client.

[0101] e. Also, in order to perform roaming procedure related signaling quickly (before the serving AP MLD is lost), there are discussions ongoing to have some form of roaming preparation in place so that some static configurations can be handled in advance before the actual roaming is triggered.

[0102] In the currently ongoing discussions about architecture and variants of Seamless Mobility Domain (SMD), a common understanding among the chipset manufacturers is as shown in Figures 3 and 4. Two different variants of SMD roaming architecture have been proposed:-

[0103] a. SMD roaming with different Medium Access Control-Service Access Point (MAC SAP), exposed to the Distributed System (DS, AP backend), for each non-collocated AP MLD of the SMD for roaming between those AP MLDs (shown in Figure 3).

[0104] b. SMD roaming with a single MAC-SAP, exposed to the DS, for the SMD and roaming within non-collocated AP MLDs of an SMD (shown in Figure 4).

[0105] Therefore, the problems with existing architecture are:

[0106] a. Utility of buffered DL data-

[0107] i. Timely handling of buffered DL data is essential to achieve near lossless handover.

[0108] ii. In non-real-time use cases (e.g. file downloads, buffered audio / video), the buffered data is often usable by the application.

[0109] ii. Especially when the dropping data packets significantly impact the TCP congestion window.

[0110] iv. Also in video transmissions, if the buffered data contains a video I-frame, it may be needed to render subsequent P-frames.

[0111] b. Roaming trigger (rate of roaming-trigger KPI e.g. RSSI, SINR drop at serving AP MLD)

[0112] i. According to the rate of drop of roaming KPI on the serving AP MLD, the entire roaming procedure can be categorized under three scenarios.

[0113] ii. Normal RSSI drop: When the rate of drop provides enough time to complete roaming signaling as well as retrieve some buffered DL data from serving AP MLD before moving to target AP MLD completely.

[0114] iii. Fast RSSI drop: When the rate of drop provides just enough time to complete roaming signaling but no time for buffered DL data retrieval from serving AP MLD.

[0115] iv. Panic RSSI drop: When the rate of drop is so drastic that there not even enough time to complete roaming related signaling procedure and serving AP MLD is lost beforehand.

[0116] Hence, there is need to define mechanism to handle the buffered DL data for all such cases for best case data recovery during seamless roaming.

[0117] When seamless roaming preparation does not support / implement buffered data handling as part of pre-roaming operations due to any backhaul limitations or implementation complexity, then there should be robust solutions to handle buffered data at the "time of roaming" itself to make it possible to achieve lossless and seamless roaming KPIs and UHR experience.

[0118] According to current IEEE spec draft reference, as part of Seamless roaming, the current AP MLD may forward DL data to the target AP MLD but the procedure of when and how to initiate the DL data forwarding is still open to be defined in standards.

[0119] The present disclosure proposes a method and a system to handle the buffered DL data (at serving AP MLD) during seamless roaming to efficiently prevent data loss for all possible 'rate of roaming-trigger KPI drop' scenarios while utilizing open scopes of data forwarding (to target AP MLD). Various embodiments of the present invention are summarized below:

[0120] a. To handle buffered DL data during seamless roaming using an embodiment described in Figure 5 for normal RSSI drop.

[0121] b. To handle buffered DL data during seamless roaming using an embodiment described in Figure 6 for normal RSSI drop.

[0122] c. To handle buffered DL data during seamless roaming using SMD level MAC buffer copying for fast RSSI drop.

[0123] d. Buffered data copying to SMD level buffer with a validity timer.

[0124] To handle buffered DL data during seamless roaming via direct roaming request to target AP2 for panic RSSI drop and related message format.

[0125] Figure 5is an exemplary flow chart illustrating a solution to the problem described above according to a first embodiment of the present disclosure, where a target AP resumes buffered data transmission post serving AP copying (buffered data to target AP's buffer) procedure is completed. Initially, STA (client) is connected to serving AP1(MLD). Both AP1 and AP2(MLD) (which is identified at roaming trigger time by STA are affiliated to same SMD.

[0126] a. At step 501, STA is in active data session with AP1;

[0127] b. At step 502, roaming trigger is hit at STA;

[0128] c. At step 503, STA sends a Roaming Request to AP1 including target AP2 indication;

[0129] d. At step 504, AP1 and AP2 engage in data session context transfer and Distributed System(DS / backend of AP MLDs) mapping change;

[0130] e. At step 505, AP1 sends a Roaming Response to STA containing required AP2's information such as link configuration;

[0131] f. At step 506, AP1 transmits the downlink data buffer copy to AP2 belonging to same SMD while continuing the DL buffered data transmission towards STA;

[0132] g. At step 507, as soon as the data buffer copying to AP2 is done / completed; at step 508, AP1 stops further DL data transmission towards STA and sends a short notification for context update about last acknowledged (Aced) sequence number (SN) (of buffered data being transmitted to STA) to AP2, and at step 509, simultaneously deletes the link with STA;

[0133] h. At step 510, AP2 fetches the copied data buffer and resumes the data transmission towards STA from the last ACKed_SN+1 onwards.

[0134] Figure 6 is an exemplary flow chart illustrating a solution to the problem described above according to a second embodiment of the present disclosure, where the target AP starts buffered data transmission as soon as serving AP copying (buffered data to target AP's buffer) procedure is started. Initially, STA(client) is connected to serving AP1(MLD). Both AP1 and AP2(MLD) (which is identified at roaming trigger time by STA) are affiliated to same SMD.

[0135] a. At step 601, STA is in active data session with AP1;

[0136] b. At step 602, roaming trigger is hit at STA;

[0137] c. At step 603, STA sends a Roaming Request to AP1 including target AP2 indication;

[0138] d. At step 604, AP1 and AP2 engage in data session context transfer and Distributed System (DS / backend of AP MLDs) mapping change;

[0139] e. At step 605, AP1 sends a Roaming Response to STA containing required AP2's information such as link configuration;

[0140] f. At step 606, AP1 starts with the data buffer copy to AP2 belonging to same SMD;

[0141] g. At step 607, as soon as AP1 starts data buffer copy procedure, it indicates AP2 to fetch and start transmitting the data towards STA in parallel to ongoing data copying procedure so that STA-AP2 data connection is initiated quickly;

[0142] h. At step 608, as soon as step 7 is performed, AP1 also deletes link with STA;

[0143] i. At step 609, AP2 is fetching and transmitting complete buffered data simultaneously to the STA.

