Wyniki wyszukiwania - BazTech

1

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

Sinha Shivaji, Kumar Chakresh

Optica Applicata

|

2023

|

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.

2

Analiza jakości transmisji treści audio-wideo w symulowanym łączu telekomunikacyjnym z wykorzystaniem techniki OFDM

Zamłyńska Monika, Falkowski-Gilski Przemysław

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2022

|

nr 4

219--223

PL

Wdrożenie niezawodnego systemu komunikacji audio-wideo przynosi wiele korzyści. Z uwagi na fakt, że ilość dostępnego pasma stale się kurczy, badacze koncentrują się na nowatorskich metodach transmisji. Obecnie technika OFDM (Orthogonal Frequency Division Multiplexing) jest szeroko stosowana zarówno w mediach przewodowych, jak i bezprzewodowych. W pracy przedstawiono badania jakości QoS (Quality of Service) symulowanego łącza transmisji danych, przy zmiennych poziomach SNR (Signal-to-Noise Ratio) oraz BER (Bit Error Rate).

EN

Application of a reliable audio-video communication system brings many advantages. As the amount of available bandwidth continues to shrink, researchers focus on novel types of transmission. Nowadays, OFDM (Orthogonal Frequency Division Multiplexing) is widely utilized both in wired and wireless media. In this paper we investigate the QoS (Quality of Service) parameters of a simulated data transmission system, including SNR (Signal-to-Noise Ratio) and BER (Bit Error Rate).

3

Investigation of Vehicular S-LSTM NOMA Over Time Selective Nakagami-m Fading with Imperfect CSI

Shankar Ravi, Chaudhary Bhanu Pratap, Mishra Ritesh Kumar

Journal of Telecommunications and Information Technology

|

2022

|

nr 4

47--59

EN

In this paper, the performance of a deep learningbased multiple-input multiple-output (MIMO) non-orthogonal multiple access (NOMA) system is investigated for 5G radio communication networks. We consider independent and identically distributed (i.i.d.) Nakagami-m fading links to prove that when using MIMO with the NOMA system, the outage probability (OP) and end-to-end symbol error rate (SER) improve, even in the presence of imperfect channel state information (CSI) and successive interference cancellation (SIC) errors. Furthermore, the stacked long short-term memory (S-LSTM) algorithm is employed to improve the system’s performance, even under time-selective channel conditions and in the presence of terminal’s mobility. For vehicular NOMA networks, OP, SER, and ergodic sum rate have been formulated. Simulations show that an S-LSTM-based DL-NOMA receiver outperforms least square (LS) and minimum mean square error (MMSE) receivers. Furthermore, it has been discovered that the performance of the end-to-end system degrades with the growing amount of node mobility, or if CSI knowledge remains poor. Simulated curves are in close agreement with the analytical results.

4

Performance analysis of DFT-S-OFDM waveform for Li-Fi systems

Hussin S., Shalaby E. Mansour

Opto-Electronics Review

|

2021

|

Vol. 29, No. 4

167--174

EN

In this paper, the effect of an indoor visible light communication channel is studied. Moreover, the analysis of the received power distribution of the photodiode in the line of sight and the first reflection of the channel without line of sight with several parameters is simulated. Two different waveforms are explained in detail. Orthogonal frequency division multiplexing has been widely adopted in radio frequency and optical communication systems. One of the most important disadvantages of the orthogonal frequency division multiplexing signal is the high peak-to-average power ratio. Therefore, it is important to minimize the peak-to-average power ratio in the visible light communication systems more than in radio-frequency wireless applications. In the visible light communication systems, the high peak-to-average power ratio produces a high DC bias which reduces power efficiency of the system. A discrete Fourier transform spread orthogonal frequency division multiplexing is proposed to be used in wireless communication systems; its ability to minimize peak-to-average power ratio has been tested. The analysis of two different subcarrier allocation methods for the discrete Fourier transform-spread subcarriers, as well as the examination of two distinct subcarrier allocation strategies, distributed and localized mapping, are investigated and studied. The effects of an accurate new sub-band mapping for the localized discrete Fourier transform spread orthogonal frequency division multiplexing scheme are presented in this paper. The light-fidelity system performance of the orthogonal frequency division multiplexing and discrete Fourier transform spread orthogonal frequency division multiplexing with different sub-mapping techniques are simulated with Matlab™. A system performance size of bit error rate and peak-to-average power ratio are obtained, as well.

