802.11n MIMO LDPC Coding With Phase-Offset Subcarriers
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Solution Overview
Problem
MIMO systems face interference issues due to co-channel interference, which limits data throughput and signal quality, and existing error correction codes are not effectively chosen to mitigate these interferences.
Innovation Solution
Implementing Low Density Parity Check (LDPC) codes in an IEEE 802.11 standard system for MIMO schema, where a base LDPC code is transmitted on specified and offset phases across multiple sub-carriers, using a structured parity check matrix to facilitate efficient decoding and error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MIMO systems transmit more data to increase throughput, then data throughput is improved, but co-channel interference increases and signal quality deteriorates
Solution Approach 1:
The patent applies parameter changes by carefully selecting LDPC code parameters (code rate, block length, parity check matrix structure) to optimize performance in MIMO systems. The parity check matrix is designed with specific properties (progressive edge growth algorithm) to minimize interference effects and maximize throughput while maintaining signal quality
2Reliability
If traditional FEC codes are used in MIMO systems, then error correction is provided, but the codes cannot be chosen randomly and frequency reassignment is required which is limited by standards
Solution Approach 1:
The patent segments the error correction function into specific LDPC code structures with defined properties. The parity check matrix is constructed using progressive edge growth algorithm that divides the code construction into manageable steps, allowing systematic selection of codes that work effectively in MIMO systems without requiring frequency reassignment
Solution Approach 2:
The patent enables versatile code selection by allowing different LDPC code parameters (rate, length, structure) to be chosen based on channel conditions and system requirements, providing both reliability and adaptability in MIMO communications
3Productivity
If LDPC codes are implemented in MIMO systems with multiple antennas and sub-carriers, then data throughput and signal quality are enhanced, but system complexity increases
Solution Approach 1:
The patent segments the LDPC decoding process into parallel operations that can be efficiently implemented in hardware. The parity check matrix structure enables decomposition of the decoding task into manageable check node and variable node operations, reducing circuit complexity while maintaining high throughput performance
Data Source
AI summary
Method and apparatus for implementing LDPC codes in an IEEE 802.11 standard system configured to operate in a Multiple-Input, Multiple-Output (MIMO) schema. A method in accordance with the present invention comprises defining a base LDPC code, having a length equal to an integer number of data carriers in an ODFM symbol, transmitting the base LDPC code over a plurality of sub-carriers, wherein the base code is transmitted at an expected phase on sub-carriers specified by the IEEE 802.11 standard system, and transmitting the base LDPC code on other sub-carriers than those specified by the IEEE 802.11 standard system, wherein the base LDPC code on the other sub-carriers is transmit offset in phase from the base LDPC code on the specified sub-carriers.