2010 NDIA GROUND VEHICLE SYSTEMS ENGINEERING AND TECHNOLOGY SYMPOSIUM
VEHICLE ELECTRONICS AND ARCHITECTURE MINI-SYMPOSIUM
AUGUST 17-19 DEARBORN, MICHIGAN
MOBILE, SECURED COMMUNICATIONS ENABLE NET-CENTRIC
OPERATIONS
Dr. Amish A. Mehta Andrew Cambridge
Vice President, Engineering Chief Scientist
Ultra Electronics Ultra Electronics
Measurement Systems Inc. Communications & Integrated
Wallingford, CT Systems
Greenford, UK
Brian Gardner
Technical Director
Ultra Electronics Communications & Integrated Systems
Greenford, UK
ABSTRACT
The demand for mobile, secure communications has been and will continue to be a fundamental
requirement for dismounted, urban and distributed operations in the field. It is imperative that soldiers on the
front lines receive actionable information in a timely, secured and uninterrupted manner to increase force
protection and effectiveness. In this paper, we describe a novel, high technical maturity (TRL 8+)
communications link that offers the mounted and dismounted soldier secure, beyond line of sight, encrypted
capability for weapons control and command & control of multiple platforms. An innovative spread spectrum
waveform was designed from the ground up to deliver necessary functionality for reliable communications
amongst multiple nodes with a data rate and range commensurate with battlefield scenarios.
INTRODUCTION several key requirements for unmanned platforms in the
Knowledge is survival on the battlefield; knowing the modern battlefield: a) low latency for direct command
location of friendly soldiers, enemies and the overall
surroundings is paramount for dismounted, urban and
distributed operations. The key to obtaining and maintaining
this necessary knowledge is the ability to send and receive
communications and have reliable situation awareness while
in motion on land, in the air or at sea ([1,5]). The result is
battlefield superiority through the ability to securely
communicate via voice, video and data from any location
while maintaining force maneuverability.
With the decreasing availability of the RF spectrum, it is
critical to multi-task with any communications link. Reviews
of existing data links and radios as well as interviews with
Users identified several gaps in both performance and
functionality for the unmanned scenarios faced in the
battlefield. The User community is interested in addressing Figure 1: Desired Command & Control Data Link Concept
Proceedings of the 2010 Ground Vehicle Systems Engineering and Technology Symposium (GVSETS)
and control, b) low probability of intercept (LPI), c) low variable rates can be made available) and integrity according
probability of detection (LPD), d) possible use of non- to application requirements.
contiguous spectrum, e) long range implementation and f)
Beyond Line of Sight (BLOS) networking capabilities. Waveform Description
The HIDL waveform is a variant of Orthogonal Frequency
It is important to note that “standard or traditional” data Division Multiplexing (OFDM) ([2 - 4]) in which signaling
links implement methods of modulation (e.g., QPSK, is simultaneously achieved on multiple parallel frequencies.
OFDM) in which the symbol structure is inherently visible OFDM is the technology behind Asymmetric Digital
and potentially, the synchronization structure is visible as Subscriber Line Broadband (ADSL), WiFi, and 4th
well. This presents a problem because interceptors could generation mobile phones.
easily read the signals and hence jammers could jam the
signal by simply attacking the identified synchronization. In With OFDM, a large number of parallel frequencies are each
addition, most secured radios today tend to implement simultaneously modulated, with separate data at a low
frequency hopping methods that can also be tracked and symbol rate, to achieve a high aggregate data rate. As a
intercepted. consequence of the low rate on each carrier, OFDM can be
made highly resistant to multipath, in which not only does a
The innovative, high maturity (TRL 8+) High Integrity Data radio receive the intended signal, but also the reflections of it
Link (HIDL) was developed to satisfy these challenging, a short time later. Traditional modulation schemes,
unique requirements of unmanned platforms operating in especially when working at high data rates, pose challenges
multi-path, cluttered environments. in multipath mitigation whereas OFDM has a natural
robustness against this type of degradation.
HIGH INTEGRITY DATA LINK (HIDL) The variant of OFDM used for the HIDL waveform
The HIDL incorporates low probability of intercept (LPI), incorporates an innovative spread spectrum scheme that
low probability of detection (LPD), jam resistance ensures a noise-like appearance in both the time and
technology and multipath immunity to ensure that command frequency domains as shown in Figures 2 and 3. This is
& control (C2) functionality is not compromised in the critical because it allows the radio’s spectrum to be precisely
battlefield. The external user interface is Ethernet, thus tailored for efficient exploitation of available resources and
allowing the data link to be connected to standard processors
for ease of use.