5

Shallow Water Experiment of OFDM Underwater Acoustic Communications

Kochańska Iwona, Schmidt Jan H., Marszal Jacek

Archives of Acoustics

|

2020

|

Vol. 45, No. 1

11--18

EN

The large variability of communication properties of underwater acoustic channels, and especially the strongly varying instantaneous conditions in shallow waters, is a challenge for the designers of underwater acoustic communication (UAC) systems. The use of phase modulated signals does not allow reliable data transmission through such a tough communication channel. However, orthogonal frequency-division multiplexing (OFDM), being a multi-carrier amplitude and phase modulation technique applied successfully in the latest standards of wireless communications, gives the chance of reliable communication with an acceptable error rate. This paper describes communication tests conducted with the use of a laboratory model of an OFDM data transmission system in a shallow water environment in Wdzydze Lake.

6

Cooperative MIMO OFDM system based on Amplify and Forward Relay: Evaluation of ZF-SIC and MMSE-SIC equalization

Rahman M., Alam S., Islam S., Samy A. A., Islam N. A.

Przegląd Elektrotechniczny

|

2018

|

R. 94, nr 9

75--79

EN

In the world of wireless communication, cooperative communication is a modern and unprecedented approach which enables wireless nodes to transfer the information in a cooperative manner and finally to reach the destination without least possible deterioration. Orthogonal frequency division multiplexing (OFDM) can provide high data rate and better performance and a combination of OFDM and cooperative communication may push a wireless network forward to its next generation with enhanced reliability and efficiency. In this work, we develop a mathematical model for cooperative multiple input multiple output (MIMO) OFDM system. Results are achieved in the study to evaluate and compare bit error rate (BER) for different detection schemes. Based on the results it can be mentioned that the performance of cooperative MIMO-OFDM with space time block code (STBC) under amplify and forward (AF) relay for the MMSE-SIC detection scheme was found very satisfactory with improved signal to noise ratio (SNR).

PL

W artykule przedstawiono model matematyczny kooperacyjnej komunikacji bezprzewodowej wiele wejść, wiele wyjść (MIMO) z multipleksingiem i ortogonalnym podziałem częstotliwości (OFDM). Określono współczynnik BER (bit error rate) dla różnych metod detekcji. Najlepsze parametry otrzymano dla systemu STBC (space time block code).

7

Damped Zero-Pseudorandom Noise OFDM Systems

Esmaiel H.

International Journal of Electronics and Telecommunications

|

2018

|

Vol. 64, No. 4

433--438

EN

This paper proposed a new OFDM scheme called damped zero-pseudorandom noise orthogonal frequency division multiplexing (DZPN-OFDM) scheme. In the proposed scheme, ZPN-OFDM non-zero part is damped to reduce its energy, thus the mutual interference power in-between the data and training blocks with conservative the pseudo-noise conventional properties required for channel estimation or synchronization. The motivation of this paper is the OFDM long guard interval working in wide dispersion channels, whereas a significant energy is wasted when the conventional ZPN-OFDM is used as well as the BER performance is also degraded. Moreover, the proposed scheme doesn’t duplicate the guard interval to solve the ZPN-OFDM spectrum efficiency loss problem. Both detailed performance analysis and simulation results show that the proposed DZPNOFDM scheme can, indeed, offer significant bit error rate, spectrum efficiency and energy efficiency improvement.

8

Spectrum Allocation Policy in Elastic Optical Networks

Olszewski I.

