Base Station HARQ-ACK Resource Allocation for Mixed RTTs
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Solution Overview
Problem
In wireless communication systems, the shortened Round Trip Time (RTT) for Hybrid Automatic Repeat Request (HARQ) in LTE-Advanced can lead to conflicts in resource allocation for HARQ-ACK transmissions due to differing RTTs among terminal apparatuses, causing overlapping and incorrect reception of acknowledgements.
Innovation Solution
A base station apparatus determines and notifies terminal apparatuses of specific resource indices for HARQ-ACK transmission based on their individual RTTs, using methods such as index offsets or predefined sets to avoid resource conflicts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the HARQ RTT is shortened in LTE-Advanced, then the communication efficiency is improved, but resource conflicts occur in HARQ-ACK transmissions due to differing RTTs among terminal apparatuses
Solution Approach 1:
The patent applies parameter changes by allowing different HARQ RTT values for different terminal apparatuses. The base station configures specific RTT parameters for each terminal based on their individual characteristics, enabling shortened RTT for some terminals while maintaining proper resource allocation. This resolves the contradiction by making the RTT parameter variable rather than fixed, thus improving efficiency without causing resource conflicts.
Solution Approach 2:
The patent segments the resource allocation by associating different resource indices with different HARQ RTT values. Each terminal apparatus with a specific RTT is assigned dedicated resources (resource blocks, code resources) that are distinct from terminals with other RTT values. This segmentation prevents resource conflicts while allowing different RTT configurations, thus maintaining both efficiency and reliability.
2Device complexity
If resource allocation is based on CCE start index only, then the allocation method is simple, but resource conflicts occur when terminals with different RTTs transmit HARQ-ACK at the same timing
Solution Approach 1:
The patent extends the resource allocation from a single dimension (CCE start index only) to multiple dimensions by introducing RTT-based resource indexing. The resource allocation now considers both the CCE start index and the HARQ RTT value, creating a two-dimensional resource space. This allows terminals with different RTTs to be allocated distinct resources even when their CCE start indices coincide, preventing resource conflicts while maintaining allocation simplicity.
Solution Approach 2:
The patent changes the resource allocation parameters from using only CCE start index to using a combination of CCE start index and HARQ RTT value. By introducing RTT as an additional parameter in the resource determination formula, the system can distinguish between terminals with different RTTs and allocate unique resources to each, thus avoiding collisions while keeping the allocation method straightforward.
Data Source
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AI summary
There is provided a base station apparatus capable of transmitting a signal to a terminal apparatus and receiving an acknowledgement from the terminal apparatus. The base station apparatus transmits, to the terminal apparatus, information pertaining to a resource to be used to transmit the acknowledgement and determined in accordance with a length of a period from when the signal is transmitted to the terminal apparatus until the acknowledgement is received, and receives the acknowledgement transmitted by the terminal apparatus using the resource by specifying the resource based on the information.