Master-Access Point Joint Transmission Coordination
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Solution Overview
Problem
Next-generation wireless LAN systems face challenges in improving spectrum efficiency and area throughput, especially in dense environments with multiple access points and stations, and outdoor settings, where existing technologies struggle to manage interference and optimize performance.
Innovation Solution
A method for joint frame transmission in a wireless LAN system using a Master-Access Point (M-AP) that coordinates multiple Slave-Access Points (S-APs) through Coordinated-Request To Send (C-RTS) and Clear To Send (CTS) frames, enabling coordinated beamforming and OFDMA transmission to prevent interference and enhance throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple access points transmit frames simultaneously in dense environments, then area throughput increases, but interference from overlapping basic service sets and unintended stations increases
Solution Approach 1:
The M-AP sends a C-RTS frame before the actual joint transmission to reserve the channel and notify other stations. This preliminary action prevents other stations from transmitting during the upcoming joint transmission period, thereby avoiding interference while enabling the M-APs to transmit simultaneously and improve area throughput.
Solution Approach 2:
The C-RTS and CTS frames act as intermediaries in the coordination process between M-APs and other stations. These control frames carry timing and resource allocation information that mediates the transmission schedule, allowing joint transmission to occur without causing interference to other basic service sets.
2Productivity
If multiple access points perform joint transmission, then spectrum efficiency improves, but coordination complexity between access points increases
Solution Approach 1:
The coordination function is segmented between the M-AP (coordinator) and S-APs (participants). The M-AP is responsible for sending C-RTS frames and receiving CTS frames from S-APs, while S-APs only need to respond with CTS and perform transmission. This segmentation reduces individual device complexity while enabling joint transmission for improved spectrum efficiency.
Solution Approach 2:
Multiple S-APs are merged into a coordinated transmission group under the M-AP's control. They transmit identical data to the same STA simultaneously using the same resource units, effectively combining their transmission capabilities to improve spectrum efficiency while the M-AP manages the coordination to keep individual device complexity manageable.
3Reliability
If access points use traditional RTS/CTS handshake, then collision avoidance is achieved, but transmission overhead increases in multi-AP scenarios
Solution Approach 1:
The C-RTS frame serves multiple functions simultaneously: it acts as a trigger frame to initiate joint transmission, reserves the channel for multiple M-APs, and coordinates timing information for participating S-APs. This multi-functionality maintains collision avoidance reliability while reducing the number of separate control frames needed, thereby reducing transmission overhead compared to traditional multi-AP coordination approaches.
Data Source
AI summary
Proposed are a method and apparatus for performing joint transmission in a wireless LAN system. Specifically, an M-AP transmits a C-RTS frame to first and second S-APs. The M-AP receives, from the first and second S-APs, a CTS frame that is a response to the C-RTS frame. The M-AP performs joint transmission on an STA through the first and second S-APs.