Industry Perspective

Discusses enhanced mobile broadband (eMBB) requirements for standardized 5G mobile communication new radio services (NR). 3GPP has recently announced the first specifications for 5G NR development toward ITU “IMT for 2020 and Beyond. The significant milestone sets the stage for the global cellular industry to start full-scale development, delivering 5G technology for commercial deployments as early as 2019. This first 5G specification was completed as part of 3GPP Release 15, providing a non-standalone (NSA) 5G architecture for the so called enhanced Mobile BroadBand (eMBB) use-case with target peak data rates of 20 Gbps and user plane latency of 4 ms. However, during the Release 15 NR Study Item phase, several companies identified TCP performance bottlenecks that are exacerbated by design choices made for NR. TCP remains the pre-eminent transport layer protocol today and has also been adapted for new applications such as immersive streaming, data center, and augmented/virtual reality (AR/ VR) that require high data rates combined with very low latency. Given that overwhelming popularity of TCP, a situation unlikely to change in the near future, it is important to consider the performance of TCP over NR to ensure that 5G NR based networks can deliver promised NR data rates to end users. In this column, we begin with a brief introduction to 5G technology concepts related to TCP. Then we provide an introduction of TCP congestion control. Finally, we present the technical issues of TCP associated with the development of 5G NR and present some ns-3 simulation results.