# Practical Performance Analysis of Interference in DSS System
###### Abstract  
The 5G network is developing rapidly. However, due to spectrum resource limitation, it is expected to use the 5G network to ensure high resource utilization and network efficiency, while keeping part of 4G in the same band for existing 4G users. Dynamic spectrum-sharing (DSS) technology enables 4G/5G wireless networks to coexist in scarce spectrum resources and dynamically allocates spectrum resources in the same band. 4G/5G DSS has been successfully commercialized in some countries such as Germany and Brazil. However, complex 4G/5G DSS networks will introduce intra-frequency interference in the inter-system, which will affect network performance. Therefore, we innovatively proposed two interference mitigation schemes: buffer setting and rate matching. Furthermore, we have verified the practical performance of both schemes in a commercial network for the first time to determine the feasibility of the schemes. From theory, simulation, and practical analysis, both schemes can effectively mitigate the interference of the inter-system introduced by DSS: increasing the network rate by 60% in the interference environment and improving the user experience in the DSS architecture. dynamic spectrum sharing; 4G network; 5G network; interference mitigation; rate matching; buffer setting +
Footnote †: journal: _Sci. Secondly, 4G evolves stably to 5G: When NR is deployed, operators can divide 4G low-frequency resources and give a fixed bandwidth. It cooperates with the high frequency regime to build 5G after refarming, that is, the carrier aggregation (CA). The CA was studied in [11; 12; 13; 14]. This scheme has separate dedicated spectrum resources for LTE and NR, deployed as neighbors on the same low-frequency band [15]. However, this hard-partitioning approach will reduce the available 4G spectrum resource, leading to 4G network congestion and the risk of degraded 4G user experience. In the early stages of 5G deployment, terminal penetration and lack of users, and 5G deployment in reserved dedicated carriers may result in an inefficient spectrum. How to dynamically adjust the frequency resource allocation according to the service volume to ensure stable evolution from 4G to 5G is an urgent issue to be solved [16]. Dynamic spectrum sharing (DSS) can effectively solve the above problems. 4G/5G dynamic sharing allows LTE and NR to work on the same band and share frequency resources dynamically between LTE and NR according to the service ratio [17]. DSS realizes the decoupling of the system and spectrum. The same spectrum can be scheduled by multiple systems at the same time, which improves the efficiency of spectrum use and reduces the risk of shifting the LTE frequency in the early stage of 5G broadband construction. While sharing the spectrum between 4G and 5G systems via DSS would result in wasted resources, DSS is an effective and feasible transition method to address the growing high data rate and capacity needs of mobile network operators (MNOs) [18]. This paper is based on the DSS technology, which is a reference for the rapid development of global 5G networks and vertical industries. From a technical point of view, 4G/5G allows dynamic spectrum sharing mainly because the NR protocol design originates from LTE, which has a high degree of inheritance and similarity. The third generation partnership project (3 GPP) fully considered the need for dynamic sharing of NR and LTE spectrum at the beginning of the Release 15 NR system design. Many designs of NR use the same or extended parameters as LTE so that the two systems have the basis for coexistence. Uplink alignment of LTE and NR is specified in [19] for orthogonality and radio bearer (RB) avoidance. Meanwhile, the 3 GPP protocol introduces rate matching [20; 21], which further guarantees the reliability of dynamically sharing networks between 5G and 4G. Existing research on spectrum sharing has focused on novel network architectures, physical layers, and high-level issues in spectrum resource management and regulation.