International Journal of Electronics and Telecommunications

|

2017

|

Vol. 63, No. 4

423--429

EN

The considered problem covers routing and spectrum allocation problem (RSA problem) in Elastic Optical Networks while maintaining the spectrum continuity constraints, non-overlapping spectra constraints for adjacent connections on individual links of the network and spectrum contiguity constraints of the connection. In this article the modified version of the First Fit spectrum slot allocation policy for Fixed Alternate Routing in flexible optical networks has been proposed. The Fixed Alternate Routing with proposed spectrum allocation policy rejects fewer requests, provides less bandwidth blocking probability and less spectrum fragmentation than Fixed Alternate Routing with well-known First Fit and Exact Fit spectrum allocation policies. However, the cost of improving these parameters is a higher computational complexity of the proposed allocation policy.

9

Sub-sampling in OFDM with Constant Time Signal Recovery

Petrellis N.

Image Processing & Communications

|

2016

|

Vol. 21, no. 2

19--32

EN

The sub-sampling method for Orthogonal Frequency Division Multiplexing proposed recently, has been extended in this paper allowing the Analog-to-Digital Converter on the receiver side to operate in low power mode, up to 3/4 of the time. The predictability of the parity patterns generated by the Forward Error Correction encoder of the transmitter, when sparse data are exchanged, is exploited in order to define appropriate Inverse Fast Fourier Transform input symbol arrangements. These symbol arrangements allow the substitution of a number of samples by others that have already been received. Moreover, several operations of the Fast Fourier Transform can be omitted because their result is zero when identical values appear at its input. The advantages of the proposed method are: low power, higher speed and fewer memory resources. Despite other iterative sub-sampling approaches like Compressive Sampling, the proposed method is not iterative and thus it can be implemented with very low complexity hardware. The simulation results show that full input signal recovery or at least a very low Bit Error Rate is achieved in most of the cases that have been tested.

10

Stealthy Information Transmission in the Terrestrial GMDSS Radiotelephone Communication

Shishkin A. V., Koshevoy V. M.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

|

2013

|

Vol. 7, no. 4

541--548

EN

Audio watermarking (AW) technology is considered for stealthy information embedding directly into audio signal. Inherent in analog radiotelephone channel interferences against watermarks are analyzed. Robust encoding/decoding algorithms are presented and appropriate project of AW system named as Automatic Radio Telephone Identification System (ARTIS) is proposed. Experimental results for the practical VHF radio channel are presented. Relating on processing complexity the designed system enables imperceptibly transmit data on a rate up to 260 bit/sec in the standard VHF radio channel. ARTIS provides the full compatibility with the existing radio installation, and doesn’t require replacement of standard VHF transceivers and operational procedures. Besides, automatic identification the system may be used in the special applications, for example, under the threat of terrorist attack; generally contributes to navigation safety and information security.

11

Modulation-Mode Assignment in SVD-Aided Downlink Multiuser MIMO-OFDM Systems

Aust S., Ahrens A., Benavente-Peces C. C.

International Journal of Electronics and Telecommunications

|

2011

|

Vol. 57, No. 4

459-464

EN

Multicarrier transmission such as OFDM (orthogonal frequency division multiplexing) is an established technique for radio transmission systems and it can be considered as a promising approach for next generation wireless systems. However, in order to comply with the demand on increasing available data rates in particular in wireless technologies, systems with multiple transmit and receive antennas, also called MIMO (multiple-input multiple-output) systems, have become indispensable for future generations of wireless systems. Due to the strongly increasing demand in high-data rate transmission systems, frequency non-selective MIMO links have reached a state of maturity and frequency selective MIMO links are in the focus of interest. In this field, the combination of MIMO transmission and OFDM can be considered as an essential part of fulfilling the requirements of future generations of wireless systems. However, single-user scenarios have reached a state of maturity. By contrast multiple users' scenarios require substantial further research, where in comparison to ZF (zero-forcing) multiuser transmission techniques, the individual user's channel characteristics are taken into consideration in this contribution. The performed joint optimization of the number of activated MIMO layers and the number of transmitted bits per subcarrier shows that not necessarily all user-specific MIMO layers per subcarrier have to be activated in order to minimize the overall BER under the constraint of a given fixed data throughput.