Design and Implementation of SMARTHO -- A Network Initiated Handover mechanism in NG-RAN, on P4-based Xilinx NetFPGA switches

Abstract

This report deals with the design of handover schemes for radio access networks (RAN) in 5G networks, using programmable data plane switches. The network architecture is expected to be a centralized cloud infrastructure, connected via a backhaul network to many edge-computing clouds that are closer to the end-user. Some of the network services can be implemented in edge devices to improve network performance.In 5G networks, the C-RAN architecture splits the Base Band Unit (BBU) into Central and Distributed Units (CU and DU). This structure has created a mid-haul Network, connecting CUs and DUs. The mid-haul network has created a dataplane challenge that does not exist in traditional distributed RANs -the need for efficient connections between the CUs and DUs. Traditional encapsulation techniques can be used to transport packets across the CU and DU. However, the recent advancements in dataplane programmability can be used to enhance the system performance. In this report, we show how P4 switches can be used to parse the packets between DU, CU, and Back Haul (Core Network) for potential system improvements. In particular, we consider the scenario of mobile handover, that arises when a user moves between different cells in the mobile network. The proposed protocol is called SMARTHO, illustrating a smart handover.Programming Protocol-Independent Packet Processors (P4) is a programming language designed to support specification and programming the forwarding plane behavior of network switches/routers. With P4 switches, the protocol designer can define customized packet headers, parsing of headers, and defining new match-action routines. In SMARTHO, we use P4 Switches to intervene in the handover process for fixed-path mobile users. Such users could be those in a train, drones, devices with high-degree of predictable mobility, etc. A resource pre-allocation scheme that reserves resources before the UE reaches a future cell, is proposed. The solution is implemented using a P4-based switch introduced between the CU and the DU. The P4 switch is used to spoof the behavior of User Equipment (UE) and perform the resource allocation in advance. This is expected to reduce the handover time as the user moves along its path.The proposed SMARTHO framework is implemented in the mininet emulation environment and in a reconfigurable hardware environment using NetFPGA-SUME boards. For Mininet based simulation, we used virtual hosts connected using P4 switches, using the P4 behavior model (P4BMv2) software switch. User and control traffic is also generated to simulate the mobile traffic and measure the HO performance. User traffic is represented using ICMP ping packets over a tag. The results show a handover response time improvement of 18% for a tandem of two HOs and 25% for a tandem of three HOs. For testbed implementation, we used