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.

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