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1

Enhanced mitigation of nonlinearity signal distortion by hybrid optical compensation technique

Kareem Ali Hayder Abdul, Murdas Ibrahim A.

Przegląd Elektrotechniczny

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2023

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R. 99, nr 8

231--236

EN

This work investigates and proposes a method for mitigating the negative effects of nonlinearities in the fiber with dense wave division multiplexing transmission systems by combining the optical phase conjugation (OPC) approach with a Raman amplifier. The OPC technique uses a polarization diversity loop configuration to suppress the original input signal. As a result, phase conjugated idlers can be generated across a wide frequency range without introducing any spectral inefficiencies due to wavelength shifts. Idle waves are created by mixing four waves in nonlinear fibers with pump waves that are out of band and orthogonally polarized. Finally, the OPC subsystem is put to use in transmission experiments spanning 800 km over dispersion managed fiber spans with lumped amplification by Improved Raman amplifiers to reduce the effects of fiber nonlinearity caused by mid-link spectrum inversion or multiple links. Simulated results of a 50 GHz channel spacing and a 1.792 Tbps made up of eight 224 Gbps polarization division multiplexed (PDM) sixteen ary quadrature amplitude modulation (DP-16QAM) subchannels reveals a Q-factor improvement of up to ~3 dB in mid OPC compared to ~3.37 dB in multiple OPC in the absence of a backward Raman amplifier. In addition, using the OPC would result in an approximate of 10-6 improvement in BER compared to the conventional method. Furthermore, the average enhancement in error vector magnitude (EVM) for the DWDM situation would be larger than 15% with the inclusion of hybrid OPC with backward Raman amplifier.

PL

Ta praca bada i proponuje metodę łagodzenia negatywnych skutków nieliniowości we włóknie za pomocą systemów transmisyjnych z multipleksowaniem z gęstym podziałem fali poprzez połączenie podejścia optycznej koniugacji fazy (OPC) ze wzmacniaczem Ramana. Technika OPC wykorzystuje konfigurację pętli różnorodności polaryzacji do tłumienia oryginalnego sygnału wejściowego. W rezultacie sprzężone fazowo koła pasowe mogą być generowane w szerokim zakresie częstotliwości bez wprowadzania jakichkolwiek nieefektywności widmowych z powodu przesunięć długości fali. Fale jałowe są tworzone przez zmieszanie czterech fal we włóknach nieliniowych z falami pompy, które są poza pasmem i spolaryzowane ortogonalnie. Wreszcie, podsystem OPC jest wykorzystywany w eksperymentach z transmisją na dystansie 800 km na światłowodach zarządzanych dyspersyjnie ze wzmocnieniem skupionym przez ulepszone wzmacniacze ramanowskie w celu zmniejszenia skutków nieliniowości światłowodów spowodowanej odwróceniem widma łącza środkowego lub wieloma łączami. Symulowane wyniki odstępu międzykanałowego 50 GHz i przepustowości 1,792 Tb/s składającej się z ośmiu 224 Gb/s zmultipleksowanych z podziałem polaryzacji (PDM) szesnastu podkanałów kwadraturowej modulacji amplitudy (DP-16QAM) ujawniają poprawę współczynnika Q do ~3 dB w średnim OPC w porównaniu do ~ 3,37 dB w wielu OPC przy braku wstecznego wzmacniacza Ramana. Ponadto użycie OPC spowodowałoby poprawę BER w przybliżeniu o 10-6 w porównaniu z metodą konwencjonalną. Co więcej, średnie zwiększenie wielkości wektora błędu (EVM) dla sytuacji DWDM byłoby większe niż 15% przy uwzględnieniu hybrydowego OPC z wstecznym wzmacniaczem ramanowskim.

2

Design and performance evaluation of vehicular visible light communication system under different weather conditions and system parameters

El-Mokadem Eslam S., Tawfik Nagwan I., Aly Moustafa H., El-Deeb Walid S.

