2,248 research outputs found
Turbo receivers for interleave-division multiple-access systems
In this paper several turbo receivers for Interleave-Division Multiple-Access (IDMA) systems will be discussed. The multiple access system model is presented first. The optimal, Maximum A Posteriori (MAP) algorithm, is then presented. It will be shown that the use of a precoding technique at the emitter side is applicable to IDMA systems. Several low complexity Multi-User Detector (MUD), based on the Gaussian approximation, will be next discussed. It will be shown that the MUD with Probabilistic Data Association (PDA) algorithm provides faster convergence of the turbo receiver. The discussed turbo receivers will be evaluated by means of Bit Error Rate (BER) simulations and EXtrinsic Information Transfer (EXIT) charts
EXIT Chart Based Joint Code-Rate and Spreading-Factor Optimisation of Single-Carrier Interleave Division Multiple Access
Abstract—In this paper, we consider the joint code-rate and spreading-factor optimisation of turbo-style iterative joint detection and decoding assisted single-carrier interleave division multiple access (SC-IDMA) systems using different-rate convolutional codes and Extrinsic Information Transfer (EXIT) charts, when communicating over Additive White Gaussian Noise (AWGN) channels. More explicitly, we study the extrinsic information exchange between two serial concatenated components and maximise the number of users supported by the SC-IDMA system under the constraint of a fixed bandwidth expansion factor, while maintaining a predefined Bit Error Ratio (BER) versus Eb/N0 performance. We found that an optimum coderate and spreading-factor combination can be found for the SC-IDMA system at low Eb/N0 values, where maintaining a low BER inevitably requires the employment of channel coding. By contrast, at high Eb/N0 the system performs best, when no channel coding is used, i.e. DS-spreading is the only means of bandwidth expansion
Enhanced Trellis Coded Multiple Access (ETCMA)
We propose an enhanced version of trellis coded multiple access (TCMA), an
overloaded multiple access scheme that outperforms the original TCMA in terms
of achieved spectral efficiency. Enhanced TCMA (ETCMA) performs simultaneous
transmission of multiple data streams intended for users experiencing similar
signal-to-noise ratios and can be employed both in the uplink and in the
downlink of wireless systems, thus overcoming one of the main limitations of
TCMA. Thanks to a new receiver algorithm, ETCMA is capable of delivering a
significantly higher spectral efficiency. We show that ETCMA approaches the
capacity of the Additive White Gaussian Noise channel for a wide range of
signal-to-noise ratios.Comment: 5 pages, 5 figure
Provision of Guaranteed QoS with Hybrid Automatic Repeat Request in Interleave Division Multiple Access Systems
Provision of guaranteed quality of service (QoS) in
wireless communication has always been a demanding task. QoS
can be ensured by the mechanism of repeat request, however
real time systems can tolerate only a finite delay. In this paper
we investigate the problem of provision of guaranteed QoS by
hybrid automatic repeat request (HARQ) schemes, based on soft
outputs of a channel decoder. Focus is on adaptive interleavedivision
multiple access (IDMA) transmission. Such a system is
able to provide virtually arbitrary bit error rates (BER).
The proposed HARQ schemes use the reliability information
provided by the channel decoder to decide whether a packet
satisfies the quality of service (QoS) requirements. QoS can be
specified in terms of a minimum required throughput/data rate or
a minimum required BER. Effect of truncation of repeat requests
on the bit error rate and packet throughput is investigated. An
adaptation scheme based upon the bit error rate in the accepted
packets is proposed and the effect of the adaptation on the
effective throughput is demonstrated
Compressed television transmission: A market survey
NASA's compressed television transmission technology is described, and its potential market is considered; a market that encompasses teleconferencing, remote medical diagnosis, patient monitoring, transit station surveillance, as well as traffic management and control. In addition, current and potential television transmission systems and their costs and potential manufacturers are considered
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