Keying

About: Keying is a research topic. Over the lifetime, 6598 publications have been published within this topic receiving 82943 citations.

Real-Time 262-Mb/s Visible Light Communication With Digital Predistortion Waveform Shaping

Abstract: A digital predistortion waveform shaping scheme combined with a blue filter is proposed to optimize both the rise and fall times of a light-emitting diode (LED) and the optical receiver current of the signal of the real-time visible light communication (VLC) system. The proposed scheme is implemented on a field-programmable gate array (FPGA) and a digital-to-analog converter based test bed, which is flexible and reconfigurable by programming the FPGA to match different LED characteristics and varied data rates. A 262-Mb/s non-return-to-zero on-off keying modulation based real-time VLC link with a bit error rate of less than $1.0\times 10^{-6}$ is achieved over a transmission distance of 5.0 m, which uses a single white phosphorous LED with a limited power of 0.1 W.

Token-based distributed generation of security keying material

Abstract: A method and apparatus for delegating distribution of security keying material for the communication path between a mobile entity and a network service function, to the mobile entity. An authorization token is issued to the mobile entity which then supplies security keying material for the communication path. The keying material may be created by the Mobile entity itself. The mobile entity sends the security path material and the authorization token to a network service function. The network service function checks the authorization token to determine if the mobile entity is authorized to create the key material. If so, the received keying material is installed for use in securing the communication path with the mobile entity. The network service function may also be issued with a token to show that it is trusted by the issuer of the token.

On the performance of phase-shift-keying systems

Abstract: Coherent phase-shift keying (CPSK) and differential phase-shift keying (DPSK) are widely used modulation methods in digital communications Bandwidth efficiency, good noise immunity, constant envelope, and simplicity of implementation make these schemes particularly attractive for use over the satellite, terrestrial radio and voiceband telephone channels While system analyses abound in the literature, treatment is usually restricted to the additive Gaussian channel Important issues determining ultimate performance, such as the joint effect of intersymbol interference and the acquisition of carrier phase have not been adequately addressed The main purpose of this paper is to develop analytical tools that can be used to assess system performance under practical operating conditions Pure coherent demodulation schemes such as CPSK are ideals which are rarely achieved in practice, and carrier phase must be estimated prior to and/or during data transmission This requires start-up time, as well as added equipment, and the fidelity of the phase estimate ultimately determines performance In contrast, DPSK is independent of carrier phase, since decisions are made on phase differences However, this comes at a price, and it is known that ideal multiphase DPSK suffers an asymptotic performance penalty of 3 dB in signal-to-noise ratio (s/n) over ideal CPSK We develop a new rigorous method for calculating the error rates of both CPSK and DPSK, under a variety of operating conditions In particular, we find that the intersymbol interference penalty for quaternary DPSK is about 1 dB worse in s/n than for CPSK We demonstrate that the detection efficiency of CPSK approaches the ideal, provided that the s/n of the phase-recovery circuit is about 10 dB more than that at the receiver input Alternatively, for the same s/n, a 10-baud phase-locked loop integration time is required to achieve near-ideal performance

Adaptive Coherent/Non-Coherent Single/Multiple-Antenna Aided Channel Coded Ground-to-Air Aeronautical Communication

Abstract: In this treatise, first of all, we conceive a generic multiple-symbol differential sphere detection (MSDSD) solution for both single- and multiple-antenna-based noncoherent schemes in both uncoded and coded scenarios, where the high-mobility aeronautical Ricean fading features are taken into account. The bespoke design is the first MSDSD solution in the open literature that is applicable to the generic differential space-time modulation (DSTM) for transmission over Ricean fading. In the light of this development, the recently developed differential spatial modulation and its diversity counterpart of differential space-time block coding using index shift keying are specifically recommended for aeronautical applications owing to their low-complexity single-RF and finite-cardinality features. Moreover, we further devise a noncoherent decision-feedback differential detection and a channel-state information estimation aided coherent detection, which also take into account the same Ricean features. Finally, the advantages of the proposed techniques in different scenarios lead us to propose for the aeronautical systems to adaptively: 1) switch between coherent and non-coherent schemes; 2) switch between single- and multiple-antenna-based schemes as well as; and 3) switch between high-diversity and high-throughput DSTM schemes.

A Likelihood-Based Algorithm for Blind Identification of QAM and PSK Signals

Abstract: This paper presents a likelihood-based method for automatically identifying different quadrature amplitude modulations (QAM) and phase-shift keying (PSK) modulations. This algorithm selects the modulation type that maximizes a log-likelihood function based on the known probability distribution associated with the phase or amplitude of the received signals for the candidate modulation types. The approach of this paper does not need prior knowledge of carrier frequency or baud rate. Comparisons of theory and simulation demonstrate good agreement in the probability of successful modulation identification under different signal-to-noise ratios (SNRs). The probability of successful identification results in the simulation results show that under additive white Gaussian noise, the system can identify BPSK, QPSK, 8PSK, and QAMs of order 16, 32, 64, 128, and 256 above 99% accuracy at 4-dB SNR when the two other competing methods available in the literatures cannot for an input signal containing 10 000 symbols and 20 samples per symbol. The simulation results also indicate that when the input signal length decreases, the system needs higher SNRs in order to get accurate identification results. Finally, simulations under different noisy environments indicate that the algorithm is robust to variations of noise environments different from the assumed model in the derivations.