Cloud radio access network (C-RAN) is a recent trend of RAN architecture positioned to help the operators to address challenges of new wireless services, such as emerging 4G and 5G mobile networks. C-RAN uses baseband processing units in a central server which connects to the radio front-ends at cell sites via the so-called fronthaul network. The fronthaul infrastructure is currently provided by CPRI (Common Public Radio Interface) and OBSAI (Open Basestation Architecture Initiative) industry standards which use dedicated optical links with high deployment costs. An alternative is to use Ethernet technology aiming to reuse of network infrastructure available in many commercial buildings. However, in contrast to the traditional synchronous fronthaul, Ethernet suffers with packet delay variation (PDV) and challenging synchronization recovery. This work presents a complete and flexible testbed to evaluate Ethernet-based fronthaul. The system is validated via extensive measurements that show the effects of synchronization procedures and network impairments on regenerated clock phase noise.

Resumo-Múltiplas antenas são amplamente utilizadas nos sistemas de comunicação (MIMO). Testbeds de baixo custo que deem suporte à comunicação com MIMO são de interesse tanto para indústria quanto para academia. Rádio definido por software (SDR) é uma tecnologia promissora para prover essa flexibilidade. No entanto, a criação de um testbed MIMO com SDR requer um know-how não trivial e cuja curva de aprendizagem é íngreme. A contribuição deste trabalho é utilizar as tecnologias SDR existentes, descrevendo os problemas e gargalos associados à criação desse testbed. Resultados de medidas de canal também são apresentados e demonstram a implementação do setup MIMO utilizando SDR.

Software defined radio (SDR) is an important tool for communication research nowadays. It allows for better spectrum utilization and leads to smarter communication systems. Besides, due to its flexibility, research groups have been using SDR hardware platforms for quicker implementation of new algorithms and development of products. Therefore, the availability of flexible and relatively low cost platforms has been increasing and can also be explored in the teaching environment. This work describes the GNU Radio platform and presents some GNU Radio scripts for public use in teaching basic and intermediate level aspects of communications systems. The goal of this initiative is to contribute to the telecommunications community with easyto-follow educational material that is made freely available.