Unequal Error Protection Nonbinary LDPC Codes for Bandwidth Efficient Transmission

A two-level unequal error protection scheme of nonbinary low-density parity-check (LDPC) codes for bandwidth-efficient coded modulation systems is proposed in order to allow bandwidth efficient transmissions. These two unequal error protection levels are originated from codeword characteristics and high order constellation, which make full use of different degrees of variable node and bit reliabilities of high order modulation. The information transformation is not needed if nonbinary LDPC code and high order modulation are matched in coded modulation systems. The systems can provide different reliabilities at symbol and bit levels to meet the requirement of symbol error rate and bit error rate for real-life system implementations. Simulation results show that the 16QAM modulation is always superior to the 16PSK modulation over an AWGN channel. The distinct unequal error protection is achieved considering the variable node degrees and high order modulation. The transmitted bits have different sensitivities to errors, and the important bits are protected strongly.