Demonstration of M-QAM OFDM bidirectional 60/25 GHz transmission over 10 km Fiber, 100 m FSO and 2 m radio seamless heterogeneous fronthaul link
Luis Vallejo, B. Ortega, J. Mora, Dong‐Nhat Nguyen, Carlos Guerra, Jan Bohata, Jan Spáčil, Stanislav Zvánovec
Abstract
In this paper, we demonstrate the experimental transmission of 16- and 64- quadrature amplitude modulation (QAM) Long Term Evolution - Orthogonal Frequency Division Multiplexing (LTE-OFDM) signals by using millimetre wave frequencies at 60 GHz and 25 GHz for downlink and uplink, respectively, over a heterogeneous optical fronthaul infrastructure. A directly modulated laser was employed for both links, which enables the cost-effective full-duplex system proposal. The bidirectional link consists of a 10 km of single mode fiber, a 100 m long free space optics channel and 2 m long wireless radio link, which brings flexibility for future wireless networks. The error vector magnitude (EVM) parameter is measured for a range of the received optical and electrical power as well as the signal-to-noise ratio. A comprehensive estimation of penalty factors in the different network segments is presented. The successful transmission over the whole proposed network with the EVM below the required limit of 9 % for 64-QAM with 20 MHz bandwidth is experimentally demonstrated for the received optical power of −2.7 dBm and −1 dBm for the downlink and uplink, respectively.