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This paper is concerned with constructions of nonbinary low-density parity-check(LDPC)codes for adaptive coded modulations(ACM).A new class of efciently encodable structured nonbinary LDPC codes are proposed.The defining parity-check matrices are composed of scalar circulant sub-matrices which greatly reduce the storage requirement when compared with random LDPC codes.With this special structure of paritycheck matrix,an efcient encoding algorithm is presented.Based on the proposed codes,a family of variablerate/variable-field nonbinary LDPC codes is designed for the ACM system.When combined with matched-size signal constellations,the family of constructed codes can achieve a wide range of spectral efciency.Furthermore,the resultant ACM system can be implemented via a set of encoder and decoder.Simulation results show that the proposed nonbinary LDPC codes for the ACM system perform well.
This paper is concerned with constructions of nonbinary low-density parity-check (LDPC) codes for adaptive coded modulations (ACM). A new class of efciently encodable structured nonbinary LDPC codes are proposed. The critical-check matrices are composed of scalar circulant sub-matrices which greatly reduce the storage requirement when compared with random LDPC codes. This particular structure of paritycheck matrix, an efcient encoding algorithm is presented.Based on the proposed codes, a family of variablerate / variable-field nonbinary LDPC codes is designed for the ACM system. Combined with matched-size signal constellations, the family of constructed codes can achieve a wide range of spectral efciency. Futurertherm, the resultant ACM system can be implemented via a set of encoder and decoder. Simulation results show that the proposed nonbinary LDPC codes for the ACM system perform well.