# Velocity-Aware Handover Self-Optimization Management for Next Generation Networks
## 3 Velocity-Based Optimization Algorithm  
### HO Problem  
Improper configurations of HCPs increase the rate of RLF, thereby degrading the system performance. The high and low values of HCPs cause too late and too early HOs, respectively. Thus, the HCPs should be frequently adjusted according to the UE's mobility. In this work, the adjustment of the HCPs depends on the UE's speed and the reference signal received power (RSRP), which causes high HOPP and RLF. For example, when a user moves at high speeds, numerous cells (macro or small cells) will be crossed. In this case, the value of the HCPs should be decreased to avoid too late HO. By contrast, when a user moves at low speeds, it experiences a short distance movement and attains a good signal quality; thus, high values of HCPs are required to avoid too early HO. The objective of \begin{table}
\begin{tabular}{l l} \hline \hline
**Notation** & **Description** \\ \hline \(N_{u}\) & Set of UE \(U\in 1,2,...,|U|\) \\ \(N_{k}\) & Number of macro BSs \\ \(N_{l}\) & Number of small BSs \\ \(V_{u}\) & Velocity for UE \(u\) \\ \(PL_{u,k,l}\) & Path loss model \\ \(d_{0}\) & Reference distance between UE \(u\) and BS \\ \(d_{u},k,l\) & Distance between UE \(u\) and BS \\ \(\lambda_{l}\) & Wavelength at carrier frequency \(f_{c,l}\) \\ \(\chi\) & Gaussian random variable with zero \\  & mean and variance \(\sigma^{2}\) \\ \(SINR_{u,k,l}\) & SINR experienced by UE \(u\) at BS \(k\) \\ \(b_{ij}\) & Binary association indicator of user \(u\) \\ \(S_{u,k,l}\) & Channel gain for UE \(u\) at BS\(k\) \\ \(P_{u,k,l}\) & Received signal power by UE \(u\) at BS \(k\) \\ \(P_{AWGN}\) & AWGN power \\ \(\theta_{th}\) & Threshold level for HO decision \\ \(V_{u,t}\) & UE\(u\) Speed level at time \(t\) \\ \(V_{r}\) & Reference speed (medium speed)for entire simulation \\ \(RSRP_{S}\) & Serving RSRP UE \(u\) at BS \(k\) \\ \(RSRP_{l}\) & Target RSRP for UE \(u\) at BS \(k\) \\ \(\Delta\mathcal{H}\mathcal{O}\mathcal{M}_{u,t}\) & Updated HOM for each UE \(u\) at time \(t\) \\ \(\Delta\mathcal{TT}_{u,t}\) & Updated TTT for each UE \(u\) at time \(t\) \\ \(N_{F}\) & Number of failure HO \\ \(N_{C}\) & Number of successful HO \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of notations. ```
1:begin
2:Set up initial values of TTT and HOM
3:if\(Simulation\quad time\quad t=1\)then
4:\(HO\) Decision \(\longleftarrow\) false
5:else
6:if\(RSRP_{5}>RSRP_{7}+\theta_{th}\)then
7: Update \(\mathcal{HOM}\) and \(\mathcal{TTT}\) according to condition 1. 8: Run Algorithm 2. 9: Update \(\mathcal{HOM}\) and \(\mathcal{TTT}\)
10:else if\(RSRP_{5}<RSRP_{7}+\theta_{th}\)then
11: Update \(\mathcal{HOM}\) and \(\mathcal{TTT}\) according to condition 3. 12: Run Algorithm 2. 13: Update \(\mathcal{HOM}\) and \(\mathcal{TTT}\)
14:else
15: Update \(\mathcal{HOM}\) and \(\mathcal{TTT}\) according to condition 2. 16: Run Algorithm 2. 17: Update \(\mathcal{HOM}\) and \(\mathcal{TTT}\)
18:endif
19:\(\mathcal{AHOM}=\mathcal{HOM}_{t+1}\)
20:\(\mathcal{TTT}=\mathcal{TTT}_{t+1}\)
21: calculate HOF, HOPP, RLF
22:endif
23:end
```  
**Algorithm 1** Velocity-based optimization algorithm  
Figure 2: Flowchart of the proposed algorithm. The UE sends the MR to the serving BS during their mobility in the network. Then, the serving BS checks if the serving RSRP of the UE meets one of the above conditions. If the serving RSRP is greater than the target RSRP plus the threshold \(\theta_{th}\), then the current \(\Delta\mathcal{HOM}_{t}\) and \(\Delta\mathcal{TTT}_{t}\) are adjusted by adding the current values to the previous values of \(\mathcal{HOM}_{t-1}\) and \(\mathcal{TTT}_{t-1}\) according to UE speed. After updating the HCPs, the proposed algorithm will check if the HO decision is true or false. Algorithm 2 elaborates the HO trigger and decision process.