## 5 System-Level Performance Evaluation  
The main objective of this section is to analyze both qualitatively and quantitatively the benefits that the integration of the proposed compression module can offer to a real WSN platform, by taking into account both the performance and the energy conservation. The degree by which the bandwidth required to transmit a specific amount of data is reduced, due to utilization of compression, depends solely on the algorithm and not on the integration efficiency. However, the system-level transmission delay and the energy consumption metrics depend heavily on the hardware design of the compression modules, as well as on the integration of the component to a specific WSN platform. To evaluate both compression delay and compression power consumption, we assume a signal sample of \(X\) Bytes that can be compressed by \(Y\%\) and adopt the following rationale. As far as the transmission delay is concerned, the two equations that enable us to calculate the required time interval to send the respective information with and without the compression module are the following ones. _Without the compression module integrated:_  
\[Tx_{no\_compress}=Tx_{XBytes}, \tag{2}\]  
where \(Tx_{XBytes}\): Represents the time interval required to successfully transmit \(X\) Bytes and it is measured using a specific platform and specific WSN communication technology. _With the compression module integrated:_  
\[Tx_{compress}=Tc_{XBytes}+Tx_{x\times y\%Bytes}+Tdc_{XBytes}, \tag{3}\]  
where \(Tc_{XBytes}\) is the time interval required to compress \(X\) Bytes that can be accurately calculated for a specific processing clock frequency of the implementation presented in Section 4. \(Tx_{x\times y\%Bytes}\) is the time required to successfully transmit the compressed amount of data which can be accurately measured using a specific platform and a specific WSN communication technology. \(Tdc_{XBytes}\) is the time interval required to decompress the compressed data back to \(X\) Bytes which, without loss of \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Clock Frequency (MHz)** & **Total Power (mW)** & **Dynamic Power (mW)** & **Static Power (mW)** \\ \hline
1 & 114.27 & 15.53 & 98.74 \\
62.5 & 198.52 & 98.45 & 100.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Compression module power dissipation (Spartan3E Xilinx FPGA Technology). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Configurable Logic Block (CLB) Slices** & **Flip Flops (FFs)** & **Block RAMs** & **I/Os** \\ \hline
1676/7680 \(-\) 21\% & 1148/15,360 \(-\) 7\% & 7/12 \(-\) 29\% & 60/173 \(-\) 34\% \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Compression module resources (Spartan3E xc3s100 \(-\) 4 ft256 Xilinx FPGA Technology). accuracy, can be considered equal to \(T_{CXBytes}\) since the compression and decompression algorithms are symmetrical in the proposed solution. Moving on to energy consumption the respective equations used are as follows. _Energy consumption without integrated compression module:_  
\[Ex_{no\_compress}=P_{tx\_radio}\times Tx_{XBytes}=V_{tx\_radio}\times I_{tx\_ radio}\times Tx_{XBytes}, \tag{4}\]  
where \(Ex_{no\_compress}\) is the energy consumed for sending successfully \(X\) Bytes of data. \(P_{tx\_radio}\) is the transmission power consumption of a specific radio transceiver. \(V_{tx\_radio}\) is the voltage supply required of specific radio transceiver (provided by respective datasheets). \(I_{tx\_radio}\) is the current draw during transmission of a specific radio transceiver (provided by respective datasheets). \(Tx_{XBytes}\) is the time required to successfully transmit \(X\) bytes; it is measured using a specific platform and a specific communication technology. _Energy consumption with integrated compression module:_  
\[ \begin{array}{c}Ex_{compress}=Ec_{XBytes}+E_{tx\_{X}\times y\%Bytes}=(P_{ compr}\times Tc_{XBytes})+(P_{tx\_radio}\times Tx_{X\times y\%Bytes})=\\ (P_{compr}\times Tc_{XBytes})+(V_{tx\_radio}\times I_{tx\_radio}\times Tx_{X \times y\%Bytes}),\end{array}