Multi-AP Joint Transmission Backhaul Bandwidth Reduction
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Solution Overview
Problem
Existing multi-AP communication systems face challenges in efficiently managing retransmissions, particularly in joint transmission scenarios, which can lead to increased backhaul bandwidth requirements and inefficiencies.
Innovation Solution
The system employs a mechanism that allows for the reuse of data units conveyed from a master AP to slave APs for initial transmissions, enabling subsequent joint retransmissions without retransmitting the data units over the backhaul, thus reducing bandwidth requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If joint transmission is used by multiple APs to increase coverage and spectral efficiency, then reception quality and spectral efficiency are improved, but backhaul bandwidth requirements increase during retransmissions
Solution Approach 1:
The patent applies preliminary action by having slave APs store the MAC output data units received from the master AP before the joint transmission occurs. This pre-storage enables the slave APs to participate in retransmissions without requiring real-time backhaul communication, thereby reducing backhaul bandwidth requirements while maintaining reliable reception through joint transmission.
2Reliability
If data units are retransmitted over the backhaul link for joint retransmission, then retransmission reliability is improved, but backhaul bandwidth consumption increases
Solution Approach 1:
The patent implements self-service by enabling slave APs to use their locally stored MAC output data units for retransmissions without requiring continuous backhaul support. The slave APs serve themselves by retrieving stored data units when retransmission is needed, eliminating the need for energy-intensive real-time backhaul communication while maintaining retransmission reliability.
3Quantity of substance
If MAC output data units are stored at slave APs for potential retransmission, then backhaul bandwidth requirements are reduced, but storage capacity requirements at slave APs increase
Solution Approach 1:
The patent applies partial action by having slave APs store only the MAC output data units that are relevant for joint transmission to specific STAs, rather than storing all possible data units. This selective storage approach reduces the storage capacity requirement at slave APs while still enabling them to participate in retransmissions when needed, thereby balancing storage requirements with backhaul bandwidth savings.
Data Source
AI summary
Multiple access points (APs) that transmit jointly at the same time to one or more stations (STAs) need logically to be connected via a link, e.g. a backhaul link. The master AP creates physical layer input data units (PSDUs) to be transmitted during joint transmission and conveys it via the link to one or more slave APs. It may happen that a STA receives the PSDU or parts of it erroneously, in which case a retransmission takes place. A mechanism that allows to reuse the PSDU, which was conveyed by the master AP via the link to the slave AP for the initial transmission, for any subsequent retransmission. Thereby, the bandwidth requirement of the backhaul link is significantly lowered when retransmissions take place. In particular, the difficulty that the PSDU contents change within a retransmission is addressed.