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

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

Wideband cyclostationary spectrum sensing and characterization for cognitive radios

Motivated by the spectrum scarcity problem, Cognitive Radios (CRs) have been proposed as a solution to opportunistically communicate over unused spectrum licensed to Primary users (PUs). In this context, the unlicensed Secondary users (SUs) sense the spectrum to detect the presence or absence of PUs, and use the unoccupied bands without causing interference to PUs. CRs are equipped with capabilities such as, learning, adaptability, and recongurability, and are spectrum aware. Spectrum awareness comes from spectrum sensing, and it can be performed using different techniques

Tone calibration technique: A digital signaling scheme for mobile applications

Residual carrier modulation is conventionally used in a communication link to assist the receiver with signal demodulation and detection. Although suppressed carrier modulation has a slight power advantage over the residual carrier approach in systems enjoying a high level of stability, it lacks sufficient robustness to be used in channels severely contaminated by noise, interference and propagation effects. In mobile links, in particular, the vehicle motion and multipath waveform propagation affect the received carrier in an adverse fashion. A residual carrier scheme that uses a pilot carrier to calibrate a mobile channel against multipath fading anomalies is described. The benefits of this scheme, known as tone calibration technique, are described. A brief study of the system performance in the presence of implementation anomalies is also given

MSAT-X: A technical introduction and status report

A technical introduction and status report for the Mobile Satellite Experiment (MSAT-X) program is presented. The concepts of a Mobile Satellite System (MSS) and its unique challenges are introduced. MSAT-X's role and objectives are delineated with focus on its achievements. An outline of MSS design philosophy is followed by a presentation and analysis of the MSAT-X results, which are cast in a broader context of an MSS. The current phase of MSAT-X has focused notably on the ground segment of MSS. The accomplishments in the four critical technology areas of vehicle antennas, modem and mobile terminal design, speech coding, and networking are presented. A concise evolutionary trace is incorporated in each area to elucidate the rationale leading to the current design choices. The findings in the area of propagation channel modeling are also summarized and their impact on system design discussed. To facilitate the assessment of the MSAT-X results, technology and subsystem recommendations are also included and integrated with a quantitative first-generation MSS design

Trellis coding with Continuous Phase Modulation (CPM) for satellite-based land-mobile communications

This volume of the final report summarizes the results of our studies on the satellite-based mobile communications project. It includes: a detailed analysis, design, and simulations of trellis coded, full/partial response CPM signals with/without interleaving over various Rician fading channels; analysis and simulation of computational cutoff rates for coherent, noncoherent, and differential detection of CPM signals; optimization of the complete transmission system; analysis and simulation of power spectrum of the CPM signals; design and development of a class of Doppler frequency shift estimators; design and development of a symbol timing recovery circuit; and breadboard implementation of the transmission system. Studies prove the suitability of the CPM system for mobile communications

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