Study Of Cross-layer Design Of Multi-rate Wireless Networks

With the rapid development of wireless mobile communications, wireless mobile networks and devices have become more and more popular, as they can facilitate information access and communication at any time and any place. Wireless local area networks use wireless transmission mediums to form local area networks. For areas where wiring is difficult, they can provide communication capacities and facilitate installation, use and management.The IEEE 802.11 protocol is the standard protocol for wireless LAN MAC layers and physical layers. In the past, IEEE 802.11 only provided a transmission rate. In recent years, through the use of different modulation and coding methods, IEEE 802.11 has begun to provide a variety of transmission rates in physical layers. Considering that multi-rates help to improve network throughput and improve savings in energy consumption, researching multi-rate problems is of great importance. For instance, a major direction of research in multi-rate problems is how one can choose an appropriate rate adjustment algorithm in accordance to channel status. This paper combines thinking on network protocol stack cross-layer design—so-called cross layer design refers to breaking inherent independence in levels in network protocol hierarchical designs, strengthening inter-layer interaction and data collaboration, and optimizing the overall network design method. Through information exchange between the application layer and the MAC layer, a kind of cross-layer adaptive rate adjustment algorithm is designed, and overall network performance is enhanced through simulation verification.At the same time, this paper analyzes the original IEEE under multi-rate environment.In the 802.11DCF exponential backoff mechanism fairness issues such as low utilization rates in networks and throughput anomalies exist. Therefore, as new rate adaptive algorithms are designed, they should be made in line with original channel access protocols in order to fully optimize network performance. In response to this problem, this paper analyzes the fairness of traditional channel access protocols under the multi-rate environment, proposing an access channel method based on minimum contention window adjustment, effectively improving the fairness of channel access under the multi-rate environment.The main content and contributions of this research are as follows:(1) An analysis of existing rate adaptive algorithms that combines different thinking on network cross-layer design, creating a kind of rate adaptive program that supports cross layer information exchanges. This program combines time restrictions on upper and lower application requirements and, through the matching and parameter transmission of MAC layers and application layers, effectively improves network performance.(2) Regarding the fairness issue in traditional access protocols in the multi-rate environment, this paper combines multi-rate network features, analyzes transfer rates, data size, error rates, and other factors that effect network throughput. It achieves channel access fairness under the multi-rate environment by dynamically adjusting the minimum contention window(3) It builds a simulation environment and, through simulation experiments, verifies the effectiveness of the program proposed in this paper.