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Communication channel

About: Communication channel is a research topic. Over the lifetime, 137411 publications have been published within this topic receiving 1715077 citations. The topic is also known as: communication channel & communications channel.


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Patent
Larry E. Harkins1, Ken Hayward1, Thomas J. Herceg1, Jonathan D. Levine1, David M. Parsons1 
04 Oct 1993
TL;DR: In this article, a receiver profile establishes the properties and mode for receiving of information for receivers on the network and the profile is published in a network repository for all network users or is accessible by selected groups or individuals.
Abstract: A method for a sender to automatically distribute information to a receiver on a network using devices (such as printers and facsimile machines) and communication channels (such as electronic mail) defined in a receiver profile. The receiver profile establishes the properties and mode for receipt of information for receivers on the network and the profile is published in a network repository for all network users or is accessible by selected groups or individuals on the network. Receivers have additional control over network senders by defining an information filter which further controls sender channel access (to a receiver) by defining some channels as having priority of access such as direct or delayed access, as well as selectively permitting senders to override the receiver profile. Consequently, receiver profiles provide a variable receiver definable link to senders using multiple forms of media as well as multiple hardware platforms and network configurations.

390 citations

Journal ArticleDOI
TL;DR: A polynomial time algorithm is proposed under which a channel is assigned to nodes from global, multiple-source broadcasting considerations, and it is shown that the problem of finding an optimal protocol is NP-hard.
Abstract: In this paper we develop a graph-oriented model for dealing with broadcasting in radio networks. Using this model, optimality in broadcasting protocols is defined, and it is shown that the problem of finding an optimal protocol is NP-hard. A polynomial time algorithm is proposed under which a channel is assigned to nodes from global, multiple-source broadcasting considerations. In particular, nodes participating in the broadcast do not interfere with each other's transmissions, but otherwise simultaneous channel reuse is permitted. Protocol implementations of this approach by frequency division and by time division are given. It is shown that, using these protocols, bounded delay for broadcasted messages can be guaranteed.

390 citations

Patent
31 Jul 1998
TL;DR: In this article, a new form of signaling based on precise control of the frequency, amplitude, and phase of the waveform of the signal is proposed, which is a unique signature of the transmitting node preventing security breaches.
Abstract: Nodes on a network are synchronized with each other using a clock transfer system (16). The communications channels between the nodes are then measured (164) and calibrated (163) for optimal bandwidth. The optimized channels and synchronization enable a new form of signaling based on precise control of the frequency, amplitude, and phase of the waveform of the signal. Receiving nodes receive information in order to locate the signal at the frequency, phase and amplitude. Precision control (165, 166) of these parameters also serves as a unique signature of the transmitting node preventing security breaches (162) as the signal's characteristics are unique to the transmitting node. The channel is continuously updated with a precision control system (165, 166) to insure that the nodes are not out of phase.

390 citations

Book ChapterDOI
23 Aug 1985
TL;DR: This work considers a communications scenario in which a transmitter attempts to inform a remote receiver of the state of a source by sending messages through an imperfect communications channel, and considers the deliberate introduction of redundant information into the transmitted message.
Abstract: We consider a communications scenario in which a transmitter attempts to inform a remote receiver of the state of a source by sending messages through an imperfect communications channel. There are two fundamentally different ways in which the receiver can end up being misinformed. The channel may be noisy so that symbols in the transmitted message can be received in error, or the channel may be under the control of an opponent who can either deliberately modify legitimate messages or else introduce fraudulent ones to deceive the receiver, i.e., what Wyner has called an "active wiretapper" [1]. The device by which the receiver improves his chances of detecting error (deception) is the same in either case: the deliberate introduction of redundant information into the transmitted message. The way in which this redundant information is introduced and used, though, is diametrically opposite in the two cases.For a statistically described noisy channel, coding theory is concerned with schemes (codes) that introduce redundancy in such a way that the most likely alterations to the encoded messages are in some sense close to the code they derive from. The receiver can then use a maximum likelihood detector to decide which (acceptable) message he should infer as having been transmitted from the (possibly altered) code that was received. In other words, the object in coding theory is to cluster the most likely alterations of an acceptable code as closely as possible (in an appropriate metric) to the code itself, and disjoint from the corresponding clusters about other acceptable codes.

389 citations

Journal ArticleDOI
TL;DR: This work derives the expected intersymbol/interchannel interference of such a nonorthogonal FDM (NOFDM) system under the assumption of a wide-sense stationary uncorrelated scattering (WSSUS) channel and compares OFDM and NOFDM schemes with regard to robustness against delay/Doppler spread.
Abstract: A new approach to multicarrier digital communication over time-varying, frequency selective fading channels is presented. We propose a transmission signal set whose basic structure is similar to standard orthogonal frequency division multiple access (OFDM)-setups, i.e., a system of functions generated by time and frequency-shifted versions of a pulse-like prototype function known as a Weyl-Heisenberg (WH) system. Unlike previous OFDM studies, however, which are restricted to the case of orthonormal pulses, we consider nonorthogonal pulses that are adapted to realistically available a priori knowledge of the channel. Perfect transmultiplexing in the case of an ideal channel is incorporated as a mathematical side-constraint. We derive the expected intersymbol/interchannel interference of such a nonorthogonal FDM (NOFDM) system under the assumption of a wide-sense stationary uncorrelated scattering (WSSUS) channel. Based on this result, we compare OFDM and NOFDM schemes with regard to robustness against delay/Doppler spread.

388 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202270
20214,425
20206,535
20197,160
20187,052
20176,315