# Remote Radio Frequency Sensing Based on 5G New Radio Positioning Reference Signals
## 5 Results  
### Simulation Setup  
Simulations were performed using MATLAB R2023B and 5G Toolbox. The Frequency Division Duplex (FDD) mode was exploited. The assumed downlink carrier parameters are presented in Table 3. The values of the radar target parameters used in the simulations are given in Table 4, i.e., range, velocity, and reflection gain. The first two parameters do not require additional explanation. Reflection gain defines how strong the echo signal is in the signal recorded by the receiver (see Equation (11)). For \(g=\frac{0.01*(1+1)}{\sqrt{2}}\), the echo component is 100 times weaker than the light-of-sight component. This reflection gain value was selected based on our previous field studies [31; 32; 33].  
Table 5 shows the PRS configuration parameters shared across all configurations. The detailed parameters of each PRS configuration used in the simulation are presented in Table 6, which has columns indicating the number of REs occupied by PRS in a single slot and the total overhead caused by that. The more REs are intended for PRS, the larger the overhead, which means that fewer REs can be dedicated to communication tasks. This can result in lower bit throughput.  
PRS configurations are primarily categorized into two groups: those with two PRS resources (PRS-6-6-2-RES, PRS-4-4-2-RES, PRS-2-2-2-RES), and those with one PRS resource (PRS-2-2-1-RES, PRS-4-4-1-RES, PRS-6-6-1-RES, PRS-12-12-1-RES). The first group has the denser pilot array, utilizing two times more pilots compared to each configuration of the second group. Such an arrangement should enhance the sensing capabilities in poor radio conditions (e.g., lower SNR). The use of two PRS resources enables the placement of two pilots on the same subcarrier. This increases the maximum observable Doppler frequency shift (see Equation (17)) but at the same time increases the pilot overhead. The second group of configurations with only one PRS resource exhibits a lower maximum observable Doppler frequency shift and decreased sensing capabilities; however, it is beneficial when additional resources are required to obtain higher bit throughput in the communication part of the system. Two of the configurations presented (PRS-12-1-2-RES and PRS-12-1-1-RES) are not currently supported by the 3 GPP standard due to the invalid value of \(L_{PRS}\), but they are included in the simulations to show their potential benefits for 5G networks to have such configurations available. These configurations occupy very few REs in a single slot, which allows the operator to allocate more resources for data transmission. Moreover, the usage of these two extra configurations would allow better adjustment to radio channel conditions.  
The selection of values of the target parameters follows the rules described in Section 3, and only one target is present at the same time in a single iteration of the simulation. The radar targets were selected in such a way that neither velocity nor range exactly fell into the IFFT/FFT spacing (bins) of the CIR and DDM matrices (i.e., fractional, not integer, position of targets in DDMs was assumed). For this reason, blur occurs in the DDM.  
This is the worst-case scenario that can occur in field conditions; therefore, it is used to measure the performance quality of the different PRS configurations used in simulations. For velocity estimation, the high-resolution spectral analysis method of Aboutanios and Ye was used [34].