# Empirical Study on 5G NR Cochannel Coexistence
## 4 Experimental Methodology  
In order to systematically carry out the coexistence measurements, we developed a tool for configurable traffic generation and carrying out accurate one-way (DL/UL) latency and throughput measurements. We have first measured the baseline latency and throughput, i.e., without interference, and later measured latency and throughput in the presence of interference. The baseline peak throughput performance depends upon the system bandwidth configured. Higher peak throughput is achieved with a larger bandwidth and vice-versa. The amount of interference level and its direction (UL/DL) determines the performance loss compared to the respective baseline. Various aspects of interfernce impact on the performance of the indoor network has been evaluated.  
Our over-the-air coexistence measurements have been performed in the 3.7-3.8 GHz 5G N78 TDD band, which is allocated with a local license for industrial application use in Germany. Our measurements have been carried out at the 5G Industry Campus Europe (5G ICE) in Aachen [24], which has an outdoor network deployment covering an area of approximately 1 km\({}^{2}\), with four outdoor macro sites colored in yellow in Figure 2a. As part of 5G ICE, we have selected the indoor network deployment on the shopfloor of the Fraunhofer Institute for Production Technology (IPT), shown as a green rectangle with an area of ca. 2700 m\({}^{2}\). The power levels for the indoor and outdoor networks are in the nominal operating range. During the empirical study, both the indoor and outdoor networks were exclusively used and we ensured no other device was operating in the two networks.  
The coexistence measurements were conducted with four different UE locations, two indoor and two outdoor UE locations. The four scenarios are as described in Table 1 according to Figure 2b. The first scenario is the worst-case of interference, when the indoor and outdoor UE are close by to each other at a distance of around 50 cm from the window of the shopfloor. In the second scenario, the outdoor UE is in the same location and the indoor UE is moved at distance of 10 m from the window, close to a robot cell. Then, in the third scenario the indoor UE is moved to a location next to the factory shopfloor window, while the outdoor UE is moved away from the shopfloor to a distance of 15 m. Finally, the indoor UE was placed close to the robot cell, while keeping the outdoor UE away at a distance of 15 m from the shopfloor.  
Figure 1: Illustration of interference situation caused by coexisting indoor and outdoor networks. (**a**) Interference links between base stations and UEs of indoor and outdoor networks when different TDD patterns are selected. (**b**) Different TDD patterns used in the indoor network compared to the outdoor network result in both near–far interference and cross-link interference.  
As described in Table 2, both indoor and outdoor networks are based on a mid-band 5G non-stand alone (NSA) system with independent baseband and core networks. The 4G anchor cell of both networks is on the 2300 MHz B40 frequency band while the 5G leg of the NSA deployment uses the full 100 MHz bandwidth available within the n78 band of the 3.7-3.8 GHz spectrum, which fulfills the requirement for cochannel networks.  
For our measurements, we used one test UE for the indoor network and one test UE for the outdoor network. Both the UEs are identical and based on Qualcomm x55 modem chipset. We ensured that no other devices were active besides the test devices when performing measurements.