dcastro's Lee:H [7 articles]

Abstract

Testing active antennas or polarimetric radar calibrators in the far-field (plane wave excitation) is complicated by imperfect isolation between transmitting and receiving channels. We describe a far-field reflectometry setup which overcomes this problem. A large dynamic range is achieved by modulating the active element bias and using a quadrature receiver and lock-in detection scheme. Measured results compare favorably with other existing techniques ...

Abstract

Convergence between wireless networks is the main trend in current and future wireless communications. The distinct advantage of satellite and terrestrial network integration is the possibility to provide ubiquitous multimedia services in vehicles at any location. The key design considerations of mobile broadband satellite access technologies are given in this article. After presenting the conceptual models of a system and services, the design issues of satellite network synchronization and burst demodulation are described. The design considerations of medium access control, resource ...

Abstract

This paper proposes the novel OFDM transmission scheme that can effectively overcome ISI by adjusting CP length. As a way of combating ISI caused by multipath delay longer than guard interval, interference canceller or powerful channel coding has been proposed. Such approaches may reduce ISI, but it needs much complex computation or considerably decreases transmission efficiency to completely eliminate ISI. In our proposed scheme, CP length can be adaptively controlled by simply adjusting sampling rate. Hence it does neither much increase ...

Abstract

We present two code-acquisition schemes for a multicarrier direct-sequence code-division multiple-access system, one that uses equal gain combining and the other that uses selection combining. The code-acquisition performance of the two multicarrier systems, as well as that of a single-carrier system, are analyzed in both nonfading and Rayleigh fading channels under the assumption that the receiver is chip-synchronized; the effect of partial-band interference (PBI) on the performance is also included. It is demonstrated that in an additive white Gaussian noise channel, ...

Abstract

An adaptive acquisition scheme of PN sequences is presented for DS/SS communications. The basic idea of the scheme is to apply the radar CFAR technique to the acquisition of PN sequences. The detection performance is analysed and an example of adaptive thresholding for multipath Rayleigh fading channels is given ...

Abstract

Since the received signal levels in mobile communications are unknown and the location is varying, acquisition schemes for pseudonoise (PN) sequences with fixed thresholds cannot provide satisfactory performance. This fixed-threshold scheme may cause too many false alarms or result in a low detection probability for a selected threshold value. We present an adaptive acquisition scheme for PN sequences which estimate the background power level, multiply it with a threshold coefficient to keep the false alarms constant, and use it as a ...