Keying

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

Indoor Positioning in High Speed OFDM Visible Light Communications.

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 of single carrier modulation scheme, i.e., on-off keying (OOK) modulation. We demonstrate that OFDM positioning system outperforms its conventional counterpart.

Impact of Pump-Phase Modulation on FWM-Based Wavelength Conversion of D(Q)PSK Signals

Abstract: We investigate both theoretically and experimentally the impact of pump-phase modulation on differential phase shift keying (DPSK) and differential quadrature phase shift keying (DQPSK) signals in fiber-based parametric wavelength converters. It will be shown that the pump-phase modulation used to suppress stimulated Brillouin scattering introduces critical signal degradations and optical SNR penalties on DPSK signals, and more severe on DQPSK signals. Different modulation schemes will be theoretically investigated and the quantitative results are compared to system experiments. Finally, the theoretical results for a single conversion will be extended to multiple conversions to study the cascadability of the wavelength converter.

Secrecy Capacity of Space Keying with Two Antennas

Abstract: Spatial modulation (SM) and space shift keying (SSK) use only one out of several transmit antennas at a time to transmit data via an antenna index. In such a system, the information is encoded by exploiting channel randomness i.e. the fact that channels between different transmit and receive antennas are random. This difference is used to distinguish among the transmit antennas. While SSK uses only antenna index to transmit data, SM also uses ordinary signal modulation. In wireless secrecy systems, one of the key performance measures is secrecy capacity. It specifies the rate at which the transmitter can communicates on the main link to the desired receiver while this information cannot be decoded by the eavesdropper. We investigate SM and SSK in the context of wireless secrecy capacity when the underlying modulation and the difference between the legitimate and eavesdropper signal to noise ratios (SNRs) are varied.

Composite-shift-keying communication equipment

Abstract: 57 A Composite Shift Keying (CSK) modulation technique is described which provides enhanced error detection capability in a noisy transmission medium, such as an AC power line. A modulation binary signal causes the generation of two or three possible transmitted signals, and when the modulating binary signal is idle, no signal is transmitted. When the modulating signal is active, a single frequency qualifying signal (of radian frequency Wqt) is transmitted. If the active binary signal is a logical (0), an additional single frequency (of radian frequency WO) is transmitted along with Wqt. If the active binary signal is a logical (1), a different single frequency (of radian freqency W1) is transmitted with Wqt.

Performance analysis of a JTIDS/Link-16-type waveform transmitted over Nakagami fading channels with pulsed-noise interference

Abstract: The Joint Tactical Information Distribution System (JTIDS) is the communication terminal of Link-16. JTIDS is a hybrid direct sequence/frequency-hopping spread spectrum system and features Reed-Solomon codes for channel coding, cyclic code-shift keying for 32-ary symbol modulation, minimum-shift keying for chip modulation, symbol interleaving, chip sequence scrambling and random jittering for transmission security, and a double-pulse structure for diversity. Assuming that coherent chip demodulation is practical, we investigate the probability of symbol error of a JTIDS/Link-16-type waveform for both the single- and the double-pulse structure transmitted over a slow, flat Nakagami fading channel in the presence of pulsed-noise interference (PNI) in this paper. In general, the results show that the double-pulse structure always outperforms the single-pulse structure, whether the PNI is present or not and whether the channel is fading or not. Furthermore, barrage noise interference has the most effect in degrading performance when signal-to-interference ratio (SIR) is small. When SIR is large, PNI with a smaller fraction of time that interference is on causes the greatest degradation.