# User QoS-Based Optimized Handover Algorithm for Wireless Networks
## 3 User QoS-Based Optimized Handover Algorithm
### Optimized Handover Algorithm
First, when the signal strength of the second-best AP (\(RSS^{2 nd-best}\)) is greater than the handover threshold of nearby AP with the second-best signal strength (\(T^{2 nd-best}\)) minus the handover HM of nearby AP with the second-best signal strength (\(HM^{2 nd-best}\)), it means that the nearby AP with the second-best signal strength can provide good enough signal quality. However, the HM used in this article is the upper/lower limit range of the tolerable signal strength variation based on a signal strength RSSI value, so the \"subtract with HM\" method is not a direct subtraction of the two signal strength levels. Second, when the UE moves towards the AP with the second-best service quality nearby, if the conditions for the overstep AP handover have not been established, which means that there is no AP that meets the second-best quality and can be handed over to, then the following more detailed and accurate handover judgment is performed to avoid unnecessary handovers. This method divides the signal strength of the currently connected AP into \"good signal quality\" and \"bad signal quality\" to optimize the performance of the handover algorithm. When the current signal connection quality is within the good signal conditions, the following four conditions need to be satisfied, and the connection of the UE will be handed over to the AP with the best signal quality nearby. 1. The signal strength quality of the AP near the UE is the best (\(RSSI^{\text{Marr}}\)) and better than the sum of the signal strength of the currently connected AP (\(RSSI^{\text{C}}\)) and the HM with a good signal quality (\(HM^{\text{Good}}\)). Since the signal strength quality of neighboring APs is excellent, the handover procedure can be performed (i.e., \(RSSI^{\text{Marr}}\geq RSSI^{\text{C}}+HM^{\text{Good}}\)). 2. \"The minimum signal quality threshold for should handover\" (\(T^{5-HO}\)) is better than the sum of the signal strength of the currently connected AP (\(RSSI^{\text{C}}\)) and \"the minimum signal quality HM for should handover\" (\(HM^{5-HO}\)). The handover process is  
Figure 2: Optimized handover algorithm. (**a**) The overstep AP handover (taking AP1 and AP2 as an example); (**b**) the non-overstep AP handover (taking AP1, AP2, and AP3 as an example). not performed until the signal strength quality of the currently connected AP is in this condition, which can effectively reduce the occurrence of the ping-pong effect (i.e., \(T^{S\_HO}\geq RSSI^{C}+HM^{S\_HO}\)). 3. The signal strength quality of the AP near the UE is the best (\(RSSI^{Max}\)) and better than the sum of the signal strength of the second-best AP (\(RSSI^{2 nd\_best}\)) and the HM with the second-best signal strength in the good signal interval (\(HM^{2 nd\_good}\)). This means that for the UE, the quality of service of the nearby AP with the best signal strength is much better than the service quality of the second-best nearby AP (i.e., \(RSSI^{Max}\geq RSSI^{2 nd\_best}+HM^{2 nd\_good}\)). 4. When selecting the best nearby AP for handover, the AP with the largest signal increment will be selected as the best handover AP; that is, the UE keeps moving to it (i.e., UE is moving toward \(RSSI^{Max}\) AP). If the current signal connection quality is in the bad signal condition range (as shown in Figure 2b, and lines 9 to 13 of Algorithm 1), the handover procedure will be triggered when the following five conditions are met. 1. The signal strength quality of the AP near the UE is the best (\(RSSI^{Max}\)) and better than the sum of the signal strength of the currently connected AP (\(RSSI^{C}\)) and the HM with a bad signal interval (\(HM^{Bad}\)). Since the signal strength quality of neighboring APs is excellent, the handover procedure can be performed (i.e., \(RSSI^{Max}\geq RSSI^{C}+HM^{Bad}\)). 2. The minimum signal quality threshold for handover (\(T^{S\_HO}\)) is better than the sum of the signal strength of the currently connected AP (\(RSSI^{C}\)) and \"the minimum signal quality HM for should handover\" (\(HM^{S\_HO}\)).