OFDM Receiver Performance Analysis with Measured Channel Model for Power Line Communication

This paper reports the results of wideband channel measurements conducted on in house outlets. Two kinds of channel measurements were performed: impulse response measurements and noise signal measurements. In measure based channel model, preamble assisted orthogonal frequency-division multiplexing access (OFDM) receiver scheme is proposed for differential phase shift keying (DPSK) and quadrature amplitude modulation (QAM). Timing synchronization and channel estimation is performed using the preamble. We provide numerical results to illustrate the performance of OFDM receiver in measure based channel model

OFDM receiver performance analysis with measured power line channel model for coded OFDM system

This paper reports the results of wideband channel measurements conducted on in apartment environments. Two kinds of channel measurements were performed: impulse response measurements and noise signal measurements. In measure based channel model, the performance degradation is analyzed due to timing synchronization and colored noise in orthogonal frequency division multiplexing (OFDM) based power line communication (PLC) systems and then proceeds to propose a new receiver scheme for channel estimation and soft decision decoding scheme under imperfect channel estimation. Simulation results show that the proposed algorithm can efficiently eliminate the effects of imperfect channel estimation and colored noise for coded OFDM system

Hard X-ray free-electron laser with femtosecond-scale timing jitter

The hard X-ray free-electron laser at the Pohang Accelerator Laboratory (PAL-XFEL) in the Republic of Korea achieved saturation of a 0.144 nm free-electron laser beam on 27 November 2016, making it the third hard X-ray free-electron laser in the world, following the demonstrations of the Linac Coherent Light Source (LCLS) and the SPring-8 Angstrom Compact Free Electron Laser (SACLA). The use of electron-beam-based alignment incorporating undulator radiation spectrum analysis has allowed reliable operation of PAL-XFEL with unprecedented temporal stability and dispersion-free orbits. In particular, a timing jitter of just 20 fs for the free-electron laser photon beam is consistently achieved due to the use of a state-of-the-art design of the electron linear accelerator and electron-beam-based alignment. The low timing jitter of the electron beam makes it possible to observe Bi(111) phonon dynamics without the need for timing-jitter correction, indicating that PAL-XFEL will be an extremely useful tool for hard X-ray time-resolved experiments.1143Nsciescopu