841 research outputs found

    Correlative Tracking of Pseudo-Noise Codes using a Phase Shifted Reference

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    This work investigates a first-order correlation loop for tracking pseudo-noise (PN) codes. The local reference is produced by a PN sequence generator in series with a Hilbert transform filter. The tracking performance of this non-linear loop is compared with conventional early-late delay-lock loops (ELDLL). Using a conservative definition of bandwidth, the new loop was found to be superior at moderate to low signal-to-noise ratios (SNR). Another advantage of the new structure is that it has a very large (arguably infinite) lock range

    Performance analysis of a second order delay-lock loop with application to a CDMA system with multipath propagation

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    CDMA systems require synchronization between the received sequence and the locally generated sequence. This is done by means of a delay-lock loop (DLL). The differential equation of an incoherent second-order DLL has been programmed. The mean time to lose lock (MTLL) of the DLL is a very important design parameter. The authors have obtained this parameter by computer simulation and are able to plot the MTLL as a function of the signal to noise ratio in the data bandwidth. In a narrow-band system, the simulation shows that the effect of the fast Rayleigh fading is a performance degradation even with high mean signal to noise ratio. Assuming a wide-band system, so that the receiver has enough bandwidth to resolve the different propagation paths, the authors propose a modified DLL scheme. The MTLL of the proposed DLL is evaluated using a dynamic simulation of the multipath channel. The results show an improvement with respect to the conventional DLL.Peer ReviewedPostprint (published version

    Code Acquisition at Low SINR in Spread Spectrum Communications

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    Abstract—We consider the problem of code acquisition at low signal to interference and noise ratio (SINR) in packet-based spread spectrum communications, where a centralized “pilot ” synchronization signal and high-precision oscillators are not available. Such problems arise in the context of ad-hoc networks, for example, which require fast code acquisition times and gradual degradation of the network with decreasing SINR. We motivate the use of the “postdetection integration ” ap-proach, which utilizes the energy of multiple bits in a packet, for code acquisition at low SINR. We present the implementation of a fully parallel architecture which simultaneously looks at all possible code alignments over multiple bits. This leads to a drastic reduction in acquisition time compared to serial search based methods. We report some preliminary simulation and experimental results from a hardware prototype of a transceiver on which the code acquisition algorithm was implemented. I

    Adaptive systems in digital communication designs

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    Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (leaves 98-100).by Xinben Garrison Qian.M.S

    Millimeter communication propagation program, volume III Final report, 1 Nov. 1964 - 1 Nov. 1965

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    Annotated bibliography for millimeter wave communication propagation program for space-earth communication

    Application of advanced on-board processing concepts to future satellite communications systems: Bibliography

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    Abstracts are presented of a literature survey of reports concerning the application of signal processing concepts. Approximately 300 references are included
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