# Optimized DM-RS Configuration for Improved 5G New Radio Network Capacity and Performance.
## 1 Introduction  
On average, mobile data traffic has more than doubled every two years for the last 10 years [1]. The current growth rate is approximately 7% per quarter, or 30% year over year. It is forecasted to grow 20-30% per year in most regions in the next few years, with sub-20% growth subsequently. These figures do not include fixed wireless access traffic. The introduction of XR-type services, including augmented reality (AR), virtual reality (VR) and mixed reality (MR), will bring so far unquantified contributions to traffic growth. Simultaneously, the demand for good network performance, high data throughputs and low latency is increasing, which puts pressure on mobile operators to secure sufficient capacity. Network designers can address capacity demands with spectrum addition and introduction of new frequency bands, by increasing network density or by improving spectral efficiency. Spectrum assets are scarce; new bands are typically positioned on higher frequencies with more radio propagation challenges, increasing the cost of deployment. Building new sites, on the other hand, poses huge challenges. In most markets it is difficult to find new locations for macro sites, and small cell deployment is also a challenging and expensive task. In such a situation, achieving optimal spectral efficiency is an important task for mobile operators that directly impacts the total cost of ownership. Each contribution to improved spectral efficiency matters more than ever.  
Spectral efficiency is driven by link adaptation performance and the ability to control interference (predominantly inter-cell) [2], MIMO performance in terms of the number of layers used and multi-user MIMO scenario adoption, and finally radio interface time-frequency resource grid organization and related overhead. Concerning overhead reduction and potential spectral efficiency improvements, the DM-RS signal configuration is a good candidate for optimization due to its potentially large contribution to unnecessary overhead and is the subject of research presented in this paper. The main goal was to improve spectral efficiency in commercially deployed 5G/NR networks through the reduction in the allocation of DM-RS signals, without any introduced degradation, within use cases of interest that will not be affected.  
In Section 2, an overview of related work by other researchers is provided. Theoretical background is given in Section 3, with a focus on the new 5G/NR radio interface, the main differences compared to the systems of fourth generation (LTE), a deep dive into the DM-RS configuration and current 5G deployments around the world, achieved spectral efficiency and initial settings in commercial networks with a focus on DM-RS configuration aspects. Section 4 analyzes Doppler shifts theoretically and lays the foundation for optimization of the DM-RS configuration for different use cases, network configurations and speeds of terminals. Finally, in Section 5, testing of different DM-RS configurations and analysis of the impact on network performance and user experience from various perspectives is presented, followed by a discussion of the results and a conclusion of the research in Section 6.