# User QoS-Based Optimized Handover Algorithm for Wireless Networks
## 1 Introduction  
In recent years, technologies such as IEEE 802.11 wireless networks and cellular networks (such as 4G) have matured [1], and the application services using these technologies have also gradually increased. At the beginning of the development of wireless network technologies, the main focus of research and development was achieving high quality of service (QoS) and high connection stabilities between access points (APs) and user equipment (UE), and also achieving high packet delivery ratio (PDR) [2]. As these wireless network technologies mature, the stability of network connections and the transmission rate of data exchange increase, and more applications now use wireless networks as a medium for data exchange.  
When using IEEE 802.11 wireless networks for transmission with high throughput requirements, once the UE moves to the boundary of the AP's transmission range, the AP that originally provided the network service should hand over its job to a nearby AP, which can provide higher throughput to the UE; otherwise, the UE will keep gaining low throughput, which will affect the QoS of the UE. However, on the contrary, if the UE does not have high throughput requirements, and the handover decision is still prioritized to providing high-throughput network service between the AP and the UE, this may raise the chance of unnecessary handovers. Handover refers to the process of an AP handinover its job of network provision to another AP. It mainly occurs when the original serving AP can no longer provide a satisfactory QoS for the UE, and handing over the right of network service provision is required. If the handover judgment is not designed based on the users' environment of application, the handover decision will be inaccurate and unable to ensure that the handover occurs at the correct time. When the UE wanders between multiple nearby APs, the signal strengths of these APs are similar, so if there is no good handover design, the handover between APs will become frequent, resulting in the occurrence of the ping-pong effect. Because of this phenomenon, we found that when designing the handover algorithm and its threshold, a more delicate design should be adopted to effectively prevent the ping-pong effect and further improve the QoS of the network.  
In this paper, we propose the optimal handover algorithm (OHA) and the optimal handover algorithm with QoS requirements (OHAQR) to reduce the number of handover procedure triggers and ensure the quality of service in the network. In the OHA, to consider whether the signal quality is good or bad, different hysteresis margins (HMs) are used to solve the problem of frequent handover procedures. Different HMs are designed according to different signal qualities to help reduce unnecessary handover procedures being triggered. In the OHAQR, the handover score Q is included in the OHA algorithm to start the handover procedure earlier when the current network performance does not meet the QoS requirements. The handover score Q is a measurement indicator based on the QoS requirements, which includes throughput and packet loss rate (PLR) [3].  
The rest of this paper is organized as follows: In Section 2, we detail and analyze the related work proposed by other authors, organize the pros and cons of their proposed methods, and further clarify the goal of our research; in Section 3, we clearly explain our proposed handover algorithm, which is optimized based on users' QoS requirements; in Section 4, we present the experimental results simulated in different densities of topologies and compare the network performances of the proposed handover algorithm with the methods proposed by other authors, through the Mininet-WiFi simulator; and in the last section, we conclude this paper based on our proposed methods and summarize their performance breakthroughs, while also briefly outlining our future research.