[0144] In comparison to the first embodiment of the present disclosure described in figure 5, in the second embodiment, the STA-AP2 connection is resumed faster and may be typically helpful if chances of losing the serving AP is higher before STA-AP2 data connection can be resumed. But it comes with a trade-off that buffer data handling load is transferred completely to AP2 while AP1 is still copying the data to AP2's buffer.

[0145] Figure 7 is an exemplary flow chart illustrating a solution to the problem described above according to a third embodiment of the present disclosure relating to buffer data handling for fast RSSI drop. Initially, STA(client) is connected to serving AP1(MLD). Both AP1 and AP2(MLD) (which is identified at roaming trigger time by STA are affiliated to same SMD.

[0146] a. At step 701, STA is in active data session with AP1;

[0147] b. At step 702, roaming trigger is hit at STA;

[0148] c. At step 703, STA sends a Roaming Request to AP1 including target AP2 indication as well as an additional field: "cause" corresponding to "value": fast_RSSI_drop;

[0149] Now, at this time, since context exchange and DS mapping change between AP1 and AP2 is still not completed, AP1 cannot copy buffered data to AP2. But, since RSSI may be dropping faster, so there is a need for a mechanism to handle the buffered data faster. Hence, in the present embodiment, while context and DS mapping change are handled as-usual, AP1 starts to copy the buffered data to proposed SMD level buffer (which is common and accessible to affiliated APs) in parallel, thus by the time context exchange and DS mapping are completed, data buffer may already be available to AP2 for fetching / transmission, thus helping to preserve the data and make the process faster. Further steps of the present embodiment related to SMD level data copying are provided below:

[0150] d. At step 704, AP1 already starts copying the buffered data to SMD level buffer for preservation.

[0151] e. At step 705, which is ongoing in parallel to step4, AP1 and AP2 engage in data session context transfer and Distributed System (DS / backend of AP MLDs) mapping change.

[0152] f. At step 706, AP1 sends a combined "Roaming Response plus Delete Link" to STA and simultaneously indicates AP2 to resume complete DL data buffer transmission towards STA.

[0153] g. At step 707, AP2 fetches the data buffer (from SMD level data buffer) and resumes the complete data transmission towards STA.

[0154] In this embodiment, between Roaming Request and Roaming Response steps, AP1 may continue to transmit DL buffered data towards STA in which case at the final indication to Resume complete DL data buffer handling to AP2, AP1 shall also inform the last ACKed SN so that AP2 can fetch and resume data transmission towards STA from SN = last ACKed SN+1.

[0155] Figure 8 is an exemplary illustration of a solution to the problem described above according to a fourth embodiment of the present disclosure relating to buffered data copying to SMD level buffer. In this embodiment, an SMD with MAC SAP, shall host a common data buffer accessible to all affiliated AP MLDs. Upon need, an AP1 may copy its buffered data into SMD buffer and later upon appropriate signaling, the intended AP2 may fetch the data from SMD buffer to its own buffer for further handling. To efficiently utilize the SMD buffer, there should be a standard validity timer (Tv) associated to data copied to SMD buffer so that when left unutilized, SMD can clear out the buffer after such timer expiry. In an embodiment, the value of above validity timer shall be set according to, at least:

[0156] a. the data type(Access Category),

[0157] b. standard Roaming Signaling Completion timing and

[0158] c. other SMD / backend limitations.

[0159] Figure 9 is an exemplary flow chart illustrating a solution to the problem described above according to a fifth embodiment of the present disclosure relating to Buffer data handling for panic RSSI drop affiliated to same SMD.

[0160] a. At step 901, STA is in active data session with AP1.

[0161] b. At step 902, Roaming trigger maybe hit or not, but AP1 connection is lost due to rapid degradation in AP1's RSSI / SINR KPI.

[0162] c. At step 903, STA sends a Roaming Request directly to target AP2 using baseline Protected Management Frame (PMF) concept and tries to re-establish the connection to AP2. STA shall also include 'AP1 information and STA's association identifier with AP1' so that target AP2 can fetch essential context from previous serving AP1.

[0163] d. At step 904, the AP1 sends a STA Context Request to previous serving AP1 including STA's previous association ID.

[0164] e. At step 905, the AP1 sends a STA Context Response to target AP2 including the data context of the STA.

[0165] f. At step 906, the AP1 and AP2 engage to perform Distributed System (DS / backend of AP MLDs) mapping change.

[0166] g. At step 907, the AP2 sends a Roaming Response to the STA.

[0167] h. At step 908, the AP1 copies the remaining buffered data to target AP2 buffer.

[0168] i. At step 909, the AP2 fetches the data buffer and resumes the complete data transmission towards the STA.

[0169] In an embodiment, a message format pseudo code capturing the essential parameters that need to be defined and be present in Roaming Request message of the seamless roaming procedure. In an embodiment, the roaming request includes target AP ID i.e. the AP identifier for the target AP to which STA prefers to roam to after roaming trigger is hit. Further, the cause indicate is used to include cause value in all cases for fast KPI drop. The cause indicator may be fast_RSSI_drop or fast_SINR_drop. A skilled person may appreciate that the KPI may be Received signal strength indicator (RSSI) or the Signal to noise ratio (SINR). Thus, information about the factor which is key contributor is provided in the cause indicator during fast KPI drop. The serving AP ID is the element that is included for rapid drop cases (when Roaming Request is directly sent to target AP from STA) in order to inform target AP about the 'previous serving AP' to help target AP fetch the lost context about STA from the previous serving AP. The serving AP association identifier i.e., AID is included if 'serving AP ID' to indicate that target AP can request for context information about this associated STA to the previous serving AP.

[0170] Abbreviations:

[0171] DL : Downlink

[0172] AP : Access Point (e.g., Wi-Fi router)

[0173] DS : Distributed System (e.g., backend to AP)

[0174] non-AP : client station / device

[0175] STA : client station / device

[0176] SMD : Seamless Mobility Domain

[0177] KPI : Key Performance Indicator

[0178] MAC : Medium Access Control

[0179] SAP : Service Access Point

[0180] SN : Sequence Number

[0181] RSSI : Received Signal Strength Indicator

[0182] SINR : Signal to Interference and Noise Ratio

[0183] Modern Wi-Fi systems - particularly Wi-Fi 8 Ultra High Reliability (UHR)―increasingly require mechanisms to support seamless roaming, wherein a non-AP multi-link device (MLD) or station (STA) transitions between access point MLDs while remaining authenticated and associated without service interruption. As standardized in ongoing IEEE and industry discussions, a fundamental requirement for such roaming is the preservation and transfer of active data session context so that downlink (DL) data delivery remains near-lossless during handover. Because seamless roaming often involves rapid fluctuations in RF conditions such as RSSI and SINR, ensuring continuity of DL buffered data requires well-defined procedures for context sharing and buffer handling between the serving and target AP MLDs.

