International Conference on Intelligent Control and Computer Application (ICCA 2016)
Research on Distinguishing Technology of Frequency
Hopping Network Signal
Yuan Yuan
Zhiyong Shi
Jianguo Shen
School of Electronic and Information
Engineering
Beihang University
Beijing, China
Luna_369@163.com
College of Communication
Engineering,
Chongqing University
Chongqing, China
szy13@163.com
ChongQing Communicate Institute
of PLA
put forward several methods on reconnaissance of frequency
hopping signal, such as, adaptive and multi channel detection
technology [1], compressed receiver detection technique[2],
digital channelization technology[3], detection technology
combined with compression and channelization[4], maximum
related treatment[5], detection technology under sophisticated
electromagnetic environment[6] and so on. Generally speaking,
the domestic reconnaissance of frequency hopping signal has a
certain research foundation.
Abstract—The technology of extracting network information
parameters from FH Synchronization Orthogonal network signal
distinguishing is proposed in this paper, then its performance is
simulated.
Keywords—FH Communication; Synchronization Orthogonal
Network; Network Distinguish; Network Information Parameters
I.
INTRODUCTION
Frequency hopping communication has strong capacity of
resisting disturbance, good LPI characteristics as well as
strong networking capability, which has been widely used in
modern military communication. Therefore, to actively and
effectively carry out research on frequency hopping
communication reconnaissance is imperative now. At present,
both domestic and overseas countries have made great
progress on the aspect of frequency hopping signal
reconnaissance, for instance, distinguishing issues of medium
and low speed frequency hopping signal reconnaissance and
non-orthogonal network signal have been resolved in a certain
degree[1]. However, there are still many problems of separating
frequency hopping orthogonal network signal need to be
further studied. Due to the application of frequency hopping
network and battlefield integrated frequency hopping
parameter management system, the characteristics of space
frequency hopping signal become more and more complicated
and elusive, which strengthened its LPI performance and
increased the difficulty of net sorting. Based on this, some
researches on distinguishing technology of frequency hopping
network signal will be discussed in this paper.
II.
The traditional distinguishing technology focuses on
completing distinguishing by extracting parameters from
signal frequency, direction, amplitude and other characteristics
of radio frequency or subtle features of signal[7.8.9]. However,
some of those parameters are not reliable due to impact of
environment, some of them are difficult to be extracted, which
result in several limits to these algorithms and concepts. Based
on the literature of [10], this paper puts forward an algorithm
about frequency hopping synchronous orthogonal network
signal distinguishing from the prospective of combining
reconnaissance and counter reconnaissance with a starting
point of using network information parameter of frequency
hopping signal into the distinguishing of synchronous
orthogonal network, the key of implementation is how to
extract network information parameters correctly and reliably.
III.
INTRODUCTION OF DISTINGUISHING ALGORITHM
A. Distinguishing model
Broadba Original
nd
detection
receiver signal
DEVELOPMENT STATUS OF DISTINGUISHING
TECHNOLOGY OF FREQUENCY HOPPING SIGNAL
RECONNAISSANCE
Signal
Frequen
detection
cy
and
hopping
pretreatmen network
t
signal
Separatio
n result
Parameter
extraction
&
integratio
Separatio
n
procedur
e
Result
database
n
To distinguish frequency hopping network signal, it is
necessary to conduct reconnaissance of frequency hopping
signal at first. There are many researches done for frequency
hopping signal in abroad, but there’s a few report about such
aspect due to variety of difficulty or confidentiality. In fact,
some certain researches have also been made in China, which
© 2016. The authors - Published by Atlantis Press
ChongQing, China
cqshenjg@163.com
Network separation
Signal
f
Frequency hopping signal analysis
Baseband
information
Data information
Fig.1. A distinguishing model of frequency hopping synchronous
orthogonal network
278
In order to correctly distinguish frequency hopping signal
from different network by utilizing distinguishing algorithm, it
is necessary to find the position of network information
parameter contained in the signal of each jump at first, this is
not only the primary issue of correct distinguishing of
frequency hopping network, but also the key of distinguishing
algorithm. The probability of correct extraction of network
information parameter provided by such algorithm will
directly influence the final probability of correct
distinguishing, thus, the situation of such algorithm in this part
will decide whether the whole distinguishing algorithm has
superiority or not. This part is also the main content we need
to research.
