| A general and broad new class, ART, consisting of adaptive hybrid multiple access protocols applicable to communication networks sharing a single transmission medium and which behave like A loha-type, R eservation and T DMA basic protocols at low, medium and high throughput respectively, is proposed. Each hybrid protocol in this class is a combination of one protocol, possibly individually adaptive or improved version, from each of these three basic classes of protocols. Specifically, for satellite communication networks, a sub-class of ART protocols called Adaptive Satellite Hybrid Access (ASHA){dollar}sp+{dollar} is proposed.; Two ASHA protocols named ASHA1 and ASHA2 that combine the features of S-ALOHA, TDMA-Reservation and TDMA protocols by using a proposed generalized design technique, are described in detail and their analytical models are formulated. The ASHA protocols are analyzed using Equilibrium Point Analysis technique and then their analytical results are presented.; A fairly sophisticated and new simulator, modeled basically as a 3-state finite state machine, to simulate the ASHA protocols is designed, described and implemented. A new phenomenon called "protocol oscillations" is observed, in which a hybrid protocol oscillates back and forth between its two adjacent states without accomplishing much, and becomes literally unstable. Traffic measures and threshold values to remedy this problem are discussed.; As a by-product of simulator validation, it is found that SRUC protocol, previously thought to be stable at all traffic levels, also suffers from this problem. In addition, some previous simulation results of SRUC protocol are felt not to be correct, and its simulation results that we believe to be correct instead, are given.; Detailed simulation results of ASHA protocols are presented and also compared with their analytical results. These results provide a large amount of practical and valuable insight, heretofore unknown, into the workings of adaptive hybrid protocols in general and of ASHA protocols in particular. Moreover, these results show that ASHA protocols provide better delay versus throughput performance over the entire range of throughput compared to any of their individual constituent protocols, and extend the channel capacity to unity. ftn{dollar}sp+{dollar}As an aside, ASHA means "hope" in Hindi language. |
