# Evaluation of the Digital Data Performance Transmission on a Fiber-Radio System
## 1 Introduction  
Advances in communication technologies have revolutionized the distribution and transmission of several services such as radio, HDTV, telephony, and the Internet, in an ever faster and more efficient way. Furthermore, a combination of technologies such as optical and wireless allows users to exploit the inherent advantages of each one of these technologies. In particular, fiber-radio technology uses optical fiber to transport signals to be radiated to multiple users using antennas [1]. On the one hand, the large bandwidth, immunity to electromagnetic interference (EMI), and low attenuation of the optical fiber are used in an advantageous manner [2]. On the other hand, the wireless transmission provides absolute mobility to users without the need for a connection terminal [3]. Figure 1 shows a basic fiber-radio scheme where the data are transmitted from a central site (CS) through an optical link to the remote radio unit (RRU). The wireless medium (atmosphere) is mainly affected by fading channels, AWGN [4], and co-channel interference [5], among other impairments.  
Several applications of fiber-radio schemes are reported in the literature. For instance, in [6], an all-optical link with double spectral-efficient transmission and compensation of chromatic dispersion-induced power fading is proposed and demonstrated experimentally. In [7], a system for the transmission of energy through an optical fiber is proposed. In [8], the functionality of a fiber-radio scheme with different simultaneous transmission frequencies using a digital multiplexer for the selection of frequencies and channels is demonstrated. In [9], a fiber-radio scheme is characterized where a microwave signal provided by a receiving antenna is supplied to an optical modulator. In [10], a hybrid scheme with a fiber-to-the-home (FTTH) system combined with a mobile wireless application system usinga double optical modulator and two different signals (in RF and baseband) is proposed. Finally, in [11], a fiber-radio scheme is used for the transmission of an analog TV signal through an optical link using a radiating cable for its wireless emission.  
From the paragraphs above, the goal of this work is to evaluate the digital data performance transmission for a fiber-radio system. This evaluation is supported by a set of numerical simulations. For this task, the VPI Photonics software [12] takes the following into account: 1. a transmission of a digital signal at a bit rate of 2.4 GHz through an optical link of 25 km of SM-SF; 2. an optical external modulation scheme, and; 3. a dispersive channel. Whereas MATLAB software is utilized to emulate a wireless environment taking into account: 1. an urban scenario; 2. a user in movement displacing within a coverage cell of 500 m radius that corresponds to the maximum distance from the wireless receiver to the base station (BS), and; 3. a QPSK strategy format as well as four effects such as multipath and slow fading, co-channel interference, and AWGN. The performance evaluation of this proposal is evaluated taking account of the parameters of SINR and BER statistical tests. In summary, the main novelty of this work lies in the evaluation of fiber-radio systems at simulation level, finding potential applications in cellular telephony, the IoT, or any other mobile system. The rest of this document is organized as follows: Section 2 describes in detail the main concepts for the optical and wireless transmission arrangements; Section 3 shows the results of the numerical simulations carried out for the optical and wireless schemes; and finally, Section 4 summarizes the main conclusions of this work.