Wi-Fi Network MAC Cross-layer Protocol Optimization

With the continuous development of the wireless communication technology in recent years, Wi-Fi has gradually been known by the masses and integrated into daily lives of people. Wi-Fi has been popularized at present. Wi-Fi appears to enable people to realize the wireless layout and Internet access whenever and wherever possible. With its fast network transmission speed, it has gradually found favor among the masses. We can say that Wi-Fi has become the first choice for people to realize wireless Internet access. Recently, the State Council has formulated and promulgated a strategy and implementation program for a full access of the "broadband era’.Wi-Fi has virtually become an absolute leader in the development of the telecommunication industry. The worldwide Wireless LAN sales have flourished, and showed an explosive growth, especially in recent years. However, compared with wired networks, Wi-Fi, as one of important technologies in wireless LAN communication, Wi-Fi needs further improvement in its performance, transmission distance, network transmission efficiency and other aspects. Besides environmental factors, MAC protocols and routing protocol design constitute another major cause of the failure to achieve the desired performance of Wi-Fi. Therefore, in order to further improve the performance of Wi-Fi, it is of great significance to study and improve MAC protocols of Wi-Fi.Ever since 1997 when the first Wi-Fi standard was issued,researchers have been devoting to improvement of the performance of Wi-Fi. The re-defined Wi-Fi standards have also been greatly improved in the performance. Meanwhile, scholars have also used various mathematical models to analyze MAC protocols. Cross-layer design emerged at this historical moment, and has developed into a new direction of research on network performance.In this paper, the author follows the idea of cross-layer design to study the performance of Wi-Fi. This paper falls into following parts:introduction, theoretical basis, model building and extension, cross-layer scheme selection and building and simulation result analysis. In this paper, firstly, the composition of wireless local area network is discussed to introduce the concept of Wi-Fi to focus on exploring the significance of Wi-Fi. Meanwhile, based on the development of IEEE802.11 standards, due to different system performances, various MAC research hotspots and directions are introduced. The throughput, collision probability, time delays and cross-layer design has become hot topics for scholars on a global scale. Secondly, under the research background of MAC functions, the MAC protocol architecture and routing protocols, PCF and DCF mechanisms are adopted to determine the collision, competition and time delay of data in the information channel transmission process, and compare three categories of routing protocols including table-driven protocols (DSDV, WRP, and OLSR), on-demand routing protocols (DSR, ABR, and AODV) and hybrid routing protocols. These protocols are compared to analyze deficiencies of the performance of existing routing protocols. Thirdly, the DCF mechanism is taken as a basis to establish MAC mathematical models mainly including saturated and unsaturated Markov chain models. The two models are used to build calculation methods of relevant reference quantities, and the idea of cross-layer design and research achievements of cross-layer design are introduced to form the guiding idea of cross-layer design in this paper. The saturated Markov chain is used to extend the model to extract relevant parameters (collision probability) as cross-layer analysis conditions. The routing optimization mechanism AODVMLP is combined to develop the cross-layer design scheme. This design scheme is followed to calculate the collision probability, update the routing criteria and modify the route list, thereby completing cross-layer design and deriving calculation methods of relevant reference quantities (throughput, delay, etc.).Lastly, the NS-2 simulation software is used to make analogue simulation of the cross-layer design scheme. Analysis results of throughput, time delay and other reference quantities show that compared with the original design, this cross-layer design scheme shows a significant improvement in the MAC performance, which validates the feasibility of cross-layer design.