Hyung-Rae Park

Performance analysis of the hybrid search code acquisition technique for cellular CDMA systems

The hybrid search algorithm, a combination of the maximum-likelihood search and serial search algorithms, is one of the most promising techniques that can be used for code acquisition in CDMA forward links. The hybrid search code acquisition system considered in this paper employs two operating modes, i.e., search and verification modes with M-parallel correlators used for maximum-likelihood detection in search mode. An analytical expression for the mean acquisition time is first obtained. The probabilities of detection, miss, and false alarm are also derived for both search and verification modes for frequency-selective Rayleigh fading environments with assumption that the fading envelope of the received signal is constant over the interval of post-detection integration (PDI). Numerical evaluation shall be performed to investigate the effects of sub-window size, number of post-detection integration in search and verification modes, and so on, in the forward link of cellular CDMA networks.

A novel ESD protection technique for submicron CMOS/BiCMOS technologies

In this paper, we present a novel electrostatic discharge (ESD) protection device. When an ESD pulse attacks, this device is activated as either a reverse-biased punchthrough BJT or a forward-biased diode, depending on the polarity of the input pulse. Experimental results (based on the Human-Body Model) show that the new protection device is more efficient and area-effective than any other conventional one. It does not require any extra mask for its implementation because of the compatibility with established processes. Thus we believe that it is a viable approach for the protection of submicron CMOS/BiCMOS devices and circuits vulnerable to ESD stress.

Design and performance analysis of a noncoherent code tracking loop with variable loop bandwidth

In this paper, the performance of a noncoherent DLL code tracking loop with a variable loop bandwidth is analyzed in detail and some practical design issues for loop filter are discussed. First, an analytical closed-form expression on steady-state jitter variance is derived as a function of a pulse-shaping filter, timing offset, signal-to-interference ratio, and a loop bandwidth. A noncoherent code tracking loop with a variable loop bandwidth is then designed for application to WCDMA mobile stations and its performance is verified by computer simulation.

Performance analysis of the adaptive hybrid search code acquisition algorithm for cellular CDMA systems

The hybrid search algorithm, a combination of the maximum-likelihood search and serial search algorithms, is known as one of the most promising techniques that can be used for code acquisition in CDMA forward links. An efficient adaptive hybrid search code acquisition algorithm with embedded CFAR is designed in this paper, which employs two operating modes, i.e., search and verification modes with M-parallel correlators used for maximum-likelihood detection in search mode. An analytical expression for the mean acquisition time is obtained and the exact expressions on the probabilities of detection, miss, and false alarm are derived for slowly varying frequency-selective Rayleigh fading environments. Numerical evaluation shall be performed to investigate the effects of sub-window size, number of post-detection integration, and so on, in the forward link of cellular CDMA networks.

Performance analysis of an adaptive hybrid search code acquisition technique in the case of multiple pilot signals

The performance of an adaptive hybrid search code acquisition technique is analyzed for CDMA cellular networks in the case of multiple pilot signals. An analytical expression for the mean acquisition time is first derived. The probabilities of detection, miss, and false alarm are then derived for frequency-selective Rayleigh fading environments with assumption that the fading envelope of a received signal is constant over the interval of post-detection integration (PDI). The performance of the adaptive hybrid search code acquisition technique is evaluated numerically in terms of the mean acquisition time according to the sub-window size, number of PDIs.

A new adaptive polarization-space-time domain radar target detection algorithm for nonhomogeneous clutter environments

A new adaptive radar target detection algorithm, called the polarization-space-time localized generalized likelihood ratio (PSTL-GLR) test shall be exploited, which is of significant use in nonhomogeneous clutter environments. The key idea of the PSTL-GLR algorithm is that the degree of freedom (DOF) is controlled to avoid a serious detection loss due to limited secondary data vectors by transforming the data from space-time domain to angle-Doppler domain, while maintaining high performance of the joint polarization-space-time processing. The detection performance of the proposed algorithm is derived analytically in terms of the probabilities of detection and false alarm, along with numerical evaluation to illustrate its efficiency in limited secondary data environments.

Channel Capacity of MIMO Wideband CDMA System under the Imperfect Channel Estimation and Near/Far Effect

The channel capacity of multiple-input multiple-output (MIMO) wideband CDMA system with coherent RAKE receiver is considered. General multi-path intensity Nakagami fading and multiple-access near/far interference channel are assumed. The analysis for system performance shows that the error of channel estimation significantly degrades BER performance and can be effectively suppressed by RAKE receiver and MIMO schemes. Also, an attempt for comparing the channel capacity on different performance improvement schemes has been made. In particular, the channel capacity of MIMO system is compared with single-input single-output (SISO) system. The MIMO complex spreading CDMA system with path correlation yields better performance with respect to channel capacity than a SISO system with i.i.d. input and output. And a discussion on the multiple-access near/far interference is also included, which illustrates that it can be effectively limited by power control and channel estimation schemes.