According to the distinguishing target that need to be
achieved by synchronous orthogonal networking mechanism,
signal characteristics and frequency hopping signal
reconnaissance, the distinguishing model of frequency
hopping synchronous orthogonal networking signal can be
established as shown in Figure 1.
B. Distinguishing algorithm
In literature [5], the basic idea of distinguishing algorithm
is that, distinguishing is achieved by extracting network
information parameters carried by each network signal
according to the different network information parameter
based on different network information carried by all
frequency hopping synchronous orthogonal networking signal.
Signal with same network information belong to the same
frequency hopping network, vice versa. The steps are as
following:
In order to extract this parameter, the position of first and
final bit of correlation code and network number sequence
shall be determined accurately. Specially for the frame
structure of frequency hopping network shown in Table 1, the
connection of correlation code and network number can be
presented by one sequence, for example, Ci(i=1,2,3…)
indicates the correlation code and network number of No.i
network. Regarding several frequency hopping signal captured
at the same time, the correlation code and network number
information can be extracted respectively through analysis and
comparison of baseband information after the demodulation of
several hop signal.
(1) Parameter extraction and integration: Extract network
distinguishing characteristic parameter based on analysis of
basic feature of frequency hopping network signal, and then
make classification, arrangement and integration, so as to form
parameter database that can be directly called by
distinguishing algorithm according to the needs of
distinguishing.
(2) Distinguishing: mainly including two parts:
Supposing the speed, information speed, compression ratio
and channel data speed of a frequency hopping signal is
250H/s, 192kbps, 3:2 and 288kbps respectively, the bit
distribution of its frame structure is shown as Table 1. If there
is no information send during frequency change, then 116 bit
shall be set as “0”, bit synchronous guidance is the
“1010…”code of 100 bit, and the correlation code, network
code and code format are shown as Table 2. The
synchronization/data/deferred-network-entry guidance/service
information is 768 bit random 0/1 sequence, while the
protection bit is 80 bit random 0/1 sequence.
a)Conduct analysis, accumulation, extraction and
integration of parameters by using several hops to generate
distinguishing parameter set.
b)Conduct real-time distinguishing for several signal
occurred simultaneously according to the gradual hop of
distinguishing parameter set.
IV. EXTRACTION OF NETWORK INFORMATION PARAMETER
The network information carried by each network is
important parameter for the distinguishing of network. For
typical frequency hopping synchronous orthogonal network,
the network information is mainly including correlation code,
network number and so on. Correlation code is a group of
special code word used for synchronous maintenance and
timing. Network number is the status symbol of each network
used for network identification, while low speed correlation
code is generally passed through during the usage, so that
ensure the reliability of transmission. These two groups of
parameter will be occurred in synchronous hop, data transfer,
deferred-network-entry guiding hop and service hop signal
when frequency hopping synchronous orthogonal network is
working. One of typical frame structure in frequency hopping
synchronous orthogonal network signal is shown in Table 1.
TABLE I.
Frequency
hopping
116
TABLE II.
Network-1
Network-2
Network-3
Relevan
t code
Network
number
24
64
Synchronizatio
n /Data/
Deferrednetwork-entry
guidance/Servi
ce information
768
Relevant code
096E8F
F69170
F17690
Network number
0001
0010
0011
Code of network number
0:F1EA;1:6F49;
0:6F68; 1:4583;
0:52BD;1:8585;
Take three networks and three hops extraction as an
example,the calculation of X11,X12,X13 with X21,X22,X23
shall be made respectively at first. As there is same frequency
hopping, bit synchronous guidance, correlation code and
network number in the information sequence of same network
signal, the first 304 bit of same network signal information
sequence after calculation without error are all zero, and the
first 216 bit of different network signal information sequence
after calculation are all zero, then, make calculation of
X11,X12,X13 with X31,X32,X33 respectively. Similarly, the
first 216 bit of different network signal information sequence
after calculation are all zero, and the first 304 bit of same
network signal information sequence after calculation without
error are all zero. Due to the influence of data in the front and
back end, redundant bit will be inevitably introduced
accordingly. Assuming the probability of 0 and 1 occurring in
the bit synchronous guidance sequence of front end and
EXTRACTION OF NETWORK INFORMATION PARAMETER
Bit
synch
roniz
ation
Guid
ance
100
FORMAT OF RELEVANT CODE, NETWORK NUMBER AND CODE
Prote
ction
80
279
random sequence of back end is same, the probability of
judging one more bit is 2 (1/2)3=1/4. Take the smallest bit
from Ci sequence of three networks as the bit of such
sequence, then the probability of judging more bit of Ci
sequence from three networks is (1/4)3=1/64.
step5: Take last 12 values from P, use matrix u to make
continuous numbers from those 12 values into a group, and
then put it into a certain line of matrix. The number of lines in
matrix is equal to that of continuous array, compensate all
lines with “0”.
