A Dual QPSK Soft-demapper for ECMA-368 Exploiting Time-Domain Spreading and Guard Interval Diversity

When considering the relative fast processing speed and low power requirements for wireless personal area networks (WPAN) and wireless universal serial bus (USB) consumer based products, then the efficiency and cost effectiveness of these products become paramount. This paper presents an improved soft-output QPSK demapper suitable for the products above that not only exploits time diversity and guard carrier diversity, but also merges the demapping and symbol combining functions together to minimize CPU cycles, or memory access dependant upon the chosen implementation architecture. The proposed demapper is presented in the context of multiband OFDM version of UWB (ECMA-368) as the chosen physical implementation for high-rate wireless USB.