# Empirical Study on 5G NR Cochannel Coexistence
## 1 Introduction  
The 5G-NR-based non-public networks are becoming increasingly popular especially for industrial applications. This is owing to superior performance characteristics, mobility support, scalability and security aspects of 5G NR compared to other existing wireless technologies, e.g., Wi-Fi or 4G/LTE. Due to challenging requirements of industrial applications, these technologies do not adequetly meet the desired communication demands [1]. There are various 5G NR non-public network deployement options [2], either using spectrum licensed for public operator networks or locally licensed spectrum available in some markets. For instance, the 3.7-3.8 GHz spectrum is locally licensed for industrial use in Germany by the spectrum management authority (BNetZA) [3]. The increasing density of non-public network deployments in the local licensed and shared spectrum give rise to a cochannel coexistence problem, which has been discussed in the research community [4]. The performance characteristics of a non-public network may deteriorate due to spectral interference from coexisting networks. This performance impact depends upon a number of factors such as proximity of the interfering transmitter to the receiver of the non-public network and antenna directionality aspects, power levels of the transmitting node and that of the interfering entity, signal quality level at the receiver due to propagation characteristics, etc. While enhanced mobile broadband application use-cases target highdata rates and peak throughputs in the best effort manner, industrial use-cases are typically characterized by mission-critical communication requirements of high reliablity and low-latency, albeit support for the best effort background traffic is also required [5; 6]. Given that there is available system capacity for packet retransmissions, the overall throughput characteristics might remain unaffected even when packets need to be retransmitted due to interference from a coexisting network. However, the interference caused from the coexisting network may still lead to instantaneous link outages which are rectified by the error control mechanisms in the 5G NR protocol stack. These error correction mechanisms lead to instantenous latency spikes (e.g., due to Hybrid automatic repeat request (HARQ retransmissions), which can be intolerable for mission-critical industrial traffic. There exists various analytical and simulation studies on the performance analysis of mission-critical services due to interference from coexisting networks [7; 8]. However, so far there is no other systematic coexistence performance evaluation for a 5G NR non-public network based on real measurements. It is highly important to empirically quantify the impact of interference on throughput as well as latency, in both uplink and downlink directions, with different UE positions and under various traffic load conditions in realistic deployment scenarios. There is naturally a need to mitigate interference effects to guarantee the desired performance characteristics for mission-critical services. In this article, we present detailed over-the-air performance evaluation results obtained on an industrial shopfloor considering realistic deployment scenarios of a 5G NR non-public indoor network coexisting in the same spectrum as a 5G NR outdoor network. The throughput and latency characteristics of the indoor network in various realistic interference scenarios due to a coexisting outdoor network are compared with their respective baselines without the presence of interference from the coexisting outdoor network. We present the empirical performance results for synchronized, as well as different unsynchronized, TDD patterns used by the 5G NR indoor non-public network. In this article, the term unsynchronized TDD patterns refers to a scenario where the indoor and outdoor networks are using different TDD patterns. However, also in the \"unsynchronized\" scenario, the two networks have a common time reference and their respective TDD patterns are slot-aligned.