A Faded-Compensation Technique for Digital Land Mobile Satellite Systems

This paper proposes a novel fade-compensation algorithm using a pilot symbol-aided technique for digital and mobile satellite systems. In a conventional pilot symbol-aided system, a pilot symbol from a known pseudorandom-symbol sequence is inserted periodically into the data-symbol sequence in the transmitter. At the receiver, these pilot symbols are extracted from the received signal and used to estimate the signal distortion introduced in the fading channel. The resultant estimate is then used to correct the fading effects in the received data symbols. In this paper, a novel fade-compensation technique that uses both the pilot symbols and the data symbols is proposed. A series of computer-simulation tests has been carried out to assess the effectiveness of the technique on the bit-error-rate (BER) performances of an uncoded 16-ary phase-shift keyed (16PSK) and an uncoded 16-ary quadrature-amplitude modulated (16QAM) signal over the land mobile satellite channels. The results have shown that substantial improvements in the BER performances of the systems can be obtained, compared to those using only the pilot symbolspostprin

Summary of the First ACTS Propagation Workshop

The first Advanced Communications Technology Satellite (ACTS) Propagation Studies Workshop (APSW I), organized by NASA/Jet Propulsion Laboratory (JPL) to plan propagation experiments and studies with NASA's ACTS, convened in Santa Monica, California, during November 28 and 29, 1989. The objectives of APSW I were to identify general and ACTS-related propagation needs, and to prepare recommendations for a study plan incorporating scientific and systems requirements related to deployment of 8 to 10 propagation terminals in the USA in support of ACTS experimental activities. A summary of workshop activities is given

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

Proceedings of the Fourteenth NASA Propagation Experimenters Meeting (NAPEX 14) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. NAPEX XIV was held on May 11, 1990, at the Balcones Research Centers, University of Texas, Austin, Texas. The meeting was organized into two technical sessions: Satellite (ACTS) and the Olympus Spacecraft, while the second focused on the fixed and mobile satellite propagation studies and experiments. Following NAPEX XIV, the ACTS Miniworkshop was held at the Hotel Driskill, Austin, Texas, on May 12, 1990, to review ACTS propagation activities since the First ACTS Propagation Studies Workshop was held in Santa Monica, California, on November 28 and 29, 1989

Future benefits and applications of intelligent on-board processing to VSAT services

The trends and roles of VSAT services in the year 2010 time frame are examined based on an overall network and service model for that period. An estimate of the VSAT traffic is then made and the service and general network requirements are identified. In order to accommodate these traffic needs, four satellite VSAT architectures based on the use of fixed or scanning multibeam antennas in conjunction with IF switching or onboard regeneration and baseband processing are suggested. The performance of each of these architectures is assessed and the key enabling technologies are identified

Performances of 16QAM with fading compensation and postdetection diversity reception in satellite mobile channels

This paper studies the effects of N-branch postdetection selection diversity reception, where N = 1, 2, 3 or 4, incorporated with fading compensation on a digital satellite mobile system. The digital satellite mobile system transmits a pilot-symbol-aided 16-ary quadrature-amplitude modulated (PSA-16QAM) signal over the Rician channels. A selection method that makes use of the pilot symbols to select one of the N branches in the diversity reception system for signal detection, and a novel PSA technique that makes use of both the pilot symbols and data symbols for fading compensation, are proposed. Computer simulation tests are used to assess the effects of the proposed techniques on bit-error rate performances (BER) of the PSA-16QAM system in the presence of additive white Gaussian noise (AWGN) or co-channel interference (CCI) in the Rician faded channels. When frequency diversity is used, PSA-16QAM with 2-branch and 4-branch diversity reception occupies about the same bandwidths as quaternary phase-shift-keying (QPSK) without using diversity and with 2-branch diversity, respectively, yet achieving the same capacity. Thus, simulation tests on the BER performances of a QPSK system without diversity and with 2-branch diversity are also carried out and the results are used to determine the preferred system arrangements. ©1997 John Wiley & Sons, Ltd.postprin

Data-aided fading estimation technique for shadowed mobile satellite fading channels

A novel data-aided fading estimation technique that employs both pilot and data symbols is proposed to significantly reduce the bandwidth redundancy of the pilot-symbol-aided (PSA) systems using receivers with low complexity and latency in the shadowed mobile satellite fading channels. The shadowed mobile satellite fading channels are modeled as the sum of a lognormally distributed direct component and a Rayleigh distributed multipath component, and the PSA system employs 16-ary quadrature-amplitude-modulation (16QAM) for transmission. Monte Carlo computer simulation has been used to assess the technique on the bit-error-rate (BER) performances of the system in the light shadowed, the average shadowed and the heavy shadowed Rician fading environments. The results have shown that the proposed technique requires a very low bandwidth redundancy to provide satisfactory BER performances, and can substantially lower the error floors of the PSA systems.postprin

Performance of a Faded-Compensated 16QAM with Diversity Reception in Mobile radio Channels

The paper studies the bit-error-rate (BER) performance of a fade-compensated 16 QAM with two-branch postdetection selection combining diversity reception in the Rayleigh fading channels. A pilot symbol-aided (PSA) technique that uses both pilot symbols and data symbols is employed for fading compensation. Computer simulation results have shown that, the use of diversity reception technique can significantly improve the BER performance when the normalized delay between the signals at the two receivers is small. It is also shown that, the error-floor is sensitive to the normalized delay, but relatively less sensitive to the power ratio between the signals at the two receivers.published_or_final_versio

Proceedings of the Fifteenth NASA Propagation Experimenters Meeting (NAPEX 15) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

The NASA Propagation Experimenters Meeting (NAPEX), supported by the NASA Propagation Program, is convened annually to discuss studies made on radio wave propagation by investigators from domestic and international organizations. The meeting was organized into three technical sessions. The first session was dedicated to Olympus and ACTS studies and experiments, the second session was focused on the propagation studies and measurements, and the third session covered computer-based propagation model development. In total, sixteen technical papers and some informal contributions were presented. Following NAPEX 15, the Advanced Communications Technology Satellite (ACTS) miniworkshop was held on 29 Jun. 1991, to review ACTS propagation activities, with emphasis on ACTS hardware development and experiment planning. Five papers were presented

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