Since in BICM the bit-based minimum Hamming distance (the number of different bits between the erroneous path in the shortest error event and the correct path)is maximized, BICM will give a lower BER in Rayleigh fading n that of TCM that maximize the FED.In ther words,for the same compexity BICM achieves better code e diversity (1.e. the minimum Hamming distance),while TCM achieves better minimum Euclidean distance. In fact,the three separate bit interleavers of size K can be replaced by a single bit-interleaver with size of 3K,resulting in a generic BICM scheme as shown in Fig.5.11.1(c).In general,a BICM transmitter comprises an encoder for a binary code C.a"bit interleaver,"and a signal mapper.The output sequence of the bit interleaver is segmented into m-bit blocks,which are mapped to a 2-point signal constellation using Gray coding.The BICM decoder implements the inverse process,as shown in Fig.5.11.1 (c).Good performance close to capacity can be obtained if C is a long Turbo code or LDPC code. Conv. Signal Channel mapper interleaver (a)TCM scheme for fading ch nnels Bit interleaver Conv 8-PSK Encode Bit interleaver rate-2/3 mapper Bit interleaver (b)Zehavi's BICM for 8-PSK Binary Bit interleaver Signal encoder mapper Equivalent Channel Binary De-interleaver De- ecoder mapper (c)A general BICM scheme Figure5.l1.1 5.11.I BICM-ID BICM can be viewed as a special type of SCCC,and the "inner code"is the symbol 21 21 Since in BICM the bit-based minimum Hamming distance (the number of different bits between the erroneous path in the shortest error event and the correct path) is maximized, BICM will give a lower BER in Rayleigh fading channels than that of TCM that maximizes the FED. In other words, for the same complexity BICM achieves better code diversity (i.e., the minimum Hamming distance), while TCM achieves better minimum Euclidean distance. In fact, the three separate bit interleavers of size K can be replaced by a single bit-interleaver with size of 3K, resulting in a generic BICM scheme as shown in Fig. 5.11.1 (c). In general, a BICM transmitter comprises an encoder for a binary code C, a “bit interleaver,” and a signal mapper. The output sequence of the bit interleaver is segmented into m-bit blocks, which are mapped to a 2m-point signal constellation using Gray coding. The BICM decoder implements the inverse process, as shown in Fig. 5.11.1 (c). Good performance close to capacity can be obtained if C is a long Turbo code or LDPC code. Channel interleaver Conv. encoder Signal mapper (a) TCM scheme for fading channels Conv. Encoder rate-2/3 8-PSK mapper Bit interleaver Bit interleaver Bit interleaver (b) Zehavi’s BICM for 8-PSK Binary Bit interleaver encoder Signal mapper π b Equivalent Channel De￾mapper Binary De-interleaver decoder 1 π b − (c) A general BICM scheme Figure 5.11.1 5.11.1 BICM-ID BICM can be viewed as a special type of SCCC, and the “inner code” is the symbol