Ref: 38.821
Options for HARQ Optimization
HARQ Process Count and Feedback:
- Option 1: Keep 16 HARQ processes, disable UL HARQ feedback, and rely on RLC ARQ.
- Option 2: Increase HARQ processes beyond 16, enable UL HARQ feedback, and maintain a 4-bit HARQ process ID field.
Solutions for Managing >16 HARQ Process IDs:
- Slot-number-based approach.
- Virtual process ID with retransmission timing restrictions.
- Reuse HARQ process ID within RTT time window.
- Reinterpret existing DCI fields with higher-layer assistance.
HARQ Enhancements for Soft Buffer Management
- Pre-emptive HARQ to reduce stop-and-wait time.
- Configurable HARQ buffer usage per UE and HARQ process.
- HARQ buffer status reports from the UE.
Recommendations and Next Steps
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Use adaptive approaches to configure HARQ processes and feedback mechanisms based on system conditions (e.g., RTT, channel type, UE density).
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Further investigate trade-offs among HARQ process count, RLC ARQ dependency, and buffer management.
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Incorporate traffic patterns, mobility, and scheduling in system-level simulations.
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Ensure backward compatibility for UEs with limited HARQ process support.
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Engage in specification development to refine HARQ feedback, buffer size, and process count configurations.
“Though Many Ue & gNB stack vendor started supporting “disable UL HARQ feedback” still many works need to do to manage the Latency and improve Overall Throughput.”
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