# Empirical Study on 5G NR Cochannel Coexistence
## 5 5G Performance for Industrial Control
### Synchronized TDD Patterns  
Current cellular wide-area network deployments on the TDD spectrum use the same TDD pattern on all cells in order to avoid interference. According to the standardization technical specifications of 3 GPP 38.401 Section 9.1, all networks must have a common clock reference. Hence, in order to keep the same harmonized TDD pattern DDDDU regulated for wide-area networks in Germany, the first set of tests were conducted to study the indoor network performance in the presence of interference from the outdoor network when both the networks use the same TDD pattern, referred to as synchronized TDD patterns. The interference for the synchronized TDD pattern scenario can only occur between slots on the same transmission directions, i.e., DL slots interfere only with the DL slots and UL slots interfere with the UL slots of the two networks. Therefore, the interference links for the synchronized TDD pattern in DL and UL are only the near-far interference links, as illustrated in Figure 1. The first scenario studied for cochannel interference and synchronized TDD pattern is for indoor and outdoor UE deployments next to the window, as shown in Figure 2b. For median values, the increase in latency compared to baseline for both indoor DL and UL slots is negligible, as can be observed from Figure 3. Similarly, for the 99 th percentile value, the indoor DL latency increase due to the DL near-far interference being low, while results from UL near-far interference show higher delays of 0.7 ms and 5.3 ms, respectively. For the 99.9 th percentile value, the increase in latency compared to baseline follows a similar trend. Here, the UL near-far interference impact is higher than the DL near-far interference. Compared to baseline, the increase in latency in the indoor DL and UL for the 99.9 th percentile value are 5.1 ms and 7.5 ms, respectively.  
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,  
Figure 3: Increase in DL (**a**) and UL (**b**) latency compared to their respective baselines for synchronized TDD pattern (DDDDDU) used by the indoor and outdoor networks.  
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.  
For other UE deployment locations, it can be observed in Figure 4 that the DL (Figure 4a) and UL (Figure 4b) latencies increase compared to their respective baselines with a synchronized TDD pattern. The worst-case interference scenario is the previously analyzed result. The robot cell scenario is the result of the latency increase for a different indoor UE position (robot cell) within the test factory shopfloor and same outdoor UE position (next to the window). The remaining scenario is for the indoor UE close to the window and the outdoor UE at some distance from the shopfloor. The indoor DL performance for the robot cell scenario, where the victim of the indoor network is the indoor UE and the aggressor is the outdoor BS, shows no impact due to DL interference. Similarly, for the interference far away scenario, no impact is observed in the DL latency. Hence, it is observed that increasing the distance between the UEs helps to reduce the impact of DL interference. On the other hand, the indoor UL latency increase for the robot cell scenario is slightly greater and no latency increase is observed for the interference far away scenario.