[0184] In conventional Wi-Fi roaming approaches, mechanisms such as Fast Transition (FT) provide baseline signaling for authentication and association across APs. However, these approaches do not adequately address scenarios requiring timely retrieval or forwarding of downlink buffered data from the serving AP MLD―data that may be essential for application continuity, especially for TCP-based transfers, video streams containing key I-frames, or other latency-sensitive traffic. Existing procedures also do not define how buffered data should be processed across different roaming trigger rates, including normal, fast, and panic RSSI- or SINR-drop situations, each of which imposes significantly different timing constraints.

[0185] As current discussions within the Seamless Mobility Domain (SMD) architecture indicate, roaming between AP MLDs affiliated within the same SMD may involve complex factors such as whether the affiliated APs expose individual MAC-SAP interfaces or share a unified MAC-SAP towards the distributed system (DS). In either case, ambiguity persists regarding how the serving AP MLD should manage its DL buffered data in real time―whether by forwarding the buffer to the target AP MLD, copying it to an SMD-level shared buffer, or performing in-parallel preservation mechanisms that account for DS mapping delays. These uncertainties complicate roaming preparation, message handling, and buffer preservation, especially in fast degradation scenarios where the serving AP MLD may be lost before conventional data forwarding can complete.

[0186] These challenges highlight the need for improved data-forwarding mechanisms that clearly define how buffered DL data should be preserved and transferred during seamless roaming for all degradation scenarios including normal, fast, and rapid KPI drops.

[0187] Solutions must specify when the serving AP MLD should forward buffered data, when such data should be copied to a shared SMD-level buffer with a validity timer, and when the STA itself must directly initiate roaming to the target AP MLD using only residual context. Likewise, well-defined signaling, message formats, and bearer-selection-like rules are needed to ensure that the DS mapping, context transfer, and resumption of buffered data transmission at the target AP MLD occur reliably even under stringent timing constraints.

[0188] Figure 10 is a flow diagram of a method for managing buffered downlink (DL) data during seamless roaming in a wireless communication network, according to one of the embodiments enclosed.

[0189] At step 1001, the method includes detecting a roaming request initiated by a client device connected to a serving access point multi-link device (AP MLD) to initiate a transition to a target AP MLD within a seamless mobility domain (SMD).

[0190] At step 1003, the method includes initiating a predefined roaming procedure in response to the detected roaming request. The predefined roaming procedure is selected based on a rate of degradation detected in at least one roaming-related key performance indicators (KPI). In an embodiment, the rate of degradation of the at least one roaming-related key performance indicators (KPI) is normal KPI drop. In another embodiment, the rate of degradation of the at least one roaming-related key performance indicators (KPI) is fast KPI drop. In yet another embodiment, the rate of degradation of the at least one roaming-related key performance indicators (KPI) is rapid KPI drop. Further, the at least one roaming-related KPI comprises, but not limited to, Received Signal Strength Indicator (RSSI) and Signal to Interference and Noise Ratio (SINR). A person skilled in the art appreciate that there may be other KPI as well that need to be monitored based on the application requirement.

[0191] At step 1005, the method includes managing the buffered downlink data between the serving AP MLD and the target AP MLD for the initiated roaming procedure. For example, when the predefined roaming procedure is initiated for the normal KPI drop, the method comprises copying, by the serving AP MLD, buffered DL data to a buffer in the target AP MLD while continuing transmission to the client device. Thereafter, the serving AP MLD, deactivates the DL data transmission to the client device upon completion of copying. Then, the serving AP MLD, transmits a notification for context update about last acknowledged (ACKed) sequence number (SN) of buffered data being transmitted towards client device, to the target AP MLD. In another exemplary scenario, when the predefined roaming procedure is initiated for the normal KPI drop, the serving AP MLD copies the buffered DL data to a buffer in the target AP MLD and indicates target AP MLD to initiate transmission of data towards client device in parallel to copying of buffered DL data in the target AP MLD. Thereafter, the serving AP MLD deletes or deactivate the communication link with the client device and resumes transmission of data towards client device from the target AP MLD.

[0192] In another embodiment, when the predefined roaming procedure is initiated for the fast KPI drop, the serving AP MLD copies the DL buffered data by the serving AP MLD using SMD level MAC buffer however, while copying the DL buffered data, the service AP MLD and the target AP MLD are engaged in data session context transfer and Distributed System mapping change. The copying of DL buffered data using SMD level MAC buffer is regulated via a standard validity timer (Tv). Further, the serving AP MLD, transmits a message to the client device, the message may include roaming response and a message for deletion of communication link between the client device and the service AP MLD. Thereafter, the serving AP MLD simultaneously transmits message to the target AP MLD to fetch data buffer from the SMD level MAC buffer in order to resume DL data buffer transmission towards the client device. The client device includes a cause indicator as well in fast KPI drop, the cause indicator indicates the at least one roaming-related KPI responsible for fast degradation of the KPIs. In an exemplary embodiment, the cause indicator may indicate FAST drop of received signal strength i.e., RSSI. In another embodiment, the cause indicator indicates FAST drop of signal to noise ratio i.e., SINR.

[0193] In yet another embodiment, when the predefined roaming procedure is initiated for the rapid KPI drop. In the rapid KPI drop scenario, the method transmits a roaming request directly from the client device i.e. STA to the target AP MLD i.e., AP2. The roaming request includes serving AP MLD information and a serving AP MLD identifier (AID) indicating association of the client device with the serving AP MLD. In rapid KPI drop, the target AP MLD transmits a STA Context Request to the serving AP MLD and the request includes client device's previous association ID as well. Further, the serving AP MLD transmits a STA Context Response to the target AP MLD including data context of the client device. The target AP MLD also transmits a roaming response to the client device and receives remaining buffered data from the serving AP MLD. In this way, the target AP MLD resumes data transmission towards the client device. During these roaming requests, a target access point identifier is transmitted as part of the roaming request so as to indicate the target AP MLD to which the client device seeks to roam. Also, the association identifier of the client device is transmitted along with transmission of serving AP MLD identifier to enable the target AP MLD for requesting context information about the associated client device to the serving AP MLD.

