Multi-AP Joint Transmission Coordination for SINR Improvement
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Solution Overview
Problem
Existing wireless networks with standalone Basic Service Sets (BSSs) face challenges in controlling interference and improving Signal-to-Interference-Plus-Noise Ratio (SINR) for stations (STAs) located at the edge of networks and within overlapping BSS zones.
Innovation Solution
The implementation of multi-AP coordination, specifically Joint Transmission (JT) schemes, where multiple Access Points (APs) synchronize and transmit the same signal to a STA, reducing interference and enhancing SINR. This involves the distribution and synchronization of JT data among Slave APs and a Master AP, using JT Trigger frames and coordinated PHY and MAC layer processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple APs transmit simultaneously to a STA, then SINR is improved and interference is reduced, but system complexity and coordination overhead increase
Solution Approach 1:
The patent segments the joint transmission process into distinct phases: data distribution phase where MPDUs are distributed from Master AP to Slave APs, and joint transmission phase where synchronized transmission occurs. This segmentation reduces coordination complexity by separating data preparation from execution.
Solution Approach 2:
The patent implements preliminary action by distributing MPDUs to Slave APs in advance during the data distribution phase, before the actual joint transmission. Slave APs store these MPDUs in their buffers, ready for synchronized transmission, which simplifies real-time coordination during the transmission phase.
2Adaptability or versatility
If JT data is distributed to Slave APs, then joint transmission capability is enabled, but buffer memory requirements and data management complexity increase
Solution Approach 1:
The patent applies local quality by allowing each Slave AP to buffer only the specific MPDUs assigned to it for joint transmission, rather than requiring all APs to store all possible data. This localized buffering reduces overall memory requirements while maintaining joint transmission capability.
Solution Approach 2:
The patent implements discarding and recovering by allowing Slave APs to discard buffered MPDUs after successful joint transmission, and to recover/request additional MPDUs from the Master AP if needed for retransmission. This dynamic buffer management optimizes memory usage.
3Reliability
If retransmission is performed by redistributing JT data, then transmission reliability is improved, but transmission time and overhead increase
Solution Approach 1:
The patent uses preliminary action by pre-distributing MPDUs to Slave APs buffers during the data distribution phase. When retransmission is needed, Slave APs can immediately use their buffered copies without waiting for redistribution, significantly reducing retransmission time and overhead.
Solution Approach 2:
The patent implements beforehand cushioning by maintaining copies of MPDUs in Slave APs buffers as a cushion against potential transmission failures. This pre-prepared cushion enables rapid retransmission without requiring full data redistribution, improving reliability while minimizing time loss.
Data Source
AI summary
An access point (AP) includes a receiver, which, in operation, receives a Joint Transmission (JT) Trigger frame from another AP that indicates MAC protocol data units (MPDUs) to be jointly transmitted to a communication apparatus; and a local memory that stores one or more MPDUs previously transmitted to the communication apparatus.