272 research outputs found
Shuttle Ku-band signal design study
Carrier synchronization and data demodulation of Unbalanced Quadriphase Shift Keyed (UQPSK) Shuttle communications' signals by optimum and suboptimum methods are discussed. The problem of analyzing carrier reconstruction techniques for unbalanced QPSK signal formats is addressed. An evaluation of the demodulation approach of the Ku-Band Shuttle return link for UQPSK when the I-Q channel power ratio is large is carried out. The effects that Shuttle rocket motor plumes have on the RF communications are determined also. The effect of data asymmetry on bit error probability is discussed
A survey of the state of the art and focused research in range systems, task 2
Contract generated publications are compiled which describe the research activities for the reporting period. Study topics include: equivalent configurations of systolic arrays; least squares estimation algorithms with systolic array architectures; modeling and equilization of nonlinear bandlimited satellite channels; and least squares estimation and Kalman filtering by systolic arrays
An investigation into a DSP implementation of partial response signaling for 4800 bits per second full-duplex data communications over M.1020 telephone lines
Includes bibliographical references.This thesis investigates high-speed digital transmission over a conditioned, voice-grade telephone circuit (M.1020), using a technique known as partial response signaling, or PRS. In particular, the case where 4800 bps, full-duplex transmission is required in a CCI'PT V. 22 type format is investigated. The main v.22 criterion to be adhered to, is that frequency-division multiplexing (FDM) is to be used as the means of separating thetransmit and receive channels. The carrier frequencies should be 1200 Hz and 2400 Hz respectively. The investigation concerns the modulation and demodulation sections only
Advanced Modulation and Coding Technology Conference
The objectives, approach, and status of all current LeRC-sponsored industry contracts and university grants are presented. The following topics are covered: (1) the LeRC Space Communications Program, and Advanced Modulation and Coding Projects; (2) the status of four contracts for development of proof-of-concept modems; (3) modulation and coding work done under three university grants, two small business innovation research contracts, and two demonstration model hardware development contracts; and (4) technology needs and opportunities for future missions
Programming techniques for efficient and interoperable software defined radios
Recently, Software-Dened Radios (SDRs) has became a hot research topic in wireless communications eld. This is jointly due to the increasing request of reconfigurable and interoperable multi-standard radio systems able to learn from their surrounding
environment and efficiently exploit the available frequency spectrum resources, so realizing the cognitive radio paradigm, and to the availability of reprogrammable hardware architectures providing the computing power necessary to meet the tight
real-time constraints typical of the state-of-art wideband communications standards.
Most SDR implementations are based on mixed architectures in which Field Programmable Gate Arrays (FPGA), Digital Signal Processors (DSP) and General Purpose Processors (GPP) coexist. GPP-based solutions, even if providing the highest
level of flexibility, are typically avoided because of their computational inefficiency
and power consumption.
Starting from these assumptions, this thesis tries to jointly face two of the main important issues in GPP-based SDR systems: the computational efficiency and the interoperability capacity. In the first part, this thesis presents the potential of a novel programming technique, named Memory Acceleration (MA), in which the memory resources typical of GPP-based systems are used to assist central processor in executing real-time signal processing operations. This technique, belonging to the classical computer-science optimization techniques known as Space-Time trade-offs, defines
novel algorithmic methods to assist developers in designing their software-defined signal processing algorithms. In order to show its applicability some "real-world" case studies are presented together with the acceleration factor obtained. In the second part of the thesis, the interoperability issue in SDR systems is also considered. Existing software architectures, like the Software Communications Architecture
(SCA), abstract the hardware/software components of a radio communications chain using a middleware like CORBA for providing full portability and interoperability to the implemented chain, called waveform in the SCA parlance. This feature is
paid in terms of computational overhead introduced by the software communications middleware and this is one of the reasons why GPP-based architecture are generally discarded also for the implementation of narrow-band SCA-compliant communications standards. In this thesis we briefly analyse SCA architecture and an
open-source SCA-compliant framework, ie. OSSIE, and provide guidelines to enable component-based multithreading programming and CPU affinity in that framework.
We also detail the implementation of a real-time SCA-compliant waveform developed inside this modified framework, i.e. the VHF analogue aeronautical communications transceiver. Finally, we provide the proof of how it is possible to implement an efficient and interoperable real-time wideband SCA-compliant waveform, i.e. the AeroMACS
waveform, on a GPP-based architecture by merging the acceleration factor provided by MA technique and the interoperability feature ensured by SCA architecture
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Proposed implementation of a near-far resistant multiuser detector without matrix inversion using Delta-Sigma modulation
A new algorithm is proposed which provides a sub-optimum near-far resistant
pattern for correlation with a known signal in a spread-spectrum multiple access
environment with additive white gaussian noise (AWGN). Only the patterns and
respective delays of the K-1 interfering users are required. The technique does not
require the inversion of a cross-correlation matrix. The technique can be easily
extended to as many users as desired using a simple recursion equation. The
computational complexity is O(K²) for each user to be decoded. It is shown that this
method provides the same results as the "one-shot" method proposed by Verdu and
Lupas.
Also shown is a new array architecture for implementing this new solution
using delta-sigma modulation and a correlator for non-binary patterns that takes
advantage of the digitized Al: signals. Simulation results are presented which show
the algorithm and correlator to be implementable in VLSI technology. This
approach allows processing of the received signal in real-time with a delay of O(.K)
bit periods per user. A modification of the algorithm is examined which allows
further reduction of complexity at the expense of reduced performance
Spatial processing for frequency diversity schemes
A novel technique to obtain optimum blind spatial
processing for frequency diversity spread spectrum (FDSS) communication
systems is introduced. The sufficient statistics for a
linear combiner, which prove ineffective due to the interferers frequency
characteristics, are modified to yield improved detection
under partial jamming in the spectral domain. Robustness to partial
time jamming is achieved by extending the notion of replicas
over the frequency axis to a repetition over the time variable. Analysis
and simulations are provided, showing the advantages of using
FDSS with spatial diversity to combat the interference when it is
confined to a narrow frequency band or short time interval relative
to the desired signal extent in either domain.Peer Reviewe
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