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2016
Journal Article
Titel
Robust optical wireless link for the backhaul and fronthaul of small radio cells
Abstract
This paper summarizes recent work on the use of optical wireless links as a robust outdoor backhaul solution for small radio cells, such as WiFi, LTE and 5G, over distances between 20 and 200 m. Results of a 5-month outdoor field trial in Berlin, Germany, indicate that the visibility range was never below 180 m, with more than 1 km in 99% of all times during this period. Rate-adaptive transmission proved to improve the availability remarkably in the occasional presence of fog or sunlight. A mathematical model of the backhaul link including these impairments is presented and implemented to obtain an optimized link design. A prototype was realized, accordingly, using low-cost optoelectronic components and a 1 Gb/s baseband chipset. Gross data rates of 800, 500, and 225 Mb/s have been achieved in real-time operation over 20, 100, and 215 m outdoor link distance, respectively, with 2 ms latency at 95% load. Finally, we discuss further evolution towards 5G mobile networks.