The innovative waveform employed by HIDL supports a
network of nodes and implements a Time Division Multiple
Access (TDMA) scheme; each node transmits on assigned
timeslots and receives data on all other timeslots. In this Figure 2: Typical Waveform over a Timeslot
schema, individual nodes may be given an allocation aligned
with its functionality; for example, passive nodes may spend thereby reduces the spectral density making the signal
most of their time “listening” while those needing to difficult to detect. The spreading and overlapping pulse
transmit larger amounts of data can be given the majority of structure allow the waveform to, in essence, self interfere.
timeslots. Since the timeslots are naturally separated in time, An enemy will not know the spreading code and therefore
this allows us to form simple networks that can relay various will not be able to recover the symbols because the symbol
configurations for BLOS operations. This is an advantage and synchronization structures are not evident in the signal.
over conventional frequency division approaches since no In addition, the mapping from bits to symbols is highly
“backwards radios” are required at the relay nodes and the randomized.
same radio can be used for all nodes.
By maintaining a certain level of spreading, the benefits of
Timeslots in the HIDL TDMA scheme are of short duration spread spectrum are thus assured including anti-jam, LPI
that enable end-to-end low-latency; of paramount (due to hidden symbols) and LPD (due to noise-like
importance when setting up stable loops for real-time control features).
applications. The HIDL waveform provides the user
significant adaptability when implemented on a Software
Defined Radio (SDR). For example, it is possible to
simultaneously trade off spectrum usage, data rate (e.g.,
Mobile, Secured Communications Enable Net-Centric Operations, Mehta et al.
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Proceedings of the 2010 Ground Vehicle Systems Engineering and Technology Symposium (GVSETS)
proportion to the amount of spreading and thus the signal
becomes disguised by natural noise in the system. The
receiver, exploiting knowledge of the precise spreading
function used by the transmitter, can reject the noise and de-
spread the signal to recover the original data. In addition to
providing a waveform with low probability of detection and
interception, spreading also gives the system anti-jam
properties.
Figure 3: Spreading for Anti-Jam and LPI
The implementation of the HIDL waveform provides
significant flexibility in timeslot allocation with asymmetric
The User data has Forward Error Correction (FEC) applied
allocations possible thus allowing different data rates in
thus enabling good Bite Error Rate (BER) performance.
different directions. Relay capability can be naturally
Supplementing the spread spectrum is a pseudo-random
configured and the amount of spectrum used can be tailored
interleaving and randomization operation applied to the FEC
to the mission’s requirements.
data prior to transmission. This not only protects against
burst errors in the propagation channel, but also guards
Implementing various encryption mechanisms, the system
against unintended interception of the data.
provides INFOSEC (Information Security), TRANSEC
(Transmission Security) and COMSEC (Communication
There are several desirable waveform properties of HIDL:
Security) for mobile operations. The inherent low latency
a) one hundred (100) timeslots available for allocation
allows for rapid response to information and independence
between transmitters thus allowing for different data rates
from GPS measurements, and thus, immunity to standard
for different platforms and relay capabilities; b) bandwidth
GPS jamming methods. The innovative HIDL waveform
between 1 and 20MHz can be allocated as desired to tailor
addresses the need for secure, reliable communications for
implementation for high data rates (e.g., video), maximum
battlefield command & control applications.
range or multi-user environments (e.g., use of non-
contiguous frequencies); c) range up to 200nM (e.g., antenna
and bandwidth dependent) and d) data rates > 5Mbps.
REFERENCES
Encryption [1] J. Moore, “Blazing trials, dropping bread crumbs”,
Overall system security, implementing the HIDL waveform, Defense Systems, 2007.
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Blowfish) or addressed via additional modules to 1998.
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the option of transmitting Encapsulated Security Payload Value Decomposition”, IEEE Trans. Communications,
(ESP) packets either in transport or tunnel modes as 1998.
necessary.
[4] H. Minn et al., “A robust timing and frequency
SUMMARY synchronization for OFDM systems”, IEEE Trans on
The HIDL system is based on a new NATO Command and Wireless Communications, 2003.
Control standard (STANAG 4660 [6]) for interoperable C2 [5] M. Lawlor, “Network-Centric Operations Go on the
data links and uses an innovative multi-carrier, noise-like Road”, SIGNAL Magazine, 2005.
waveform. [6] “STANAG 4660 Interoperable Command and Control
Data Link (IC2DL)”, Naval UAS Newsletter, 2007.
Implementing spread spectrum technology, the power
spectral density of the resultant signal is reduced in
Mobile, Secured Communications Enable Net-Centric Operations, Mehta et al.
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