Post-equalization Precoding for Multi-User MIMO Capacity
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Solution Overview
Problem
Existing wireless local area networks (WLANs) face limitations in multi-user communication due to constraints on the number of receive antennas, which restrict the number of devices that can be included in multi-user multiple-input multiple-output (MIMO) groups, especially when devices like wireless HDTVs and computers with multiple antennas are involved.
Innovation Solution
A wireless access point (WAP) apparatus with a station grouping module, precode selector, and spatial mapper that supports orthogonal frequency division multiplexed (OFDM) communication channels, allowing for post-equalization precoding to include devices with an aggregate number of receive antennas exceeding the number of transmit antennas, thereby enhancing communication capabilities by precoding concurrent transmissions using a similarity transform matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional precoding methods are used in MU-MIMO, then the system can maintain simple processing, but the aggregate number of receive antennas must not exceed the number of transmit antennas, limiting network capacity
Solution Approach 1:
The precoding process is segmented into two distinct stages: first-stage precoding that operates on the original signal, and second-stage precoding that operates on the equalized signal. This segmentation allows the system to handle cases where the aggregate number of receive antennas exceeds the number of transmit antennas, thereby increasing network capacity without overwhelming computational complexity.
Solution Approach 2:
The first-stage precoding is applied preliminarily before equalization to pre-condition the signal and reduce interference. This preliminary action simplifies the subsequent equalization process and enables the second-stage precoding to effectively handle the antenna number mismatch, allowing more receive antennas than transmit antennas while maintaining manageable complexity.
2Adaptability or versatility
If the aggregate number of receive antennas exceeds the number of transmit antennas, then more devices can be included in MU-MIMO groups, but conventional precoding methods fail to provide adequate interference management
Solution Approach 1:
Equalization is introduced as an intermediary step between reception and second-stage precoding. This intermediary process compensates for channel effects and reduces interference before the second-stage precoding operates, enabling reliable interference management even when the aggregate number of receive antennas exceeds the number of transmit antennas. This allows greater device compatibility in MU-MIMO groups while maintaining signal reliability.
3Reliability
If single-user MIMO is used for each device, then interference management is simplified, but the airtime available for video streams is reduced
Solution Approach 1:
Multiple user streams are merged into a single MU-MIMO transmission group, allowing concurrent communication with multiple devices. The two-stage precoding method manages interference within this merged group, maintaining signal quality comparable to single-user MIMO while significantly increasing the airtime efficiency and reducing the total time required for video stream delivery across multiple devices.
Data Source
AI summary
A wireless access point including: a station grouping module for selecting station nodes for concurrent multi-user (MU) multiple-input multiple-output (MIMO) communication links, for retrieving ‘sounding’ packets therefrom which characterize the associated communication channels; a precode selector for determining whether an aggregate number of receive antennas on the at least two station nodes exceeds in number the plurality of antenna on the WAP; a post-equalization precoder responsive to an affirmative determination by the precode selector to perform a similarity transform of the inner products of the associated communication channels using ‘Q’ as a transform matrix where ‘Q’ block diagonalizes the associated communication channels; and a spatial mapper for precoding all concurrent transmissions to the selected at least two station nodes using “Q” as a precode matrix.