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 multi...
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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) blockcode 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.
In this paper, we present a space-time-frequency joint block coding (STFBC) scheme to exploit the essential space-time-frequency degrees of freedom of multiuser multiple-input-single-output multicarrier code-division ...
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In this paper, we present a space-time-frequency joint block coding (STFBC) scheme to exploit the essential space-time-frequency degrees of freedom of multiuser multiple-input-single-output multicarrier code-division multiple-access systems. Specifically, we use a series of orthogonal random codes to spread the space-timecode over several subcarriers to obtain multidiversity gains, whereas multiuser parallel transmission is applied over the same subcarriers by making use of multiple orthogonal code channels. Furthermore, to improve the system performance, we put forward to linear precoding the predetermined orthogonal STFBC, including transmitting directions selection and power allocation over these directions. We propose a precoder design method by making use of channel statistical information in time domain based on the Kronecker correlation model for the channels;thus, feedback amount can be largely decreased in multicarrier systems. In addition, we give the performance analysis from the perspectives of diversity order and coding gain, respectively. Moreover, through asymptotic analysis, we derive some simple precoder design methods, while guaranteeing a good performance. Finally, numerical results validate our theoretical claims.
A different and simple approach is proposed to compute the error rate performances of orthogonal space-time-frequency block codes over frequency-selective with m-coefficient Rayleigh fading channel bearing 2x1 and 2x2...
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ISBN:
(纸本)9781479944095
A different and simple approach is proposed to compute the error rate performances of orthogonal space-time-frequency block codes over frequency-selective with m-coefficient Rayleigh fading channel bearing 2x1 and 2x2 MIMO-OFDM systems. First, PDF of the instantaneous SNR at the receiver is derived and BER expression for BPSK and QPSK modulations is obtained. Then based on the Moment Generating Function (MGF) approach, exact expressions for SER of M-PSK and M-QAM modulations are attained. As theoretical and simulation results show, the orthogonal STFBC can achieve diversity order of LMTMR while quasi-orthogonal STFBC, for high SNRs does not achieve full space and multipath diversity gains available in the MIMO-OFDM channel.
By using multiple transmit antennas, wireless systems have a large capacity in time-varying multipath fading channels. space-timeblockcode (STBC), space-frequencyblockcode (SFBC), and space-time-frequency (STF) bl...
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By using multiple transmit antennas, wireless systems have a large capacity in time-varying multipath fading channels. space-timeblockcode (STBC), space-frequencyblockcode (SFBC), and space-time-frequency (STF) blockcode are well-known techniques in transmitter diversity schemes. While the SFBC (or the STF blockcoded) system gives full diversity at frequency-nonselective channels, it breaks down when used in a frequency-selective environment. This is because the SFBC (or the STF blockcode) scheme disregards frequency selectivity of the channel by assuming that channel frequency responses (CFRs) at adjacent subcarriers are the same. In this paper, we propose efficient channel estimation and symbol decoding methods, which consider the difference between CFRs at the adjacent subcarriers of the SFBC (or the STF blockcoded) orthogonal frequency division multiplexing (OFDM) system in multipath fading channels. The proposed method gives initial channel information by designing a simple training symbol, and the CFRs at all the subcarriers and the differences between the CFRs are easily calculated by using an interpolation method or a discrete Fourier transform (DFT) operation.
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