Design Switchable Precoded Space-Time Parallel Two-Path OFDM Systems

A 2x2 space-time (ST) orthogonal frequency division multiplexing (OFDM) system is proposed with parallel cancellation (PC) two-path transmission to form a 2x2 STPC system. The 2x2 STPC-OFDM systems mitigate the inter-carrier interference (ICI) in the mobile channels with a better BER than that of a 2x2 ST-OFDM system. The design is switchable between two operation modes: either high data rate with ST-OFDM or high reliability with STPC in mobile fading channels having lower bit error rate (BER). Furthermore, a generalized STPC architecture is designed with multiple receiver antennas. It offers higher diversity order and better BER. Two orthogonal transforms, such as Zadoff-Chu transform (ZCT) and Walsh–Hadamard transform (WHT), are employed as the precoder to enhance the BER further. Although the proposed STPC-OFDM systems require two-path transmission with the cost of reducing bandwidth efficiency, simulations show that the proposed 2x2 STPC-OFDM systems are robust to various channel environments and have a better BER performance for fair data rate comparison with 2x2 ST-OFDM.