| How to design and optimize link layer protocols is one of the research hotspots in Mobile Ad Hoc networks. Firstly the link layer based on Scheduling strategies generally adopted TDMA (Time Division Media Access) protocol. One effective method of improving TDMA protocol is to adopt STDMA (Spatial TDMA) mechanism. So lastly combining the ascendants both of them, STDMA MAC protocol, linking scheduling and Ad Hoc networking method are proposed.This dissertation starts with the basic conceptions and characteristics of ultrashort Selforganized Network and introduces the current main problems and application foreground of wireless Selforganized Network. Later some advantages of the directional antenna as many aspects are described which including Spatial division multiple access, the antenna gain, anti-interference etc. After that the possibility about the directional antenna used for the ad hoc networks is analyzed. Secondly Ad Hoc network multiple access protocols including STDMA protocol are studied, at the same time comparing with the protocol differences and network performance between isotropic and directional antenna in particular environment. The MAC protocol proposed in the thesis includes layer interface, link assignment strategies, slot structure and packet structure etc. Updating three information tables periodically achieve channel access and mapping. At last the results show that the average delay decreased when using directional antenna instead of isotropic antenna arrays. Using the antenna array also affects the capacity gain and network throughput. Every node not only can access channel fairly without interfere using STDMA, but also increase the netowork connectivity.Network node model and directional antenna model are designed based on soft tool OPNET and the emulation of special network models is realized. According to the results, STDMA protocol ensures that connectivities per node achieve 4.8 and time of topology stabilization is less than 8 Epoches. Comparing with CSMA/CA, up to 60% throught improvement is achieved and delay controls within 250ms by utilizing SDTMA protocol with directional anntena. This protocol not only achieves requests of design, but also guarantees efficiency and stabilization. |