[0194] The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and / or software component(s) and / or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Generally, where there are operations illustrated in figures, those operations may be performed by any suitable corresponding counterpart means-plus-function components.

[0195] The order in which the various operations of the methods are described is not intended to be construed as a limitation, and any number of the method blocks described can be combined in any order to implement the method. Additionally, individual blocks may be deleted from the methods without departing from the spirit and scope of the subject matter described herein. Furthermore, the methods can be implemented in any suitable hardware, software, firmware, or combination thereof.

[0196] Figure 11 depicts a block diagram of a system 1101 for managing buffered downlink (DL) data during seamless roaming in a wireless communication network, according to one of the embodiments enclosed.

[0197] The disclosed system may be implemented in a network entity. In an exemplary embodiment, a client device (STA) may be associated with a WLAN network entity through a WLAN communication network (not shown in figure). As an example, the STA may include, without limitation, any device used by a user to communicate and / or access content such as, but not limited to, mobile phones, smartphones, laptops, wearables, Internet of Things (IoTs), and the like with LTE / 5G / 6G capabilities. As an example, the communication network may be a wireless telecommunication network such as Wireless Local Area Network (WLAN), Long-Term Evolution (LTE) network, 5thGeneration (5G) network, 6thGeneration (6G) network and the like. In an embodiment, an apparatus may be configured to perform the aspects of the present disclosure (not shown in figure). The system may be a functional element within the network entity or access point which may be configured to perform the aspects of the present disclosure. The network entity may comprise various radio access nodes, the nature of which can vary depending on the communication standard or deployment architecture. For example, in some embodiments, the radio access node may be a WLAN Wi-Fi Access Point with Distributed System (DS) as backend or Evolved Node B (eNB), typically associated with a 4G or Long Term Evolution (LTE) system and the radio access node may be a gNodeB (gNB), typically associated with a 5G or New Radio (NR) system and the radio access node be may be a base station associated with 6G.

[0198] The term network entity or access point are used interchangeably throughout the description.

[0199] In some implementations, the system 1101 may include an I / O interface, a processor 1103 and a memory 1105. In an embodiment, the memory 1105 may be communicatively coupled to the processor 1103. The processor 1103 may be configured to perform one or more functions of the network entity / access point for managing buffered downlink data using one or more modules. In an embodiment, the memory 1105 may store the data. A skilled person may appreciate that there may be a single processor or multiple processors that may help the network entity in managing buffered downlink data during roaming in a wireless communication network.

[0200] The processor 1103 is configured to detect a roaming request, initiated by a client device connected to a serving access point multi-link device (AP MLD), to initiate a transition to a target AP MLD within a seamless mobility domain (SMD). Once the request is detected, the processor 1103 initiates a predefined roaming procedure. The predefined roaming procedure is selected based on a rate of degradation detected in at least one roaming-related key performance indicators (KPI) such as for normal KPI drop, fast KPI drop or rapid KPI drop. The at least one processor is also configured to manage the buffered downlink data between the serving AP MLD and the target AP MLD for the initiated roaming procedure.

[0201] In a scenario, when the predefined roaming procedure is initiated for the normal KPI drop, the at least one processor 1103 is configured to copy, by the serving AP MLD, buffered DL data to a buffer in the target AP MLD while continuing transmission to the client device and once the data is copied, it deactivates the data transmission to the client device and transmits a notification for context update about last acknowledged (ACKed) sequence number (SN) of buffered data being transmitted towards client device, to the target AP MLD. The target AP fetches the copied data buffer and resumes the data transmission towards the client device from the last ACKed_SN+1 onwards.

[0202] In another scenario, when the predefined roaming procedure is initiated for the fast KPI drop, the at least one processor 1103 is configured to copy the DL buffered data by the serving AP MLD using SMD level MAC buffer, while copying the DL buffered data, the service AP MLD and the target AP MLD are engaged in data session context transfer and Distributed System mapping change. The at least one processor of the serving AP MLD, transmits a message to the client device. The message includes roaming response and a message for deletion of communication link between the client device and the service AP MLD. The at least one processor of the serving AP MLD, simultaneously transmits message to the target AP MLD to fetch data buffer from the SMD level MAC buffer in order to resume DL data buffer transmission towards the client device. In the fast KPI drop, the copying of DL buffered data using SMD level MAC buffer is regulated via a standard validity timer (Tv). The standard validity timer (Tv) is used so that SMD can clear out the buffer after such timer expiry. In Fast KPI drop scenario, a cause indicator is also used to indicate the factor responsible for fast KIP drop i.e. RSSI or SINR.

[0203] In another scenario, when the predefined roaming procedure is initiated for the rapid KPI drop, the processor 1103 is further configured to transmit a roaming request directly from the client device to the target AP MLD. The roaming request includes serving AP MLD information and a serving AP MLD identifier indicating association of the client device with the serving AP MLD. The processor 1103 is further configured to transmit, by the target AP MLD, a STA Context Request to the serving AP MLD including the client device's previous association ID and transmit, by the serving AP MLD, a STA Context Response to the target AP MLD including data context of the client device. The processor 1103 is further configured to transmit, by the target AP MLD, a roaming response to the client device and receive, by the target AP MLD, remaining buffered data from the serving AP MLD. In this way, the system resumes data transmission towards the client device. The processor 1103 is further configured to transmit an association identifier of the client device along with transmission of serving AP MLD identifier to enable the target AP MLD to request context information about the associated client device to the serving AP MLD.

[0204] FIG. 12 is a block diagram of a station (STA) or a non-AP STA 1200 according to an embodiment of the disclosure.

[0205] The STA 1200 is an electronic device capable of wireless communication and having various form factors, examples of the STA 1200 may include a UE, a mobile station (MS), a cellular phone, a smartphone, a computer, a tablet, a wearable device, an Internet of Things (IoT) device, or any other device / system capable of performing wireless communication with an AP (access point) 1300 and / or another STA through a wireless channel.

