Abstract
In the modern wireless networks, millimeter-wave radio-frequency (RF) bands are becoming more attractive as they provide larger bandwidth and higher data rates than the today-used systems operating at frequencies below 6 GHz. In addition, according to the fact that coaxial cables exhibit extremely high attenuation for millimeter-wave RF signals, analog radio over fiber techniques (RoF) form a promising technology for delivering unaltered radio waveform to a remote antenna. This paper experimentally analyzes three types of RoF modulations, namely a directly modulated laser, an electro-absorption modulator, and a Mach-Zehnder Modulator. The primary focus is on the implementation of each RoF transmitter in an RoF system, such as those in 5G networks. The experimental study includes a detailed characterization of an RoF system with a 50-m long outdoor free-space RF channel operating in the frequency band of 25 GHz. Frequency response (S-parameters) and third-order nonlinear distortion are investigated in detail. Tests of EVM performance were conducted using an orthogonal frequency division multiplexing signal modulated with 16-quadrature amplitude modulation (16-QAM) with a long-term evolution signal. It is demonstrated that the transmitters studied can operate under a 13.5% EVM limit given for 16-QAM. Apart from the detailed system performance, the considerable power fluctuations in the 25 GHz free-space RF outdoor channel are reported.
Highlights
Global data traffic in wireless networks is increasing exponentially, mainly due to video applications and high-resolution streaming, and it is expected that about 75% of the 69 Exabytes of total worldwide mobile data traffic will be used for video by 2022 [1]
The best system performance has been achieved by using Transmitter A and Transmitter C
The mean error vector magnitude (EVM) for the aforementioned transmitters was below 8.5% over the entire tested 4 GHz bandwidth window, giving reasonable margin for the 16-quadrature amplitude modulation (16-QAM) requirement of
Summary
Global data traffic in wireless networks is increasing exponentially, mainly due to video applications and high-resolution streaming, and it is expected that about 75% of the 69 Exabytes of total worldwide mobile data traffic will be used for video by 2022 [1]. This demand is driving the rapid evolution of wireless technology and incorporates higher frequency bands than those used today to offer significantly greater bandwidth, which is of particular importance for the 5th generation (5G) mobile networks. A comprehensive review of mm-wave frequency RoF systems was provided in [10]
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