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Adaptive beamforming in a CDMA mobile satellite communications systemCode-Division Multiple-Access (CDMA) stands out as a strong contender for the choice of multiple access scheme in these future mobile communication systems. This is due to a variety of reasons such as the excellent performance in multipath environments, high scope for frequency reuse and graceful degradation near saturation. However, the capacity of CDMA is limited by the self-interference between the transmissions of the different users in the network. Moreover, the disparity between the received power levels gives rise to the near-far problem, this is, weak signals are severely degraded by the transmissions from other users. In this paper, the use of time-reference adaptive digital beamforming on board the satellite is proposed as a means to overcome the problems associated with CDMA. This technique enables a high number of independently steered beams to be generated from a single phased array antenna, which automatically track the desired user signal and null the unwanted interference sources. Since CDMA is interference limited, the interference protection provided by the antenna converts directly and linearly into an increase in capacity. Furthermore, the proposed concept allows the near-far effect to be mitigated without requiring a tight coordination of the users in terms of power control. A payload architecture will be presented that illustrates the practical implementation of this concept. This digital payload architecture shows that with the advent of high performance CMOS digital processing, the on-board implementation of complex DSP techniques -in particular digital beamforming- has become possible, being most attractive for Mobile Satellite Communications.
Document ID
19950016398
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Munoz-Garcia, Samuel G.
(European Space Agency. European Space Research and Technology Center ESTEC, Noordwijk, Netherlands)
Date Acquired
September 6, 2013
Publication Date
January 1, 1993
Publication Information
Publication: JPL, Addendum to the Proceedings of the Third International Mobile Satellite Conference (IMSC 1993)
Subject Category
Communications And Radar
Meeting Information
Meeting: ERA Conference on DSP: The Enabling Technology for Communications
Location: Amsterdam
Country: Netherlands
Start Date: March 9, 1993
End Date: March 10, 1993
Accession Number
95N22815
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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