Signal Design And Performance Analysis For Joint Time-frequency Communication System In Transformed Domain

The Weighted-type Fractional Fourier Transform (WFRFT) is a novelmathematical tool for time-frequency analysis in the recent years. The signal in theWFRFT domain is made up with two main categories: the time-domain informationand the frequency-domain information. And the WFRFT implementation comprisesa co-modulation process of single-carrier (SC) system and multi-carrier (MC)system. Hence by applying WFRFT into the communication field we build a noveljoint time-frequency communication system which is also called a hybrid carrier(HC) system. The main feature of the HC system is that it can not only provide thecompatibility with SC and MC, but also achieve a smooth and seamless transitionbetween the two. However as a WFRFT procedure contains both SC and MCmodulation, HC system may inherit some undesired properties. In this paper wefocus on the researches to overcome these shortcomings.At first, we summarized the basis theory of WFRFT. And a novel joint time-frequency communication system based on WFRFT is introduced in the paper. Theframeworks and the implementation of the proposed system are discussed, and theproperties of the HC system signals are also presented in detail.At the second, we make an analysis on the influence to the HC system causedby frequency offset in this paper. In this part the inter-carrier interference (ICI)mechanism of a HC system caused by frequency offset is analyzed. The polynomialcancellation coding (PCC) method is adopted to improve the HC system. In whicheach data symbol is modulated onto a group of adjacent subcarriers with a group ofweighting coefficient at the transmitter side and demodulated by linearly combiningthe received signals with at the receiver side. Through a detailed analysis andsimulation, it is shown that, the HC system with the PCC method gives a better biterror rate (BER) and carrier to interference ratio (CIR) performance.At last, we make a discussion on the peak-to-average power ratio (PAPR)issues of the HC system. In this part a brief introduction to the PAPR of HC systemis proposed. A compare of PAPR performance between HC and MC is made in thispaper. And the selected mapping (SLM) method is applied in a HC system toimprove its PAPR performance. And then two novel methods based on SLM method are proposed according to the linear property of WFRFT, and the PAPRperformance of these two proposed methods are analyzed in detail. Then the crossentropy method used for combinatorial optimization is combined with SLM, thePAPR performance of this method is also analyzed in this part. According to thesimulation, we can find that by applying these methods the PAPR performance ofthe HC system can get huge improvement...