Dynamic Frequency Resource Allocation for Semi-Persistent Scheduling
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Solution Overview
Problem
In wireless communication networks using LTE, semi-persistent scheduling (SPS) and HARQ retransmissions often result in collisions between SPS UE transmissions, leading to increased PDCCH resource utilization and delay due to adaptive retransmissions, which counteract the resource savings of SPS and degrade VoIP quality.
Innovation Solution
A method and RBS configuration that dynamically allocate frequency resources for SPS transmissions, using a hopping concept to avoid synchronized collisions by changing frequency resource sets every round trip time value, ensuring non-adaptive HARQ retransmissions do not collide with initial SPS transmissions, thereby minimizing PDCCH resource consumption and reducing potential delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SPS scheduling is used to reduce PDCCH signaling load, then PDCCH resource usage is reduced, but HARQ retransmission collisions increase leading to adaptive retransmissions that require PDCCH signaling
Solution Approach 1:
The patent applies dynamics by making the frequency resource allocation dynamic rather than static. The eNodeB dynamically switches between at least two different frequency resource sets for SPS transmissions based on the timing of HARQ retransmissions. This dynamic adjustment prevents collisions between SPS transmissions and HARQ retransmissions, allowing the system to maintain the PDCCH resource savings of SPS while avoiding the reliability issues of resource collisions.
Solution Approach 2:
The patent applies preliminary action by having the eNodeB determine and prepare multiple frequency resource sets in advance before collisions occur. The system pre-calculates which frequency set to use based on the HARQ timing information, ensuring that when a collision would occur, the frequency resources are already switched to avoid the collision. This proactive approach prevents the need for adaptive retransmissions while maintaining SPS efficiency.
2Reliability
If adaptive retransmissions are used to avoid frequency collisions, then retransmission reliability is improved, but PDCCH resource consumption increases counteracting SPS benefits
Solution Approach 1:
The system dynamically adjusts frequency resource allocation based on the timing of SPS transmissions and HARQ retransmissions. By switching between multiple frequency sets, the system ensures that retransmissions can occur without collisions while avoiding the need for adaptive retransmissions that would consume PDCCH resources. This dynamic approach maintains reliability without the resource cost.
Solution Approach 2:
The eNodeB performs preliminary determination of frequency resource sets and prepares switching decisions in advance. By having the frequency allocation strategy pre-planned based on HARQ timing, the system ensures reliable retransmissions without needing to trigger adaptive retransmissions that would increase PDCCH consumption. The preliminary setup prevents the need for resource-consuming adaptive retransmissions.
3Device complexity
If frequency resources are allocated statically for SPS, then scheduling simplicity is maintained, but collisions with HARQ retransmissions occur continuously
Solution Approach 1:
The patent introduces a relatively simple dynamic mechanism where the eNodeB switches between at least two frequency resource sets based on HARQ timing. This dynamic approach is not overly complex - it involves determining which frequency set to use and switching accordingly - but it effectively prevents collisions between SPS transmissions and HARQ retransmissions, achieving reliability without excessive complexity.
Solution Approach 2:
The system performs preliminary determination of frequency resource allocation strategy based on HARQ timing information before collisions occur. By pre-calculating which frequency set to use, the system avoids collisions without requiring complex real-time decision-making. This preliminary planning approach maintains scheduling simplicity while achieving collision-free transmissions.
Data Source
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AI summary
The present invention relates to a method for allocating frequency resources for at least two wireless devices in a cell of a wireless communication network. SPS transmissions and automatic retransmissions are applied for the at least two wireless devices. A time difference between an SPS transmission and an automatic retransmission related to the SPS transmission is determined by a round trip time value. The method is performed in a radio base station serving the cell. The method comprises determining (510) at least two different sets of frequency resources for the SPS transmissions of the at least two wireless devices. The method also comprises allocating (520) frequency resources for the SPS transmissions of the at least two wireless devices within an SPS period, such that the allocated frequency resources change between two of the at least two different sets every round trip time value.