Variable-Length TIM Structure for Large-Scale WLAN Station Support
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Solution Overview
Problem
Existing wireless local area network (WLAN) technologies, particularly in the 802.11ah standard, face challenges in efficiently indicating traffic information to a large number of stations, especially when there is no unicast buffer data for any station, limiting the number of supported users and requiring frequent beacon intervals for compressed TIM segments.
Innovation Solution
Incorporating an indication field in radio frames sent by the access point (AP) to indicate whether the frame carries traffic indication virtual bitmap information, allowing stations to determine if they have unicast buffer data to be sent, even when the AP has no buffer data for any station, using broadcast or multicast modes and setting this field in various fields within the TIM or compressed TIM information elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the TIM information element uses a fixed-length length field (1 octet) and 7-bit bitmap offset, then the structure is simple and easy to parse, but the maximum number of supported stations is limited to 2007 AIDs
Solution Approach 1:
The patent applies dynamics by making the length field and bitmap offset field variable-length rather than fixed. The length field can be 1 or 3 octets, and the bitmap offset field can be 7 or 15 bits, allowing the TIM structure to adapt its size based on the number of stations needing service, thus supporting up to 65535 AIDs while maintaining parsing efficiency
Solution Approach 2:
The patent changes the parameters of the TIM structure by allowing the length field to take different values (1 or 3 octets) and the bitmap offset field to have different bit lengths (7 or 15 bits). This parameter variability enables the system to support a larger number of stations (up to 65535 AIDs) while keeping the structure manageable through defined parsing rules
2Quantity of substance
If compressed TIM segments are used to support a large number of users, then more stations can be supported, but the beacon interval must be increased frequently which increases time consumption and reduces network efficiency
Solution Approach 1:
The patent uses segmentation by dividing the bitmap into multiple segments when the number of stations exceeds the single-segment capacity. Each segment can be indicated through the variable-length structure, allowing efficient representation of large numbers of stations without requiring frequent beacon intervals, thus reducing time loss while supporting more users
3Reliability
If the AP sends paging information to stations in power saving mode, then stations can be notified of buffer data, but stations cannot determine whether they have unicast buffer data when the AP has no buffer data for any station
Solution Approach 1:
The patent extracts the indication of unicast buffer data status from the general paging information by using specific bit positions in the variable-length structure. When the length field indicates 3 octets and the bitmap offset field is set to a specific value, it explicitly indicates that the AP has no unicast buffer data for any station, allowing stations to determine their data transmission needs without unnecessary data exchange
Data Source
AI summary
Provided are a method and a device for sending traffic indication information. In the method, an AP sends a radio frame to multiple STAs associated with the AP, wherein the radio frame carries an indication field, and the indication field is used to indicate whether the radio frame carries traffic indication virtual bitmap information. According to the technical solution provided, in the case where the AP has no unicast cache data for any station, multiple STAs associated with the AP can know whether the AP has their respective unicast cache data to be sent.