HARQ Process Identifier for Semi-Persistent Scheduling
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Solution Overview
Problem
In mobile radio communications systems, semi-persistent scheduling introduces challenges in matching dynamically-scheduled retransmissions with initially-transmitted HARQ processes, leading to increased error rates and decreased throughput due to the lack of explicit HARQ process identification.
Innovation Solution
Associating each semi-persistent radio resource with a specific HARQ process identifier, which is communicated to the user equipment (UE) through configuration or scheduling messages, allowing the UE to correctly match retransmissions with initial transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If semi-persistent scheduling is used to reduce signaling overhead, then signaling overhead is reduced, but the ability to correctly match retransmissions with initial transmissions deteriorates due to lack of explicit HARQ process identification
Solution Approach 1:
The system pre-associates each semi-persistent radio resource with a specific HARQ process identifier before data transmission begins. This preliminary association is configured through higher-layer signaling (RRC or MAC CE) so that when data is transmitted on the semi-persistent resource, the receiving UE already knows which HARQ process to use for matching retransmissions, eliminating the need for explicit HARQ process identification in dynamic scheduling messages.
Solution Approach 2:
The HARQ process identifier acts as an intermediary that links the semi-persistent radio resource to the correct HARQ process. Instead of directly matching retransmissions through complex timing relationships or resource patterns, the system uses the HARQ process ID as a mediator that both transmitting and receiving entities use to correctly associate initial transmissions with their retransmissions.
2Reliability
If dynamic scheduling is used for each transmission, then HARQ process identification is accurate, but signaling overhead increases substantially
Solution Approach 1:
The system performs the HARQ process assignment in advance through higher-layer configuration messages (RRC Connection Reconfiguration or MAC Control Element). This preliminary action establishes the HARQ process identifier association before data transmission begins, so that subsequent data transmissions on semi-persistent resources do not require repeated signaling of the HARQ process ID, thereby reducing signaling overhead while maintaining identification accuracy.
3Adaptability or versatility
If semi-persistent resources are allocated without explicit HARQ process association, then resource allocation flexibility is improved, but error rates increase due to mismatched retransmissions
Solution Approach 1:
The system pre-configures the association between semi-persistent radio resources and HARQ process identifiers through higher-layer signaling before data transmission begins. This allows the system to maintain flexible resource allocation (semi-persistent scheduling) while ensuring that both transmitting and receiving entities correctly identify which HARQ process corresponds to each semi-persistent resource, thereby preventing mismatched retransmissions and reducing error rates.
Data Source
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AI summary
A radio communications link is established between radio stations, and a semi-persistent radio resource is allocated to support data transmission over the communications link. The semi-persistent radio resource is associated with a corresponding automatic repeat request (ARQ) process identifier. Non-limiting examples of a semi-persistent radio resource include a regularly scheduled transmission time interval, frame, subframe, or time slot during which to transmit a data unit over the radio interface. Retransmission is requested of a data unit transmitted using the semi-persistent radio resource. The ARQ process identifier associated with the semi-persistent resource is used to match a retransmission of a data unit dynamically scheduled on the communications link with the requested data unit retransmission. In a preferred example embodiment, the ARQ process identifier is a hybrid ARQ (HARQ) process, where a retransmitted data unit is combined with a previously-received version of the data unit.