[Paper Review] A Centralized SDN Architecture for the 5G Cellular Network

Akshatha M. Nayak, Pranav Jha+1 more|arXiv (Cornell University)|Jan 2, 2018

Software-Defined Networks and 5G1 references3 citations

TL;DR

This paper proposes a centralized SDN architecture for 5G cellular networks by relocating the RRC and RRM control functions from gNBs to the core network, transforming gNBs into pure data plane nodes. This reduces signaling overhead, cuts registration and handover times by up to 29%, and improves system throughput through centralized mobility management with load-aware handover decisions.

ABSTRACT

In order to meet the increasing demands of high data rate and low latency cellular broadband applications, plans are underway to roll out the Fifth Generation (5G) cellular wireless system by the year 2020. This paper proposes a novel method for adapting the Third Generation Partnership Project (3GPP)'s 5G architecture to the principles of Software Defined Networking (SDN). We propose to have centralized network functions in the 5G network core to control the network, end-to-end. This is achieved by relocating the control functionality present in the 5G Radio Access Network (RAN) to the network core, resulting in the conversion of the base station known as the gNB into a pure data plane node. This brings about a significant reduction in signaling costs between the RAN and the core network. It also results in improved system performance. The merits of our proposal have been illustrated by evaluating the Key Performance Indicators (KPIs) of the 5G network, such as network attach (registration) time and handover time. We have also demonstrated improvements in attach time and system throughput due to the use of centralized algorithms for mobility management with the help of ns-3 simulations.

Motivation & Objective

• Address the growing complexity and signaling overhead in 5G networks due to increasing data demand and diverse device requirements.
• Reduce control plane signaling and latency in 5G by centralizing RRC and RRM functions in the core network.
• Improve system performance through centralized, network-wide visibility for mobility management decisions.
• Demonstrate the feasibility and benefits of SDN principles in 5G RAN using ns-3 simulations and KPI analysis.
• Compare the proposed architecture with the 3GPP-defined 5G architecture to quantify improvements in latency and throughput.

Proposed method

• Relocate the RRC protocol layer and Radio Resource Management (RRM) functions from gNBs to the core network, transforming gNBs into pure data plane nodes.
• Eliminate the NG-AP signaling interface by removing RRC from the gNB, reducing processing and encoding/decoding overhead.
• Implement a centralized control function in the core network (eAMF) with a global view of network state, including load and signal strength.
• Use a centralized algorithm for mobility management that combines RSRP and eNB load information to make optimal handover decisions.
• Simulate the proposed and 3GPP architectures using ns-3 LENA module with realistic parameters, including path loss models and user mobility.
• Measure key performance indicators such as attach time, registration time, handover time, and system throughput under varying load and mobility conditions.

Experimental results

Research questions

• RQ1 How does centralizing RRC and RRM functions in the 5G core network affect signaling overhead and control plane latency?
• RQ2 To what extent does centralized mobility management improve system throughput compared to distributed algorithms in a dynamic network?
• RQ3 What is the reduction in registration and handover times achieved by moving RRC from gNB to the core network?
• RQ4 How does the proposed architecture compare to the 3GPP-defined 5G architecture in terms of signaling cost and processing efficiency?
• RQ5 Can centralized SDN-based control improve network performance under high mobility and load variation scenarios?

Key findings

• Registration time is reduced by 12% to 28% in the proposed architecture, from 74–84 ms to 60 ms, compared to the 3GPP 5G architecture.
• Handover time is reduced by 29.29%, from 78.5 ms to 55.5 ms, due to elimination of RRC signaling and faster decision-making in the core.
• Attach time is reduced by 10% in simulations, from 3.23 ms to 2.94 ms, due to reduced processing and encoding/decoding overhead.
• System throughput improves monotonically with the number of handovers when using centralized load-aware handover algorithms, outperforming traditional distributed A3-based RSRP algorithms.
• The centralized architecture reduces signaling failure scenarios, such as handover failures, by enabling more accurate and coordinated decision-making.
• The performance gains are robust even when accounting for air interface and simulation abstraction effects, as relative improvements remain consistent.