WLAN Channel Sounding with Phase-Aware Beamforming Smoothing
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Solution Overview
Problem
In wireless local area networks (WLANs), beamforming processes experience discontinuity between beamforming matrices for adjacent subcarriers, leading to signal energy loss and increased packet error rates due to the absence of channel smoothing operations.
Innovation Solution
A method involving the transmission of a null data packet (NDP) and feedback frame exchange between a first and second apparatus to estimate channels, perform singular value decomposition, and generate phase information for beam steering matrices, reducing discontinuity by reflecting this information in beamforming operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If beamforming is performed without channel smoothing operation, then the beamforming process is simple and fast, but discontinuity between beamforming matrices causes signal energy loss and increased packet error rates
Solution Approach 1:
The patent applies preliminary action by performing channel smoothing operation on the beamformed signal before the signal is transmitted. The access point receives a beamformed signal from the station, performs channel smoothing on this signal in advance, and then transmits the smoothed signal. This preliminary smoothing action prevents discontinuity issues during actual data transmission, resolving the contradiction between fast beamforming and reliable communication.
2Reliability
If channel smoothing operation is performed on beamformed signal, then signal energy is preserved and packet error rate is reduced, but the beamforming process becomes more complex and time-consuming
Solution Approach 1:
The patent applies self-service by having the station perform channel smoothing on the beamformed signal using its own received signal characteristics. The station estimates the channel based on the beamformed signal it receives, and uses this estimation to perform smoothing. This self-service approach distributes the computational complexity and leverages the station's own channel knowledge, reducing the overall system complexity while maintaining signal energy preservation.
3Stability of the object's composition
If separate channel smoothing operation is performed on beamformed signal, then discontinuity between adjacent subcarriers is addressed, but the beamforming process cannot be efficiently integrated with MU-MIMO operations
Solution Approach 1:
The patent applies merging by integrating the channel smoothing operation directly into the MU-MIMO beamforming process. Instead of performing smoothing as a separate post-processing step, the access point performs smoothing on the beamformed signal as part of the MU-MIMO transmission process. The access point receives beamformed signals from multiple stations, performs channel smoothing on each signal, and then transmits them simultaneously. This merging of smoothing with MU-MIMO operations maintains beamforming matrix continuity while preserving MU-MIMO integration capability.
Data Source
AI summary
A method of communication performed by a first apparatus with respect to a second apparatus in a wireless local area network (WLAN) system including the first apparatus and the second apparatus, includes: transmitting a null data packet (NDP) based on a first protocol standard to the second apparatus; receiving a first feedback frame including information on an estimated first channel and phase information from the second apparatus in response to the NDP; performing beamforming with respect to the second apparatus by reflecting the phase information in the information on the estimated first channel; and transmitting a beamformed physical layer protocol data unit (PPDU) to the second apparatus.