Filter Bank Design for DFT Based Transmultiplexers

This paper investigates the application of filter bank design techniques on the DFT based transmultiplexers to ameliorate the effects of in-band aliasing and consequently improve the performance of the system. With this approach, one is allowed flexibility in the design of the synthesis and analysis filters. Hence, a suitable prototype filter can be selected and specific values assigned to its parameters, namely the cut-off frequency, main lobe width and side lobe amplitudes so as to construct an ideal filter for optimal recovery. Investigation results depict that increasing the cut-off frequency of the prototype filter by a small increment delta, enhances system performance through the widening of the stopband tolerance region which reduces the effect of aliasing. Simulations also show that using a Kaiser prototype filter with a wide main lobe and low side lobe amplitudes generates the most favorable results. Moreover, it was observed that the performance of the transmultiplexer can be improved by increasing the number of sub-carriers and oversampling factor. The evaluation of the transmultiplexer structure for this paper was assessed in terms of its bit error rate (BER) performance