Path Delay Profile Research Articles

Generalized cell morphological parameters based on interferometric phase microscopy and their application to cell life cycle characterization

We present analysis tools which are formulated using wide-field interferometric phase microscopy measurements, and show their ability to uniquely quantify the life cycle of live cancer cells. These parameters are based directly on the optical path delay profile of the sample and do not necessitate decoupling the refractive index and the thickness in the cell interferometric phase profile, and thus can be calculated using a single-frame acquisition. To demonstrate the use of these parameters, we have constructed a wide-field interferometric phase microscopy setup and closely traced the full lifecycle of HeLa cancer cells. These initial results show the potential of the parameters to distinguish between the different phases of the cell lifecycle, as well others biological phenomena.

Interconnect Driver Design for Long Wires in Field-Programmable Gate Arrays

Each new semiconductor technology node brings smaller, faster transistors and smaller, slower wires. In particular, long interconnect wires in modern FPGAs now require rebuffering at interior points in the wire. This paper presents a framework for designing and evaluating long, buffered interconnect wires in FPGAs with near-optimal delay performance using HSPICE-derived delays. Given a target physical wire length, width, and spacing, the method determines the number, size, and position of buffers required to obtain the fastest signal velocity for programmable interconnect. While traditional hand-calculations used for ideal repeater placement can be used, they are not very accurate and ignore practical constraints such as the overhead effects of front-end multiplexing and driving logic, “finite” wire length, and a discrete number of repeaters. A metric introduced during the design is the “path delay profile”, or the arrival time of a signal at different points of a long wire. This method is used to design buffering strategies for interconnect based on 0.5, 2, and 3 mm wire lengths in 180 nm technology. These interconnect designs are coded into VPR along with an improved timing analyzer which accurately determines the “path delay profile” arrival times. Using VPR, average critical-path delay is reduced by 19% for 0.5 mm wires and by up to 46% for 3mm wires over previous designs.

Prediction of available path number in wideband mobile propagation

A formula to predict the available path number in wideband mobile propagation is proposed. It is based on the authors' previously proposed empirical path delay profile model. The predicted values are in good agreement with measured data, demonstrating that the proposed formula is valid.

Error probability performance for W-CDMA systems with multiple transmit and receive antennas in correlated nakagami fading channels

The bit error rate (BER) performance of a two-dimensional (2-D) RAKE receiver, in combination with transmit diversity on the downlink of a wide-band CDMA (W-CDMA) system, is presented. The analyses assume correlated fading between receive antenna array elements, and an arbitrary number of independent but nonidentical resolvable multipaths combined by the RAKE receiver in the general Nakagami-m (1960) fading channel framework. The impact of the array configuration (e.g., the number of transmit antennas and receive antennas, the antenna element separation) and the operating environment parameters (such as the fading severity, angular spread and path delay profile) on the overall space-path diversity gain can be directly evaluated. In addition, the exact pairwise error probability of a convolutional coded system is obtained, and the coding gain of a space-path diversity receiver is quantified.