| Summary: | 碩士 === 國立臺北科技大學 === 電腦通訊與控制研究所 === 92 === For wireless mobile communications, the problem is that how to transmit and receive signals effectively and reliably in a practice transmission channel; thereupon, a wideband wireless communication system should be able to combat the time-selective fading resulted from the high-speed movement and overcome the frequency-selective fading caused by the multipath propagation.
For the coherent transmission, the real-time channel state information (CSI) is required for demodulating the signals correctly. However, for a rapid fading channel, the accurate and real-time channel estimation is a difficult task. To avoid this, we consider the noncoherent transmission that employs the differential space-time block coding (DSTBC) to combat the time-selective fading. To obtain the best performance, the noncoherent maximum-likelihood sequence detector is studied. To avoid its high complexity, we also study its three special cases, namely, the noncoherent one-shot detector, the linearly predictive decision-feedback detector, and the linearly predictive Viterbi receiver.
To overcome the frequency-selective fading, we choose the orthogonal frequency division multiplexing (OFDM) technique, which divides the transmission bandwidth into many narrowband subcarriers, each of which exhibits an approximately flat fading.
In summary, combining the two advance transmission technique mentioned above, namely, the DSTBC and the OFDM, we construct the wideband wireless noncoherent 2IMO OFDM systems. Numerical results have revealed that satisfactory performances can be obtained even when the systems are operated in highly selective channels.
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