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| Study on Quasiª²Orthogonal Time Division
Multiplexing in Multipath Fading Channels Sun Enchang,Yi Kechu,Wang Yong,Tian Bin (State Key Laboratory of Integrated Service Networks, Xidian University£¬Xi'an 710071£¬China) Abstract£ºBased on the principle of timeª²frequency duality of Fourier transform, the quasiª²orthogonal time division multiplexing (QOTDM) was proposed, which employed the shift orthogonal property of the pulse function with raised cosine shape in frequency domain so as to make the whole channel features of transmit filter, channel and receiving filter have raised cosine property, and to make the equivalent pulse response satisfy the criterion of Nyquist sampling points with no distortion by using adaptive channel equalization method. At transmitter the quasiª²orthogonal discrete information symbols sequence is transmitted over the channel above, and the orthogonal separation is realized according to the quasiª²orthogonal property of information symbols at receiver. QOTDM can decrease the peakª²toª²average power ratio with lowering bandwidth efficiency a little, and is more robust against multipath fading when the signalª²toª²noise ratio (SNR) is higher compared to the orthogonal frequency division multiplexing (OFDM). Simulation results indicate that when the bit error rate is 10-3 QOTDM is about 3 dB lower than the average bit SNR of OFDM by using orthogonal amplitude modulation in quasiª²static multipath fading channels. Keywords£ºtimeª²frequency duality; quasiª²orthogonal time division multiplexing; orthogonal frequency division multiplexing; bandwidth efficiency; peakª²toª²average power ratio |
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