Radio Communication Apparatus Equalizing ACK NACK Reception Quality
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Solution Overview
Problem
In radio communication systems, the interference between ACK and NACK signals from different mobile stations leads to a disparity in their received quality, with NACK signals being more susceptible to interference due to a higher error rate, resulting in poorer reception compared to ACK signals.
Innovation Solution
A radio communication apparatus and method that employs first and second spreading sections using sequences with different cyclic shift values and orthogonal sequences, respectively, and a rotating section to rotate the constellation of response signals by 90 degrees, ensuring equal received quality for ACK and NACK signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If code-multiplexing is performed by spreading response signals using ZAC sequences and Walsh sequences, then the number of multiplexed signals increases, but interference between ACK and NACK signals from different mobile stations increases, leading to disparity in received quality
Solution Approach 1:
The patent applies local quality by differentiating the treatment of ACK and NACK signals through separate constellation definitions. NACK signals use a constellation rotated 90 degrees relative to ACK signals, allowing the receiver to apply different correlation detection strategies for each signal type. This local differentiation in signal processing resolves the interference disparity while maintaining high multiplexing capacity.
Solution Approach 2:
The patent introduces asymmetry by using non-identical constellations for ACK and NACK signals. Specifically, the NACK constellation is rotated 90 degrees relative to the ACK constellation, creating an asymmetric signal structure that enables the receiver to distinguish and separately process these signal types, thereby reducing interference-induced quality disparity.
2Device complexity
If the same constellation is used for all response signals, then device complexity is reduced, but interference between different signal types cannot be mitigated, resulting in unequal error rates for ACK and NACK
Solution Approach 1:
The patent applies local quality by differentiating the treatment of ACK and NACK signals through separate constellation definitions. NACK signals use a constellation rotated 90 degrees relative to ACK signals, allowing the receiver to apply different correlation detection strategies for each signal type. This local differentiation in signal processing resolves the interference disparity while maintaining high multiplexing capacity.
Solution Approach 2:
The patent changes the constellation parameter (phase rotation) specifically for NACK signals while keeping ACK signals unchanged. This parameter modification creates distinct signal characteristics that enable separate detection and interference mitigation, achieving equal error rates without substantially increasing overall system complexity.
Data Source
AI summary
Provided is a radio communication device which can make Acknowledgement (ACK) reception quality and Negative Acknowledgement (NACK) reception quality to be equal to each other. The device includes: a scrambling unit (214) which multiplies a response signal after modulated, by a scrambling code “1” or “e−j(π/2)” so as to rotate a constellation for each of response signals on a cyclic shift axis; a spread unit (215) which performs a primary spread of the response signal by using a Zero Auto Correlation (ZAC) sequence set by a control unit (209); and a spread unit (218) which performs a secondary spread of the response signal after subjected to the primary spread, by using a block-wise spread code sequence set by the control unit (209).