Keying

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

Performance of an RCPC-coded OFDM-based digital audio broadcasting (DAB) system

Abstract: A system proposal for DAB is investigated. The kernel is orthogonal frequency division multiplexing (OFDM) with 4-DPSK (differential phase shift keying) modulation, rectangular pulse-shaping, and a guard interval to reject multipath distortions. Emphasis is on the use of source-adapted channel coding with rate-compatible punctured convolutional (RCPC) codes. Based on analytical and simulated BER (bit error rate) curves for several propagation conditions and on preliminary source significance information (SSI), a static code design with unequal error protection (UEP) is presented that also takes auxiliary data services into account. The gain due to UEP is on the order of 8dB in signal power or 25% in bandwidth. >

Effect of avalanche photodiode and thermal noises on the performance of binary phase-shift keying- subcarrier-intensity modulation/free-space optical systems over turbulence channels

Abstract: In this study, the authors theoretically study the performance of direct-detection free-space optical communication systems using binary phase-shift keying subcarrier-intensity modulation and avalanche photodiode (APD). The system bit-error rate and channel capacity are theoretically derived in cases of log-normal and gamma-gamma channel models for weak-to-moderate and moderate-to-strong atmospheric turbulence conditions, respectively. The authors quantitatively discuss the optimal values of the APD average gain, required transmitted optical power, and operating bit-rate considering various turbulence conditions, APD shot noise and thermal noise. It is seen that, although the impact of turbulence is severe, a proper selection of APD average gain could significantly improve the system performance in both cases of turbulence channels. The optimal value of APD average gain remains almost the same for different levels of turbulence; nevertheless it varies significantly in accordance to the change of receiver noise temperature.

Digital transmission through a land mobile satellite channel

Abstract: An analytical derivation of the probability of bit error noncoherent frequency-shift keying (FSK) and coherent phase-shift keying (PSK) signals transmitted through a land-mobile satellite channel is described. The channel characteristics used in the analysis are based on a recently developed model which includes the combined effects of fading and shadowing. Analytical expressions for the probability of bit error of FSK and coherent phase-shift keying (CPSK) signals are obtained. The results show that large amounts of signal-to-noise ratio (SNR) are required to compensate for the combined effect of fading and shadowing. An analytical expression for the irreducible probability of bit error of a CPSK signal due to phase variations caused by fading and shadowing is derived. The results described should be useful in the design of land mobile satellite communication systems. >

Performance of interleaved trellis-coded differential 8-PSK modulation over fading channels

Abstract: The performance of trellis-coded differential octal phase-shift keying (coded 8-DPSK) with differentially coherent detection and soft-decision Viterbi decoding is investigated. A suitable receiver is presented whose signal processing is based on Nyquist signaling, requiring only one complex sample per modulation interval. Symbol synchronization and automatic frequency control are performed in a decision-directed way. Bit-error-rate (BER) performance over Gaussian, Rayleigh, and Rician channels is determined by means of computer simulations. The performance of coded 8-DPSK on the Gaussian channel is shown for a four-state convolutional trellis code. The unquantized outputs of up to three symbol detectors with delays of 1, 2, and 3 symbol periods are used for metric computation. The coding gain which includes losses due to timing and frequency synchronization errors is found to be 2.5 dB at BER=10/sup -5/ with respect to uncoded 4-DPSK. Much larger gains are achieved for fading channels if interleaving is applied. Using an eight-state trellis code the performance is determined on Rayleigh and Rician channels for various Doppler spreads and interleaver sizes. >

Detecting and Receiving Phase Modulated Signals with a Rydberg Atom-Based Mixer.

Abstract: Recently, we introduced a Rydberg-atom based mixer capable of detecting and measuring the phase of a radio-frequency field through the electromagnetically induced transparency (EIT) and Autler-Townes (AT) effect. The ability to measure phase with this mixer allows for an atom-based receiver to detect digital modulated communication signals. In this paper, we demonstrate detection and reception of digital modulated signals based on various phase-shift keying approaches. We demonstrate Rydberg atom-based digital reception of binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), and quadrature amplitude (QAM) modulated signals over a 19.626~GHz carrier to transmit and receive a bit stream in cesium vapor. We present measured values of Error Vector Magnitude (EVM, a common communication metric used to assess how accurate a symbol or bit stream is received) as a function of symbol rate for BPSK, QPSK, 16QAM, 32QAM, and 64QAM modulation schemes. These results allow us to discuss the bandwidth of a Rydberg-atom based receiver system.