Architectures of 4x1 and 4x2 OFDM With Two-path Parallel ICI Cancellation Full-Rate Schemes in Mobile Channels

Further developing the idea of combining spatial diversity and parallel cancellation (PC) scheme together for mitigating intercarrier interference (ICI), we develop both 4x1 and 4x2 orthogonal frequency division multiplexing (OFDM) architectures with two-pair two-path PC schemes. First, the two-path PC scheme is integrated with the space-time-frequency (STF) block code OFDM transceiver to develop 4x1 and 4x2 STFPC-OFDM architectures in downlink. Given the same bandwidth efficiency and the same symbol size in modulation for transmission, the bit error rate (BER) of 4x1 and 4x2 STFPC-OFDM systems at a full-rate outperforms that of 4x1 and 4x2 STF-OFDM systems at a half-rate using both QPSK and 16-QAM modulations in high-speed mobile channels. This two-pair STFPC-OFDM architecture provides both diversity and block coding gains to mitigate ICI and lower BER. Additionally, the total number of computational requirements for the full-rate 4x1 STFPC-OFDM transceiver is half that of the rate half 4x1 STF-OFDM transceiver. Moreover, the orthogonal Walsh–Hadamard (WH) transform is employed as a pre-coder to develop 4x1 and 4x2 WHSTF-OFDM and WHSTFPC-OFDM systems. The BER of WHSTFPC-OFDM systems at a full-rate outperforms that of WHSTF-OFDM systems at a half-rate in QPSK and 16-QAM modulations. The 4x1 and 4x2 WHSTFPC-OFDM schemes are simple and can be generalized to multiple input and multiple output (MIMO), such as 4x4 and 4x8 MIMO-OFDM ones. They may serve as basic modules for the fifth generation, and future broadcast systems.