Radio Communication Apparatus Cyclic Phase Shift Resending
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Solution Overview
Problem
The existing resending control methods using Cyclic Delay Diversity (CDD) in radio communication systems fail to significantly enhance the synthesized gain during resending operations when the propagation state remains constant, leading to reduced throughput and ineffective frequency diversity due to unchanged frequency selectivity.
Innovation Solution
A radio communication apparatus and method that applies cyclic delay diversity and adjusts the phase shift and antenna mapping in response to the number of transmission times, introducing a phase offset to change the frequency characteristic and improve the independence of propagation paths, thereby enhancing the synthesized gain during resending operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resending control is applied with CDD, then the probability of successful reception is increased, but the synthesized gain becomes small when propagation state does not change, reducing throughput
Solution Approach 1:
The patent dynamically changes the phase shift amount assigned to each subcarrier based on the number of transmission attempts. During initial transmission, a first phase shift amount is applied, and during resending operations, a second different phase shift amount is applied. This dynamic adjustment modifies the frequency selectivity pattern across transmissions, ensuring that resending operations exploit different frequency diversity conditions even when the overall propagation state remains constant, thereby maintaining both high reliability and throughput.
2Reliability
If CDD is employed, then frequency diversity effect is achieved, but the frequency selectivity remains unchanged during resending operations, reducing synthesized gain
Solution Approach 1:
The patent changes the phase shift parameter in the CDD process based on the transmission attempt number. Specifically, it assigns different phase shift amounts to subcarriers during initial transmission versus resending operations. This parameter change modifies the frequency selectivity pattern, creating different frequency diversity conditions for each transmission attempt, thereby increasing the synthesized gain when multiple transmissions are combined at the receiver.
3Reliability
If the same packet is transmitted repeatedly, then the receiving station can try decoding with past information, but the transmission consumes more time and reduces efficiency
Solution Approach 1:
The patent implements dynamic phase shift adjustment that activates differently based on transmission status. During initial transmission, the system uses a first phase shift configuration optimized for first-attempt performance. When resending is triggered (indicating initial transmission failed), the system automatically switches to a second phase shift configuration. This dynamic adaptation ensures that resending operations have enhanced diversity conditions from the start, improving decoding success probability while minimizing the time penalty of retransmissions.
Data Source
AI summary
A synthesized gain in a resending operation can be improved significantly by relatively simple control when resending control is applied upon executing of a transmission diversity using CDD. A radio communication apparatus equipped with a plurality of antennas and for performing communication by MIMO, includes a phase shift amount assigning section 18 for executing a CDD process to assign a cyclic phase shift to a transmission signal on a frequency axis, a response signal demodulator 16 for demodulating ACK/NACK received from a destination station, and outputting control information about a resending operation when NACK is received and a reception is failed, and an initial phase controller 17 for setting an offset to a phase shift at a time of CDD process in response to a number of transmission times in resending control such that a predetermined offset, which is produced by adding a phase difference from a signal transmitted from other antenna to the phase shift, is assigned to a signal transmitted from the antenna over a full frequency band, wherein a frequency characteristic of a radio propagation path at a time of resending is changed every time of transmission times.