Research On WLAN Handoff And Channel Assignment Based On Partially Overlapping Channels

With the rapid development of wireless technology,wireless network services are gradually becoming an indispensable service in people's daily life.Currently,wireless local area networks(WLANs)have been widely used.Due to the limited power of a single AP,the coverage of the service is limited.Multiple APs need to be deployed when covering a large area,and a handoff is required when the mobile node moves between two AP cells.The handoff process causes a certain delay,which brings challenges to delay-sensitive real-time multimedia applications.The performance of the handoff is directly related to the user's experience,and is a hot topic of current WLAN application technology.Wireless network intensiveness has made the limited spectrum resources more tense,so the use of partially overlapping channels is the key to improving spectral efficiency.For the handoff problem under partially overlapping channels,this paper analyzes the WLAN network topology and the mechanism of handoff,and then refers to several classic handoff algorithms.Then,the composition of the delay in the handoff process is analyzed.According to the characteristics of partially overlapping channels,this paper proposes a WLAN handoff protocol design based on partially overlapping channels.The physical layer design of partially overlapping channel transmission and the partial overlap channel handoff MAC design are elaborated.The subcarrier distribution is re-planned according to the characteristics of partially overlapping channels.The MAC mechanism of partially overlapping channel transmission is designed to coordinate communications during the handoff process.The triggering and workflow of the handoff is then explained.In order to effectively use spectrum resources,an adaptive cell splitting and partial overlapping channel allocation algorithm is proposed.In order to verify the handoff protocol proposed in this paper,an experimental model is established on the network protocol simulation platform NS-3.The algorithm is analyzed and the experimental results are compared with the results of the standard 802.11 built-in handoff algorithm and the neighbor graph handoff algorithm.The experimental results show that the proposed handoff algorithm reduces the handoff delay by more than 90% compared with 802.11 handoff,and reduces the handoff delay by about 50% compared with the typical neighbor graph algorithm.At the same time,it achieves a lower packet loss rate and meets the requirements of handoff delay for most real-time applications.