Topic
Keying
About: Keying is a research topic. Over the lifetime, 6598 publications have been published within this topic receiving 82943 citations.
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TL;DR: This paper investigates the error performance for convolutional coded on-off keying free-space optical systems through symbol by symbol interleaved channels characterized by strong turbulence and/or pointing error effects and derives exact analytical expressions for the pairwise error probability.
Abstract: The performance of optical wireless systems deteriorates to a large extent from the presence of turbulence and pointing error effects. To meet the typical bit error rate (BER) targets for reliable communications within the practical ranges of signal-to-noise ratio, error control coding schemes are often proposed. This paper investigates the error performance for convolutional coded on-off keying free-space optical systems through symbol by symbol interleaved channels characterized by strong turbulence and/or pointing error effects. We consider several channel types and derive exact analytical expressions for the pairwise error probability. These expressions are applied to obtain upper bounds on the BER performance using the transfer function technique.
44 citations
TL;DR: A system based on sequential decoding and utilizing binary phase-shift keying and 8-level quantized decisions is proposed for deep-space communication and an analysis included of the required phase reference signal-to-noise ratio.
Abstract: A system based on sequential decoding and utilizing binary phase-shift keying and 8-level quantized decisions is proposed for deep-space communication. Theoretical analyses augmented by a program of computer Simulation promise operation within 3-4 dB of the channel capacity of an infinite bandwidth additive white Gaussian noise channel. A low probability of erasure is achieved by the suggested use of occasional off-line decoding. A negligible probability of error is readily achieved. Channel coherence is examined and quadratic and decision-directed methods of achieving a phase reference are compared. Extensive symbol interleaving is suggested and an analysis included of the required phase reference signal-to-noise ratio.
44 citations
TL;DR: The primary finding was that keypads with square keys resulted in improved speed and a higher degree of accuracy than do keypad with regular keys (either a long horizontal dimension or a longer vertical dimension).
Abstract: This paper reports on a study comparing keying accuracy and speed for eight different numeric keypad configurations on a touch screen. Using touch-sensitive keypads displayed on a computer terminal, operators entered numbers presented to them through a speech synthesizer. Dependent measures collected were keying rates, errors, and the x- and y-dimension standard deviations from the centre point of the key. The primary finding was that keypads with square keys resulted in improved speed and a higher degree of accuracy than do keypads with regular keys (either a long horizontal dimension or a longer vertical dimension). Spread-out versions of the keypads (inter-key spacing = 1·3 cm) did not yield superior performance compared with compressed versions (inter-key spacing = 0·6 cm).
43 citations
TL;DR: Spectral regrowth and error vector magnitude measurements indicate that the chip can support at least 20-MSym/s quadrature phase-shift keying and binary phase- shift keying modulation at an output power of +5 dBm per channel.
Abstract: This paper presents a four-element X-band phased-array transmitter in 0.13-μm CMOS. The design is based on the all-RF architecture and contains a 5-bit phase shifter (lowest bit is used as a trim bit), 4-bit gain control (to reduce the rms gain error), and power amplifiers capable of delivering a PSAT of 13.5 dBm per channel at 8.5-10.5 GHz. The chip can be used in the linear mode for communication systems and in the saturated mode for frequency-modulated continuous-wave radar systems, and therefore, extensive analysis is done on the phase shifter distortion versus input power. Spectral regrowth and error vector magnitude measurements indicate that the chip can support at least 20-MSym/s quadrature phase-shift keying and binary phase-shift keying modulation at an output power of +5 dBm per channel. Packaging techniques based on chip-on-board and quad flat no-lead (QFN) modules have been implemented with the four-channel chip, and both show a nearest neighbor coupling of -30 dB at 8-10 GHz, limited by bond-wire coupling. The chip dimensions are 2.9×3.0 mm2 and it consumes 870 mW from 2- and 3-V power supplies.
43 citations
TL;DR: A new decoding scheme to reduce mutual interference which makes use of the well-defined algebraic structure of the users' addresses is described, allowing a 50 to 60 percent increase in the number of users who can simultaneously share the system at a given error rate.
Abstract: We have recently examined, for possible application to digital mobile radio telephony, a digital spread-spectrum technique employing multiple frequency-shift keying (MFSK) modulation with code-division-multiple access (CDMA) by frequency-hopping over a common bandwidth. The system uses the cellular approach where all mobiles within a cell communicate with a fixed base station in the cell. An analysis of base-to-mobile transmission shows that mutual interference limits the number of users which the system can accommodate at a given error rate. This paper describes a new decoding scheme to reduce mutual interference which makes use of the well-defined algebraic structure of the users' addresses. Analysis of the new decoder at high signal to noise (s/n) ratio shows it to outperform conventional decoding, allowing a 50 to 60 percent increase in the number of users who can simultaneously share the system at a given error rate. We describe a simple implementation of the decoder using shift registers.
43 citations