Fast NACK Mechanism for Wireless Packet Loss Recovery
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Solution Overview
Problem
Existing wireless communication systems face inefficiencies in transmitting negative acknowledgment (NACK) feedback messages during physical layer issues, leading to increased latency and buffering at the radio link control (RLC) layer.
Innovation Solution
A user equipment (UE) is enabled to transmit a NACK feedback message prior to a reassembly timer expiring, based on detecting lost packets at the RLC layer due to specific situations such as measurement gaps, connected discontinuous reception (C-DRX) wake up latencies, or interference from neighboring cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the UE waits for the reassembly timer to expire before transmitting NACK feedback, then the system maintains simple timing synchronization, but the latency increases and packet recovery is delayed
Solution Approach 1:
The UE transmits the NACK feedback message before the reassembly timer expires upon detecting a lost packet. This preliminary action allows the base station to initiate retransmission earlier, reducing the overall latency for packet recovery without requiring complex timer coordination mechanisms.
Solution Approach 2:
The system dynamically adapts the NACK transmission timing based on packet loss detection. Instead of a fixed timer-based approach, the UE can trigger NACK transmission at different times depending on whether packet loss is detected, optimizing the balance between latency reduction and system complexity.
2Productivity
If the UE transmits NACK feedback immediately upon detecting lost packets, then the packet recovery speed increases, but the risk of false NACK transmissions increases
Solution Approach 1:
The UE performs preliminary detection of packet loss at the RLC layer before triggering NACK transmission. This preliminary verification ensures that NACK feedback is only sent when actual packet loss is detected, preventing false NACK transmissions while enabling faster recovery compared to waiting for timer expiration.
Solution Approach 2:
The system implements a feedback mechanism where the UE monitors packet reception status and provides NACK feedback to the base station. This closed-loop feedback ensures that retransmissions are triggered only when necessary, maintaining reliability while improving recovery speed.
3Quantity of substance
If the UE buffers packets for extended periods waiting for retransmission, then the system maintains simple retransmission protocols, but the memory burden on the UE increases
Solution Approach 1:
By transmitting NACK feedback before the reassembly timer expires, the UE initiates retransmission earlier in the process. This reduces the duration for which packets need to be buffered, thereby decreasing the memory burden on the UE without requiring complex buffer management strategies.
4Ease of operation
If the system uses traditional timer-based NACK transmission, then the protocol remains simple and standardized, but the round-trip time increases
Solution Approach 1:
The UE transmits NACK feedback preliminarily, before the reassembly timer would normally expire. This approach maintains compatibility with existing timer-based protocols while reducing the effective round-trip time by initiating retransmission earlier in the process.
Solution Approach 2:
The system dynamically adjusts NACK transmission timing based on actual packet reception status. When packet loss is detected, the UE triggers NACK transmission earlier than the standard timer would allow, optimizing round-trip time while maintaining protocol simplicity for normal operations.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) determine that at least one packet of a set of packets for a downlink message is unsuccessfully received at a radio link control (RLC) layer of the UE due to a specific situation of a set of specific situations and may transmit the NACK message based on the missing packet (s) on an as needed basis rather than waiting for a timer to expire (e.g., a fast NACK mechanism). In some examples, the specific situations may include the UE missing packets after a measurement gap, missing packets based on wake up latencies for a discontinuous reception mode of the UE, missing packets due to interference from reference signals transmitted by neighboring cells, missing packets due to the UE not decoding retransmissions that have a same redundancy version (RV) of a downlink message, or a combination thereof.