[0206] Referring to FIG. 12, the STA 1200 may include at least one transceiver (hereinafter, referred to as simply "transceiver") 1201, at least one processor (hereinafter, referred to as simply "processor") 1202, and at least one memory (hereinafter, referred to as simply "memory") 1203. According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the transceiver 1201, the processor 1202, and the memory 1203 of the STA 1200 may operate. However, components of the STA 1200 are not limited to the example components illustrated in FIG. 12. In another embodiment, the STA 1200 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in some embodiments, any combination of the transceiver 1201, the processor 1202, or the memory 1203 may be integrated in the form of one component.

[0207] The transceiver 1201 may be a communication circuit or communication circuitry that enables the STA 1200 to perform wireless communication with an AP or other STA(s). For example, the transceiver 1201 may enable the STA 1200 to transmit or receive a signal to or from a AP through wireless communication, or to transmit or receive a signal to or from other STA through wireless communication (or, peer-to-peer (P2P) communication). For example, the transceiver 1201 may support at least one of various cellular communication technologies including 3rd generation (3G), 4thgeneration (4G), long term evolution (LTE), 5th generation (5G) NR, 6thgeneration (6G), etc. Additionally, the transceiver 1201 may support at least one standard in the group of wireless communication protocol standards as defined in the protocol standards for Bluetooth, wireless local area network (WLAN) network (including institute of electrical and electronics engineers (IEEE) 802.11-2016 standard or its amendments, e.g., 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, 802.11be and 802.11bn, without being limited thereto). The various wireless communication technologies supported by the transceiver 1201 may include all subsequent generations of wireless communications.

[0208] According to an embodiment, STA 1200 may include a plurality of transceivers and may include a first transceiver and a second transceiver that support the same or different wireless communication technologies.

[0209] According to an embodiment, the transceiver 1201 may include various circuit structures used to transmit or receive signals to or from an AP or other STA(s) through a wireless channel. For example, the transceiver 1201 may include a radio frequency (RF) transmitter for up-converting and amplifying the frequency of a transmitted signal and an RF receiver for low-noise-amplifying a received signal and down-converting the frequency thereof. The transceiver 1201 may output a signal received through a wireless channel to the processor 1202 and may transmit, through a wireless channel, a signal output from the processor 1202.

[0210] The processor 1202 may control general operations of the STA 1200 according to embodiments of the disclosure. The processor 1202 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 1202 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 1203, individually, collectively or in any combination thereof. Further, the processor 1202 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme.

[0211] The processor 1202 may be electrically, operatively, and / or communicatively coupled to the transceiver 1201 to control the transceiver 1201.

[0212] The processor 1202 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. For example, the processor 1202 may include a communication processor (CP) configured to control communication operations and an application processor (AP) configured to control execution of an upper layer (for example, an application layer) . In a specific embodiment, at least a part of the processor 1202 may be included in one chip (or IC) and the other part of the processor 1202 may be included in another chip (or, IC). Otherwise, at least one processor may be included in another component, for example, the transceiver 1201 or the memory 1203.

[0213] The processor 1202 may perform or control or cause an operation of the STA 1200 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 1202 may control operations of the STA 1200 for processing a downlink signal received from an AP or generating and transmitting an uplink signal to an AP. To this end, the processor 1202 may execute a computer program, codes, or instructions stored in the memory 1203, so as to control other components of the STA 1200 to enable execution of various operations.

[0214] The memory 1203 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 1203 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0215] The memory 1203 may be electrically, operatively, and / or communicatively coupled to the processor 1202 and may be accessed by the processor 1202.

[0216] The memory 1203 may store a computer program, codes, or instructions executable by the processor 1202. According to an embodiment, a computer program, codes, or instructions executable by the processor 1202 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 1203, the processor 1202 may perform various functions according to an embodiment of the disclosure.

[0217] According to an embodiment of the disclosure, operations of the STA 1200 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 1203 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0218] FIG. 13 is a block diagram of an access point (AP) 1300 according to an embodiment of the disclosure.

[0219] The AP 1300 may perform wireless communication with at least one STA located within the area of the AP 1300 or another AP through a wireless channel. The AP 1300 may include a fixed AP or a mobile AP. The AP 1300 may perform communication with a node or an entity of a network through wired or wireless communication.

[0220] Referring to FIG. 13, the AP 1300 may include at least one transceiver (hereinafter, referred to as simply "transceiver") 1301, at least one processor (hereinafter, referred to as simply "processor") 1302, and at least one memory (hereinafter, referred to as simply "memory") 1303. According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the transceiver 1301, the processor 1302, and the memory 1303 of the AP 1300 may operate. However, components of the AP 1300 are not limited to the example components illustrated in FIG. 13. In another embodiment, the AP 1300 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in some embodiments, any combination of the transceiver 1301, the processor 1302, or the memory 1303 may be integrated in the form of one component.

[0221] The transceiver 1301 may be a communication circuit or communication circuitry that enables the AP 1300 to perform wireless communication with a non-AP STA, another AP, a node / entity of a network. For example, the transceiver 1301 may enable the AP 1300 to transmit or receive a signal to or from the STA 1200 through wireless communication, or to transmit or receive a signal to or from other AP through wireless communication. For example, the transceiver 1301 may support various cellular communication technologies including 3rd generation (3G), 4thgeneration (4G), long term evolution (LTE), 5th generation (5G) NR, 6thgeneration (6G), etc. Additionally, the transceiver 1301 may support at least one standard in the group of wireless communication protocol standards as defined in the protocol standards for Bluetooth, wireless local area network (WLAN) network (including institute of electrical and electronics engineers (IEEE) 802.11-2016 standard or its amendments, e.g., 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba, 802.11be and 802.11bn, without being limited thereto). The various wireless communication technologies supported by the transceiver 1201 may include all subsequent generations of wireless communications.

[0222] According to an embodiment, the transceiver 1301 may include various circuit structures used to transmit or receive signals to or from a STA or other AP through a wireless channel. For example, the transceiver 1301 may include a radio frequency (RF) transmitter for up-converting and amplifying the frequency of a transmitted signal and an RF receiver for low-noise-amplifying a received signal and down-converting the frequency thereof. The transceiver 1301 may output a signal received through a wireless channel to the processor 1302 and may transmit, through a wireless channel, a signal output from the processor 1302.

