A reduced-complexity demapping algorithm for gray-labeled PSK constellations

This paper proposes a novel symbol-to-bit demapping algorithm for Gray-labeled phase shift keying (PSK) constellations. Unlike the Max-Log-MAP demapper, the proposed algorithm does not perform exhaustive search operations, but directly computes the soft information by exploiting the binary search and the symmetry of the Gray-labeled PSK constellations. Hence its complexity is remarkably reduced from the order of O(2 m ) of the Max-Log-MAP to O(M), where M denotes the number of bits per symbol. A pair of recent methods are used as bench markers in this paper. One of them reduces the complexity without any performance loss, while the other is a recursive method that reduces the complexity by approximating the original bit metric. It is shown that the proposed algorithm achieves a more substantial complexity reduction than the former bench marker. The proposed algorithm achieves a similar complexity reduction to the latter bench marker and yet, it does not suffer from any performance degradation.