Exact evaluation of capture effect under NCFSK demodulation

The capture effect can improve the throughput of random multiple access protocols. An exact model for evaluating the capture effect is proposed for noncoherent FSK demodulation (NCFSK) under a slow fading assumption. This model takes into account the bit decision process of the NCFSK demodulator in the presence of both cochannel interference and noise. An approximate and simplified model is also presented for comparison. Additionally, a Gaussian assumption-based model is derived, which turns out to be too pessimistic for slow fading channels. The capture effect is investigated by means of the proposed exact model in a low Earth orbit satellite channel. The result shows that a relatively large link margin can result in a large capture probability, and consequently benefit slotted ALOHA protocols with a substantial throughput improvement