## 4 Discussion on the Proposed Technique and Results Obtained during the Experiments
### Discussion on the Results Achieved during Implementation of the Photovoltaic System  
In order to evaluate the optimization technique presented in the paper, the results achieved in the previous section are compared with the values obtained in the traditional design flow. As a reference method (denoted as \"traditional technique\"), the prototyping idea shown in previous authors' works is selected [13; 41; 43]. In particular, the presented photovoltaic system is designed without the application of the proposed functional decomposition. The whole procedure is the same, except for the optimization shown in Section 3.3.  
To examine the proper functionality, the validation of both systems (that is, the one achieved by the proposed technique and the traditional one) is executed. To perform this, results of the simulation of both systems are compared. It should be noted that validation returns exactly the same results, which means that the applied optimizations do not interfere with the functionality of the system.  
Finally, the evaluation of the presented optimization technique is performed. Table 3 shows the implementation results obtained for both techniques. The first column contains the analyzed resources: look-up tables (LUTs), flip-flops (FFs), input/output blocks (IOs), and buffers (BUFGs). The second and third columns present the utilized resources obtained with the proposed and traditional design technique, respectively.  
Figure 14: Hardware validation of the designed photovoltaic system with Nexys4 DDR board.  
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Resources** & **Proposed Technique** & **Traditional Technique**[13; 41; 43] \\ \hline Number of utilized LUTs & 91 & 126 \\ Number of utilized FFs & 114 & 114 \\ Number of utilized IOs & 38 & 38 \\ Number of utilized BUFGs & 1 & 1 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison of the utilized FPGA resources.  
From the values shown in Table 3, it can be noticed that the proposed technique permits dropping the number of utilized look-up tables. The traditional design flow consumes 126 LUTs, while the presented optimizations allow for the reduction in utilized logic blocks by 28%.  
Furthermore, let us compare the impact of the sequential optimization--a novel technique proposed in this paper. The obtained synthesis results are as follows:  
* initial system (without any optimization): 126 LUTs, 114 FFs,
* system with combinational optimization only: 95 LUTs, 122 FFs,
* system with combinational and sequential optimizations: 91 LUTs, 114 FFs.  
It can be noticed that the innovative optimization of the sequential areas of the concurrent control system benefited a significant reduction in the resources. However, the application of the functional decomposition is not enough in this particular case. Although the number of LUTs decreases, the number of registers becomes much larger. Nevertheless, optimization of the redundant flip-flops proposed in this work drops down the number of utilized registers and additionally decreases the number of LUTs.  
To summarize the above discussion, let us underline that in the context of FPGA resource utilization, the obtained values should be considered as a very good result. The \"saved\" resources can be, for example, effectively utilized by other blocks of the prototyped concurrent control system. Moreover, such a reduction is essential in the case of farms of photovoltaic panels. Assume a system that consists of hundreds or even thousands of such solar cells. The initial estimation shows that the traditional design technique allows for the implementation of up to 503 solar panels. Conversely, the application of the proposed optimization method increases the possible utilized panels up to 696. Of course, those are just initial estimations (although the implementation of photovoltaic farms is planned in our further papers); nevertheless, it shows the practical benefit of the proposed technique.