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Data Transmission and Signalling
Published in Michel Daoud Yacoub, Foundations of Mobile Radio Engineering, 2019
A simplified model of a digital system using adaptive equalizer is sketched in Figure 6.4. The transmitted digital sequence x(n) arrives at the receiver as the sequence xn(n), a distorted form of x(n). The aim of the adaptive equalizer is to restore the signal as close as possible to its original form. An adaptive equalizer is a transversal filter having as an output the weighted sum of the input xn(n) delayed by a set of delaying elements (Δ).† The estimate of x(n) is x’(n), obtained by conveniently sampling the equalizer’s output x(n). The sampling is carried out by the decision device block. After a training period the estimate x′(n) closely approximates x(n) and the adaptive equalizer starts its “tracking mode”. In this mode the difference x′(n) − x(n) (the error) is used for continuous adjustment of the filter coefficients hi. If the variations of the received signal are slow enough, these perturbations can be tracked and corrected.
Channel Equalization
Published in Jerry D. Gibson, Mobile Communications Handbook, 2017
Initially, the adaptive equalizer is trained by the transmission of a known pseudo-random sequence {Im} over the channel. At the demodulator, the equalizer employs the known sequence to adjust its coefficients. Upon initial adjustment, the adaptive equalizer switches from a training mode to a decision-directed mode, in which case the decisions at the output of the detector are sufficiently reliable so that the error signal is formed by computing the difference between the detector output and the equalizer output, that is, ek=I˜k−zk
Channel Equalization
Published in Jerry D. Gibson, The Communications Handbook, 2018
Initially, the adaptive equalizer is trained by the transmission of a known pseudorandom sequence {!„} over the channel. At the demodulator, the equalizer employs the known sequence to adjust its coefficients. Upon initial adjustment, the adaptive equalizer switches from a training mode to a decision-directed mode,
FPGA Implementation of an Adaptive Equalizer with TLBO and PSO Variant
Published in IETE Journal of Research, 2023
Shital Ganorkar, Shekhar Sharma, Anjana Jain
ISI can also be a major obstacle for high-speed data transmission and bandwidth-limited channels [2] since practically every channel is noisy and non-ideal it is a challenge in the wireless communication system to transfer data for high system applications [3]. To overcome this problem the best solution is the addition of an adaptive equalizer in series with a channel. An Adaptive equalizer improves the Bit Error Rate (BER) and also removes other impairments which distort communication like noise and cross-talk. An adaptive equalizer is a form of a transversal filter whose response can be varied by adjusting the weight of the filter to equalize the effects of all the impairments of the channel. Working of an Equalizer is just the same as a filter, it first initializes weights, then filters the received data, and finally adapts the suitable coefficients as per changes in the environment with a selected optimization technique [4].