[0223] Meanwhile, according to an embodiment of the present disclosure, the AP 1300 may perform communication with a node or an entity of a network through wired or wireless communication. For example, the AP 1300 may perform wired or wireless communication with an adjacent AP, or a node or a network entity of a network through a backhaul network. Although not illustrated in FIG. 13, when the AP 1300 performs wired communication, the AP 1300 may further include a separate network interface for wired communication in addition to the transceiver 1301. The network interface may be referred to as network interface circuitry or communication interface circuitry.

[0224] The processor 1302 may control general operations of the AP 1300 according to embodiments of the disclosure. The processor 1302 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 1302 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 1303, individually, collectively or in any combination thereof. Further, the processor 1302 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme.

[0225] The processor 1302 may be electrically, operatively, and / or communicatively coupled to the transceiver 1301 to control the transceiver 1301.

[0226] The processor 1302 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. In a specific embodiment, at least a part of the processor 1302 may be included in one chip (or, IC) and the other part of the processor 1302 may be included in another chip (or, IC). Otherwise, at least one processor may be included in another component, for example, the transceiver 1301 or the memory 1303.

[0227] The processor 1302 may perform or control or cause an operation of the AP 1300 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 1302 may control operations of the AP 1300 for generating and transmitting a downlink signal to a STA or processing an uplink signal received from a STA. Otherwise, the AP 1300 may transmit or receive a signal to or from a neighboring AP, transfer a signal received from a STA to an upper node of the network, or transmit a signal transferred from an upper node of the network to a STA. To this end, the processor 1302 may execute a computer program, codes, or instructions stored in the memory 1303, so as to control other components of the AP 1300 to enable execution of various operations.

[0228] The memory 1303 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 1303 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0229] The memory 1303 may be electrically, operatively, and / or communicatively coupled to the processor 1302 and may be accessed by the processor 1302.

[0230] The memory 1303 may store a computer program, codes, or instructions executable by the processor 1302. According to an embodiment, a computer program, codes, or instructions executable by the processor 1302 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 1303, the processor 1302 may perform various functions according to an embodiment of the disclosure.

[0231] According to an embodiment of the disclosure, operations of the AP 1300 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 1303 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0232] The STA 1200 or the AP 1300 may perform various communication procedures related to the control plane or the user plane by cooperating with one or more network entities based on wireless communication. For example, the STA 1200 may communicate with any network entity in wireless local area network via the AP 1300, or the AP 1300 may perform at least one communication procedure by directly transmitting and receiving signals to / from, or relaying signals between, the network entities.

[0233] FIG. 14 is a block diagram of a network entity 1400 according to an embodiment of the disclosure.

[0234] The network entity 1400 may include an entity (apparatus, device, or server, etc.) that performs one or more network functions (NFs) or a part of a network function constituting a core network (e.g., a 5th generation (5G) core (5GC)) in a communication system. In this case, multiple NFs may be implemented within a single network entity, or a single NF may be distributed and implemented across a plurality of network entities. In addition, when an NF is implemented within the network entity, the NF may be implemented in the form of software, and in such a case, a program for operating the NF may be stored in memory of the network entity 1400.

[0235] A single NF may be implemented by one or more instances, which may be deployed on the same network entity or distributed across multiple network entities to operate. The instance may be a software unit that logically executes a specific network function, and may be implemented in a form that is decoupled from physical hardware resources. Further, one or more NFs may be implemented in the form of one network slice to operate to satisfy specifications required by a particular service.

[0236] The NF may include at least one of an access and mobility management function (AMF), a session management function (SMF), a local session management function (L-SMF), a user plane function (UPF), a local user plane function (L-UPF), a policy control function (PCF), a unified data management (UDM), a unified data repository (UDR), a network exposure function (NEF), a network repository function (NRF), an application function (AF), a network slice selection function (NSSF), a network data analytics function (NWDAF), a network slice admission control function (NSACF), an authentication server function (AUSF), or a data network (DN), etc.

[0237] Referring to FIG. 14, the network entity 1400 may include at least one network interface 1401, at least one processor 1402 (hereinafter, "processor"), and at least one memory 1403 (hereinafter, "memory"). As described above, a NF may be implemented in the form of a physical device such as the network entity 1400, or may be virtualized and executed in the form of an instance. When implemented as an instance, the NF need not necessarily include physical components as illustrated in FIG. 14. In such a case, the instance may be logically represented as comprising one or more logical functional elements.

[0238] According to at least one or a combination of methods corresponding to the embodiments described in the present disclosure, the network interface 1401, the processor 1402, and the memory 1403 of the network entity 1400 may operate. However, components of the network entity 1400 are not limited to the example components illustrated in FIG. 14. In another embodiment, the network entity 1400 may further include additional components in addition to the above-mentioned components, or some components may be omitted. Further, in an embodiment, the network interface 1401, the processor 1402, or the memory 1403 may be integrated in the form of one component.

[0239] The network interface 1401 is a collective term for a transmitter part of the network entity 1400 and a receiver part of the network entity 1400, and may be a communication circuit for transmitting or receiving a signal to or from a STA, an AP, or another network entity. Here, the communication circuit may include both a communication circuit for wireless communication and a communication circuit for a wired communication. For example, the network interface 1401 may include a circuit, logic, hardware, etc., configured to exchange a control plane message or a user plane message with a STA, an AP, or other core network entities through wireless communication or wired communication. The network interface 1401 may operate using various protocols (e.g., non-access stratum (NAS) protocol). The network interface 1401 may also be referred to, for convenience of description or depending on implementation, as communication circuitry, network interface circuitry, or a communication interface circuitry.

[0240] The processor 1402 may control general operations of the network entity 1400 according to embodiments of the disclosure. The processor 1402 may be implemented by one or more integrated circuit (or circuitry) (IC) chips and may execute various data processing operations. The processor 1402 may include at least one electric circuit, and may execute instructions (or a program, codes, data, etc.) stored in the memory 1403, individually, collectively or in any combination thereof. Further, the processor 1402 may include a single-core processor or multi-core processor, and may include a processor assembly including a plurality of processing circuits (circuitry) according to a specific implementation scheme. Further, it should be noted that, according to another embodiment, in a case where NF is implemented in the form of an instance, the network function may be not necessarily configured by physical hardware.

[0241] According to an embodiment, the processor 1402 may be electrically, operatively, and / or communicatively coupled to the network interface 1401 to control the network interface 1401.

