First, for given symbol length m and codeword length n, we determine the optimal codebook with the least average number of high bits per codeword and give the corresponding average codeword weight as a function of m and n.
The terminology (n,k,t) of the block code indicates the codeword length n, dataword length k, and the error correction capability as t bits per codeword.
denotes the message of user, of length symbols, that is, bits. is the codeword of user, of length symbols, that is, bits, constant for all users.
Table 1 shows the number of uncoded bits, codeword length, uncoded bit to coded symbol rate R s and the uncoded bit to coded bit rate R c (code rate) for different n.
Table 2 shows the number of uncoded bits, codeword length, the uncoded bit to coded symbol rate R s and code rate R c for different 2n.
This gain increases with the number of fading blocks per codeword.
The Huffman coding [ 12, 13], invented in 1952, is a statistical method, which assigns a sequence of bits (a codeword) to each alphabet symbol.
This paper presents a quasi-cyclic low-density parity-check (LDPC) coded OFDM system, in which the redundant bits of each codeword are mapped to a higher-order modulation constellation.
The N bits of a codeword are represented in the systematic form, divided in information bits (IN) and parity-check bits (PN) given by the number of columns of A and B, respectively.
Next, in the transmission phase, is block-encoded into a length- codeword in codebook at a rate of bits per sample.
