Chapter 6
Standardization
6.1 3GPP Systems: UMTS and LTE
Advanced error-correcting schemes have been introduced into standards defining third-generation (3G) wireless systems. Turbo codes were introduced in the late 1990s in the UMTS specification, edited by 3GPP. They have also been included in the “cdma2000” standard, supported by 3GPP2. In both cases, binary turbo codes, based on eight-state constituent codes, have been specified. The 3GPP turbo code has a natural coding rate of 1/3, with generator polynomials (13,15)8, and is shown in Figure 6.1.
Figure 6.1 Structure of 3GPP turbo encoder
Trellis termination is performed with the addition of tail bits, padded at the end of each information block, which will enable the encoder to come back to its initial state at the cost of a slight loss in efficiency. This turbo code includes an internal block interleaver, in which bits are input row-wise in a rectangular matrix. Output bits are read out column-wise, after inter-row and intra-row permutation. The interleaver is defined for any information block size in the range 40–5114 bits. The 3GPP2 has a lower natural coding rate (1/5) and can cover information block sizes up to 8192 bits.
Discussions have been performed during Rel.8 the working group named “Long Term ...
