Topic
Keying
About: Keying is a research topic. Over the lifetime, 6598 publications have been published within this topic receiving 82943 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: A hierarchical hypothesis-based theoretical framework has been developed to find the probability of error for the proposed BMC method, which is more robust than the one based on EC and at the same time it requires lower complexity than the maximum likelihood approach.
Abstract: This paper presents a hierarchical hypothesis test and a feature-based blind modulation classification (BMC) algorithm for linearly modulated signals. The proposed BMC method is based on the combination of elementary cumulant (EC) and cyclic cumulants. The EC is used to decide whether the constellations are from real, circular, or rectangular class, which is referred to as macro classifier. The cyclic cumulant is used to classify modulation within a subclass, which is referred to as micro classifier. For the micro classification, we use positions of nonzero cyclic frequencies (symbol rate frequency or carrier frequency) of the received signals. A hierarchical hypothesis-based theoretical framework has been developed to find the probability of error for the proposed classification. The method works over a flat fading channel without any knowledge of the signal parameters. The proposed method is more robust than the one based on EC and at the same time it requires lower complexity than the maximum likelihood approach. To validate the proposed scheme, measurement is carried out in realistic scenarios. The performance of the new algorithm is compared with the existing methods. In this paper, we have considered a six-class problem including binary phase-shift keying, quadrature phase-shift keying (QPSK), offset-QPSK, $\pi$ /4-QPSK, minimum shift keying, and 16-quadrature amplitude modulation.
75 citations
TL;DR: A new non-data-aided estimate is proposed, which makes use of the sixth-order moment of the received data, and which can be tuned for a particular constellation in order to extend the usable range of SNR values.
Abstract: Signal-to-noise ratio (SNR) estimation is an important task in many digital communication systems. With nonconstant modulus constellations, the performance of the classical second- and fourth-order moments estimate is known to degrade with increasing SNR. A new non-data-aided estimate is proposed, which makes use of the sixth-order moment of the received data, and which can be tuned for a particular constellation in order to extend the usable range of SNR values. The advantage of the new method is especially significant for constellations with two different amplitude levels, e.g. 16-amplitude-and-phase-shift keying (16-APSK)
75 citations
TL;DR: The work uses capacitive transducers with a useful bandwidth to transmit digitally coded signals across an air gap in the laboratory, using three of the common methods used in digital communications.
Abstract: The use of ultrasound in air as a means of communicating digital signals is demonstrated. The work uses capacitive transducers with a useful bandwidth to transmit digitally coded signals across an air gap in the laboratory, using three of the common methods used in digital communications. These are on-off keying (OOK), binary frequency-shift keying (BFSK), and binary phase shift keying (BPSK). All three methods are simulated numerically using the available bandwidth of the transducer systems and are compared to results obtained experimentally. It is demonstrated that BPSK can be used to transmit signals with a low bit error rate.
73 citations
26 Apr 2004
TL;DR: In this paper, the Chireix out-phasing method is presented as an alternative to generating amplitude and phase modulated waveforms, which provides a way of improving the efficiency compared to the conventional class A power amplifier.
Abstract: Navy radar operations are being curtailed in a littoral environment. This is due to two factors: the encroachment of cell phone systems into the naval radar bands; in-band interference from other radars. The spectral width of most pulsed radars is significantly wider than necessary with present modulation schemes. Most radars utilize some form of constant envelope pulse with phase or frequency modulation. This causes the spectrum to broaden to several times the information bandwidth. If both the amplitude and phase of the transmitted signal are allowed to change, a significantly narrower bandwidth can be achieved. The paper presents a method to create waveforms with instantaneous bandwidths of 20 MHz confined within -100 dB. The theoretical spectral results of three popular phase modulation schemes (phase shift keying, minimum phase shift keying and derivative phase shift keying) are compared with the spectrally clean results. In addition, the Chireix out-phasing method is presented as an alternative to generating amplitude and phase modulated waveforms. The Chireix method provides a way of improving the efficiency compared to the conventional class A power amplifier. Preliminary results are shown for a spectrally clean waveform.
73 citations
Patent•
05 May 1993
TL;DR: In this paper, a duplex optical fiber connector terminates two single or multi-mode optical fibers of a cable and is adapted to be joined to a receptacle being polarized correspondingly to a keying element of the connector.
Abstract: A duplex optical fiber connector terminates two single or multi-mode optical fibers of a cable and is adapted to be joined to a receptacle being polarized correspondingly to a keying element of the connector. The keying element is slidable into multiple positions so that a recess in the keying element mates with a correspondingly positioned rib of a receptacle. The recess of the keying element is positioned within a channel axially extending on the connector exterior body.
73 citations