Hussein Ahmed Mahmood, Al-Karawi Hussein Shookor, K. Y. Rumyantsev
2021-01-19
Abstract ▼
The high demand for increased bandwidth, data rate and quality in optical communication systems in modern applications. Radio over free space optics (RoFSO) is deemed a new design methodology over wireless systems and networks. This technique has to ensure data rates like ones presented by means optical fiber communication techniques in keeping with a portion of its arrangement cost. Such systems are implemented by combined radio signal (RF) with optical signal, which containing various wireless administrations and Free Space Optics (FSO) link. In this paper, the simulation and evaluation system of Subcarrier Multiplexing/Amplitude Shift Keying (SCM/ASK) transmitter for Free Space Optical Communication is proposed. 1Gb/s data Rate given to the system. Whilst 10 GHz radio frequency signal setting in electrical amplitude modulator. Thereafter, radio signal is added with 100 subcarrier channels of 10 MHz spacing channel at operated first channel frequency of 60 MHz. These subcarrier channels with 900 combined with 10 GHz sin wave signal ( radio frequency ) at hybrid coupler, the combination of each subcarriers and radio signal are modulated by LiNb Mach-Zehnder optical modulator with 1550 nm wavelength continues wave laser signal at 10 dBm input power. The optical modulated signal (after optical modulator) is transmitted over a various free space optical link from 300m to 1km under the Atmospheric turbulence effect (the structure feature of the refractive index). The system is evaluated utilizing Opti system software with Q-factor and BER terminology. It is shown that the maximum optical distance for weak turbulence ( at BER equal to 10-9 is 950m, while the maximum optical distance for strong turbulence is 850m.
This paper considers infrastructure to wireless mobile communications using Advanced-WiMAX. In this paper, the productivity performance throughput experienced the mobile users is compared in the cases of 3D SISO and 3D MIMO-channel models within a large urban cell. Re-cently, there has been substantial work and interest to expand MIMO and SISO-processing by taking into consideration in the design the elevation plane in addition to the azimuth dimension, Since the evaluation of elevation MIMO and SISO performance in 3D-channel design is needed. Bit-level simulation is performed for the channel in WiMAX operating at 2.5 GHz. The results indicate the accuracy of the 3D channel model, and the correct estimation of the 3D channel is showed. The difference in higher predicted capacity for the 3D channel model has resulted in the small-scale parameters for the SISO-case and the lower spatial correlation parameters for the MIMO-case. Different mobility speeds, the effect of the Doppler shift, several paths and the signal attenuation at a distance and with increasing frequency has been carried out in this study. Simulation runtimes are measured concerning the multi-section modulation types for both systems SISO and MIMO. Noise immunity is adversely affected by an increase in the number of spatial streams. The noise immunity is also affected by the increase in the number of antennas at the transmitters and receivers.
Reducing the probability of errors in message transmission is important in satellite, wireless and space communication systems. Reducing the probability of bit errors in a wireless communication system is possible by using encoding of the data being sent. Using channel encoding allows detecting and correcting errors in message transmission in a noisy channel. The aim of the work is to study the effect of using Reed-Solomon codes and the algorithm of space-time signal processing in a receiver using an adaptive antenna array on increasing noise immunity in wireless radio communication systems. In the presence of complex signal propagation paths, this allows performing spatial filtering in channels with reflections. The adaptation method, considered in this paper, is based on the theory of vectors and eigenvalues of the spatial correlation matrix. For Reed-Solomon codes, the simulation results show a significant decrease in bit error rates due to the correction of transmission errors. By using adaptive algorithms for single-input multiple-output orthogonal frequency division multiplexing (SIMO-OFDM) and multiple-input multiple-output MIMO-OFDM systems together with the Reed-Solomon code for the transmitted message, the signal-to-noise ratio for a fixed bit error level was increased to 8 dB and 5 dB, respectively. The results show that the adaptive algorithm with simultaneous use of the Reed-Solomon code can increase the throughput while significantly reducing the error probability. Under conditions of multipath signal propagation, it can be argued that the use of adaptive space-time algorithms improves the noise immunity of the receiving system during signal processing.
V.P. Fedosov, Al-Musawi Wisam Mohammedtaqi M. Jawad, S.V. Kucheryavenko
2025-01-30
Abstract ▼
The development of the telecommunications industry is focused on the use of wireless broadband communication systems that allow increasing the speed of information transfer. New technologies with high transmission capabilities have been developed to solve this problem. Limitation of the signal spectrum and signal fading in Fresnel zones due to multipath components in a wireless system deployed in densely built-up urban areas are significant problems in the design of wireless communication systems, as well as the occurrence of the Doppler effect due to the movement of the mobile station and signal attenuation during propagation in the channel in different frequency ranges. To increase the speed and throughput, it is possible to use the procedure of transmitting and receiving signals to form channels with one input and several outputs SIMO (Single Input Multiple Output), providing spatial filtering when choosing the path with the maximum signal power. The article presents the analysis and modeling of data transmission based on the SIMO system of the 3D WiMAX wireless channel. The results of comparison of signal processing by this method with and without the adaptive algorithm, obtained by the criterion of maximum signal-to-noise ratio (SNR) are presented by the dependences of the probability of occurrence of a bit error (BER) on the signal-to-noise ratio (SNR). As a result of modeling, it was concluded that for the same system, the probability of error is sensitive to a change in the modulation type, in other words, BER changes in accordance with a change in the type of signal modulation. It can also be concluded that SIMO systems are sensitive to multipath signal propagation for the same modulation type, and BER increases with an increase in the number of receivers since the signal-to-noise ratio SNR decreases.
