In this paper, it is proposed to employ random multiple signal levels for channel access in packet broadcast networks. We pre-sent priority-free random access protocols that possess the advantage of capture effect. The presented schemes are applied to the slotted ALOHA, and the performance is analyzed based on a conservative capture model. Closed-form expressions for the system throughput are derived for a general two-signal level system and a general m-signal-level system. It is shown that the maximum throughput for the two-level system increases from 0.47 to 0.52 as the separation between the two levels increases. For the m-level system, the maximum throughput increases from 0.52 to 0.66 as m increases from three to infinity. Then a rotary-priority sure-capture random access scheme is presented, which can achieve perfect channel utilization. The time-delay characteristic and the throughput-delay tradeoff are analyzed for the simplest two-level system for which the higher level is double the lower level. The results compare favorably to those of the conventional slotted Aloha system which employs a single signal level for packet trans-mission. A number of open problems are addressed.
ASJC Scopus subject areas
- Computer Networks and Communications
- Electrical and Electronic Engineering