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SIGNAL-CODE CONSTRUCTS AND PROCESSING ALGORITHM WITH AUTOMATIC DISPERSION DISTORTION COMPENSATION FOR WIDEBAND HF COMMUNICATION
DOI 10.24411/2072-8735-2018-10240
Nikolay A. Kandaurov,
MTUCI, Moscow, Russia, „ . . , , . . • „u
' Keywords: signal-code constructs, ionosphere,
kandaurov@srdmtucLru dispersion distortion, HF communication, wideband.
HF communication is a backup form of communication, especially in demand in emergencies in remote areas. Basically it is necessary to send short text messages, but over long distances. The disadvantage is the dependence of the quality of radio communications in different frequency ranges on the state of the ionosphere and the workload of the decameter range by powerful broadcasting stations. The solution to the problem is the use of wideband noise-like signals and complex signalcode constructs. When using wideband signals in HF communication, frequency dispersion has a significant effect on the signal. The article deals with the tasks of developing new signal-code constructs for a wideband HF communication and an algorithm for processing them with a dispersion distortion compensator. At present, the actual task is to expand the bandwidth of the signals used. One of the problems arising from this is the dispersion distortion of wideband signals in the ionospheric channel, which lead to a decrease in reception quality. Signal-code constructions based on non-linear pseudo-random sequences and non-binary error-correcting code NB-LDPC are proposed. Simulation is carried out to assess noise immunity, taking into account dispersion distortion. An algorithm and a device for its implementation for automatic compensation of dispersion distortion are proposed. The simulation results with compensation are given. The proposed algorithm and results can be used to increase the frequency band of the used HF communication.
Information about author:
Nikolay A. Kandaurov, minor researcher at SRD MTUCI, Moscow, Russia
Для цитирования:
Кандауров Н.А. Сигнально-кодовые конструкции и алгоритм их обработки с автоматической компенсацией дисперсионных искажений для широкополосной декаметровой связи // T-Comm: Телекоммуникации и транспорт. 2019. Том 13. №2. С. 76-79.
For citation:
Kandaurov N.A. (2019). Signal-code constructs and processing algorithm with automatic dispersion distortion compensation for wideband HF communication. T-Comm, vol. 13, no.2, pр. 76-79.
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introduction
The t'arth's ionosphere is a medium of propagation of radio waves of various ranges. for which the pha.se pan of iht- transfer function depend* on frequency. Thus, dm: to the frequency dispersion. separate parts of the wideband signal have different propagation delays. Tiiis difference leads to a synchronization error and affects the quality of information reception. To improve the quality of reception of information, it is necessary to evaluate and compensate the frequency dispersion. In articles 11-41 il is shown (hat losses due to dispersion distortion reach 7 dfi a! a signal bandwidth of 400 kit/. Thus, it is necessary to evaluate and compensate for the dispersion distortion of broadband signals. In methods for estimating dispersion distortions without the use of an ionospheric probe arc presented. One of the main drawbacks of conventional decameter radio communications is the wide availability of infbtm$iion transmitted, due To the possibility of receiving radio signals re Heeled from The ionosphere over large areas of the entire globe, iird. consequently. problems in ensuring the confidentiality of information Transmitted. A pressing problem is the development of a signal -eode constructs for a wideband radio Jink of IIK communication with compensation for dispersion distortion and an increase in energy and structural secrecy.
E'roecss hkin for DSSS with dispersion distortion.
When using signal-code constructions based on direct spectrum expansion, it is important to find the optimal combination between different parameters, namely, the speed of the error-correcting code, the character width, the length of the expanding sequence. At the satne time, when used in the ionospheric channel, it is important to find the moment when the expansion of the signal spectrum will give a gam Compared to dispersive distortions.
The value lor the aggregate process gain fur !)SSS fl, taking inlo account the relative speed of error-Correcting coding number of bils in a character Hi, length of the expanding PN sequence y and a smoothing filter parameter [1 in the form:
,.JLitl,«
r m-r "
l + p
(1)
Kind [he expression lor the optimal process gain lor [)SSS taking inlo account the dispersion distortion. To do this, we express the signal-to-noise ratio in the band of the received useful signal through the normalized ratio oi'lhe energy of the transmitted symbol to the spectral power density of noise:
I
R
E R...
[l+fi)
<2}
E
In (2), the relationship between the signal bandwidth ut a level of -3 dli, the symbol rate R , and the filter .snUHithini; factor is taken into account /7 . Taking into account the digit character of the transmitted symbol and the relative speed of the error-correcting coding, one can write Es =m r-Eh .
Then
Where does il come from:
Il-h.
