This letter addresses the edge effect on a windowed discrete Fourier transform (WDFT)-based channel estimator for orthogonal frequency division multiplexing (OFDM) systems with virtual carriers in non-sample spaced channels and derives a sufficient condition to reduce the edge effect. Moreover, a modified WDFT-based channel estimator with multi-step linear prediction as an edge effect reduction technique is proposed. Simulation results show that it offers around 5 dB signal-to-noise ratio (SNR) gain over the conventional WDFT-based channel estimator at bit error rate (BER) of 10-3.

This letter presents an efficient blind carrier frequency offset (CFO) estimate approach for multicarrier-code division multiple access (MC-CDMA) system. It can reduce the searching grids required and improve the CFO estimating accuracy compared with conventional searching-based algorithms. Simulation results are provided for illustrating the effectiveness of the proposed blind estimate approach.

In this letter, we present a blind carrier frequency offset (CFO) estimator by exploiting the subspace-based technique for multicarrier-code division multiple access (MC-CDMA) systems. Relative high accuracy and low-complexity to the CFO estimation can be achieved by rooting a polynomial. Simulation results are provided for illustrating the effectiveness of the proposed blind polynomial rooting estimator.

We propose a DOA-Matrix based blind CFO estimation method for a MIMO-OFDM system with Virtual Carriers. The method estimates CFO in closed-form by jointly exploiting the shift-invariant structure of time-domain signal received on multiple receive antennas. In contrast to previous training-based methods, the proposed method is bandwidth efficiency. We also present numerical simulation results for different transmit and receive antenna configurations and for different record lengths.

Two simple frequency offset estimators based on projection approaches for multicarrier code-division multiple access systems are proposed, without using specific training sequences. It is not only can estimate and correct frequency offset, but also has less computational load. Several computer simulations are provided for illustrating the effectiveness of the blind estimate approaches.

This paper describes the numerical analysis for terahertz electromagnetic-wave oscillation/detection properties of plasma-wave field-effect transistors (PW-FET's) and their applications to future smart photonic network systems. The PW-FET is a new type of the electron device that utilizes the plasma resonance effect of highly dense two-dimensional conduction electrons in the FET channel. By numerically solving the hydrodynamic equations for PW-FET's, the plasma resonance characteristics under terahertz electromagnetic-wave absorption are analyzed for three types of FET's; Si MOSFET's, GaAs MESFET's, and InP-based HEMT's. The results indicate that the InP-based sub-100-nm gate-length HEMT's exhibit the most promising oscillation/detection characteristics in the terahertz range with very wide frequency tunability. By introducing the PW-FET's as injection-locked terahertz-frequency-tunable oscillators and terahertz mixers, a new idea of coherent heterodyne detection utilizing terahertz IF (intermediate-frequency) bands is proposed for the future smart photonic network systems that enable real-time adaptive wavelength routing for add-drop multiplexing. The plasma resonance of PW-FET's by means of different frequency generation based on direct photomixing is also proposed as an alternative approach to injection-locked terahertz oscillation. To realize it, virtual carrier excitations by the polariton having photon energy lower than the bandgap of the channel is a possible mechanism.