Exact evaluation of capture effect under NCFSK demodulation

The capture effect can improve throughput of random multiple access protoco ls. An exact model for evaluating the capture effect is proposed for noncoh erent FSK demodulation (NCFSK) under a slow fading assumption. This model t akes into account the bit decision process of the NCFSK demodulator in the presence of both co-channel interference and noise. An approximate and simp lified model is also presented for comparison. Additionally, a Gaussian ass umption-based model is derived, which turns out to be too pessimistic for s low fading channels. The capture effect is investigated by means of the pro posed exact model in a low Earth orbit satellite channel. The result shows that a relatively large link margin can result in a large capture probabili ty, and consequently benefit slotted ALOHA protocols with a substantial thr oughput improvement.