Real-time Emulation Methodologies for Centralized Radio Access Networks

This work considers radio-network emulators for testing Centralized Radio Access Network (C-RAN) elements using a frequency-domain functional split (so-called split 7-1). The techniques are applicable to fourth and fifth generation cellular systems. They allow system validation and performance evaluation of base station or Distributed Unit (DU) equipment using a synthetic radio network instead of actual radio units. Also, they can be employed for testing during the development phase in a software-only environment or as real-time traffic stimulus for performance evaluation of not only the physical layer but also layer 2 procedures (e.g. MAC scheduling). Specifically, we propose real-time emulation methodologies built on top of the OpenAirInterface (OAI) platform employing general-purpose processors and fast Ethernet transport ports. We discuss software functions optimizations to emulate the multipath channel, enabling synthetic network scalability through frequency-domain processing and avoiding the need for abstraction models of the physical layer. Even though the IP-based synthetic network can accommodate 1-3 Radio Remote Units (RRUs) and up to 3 User Equipment (UEs) to work in real-time, it supports higher non-real-time scenarios. It can be parallelized on high-end multi-core computers to scale up to higher bandwidth and more UEs. Our proposal exhibits an improvement of one order of magnitude on generic x86 computers related to the average computation time of the multipath channel, compared to the existing time domain approach in downlink and uplink transmissions.