Opto-Electronics Review

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2023

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Vol. 31, No. 2

art. no. e145580

EN

Vehicular visible light communication is an emerging technology that allows wireless communication between vehicles or between vehicles and infrastructure. In this paper, a vehicular visible light communication system is designed using a non-return to zero on-off keying modulation scheme under the effect of different weather conditions such as clear, haze, and fog. The first model is a light emitting diode-based system and the second is a laser diode-based system. For both models, the influence of system parameters such as beam divergence, transceiver aperture diameters, and receiver responsivity is studied. The impact of the use of the trans-impedance amplifier is also investigated for both models. It was concluded that in the presence of the amplifier, output power of the light emitting diode and laser diode model are increased by 98.46 μW and 0.4719 W, respectively. The performance of the two proposed models is evaluated through bit error rate, quality factor, eye diagram, and output power to have some insightful results about the quality of service for the two proposed models. Under a specific weather condition, the performance of the system would be critical and other techniques should be applied. The maximum achievable link distance for the laser-based and light-emitting diode-based systems is 190 m at a data rate of 25 Gbps and 80 m at a data rate of 60 kbps, respectively, under the same system parameters and weather conditions. The obtained results provide a full idea about the availability of constructing our proposed model in a practical environment, showing a higher performance of the laser diode-based model than that of the light emitting diode-based model.

3

Feasibility study of using various optical filters in conjunction with indoor visible light communication system

Fadhil Hilal A., Alattar Feras Hasson, Fadil Tariq Adnan

Optica Applicata

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2023

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Vol. 53, nr 4

511--522

EN

In modern telecommunication engineering, visible light communication (VLC) is developing a competitive advantage over the traditional RF data communication model since it uses light to transmit data. Optical filters play an important role in optical communication systems to enhance the transmission rate of bit-error rate (BER), especially as a result of noisy environments. We investigate the VLC signal performance induced by four types of filters, including Bessel, Gaussian, rectangular, and trapezoidal filters. The BER is considered an important aspect of improving optical system performance, as it indicates less crosstalk and fewer interferences within the system and is analyzed using eye diagram opening penalties. In our simulation results, the Gaussian filter performs best among these four types of filters. In this paper, a VLC indoor model is developed and simulated using an eye diagram, a bit error rate, and a transmission distance for the proposed model. The results from this study show significant improvements of Gaussian filter over other optical filters for next-generation optical networking systems, the overall BER of a Gaussian filter-based indoor VLC system is less than 9.6×10–15, when the bandwidth of the optical filter is 5 nm at the quality factor of 14 dB.

4

Evaluation of a high-speed hybrid OAM-OFDM-MDM multiplexed coherent FSO system under desert conditions

Sinha Shivaji, Kumar Chakresh

Optica Applicata

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2023

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Vol. 53, nr 3

431--445

EN

To meet the needs of future wireless optical networks, this paper introduces a high-speed, hybrid multiplexed, coherent free-space optical (FSO) communication system that integrates an orbital angular momentum (OAM) multiplexed signal with an orthogonal frequency division multiplexing (OFDM) technique. Two independent QAM polarized beams, each carrying in-phase and quadrature (I/Q) phase 16-QAM-OFDM modulated data, are combined using mode division multiplexing (MDM) to increase the capacity of the proposed system. The reason of choosing OFDM is its capability to support higher data rate, and mitigating intersymbol interference (ISI). The signal is detected using a coherent detection-based digital signal processing (DSP) algorithm at the receiver end. The proposed hybrid FSO system is evaluated in low and heavy dust environments using bit error rate (BER), link distance, optical signal-to-noise ratio (OSNR), and received optical power performance matrices. The simulation results demonstrate the successful transmission of a 120 Gb/s single carrier over the longest link ranges of 1.5 and 0.40 km, respectively, under low and heavy dust weather environments below the signal degradation threshold value (forward error correction (FEC) limit) of BER 2.2 × 10–3 in strong turbulent conditions.

5

Hybrid PAPR reduction schemes for different OFDM-based VLC systems

El-Ganiny Mohamed Y., Khalaf Ashraf A. M., Hussein Aziza I., Hamed Hesham F. A.

