## 5 Experimental Results
### Experimental Results for BCC Algorithm
#### 5.2.2 Power Consumption Analysis of BCC
The power consumption for communication per server in S2S-WiDCN was calculated as:  
\[P_{Wireless}=7P_{60 GHzTran}+P_{WifiCntrl}+P_{NIC}, \tag{24}\]  
where \(P_{60 GHzTran}\) is the power consumption of a single 60 GHz transceiver required for each of the six sectors and the horizontal link and \(P_{WifiCntrl}\) is the power consumption of the IEEE802.11 2.4/5 GHz ISM adapter for the control channel. Finally, the total power consumption in S2S-WiDCN was:  
\[P_{Network(WiDCN)}=N_{Core}P_{Core}+N.P_{Wireless}. \tag{25}\]  
Comparative Analysis of Power Consumption for BCC:  
The IT power consumption of wired and S2S-WiDCN data centers with different consolidation methods including the BCC algorithm with variation in the flow injection rate are shown in Figure 8. These power consumption are computed based on the power model described in the previous sub-section for each of the simulation cases ran in the NS-3 simulator for different consolidation algorithm. In [45], it is observed that the majority of the utilization factor of a server is within the range of 20-30%. Here we adopted the utilization of the server capacity of each server without any consolidation from [45]. Figure 8a represents the power consumption of the HPC data center with no consolidation normal condition (NC) while Figure 8d represents BCC. The figure also contains the power consumption pattern if Clustered Exhaustive Search (CES) algorithm was adopted instead of BCC in Figure 8b. CES is a variant of the BCC algorithm, which finds the optimal migration within each cluster using the exhaustive search, hence being much more computationally expensive. For the sake of comparison, we also simulated a network-unaware greedy approach based consolidation (GRD) which is a variant of NICE [11] and the power consumption pattern is shown in Figure 8c. For both wired and wireless networks, at lower injection rates, all the consolidation techniques performed similarly and resulted in significant power consumption reduction compared to NC, while CES consumed the least power. BCC algorithm consumed only 2.83% more power than CES, whereas CES was significantly more computationally complex than BCC because of exhaustive search as discussed in Section 4.4. Hence during the consolidation operation, for moderate to large size of data centers, CES algorithm became impractical to implement as it was not able to perform real-time operations, whereas the BCC algorithm could. BCC algorithm for S2S-WiDCN reduced 37% power consumption compared to the NC case. For higher injection rates, CES and GRD consumed significantly less server power compared to BCC for wired networks. This was because the CES and GRD did not consider the network bandwidth constraints while consolidating, resulting in more aggressive consolidation that in the BCC. Therefore, this difference became more apparent with increase in flow injection rates. However, this reduction of power came at the cost of the lower throughput because the CES and GRD algorithms did not consider the network traffic characteristics. This impact on performance will be discussed in detail in Section 5.2.3. Moreover, the computational complexity of CES was orders of magnitude higher than the BCC. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Device** & **Model** & **Used in** & **Power (W)** \\ \hline Access Layer Switch & Cisco 9372 & Fat-Tree & 210.0 \\ Aggregate Layer Switch & Cisco 9508 & Fat-Tree & 2527.0 \\ Core Layer Switch & Cisco 7702 & Fat-Tree, S2S-WiDCN & 837.0 \\ Network Interface Card & Silicon PE2G2I35 & Fat-Tree, S2S-WiDCN & 2.64 \\
60 GHz Transceiver & Analog Device HMC 6300/6301 & S2S-WiDCN & 1.70 \\ IEEE802.11 2.4/5 GHz Adapter & D-link DWA-171 & S2S-WiDCN & 0.22 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Power consumption of different data center network (DCN) components. For BCC consolidation in S2S-WiDCN, similar to the wired network, with the increase in flow injection rate, the server power consumption increased, while for CES and GRD power consumption remained the same.