Optics Communications 402 (2017) 52–55
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Optics Communications
journal homepage: www.elsevier.com/locate/optcom
Experimental demonstration of optical MIMO NOMA-VLC with single
carrier transmission
Bangjiang Lin
a,
*, Zabih Ghassemlooy
b
, Xuan Tang
a
, Yiwei Li
a
, Min Zhang
a
a
Quanzhou Institute of Equipment Manufacturing, Haixi Institutes, Chinese Academy of Sciences, Quanzhou, China
b
Optical Communications Research Group, Faculty of Engineering and Environment, Northumbria University, Newcastle, UK
a r t i c l e i n f o
Keywords:
Visible light communications (VLC)
Non-orthogonal multiple access (NOMA)
Multiple inputs multiple outputs (MIMO)
a b s t r a c t
We experimentally demonstrate a non-orthogonal multiple access (NOMA) scheme for optical multiple inputs
multiple outputs (MIMO) visible light communications (VLC) with single carrier transmission and frequency
domain successive interference cancellation, which offers low peak to average power ratio, a good balance
between throughput and fairness, and a higher system capacity for a larger number of users. The MIMO
demultiplexing and the inter-user interference mitigation are realized with efficient channel equalization. The
optimum power allocation ratio is about 0.29 in the case of four users.
© 2017 Elsevier B.V. All rights reserved.
1. Introduction
Light-emitting diode (LED) based visible light communications (VLC)
is an emerging technique of optical wireless communications. Due to its
advantages of low cost, license-free and immunity to the electromag-
netic interference, VLC has been considered as a promising candidate
to complement conventional radio frequency (RF) communications,
especially for short-range indoor applications [1,2]. The ability to serve
multiple access in the physical layer is crucial to optical wireless
networks with multiple VLC transmitters (TXs) and receivers (RXs).
Orthogonal multiple access (OMA) techniques such as time domain
multiple access (TDMA), orthogonal frequency domain multiple access
(OFDMA) and interleaved frequency division multiple access (IFDMA)
have been introduced into VLC [3–6].
Power domain multiple access, also known as non-orthogonal multi-
ple access (NOMA) has recently been proposed as a promising solution
to enhance the spectral efficiency for the 5th generation (5G) wireless
networks [7–9]. Unlike the OMA, NOMA superposes user messages in
the power domain and uses successive interference cancellation (SIC)
at the RXs to separate the users, so that all of the users can use the
whole time–frequency resources. The NOMA scheme offers a better
balance between system fairness and throughput, and improved system
capacity [7–9]. With good feasibility and performance, it has also
been adopted for VLC systems [10–12]. In [13], a phase pre-distortion
method was proposed to improve the symbol error rate performance of
NOMA uplink with SIC decoding in VLC. In [14], we propose a NOMA
*
Corresponding author.
E-mail address: linbangjiang@163.com (B. Lin).
scheme combined with OFDMA for VLC, which offers flexible bandwidth
allocation and a higher system capacity.
In this paper, we propose a NOMA scheme for optical multiple
inputs multiple outputs (MIMO) VLC system with single carrier trans-
mission and frequency-domain (FD)-SIC. Single carrier transmission
can outperform OFDMA in terms of peak to average power ratio
(PAPR), which is critical to VLC system due to the high nonlinearity
of LED [15]. Due to the availability of a large number of LEDs in indoor
environment, the optical MIMO is becoming popular to increase the
data rate for VLC [16–19]. The feasibility of the NOMA MIMO-VLC
with single carrier transmission is verified with experiment demon-
stration. The MIMO demultiplexing and interference cancellation are
simultaneously realized at frequency domain based on time-domain
multiplexing preamble structure. Both intra symbol frequency averaging
(ISFA) and minimum mean square error (MMSE) which offer better
channel estimation [20] are also proposed to eliminate the inter-user
interference more effectively. As shown in the experiment results, the
optimum power allocation ratio (PAR) is about 0.29.
2. Technique principle
Fig. 1 shows the schematic diagram of MIMO NOMA-VLC with 𝑁
users for each TX. In each TX, the source data for each user is mapped
and encoded into quadrature amplitude modulation (QAM) symbol.
Cyclic prefix (CP) and preamble are inserted prior to power allocation,
http://dx.doi.org/10.1016/j.optcom.2017.05.069
Received 24 March 2017; Received in revised form 25 May 2017; Accepted 25 May 2017
0030-4018/© 2017 Elsevier B.V. All rights reserved.