# A Comparative Analysis of Wi-Fi Offloading and Cooperation in Small-Cell Network
## 5 Performance Evaluation
Next, the simulation results in Figure 5 shows the effect of the increase in user density on the achievable data rate per user of SCRE and SORE in the SC network. We evaluate these results with 3 SBSs, 10 RBs and 100 bits/s rate threshold value. As the number of UEs increases from 5 to 30, a significant decrease in the achievable date of both SCRE and SORE is observed. This decrease in the achievable data rate is due to increase in the number of UEs without changing the resources present in the network, therefore reducing the resources per UE. For SCRE which is represented by a dashed magenta line in Figure 5, the QoS per user degrades and is similar to non-cooperative/Wi-Fi offloading scenario. However, as the density of the user increases, the QoS per user of cooperation achieves the QoS per user in non-cooperative/Wi-Fi offloading case. This is due to the of the maximum number of SBS to user association constraint. As the number of UEs increase, a UE cannot be associated with other SBS because each SBS can barely serve its own users, and there is no space left for cooperation. Similar to SCRE, the performance of SORE is significantly better than non-cooperative/Wi-Fi offloading case in a less dense network, whereas in a dense network the increase in QoS per user as compared to non-cooperative/Wi-Fi \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Symbols** & **Values** \\ \hline Maximum power & \(P_{max}\) & 23 dBm \\ No. of SBSs & \(M\) & 3–15 \\ No. of UEs & \(N\) & 5–30 \\ No. of RBs & \(K\) & 5–30 \\ Rate threshold & \(R^{th}\) & 50–300 bits/s \\ Noise variance & \(\sigma^{2}\) & \(1.0\times 10^{-15}\) \\ Saved power of SBS i & \(\Delta_{i}\) & 0.025 Watts \\ Min channel difference threshold & \(v^{th}\) & 0.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Evaluation Parameters. Figure 3: Analysis of Rate allocation in Cooperation regarding Association. offloading case depends on the Wi-Fi leftover rate. In other words, if the Wi-Fi network is crowded, the leftover capacity that it can share with LTE UEs is less and thus the increase in data rate is less compared to a less crowded Wi-Fi network. The performance of SCRE is better as compared to SORE in a less dense environment. However, with the increase in the number of UEs, the performance of SCRE becomes worse than the performance of SORE. The performance degradation in SCRE as compared to SORE is dependent on the density of the Wi-Fi network (or the leftover Wi-Fi rate \(L_{i}\)). With higher leftover rates value, SORE performance becomes better. Thus, we can conclude that cooperation outperforms Wi-Fi offloading in a less dense network whereas Wi-Fi offloading is more advantageous in a dense SC network, provided there is sufficient leftover Wi-Fi capacity available. The percentage increase in rate of Wi-Fi offloading is 43% and of cooperation is 32% as compared to non-cooperative/Wi-Fi method. After executing both SCRE and SORE, the value of switching parameter for user density \(\beta\) is passed to SCO to perform switching. The performance of SCO is shown as a dotted green line which is better than the performance of either of SCRE and SORE. It also shows that for \(\beta<=10\) (less dense network), it performs similar to SCRE and for \(\beta>10\) (dense network), it performs similar to SORE. Figure 4: Analysis of rate allocation in Wi-Fi Offloading regarding leftover rate. Figure 5: Averaged Achievable data rates per user by changing No. of Total UEs in Cooperative Communication, Without Cooperative Communication and by taking 5, 10, 15 leftover capacity in Wi-Fi offloading and overall 3 SBSs. Figure 6 shows the effect of increase in rate threshold on the QoS per user of SCRE and SORE. These results are evaluated using 10 UEs, 3 SBSs and 10 RBs. With the increase in rate threshold, the performance of SCRE increases significantly when the number of UEs in the network is less \((N=5,10)\), whereas only a slight increase is observed for a greater number of users \((N=20)\).