A result on the weight distributions of binary quadratic residue codes

Truong et al. [7]proved that the weight distribution of a binary quadratic residue code C with length congruent to −1 modulo 8 can be determined by the weight distribution of a certain subcode of C containing only one-eighth of the codewords of C. In this paper, we prove that the same conclusion holds for any binary quadratic residue codes.     

A new algorithm for linear-phase paraunitary filter banks with pairwise mirror-image frequency responses

Subband filter banks have attracted much attention during the past few years. In this paper, an efficient design algorithm, which leads to linear-phase paraunitary filter banks with pairwise mirror-image frequency responses, is revisited and further studied. New lattice structures are presented to extend the algorithm to the case where the number (M) of channels is odd. Design examples of filter banks with 3 and 5 channels are presented.     

An investigation of nanoscale tribological characteristics under different interaction forces

The present study employs a Finite Element Method (FEM) atomic approach to investigate the nanoscale mechanisms of sliding friction. The current investigation chooses diamond-like carbon as the hard material, and copper as the soft material. The atomic configurations following sliding under non-interactive, attractive, and repulsive interaction forces are observed for soft-to-soft, hard-to-soft, and hard-to-hard sliding systems. The relationships between the normal force, the friction force, and the sliding distance are discussed. The current simulation results exhibit a similar trend with the findings of previous studies using molecular dynamics approach.     

High frequency scattering from trihedral corner reflectors andother benchmark targets: SBR versus experiment

A general method for calculating the radar cross section (RCS) from a three-dimensional target is described. The target is first constructed by using a solid-geometry-modeling computer-aided design (CAD) package. Following the shooting and bouncing ray (SBR) method, a very dense grid of rays is launched from the incident direction toward the target. Each ray is traced according to the geometrical optics theory including the effect of ray tube divergence, polarization, and material reflection coefficient. At the point where the ray exits the target, a physical optics-type integration is performed to obtain the scattered far fields. This method is tested using several simple examples involving interaction among plates, cylinders, and spheres. The theoretical results are generally in good agreement with measured data     

Simple PN code sequence estimation and synchronisation techniqueusing the constrained Hebbian rule

An adaptive tapped delay line FIR filter updated by the constrained Hebbian rule can blindly estimate and synchronise to the code sequence of a direct sequence (DS) transmission. The proposed technique makes use of the fact that the dominant eigenvector is the spreading sequence itself. The implementation is very simple and is an attractive alternative to standard spread spectrum (SS) synchronisation techniques such as the RASE technique     

Soft synchronization of direct sequence spread-spectrum signals

A new technique for soft synchronization of direct-sequence spread-spectrum (DSSS) signals is presented. The technique, referred to as the dominant mode despreading (DMDS) algorithm, exploits the eigenstructure of a frequency-channelized DSSS signal to estimate the spreading code and underlying message sequence of the signal. Unlike other despreading techniques, the estimate of the code and data improves steadily with the number of code repeats. The technique is applicable to arbitrary spreading codes and message sequences and can operate in environments containing arbitrary levels of white background noise, and for signals with arbitrary unknown timing phase or carrier frequency offset. The technique requires the DSSS signal to have a constant-modulus spreading code and unrelated message and code-repeat rates. This paper introduces the basic technique, theoretically analyzes the algorithm to prove convergence under infinite time-average conditions, and demonstrates the algorithm via computer simulation for a single DSSS signal received in the presence of white Gaussian noise     

A VLSI design for a trace-back Viterbi decoder

A systolic Viterbi decoder for convolutional codes is developed which uses the trace-back method to reduce the amount of data needed to be stored in registers. It is shown that this new algorithm requires a smaller chip size and achieves a faster decoding time than other existing methods     

Flight of the FALCON [ATM]

The fabric-based ATM oriented local connectivity (FALCON), an ATM-based customer premises network (CPN), is described. FALCON supports access using traditional local area networks (LANs) such as Ethernet and token rings and supports a LAN emulation mode for its native ATM interface. This service allows a set of terminals, workstations, and servers to connect to the switch-based network and to interact as if they were attached to a traditional LAN. FALCON's backbone structure is based exclusively on ATM technology, all following CCITT or industry standards wherever they apply. The FALCON control structure is outlined     

FONI-SPATE: A new fibre optic stress/strain sensor, using anear-infrared variant of the SPATE effect

A new fibre optic stress/strain sensor, for monitoring hot materials is reported. The fibre collects grey body emission from a heated material sample. When the sample is subjected to transient stresses, the radiation is modulated due to the adiabatic changes in its temperature. The modulation is monitored, via a silica fibre, using a near-infrared GaInAs photodetector. This is also believed to be the first demonstration of the SPATE method in the near infrared     

A performance comparison of the binary quadratic residue codes withthe 1/2-rate convolutional codes

The 1/2-rate binary quadratic residue (QR) codes, using binary phase-shift keyed (BPSK) modulation and hard decoding, are presented as an efficient system for reliable communication. Performance results of error correction are obtained both theoretically and by means of computer calculations for a number of binary QR codes. These results are compared with the commonly used 1/2-rate convolutional codes with constraint lengths from 3 to 7 for the hard-decision case. The binary QR codes of different lengths are shown to be equivalent in error-correction performance to some 1/2-rate convolutional codes, each of which has a constraint length K that corresponds to the error-control rate d/n and the minimum distance d of the QR codes