Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

A Mobile Satellite Experiment (MSAT-X) network definition

The network architecture development of the Mobile Satellite Experiment (MSAT-X) project for the past few years is described. The results and findings of the network research activities carried out under the MSAT-X project are summarized. A framework is presented upon which the Mobile Satellite Systems (MSSs) operator can design a commercial network. A sample network configuration and its capability are also included under the projected scenario. The Communication Interconnection aspect of the MSAT-X network is discussed. In the MSAT-X network structure two basic protocols are presented: the channel access protocol, and the link connection protocol. The error-control techniques used in the MSAT-X project and the packet structure are also discussed. A description of two testbeds developed for experimentally simulating the channel access protocol and link control protocol, respectively, is presented. A sample network configuration and some future network activities of the MSAT-X project are also presented

Performance evaluation of FSO communication systems over weak atmospheric turbulence channel for eastern coast of South Africa.

Masters Degree. University of KwaZulu-Natal, Durban.Free space optical (FSO) communication, otherwise known as optical wireless communication (OWC), is an established line-of-sight telecommunication technique which utilises an optical signal carrier to propagate modulated signals in the form of a light wave (visible or infrared) over the atmospheric medium. It has numerous advantages, including ease of deployment, large bandwidth, cost effective, full duplex high data rate throughput, protocol independence, highly secured data rate transmission, unregulated frequency spectrum, limited electromagnetic interference, and minimum amount of power consumption. With all the inherent advantages in FSO systems, the technology is impaired by atmospheric turbulence. Atmospheric turbulence occurs due to the persistent random changes of the refractive index as a result of variations in atmospheric temperature and pressure. This results in fluctuations in the irradiance of the laser (simply referred to as scintillation), which may lead to attenuation of optical signals in the FSO communication system. Thus, atmospheric attenuation and turbulent conditions have negative effects on the performance and ease of deployment of FSO communication systems. In this dissertation, we examine the performance of FSO systems over weak atmospheric turbulence channel for the eastern coast of South Africa. We evaluate the feasibility of the FSO link and how to improve the reliability by estimating the link margin, probability of attenuation exceedance, power scintillation index, overall power loss due to attenuation and turbulence, link budget estimate for different link lengths and wavelengths. The FSO system availability estimated for the eastern coast of South Africa is above 99% for link distances ranging from 1 km-4 km at 850 nm, 950 nm and 1550 nm. It is also observed that the FSO link availability increases with corresponding increase in wavelengths. Adopting the Kim model to estimate the atmospheric attenuation at 850 nm wavelength, the attenuation due to scattering contributes 9.47% to the absolute atmospheric losses while the atmospheric turbulence loss contributes 90.53% to the overall power loss at a link range of 4 km. Using the Ferdinandov model for a link range of 4 km at 950 nm wavelength, the attenuation due to scattering contributes 8.81% to the total power loss while the atmospheric turbulence loss contributes 91.19% to the overall power loss. It is observed that the attainable link distance increases with increase in atmospheric visibility status. The FSO system availability reduces with increase in the propagation link distance. Furthermore, it is found that the fading loss from scintillation effects strongly depends on the power scintillation index. An increase in the power scintillation index, causes an increase in the fading loss. Thus, the power scintillation index also increases per unit increase in transmission link length and refractive index. The compensation margin for such atmospheric fading loss increases with decrease in accessible FSO system bound probability. Therefore, for a highly reliable FSO system link, extra margin must be incorporated to compensate for fading loss caused by scintillation

M-ary differential phase shift keying with non-coherent detection in mobile channels

In this thesis the system performances of M-ary differential phase shift keying (DPSK) with limiter discriminator detector (LDD) and differential phase detector (DPD) are investigated. The average error probability for DPSK-LDD and DPSK-DPD is evaluated in the additive white Gaussian noise (AWGN) channel and fading channels which include the satellite mobile channel (Rician) and the land mobile channel (Rayleigh). The systems analysed in this thesis are narrow-band systems which use Nyquist filters as the system filters. The time domain representation of the signal is derived for the system. Non-coherent detection methods; limiter discrimination detection and differential phase detection are analysed. In the DPSK-LDD system there is intersymbol interference (ISI) at the optimum sampling time. We can use the roll-off (3 of the Nyquist filter to reduce the effect of ISI by increasing the value of (3. Expressions for the error probability of DPSK-LDD and DPSK-DPD are derived. The average error probability for binary, quaternary and octal symbols is computed as a function of various parameters such as energy to noise ratio, time delay, Doppler frequency shift and roll-off (3 of the Nyquist filters. In the DPSK-LDD system the best sampling time has a shift of T/2 (T is the symbol duration) from the point at which DPSK-DPD samples are optimal. The error probability for DPSK-LDD fluctuates against time delay for small value of the time delay while for DPSK-DPD it increases with time delay. In the presence of Doppler frequency shift the DPSK-LDD system performs better than the DPSK-DPD system. In the absence of Doppler frequency shift the DPSK-DPD system gives a lower error probability than the DPSK-LDD system. The error probability for both DPSK-LDD and DPSK-DPD decreases with increasing K (the ratio of energy in specular and diffuse components), energy to noise ratio and (3 and the error probability increases with increasing Doppler frequency shift and the number of symbols

Bit Error Rate (BER) Comparison of AWGN Channels for Different Type’s Digital Modulation Using MATLAB Simulink

The MATLAB software with relevant Toolboxes for developing Simulink model is used for the simulation of system. In this paper, three basic types of digital modulation techniques are discussed then the bit error rate performance characteristics of receiver are evaluated by using MATLAB Simulink model for FSK, PSK and QAM modulation techniques. There are various kinds of channel used in wireless communication. In this paper, the AWGN channel is used between transmitter and receiver. This paper focuses on the characterization and the design of analog signal waveforms that carry digital information and compares their performance on an AWGN channel

Proceedings of the Mobile Satellite Conference

A satellite-based mobile communications system provides voice and data communications to mobile users over a vast geographic area. The technical and service characteristics of mobile satellite systems (MSSs) are presented and form an in-depth view of the current MSS status at the system and subsystem levels. Major emphasis is placed on developments, current and future, in the following critical MSS technology areas: vehicle antennas, networking, modulation and coding, speech compression, channel characterization, space segment technology and MSS experiments. Also, the mobile satellite communications needs of government agencies are addressed, as is the MSS potential to fulfill them