Abstract
This paper proposes a wavelet based receiver structure for frequency-flat time-varying Rayleigh channels, consisting of a receiver front-end followed by a Maximum A-Posteriori (MAP) detector. Discretization of the received continuous time signal using filter banks is an essential stage in the front-end part, where the Fast Haar Transform (FHT) is used to reduce complexity. Analysis of our receiver over slow-fading channels shows that it is optimal for certain modulation schemes. By comparison with literature, it is shown that over such channels our receiver can achieve optimal performance for Time-Orthogonal modulation. Computed and Monte-Carlo simulated performance results over fast time-varying Rayleigh fading channels show that with Minimum Shift Keying (MSK), our receiver using four basis functions (filters) lowers the error floor by more than one order of magnitude with respect to other techniques of comparable complexity. Orthogonal Frequency Shift Keying (FSK) can achieve the same performance as Time-Orthogonal modulation for the slow-fading case, but suffers some degradation over fast-fading channels where it exhibits an error floor. Compared to MSK, however, Orthogonal FSK provides better performance.
Highlights
Fueled by the increased interest in mobile communication for fast moving platforms [1] [2], signal detection over fast-fading channels has become an important research area in the last decade [3] [4]
This paper proposes a wavelet based receiver structure for frequency-flat time-varying Rayleigh channels, consisting of a receiver front-end followed by a Maximum A-Posteriori (MAP) detector
FHT stands for Fast Haar Transform [17], and the operator Vec (⋅) yields a column vector obtained by concatenating the columns of a matrix
Summary
Fueled by the increased interest in mobile communication for fast moving platforms [1] [2], signal detection over fast-fading channels has become an important research area in the last decade [3] [4]. In [10], the authors show that processing more than one sample per symbol ensures robust performance in a fast-fading environment when Nyquist pulse shaping is used, at the expense of increased system complexity compared to traditional detection techniques In line with such concept a receiver structure for a fading channel applying multisampling is derived in [11]. By a moderate increase in complexity compared to a matched filter receiver, the performance is close to optimal except at very high Signal-to-Noise Ratio (SNR) Another method of designing front-end filters is presented in [14], that employs the Karhunen-Loeve (KL) expansion [15] to approximate the autocorrelation function of the fading process by a finite dimensional separable kernel. System Model and Discrete Representation of Signals over Time-Varying Rayleigh Channels
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