Towards connecting base stations over metro gigabit ethernets

Deployment of Gigabit Ethernets in metropolitan areas creates new opportunities to save costs by converging data and telephone services. The primary question of our study is whether emerging metropolitan networks can meet the QoS requirements necessary to connect GSM and UMTS base stations. These requirements on delay, jitter, and loss are significantly more stringent than the ones for VoIP and have to be met at the presence of bursty cross traffic. Therefore, we have probed ETH's campus network which spans the metropolitan area of Zurich with traffic comparable to encapsulated E1 traffic from base stations and have measured perceived QoS. Our findings show that the campus network generally meets the QoS requirements. However, the perceived QoS degrades with increasing network utilization.To further investigate the impact of the configuration of Ethernet switches on perceived QoS, we have conducted a simulation study. The results show that the perceived QoS is better when switch buffers are limited to small sizes of 1 MB compared to setups where the number of frames in the buffer is limited. From these results we infer that metropolitan Gigabit Ethernets are well suited for connecting GSM and UMTS base stations.