Figure 2(obtained when the error rate is 10-2) provide the
calculation result (first 400 bit) of a certain signal sequence
X11 of the first hop and six information sequences
(X21,X22,X23,X31,X32,X33) within second and third hop of
targeted network signal. From the figure, we can see that, the
information sequence X11,X21,X31 of first and fourth column
data obtained belong to the same frequency hopping network.
step6: Take the line with most “0” from matrix, remove the
largest and smallest value and take average value, i.e. the
position number of last bit of network information parameter
Ci.
step7: Find the position of network information parameter
Ci in the signal of each hop according to the first and last bit
of network information parameter Ci
step8: Take network information parameter Ci from 12
signals in second, third, fourth and firth hop, and then compare
it with network information parameter Ci of 3 signals within
first hop, if the same bit beyond a certain limit, those signals
belong to same network.
step9: Compare the network information parameter Ci of 5
hops signal in same network, make majority decision for
values in same position to obtain the modified network
information parameter Ci of each network and store them.
V. ALGORITHM SIMULATION
Under MATLAB environment, we have made simulation
of extracting network information parameter of 3 frequency
hopping synchronous orthogonal network signals by using
above method. All the parameters in simulation are assumed
as Section 3. Please find the probability of correct extraction
of network information parameter from a certain network
signal under the condition of different error rate.
Fig.2. The calculation result (first 400 bit) of a certain signal sequence of
first hop and six information sequences (X21,X22,X23,X31,X32,X33) within
second and third hop of targeted network signal.
From the above process, we can find the error probability
is relatively big when extract by three hops. If extract from
four hops, similarly, the probability of judging one more bit is
2 (1/2)4=1/8. Take the smallest bit from Ci sequence of three
networks as the bit of such sequence, the probability of
judging one more bit is (1/8)4=1/4096.
From Figure 3, we can see that, extraction of network
information parameter of target network signal from several
frequency hopping synchronous orthogonal networks can be
achieved by using such algorithm through a greater probability
under the condition of worse error respectively. However, the
probability of correct extraction will be decreased with the
increase of error rate. The probability of correct extraction is
higher than 93% if the error rate is less than 1×10-2 , but it will
starts to get worse when the error rate is more than 1×10-2.
Thus, the error probability of extraction by four hops can
be accepted basically. Considering the error code existed in
channel and majority of judgment shall be required for
modifying network information parameter, five hops signal
will be used here for extracting network information. The
steps are as following:
step1: Take 3 signals from the first hop for calculating
with 12 signals within second, third, fourth and fifth hops
respectively to obtain 36 groups of sequences.
step2: Find the first position pi that is not 0 in each group
from 36 sequences, then arrange them in ascending order to
get array P.
step3: Take the first 24 numbers, using a matrix q to
arrange those 24 numbers from small to large to form a group
to place into a certain line of the matrix. The column number
will be depended by how many successive arrays, the number
of matrix column will be depended on the number of such
successive arrays. All columns will be compensate by “0”.
Fig.3. Probability of correct extraction of network information parameter
of certain specified network signal under the condition of different error rate
step4: Take the line with most “0” from matrix, remove the
largest and smallest value and take average value, i.e. the
position number of first bit of network information parameter
Ci.
VI. CONCLUSION
This paper mainly researches the extraction issues of
network information parameter by focusing on frequency
280
[3]
hopping synchronous orthogonal network distinguishing
algorithm, and provides a kind of algorithm of extracting
network information parameter consequently. After verified
by simulation, this algorithm is able to extract network
information parameter of target network within a certain range
of error rate under bad channel, which can supply firm
foundation for the distinguishing of frequency hopping
synchronous orthogonal network signal. However, such
algorithm is only suitable for frequency hopping synchronous
orthogonal network, there are still some limits for the
application in frequency hopping asynchronous orthogonal
network. Thus, it is necessary to further study another
distinguishing algorithm for frequency hopping asynchronous
orthogonal network.
[4]
[5]
[6]
[7]
[8]
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