HARQ Process Allocation for DL Semi-Persistent Scheduling
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Solution Overview
Problem
In LTE wireless communication systems, the ambiguity in HARQ process allocation for downlink Semi-Persistent Scheduling (SPS) leads to incorrect HARQ combining during SPS transmission, affecting throughput, especially in scenarios like VOIP, where reserved HARQ processes are not efficiently utilized, causing data loss and reduced Dynamic Scheduling (DS) performance.
Innovation Solution
A method for HARQ process allocation that configures and circularly uses HARQ processes for SPS transmission, allowing allocation to DS transmissions when idle, and determines transmission types based on preset criteria, eliminating the need for dedicated HARQ process reservation, thereby reducing ambiguity and enhancing DS throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple dedicated HARQ processes are reserved for SPS transmission, then HARQ combining accuracy is improved, but DS throughput deteriorates due to unavailable HARQ processes
Solution Approach 1:
The patent makes HARQ processes universal by allowing them to serve both SPS and DS functions. Instead of dedicating specific HARQ processes to SPS, the system allows any HARQ process to be used for SPS transmissions when needed, and for DS when not in use for SPS. This multi-functionality resolves the contradiction by eliminating the need for permanent reservation while maintaining reliability.
Solution Approach 2:
The patent introduces dynamic HARQ process allocation where the assignment of HARQ processes to SPS or DS changes based on real-time needs. When SPS transmission occurs, the corresponding HARQ process is used; when SPS is inactive, the HARQ process becomes available for DS. This dynamic approach allows the system to adapt resource allocation to current traffic conditions, improving both reliability and throughput.
2Reliability
If HARQ processes are reserved for SPS transmission, then SPS transmission reliability is improved, but resource utilization deteriorates during silence periods
Solution Approach 1:
The patent implements a mechanism where HARQ processes are temporarily 'discarded' from dedicated SPS reservation and made available for DS usage during SPS silence periods. When SPS transmission is not active (e.g., during VOIP silence periods), the HARQ processes that would have been reserved are recovered and made available for DS transmissions, thus eliminating waste while maintaining SPS reliability when needed.
Solution Approach 2:
The system dynamically adjusts HARQ process allocation based on SPS activity status. During active SPS transmission, dedicated HARQ processes are used to ensure reliability. During silence periods when SPS is inactive, the allocation dynamically changes to allow DS usage, preventing resource waste while maintaining the ability to quickly resume SPS when needed.
3Device complexity
If one dedicated HARQ process is reserved for SPS, then device complexity is reduced, but ambiguity resolution reliability deteriorates
Solution Approach 1:
The patent introduces feedback mechanisms (such as NDI - New Data Indication) that provide explicit information to the UE about which HARQ process is being used for SPS transmission. This feedback allows the UE to correctly identify and combine data even when HARQ processes are shared between SPS and DS, resolving ambiguity without requiring dedicated processes and thus maintaining low complexity while improving reliability.
Data Source
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AI summary
According to the present invention, there is proposed a method for HARQ process allocation for DL SPS transmission between a base station and an UE, and a system thereof. The method comprises steps of: at the base station side, configuring a HARQ process preserved for the SPS transmission and its related control information based on RRC or other control instructions from the upper layer, and transmitting the configured HARQ process and its related control information to the UE; sending down an SPS-CRNTI-based PDCCH to activate SPS configuration and indicating a HARQ process for a first SPS transmission before the first SPS transmission; determining a HARQ process allocated to the current transmission, and allocating the HARQ process preserved for the SPS transmission to possible DS transmissions when the SPS transmission is in idle; and determining a type for transmission or retransmission to be carried in the current HARQ process based on a preset criteria, then performing the determined type of transmission or retransmission, and correspondingly sending a PDCCH down; at the UE side, receiving the RRC or other control instructions from the base station; receiving PDCCH from the base station to activate SPS configuration and obtaining the time for the first SPS transmission and used HARQ process; receiving respective data transmission or retransmission and possible PDCCH from the base station; and determining a type for the received data transmission or retransmission based on a preset criteria, so as to perform respective data combination. The method and system according to the present application achieve HARQ process allocation for DL SPS transmission, while improving the DS transmission chance and reducing the ambiguity between different SPS transmissions and between SPS transmission and DS transmission.