Opto-Electronics Review

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2022

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Vol. 30, No. 3

art. no. e141951

EN

Orthogonal frequency division multiplexing has been widely used in many radio frequency wireless communication standards as a preferable multicarrier modulation scheme. The modulated signals of a conventional orthogonal frequency division multiplexing system are complex and bipolar. In intensity-modulated direct detection optical wireless communications, transmitted signals should be real and unipolar due to non-coherent emissions of an optical light emitting diode. In this paper, different hybrid optical systems have been proposed to satisfy real and unipolar signals. Peak-to-average power ratio is one of the biggest challenges for orthogonal frequency division multiplexing-based visible light communications. They are based on a combination of non-linear companding techniques with spreading or precoding techniques. Simulation evaluation is performed under direct current-biased optical orthogonal frequency division multiplexing, asymmetrically clipped optical orthogonal frequency division multiplexing, and Flip-orthogonal frequency division multiplexing systems in terms of peak-to-average power ratio, bit error rate, and spectral efficiency. The proposed schemes are investigated to determine a scheme with a low peak-to-average power ratio and an acceptable bit error rate. MATLABTM software has been successfully used to show the validity of the proposed schemes.

6

PAPR reduction using a combination between precoding and non-liner companding techniques for ACO-OFDM-based VLC systems

Mohammed Nazmi A., Elnabawy M. M., Khalaf Ashraf A. M.

Opto-Electronics Review

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2021

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Vol. 29, No. 2

59--70

EN

Peak-to-average power ratio reduction techniques for visible light communication broadcasting systems are designed, simulated, and evaluated in this work. The proposed techniques are based on merging non-linear companding techniques with precoding techniques. This work aims to nominate an optimum novel scheme combining the low peak-to-average power ratio with the acceptable bit error rate performance. Asymmetrically clipped optical orthogonal frequency division multiplexing with the low peak-to-average power ratio performance becomes more attractive to real-life visible light communication applications due to non-linearity elimination. The proposed schemes are compared and an optimum choice is nominated. Comparing the presented work and related literature reviews for peak-to-average power ratio reduction techniques are held to ensure the proposed schemes validity and effectiveness.

7

Performance Analysis of Filtered OFDM Based Downlink and Uplink NOMA System over Nakagami-m Fading Channel

Mukhtar Shaika, Begh Gh. Rasool

Journal of Telecommunications and Information Technology

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2021

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nr 2

11--23

EN

Efficient consumption of available resources and fulfillment of increasing demands are the two main challenges which are addressed by exploring advanced multiple access schemes along with efficient modulation techniques. To this end, non-orthogonal multiple access (NOMA) is discussed as a promising scheme for future 5G traffic. NOMA enables the users to share same resource block, permitting certain level of interference. In this paper, we propose filtered OFDM (F-OFDM) as a transmission waveform for NOMA systems, as it offers all the advantages of OFDM with the additional provision of sub-band filtering to satisfy the diverse services of the users. We examine F-OFDM in both downlink and uplink NOMA systems. Error-related performances of both downlink and uplink F-OFDM NOMA systems are analyzed and compared with conventional OFDM NOMA system over Nakagami-m fading channel. The results show that the error performance of F-OFDM NOMA is better than that of OFDM NOMA. An improvement of about 2 dB and 1 dB in bit error rate is achieved in downlink and uplink F-OFDM NOMA, respectively. Monte Carlo simulations are conducted for different values of fading parameter m, supporting the obtained analytical results.

8

Investigation of Different Transfer Functions for Optical Limiting Amplifier used in a 2R Burst Mode Optical Regenerator

Deodhar Yash, Reddy Jeeru Jaya Sankar, Kakade Priyanka Desai, Kakade Rohan

International Journal of Electronics and Telecommunications

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2021

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Vol. 67, No. 3

409--416

EN

The major difference between a continuous mode optical regenerator (CMOR) and a burst mode optical regenerator (BMOR) is that a BMOR is capable of handling large variations in the input power which makes it useful in optical packet switched and optical burst switched networks. This is due to the optical limiting amplifier (OLA) present in the BMOR. Using computer modelling, the impact of using different OLA non-linear transfer functions on the output bit error rate of a system consisting of a cascade of 2R BMORs has been investigated. The effect of amplified spontaneous emission (ASE) noise introduced in the inter-regenerator links has also been taken into consideration. Also, a brief review of existing OLA designs is presented.

