Performance analysis of non-line-of-sight ultraviolet
communication through turbulence channel
Tao Liu (刘 涛), Peng Wang (王 鹏), and Hongming Zhang (张洪明)*
State Key Laboratory on Integrated Optoelectronics, Tsinghua National Laboratory for Information Science and
Technology; Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
*Corresponding author: zhhm@tsinghua.edu.cn
Received November 17, 2014; accepted January 28, 2015; posted online March 25, 2015
The bit error rate performance of non-line-of-sight ultraviolet communication through atmospheric turbulence is
studied. The communication performance degradation under different strengths of turbulence is evaluated.
Particularly, under strong turbulence conditions, the communication distance can be shortened by 30%, or
at a given distance the communication rate can be reduced by half than the counterpart of no turbulence.
OCIS codes: 060.2605, 060.4510.
doi: 10.3788/COL201513.040601.
Free space optical communication, with wavelengths
ranging from the infrared to UV has attracted consider-
able attention
[1–3]
. Compared with wireless communica-
tion, the advantages of optical communication lies in
the huge unlicensed spectrum, low-power, miniaturized
transceivers, and high security
[4,5]
. The motivation for
using UV technology lies in: first, atmospheric scattering
of UV radiation by molecules and aerosols provides a
mechanism for establishing a non-line-of-sight (NLOS)
communication link
[6–9]
. The NLOS link characteristic
relaxed the acquisition, tracking, and pointing (ATP) re-
quirement, greatly reducing the complexity of the commu-
nication system. Second, the strong ozone absorption of
UV radiation in the upper atmosphere making the solar
noise in the UV band is very low. In the end, recent devel-
opment in UV transmitters and UV photomultiplier tube
(PMT) detectors, and emerging requirements from the
military and other applications have led to increasing in-
terest in NLOS UV communication.
In the late 2000s, a series of experiments and theoret ical
analysis about LED-based NLOS UV communication
were conducted
[10–12]
. However, these studies were confined
to short range communica tion (below 100 m), and greatly
limited its practical application.
To increase the communication distance, high-power
UV-LED modules are used to increase the transmitter
power. In the mean time, a high sensitivity PMT and wide
field-of-view (FOV) receiver are used to improve the
signal-to-noise ratio (SNR). In UV NLOS communication ,
on-off-keying (OOK) and pulse position modulation
(PPM) are two commonly used modulation methods.
Although OOK modulation and demodulation is relatively
simple, PPMs have better flexibility and performance
[12]
.
In our research 4-PPM is used as the modulation method.
For short range NLOS communication, the impact of
atmospheric turbulence is ignored. As the range increases
to hundreds of meters, the impact of turbulence on the
performance of NLOS communication must be considered.
In this Letter, the performance degradation of long range
NLOS UV communication through a turbulence channel
is studied, the bit error rate (BERs) are calculated and
checked by Monte-Carol simulation under different
baseline distances, different bit rates and different
transmitter/receiver. The results and conclusions ac-
quired in this Letter can be used to predict the achievable
communication performance as a function of system and
atmospheric parameters, and serve as the basis for the
system design.
A typical single-scattered NLOS communication sche-
matic diagram is illustrated
[6]
, as shown in Fig. 1. The
beam full-width divergence angle of the transmitter
(T
x
) is denoted by ϕ
1
and the FOV angle of the receiver
(R
x
) is denoted by ϕ
2
. The T
x
and R
x
pitch angles are
denoted by θ
1
and θ
2
, respectively. The baseline distance
is denoted by r and the distances of the intersected
volume V to the T
x
and R
x
are denoted by r
1
and r
2
,
respectively.
From the communication point of view, scattering
and absorption are two kinds of dominant interactions
between photons and the atmosphere. Under the homo-
geneous atmosphere assumption, the total scattering by
molecules and aerosols is defined as k
s
¼ k
ray
s
þ k
mie
s
, where
k
ray
s
and k
mie
s
are Rayleigh and Mie scattering coefficients,
respectively. The extinction coefficient is defined as
k
e
¼ k
s
þ k
a
, where k
a
is the absorption coefficient. The
Fig. 1. Typical NLOS UV communication schematic diagram.
COL 13(4), 040601(2015) CHINESE OPTICS LETTERS April 10, 2015
1671-7694/2015/040601(5) 040601-1 © 2015 Chinese Optics Letters