Effect of changing symbol rate on equalizer performance for band‐limited systems

In this work, the effect of changing symbol rate (or equivalently, symbol rate) on the equalizer performance for M‐ary PAM systems is investigated. We keep increasing the symbol rate (or equivalently, keep decreasing the symbol period) until a limit is reached. An effort is made to find this limit. In other words, we are investigating the possibility of increasing the symbol rate beyond the usual Nyquist rate. Since incessantly increasing the symbol rate will eventually produce channel spectrum null (almost null) which will render difficulties for equalization, decision‐feedback equalization combined with fractionally spaced sampling is used to overcome the difficulties. For a given channel bandwidth and a prescribed error probability, optimum symbol rates vs SNR are found so as to achieve maximum bit rates. Explanations are given for the resultant phenomena both analytically as well as by computer simulations. A theoretical channel model and a realistic twisted pair channel are used for demonstration. Important analytical expressions are given along with computer simulations to quantify performance results. Copyright © 2004 John Wiley & Sons, Ltd.