Next-generation access/mobile networks have set high standards in terms of providing wireless services at high data rates in order to keep up with the vast demands for other mobility and multiple services. Wireless-optical broadband access network (WOBAN) technology, also known as fibre-wireless (FiWi), has uncovered incredible opportunities for the future of next-generation networks because it gets the best of both domains: huge bandwidth provided by the optical fibre and high ubiquity of the wireless domain. The objective of FiWi networks is to integrate the high data rate and long reach provided by optical networks and the ubiquity and mobility of wireless networks, with the target to decrease their expense and complexity. Multiple-input–multiple-output (MIMO) is an inevitable technique for most of the new mobile/wireless networks that are driven by the huge data rates required by today’s users. Consequently, to construct any FiWi system for next-generation (NG) access/broadband networks, a MIMO technique has to be considered. This article presents a comprehensive, contemporary review of the latest subsystems, architectures and integrated technologies of MIMO wireless signals backhauling using optical fibre or fibre access networks, such as passive optical networks (PONs). An overview for FiWi, PONs and MIMO wireless systems is provided. In addition, advanced techniques of accommodating the MIMO wireless signals over optical fibre are explained and compared. Different types of wireless MIMO signals over fibre, such as 5G, WiFi and related transport technologies, are reviewed. Moreover, future research trends are also discussed.

1. Introdcution

With the increasing number of smartphones and their broadband demanded applications [1], there is a huge need for high  bandwidth broadband infrastructure. Moreover, the rapidly growing demands on bandwidth and end users’ new data rates consuming applications such as YouTube, Netflix, peer-to-peer downloading and cloud computing, call for the combination of the fibre and wireless domains in a unified infrastructure. FiWi networks merge wireless networks with optical networks. The wireless networks have the availability, flexibility and coverage, while optical networks support transmission speeds and overcome distance limitations [2]. FiWi systems have started to draw in broad research enthusiasm as they offer great potential for tackling the issues of high-speed Internet access “over the last mile”. Specifically, FiWi systems with a passive optical network (PON) as the optical system have been seriously concentrated in the previous years as a PON can give high
transmission bit rates for today’s bandwidth killing applications [2]. One of the best schemes to deliver the wireless signals over optical fibre is radio-over-fibre  (RoF) [3]. The RoF technique has shown a promising solution for the future of mobile and access networks because of its seamless integration of the large capacity provided by the optical fibre and the flexibility, mobility and freedom of radio systems [4] and, as such, RoF has become an appealing answer for the high data rate demands and overall cost reduction of wireless systems [5]. MIMO is a foreseeable technique for most of the new mobile/wireless networks that are driven by the huge data rate required by today’s users [6]. The MIMO technique is intended to enhance transmission distance, data rate and reliability compared to the performance offered by a single-input single-output (SISO) system [7,8]. Consequently, in order to build any FiWi system to provide wireless connectivity for next generation (NG) broadband networks, the MIMO technique has to be considered [9]. In this paper, we present a comprehensive, contemporary review of the latest subsystems, architectures and integrated technologies of MIMO wireless signals backhauling using optical fibre or fibre access networks, such as passive optical networks (PONs). Sections 2–4 introduce PONs, FiWi and MIMO wireless systems, respectively, with the basic technologies and concepts enabling these systems and networks. Section 5 addresses more specific topics in wireless MIMO signals over  fibre techniques. Section 6 focuses on more specific technologies for the transport of different types of     wireless MIMO signals over fibre. Integrated technologies and backhauling of MIMO wireless signals over PONs are reviewed in Section 7, Section 8, suggests future work and, finally, the conclusion is
presented in Section 9.

This entry is adapted from the peer-reviewed paper 10.3390/electronics9122014