Research On The Slotted ALOHA System Based On Spread Spectrum Technology

The ALOHA access protocol is used in communication networks where a large of users are competing to the access the same channel. The basic idea behind an ALOHA system is that users are allowed to send data any time they wish. The ALOHA system has many merits such as simple structure and application. On the other hand, it also has some disadvantages that the efficiency of channel is low…etc. This paper presents the slotted ALOHA system based on spread spectrum technology and two capture models applying to the system. The purpose of the research on them is to enlarge the throughput and the efficiency of channel. The research on them also helps the system to be applied widely.This paper imports spread spectrum technology to the conventional slotted ALOHA system. The new system only uses a unique spread spectrum code other than DS/SS-CDMA and therefore it is efficient and simple. The new system utilizes the respective advantages of both conventional systems. The delay capture effect is an inherent property of the new system. Previous works on delay capture are usually only on single capture, or using discrete time model. In this project, two continuous time multiple capture models are presented and multiple delay captures are considered. They breakthrough the conventional limit of single capture in theory and enhance the system capability. The general-M capture model presented by the paper is closer to the practical situation but approximation has to be made in theoretical analysis. The errors resulted in using this model are discussed and the accuracy of this model is verified through simulations. The first-M model is accurate but it results in under-utilizing the receiver. During the research on both models, I utilize Markov model to analyze the system performance and it is an important measure. I also use MATLAB to simulate and draw pictures in order to analyze the parameters and performance of the system directly. From the study of the dissertation, we can conclude that the slotted ALOHA system based on spread spectrum technology has better system capability and practical value than the conventional ALOHA system. Furthermore, we also conclude that both capture models based on the system that this paper presents are effective and credible.