MU-MIMO Link Adaptation via Selective MCS Feedback
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Solution Overview
Problem
In wireless local area networks (WLANs) supporting multi-user multiple input multiple output (MU-MIMO) transmission, channel interference between transmitters and receivers hampers data transmission and reception, necessitating an optimized link adaptation method to improve processing rates by recommending modulation and coding schemes (MCS) effectively.
Innovation Solution
A method where an access point transmits a physical layer convergence procedure (PLCP) protocol data unit (PPDU) containing a modulation and coding scheme (MCS) request to stations, receives feedback, and adjusts MCS values based on recommended values from stations, ensuring efficient data transmission by minimizing interference and reducing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple stations transmit MCS feedback simultaneously in MU-MIMO transmission, then comprehensive channel information can be obtained, but feedback conflicts occur and overhead increases
Solution Approach 1:
The access point transmits an MCS request frame to stations before they transmit MCS feedback, preliminarily establishing the feedback transmission order. This preliminary action prevents simultaneous feedback transmission by informing stations of their designated transmission timing in advance, thereby avoiding feedback conflicts while maintaining comprehensive channel information collection
Solution Approach 2:
The patent implements periodic MCS feedback transmission where stations transmit feedback at regularly间隔ed time points determined by the access point. The access point controls the feedback process by sending request frames at periodic intervals and stations respond at predetermined intervals, transforming simultaneous transmission into structured periodic transmission that eliminates conflicts
2Productivity
If MCS feedback is transmitted frequently to maintain accurate link adaptation, then processing rate improves, but overhead increases
Solution Approach 1:
Stations autonomously compute and determine their own MCS feedback values based on received signals and channel conditions, then transmit only the computed feedback information to the access point. This self-service mechanism eliminates the need for the access point to process complex channel calculations, reducing overhead while maintaining accurate link adaptation through frequent feedback
Solution Approach 2:
The patent implements selective MCS feedback where not all stations transmit feedback in every round, but only those designated by the access point based on current channel conditions and transmission needs. This partial action approach maintains sufficient channel information accuracy for link adaptation while significantly reducing overall feedback overhead compared to all-stations-always-transmit
Data Source
AI summary
A method of link adaptation performed by an access point supporting multi user (MU) multiple input multiple output (MIMO) in wireless local area network system is provided. The method includes transmitting, to a first station, a physical layer convergence procedure (PLCP) protocol data unit (PPDU) containing a modulation and coding scheme (MCS) request (MRQ) and receiving, from the first station, a MCS feedback (MFB) in response to the MRQ, wherein the first station is one of destination stations of MU-MIMO transmission performed by the access point, and the MFB includes a recommended MCS value computed, by the first station, on the assumption that the first station, as a member of the destination stations, receives data transmitted over at least one spatial stream allocated to the first station in MU-MIMO transmission.