The Research And Implementation Of MAC Layer Based On IEEE 802.11

With the development of society and science, there are more and more kinds of technology that have been converted into product. To be a new kind of theory or business, wireless LAN is changing people life prominently. So it is very meaningful to choose it as a research object.The standard of IEEE802.11 is one of important point of wireless LAN research. As wellknown, its protocol about MAC layer is thought to solve the problem of"hidden terminal"which has troubled people for a long time, to an certain extent, it is better than other types of wireless LAN standard. The paper puts emphasis on the research of MAC layer of IEEE std.802.11 protocol, and then we think to carry it out. For that purpose, firstly, it is necessary to explain and study the basic notions and theories of IEEE std. 802.11 protocol, and later, a math model for Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is introduced to analyse system performance. It is shown that the larger station number that network has, the more sharply that system performance goes down. And that situation fits with practical experience. In order to raise system performance, decreasing probability of stations collision is a key point should be be taken into account. This paper proposes an improved backoff algorithm which adopts the method to defer the station reset action, and finally we can make the distribution of the chosen backoff window more evenly. Simulation result shows the new improvement performs significantly.Translating process flowgraph of MAC layer of IEEE std. 802.11 protocol to C codes is another research job of the paper. Since C language is a very mature programming language, using it for research is in favor of transplant and debug. The paper tries to progamme the whole model blocks of MAC layer of IEEE std. 802.11 protocol. Up to now, our job has completed the system framework of MAC layer in general. At the same time, we have chosenμC/OS -II as the implement platform. As a micro embedded system, it is in possession of many advantages such as simpleness,convenience,refinement and so on. Through it, we could make debugging for our model blocks by alternating messages and signals.