9

Comparative BER Analysis of Free Space Optical System Using Wavelength Diversity over Exponentiated Weibull Channel

Shah Dhaval, Joshi Hardik, Kothari Dilipkumar

International Journal of Electronics and Telecommunications

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2021

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Vol. 67, No. 4

665--672

EN

Atmospheric turbulence is considered as major threat to Free Space Optical (FSO) communication as it causes irradiance and phase fluctuations of the transmitted signal which degrade the performance of FSO system. Wavelength diversity is one of the techniques to mitigate these effects. In this paper, the wavelength diversity technique is applied to FSO system to improve the performance under different turbulence conditions which are modeled using Exponentiated Weibull (EW) channel. In this technique, the data was communicated through 1.55 µm, 1.31 µm, and 0.85 µm carrier wavelengths. Optimal Combining (OC) scheme has been considered to receive the signals at receiver. Mathematical equation for average BER is derived for wavelength diversity based FSO system. Results are obtained for the different link length under different turbulence conditions. The obtained average BER results for different turbulence conditions characterized by EW channel is compared with the published result of average BER for different turbulence which is presented by classical channel model. A comparative BER analysis shows that maximum advantage of wavelength diversity technique is obtained when different turbulence conditions are modeled by EW channel.

10

Pilot symbol error re-orthogonalization in 2×2 mimo systems of wireless communication

Romanuke Vadim

Scientific Journal of Polish Naval Academy

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2020

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R. 61 nr 3 (222)

43--67

EN

A 2×2 MIMO wireless communication system with channel estimation is simulated, in which two transmit, and two receive antennas are employed. The orthogonal pilot signal approach is used for the channel estimation, where the Hadamard sequences are used for piloting. Data are modulated by coherent binary phase-shift keying, whereupon an orthogonal space-time block coding subsystem encodes information symbols by using the Alamouti code. Based on the simulation, it is ascertained a possibility to decrease the bit-error rate by substituting the Hadamard sequences for the sequences having irregular structures, and constituting the eight known orthogonal bases. Considering a de-orthogonalization caused by two any pilot sequence symbol errors, the bit-error rate is decreased by almost 2.9 %. If de-orthogonalizations are caused by two repeated indefinite, and definite pilot sequence symbol errors, the decrements are almost 16 % and 10 %, respectively. Whichever sequences are used for piloting, the 2×2 MIMO system is ascertained to be resistant to the de-orthogonalization if the frame is of 128 to 256 symbols piloted with 32 to 64 symbols, respectively.

PL

W pracy przedstawiono symulowany system komunikacji bezprzewodowej 2×2 MIMO z oszacowaniem kanału, składający się z dwóch anten nadawczych i dwóch anten odbiorczych. W procesie szacowania kanału zastosowano podejście ortogonalnego sygnału pilotującego z wykorzystaniem sekwencji Hadamarda. Na potrzeby badań symulacyjnych przyjęto modulowanie danych za pośrednictwem spójnego binarnego kluczowania z przesunięciem fazowym, podczas gdy ortogonalny podsystem kodowania bloków czasoprzestrzennych odpowiedzialny był za kodowanie informacji z wykorzystaniem kodu Alamouti. Na podstawie symulacji ustalono możliwość zmniejszenia współczynnika błędnych bitów przez zastąpienie sekwencji Hadamarda sekwencjami należącymi do ośmiu znanych baz ortogonalnych i charakteryzującymi się nieregularnymi strukturami. W przypadku deortogonalizacji wynikającej z dwóch dowolnych błędów symboli sekwencji pilotujących, współczynnik ten został zmniejszony o prawie 2.9 %. Jeśli deortogonalizacje są spowodowane przez dwa powtarzające się błędy symboli sekwencji pilotujących, nieokreślone i określone błędy uległy zmniejszeniu o odpowiednio 10 % i 16 %. Bez względu na to, które sekwencje zostały użyte do pilotowania, wykazano odporność systemu 2×2 MIMO na deortogonalizację w przypadku, gdy ramka zawierała od 128 do 256 symboli, a rozmiar sekwencji pilotującej mieścił się w zakresie od 32 do 64 symboli.

