PHICH Resource Collision Avoidance in LTE Terminals
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Solution Overview
Problem
In wireless communication systems, particularly in LTE-Advanced, the increased number of aggregated carriers leads to collisions of physical hybrid-ARQ indicator channel (PHICH) resources, making it difficult for terminals to appropriately receive acknowledgement/not-acknowledgement (ACK/NACK) signals for uplink data channels, especially when multiple uplink cells share the same resource index.
Innovation Solution
A method where a terminal determines whether a first PHICH resource collides with a second PHICH resource by comparing their lowest physical resource block (PRB) indices and cyclic shift indices, and applies an offset value, such as a lowest control channel element (CCE) index or carrier indicator field (CIF) value, to determine a new PHICH resource, preventing collisions and ensuring accurate ACK/NACK reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of aggregated carriers is increased to support higher data rates, then the data rate capability is improved, but PHICH resource collisions occur making ACK/NACK reception unreliable
Solution Approach 1:
The PHICH resource space is segmented by introducing an additional determination dimension using downlink cell indices. Instead of a single shared PHICH resource pool, the system divides resources across multiple downlink cells, each providing dedicated PHICH resources for their scheduled uplink cells. This segmentation prevents collisions even when multiple uplink cells use the same PRB and cyclic shift combinations.
Solution Approach 2:
The downlink cell index acts as an intermediary parameter in the PHICH resource determination process. By incorporating this intermediate index into the resource calculation formula, the system mediates between multiple uplink cells that would otherwise collide for the same PHICH resources, distributing them across different downlink cell-specific resource pools.
2Device complexity
If multiple uplink cells share the same resource index to simplify scheduling, then the scheduling complexity is reduced, but PHICH resource collisions occur
Solution Approach 1:
The PHICH resource determination is extended from a two-dimensional space (PRB index and cyclic shift index) to a three-dimensional space by adding the downlink cell index as a new dimension. This dimensional expansion allows multiple uplink cells to share the same PRB and cyclic shift indices while still achieving unique PHICH resource allocation through the additional downlink cell index parameter.
Data Source
AI summary
Provided are a method for a terminal for receiving a PHICH in a wireless communication system and a terminal utilizing the method. The method is characterized in that a PUSCH is transmitted, whether or not a first PHICH resource corresponding to the PUSCH collides with a second PHICH resource corresponding to a different PUSCH is determined, and the PHICH for the PUSCH is received from the PHICH resource determined on the basis of the result of the determination, wherein if the first PHICH resource and second PHICH resource do collide, then the PHICH for the PUSCH is received from a new PHICH resource determined by utilizing an offset value.