Directional Beacon Transmission for WLAN Sector Discovery
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Solution Overview
Problem
Current IEEE standards do not adequately define beacon transmission methodologies for sectorized wireless access points with directional antennas, leading to inefficient neighbor discovery and inter-sector handoff processes, resulting in unnecessary re-transmissions and power drain in wireless local area networks.
Innovation Solution
Implementing a method where access points transmit beacons on different sectors at predictable times and announce sector transmission details to clients, allowing clients to discover and synchronize with reachable sectors using virtual Target Beacon Transmission Times (TBTT) and Sector Information Elements (IEs), facilitating efficient sector discovery and inter-sector handoff.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sectorized APs with directional antennas are used to improve spatial reuse and capacity, then network capacity and coverage are improved, but beacon transmission methodology becomes undefined and neighbor discovery efficiency deteriorates
Solution Approach 1:
The patent segments the beacon transmission process by introducing sector-specific TBTT offsets for different directional antennas. Each sector transmits beacons at distinct time intervals relative to its TBTT, allowing clients to identify and discover sectors through these segmented transmission patterns without requiring complex centralized coordination.
Solution Approach 2:
The patent applies preliminary action by having the AP announce sector configuration information (number of sectors, channel assignments, TBTT offsets) before actual sector discovery and handoff operations. This pre-announcement enables clients to proactively schedule their beacon listening and neighbor discovery activities, improving efficiency without increasing runtime complexity.
2Reliability
If clients listen for beacons from all sectors to enable neighbor discovery and handoff, then handoff efficiency is improved, but power consumption and signaling overhead increase
Solution Approach 1:
The AP announces sector configuration information including TBTT offsets and channel assignments before clients perform neighbor discovery. Clients use this pre-provided information to calculate and schedule their beacon listening times for each sector, avoiding continuous monitoring and reducing power consumption while maintaining reliable handoff capability.
Solution Approach 2:
Clients autonomously calculate the TBTT and listening schedule for each sector based on the announced configuration information and their current position. This self-service approach eliminates the need for continuous AP signaling during operation, reducing both power consumption and signaling overhead while maintaining handoff reliability.
3Reliability
If multiple virtual TBTTs are assigned to different sectors to enable predictable beacon timing, then inter-sector handoff efficiency is improved, but device complexity and signaling overhead increase
Solution Approach 1:
The patent segments the TBTT management by assigning distinct virtual TBTT offsets to different sectors. Each sector's beacon transmission time is calculated as TBTT plus its specific offset, creating a segmented time schedule that simplifies client calculations compared to managing completely independent timing for each sector.
Solution Approach 2:
The patent uses a universal reference TBTT that serves as the base timing for all sectors. Each sector's virtual TBTT is derived from this single reference point through additive offsets, allowing the system to manage multiple sectors with a unified timing framework rather than requiring completely independent timing mechanisms for each sector.
Data Source
AI summary
A method for transmitting beacon transmissions in a wireless local area network (WLAN) communications system (100) operating on one or more channels includes transmitting a first beacon (C1) using a directional antenna in a first direction (D1) on a first channel. A second beacon (C2) is then transmitted using a directional antenna in a second direction (D2) on the first channel. This process is then repeated such that the first beacon and second beacon after a predetermined beacon interval. The first beacon begins its transmission at a target beacon transmission time (TBTT) and the second beacon begins its transmission in a sequential period defined by an antenna switching time after the transmission of the first beacon.