[0242] The processor 1402 may include at least one processor (or processing circuitry), and the at least one processor may perform the following operations individually, collectively or in any combination thereof. In a specific embodiment, at least a part of the processor 1402 may be included in one chip (or IC) and the other part of the processor 1402 may be included in another chip (or IC). Otherwise, at least one processor may be included in another component, for example, the network interface 1401 or the memory 1403.

[0243] The processor 1402 may perform or control or cause an operation of the network entity 1400 for executing at least one or a combination of methods according to embodiments of the disclosure. For example, the processor 1402 may control operations of the network entity 1400 for exchanging a control plane message or a user plane message with a STA, a AP, or other core network entities through wireless or wired communication, using various protocols (e.g., NAS protocol). To this end, the processor 1402 may execute a computer program, codes, or instructions stored in the memory 1403, so as to control other components of the network entity 1400 to enable execution of various operations.

[0244] The memory 1403 corresponds to a hardware storage device capable of temporarily or permanently storing information and may include one or more storage media. For example, the memory 1403 may include a memory assembly including one or more storage media. For example, the one or more storage media may include permanent memory, such as a hard drive, flash memory, or read-only memory (ROM), semipermanent memory, such as random access memory (RAM), cache memory, or a combination thereof.

[0245] The memory 1403 may be electrically, operatively, and / or communicatively coupled to the processor 1402 and may be accessed by the processor 1402.

[0246] The memory 1403 may store a computer program, codes, or instructions executable by the processor 1402. According to an embodiment, a computer program, codes, or instructions executable by the processor 1402 may be either stored in a single memory device or separated and distributedly stored in two or more memory devices. By executing the instructions stored in the memory 1403, the processor 1402 may perform various functions according to an embodiment of the disclosure.

[0247] According to an embodiment of the disclosure, operations of the network entity 1400 may be caused to be performed based on execution of instructions (or a computer program or codes) stored in the memory 1403 by at least one processor (or processing circuitry) configured to execute the same individually, collectively, or in any combination thereof, based on processing circuitry that is not configured to execute instructions, and / or based on components of processing circuitry that is not configured to execute instructions.

[0248] It may be noted here that the subject matter of some or all embodiments described herewith reference to Figures 1-14 may be relevant for both the methods and the same is not repeated for the sake of brevity.

[0249] According to the various embodiments described above, he present disclosure described above has several technical advantages including, but not limited to, the realization of a method and a system for managing buffered downlink (DL) data during seamless roaming in a wireless communication network, which:

[0250] - enable near-lossless data handover across serving and target AP MLDs by introducing structured mechanisms for copying DL buffered data either directly between APs or to an SMD-level shared buffer, thereby ensuring continuity of ongoing sessions even under rapidly degrading RF conditions (normal, fast, or rapid RSSI / SINR-drop scenarios),

[0251] - provide coordinated context-transfer and DS-mapping procedures that allow AP MLDs within a Seamless Mobility Domain (SMD) to quickly exchange session information, significantly reducing roaming interruption time and ensuring reliable resumption of transmission from the exact last acknowledged sequence number,

[0252] - introduce fallback mechanisms for fast and panic / rapid drop conditions, where buffer preservation is performed proactively either to an SMD-level common buffer or via direct STA-to-target AP roaming requests thereby avoiding data loss when the serving AP becomes unreachable before standard signaling concludes,

[0253] - utilize standardized message structures with explicit fields such as target AP ID, cause indicators (e.g., fast_RSSI_drop), serving AP ID, and STA association identifiers, ensuring predictable roaming behavior, reducing ambiguity in inter-AP coordination, and improving interoperability across chipset implementations,

[0254] - support accelerated STA-to-target AP link establishment by enabling early initiation of target-side DL transmission (in certain embodiments) even while buffer copying operations are ongoing, thereby shrinking the roaming delay window and improving QoS for latency-sensitive applications.

[0255] The present system offers a range of technical advantages that significantly enhance the practicality, performance, and applicability of high-reliability Wi-Fi roaming architectures, particularly for multi-link deployments where uninterrupted data delivery is essential for modern multimedia, enterprise, industrial, and consumer applications.

[0256] Also, economically, the proposed methods reduce packet loss, retransmissions, and service interruptions―leading to measurable gains in spectrum efficiency, lower backhaul load, improved user experience, and reduced operational overhead for network providers. The predictability and reliability introduced by these procedures make the system suitable for large-scale deployments, enabling robust roaming performance in dense urban networks, enterprise campuses, public Wi-Fi infrastructures, and next-generation Wi-Fi UHR ecosystems.

[0257] Meanwhile, although specific embodiments of the present disclosure have been described in detail, various modifications may be made without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be defined by the claims and equivalents thereof.

[0258] Meanwhile, this specification and drawings disclose preferred embodiments of the present invention, and although specific terms are used, they are used in a general sense to facilitate explanation of the technical content of the present invention and to aid in understanding the disclosure, and are not intended to limit the scope of the present invention.

[0259] Furthermore, it is obvious to those skilled in the art to which the present disclosure pertains that other variations based on the technical concept of the present disclosure are possible in addition to the embodiments described herein. For example, some or all of the contents of one embodiment described above may be combined with some or all of the contents of one or more other embodiments, and such combinations are also included in the embodiments proposed in the present disclosure.

