Lei Zhongding
Email Address
eleleizd@nus.edu.sg
6 results
Publication Search Results
Now showing 1 - 6 of 6
Publication Simplified polynomial-expansion linear detectors for DS-CDMA systems(1998-08-06) Lei, Z.D.; Lim, T.J.; CENTRE FOR WIRELESS COMMUNICATIONS; ELECTRICAL ENGINEERINGThe multistage linear receiver of Moshavi et al. was designed to approximate the decorrelating detector and the MMSE detector without calculating the inverse of the cross-correlation matrix R of the spreading codes directly. However, it is complicated by the need to calculate a set of weights using a procedure involving the inverting of a large matrix. A modified structure is proposed to accomplish the same task without the need for computationally-intensive procedures such as matrix inversion.Publication Method for selecting switched orthogonal beams for downlink diversity transmission(2003-10-09) LEI, ZHONGDING; CHIN, PO SHIN FRANCOIS; LIANG, YING CHANG; INSTITUTE FOR COMMUNICATIONS RESEARCH; CENTRE FOR WIRELESS COMMUNICATIONS; ELECTRICAL & COMPUTER ENGINEERINGA scheme for selecting two beams in a switched beam antenna system for providing downlink communications in a downlink channel, the switched beam antenna system providing uplink reception and downlink transmission is described. The scheme involves selecting a pair of beams based on the uplink reception of the switched beam antenna system, and determining from the pair of beams a corresponding pair of orthogonal beams. The scheme also involves providing the pair of orthogonal beams as a pair of transmit beams for the downlink transmission of the switched beam antenna system.Publication METHOD FOR SELECTING SWITCHED ORTHOGONAL BEAMS FOR DOWNLINK DIVERSITY TRANSMISSION(2003-10-16) LEI, ZHONGDING; CHIN, PO SHIN FRANCOIS; LIANG, YING CHANG; INSTITUTE FOR COMMUNICATIONS RESEARCH; CENTRE FOR WIRELESS COMMUNICATIONS; ELECTRICAL & COMPUTER ENGINEERINGA scheme for selecting two beams in a switched beam antenna system for providing downlink communications in a downlink channel, the switched beam antenna system providing uplink reception and downlink transmission is described. The scheme involves selecting a pair of beams based on the uplink reception of the switched beam antenna system, and determining from the pair of beams a corresponding pair of orthogonal beams. The scheme also involves providing the pair of orthogonal beams as a pair of transmit beams for the downlink transmission of the switched beam antenna system.Publication Estimation of directions of arrival of multipath signals in CDMA systems(2000-06) Lei, Z.; Lim, T.J.; CENTRE FOR WIRELESS COMMUNICATIONSIn this paper, an algorithm is proposed for estimating the directions of arrival (DOA's) of multipath signals received from multiple users on the uplink of a code-division multiple-access system. The correlation matrices of the received signal before and after code-matched filtering are used to provide unique estimates even when the number of required DOA's exceeds the number of antenna array elements. This scenario is well known to cause conventional direction-finding algorithms (such as MUSIC) to fail. Both intersymbol interference (ISI) and multiple-access interference (MAI) are modeled exactly, and so the algorithm performs much better than those which model ISI and MAI as Gaussian noise.Publication Van der Waals negative capacitance transistors(Nature Publishing Group, 2019) Wang, X.; Yu, P.; Lei, Z.; Zhu, C.; Cao, X.; Liu, F.; You, L.; Zeng, Q.; Deng, Y.; Zhu, C.; Zhou, J.; Fu, Q.; Wang, J.; Huang, Y.; Liu, Z.; ELECTRICAL ENGINEERINGThe Boltzmann distribution of electrons sets a fundamental barrier to lowering energy consumption in metal-oxide-semiconductor field-effect transistors (MOSFETs). Negative capacitance FET (NC-FET), as an emerging FET architecture, is promising to overcome this thermionic limit and build ultra-low-power consuming electronics. Here, we demonstrate steep-slope NC-FETs based on two-dimensional molybdenum disulfide and CuInP2S6 (CIPS) van der Waals (vdW) heterostructure. The vdW NC-FET provides an average subthreshold swing (SS) less than the Boltzmann’s limit for over seven decades of drain current, with a minimum SS of 28 mV dec?1. Negligible hysteresis is achieved in NC-FETs with the thickness of CIPS less than 20 nm. A voltage gain of 24 is measured for vdW NC-FET logic inverter. Flexible vdW NC-FET is further demonstrated with sub-60 mV dec?1 switching characteristics under the bending radius down to 3.8 mm. These results demonstrate the great potential of vdW NC-FET for ultra-low-power and flexible applications. © 2019, The Author(s).Publication Simplified polynomial-expansion linear detectors for DS-CDMA systems(1998-08-06) Lei, Z.D.; Lim, T.J.; CENTRE FOR WIRELESS COMMUNICATIONS; ELECTRICAL ENGINEERINGThe multistage linear receiver of Moshavi et al. was designed to approximate the decorrelating detector and the MMSE detector without calculating the inverse of the cross-correlation matrix R of the spreading codes directly. However, it is complicated by the need to calculate a set of weights using a procedure involving the inverting of a large matrix. A modified structure is proposed to accomplish the same task without the need for computationally-intensive procedures such as matrix inversion.