Table 3 Complexity evaluation of the SISO demapper and SISO decoder in terms of number and type of arithmetic computations and memory access

SISO rotated demapper with a priori input

Computation units

Number and type of operations per modulated symbol per demapping iteration

Euclidean distance

2^MAdd(18,18) + 2^{M + 1}Sub(8,10) + 2^{M + 1}Mul(18,18) + 2^{M + 1}Mul(8,10) + 2load(10) + (1 + 2^{M + 1})load(8)

A priori adder

$(2^M-2)\left\{E\right[\frac{M-1}{2}\left]\text{Add}\right(8,8)+E[\frac{M-1}{4}\left]\text{Add}\right(9,9)+E[\frac{M-1}{8}\left]\text{Add}\right(10,10)+M\text{Sub}(8,11)+M\text{Sub}(11,19\left)\right\}+M\text{load}\left(8\right)+(2^M-2)\text{load}\left(M\right)$

For QPSK M(2^M−2)Sub(11,19) + M load(8) + (2^M−2)load(M)

Minimum finder

M Sub(8,8) + M. 2^MSub(19,19) + M store(8)

SISO double binary turbo decoder

Computation units

Number and type of operations per coded symbol per turbo decoding iteration

Branch metric

4Add(5,5) + 38Add(5,10) + 4Sub(5,5) + 8load(5) + 6load(10)

State metric

64Add(10,10) + 48Sub(9,9) + 8store(10)

Extrinsic information

32Add(10,10) + 32Sub(9,9) + 9Sub(10,10) + 3Mul(4,10) + 8load(10) + 5store(10)