1,721,061 research outputs found
On the Use of Oversampling in Adaptive Receivers for Frequency-Selective Rayleigh Fading Channels
No full textIn this work, we investigate Maximum Likelihood Sequence Estimation (MLSE) of data sequences transmitted over time-varying frequency-selective Rayleigh fading channels and consider adaptive receivers which realize joint data estimation and channel tracking utilizing Per-Survivor Processing (PSP) techniques. In order to obtain a sufficient statistics for data detection, the received signal is oversampled with respect to the symbol rate. Accordingly, a time-discrete channel model with fractional spacing, with respect to the symbol interval, is assumed and an algorithm which performs fractionally-spaced
PSP-based channel tracking is analyzed. We show that receivers which employ this algorithm outperform traditional adaptive receivers based on one sample per symbol interval. Two samples per symbol interval are shown to be sufficient to attain the optimal performance for these receivers
A Recursive Formulation for Quadratic Detection on Rayleigh Fading Channels
No full textWe address the problem of optimal detection of a random signal transmitted over a time-varying frequency-selective correlated Rayleigh fading channel. We present a general recursive solution which may be operated at full complexity to provide optimal detection or at reduced complexity, using per-survivor processing (PSP) techniques, to yield a suboptimal receiver
Incremental adaptive equalizers using ternary +1, 0, -1 tap coefficients and/or delta modulation input encoding
No full textOptimal versus PSP-based sequence estimation for Rayleigh fading channels
No full textWe investigate maximum likelihood sequence estimation (MLSE) of data sequences transmitted over time-varying frequency-selective Rayleigh fading channels. We present the optimal receiver designed to exploit perfect channel state information (CSI) at the beginning of the data sequence and the optimal receiver which does not use this information. For any given data sequence length a performance range for optimal detection can be identified: this range is lower bounded by the optimal receiver with perfect CSI and upper bounded by that without CSI. For increasing data sequence lengths, this range becomes narrower, since the performance of the two optimal receivers tends to converge to a common level. As a consequence, the performance of the optimal detector can be inferred and compared to that of practical receivers based on per-survivor processing (PSP)
Efficient trellis search techniques for adaptive MLSE on fast Rayleigh fading channels
No full textWe analyze trellis search algorithms for joint sequence estimation and channel tracking, assuming rapidly varying frequency-selective Rayleigh fading. The Generalized Viterbi Algorithm (GVA) and the M-Algorithm (MA) are considered for approximately searching the maximum likelihood path in the trellis diagram and compared with the Viterbi Algorithm (VA). All algorithms perform channel tracking utilizing Per-Survivor Processing (PSP) techniques by associating a channel estimate
to each hypothetical trellis path, according to the Least Mean Square (LMS) or Recursive Least Square (RLS) algorithm.
To reproduce a typical mobile digital communication system,
a Time-Division Multiple Access (TDMA) data frame
is assumed, where each user transmits a block of information
symbols with known preamble and tail. For Doppler bands up to one hundredth the symbol frequency and a three path delay profile, the MA is shown to exhibit a slightly better performance than the GVA for an equal number of survivors, and outperform the VA
An efficient time-discrete symbol-spaced simulation model for mobile radio channels
No full textWe propose a fully parametric, time-discrete, symbol-spaced simulation model of frequency-selective mobile radio channels. The model encapsulates transmission and receiver filters and a physical channel accounting for both Rayleigh and Rice fading. The simulator allows one to accurately trade between complexity and quality of representation of the propagation channel, making use of a digital filter of variable order to implement the Doppler spectrum of the fading processes. Numerical results assessing the performance of the model in terms of the simulation time and the power spectrum of the fading processes are provided. A communication system with an adaptive receiver is employed to test the reliability of the propagation model. Increasing the degree of accuracy in the approximation of the Doppler spectrum, the performance of the considered receiver, expressed in terms of symbol error rate, rapidly converges to a specific function of the signal to noise ratio
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