Claims

1.A method for managing buffered downlink (DL) data during seamless roaming in a wireless communication network, the method comprising:detecting a roaming request, initiated by a client device connected to a serving access point multi-link device (AP MLD), to initiate a transition to a target AP MLD within a seamless mobility domain (SMD);initiating a predefined roaming procedure in response to the detected roaming request, wherein the predefined roaming procedure is selected based on a rate of degradation detected in at least one roaming-related key performance indicators (KPI); andmanaging the buffered downlink data between the serving AP MLD and the target AP MLD for the initiated roaming procedure.2.The method of claim 1, wherein the rate of degradation of the at least one roaming-related key performance indicators (KPI) is selected from a group consisting of: normal KPI drop, fast KPI drop and rapid KPI drop, andwherein the at least one roaming-related KPI comprises at least one of: Received Signal Strength Indicator (RSSI) and Signal to Interference and Noise Ratio (SINR).3.The method of claim 1, wherein when the predefined roaming procedure is initiated for the normal KPI drop, the method further comprising:copying, by the serving AP MLD, buffered DL data to a buffer in the target AP MLD while continuing transmission to the client device;deactivating, by the serving AP MLD, DL data transmission to the client device upon completion of copying; andtransmitting, by the serving AP MLD, a notification for context update about last acknowledged (ACKed) sequence number (SN) of buffered data being transmitted towards client device, to the target AP MLD.4.The method of claim 1, wherein when the predefined roaming procedure is initiated for the normal KPI drop, the method further comprising:copying, by the serving AP MLD, buffered DL data to a buffer in the target AP MLD and indicating target AP MLD to initiate transmission of data towards client device in parallel to copying of buffered DL data in the target AP MLD; anddeleting, by the serving AP MLD, communication link with the client device and resuming transmission of data towards client device from the target AP MLD.5.The method of claim 1, wherein when the predefined roaming procedure is initiated for the fast KPI drop, the method further comprising:copying, by the serving AP MLD, the DL buffered data by the serving AP MLD using SMD level MAC buffer, wherein while copying the DL buffered data, the service AP MLD and the target AP MLD are engaged in data session context transfer and Distributed System mapping change;transmitting, by the serving AP MLD, a message to the client device, wherein the message includes roaming response and a message for deletion of communication link between the client device and the service AP MLD;simultaneously transmitting, by the serving AP MLD, message to the target AP MLD to fetch data buffer from the SMD level MAC buffer in order to resume DL data buffer transmission towards the client device;regulating copying of DL buffered data using SMD level MAC buffer via a standard validity timer (Tv), wherein the client device includes a cause indicator in the roaming request, wherein the cause indicator indicates the at least one roaming-related KPI responsible for fast degradation of the KPIs.6.The method of claim 1, wherein when the predefined roaming procedure is initiated for the rapid KPI drop, the method further comprising:transmitting a roaming request directly from the client device to the target AP MLD, wherein the roaming request includes serving AP MLD information and a serving AP MLD identifier indicating association of the client device with the serving AP MLD;transmitting, by the target AP MLD, a STA Context Request to the serving AP MLD including the client device's previous association ID;transmitting, by the serving AP MLD, a STA Context Response to the target AP MLD including data context of the client device;transmitting, by the target AP MLD, a roaming response to the client device;receiving, by the target AP MLD, remaining buffered data from the serving AP MLD; andresuming, by the target AP MLD, data transmission towards the client device.7.The method of claim 1, further comprising:transmitting a target access point identifier as part of the roaming request to indicate the target AP MLD to which the client device seeks to roam; andtransmitting an association identifier of the client device along with transmission of serving AP MLD identifier to enable the target AP MLD for requesting context information about the associated client device to the serving AP MLD.8.A system for managing buffered downlink (DL) data during seamless roaming in a wireless communication network, the system comprising:a memory;at least one processor coupled to the memory, wherein the at least one processor is configured to:detect a roaming request, initiated by a client device connected to a serving access point multi-link device (AP MLD), to initiate a transition to a target AP MLD within a seamless mobility domain (SMD);initiate a predefined roaming procedure in response to the detected roaming request, wherein the predefined roaming procedure is selected based on a rate of degradation detected in at least one roaming-related key performance indicators (KPI); andmanage the buffered downlink data between the serving AP MLD and the target AP MLD for the initiated roaming procedure.9.The system of claim 8, wherein the rate of degradation of the at least one roaming-related key performance indicators (KPI) is selected from a group consisting of: normal KPI drop, fast KPI drop and rapid KPI drop, andwherein the at least one roaming-related KPI comprises at least one of: Received Signal Strength Indicator (RSSI) and Signal to Interference and Noise Ratio (SINR).10.The system of claim 8, wherein when the predefined roaming procedure is initiated for the normal KPI drop, the at least one processor is further configured to:copy, by the serving AP MLD, buffered DL data to a buffer in the target AP MLD while continuing transmission to the client device;deactivate, by the serving AP MLD, DL data transmission to the client device upon completion of copying; andtransmit, by the serving AP MLD, a notification for context update about last acknowledged (ACKed) sequence number (SN) of buffered data being transmitted towards client device, to the target AP MLD.11.The system of claim 8, wherein when the predefined roaming procedure is initiated for the normal KPI drop, the at least one processor is further configured to:copy, by the serving AP MLD, buffered DL data to a buffer in the target AP MLD and indicating target AP MLD to initiate transmission of data towards client device in parallel to copying of buffered DL data in the target AP MLD; anddelete, by the serving AP MLD, communication link with the client device and resuming transmission of data towards client device from the target AP MLD.12.The system of claim 8, wherein when the predefined roaming procedure is initiated for the fast KPI drop, the at least one processor is further configured to:copy, by the serving AP MLD, the DL buffered data by the serving AP MLD using SMD level MAC buffer, wherein while copying the DL buffered data, the service AP MLD and the target AP MLD are engaged in data session context transfer and Distributed System mapping change;transmit, by the serving AP MLD, a message to the client device, wherein the message includes roaming response and a message for deletion of communication Link between the client device and the service AP MLD;simultaneously transmit, by the serving AP MLD, message to the target AP MLD to fetch data buffer from the SMD level MAC buffer in order to resume DL data buffer transmission towards the client device; andregulate copying of DL buffered data using SMD level MAC buffer via a standard validity timer (Tv), wherein the client device includes a cause indicator in the roaming request, wherein the cause indicator indicates the at least one roaming-related KPI responsible for fast degradation of the KPIs.13.The system of claim 8, wherein when the predefined roaming procedure is initiated for the rapid KPI drop, the at least one processor is further configured to:transmit a roaming request directly from the client device to the target AP MLD, wherein the roaming request includes serving AP MLD information and a Serving AP MLD identifier indicating association of the client device with the serving AP MLD.14.The system of claim 8, wherein the at least one processor is further configured to:transmit, by the target AP MLD, a STA Context Request to the serving AP MLD including the client device's previous association ID; andtransmit, by the serving AP MLD, a STA Context Response to the target AP MLD including data context of the client device,wherein the at least one processor is further configured to:transmit, by the target AP MLD, a roaming response to the client device;receive, by the target AP MLD, remaining buffered data from the serving AP MLD; andresume, by the target AP MLD, data transmission towards the client devices.15.The system of claim 13, wherein the at least one processor is further configured to:transmit an association identifier of the client device along with transmission of serving AP MLD identifier to enable the target AP MLD to request context information about the associated client device to the serving AP MLD.

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