Semi-Persistent Scheduling HARQ Process Management
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Solution Overview
Problem
In wireless communication systems like LTE, semi-persistent scheduling for VoIP traffic faces challenges in managing HARQ processes without using PDCCH signaling, leading to limited re-transmissions and potential performance deterioration due to the need for increased HARQ processes or complexity.
Innovation Solution
The solution involves configuring RRC signaling to include a HARQ process number and periodicity pattern for semi-persistent allocations, allowing for multiple HARQ processes to be reserved and identified, and using additional bits in PDCCH signaling to indicate semi-persistent allocations, thereby avoiding the limitations of traditional HARQ process ID reliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semi-persistent scheduling is used for VoIP traffic, then control signaling overhead is reduced and system capacity increases, but the number of possible re-transmissions is limited due to HARQ process management constraints
Solution Approach 1:
The patent segments the HARQ process management by introducing separate uplink and downlink HARQ process counters (UL_HARQ计数器 and DL_HARQ计数器), allowing independent tracking and management of re-transmissions in each direction. This segmentation enables the system to maintain semi-persistent scheduling benefits while extending re-transmission capabilities through dedicated counter management for each HARQ direction.
2Reliability
If multiple HARQ processes are reserved for semi-persistent scheduling, then re-transmission capability is improved, but device complexity and signaling requirements increase
Solution Approach 1:
The patent implements self-service mechanisms where the UE autonomously manages HARQ process identification using locally maintained counters (UL_HARQ计数器 and DL_HARQ计数器) and the pre-configured parameter N. The system eliminates the need for explicit network signaling for each HARQ process assignment, as the UE independently determines the appropriate HARQ process based on the counter values and periodicity, thereby reducing signaling overhead and management complexity.
Solution Approach 2:
The patent introduces a configurable parameter N that defines the number of HARQ processes reserved for semi-persistent scheduling. By allowing this parameter to be adjusted based on traffic requirements and system conditions, the system can optimize the balance between re-transmission capability and resource allocation without hardcoding complex management structures. The parameter N enables flexible adaptation of HARQ process counts to match actual service needs.
3Ease of operation
If traditional HARQ process ID reliance is used, then signaling is simplified, but the number of re-transmissions is limited and performance deteriorates
Solution Approach 1:
The patent introduces intermediary counter mechanisms (UL_HARQ计数器 and DL_HARQ计数器) that mediate between the simple periodic scheduling structure and the complex HARQ re-transmission requirements. These counters serve as intermediaries that track the number of re-transmissions without requiring complex signaling, bridging the gap between signaling simplicity and re-transmission reliability by providing implicit state tracking through counter values that both the network and UE can independently determine.
Data Source
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AI summary
One or more hybrid automatic repeat request process identifications are configured for scheduling without associated control signaling. A particular HARQ process ID to be assumed for a given subframe is determined based on at least one of: a) system frame number; b) number of hybrid automatic repeat request processes that are allocated for semi-persistent scheduling; and c) periodicity for semi-persistent scheduling. In various embodiments: a) is broadcast and b) and c) are sent via RRC signaling; and the assumed particular HARQ process ID is determined as a function of [Current TTI/SP_Period] mod Num_SP_HARQ:wherein Current TTI is a number for the given subframe derived from the system frame number and the term [Current TTI/SP_Period] is rounded to an integer prior to the modulo operation; SP_Period is the periodicity of the semi-persistent scheduling; and Num_SP_HARQ is the number of hybrid automatic repeat request processes that are allocated for semi-persistent scheduling.