Keying

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

On the effect of cochannel interference on average error rates in Nakagami-fading channels

Abstract: The effect of cochannel interference on the performance of digital mobile radio systems in a Nakagami-fading channel is studied. Closed-form expressions are derived for the average probability of error of both coherent and noncoherent (differentially coherent) binary frequency shift keying and phase-shift keying schemes in an interference-limited system. The analysis assumes an arbitrary number of independent and identically distributed Nakagami interferers. The effect of maximal ratio combining diversity is also examined.

Type-Based Sign Modulation and Its Application for ISI Mitigation in Molecular Communication

Abstract: While ISI is a common issue in classical communications, it is more challenging and prominent in the context of molecular communication, because one cannot readily combat ISI with classical channel equalization techniques. This is due to the fact that transmitter can only release a positive amount of concentration of a specific molecule into the medium. Previous works have proposed use of chemical reactions to remove molecules from the environment, and to effectively simulate negative signals. However, the differential equation describing a diffusion-reaction process is non-linear. This precludes the possibility of using Fourier transform tools. In this paper, a solution for simulating negative signals based on the diffusion-reaction channel model is proposed. While the proposed solution does not exploit the full degrees of freedom available for signaling in a diffusion-reaction process, but its end-to-end system is a linear channel and amenable to Fourier transform analysis. Based on our solution, a modulation scheme and a precoder are introduced and shown to have a significant reduction in error probability compared with previous modulation schemes, such as concentration shift keying (CSK), pre-equalization, depleted-molecule shift keying (D-MoSK), and molecular concentration shift keying (MCSK). The effects of various imperfections (such as quantization error) on the communication system performance are studied.

A differential scheme for Spatial Modulation

Abstract: In this paper, by considering the case of two transmit antennas, we propose a novel approach for introducing differential signaling into Spatial Modulation (SM)/Space-Shift Keying (SSK) and thus develop a differential SM/SSK (DSM/DSSK) scheme, where neither the transmitter nor the receiver has access to channel state information. The proposed approach can be applied to any equal energy signal constellations. Performance analysis of the proposed DSM is developed analytically and demonstrated via simulations, leading to some interesting observations and useful conclusions. It is shown that the performance degradation of DSM over SM can be less than 3dB and that the loss decreases as the number of receive antennas decreases.

Format Conversion of Optical Multilevel Signals Using FWM-Based Optical Phase Erasure

Abstract: An optical format conversion scheme of multilevel phase-shift keying (M-ary PSK) signals using the four-wave mixing based optical phase erasure is discussed in this paper. The conversion from differential quadrature phase-shift keying (DQPSK) to differential phase shift keying at 10 and 160 Gbaud, and the conversion from differential eight-ary phase-shift keying to DQPSK at 40 Gbaud have been experimentally demonstrated. The proposed scheme could be used as a phase erasure, in which a redundant tributary of the M-ary PSK signal is removed, or as an “updater” where the unwanted phase pattern is replaced with the new pattern.

Spectral shaping of UWB signals for time-hopping impulse radio

Abstract: This paper studies the design of signaling waveforms for time-hopping impulse radio (TH-IR) with limits on the power spectral density. Such restrictions are imposed by the spectral mask prescribed by frequency regulators for ultra-wideband (UWB) signals. The "conventional" TH-IR system with pulse-position modulation and time-hopping multiple access gives rise to spectral lines that either violate the regulations, or require a significant power backoff. To remedy this situation, we propose the use of polarity randomization, which eliminates the spectral lines and also leads to a smoothing of the continuous part of the spectrum. We analyze different variants of the polarity randomization, considering short and long randomization sequences, as well as symbol-based or pulse-based randomization. We analyze the effect of this technique on both pulse position modulation and binary phase-shift keying modulation.