# Chronic Obstructive Pulmonary Disease Warning in the Approximate Ward Environment
## 3 Design Implementation and C-Band Sensing  
In a communication link, the channel properties must be known in advance, which could be analyzed with the help of wireless channel information (WCI). There exist multiple effects like scattering, fading, and multipath propagation [20], which affect the WCI of RF signal and which propagate between transmitter and receiver. The RF signal could be represented as follows,  
\[H(a)=\left|\left|H(a)\right|\right|e^{(b\angle H(a))} \tag{13}\]  
In Equation (13) \(H(a)\) represents the WCI and the phase and amplitude are represented as, \(\mid\mid H(a)\mid\mid\) and \(\angle H(a)\) respectively. This experiment was performed using C-Band operating at 4.8 GHz frequency. In our research we have used an RF signal generator (DSG 3060) connected to an omnidirectional antenna (Rubber duck) at the transmitter side with an output power of 100 mW (20 dBm) and with typical phase noise of \(<\)\(-\)110 dBc/Hz at 20 KHz. This antenna propagates the RF signal to 360 degrees horizontally with \(\frac{1}{4}\) dipole length of 26 mm. At the receiver side, a desktop mounted with network interface card (MCX416A-BCAT), worked as a receiver. The experiment was performed in different indoor environments. We used microwave absorbing material to reduce the multipath propagation. The WCI then extracted [21] using this NIC mounted in a modified desktop PC. The NIC card revealed only 30 subcarriers' information represented as single WCI packet. After successful pinging of an AP, we received 10 WCI packets per second. The received WCI was in the form of matrix of 30 \(\times\) 1 represented as channel frequency response (CFR) and shown as,  
\[CFR_{(30x1)matrix}=\left[h^{1},h^{2},\ldots,h^{n}\right] \tag{14}\]  
In the above equation the \(h^{1}\) represents the CFR of subcarrier number 1 and \(h^{n}\) represents the CFR for the 30 th subcarrier as there are only 30 subcarriers.  
Figure 1 shows the experimental settings for the proposed methodology. We have adjusted the distance between the devices and patient according to system feasibility. The height of the transmitter, receiver and patient was adjusted around 1.5 m from the ground and 4.5 m from the ceiling. The total height to the ceiling is 6 m from the ground.  
We obtained the raw WCI for breathing activity of a person imitating a COPD patient. There are 30 subcarriers in total but for the correct breathing information subcarrier #19 and 21 show better results for normal and abnormal breathing and for coughing, subcarrier number 7 gives a reasonable result. We examined all 30 subcarriers [22] and compared their results with our digital respiratory sensor. We performed that experiment multiple times and in all cases the mentioned subcarriers showed better results very near to the digital respiratory sensor's results. In our research we focused on the efficient monitoring of breathing by exploiting the 5G technology. As C-Band is operating on 4.8 GHz frequency, it can be easily integrated with the 5G system. The internet of things (IoTs) operate at a similar frequency band. This way we can easily perform the efficient spectrum utilization regarding 5G. Table 2 shows the numbers of subjects involved in the experiment.