HARQ Receiver Duplicate Detection and Re-ordering
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Solution Overview
Problem
Wireless communication systems using HARQ face challenges in duplicate detection and re-ordering of packets due to high error rates in ACK transmissions, leading to duplicate packets and delayed delivery of correctly decoded packets to upper layers.
Innovation Solution
The implementation of multiple ARQ channels with synchronized transmission times allows for duplicate detection by tracking unexpected subpacket identifiers and re-ordering by determining the presence of pending earlier packets based on correctly decoded packets across channels, ensuring efficient delivery of packets to upper layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the receiver HARQ entity buffers packets to re-order them in sequence, then packet delivery order is improved, but delivery delay increases
Solution Approach 1:
The receiver HARQ entity proactively declares packets as lost after a maximum number of transmission attempts, rather than waiting indefinitely for re-ordering. This preliminary action prevents excessive buffering delays while maintaining acceptable delivery order through the combination of sequential transmission and timely loss declaration.
2Loss of time
If the receiver declares packets as lost early to reduce buffering delay, then delivery delay is reduced, but packet loss rate increases
Solution Approach 1:
The system changes the parameter of maximum transmission attempts from an implicit unlimited value to an explicit finite limit. This parameter change enables the receiver to distinguish between temporarily delayed packets and permanently lost packets, reducing false loss declarations while maintaining timely delivery for successfully received packets.
3Reliability
If multiple subpackets are transmitted for erased packets to improve reliability, then data transmission reliability is improved, but duplicate packet rate increases due to ACK errors
Solution Approach 1:
The receiver HARQ entity uses feedback based on sequence numbers and transmission attempt counts to identify and discard duplicate packets. When a packet is received, the system checks whether it is a duplicate by comparing with previously received packets and transmission history, thereby eliminating duplicates while preserving the reliability benefits of multiple subpacket transmissions.
Data Source
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AI summary
Techniques for performing duplicate detection and re-ordering for a HARQ transmission are described. For duplicate detection, a receiver determines whether a decoded packet x for an ARQ channel y is a duplicate packet based on packet x and a prior decoded packet for ARQ channel y. For re-ordering, the receiver determines whether an earlier packet is still pending on any other ARQ channel based on prior decoded packets for the ARQ channels and forwards packet x only if there are no pending earlier packets. There are no pending earlier packets on another ARQ channel z if (1) a decoded packet was received on ARQ channel z at a designated time or later or (2) a decoded packet was not received on ARQ channel z within a time window from current time.