11

Doppler Effect in 2 × 2 to 4 × 4 MIMO systems of wireless communication with orthogonal pilot channel estimation

Romanuke Vadim

Scientific Journal of Polish Naval Academy

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2020

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R. 61 nr 4 (223)

5--20

EN

The Doppler effect in 2×2, 3×3, 4×4 MIMO wireless communication systems with channel estimation is studied. The orthogonal pilot signal approach is used for the channel estimation, where the Hadamard sequences are used for piloting, along with the eight alternative orthogonal sets similar to the Walsh set. MIMO transmissions are simulated for 10 cases of the frame length and pilot symbols per frame by no Doppler shift to 1100 Hz Doppler shift with a step of 100 Hz. Based on the simulation, it is ascertained that MIMO transmissions of shorter frames are less sensitive to the Doppler effect. Despite increasing the number of antennas does not mitigate the Doppler effect, and the bit-error rate performance of 4×4 MIMO systems worsens faster than that of 2×2 MIMO systems, it is better to use the maximum number of antennas. The Doppler effect does badly worsen the performance at highway and express train speeds (100 km/hr, and faster), leaving only possibility to further shorten transmissions. This, however, decreases the data rate, but the respective accuracy-versus-data-rate tradeoff must be acceptable.

PL

W pracy przedstawiono badania efektu Dopplera w systemach komunikacji bezprzewodowej 2×2, 3×3, 4×4 MIMO z estymacją kanału. W procesie szacowania kanału zastosowano podejście sygnału pilotującego w wykorzystaniem sekwencji Hadamarda, wraz z ośmioma alternatywnymi zestawami baz ortogonalnych, podobnymi do zestawu Walsha. Transmisje MIMO zostały zasymulowane dla 10 przypadków, różniących się długością ramki i symboli pilotujących oraz częstotliwością Dopplera, której zakres zmieniał się od 0 do 1100 Hz z krokiem 100 Hz. Na podstawie badań symulacyjnych wykazano, że transmisje krótszych ramek MIMO są mniej wrażliwe na efekt Dopplera. Pomimo, że zwiększenie liczby anten nie zmniejsza efektu Dopplera, a wydajność współczynnika błędnych bitów w systemach 4×4 MIMO pogarsza się szybciej niż w systemach 2×2 MIMO, przeprowadzone badania wskazują na korzyści z zastosowania większej ilości anten. Efekt Dopplera znacznie pogarsza jakość transmisji przy prędkościach powyżej 100 km/h (ruch samochodów na autostradach lub pociągów ekspresowych), determinując potrzebę redukcji przesyłanych danych. To jednak zmniejsza szybkość transmisji danych, ale odpowiedni kompromis między dokładnością a szybkością przesyłania danych musi być akceptowalny.

12

Dimming control schemes combining IEEE 802.15.7 and SC-LPPM modulation schemes with an adaptive M-QAM OFDM for indoor LOS VLC systems

Mohammed Nazmi A., Badawi Kareem A., Khalaf Ashraf A. M., El-Rabaie El-Sayed

Opto-Electronics Review

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2020

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Vol. 28, No. 4

203--212

EN

The presented work proposes a new dimming control schemes for indoor visible light communication which combines variable pulse-position modulation, colour shift keying as key schemes of IEEE 802.15.7 standard, and sub carrier-pulse-position modulation as a pulse-position modulation variant with orthogonal frequency division multiplexing. These schemes are then compared with traditional merging schemes utilizing pulse-width modulation and multiple pulse-position modulation with m-ary quadrature amplitude modulation OFDM. The proposed schemes are investigated in a typical room with a different lighting layout (i.e., distinctive and uniform lighting layout), followed by an illumination investigation to evaluate the performance of the proposed schemes, especially the enhanced achieved data rates, and to determine their limitations as reliable visible light communication systems that can satisfy both communication and illumination requirements.

