Directional Antenna Channel Access via Contention Period Segmentation
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Solution Overview
Problem
Wireless communication systems using directional antennas face issues such as deafness and hidden node problems, which degrade system performance and reduce spatial reuse gain, especially in high-speed communication systems like those using the 60 GHz frequency band.
Innovation Solution
A central control unit divides the contention period into beamformable and non-beamformable periods, generating a beacon message that includes information about these periods to manage channel access effectively, allowing beamforming during the beamformable period and non-beamforming during the non-beamformable period, thereby enhancing spatial reuse and reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a directional antenna is used to extend signal reach distance, then spatial reuse gain is improved, but deafness issue and hidden node issue increase causing system performance deterioration
Solution Approach 1:
The contention period is segmented into beamformable contention periods and non-beamformable contention periods. During beamformable periods, directional beamforming is applied to extend signal reach and improve spatial reuse. During non-beamformable periods, omnidirectional transmission is used to ensure reliable RTS frame reception and avoid deafness issues. This temporal segmentation allows the system to achieve both high productivity through directional transmission and high reliability through omnidirectional fallback.
2Reliability
If TDMA resource allocation is used to resolve CSMA/CA issues, then hidden node issue is resolved, but resource utilization efficiency decreases when traffic is generated intermittently
Solution Approach 1:
The system dynamically switches between TDMA and CSMA/CA resource allocation modes based on traffic conditions. When traffic is continuous and predictable, TDMA provides reliable hidden node resolution. When traffic is intermittent, the system transitions to CSMA/CA with directional beamforming to improve resource utilization efficiency. This dynamic adaptation allows the system to maintain high reliability when needed while achieving high productivity under varying traffic loads.
3Reliability
If RTS/CTS control frames are transmitted to resolve hidden node issue, then hidden node issue is improved, but channel access time increases due to repeated RTS retransmission in deafness state
Solution Approach 1:
The system employs periodic omnidirectional transmission intervals within the contention period to detect and resolve deafness conditions. During these periodic omnidirectional phases, RTS frames are transmitted in all directions to ensure reliable reception by all nodes. This periodic action prevents persistent deafness states and reduces the need for repeated RTS retransmissions, thereby resolving hidden node issues while minimizing channel access time delays.
Data Source
AI summary
Provided are a method of performing contention based channel access by classifying a contention period into a beamformable contention period in which a beamforming is allowed and a non-beamformable contention period in which the beamforming is interrupted so as to resolve an issue regarding channel access occurring due to an introduction of a directional antenna for handling a path loss in a wideband wireless communication system according to an embodiment of the present invention, and a method for maximizing a spatial reuse gain by managing, for each direction, information about a transmission time of a message received from a dispersion device.