Keying

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

Accurate performance evaluation of time-hopping and direct-sequence UWB systems in multi-user interference

Abstract: An exact analysis is derived for precisely calculating the bit error probability of time-hopping and direct-sequence ultra-wideband systems with multi-user interference in an additive white Gaussian noise environment. The analytical expressions are validated by simulation and used to assess the accuracy of the Gaussian approximation proposed for estimating the performance of ultra-wideband communication systems. The Gaussian approximation is shown to be inaccurate for predicting the bit error rate for medium and large signal-to-noise ratio values. The performances of time-hopping and direct-sequence modulation schemes are accurately compared for different numbers of users and frame widths. It is shown that direct-sequence binary phase-shift keying outperforms time-hopping binary phase-shift keying for medium and large values of signal-to-noise ratio, which contradicts some previous results obtained using a Gaussian approximation.

Compensation of intra-channel nonlinear fibre impairments using simplified digital back-propagation algorithm

Abstract: We investigate a digital back-propagation simplification method to enable computationally-efficient digital nonlinearity compensation for a coherently-detected 112 Gb/s polarization multiplexed quadrature phase shifted keying transmission over a 1,600 km link (20x80km) with no inline compensation. Through numerical simulation, we report up to 80% reduction in required back-propagation steps to perform nonlinear compensation, in comparison to the standard back-propagation algorithm. This method takes into account the correlation between adjacent symbols at a given instant using a weighted-average approach, and optimization of the position of nonlinear compensator stage to enable practical digital back-propagation.

Digital Modulation Techniques

Abstract: First considers the three basic forms of digital modulation: amplitude-shift-keying, frequency-shift keying, and phase-shift keying Compares binary modulation systems, in terms of power efficiency and spectrum efficiency Explains the principle of quadrature modulation used with M-ary PSK Describes three modulation techniques that offer certain advantages for band-limited, nonlinear channels: offset quadrature phase-shift keying, QPSK, and minimum-shift keying Explains how the technique of quadrature partial response increases the bandwidth efficiency of OAM signaling Describes trellis coded modulation as a combination of convolutional coding and digital modulation, and show an example in detail Shows the principles behind orthogonal frequency-division multiplexing (OFDM) Compares digital modulation techniques in terms of error performance, complexity of implementation, and all bandwidth efficiency

System and method for trusted path communications

Abstract: A system and method for identifying and authenticating users and for controlling the access of those users to privileged instructions within a data enclave The data enclave includes a plurality of controllers, such as workstations, connected over a network to a security server; each data enclave is assigned a cryptographic key A personal keying device having an encrypted user unique identifier is assigned to each user; provisions are made for temporarily connecting the personal keying device to one of the controllers and for transmitting an encrypted message, including the user unique identifier and the last countersign, to the security server to authenticate the user and establish his/her access rights A mechanism for updating the countersign is provided so that trusted path communications can be established between the user and the security server

An impulse radio asynchronous transceiver for high data rates

Abstract: The purpose of this paper is to provide an operative way of achieving high data rates for impulse radio (IR) transmission based systems. Since applications targeted for ultra wide band (UWB) are liable to be low-cost, we especially focus on simple transceiver design. To that effect, we present an original demodulation scheme adapted to a multi-band ON-OFF keying modulation. From the receiver point of view, we impose relaxed channel estimation constraints and derive suitable signal processing schemes and simple hardware architectures. Indeed, we only consider the benefit from a limited a priori channel knowledge: approximative delay spread and energy level. The associated optimum demodulation turns out to be a non-trivial energetic threshold comparison whose precise theoretical computation admits an analytical solution proving its feasibility. Numerical results are eventually performed for IEEE 802.15.3a channel models and FCC requirements; they obviously demonstrate the potential of these techniques.