Beam-Specific Timing Precompensation for SFN Delay Spread
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Solution Overview
Problem
High-speed trains using single frequency networks experience inter-symbol interference due to varying arrival times of transmissions from multiple transmission and reception points, leading to increased delay spread and signal interference.
Innovation Solution
Implementing beam-specific timing precompensation by determining timing differences in uplink transmissions across multiple beam pair links and applying corresponding precompensations to downlink transmissions to align signal arrival times, thereby reducing delay spread and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple TRPs transmit on the same time-frequency resource in an SFN, then spatial diversity gain is provided, but inter-symbol interference occurs due to varying arrival times
Solution Approach 1:
The base station performs timing precompensation before downlink transmission by calculating timing differences between multiple TRPs based on uplink timing measurements. Each TRP applies a specific timing offset to its downlink transmission to pre-align the arrival times at the moving UE, thereby preventing inter-symbol interference while maintaining spatial diversity
2Manufacturing precision
If timing precompensation is applied to align signal arrival times, then delay spread is reduced, but transmission timing complexity increases
Solution Approach 1:
The system uses uplink timing feedback from the UE to the base station to determine timing differences between TRPs. The base station measures uplink arrival times at different TRPs, calculates the timing offset, and applies this feedback information to precompensate downlink transmissions, creating a closed-loop timing synchronization mechanism
Solution Approach 2:
The base station acts as an intermediary that receives uplink signals from the UE via multiple TRPs, processes timing information, and then coordinates the downlink transmissions from all TRPs with unified timing precompensation values, simplifying the overall timing coordination
3Reliability
If cyclic prefix duration is extended to accommodate delay spread, then signal reception is improved, but transmission overhead increases
Solution Approach 1:
Instead of extending the cyclic prefix as a reactive measure, the system proactively aligns transmission timings before the signals are sent out. By precompensating the timing offsets based on uplink measurements, the downlink signals from multiple TRPs arrive synchronized at the UE, eliminating the need for extended cyclic prefixes
Data Source
AI summary
Aspects relate to a user equipment that transmits an uplink transmission on a first receive beam of a first beam pair link and on a second receive beam of a second beam pair link. A base station receives the uplink transmission on a first transmit beam of the first beam pair link and a second transmit beam of the second beam pair link via first and second transmission and reception points associated with the base station. The base station transmits a downlink transmission on the first transmit beam with a first beam-specific timing precompensation and on the second transmit beam with a second beam-specific timing precompensation. The first beam-specific timing precompensation and the second beam-specific timing precompensation are based on a timing difference between the reception of the uplink transmission via the first TRP and via the second TRP. The user equipment receives the beam-specific timing precompensations.