Software-defined Communication Platform Implementation on Commodity Hardware

Abstract

Radio access networks face increasingly diversified and strict demands from applications. The diverse needs of users cannot be satisfied by a single approach. Networks must evolve into flexible platforms offering per-user service customized to the needs of each application. Meeting the increased coverage and capacity demands of applications also requires network densification. Mobile network operators are confronted with the need to improve their service offerings while keeping the capital and operational expenditure of densified networks under control. Expanding the network using traditional base station designs presents cost and interference challenges. Introducing a functional split between central and distributed units enables better co-ordination and cheaper distributed units situated closer to cell sites. This thesis contributes to software-based soft—real-time radio access networks (RAN) implementation using commodity hardware. Techniques are presented for implementing software-defined radio nodes effectively. The overall aim is to exploit the benefits of commodity hardware while mitigating the challenges caused by its focus on throughput and polyvalency over low latency and determinism. This work details an architecture for decoupling the communication protocol code from the underlying platform. The approach used is to hide and recover from deadline misses instead of being overly conservative in an effort to provide guarantees. The benefits afforded by increased flexibility in the RAN outweigh occasional lost data due to deadline overruns. The strict requirements on latency imposed by the time domain structure of air interface protocol creates challenges for power management. A method for latency-aware power management is proposed to help solve this. Building on the above, this thesis also investigates disaggregated multi-node RAN implementations. Dividing RAN functionality into physically separate nodes introduces additional latency. The midhaul linking these nodes together becomes an important factor of performance analysis. The research in this thesis presents models for characterizing the behaviour of the midhaul. Models provide tools to assess which functional splits are suitable for a particular scenario. The validity of the techniques and models presented in this thesis are verified through the use of testbeds. Prototype implementations show the viability of building soft—real-time software-based RANs on commodity hardware. The feasibility of midhaul-based disaggregated designs is demonstrated through the use of user equipment positioning as a test application. The results obtained show soft—real-time commodity hardware designs can enable novel RAN architectures.