On the satellite diversity in CDMA based mobile satellite systems (original) (raw)
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Satellite diversity in mobile satellite CDMA systems
IEEE Journal on Selected Areas in Communications, 2001
The paper addresses the exploitation of satellite diversity in a satellite mobile network. In particular, we focus on the impact of diversity on service availability and on system capacity, considering the forward link of a CDMA system with a multisatellite and multibeam architecture. The analysis includes the effects of path blockage, intrabeam and interbeam interference, imperfect power control, and fading correlation in the time domain due to nonideal interleaving. A closed-form solution is given for the estimation of system capacity. We show that satellite diversity is essential in providing service availability in urban and suburban areas, while the impact of satellite diversity on system capacity may be positive or negative, mainly depending on the fading channel characteristics. In particular, diversity becomes more and more beneficial for increasing fading time-domain correlation (i.e., for low mobile speed and/or limited interleaving depth). The analytical results have been validated by means of Monte Carlo simulation.
Satellite Diversity Gain Over The LEOS Channel , Based CDMA Systems
2000
There is a trend for mobile satellite system architectures aimed at the deployment of multi-satellite constellations in Non-Geostationary Earth Orbits (NGEOs). This allows the user terminals to be small size, low cost and having low power demand. In present and next generation satellite systems, CDMA has been proposed as the multiple access technique for a number of mobile satellite communication systems. To enhance the coverage and quality of service, Low Earth Orbiting (LEO) constellations are usually selected. In this paper, we analyze the performance of the downlink of a LEO satellite channel. The provision of such a service requires that the user have sufficient link quality for the duration of service. To have sufficient link quality, the user must have an adequate power to overcome the path loss and other physical impairments to provide acceptable communication and improve the performance of the system. This paper addresses satellite diversity with the effect of both power co...
Path diversity performance of DS-CDMA systems in a mobile satellite channel
IEEE Transactions on Vehicular Technology, 2000
We derive easy to compute semianalytical expressions for the bit error rate performance of coherent and differentially coherent binary phase-shift keying direct-sequence code-division multiple-access systems operating in a mobile satellite channel. The channel is modeled as frequency nonselective with diversity gain obtained through path diversity. This is the scenario when a signal is transmitted to all satellites in view, and
International Conference on Aerospace Sciences and Aviation Technology
In this paper, we analyse the performance of the downlink of a Non-Geostationary Earth Orbits (NGEO) mobile satellite channel based on Direct Sequence-Code Division Multiple Access (DS-CDMA) in the presence of shadowing, fading and interference from other satellites visible at the same time. In particular, the performance of QPSK convolutionally coded DS-CDMA over a Rice-Lognormal channel is analysed in depth. The provision of such a service requires that the user must have sufficient link quality for the duration of call. To have sufficient link quality, the user must have an adequate power to overcome the path loss and other physical impairments and maintain the performance of the system. The most important factor in determining the performance is the probability of signal shadowing which depends both on the user environment and on the constellation. The paper addresses the exploitation of satellite diversity in the Rician-Lognormal channel. In particular, we focus on the impact of satellite diversity on service availability, path blockage, call dropping and system capacity, considering the effects of imperfect power control, shadowing and voice activity. Concatenated codes are used to provide different bit error probabilities for different services. We show that satellite diversity is an essential in providing service availability especially in urban and suburban areas. Also we show the impact of satellite diversity on the system capacity under different environments, which is related to elevation angle, latitude and the nature of the user terminal environment.
Improvement of QoS of Land Mobile Satellite Systems Using Diversity Techniques
2014
In order to enhance the availability and the offered Quality of Service (QoS), Land Mobile Satellite Systems (LMSS) will have the option to use simultaneous transmission via two or more satellite as diversity. In this paper the performance of a TDMA and CDMA single user return link employing such a diversity reception is investigated by means of computer simulation using a multi state mobile satellite channel model. System capacity and availability have been theoretically evaluated under different operating conditions. The obtained results have shown that by using signal combining techniques improvement of the balance between service availability and system capacity is feasible.
IEEE Communications Letters, 2000
To mitigate the main impairments due to the mobile satellite channel, satellite systems adopting code-division multiple access (CDMA) can exploit diversity. Each signal can flow through more than one paths, increasing link availability or improving signal-to-noise ratio (SNR). This letter presents a general mobile satellite channel model for an arbitrary diversity order assuming that all the links are statistically independent. A diversity availability improvement upper bound is calculated.
Downlink capacity analysis for DS-CDMA satellite systems accounting for on-board power constraints
2000 IEEE Sixth International Symposium on Spread Spectrum Techniques and Applications. ISSTA 2000. Proceedings (Cat. No.00TH8536), 2000
This paper presents a novel methodology for the analysis of the downlink of a DS-CDMA mobile satellite system which allows to evaluate the impact of the power limitations expected in a satellite-based access in terms of capacity. The methodology has been applied to compare an optimum power control, providing BER-driven thresholds, with a pure Signal-to-Interference ratio (SIR)-based strategy. Relationships among service BER, channel states statistic and expected dynamic range of the outer-loop process are derived. Concluding remarks on power management policy, and its impact on the overall capacity, are given.
Design study for a CDMA-based LEO satellite network: downlink system level parameters
IEEE Journal on Selected Areas in Communications, 1996
The performance analysis of a new concept of a code-division multiple-access (CDMA) based low earth orbit (LEO) satellite network for mobile satellite communications is presented and discussed. The starting point was to analyze the feasibility of implementing multisatellite and multipath diversity reception in a CDMA network for LEO satellites. The results will be used to specify the design parameters for a system experimental test bed. Due to the extremely high Doppler, which is characteristic of LEO satellites, code acquisition is significantly simplified by using a continuous wave (CW) pilot carrier for Doppler estimation and compensation. The basic elements for the analysis presented in this paper are: the channel model, the pilot carrier frequency estimation for Doppler compensation, and multipath and multisatellite diversity combining.
Comparison of CDMA and FDMA/TDMA in non-GEO Satellite Systems
4bstract--We compare CDMA and FDMA (or TDMA) schemes in multi-beam non-geostationary satellite systems, taking the effects of antenna patterns on inter-cell interference into consideration. The maximum acceptable number of users per cell in uplink is employed as a measure of the system capacity. We have found that in FDMA (or TDMA) systems the maximum acceptable number of users varies according to the altitude of the satellites, while the performance is insensitive to the altitude in CDMA systems. For this reason, the altitude of the satellites is found to be an important factor for selecting multiple access schemes in non-geostationary satellite systems.
2013
For mobile satellite systems, quality of service and service availability depend on the line-of-sight satellite availability. The satellite visibility is one of the major factors which influence satellite link availability, since the satellite channel behavior is depended on the link conditions between satellite and land user. Because of this, the mobile satellite systems are using satellite constellation in low elevation orbits, which can provide multiple satellite visibility. In this paper a closed form expression for the performance of the post-detection product detector combiner (PDC) operating on L correlated branches in Nakagami fading has been derived, considering the DPSK signaling scheme and Nakagami flat fading channel. The average bit error rate (BER) obtained with this scheme is compared to the ideal predetection maximum ratio combining (MRC), showing limited loss. The post-detection product detector combiner is shown to perform better than the selection diversity combiner (SDC) under the considered case of mobile satellite systems.