Comparison between permutation FSK and 4×4-FSK modulations in NPCS system

In order to achieve a high throughput in the presence of a large differential delay in simulcast overlap areas, a multicarrier modulation technique (MCM) is proposed for the Narrowband Personal Communication Service (NPCS) operating in the 940 MHz band. Two major variants are considered: (8,4) permutation FSK (PFSK), and 4×4-FSK. The two variants are compared on the basis of bit error rate (BER) in Gaussian noise and in fading environments. The comparisons are both theoretical and experimental. It is found that 4×4-FSK performs better for low SNR, while (8,4) PFSK improves faster with increase in the SNR. In a fading environment, their performance is nearly the same. It is suggested that the integral of the BER over the SNR range, in a Gaussian channel, can be used as a figure of merit for the modulation technique in a fading environment