13

Implementation of C-PolSK Modulation in FSO Network and Analysis of its Atmospheric Performance

Chattopadhyay Diptangshu, Bharti Manisha

Journal of Telecommunications and Information Technology

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2019

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nr 4

43--49

EN

Free Space Optical (FSO) communication is a quickly developing technology that is designed to handle high data rates while maintaining a good quality factor (Q-factor). Many novel techniques have been implemented to cope with atmospheric attenuating factors, such as fog and rain. Here, we have introduced circular polarization shift keying (C-PolSK) modulation to produce a stable and uniform light beam. The plane of polarized light keeps rotating along with the propagation vector, which helps reduce phase variations and cross-channel eﬀects. C-PolSK provides higher penetrating power and attenuation resistance over linear polarization shift keying (L-PolSK). Two diﬀerent C-PolSK models have been proposed and graphical comparisons, relying on such parameters as Q-factor, transmission distance and inputoutput power, have been made. The cases of moderate fog and rain attenuation are taken to verify the model’s eﬃciency. Polarized light is split into two orthogonal components and then modulated using the Mach-Zehnder modulator. One of the models also employs the principle of orthogonal diﬀerential phase shifting. Eye diagrams have been provided to verify the bit error rate (BER). The orthogonal diﬀerential phase shifted C-PolSK model proves to be the most suitable implementation prototype.

14

Compensation of Fading Channels Using Partial Combining Equalizer in MC-CDMA Systems

Zidane M., Safi S., Sabri M.

Journal of Telecommunications and Information Technology

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2017

|

nr 1

5--11

EN

In this paper the performance of a partial combining equalizer for Multi-Carrier Code Division Multiple Access (MC-CDMA) systems is analytically and numerically evaluated. In the part of channel identification, authors propose a blind algorithm based on Higher Order Cumulants (HOC) for identifying the parameters representing the indoor scenario of Broadband Radio Access Networks (BRAN A) channel model normalized for MC-CDMA systems. Theoretical analysis and numerical simulation results, in noisy environment and for different Signal to Noise Ratio (SNR), are presented to illustrate the performance of the proposed algorithm in the one hand, and the other hand the impact of partial combining equalizer on the performance of MC-CDMA systems.

15

Evaluation of the Impact of Transient Disturbances on Railway Signaling Systems Using an Adapted Time-Frequency Analysis Method

Kousri M. R., Deniau V., Heddebaut M., Baranowski S.

International Journal of Electronics and Telecommunications

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2017

|

Vol. 63, No. 4

347--354

EN

As many other industrial environments, the railway electromagnetic environment is characterized by a large number of electromagnetic signals and disturbances. Among these, transient signals, with high energy level and wide frequency spectrum, represent an important threat to different signaling subsystems. In this paper, a new methodology dedicated to the detection and the characterization of the transient disturbances is presented. Based on a flexible and adjustable time-frequency analysis, this methodology is used to evaluate the impact of transient disturbances on a ground-to-train radio communication. A test bench was developed in order to validate the results of this evaluation.

16

Comparative Analysis of Channel Estimation Techniques in SISO, MISO and MIMO Systems

Obinna O., Kennedy O., Osemwegie O., Nsikan N.

International Journal of Electronics and Telecommunications

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2017

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Vol. 63, No. 3

299--304

EN

The ever-growing need for high data rate, bandwidth efficiency, reliability, less complexity and less power consumption in our communication systems is on the increase. Modern techniques have to be developed and put in place to meet these requirements. Research has shown, that compared to conventional Single Input Single Output (SISO) systems, Multiple-Input Single Output (MISO), and Multiple-Input Multiple-Output (MIMO) can actually increase the data rate of a communication system, without actually requiring more transmit power or bandwidth. This paper aims at the investigation of the existing channel estimation techniques. Based on the pilot arrangement, the block type and comb type are compared, employing the Least Square estimation (L.S) and Minimum Mean Squared Error (MMSE) estimators. Pilots occupy bandwidth, minimizing the number of pilots used to estimate the channel, in order to allow for more bandwidth utilization for data transmission, without compromising the accuracy of the estimates is taken into consideration. Various channel interpolation techniques and pilot-data insertion ratio are investigated, simulated and compared, to determine the best performance technique with less complexity and minimum power consumption. As performance measures, the Mean Squared Error (MSE) and Bit Error Rate (BER) as a function of Signal to Noise power Ratio (SNR) of the different channel estimation techniques are plotted, in order to identify the technique with the most optimal performance. The complexity and energy efficiency of the techniques are also investigated. The system modelling and simulations are carried out using Matlab simulation package. The MIMO gives the optimum performance, followed by the MISO and SISO. This is as a result of the diversity and multiplexing gain experienced in the multiple antenna techniques using the STBC.

