# Evaluation of 5G Positioning Based on Uplink SRS and Downlink PRS Under LOS and NLOS Environments
## 2 Methodology  
### The 5G Signal Structure and the Role of SRS and PRS for Positioning  
The proposed method evaluates 5G positioning performance by utilizing UL-SRS and DL-PRS in both LOS and NLOS scenarios. The methodology involves the transmission of SRS signals from the UE to the gNBs for uplink-based positioning and the transmission of PRS signals from the gNBs to the UE for downlink-based positioning. The performance of SRS and PRS transmission was evaluated through the implementation of a MATLAB R2022b-based simulation, which utilized the nrSRSConfig and nrPRSConfig tools. The utilization of TOA measurements facilitates the estimation of the UE location by determining the propagation delay of the received signals. For the purposes of simulation, it is assumed that the gNBs and UE are synchronized. The impact of synchronization errors on TOA-based estimation is beyond the scope of this study and is not considered. The positioning accuracy is determined by varying the comb size and inter-site distance, particularly highlighting performance variations between LOS and NLOS scenarios. The methodology is visually presented in Figure 1.  
The proposed methodology is validated through a simulation setup that emulates a realistic urban environment with inter-site distances of 100 and 150 m between gNBs. The UE remains in motion at 3 km/h, relying on these gNBs for pos  
Figure 1: The 5G positioning based on UL-SRS and DL-PRS under LOS and NLOS scenarios. of resource elements across different symbols is intended to span all subcarriers, thereby resulting in an SRS/PRS design that follows a comb-pattern structure, as illustrated in Figure 2a,b. This approach ensures a comprehensive evaluation of positioning performance by using both uplink and downlink reference signals. The methodology is characterized by a systematic approach involving the simulation of urban scenarios under both LOS and NLOS conditions, along with variations in inter-site distances. The frame structure employed in this research is illustrated in Figure 3 according to the 5G NR standard. The frame is characterized by a duration of 10 milliseconds (ms), subdivided into 10 subframes, with each subframe spanning 1 millisecond (ms). These subframes are further subdivided into slots, with the number of slots per subframe varying based on the subcarrier spacing (SCS) defined by 5G NR numerology. At a sampling rate of 15 kHz, the SCS is equivalent to (\(\mu=0\)). This configuration results in a slot duration of 1 ms, which corresponds to one slot per subframe. Increasing the SCS to 30 kHz (\(\mu=1\)) has the effect of reducing the slot duration to 0.5 ms. Consequently, this doubles the number of slots per subframe to two. Similarly, for the highest numerology level considered, 240 kHz (\(\mu=4\)), the slot duration is 62.5 microseconds, resulting in sixteen slots per subframe [40]. Figure 3: Frame structure of 5G NR. Figure 2: Signal transmission: (**a**) UL-SRS signal transmission from UE; (**b**) DL-PRS signal transmission from gNBs. The 5G standard [5] employs OFDM symbols with a Cyclic Prefix (CP) as a guard interval to mitigate inter-symbol interference. In the time domain, OFDM is a method of decomposing a high-speed data stream into multiple parallel streams with reduced transmission rates. In the frequency domain, OFDM partitions a wideband signal into narrowband subcarriers, with each subcarrier carrying a fraction of the data. The configuration of SCS and CP duration plays a pivotal role in defining the temporal resolution required for high-precision positioning, particularly in TOA-based methods. In normal CP mode, each slot comprises 14 OFDM symbols, whereas in extended CP mode, each slot contains 12 symbols. The CP duration, although overhead in throughput terms, provides critical robustness against multipath distortion. This, in turn, improves the reliability of delay-based positioning in both urban canyons and indoor scenarios. As illustrated in Figure 4, the NR frame structure is composed of \(10\cdot 2^{\mu}\) equally sized slots.