Aerospace and Electronic Systems Magazine May 2018 - 34

Feature Article:

DOI. No. 10.1109/MAES.2018.170109

FDA-OFDM for Integrated Navigation, Sensing, and
Communication Systems
He Huang, CETC Key Laboratory of Electromagnetic Domain Operation,
Chengdu, China
Wen-Qin Wang, State Key Laboratory of Complex Electromagnetic Environment
Effects on Electronics and Information System (CEMEE), Luoyang, China

INTRODUCTION
Integrated wireless communications, radar sensing, and smart
navigation is becoming increasingly necessary owing to their
similar finite radio frequency (RF) electromagnetic spectrum resource [1]. By integration of various disciplines, a multitude of
new and more intelligent services, such as smart city and ambient
assistant living, can become available. For instance, using a joint
waveform for both radar and communication applications, the occupied spectrum would be used in a more efficiently way and both
applications could be operated simultaneously. Such an integrated
radar and communication systems has been reported in multiple
papers [2]-[9]. An early example of integrated radar and communication system is the National Aeronautics and Space Administration Space Shuttle Orbiter [10]. Another example is the intelligent
transportation system [11], which allows the intelligent vehicles
to autonomously sense the driving environment and cooperatively
exchange the information data. Furthermore, the proposals for integrating cognitive radar and cognitive radio for efficient spectrum
sharing are also suggested [12]. Many applications would possibly
benefit from the availability of integrated navigation, sensing, and

Authors' current addresses: H. Huang is with the CETC Key
Laboratory of Electromagnetic Domain Operation, Chengdu,
610036, China. W.-Q. Wang is with the State Key Laboratory
of Complex Electromagnetic Environment Effects on Electronics and Information System (CEMEE), Luoyang, China. He is
also with School of Communication and Information Engineering, University of Electronic Science and Technology of
China, Chengdu, 611731, P. R. China, E-mail: (wqwang@uestc.
edu.cn).
This work was supported by National Natural Science Foundation of China under grant 61571081, Young Top-Notch Talent of the National Ten Thousand Talent Program, and Open
Grant of State Key Laboratory of Complex Electromagnetic
Environment Effects on Electronics and Information Systems
(CEMEE) under grant 2017K0203B.
Manuscript received May 31, 2017, revised October 1, 2017,
and ready for publication November 17, 2017.
Review handled by L. Ligthart.
0885/8985/18/$26.00 © 2018 IEEE
34

communications, which advantages can be summarized as follows
[1]: (i) System cost is reduced and resource utilization is improved;
(ii) The advantages of radar, such as high power and strong directivity, can be utilized to improve the communication quality and
increase the effective sensing range; (iii) System automation level
is enhanced.
The main challenge to integrate navigation, sensing, and communications lies in designing suitable waveforms that can be simultaneously employed for information transmission and radar
sensing [13], [14]. Although waveform design has received much
attention, especially in multiple-input multiple-output (MIMO)
radar, waveform design for integrated radar and communications
received relative few attentions. Classical radar sensing waveform
design aims to create the waveforms with optimum radar ambiguity function properties. The most popular waveform fulfilling this
requirement is the chirp waveform, also called "linearly frequency
modulated (LFM) signal". An intuitive approach for designing a
radar sensing and wireless communications integrated waveform
is to use chirp modulation to encode the data [15], but it achieves
low communication symbol rate corresponding to the chirp rate
only. In [16], different Oppermann sequences are employed for the
radar and communication applications, respectively. These two sequences have to be separated first in the receiver before subsequent
signal processing. In [17], another radar and communication integrated scheme by modulating frequency modulated continuouswave waveform with amplitude shift keying is adopted, but it has
poor peak-to-average power ratio (PAPR) performance due to the
employment of amplitude modulation. In contrast, a typical communication waveform with good auto-correlation properties is the
spread spectrum sequence, but it is not suitable for radar applications due to its small time-bandwidth product and low frequency
efficiency [18].
Orthogonal frequency division multiplexing (OFDM) is a
popular choice for integrated radar and communication waveform
because it offers many advantages such as robustness against multipath fading and relative simple synchronization. Time and frequency synchronization is crucial in OFDM communications to
preserve subcarrier orthogonality. For radar, however, sensitivity
to synchronization is beneficial since radar uses a stored version
of the transmitted signal to measure the time-delay and frequency

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