17

Optimal combiners in pre-amplified optical wireless systems under medium-to-strong atmospheric turbulence

Sagias N. A., Boucouvalas A. C., Yiannapoulos K., Uysal M., Ghassemlooy Z.

Image Processing & Communications

|

2016

|

Vol. 21, no. 1

23--32

EN

In this work we analytically investigate optimal combiners for pre-ampliﬁed diversity receivers that operate under medium-tostrongatmosphericturbulence. We ﬁrst demonstrate that the combi ner performance is strongly affected by the existence of a signal-ampliﬁed spontaneous emission beat noise at the output of the photodetector. Due to the Signac dependent nature of noise, the optimal combi ner can be classiﬁed as a hybridone,of which performance is between the well-known equalgain and maximal-ratio combiner architectures. Having established the optimal design, we further assess the proposed combiner performance over gamma-gamma and negative-exponential fading environments.

18

Decreasing of error probability in telecommunication access networks by using amplitude modulation of many components

Klymash M., Gorbatyy I.

ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes

|

2014

|

Vol. 3, No 1

55--60

EN

The paper addresses the research of data transmission technologies in telecommunication access networks. These networks are characterized by limited bandwidth and are suitable for high speed data transmission. Particular attention is paid on the data transmission technologies in telecommunication access networks based on symmetrical telecommunication lines. Paper proposes the method of adaptive data transmission in telecommunication access networks using amplitude modulation of many components. The results of mathematical modeling are presented, which allows estimating the bit error rate decrease in telecommunication access networks using this method.

19

Nowe możliwości komunikacji w sieciach mimo

Pawelec J., Krawczyk Z.

Logistyka

|

2011

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nr 6

PL

Artykuł dotyczy nowej techniki transmisji informacji w sieciach bezprzewodowych. Polega ona na tworzeniu wielu kanałów (ścieżek) przestrzennych między nadawcą i odbiorcą, co pozwala znacznie zwiększyć sumaryczną przepustowość łącza i/lub niezawodność. Autor wprowadza prosty model takiej transmisji, w którym uwzględnia istotne czynniki środowiskowe, w tym nie-selektywne (płaskie) zaniki sygnału. W efekcie otrzymuje się w drodze symulacji Monte Carlo krzywe elementowej stopy błędów w funkcji stosunku mocy sygnał/szum dla parametrycznej zmiany znormalizowanego pasma zaników BT, gdzie B- pasmo koherencji (niestałości) zaników, 1/T -szybkość transmisji sygnału. We wnioskach autor potwierdza efektywność nowej technologii z jednoczesnym zastrzeżeniem, że faktyczne zyski są znacząco mniejsze od przewidywań teorii dla typowych warunków eksploatacji i że konieczne są duże nakłady środków finansowych w toku opracowania i wdrażania nowej technologii do praktyki.

EN

The paper deals with a new technique of signal transmission in wireless networks. It consists in creation the many space channels between transmitter and receiver, which facilitates in significant growth of aggregate link capacity and/or reliability. In the paper the simple model of such transmission is given, which takes into account the essential environment factors, including non-selective fading. In a result the BER curves are obtained via Monte Carlo simulation for different normalized fading bandwidth BT, where B is a Doppler shift and T - duration of a signal symbol. In conclusion a high efficiency of new technology is emphasized, and some limitations specified such as high complexity and cost. The real gain is, however, quite well, thou lower than predictions of the pure theory.

20

Performance Analysis of Hybrid Phase Shift Keying over Generalized Nakagami Fading Channels

Youssuf M., Abdelmageed M. Z.

Journal of Telecommunications and Information Technology

|

2010

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nr 3

77-82

EN

In addition to the benefits of hybrid phase shift keying (HPSK) modulation in reducing the peak to average power ratio of the transmitted signal to reduce the zero cross- ings and the 0?-degree phase transmissions, HPSK enhances the bit error rate (BER) measure of the signal performance. The constellation of the HPSK is analyzed, and an expression for the conditional probability of HPSK modulation over additive white Gaussian noise (AWGN) is derived. This BER measure of HPSK is shown to outperform quadrature phase shift keying (QPSK) modulation. HPSK performance through Nakagami - m fading channel is also considered.