Centralized AP Precoding for Wireless LAN Uplink MU-MIMO
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Solution Overview
Problem
Existing wireless local area network (WLAN) systems lack efficient uplink multi-user multiple-input multiple-output (MU-MIMO) transmission methods, which are typically limited to downlink communication, leading to suboptimal spectral efficiency and increased latency, power consumption, and reduced capacity.
Innovation Solution
Implementing centralized precoder calculation at the access point (AP) for uplink MU-MIMO transmission, involving channel estimation, precoder coefficient computation, and communication of these coefficients to stations, utilizing sounding packets and implicit estimation techniques to manage clock and phase drifts among multiple stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If uplink MU-MIMO transmission is implemented without centralized precoder calculation, then device complexity at stations is reduced, but spectral efficiency and transmission capacity deteriorate
Solution Approach 1:
The access point acts as an intermediary that performs centralized precoder calculation based on channel state information from multiple stations. The AP receives sounding packets, computes optimal precoders, and distributes them to stations, thereby achieving high spectral efficiency without requiring complex processing at individual stations.
Solution Approach 2:
The system segments the precoder calculation function from the stations and relocates it to the access point. This separation allows stations to transmit simple sounding packets while the AP handles the computationally intensive precoder computation, resolving the contradiction between station complexity and overall system efficiency.
2Loss of time
If uplink MU-MIMO transmission is implemented without centralized coordination, then latency is reduced, but transmission reliability and interference management worsen
Solution Approach 1:
The system performs preliminary channel estimation and precoder calculation before actual data transmission. Stations send sounding packets in advance, the AP computes precoders based on these measurements, and distributes them before uplink MU-MIMO transmission begins, ensuring reliable interference management without adding significant latency.
3Device complexity
If traditional downlink-only MIMO is used, then device complexity is minimized, but capacity and spectral efficiency are limited
Solution Approach 1:
The access point is designed to perform multiple functions: traditional downlink MIMO, uplink channel estimation via sounding packets, centralized precoder calculation for uplink MU-MIMO, and coordination of multi-station transmissions. This multi-functionality enables the system to achieve high capacity without proportionally increasing overall system complexity.
Data Source
AI summary
An access point (AP) for wireless communication may include data processing hardware; and memory hardware in communication with the data processing hardware, the memory hardware storing instructions that when executed on the data processing hardware cause the data processing hardware to perform operations including: identifying, at the AP, one or more transmitting stations having one or more spatial streams; sending, from the AP to the one or more transmitting stations, a sounding request; performing, at the AP, multiple user multiple input multiple output (MU-MIMO) channel estimation based on the sounding request response; computing, at the AP, one or more precoder coefficients for the one or more transmitting stations based on the MU-MIMO channel estimation; and sending, from the AP to the one or more transmitting stations, the one or more precoder coefficients and a transmission trigger.