Investigation of White Rabbit based Frequency Synchronisation for Distributed MIMO Testbed

Sammanfattning

The demand for better networks and faster speeds within telecommunications has been an ever-growing ambition for the last decade. A promising candidate for dealing with this demand is distributed multiple-input multiple-output (D- MIMO) systems that combine large-scale antenna arrays and decentralized node architectures. However, evaluating the possibilities and limitations of such system requires real-time testbeds. This thesis investigates White Rabbit as a potential alternative for synchro- nization in the Lund University Large Intelligent Surface (LuLIS) testbed. The testbed is a scalable field programmable gate array (FPGA) based testbed with 16 distributed AMD Zynq UltraScale+ ZCU216 nodes that can operate up to 256 antennas. The testbed currently achieves frequency synchronization by distribut- ing an external reference clock over coaxial cables. Although effective over short distances, this becomes increasingly difficult as the node separation grows. An alternative is White Rabbit, which is an open-source synchronization technology that achieves sub-nanosecond time synchronization via fiber-optic communication over large distances. A White Rabbit node was developed and integrated on the AMD Zynq Ultra- Scale+ ZCU216 evaluation board. The implemented design is evaluated in terms of synchronization accuracy and frequency stability. The results shows that White Rabbits presents a highly stable frequency stability, while remaining within the cyclic prefix. Therefore, posing as a scalable and viable solution for replacing traditional coaxial cables in a distributed wireless communication system.