% B
(3)
(4)
w here the value of process gain lor DSSS is given by the expression (I}. Next, we take into account that, with the same average transmitter radiation power, and hence ihe average signal power in the reception hand (with constant average signal propagation conditions), the ratio of the symbol energy to the spectral power density of the noise may vary depending on the le\el of dispersion distortions. Equivalent energy losses due to dispersion distortion were calculated in ¡1and the energy loss coefficient w as
introduced K'{p). Multiply and divide (3) by, then
P. E,K-{P)
mr
W 1
N..
iS)
K a,
w here E,, (p) = EbK2{ p) energy accumulated with losses, and
B =
_NjUß)K\p)
(6)
ttir
equivalent process gain for i)SSS. Rewrite <6| in the form
B _ V^ + PWi^m ^Q + DKMy.A/ )
m*r
H. mr
where x is the slope of the dispersion characteristic, is the signal bandwidth.
figure 1 shows the dependence of the equivalent process gait) for DSSS on the w 1J1I1 of the spectrum for various values of the slope of the dispersion characteristic. As you can see, the optimum width of the signal spectrum is about 2i0 U1/ for the slopes of the dispersion characteristic from 60 lo SO ps/MI 1/, w-ith further spectrum expansion gain from spectrum expansion.
46
-1-1
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4240 3a 3a 31
l- 10 u VMM!
»Hirt!Hi I -iOn^Mhi
UUiivUKl 1 iOpV^Hz
i-lOOuVfH:
:oa im ™ J» mo ™ ™ ra see 1000
i'tpur4f I. Values of equivalent pnocesi fain for i)SSS tbr di fie rent slopes of the dispersion chrogterisilc
T-Comm Vol.13. #2-2019
T
New signal-cudc constructs.
Under the signal-code constructs relcrs to the connection of the error-correcting coder with the modulator, This requires the coordina Li on of the volume of the ensemble ni signals with the width of the code symbol. Signal-code constructs are considered in [i. 6]. In order to increase energy secrecy and I o solve the problem of bund load, it is proposed to use wideband signals with spread spectrum direct sequence technology.
Thus, a pseudo-random sequence (PKS) ensemble is required lo form a signal ensemble. Sequences must have good correlation properties. Namely, lo have a clear peak of the autocorrelation function of the ACT and Imv emissions of the side peaks of the CCF mutual correlation function, h is proposed 10 use sequences obtained by XOR sequences of de Hruijn and Gold. This class of sequences is described in |7|.
With a sequence length of XI92 hits, the peaks of I he CCF side peaks do not exceed 10%. In the role of the error-correcting code, it is proposed to use a non-binary low-density parity-check code (NBLDPC) code speed of 2/7, The scheme of the formation of the signa I-code construct is presented in Figure 2,
ensemble Nl'RS, in - is the width of the code symbol (the number of bits in the code word). To assess the noise immunity of various variants of signal-code const ructions, simulation modeling was pcrlbrmcd in a two-beam channel with dispersion distortion. The slope of [lie dispersion characteristic is j = SO psMi Signals with a bandwidth of 300 to S DO kllz were used. Speed of error-correcting coding r = 2 / 7 , itutnbcr of bits in a character m = 1.
As can be seen from (lie lieurc, signals with a 300 kHz band have ihe greatest rîojse immunity, due to the smaller influent*: of dispersion distortion. To use signals with a wider frequency band, it is proposed to use a dispersion distortion compensator.
Estimation ami compensation of dispersion distortion
lie fore compensating for dispersion distortion, it is necessary to estimate the slope of the dispersion characteristic s. For evaluation, it is proposed to use the maximum likelihood method described tn [3], A compensation of dispersion distortion implemented on the basis of the Kahnan filter. This method is described in [Kl.
DrtiKxra ftiMWf
m hi
îhip«
t HXadtr
1 "V
1 , CO*
WK
1 - J
Chmift) hfftí
/
a-eoAt
V
Figure 2, Scheme of Ibrmatmn of a new sifrml-code construct
-•- (in JEW liHz
* (7/7 ft- «0 kHi
ft- tfit
T (i-7 : ■ MWkHi
higiirt' 3.Thc noise i m muni [y plots of the SCC taking into account (he dispersion distortion
The stream o fin formation bits is divided into m-hit characters, cticodcd by a non-binaTy error-correcting code with a low density of parity cheeks. Then cacti received code symbol is assigned its own NI'RS,
Tiiis means thai each code symbol from the Galois field GF (2nl) is assigned its own NPRS. Thus a necessary condition is the combination ofthe size of the ensemble with the bit depth of lEic noise-resistant code; this mentis that the size of I he M'RS ensemble should be equal to: Q = 2" where Q is the size of the
I- ¡liar e -I. Wideband siemf reception scheme with dispersion distortion compensation
Figure 4 shows a scheme for receiving a wideband signal with dispersion-compensated distortion compensation. After the receiver, quadrature digital samples are fed to the input of the pre-fiItering and interference rejection module. Then the digitized samples are coming to a ray detector containsng a bank of matched filters with initial values of the slope of the dispersion characteristic s. Also digitized samples go to the multiplier with the reference I5SSS. After muttiplication enters the integrator and the storage-sampiing device fSSD). After that, they arc go to the decision device fl^li) lor the block for adjusting the slope of tile dispersion characteristic s and to the dccoder.
