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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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Patent
01 Feb 1994
TL;DR: In this article, a communication system for transmitting data to mobile receivers utilizing a subcarrier within a commercial FM channel of a radio station is described, where the data transmitted is first encoded in encoder (112), utilizing a forward error correction code.
Abstract: A communication system (100) is provided for transmitting data to mobile receivers utilizing a subcarrier within a commercial FM channel of a radio station (55). The data transmitted is first encoded in encoder (112), utilizing a forward error correction code. The sequence of the encoded data is altered in interleaver (116), subdivided into a plurality of subframes, in framing and synchronization circuit (120), which also adds channel state bits to each subframe. The framed data is modulated onto the subcarrier in the differential quadrature phased shift keying modulator (130), the output of which is coupled to the FM modulator (52) of radio station transmitter (50). The transmitted radio frequency signals may be received by a vehicle antenna (12) for coupling to the vehicle's FM receiver (80). The modulated subcarrier is recovered from the FM demodulator (84) of the receiver (80), the modulated subcarrier being demodulated to recover the encoded digital data therefrom. The channel state bits included with the data are extracted from the digital data and utilized to form a data reliability factor for each bit of the encoded data. The data reliability factors thus obtained are associated with each bit of the data in a deinterleaver (360). Deinterleaver (360) provides each data bit in proper sequence, with its associated data reliability factor to a decoder (370). The decoded digital data is provided to a vehicle traffic computer (90) for processing and presentation of traffic information to a user on a display (92).

45 citations

Proceedings ArticleDOI
01 Jan 2016
TL;DR: This paper investigates the indoor positioning accuracy of optical based OFDM techniques used in VLC systems and demonstrates that OFDM positioning system outperforms its conventional counterpart.
Abstract: Visible Light Communication (VLC) technology using light emitting diodes (LEDs) has been gaining increasing attention in recent years as it is appealing for a wide range of applications such as indoor positioning. Orthogonal frequency division multiplexing (OFDM) has been applied to indoor wireless optical communications in order to mitigate the effect of multipath distortion of the optical channel as well as increasing data rate. In this paper, we investigate the indoor positioning accuracy of optical based OFDM techniques used in VLC systems. A positioning algorithm based on power attenuation is used to estimate the receiver coordinates. We further calculate the positioning errors in all the locations of a room and compare them with those using single carrier modulation scheme, i.e., on-off keying (OOK) modulation. We demonstrate that OFDM positioning system outperforms its conventional counterpart.

45 citations

Proceedings ArticleDOI
M. Ohm1
01 Jul 2004
TL;DR: Spectral properties of 8-DPSK and chromatic dispersion tolerance are investigated and a differential 8-level phase-shift keying modulation format with a simple new receiver for transmission of 3 bit/symbol is presented.
Abstract: This paper presents a differential 8-level phase-shift keying (8-DPSK) modulation format with a simple new receiver for transmission of 3 bit/symbol. The receiver with direct detection is based on a differential quadrature phase-shift keying (DQPSK) receiver with binary decision devices and a combinational network for estimating the transmitted bit sequences from the detected multilevel electrical signals. The 8-DPSK transmitter is based on a differential quadrature phase-shift keying (DQPSK) transmitter with an additional phase modulator. Spectral properties of 8-DPSK and chromatic dispersion tolerance are investigated.

45 citations

Proceedings ArticleDOI
08 Jun 2006
TL;DR: A comprehensive system design for cognitive radio is presented and it is proposed to transmit the spectrum sensing related information via on-off keying (OOK) modulated ultrawideband (UWB) and a processing gain based approach that leads to an increased range for cognitive networks.
Abstract: The rising number and capacity requirements of radio systems bring about an increasing demand for frequency spectrum. Cognitive radio offers a tempting solution to this problem by proposing opportunistic usage of frequency bands that are not occupied by their licensed users. Since it is a rather new concept, there is no consensus on the practical implementation of cognitive radio communications. In this paper, a comprehensive system design for cognitive radio is presented. The details of spectrum sensing and dynamic spectrum shaping, which constitute the basics of opportunistic spectrum usage, are given. It is proposed to transmit the spectrum sensing related information via on-off keying (OOK) modulated ultrawideband (UWB). The limits on the range of one-to-one cognitive communications are discussed. A processing gain based approach that leads to an increased range for cognitive networks is proposed. Different signaling options for the real data communications are given, and among these options an impulse radio that employs raised cosine filters is investigated in detail.

45 citations

Patent
27 Dec 2001
TL;DR: In this article, a sigma-delta N-phase keying modulator with non-uniform polar quantization is described, where a quantiser produces a quantised output so that it represents a symbol, selected from a set of N symbols.
Abstract: The invention relates to a sigma-delta N-phase keying modulator having non-uniform polar quantisation. According to one embodiment of the invention, a quantiser produces a quantised output so that it represents a symbol, selected from a set of N symbols, depending on to which of the N non-symmetric cells, covering the complex plane in a non-overlapping manner, the phase of said symbol belongs. This may reduce the occurrence of larger phase transitions, which may lead to increased efficiency. The selection of non- symmetric cell boundaries may also affect the noise shaping spectrum of a sigma-delta N-PSK modulator. The invention also relates to an N-phase keying modulation method and a mobile telephone or transmitter including the modulator described above.

44 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023137
2022286
2021170
2020238
2019301
2018291