Lifting LDPC Matrix for MIMO Space-Time Coding
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Solution Overview
Problem
Current wireless communication systems face challenges in achieving high reliability and low error rates, particularly in multi-media services, due to the complexity and time delay associated with turbo codes, and the difficulty in implementing low density parity check (LDPC) codes for 4th generation wireless communication systems.
Innovation Solution
The use of lifting low density parity check codes to improve correlation between bit arrays transmitted through multiple antennas, expanding LDPC codes according to the number of antennas, and employing a lifting LDPC matrix to enhance coding and decoding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If turbo codes are used for channel coding, then reliability and error correction performance are improved, but device complexity and time delay increase
Solution Approach 1:
The patent replaces complex turbo codes with simpler LDPC codes that achieve comparable error correction performance with reduced complexity. The lifting LDPC structure uses lightweight parity check matrices that can be efficiently implemented with less computational resources and lower device complexity while maintaining reliability.
Solution Approach 2:
The patent transforms the parity check matrix parameters by using lifting construction where a base matrix is expanded through lifting factor Z. This parameter transformation allows the system to achieve high coding rates and good error correction performance without the iterative decoding complexity of turbo codes, effectively changing the coding parameters to reduce device complexity.
2Device complexity
If conventional LDPC codes are implemented, then device complexity is reduced, but coding performance and reliability are insufficient for 4th generation wireless communication systems
Solution Approach 1:
The patent introduces a new dimension to LDPC codes through lifting construction. By expanding the base parity check matrix through lifting factor Z, the system creates a higher-dimensional code structure that achieves better error correction performance suitable for 4th generation systems while maintaining the low complexity advantage of LDPC codes.
Solution Approach 2:
The patent creates a composite coding structure by combining lifting construction with space-time coding. The lifting LDPC codes are integrated with space-time block codes to form a composite coding scheme that achieves superior reliability for MIMO systems while keeping device complexity manageable through the structured lifting approach.
3Reliability
If the number of transmission antennas is increased, then data transmission reliability is improved, but the complexity of space-time coding increases
Solution Approach 1:
The patent creates a universal lifting LDPC coding framework that can accommodate any number of transmission antennas through the lifting factor Z. The same base matrix structure can be lifted to support different antenna configurations, providing multi-functionality and reducing the need for separate coding schemes for each antenna count, thereby managing complexity while maintaining reliability.
Solution Approach 2:
The patent introduces dynamic adaptability through the lifting factor Z, which can be adjusted based on the number of transmission antennas and channel conditions. This dynamic parameter allows the coding scheme to adapt to different MIMO configurations, optimizing performance for each scenario without requiring completely different coding structures, thus managing complexity across varying system configurations.
Data Source
AI summary
A mobile communication system and method for transmitting signals through a plurality of transmission antennas by space-time coding the signals. The signals are transmitted using a low density parity check code. A lifting low density parity check matrix is formed by expanding values of elements in a low density parity check matrix with a sub-matrix corresponding to a number of the transmission antennas. The signals to be transmitted are coded using the lifting low density parity check matrix. Thereafter, the coded signals are serial/parallel converted and transmitted through the transmission antennas.