# Context-Aware Enhanced Application-Specific Handover in 5G V2X Networks
## 3 Connection-Aware Policy Mechanism (CAP)
### Small-Cell Performance Index (PI) Measurement Using TOPSIS  
The TOPSIS criterion-weighted result is deemed to be more accurate compared to other MCDMs, demonstrating a high level of accuracy [27] due to the rationality of human decision-making [28]. This study offers a context-aware method as an enhanced version of our previous study [29]. The MCDM-based mechanism aims to select the best target SC to maximize HO success, minimize disruptions, and ensure optimum user experience using a set of heterogeneous criteria that are relevant to a UE connection context. Each criterion is classified based on whether it degrades or improves connection quality. The maximization of criteria such as RSSI, SINR, and the data rate is aimed at improving connection capacity or strength. Minimization focuses on the reduction in latency and loss (BER, delay, packet loss rate, and load). Values are normalized [0,1] for the benefit of the criteria. Higher values are beneficial for RSSI and SINR, while inversed values are beneficial for BER and delay, for example. This ensures that all scores align with a maximization objective. Once the values are normalized, they are aggregated into the PI value through a weighted sum model. This decision-based framework integrates goal setting, criterion classification, normalization, and scalar aggregation to ensure that the MCDM process is clear and robust enough to indicate that the mechanism is not based on weights alone. Dynamic-weighted network connection quality metrics are used to calculate PI for every SC using the TOPSIS method. To provide a clear rating of SCs from best to worst, TOPSIS finds the SC that is closest to the ideal solution and farthest from the negative ideal solution as per the following steps:  
* Define the Network Connection Quality Parameters  
Let X be the decision matrix where \(X_{ij}\) is the value of the parameter \(P_{j}\) for SC, and the network parameters are denoted as follows: P\({}_{1}\): RSSI, P\({}_{2}\): SINR, P\({}_{3}\): BER, P\({}_{4}\): data transmission rate, P\({}_{5}\): delay, and P\({}_{6}\): packet loss. * The normalization of weights is calculated as follows:  
\[X^{\prime}_{ij}=\left\{ \begin{array}{ll}\frac{X_{ij}-min(X_{j})}{max(X_{j}) -min(X_{i})}&\text{if $j$ is to be maximized}\\ \frac{max(X_{j})-X_{ij}}{max(X_{j})-min(X_{i})}&\text{if $j$ is to be minimized} \end{array} \right. \tag{1}\]
* Then, the dynamically adjusted weights are determined:  
\[\text{Let }W_{ijk}=\alpha_{ij}.\beta_{ik} \tag{2}\]  
Here, \(\alpha_{\text{ij}}\) is the base weight for parameter \(P_{j}\) in network type \(i\), and \(\beta_{ik}\) is the adjustment factor for parameter \(P_{j}\) based on the connection context k.  
* Then, the decision matrix is formulated:\[\mathrm{X}= \begin{bmatrix}x_{11}&x_{12}&x_{13}&x_{14}&x_{15}&x_{16}\\ x_{21}&x_{22}&x_{23}&x_{24}&x_{25}&x_{26}\\ x_{31}&x_{32}&x_{33}&x_{34}&x_{35}&x_{36}\\ x_{41}&x_{42}&x_{43}&x_{44}&x_{45}&x_{46}\\ \cdots&\cdots&\cdots&\cdots&\cdots&\cdots\\ x_{n1}&x_{n2}&x_{n3}&x_{n4}&x_{n5}&x_{n6}\end{bmatrix} \]
* The Ranking and Stay Time Assignment (STA) is as follows:  
After evaluating the quality of the network using TOPSIS, the ranked list of SCs is filtered by determining the top n%, which lowers the density and ensures that only the highest-performing cells are selected. This step is essential for effectively managing network resources and preventing congestion. _Topk_ represents the function used to obtain the top k elements from a sorted list. For example, the equation to obtain the top 20% of SCs is as follows:  
\[\mathrm{Top}_{[0.2\times n]}(\mathrm{Cranked}) \tag{3}\]  
where \(C_{rmk}\) is the list of PI values sorted in descending order. A stay time (ST) value is assigned to the selected SCs, which represents the ideal amount of time needed to maintain the connection with the selected SC before allowing a handover to a new SC. As the UE moves and conditions change, this ST allotment aids in preserving a strong, reliable connection.