Applications Of Overlapped Multiplexing Principle In Telecommunications

The principle of overlapped multiplexing is the essential phenomenology of communication system. Not only high spectral efficiency can be obtained by using overlapped multiplexing, but also superior performance compared with Nyquist system. Overlapped Time Division Multiplexing is the direct applications of overlapped multiplexing principle. By the shift data symbol weighted overlapped version, there appears a novel coding scheme with high spectral efficiency, where the "inter-symbol interference" is introduced artificially. Theoretical and practical research of OvTDM is the first topic in this thesis.The fundamental introduction of OVTDM, include the spectral efficiency of OvTDM, power spectrum density of OvTDM, channel capacity of OvTDM and error probability of OvTDM is presented in Chapter Ⅲ. It shows that the overlapping of adjacent symbol does not expand the bandwidth, and there is no excess bandwidth, which is introduced in Nyquist system, in OvTDM system. OvTDM essentially is a parallel transmission system, so it can improve the spectral efficiency linear compare with Nyquist system. The transmission level of OvTDM increase with the spectral efficiency linearly, however, the constellation point of orthogonal modulation is exponentially. So the Euclidean distance between codes nodes of OvTDM can be increased at most. Surely relative higher noise immunity can be reached. And OvTDM has lower PAPR because of fewer number of transmission level. The analyze of capacity of OvTDM shows that by waveform overlapping OvTDM can achieve higher capacity than Nyquist system. And OvTDM can achieve the capacity of waveform channel. So it is a real sense of waveform encoding schemeThe error probability of OvTDM employing a rectangle multiplexing waveform is derived by using the analyzing of ISI channel. OvTDM has two advantages compared with the quadrature modulation. The first one is that OvTDM has higher coding gain. And the second one is that OvTDM has the larger distance between the constellation points compared with QAM or PSK modulation with the same spectral efficiency.In order to improve the performance of OvTDM in the lower spectral efficiency region. The concatenation OvTDM and its iterative detection is studied in Chapter Ⅳ. Because OvTDM can be equivalent to a convolutional waveform scheme, OvTDM has several concatenation structures such as parallel concatenation OvTDM, serial concatenation OvTDM and hybrid concatenation OvTDM. The concatenation between two OvTDM encoder or between OvTDM encoder and channel encoder can increase the equivalent encoding constraint length. So it can significantly improve the performance of OvTDM.Multi-carrier OvTDM is a broadband transmission scheme of OvTDM. If we directly apply OvTDM encode to OFDM system. Not only ISI, but also inter-carrier interference is introduced in OvTDM-OFDM system. The orthogonality of subcarrier will be damaged, which will add the detection complexity. A novel spinning orthogonal complementary code pari is constructed, which is used to realize the transmission of multi-carrier OvTDM. The various signal can be decoded independently, and the proposed scheme does not increase the decoding complexity.The multi-cell and multi-user OvTDM scheme is researched in Chapter VI. A four color networking technology is employed in the cell edge to eliminate the adjacent cells interference. Based on the convolution matrix model of multi-user OvTDM system. A parallel iterative multi-user interference cancellation detection, whose complexity is just linear increased with the number of simultaneous users, is purposed to separate multi-user signal. The algorithm has less iteration, and can achieve rapid convergence.