Half-Duplex Device Synchronization Gaps for Frequency Drift
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Solution Overview
Problem
Half-duplex wireless communication devices operating in enhanced or extreme coverage scenarios lose frequency synchronization due to high repetition factors, leading to frequency drift and inter-carrier interference, which complicates network node's ability to estimate and compensate for the drifting carrier frequency, especially in low SNR conditions.
Innovation Solution
Implementing synchronization gaps during uplink transmissions allows the device to temporarily stop and retune to the downlink carrier, maintaining time and frequency synchronization with the network, thereby reducing inter-carrier and inter-symbol interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high repetition factors are used for uplink transmissions in half-duplex devices, then coverage enhancement is achieved, but frequency synchronization is lost leading to frequency drift and inter-carrier interference
Solution Approach 1:
The patent implements periodic synchronization gaps within the repeated uplink transmission sequence. These gaps occur at regular intervals (e.g., every 16, 32, or 64 repetitions) allowing the half-duplex device to temporarily stop transmitting and retune to the downlink carrier frequency. This periodic interruption maintains frequency synchronization without significantly impacting the overall coverage enhancement benefit, as the gaps are small relative to the total transmission duration.
2Productivity
If continuous uplink transmissions are performed without gaps, then transmission efficiency is improved, but the device cannot retune to downlink carrier causing frequency drift
Solution Approach 1:
The patent segments the continuous uplink transmission into groups of repeated transmissions separated by synchronization gaps. Each group contains a specific number of repetitions (e.g., 16, 32, 64) followed by a gap for synchronization. This segmentation maintains high transmission efficiency within each group while periodically restoring frequency synchronization, thus balancing productivity and measurement precision.
3Measurement precision
If the device retunes to downlink carrier during uplink transmissions, then frequency synchronization is maintained, but transmission time is increased
Solution Approach 1:
The patent applies partial action by implementing synchronization gaps at selective intervals rather than continuously. The gap frequency and duration are optimized based on the repetition factor and coverage requirements. For example, gaps may be inserted every 16 repetitions for high repetition factors, or every 32-64 repetitions for lower factors. This partial approach maintains frequency synchronization when critically needed while minimizing the total time loss compared to continuous gap insertion.
Data Source
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AI summary
Methods and apparatus disclosed herein enable a half-duplex, HD, wireless communication device, WCD (16), to remain synchronized to a supporting communication network (10), during uplink transmissions that use a large repetition factor, also referred to a using a large bundle size. For example, the WCD (16) uses a rule whereby the WCD (16) tunes back to the downlink carrier from time to time while making an uplink transmission that uses a large repetition factor. Re-tuning to the downlink carrier from time to time in this manner allows the WCD (16) to correct and maintain its time and frequency synchronization with respect to the network (10).