MIMO ACK/NACK Coding With Nonlinear Codes for Lower Error Rates
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Solution Overview
Problem
Current MIMO systems in HSDPA face inadequate error protection for ACK/NACK messages, leading to higher error rates or increased transmit power, as the existing ten-bit repetition coding scheme is insufficient for multiple MIMO streams.
Innovation Solution
Implementing a nonlinear code set with specific properties such as C10,6,6 for two-stream, C10,10,5 for three-stream, and C10,16,4 for four-stream systems, which provide optimal error protection by maximizing the minimum Hamming distance between code words, allowing for more reliable ACK/NACK signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ten-bit repetition coding is used for ACK/NACK messages in MIMO systems, then the coding scheme is simple to implement, but error protection is insufficient leading to higher error rates
Solution Approach 1:
The patent changes the coding parameters from simple repetition coding to nonlinear block codes with specific properties (C10,4,6 for two-stream, C10,8,5 for three-stream, C10,16,4 for four-stream MIMO). This involves changing the code structure, minimum Hamming distance, and codebook design to achieve better error protection while maintaining 10-bit code length for compatibility with existing HS-DPCCH resources.
2Device complexity
If ten-bit repetition coding is used for ACK/NACK messages, then the coding structure is straightforward, but transmit power must be increased to maintain acceptable error rates
Solution Approach 1:
The patent optimizes coding parameters including minimum Hamming distance (d=6 for two-stream, d=5 for three-stream, d=4 for four-stream) and codebook size to achieve better error protection efficiency. This allows the system to maintain acceptable error rates with lower transmit power by using codes that provide better error detection and correction capability within the same 10-bit constraint.
3Reliability
If optimal error protection coding is implemented for MIMO ACK/NACK messages, then error rates are reduced and reliability is improved, but coding complexity increases
Solution Approach 1:
The patent pre-defines specific nonlinear codebooks (C10,4,6, C10,8,5, C10,16,4) with optimized properties for different MIMO stream configurations. These codebooks are designed in advance with specific minimum Hamming distances and code structures that balance error protection performance with implementation complexity. The receiver uses predetermined codebooks to decode, which simplifies the decoding process while maintaining optimal error protection.
4Reliability
If more coding bits are used to protect ACK/NACK messages, then error protection is improved, but available transmission resources are reduced
Solution Approach 1:
The patent optimizes the code length parameter to exactly 10 bits for all MIMO configurations (two-stream, three-stream, four-stream), which matches the available HS-DPCCH resources. By carefully selecting nonlinear codes with appropriate minimum Hamming distances and codebook sizes within this fixed 10-bit constraint, the patent achieves optimal error protection without requiring additional transmission resources.
Data Source
AI summary
Error protection based on a nonlinear code set may be used in a multiple input multiple output (MIMO) radio communications system. A decoder decodes received MIMO data streams and generates an automatic repeat request (ARQ) message for data units received for the MIMO data streams for each transmission time interval. An encoder codes the ARQ message using a code word from a nonlinear code set. At the data transmitter, which transmits one or more data units in transmission time intervals from two or more MIMO data streams, the ARQ message associated with the transmitted data units is decoded using a code word from the nonlinear code set.