Wireless Joint Transmission With Phase-Offset-Resilient Precoding
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Solution Overview
Problem
Joint transmission (JT) schemes in wireless communication networks, such as Wi-Fi, face challenges due to increased complexity and sensitivity to phase offsets caused by imperfect synchronization between access points (APs), leading to significant degradation and multi-user interference (MUI).
Innovation Solution
Access points are configured to determine precoding matrices and weighting matrices based on channel information, distributing calculations to reduce computational complexity and ensuring zero multi-user interference (MUI) even with moderate phase offsets, using beam alignment and QR decomposition to optimize signal-to-noise ratio (SNR).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If joint transmission is implemented to increase throughput, then throughput improvement is achieved, but transmission complexity increases
Solution Approach 1:
The precoding matrix is divided into separate precoding matrices for each access point, allowing independent calculation and transmission. This segmentation reduces the complexity of coordinating a single large precoding matrix across multiple APs while maintaining the throughput benefits of joint transmission.
Solution Approach 2:
A master access point is introduced as an intermediary to coordinate the joint transmission. The master AP collects channel information from all STAs and calculates the overall precoder, then distributes precoder components to participating APs. This intermediary approach simplifies the coordination complexity by centralizing the precoding calculation function.
2Reliability
If phase synchronization is improved to reduce phase offset, then transmission reliability is improved, but synchronization complexity increases
Solution Approach 1:
The system changes the parameter of phase offset tolerance by designing the precoding scheme to be robust against larger phase offsets. Instead of requiring precise phase synchronization, the method allows for larger phase differences (e.g., up to 45 degrees) while maintaining acceptable performance, thereby reducing synchronization complexity requirements.
3Quantity of substance
If synchronization packet length is increased to reduce overhead, then communication overhead is reduced, but phase error accumulates
Solution Approach 1:
The system uses a shorter synchronization packet than would be ideal for perfect synchronization, accepting that some phase offset will remain. This partial action approach reduces the packet length and associated overhead while the robust precoding design compensates for the residual phase error, achieving acceptable performance with less synchronization effort.
Data Source
AI summary
An access point (AP) is provided for a joint transmission with at least one further AP to a plurality of stations. The AP is configured to determine, based on channel information for the plurality of stations, a respective precoding matrix for a beamed transmission to each of the plurality of stations with substantially zero multi-user interference (MUI) at the respective station and a respective overall channel matrix based on the channel information and the precoding matrix of the respective station; obtain one or more further overall channel matrices of the at least one further AP for one or more first stations of the plurality of stations; and determine, based on the one or more overall channel matrices and the one or more further overall channel matrices, for the AP and the at least one further AP a respective weighting matrix for the transmission to the one or more first stations.