## 6 System Deployment  
With a functional mathematical model, the implementation was carried out in a standard lab room in open space. Our proposed design consists of one Impini xArray Gateway RFID Reader located at the highest point (usually hanging from the ceiling) in our lab and the reference tags located on the floor. For the reference tags, we mapped them out in a square matrix arrangement of \(n\) * \(n\), and each reference tag was assigned a location value for the first test of a wider range with less accuracy. For the experiments, since we used one neighbor, there was no need for weight adjustment and hence we could use the actual reference tag as the location. Since the Impini xArray reader is a fixed infrastructure RFID reader, we used its SDK and low-level-reader protocol to change its mode and configure it to work in wide monitoring scenarios. For the reference tags, we chose UHF passive RFID cards. The tags were passive tags, meaning that they did not have an independent power source and they relied entirely ion the reader for their power. The main reason for choosing UHF tags the read range, which is the largest compared to other tags, as shown in Table 1.  
Table 1 clearly shows that the higher the frequency, the longer the read range. We set RFID reference tags almost in a standard square manner and each passive tag represented a set coordinate point ranging from \(X\) (\(X=1,2,\ldots,x\)) and \(Y\) (\(y=1,2,\ldots,y\)). The final reference tag's location would be the coordinates from the two values. Thus, if our target tag was located at the bottom right corner (with respect to the antenna reader) of the room, then the location entry would be validated as \(l=(x,y)\), with the two values being the maximum values of row and column length, respectively. \[l= \begin{bmatrix}l_{11}&l_{12}&\cdots&l_{1y}\\ l_{21}&l_{22}&\cdots&l_{2y}\\ \vdots&\vdots&\vdots&\vdots\\ l_{x1}&l_{x2}&\cdots&l_{xy}\end{bmatrix}  \tag{8}\]  
Thus, depending on the accuracy and range, we could determine the overall location. Moreover, for finer locations and pinpointing exact coordinates, we can use more neighbors and then obtain weights for each reference tag; upon obtaining the weights, we can then simply place the location points using the weighted value. This would be practical for finer location values, but considering the abundancy and relative price of passive RFID tags, being cheap, we can afford to instead simply use multiple RFID tags. When the final setup is made, the arrangement will resemble Figure 7.  
The UHF RFID tag has 4 memory banks, and they are the Electronic Product Code (EPC), user memory, reserved memory and tag identifier memory (TID). To identify the tags in the most efficient way possible, we configured our antenna as shown in Table 2.  
Once the EPC and RSSI values were matched, we obtained the corresponding matrix of reference and target tags. Then, we started to calculate the Euclidean distances of the \begin{table}
\begin{tabular}{c c c} \hline \hline
**Tag Type** & **Frequency Range** & **Read Distance** \\ \hline Low frequency (LF) & 120–140 kHz & 10–20 cm \\ High frequency (HF) & 3–30 MHz & 10–20 cm \\ Ultra -high frequency (UHF) & 869–928 MHz & 3 m \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Frequency and range comparison. target tag with respect to the landmarks. The distances were calculated using the following formula below:  
\[E_{j}=\sqrt{\sum_{i=1}^{n}(\theta_{i}-S_{i})^{2}} \tag{9}\]  
where \(j\in(1,\;\;m)\) is the Euclidean distance in signal strength between a tracking tag and the reference tag \(r_{j}\). Let \(E\) denote the location relationship between the reference tags and the tracking tag, i.e., the nearer the reference tag to the tracking tag, the smaller the \(E\) value. Upon acquiring the Euclidian distances, we could use the number of neighbors to calculate the location of the tags. If we use one neighbor, then the tag with the lowest values means that it has the highest correlation with the target tag, and it is designated as the location of the target tag.