Uplink MU-MIMO Precoding Using AP-Calculated Sounding Coefficients
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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) precoding techniques, leading to suboptimal spectral efficiency, capacity, power consumption, and latency in uplink transmissions.
Innovation Solution
Implementing centralized precoder calculation at the access point (AP) for uplink MU-MIMO, involving channel estimation, precoder coefficient computation, and transmission to stations, using sounding packets and implicit estimation methods to handle clock and phase drifts among multiple antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If uplink MU-MIMO precoding is implemented, then spectral efficiency and capacity are improved, but system complexity increases due to centralized precoder calculation at the AP
Solution Approach 1:
The patent introduces sounding packets as an intermediary mechanism to facilitate channel estimation between the AP and multiple STAs. These sounding packets carry channel state information that enables the AP to calculate precoders without requiring direct complex interactions between all STAs, thus improving spectral efficiency while managing system complexity through structured channel probing
Solution Approach 2:
The patent replaces complex real-time channel measurement and feedback mechanisms with implicit channel estimation using sounding packets. This substitution simplifies the system by using pre-configured sounding sequences rather than requiring continuous complex channel state information exchange, thereby improving productivity while controlling device complexity
2Productivity
If centralized precoder calculation is performed at the AP, then uplink transmission capacity increases, but processing time and latency increase
Solution Approach 1:
The patent performs channel estimation using sounding packets in advance of actual data transmission. By obtaining channel state information through preliminary sounding exchanges, the AP can prepare precoder calculations beforehand, thus increasing uplink transmission capacity while minimizing processing time during actual data transfer
Solution Approach 2:
The patent implements dynamic precoder updates based on changing channel conditions. The system continuously performs sounding and recalculates precoders as needed, allowing the uplink transmission capacity to adapt to channel variations while maintaining optimal processing time by only updating when necessary rather than continuously
3Productivity
If multiple STAs transmit simultaneously in uplink MU-MIMO, then data rates increase, but interference management becomes more difficult
Solution Approach 1:
The patent applies precoding specifically to each STA's transmission based on its individual channel characteristics obtained from sounding. This local optimization of transmission quality for each user enables multiple STAs to transmit simultaneously at high data rates while the precoder suppresses interference between users, thus improving productivity while managing interference complexity through user-specific optimization
4Device complexity
If clock and phase drifts among multiple antennas are not compensated, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements self-service mechanisms where each STA transmits sounding packets that inherently contain information about its own clock and phase characteristics. The AP uses these self-provided references to estimate and compensate for drifts, maintaining measurement precision without requiring complex external synchronization systems, thus improving channel estimation accuracy while keeping device complexity manageable
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.