As can be seen from Figure 5, the signal-code construct with a signal hand of RtHl kl!/ has the best noise immunity, thanks to the compensation of dispersion distortion. When using this option. you can conduct reception at the signa!-to-noise ratio ¡11 the band to - tin in us J 36 dli.
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Kcfertnccs
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4.1 vano V tJ.V. (2006). Methods ami mathematical models for study of fhe propagation of decameter camptet ¡¡gnats and correction Us dispersion distortions. MarSTU, Yoshkar-Ola. (in Russian)
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5. Kandaurov MA, Lobov ГЛ1.. Lobo va Г-О. (2018). Optimal tollo wing compensator dispersion J i sum ion s of broadband signais, Eloi trosiyu?. 201 S. No. 3. pp. 34-j S- (/я Rtissiatl)
СИГНАЛЬНО-КОДОВЫЕ КОНСТРУКЦИИ И АЛГОРИТМ ИХ ОБРАБОТКИ С АВТОМАТИЧЕСКОЙ КОМПЕНСАЦИЕЙ ДИСПЕРСИОННЫХ ИСКАЖЕНИЙ ДЛЯ ШИРОКОПОЛОСНОЙ ДЕКАМЕТРОВОЙ СВЯЗИ
Кандауров Николай Александрович, МТУСИ, Москва, Россия, [email protected]
Аннотация
Рассматриваются задачи разработки новых сигнально-кодовых конструкций для широкополосной декаметровой радиолинии и алгоритма их обработки с компенсатором дисперсионных искажений. В настоящее время актуальной является задача расширения ширины полосы частот используемых сигналов. Одной из проблем, возникающей при этом, являются дисперсионные искажения широкополосных сигналов в ионосферном канале, которые приводят к снижению качества приема. Предлагается сигнально-кодовые конструкции на основе нелинейных псевдослучайных последовательностей и недвоичного помехоустойчивого кода NB-LDPC. Производится имитационное моделирование для оценки помехоустойчивости с учетом дисперсионных искажений. Предлагается алгоритм и устройство его реализации для автоматической компенсации дисперсионных искажений. Приводятся результаты моделирования с компенсацией. Предложенный алгоритм и результаты могут быть использованы для увеличения полосы частот используемых радиолиний в декаметровом диапазоне.
Ключевые слова: сигнально-кодовые конструкции, ионосфера, дисперсионные искажения, декаметровая связь, широкополосные сигналы. Литература
1. Лобов Е.М., Кандауров Н.А., Косилов И.С., Елсуков Б.А. Качество обнаружения широкополосных сигналов в условиях дисперсионных искажений в ионосферной радиолинии II Системы синхронизации, формирования и обработки сигналов. 20iS.
2. Лобов Е.М., Кандауров Н.А., Косилов И.С., Елсуков Б.А. Методика оценки параметров частотной дисперсии ионосферного канала с помощью широкополосного фазоманипулированного сигнала II T-Comm: Телекоммуникации и транспорт. № 9. 20i4. С. 49-S3.
3. Kandaurov N.A., Lobov E.M., Smerdova E.O., Kosilov I.S., Elsukov B.A. Optimum estimation and filtering of the ionospheric channel dispersion characteristics slope algorithms II 20i7 Systems of Signal Synchronization, Generating and Processing in Telecommunications, SINKHROINFO-2017 20i7. С. 7997S37.
4. Иванов Д.В. Методы и математические модели исследования распространения в ионосфере сложных декаметровых сигналов и коррекция их дисперсионных искажений. Йошкар-Ола: МарГУ, 2006. 266 с.
5. Чиров Д.С., Лобов Е.М. Выбор сигнально-кодовой конструкции для командно-телеметрической линии радиосвязи с беспилотными летательными аппаратами средней и большой дальности II T-Comm: Телекоммуникации и транспорт. 20i7. Т. i i. № i0. С. 2i-28.
6. Назаров Л.Е., Шишкин П.В. Алгоритмы некогерентного приема сигнально-кодовых конструкций на основе блоковых турбо-кодов II Журнал Радиоэлектроники №7, 20i2
7. Кандауров Н.А., Голубев Е.А., Лобов Е.М., Шубин Д.Н. Новый класс двоичных псевдослучайных последовательностей с нелинейным алгоритмом формирования для систем связи с кодовым разделением абонентов в II T-Comm: Телекоммуникации и транспорт. 20i8. Том i2. №2. С. 76-80.
8. Кандауров Н.А., Лобов Е.М., Лобова Е.О. Оптимальный следящий компенсатор дисперсионных искажений широкополосных сигналов II Электросвязь. 20i8. №S. С. 34-38.
Информация об авторе:
Кандауров Николай Александрович, м.н.с., Московский технический университет связи и информатики, Москва, Россия
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Pifn. dB
Fifturf S. Noise immunity curves [akin с into account dispersion distortion compensation
Conclusion
Tile proposed signal-Code eon struct ions und the reception algorithm with compensation of dispersion distortions allow expanding the bunds of the used hmadhand signals in Iff communication. Compensation of dispersion distortion makes it possible to conduct recepLion at low levels of the signal-to-noisc ratio, which increases the energy secrecy.
