Adaptive SRS Beam Sweeping for Low-Latency mmWave TX Selection
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Solution Overview
Problem
Existing methods for UE TX beam selection in mmWave band communications suffer from high latency and inaccurate beam measurements due to asymmetric circuitry design and non-reciprocity of wireless propagation channels, particularly in scenarios like remote driving or remote sensing, where latency issues are exacerbated by the need for multiple SRS OFDM signals.
Innovation Solution
Adaptive transmission beam sweeping method that allows UE to transmit SRS sequences with multiple TX beams within a single OFDM signal duration, applying each beam to consecutive waveform repetitions, and a base station dynamically determines a split factor to optimize beam measurement accuracy and reduce latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple SRS OFDM signals are used for UE TX beam sweeping, then beam measurement accuracy is improved, but latency increases significantly
Solution Approach 1:
The patent segments the SRS OFDM signal in the frequency domain by dividing the available frequency resources into multiple comb indices. Each comb index corresponds to a different TX beam, allowing multiple beams to be transmitted simultaneously within a single OFDM signal duration. This frequency-domain segmentation enables parallel beam measurement without requiring multiple sequential SRS OFDM signals, thus reducing latency while maintaining measurement accuracy.
Solution Approach 2:
The patent transitions from time-domain beam sweeping (sequential transmission of multiple SRS OFDM signals) to frequency-domain beam multiplexing (simultaneous transmission of multiple beams within one OFDM signal). By utilizing different frequency combs for different beams, the system achieves multi-beam measurement in parallel within a single OFDM symbol, effectively adding a frequency dimension to the beam sweeping process and eliminating the sequential time delay.
2Productivity
If UE TX beam sweeping is performed sequentially in time domain, then beam selection is completed, but training overhead increases
Solution Approach 1:
The patent merges multiple beam transmission operations into a single OFDM signal by multiplexing different TX beams across different frequency combs. Instead of transmitting SRS signals for multiple beams sequentially in time, the system combines multiple beam transmissions in the frequency domain, allowing the base station to measure and evaluate all candidate beams simultaneously from a single OFDM signal. This merging operation reduces training overhead and improves beam selection efficiency.
3Ease of operation
If copy RX beam setting to TX beam setting is used, then beam selection is simplified, but measurement accuracy deteriorates due to asymmetric circuitry
Solution Approach 1:
The patent performs preliminary beam measurement for all candidate TX beams in advance by transmitting SRS signals with different beams simultaneously in the frequency domain. The base station measures the received power for each beam and identifies the best beam before actual data transmission begins. This preliminary action allows the system to pre-determine the optimal beam configuration, avoiding the need to copy RX beam settings and ensuring accurate beam selection that accounts for the asymmetric TX RF frontend circuitry.
Data Source
AI summary
To achieve adaptive transmission beam sweeping, a user equipment sweeps one or more transmit, TX, beams to transmit a Sounding Reference Signal, SRS, sequence within one SRS orthogonal frequency-division multiplexing, OFDM, signal duration, wherein each TX beam is applied on a group of time consecutive waveform repetitions within the SRS OFDM signal duration.