We propose a code acquisition scheme called improved multiple-shift (IMS) for optical code division multiple access systems, where the optical orthogonal code is used instead of the pseudo noise code. Although the IMS algorithm has a similar process to that of the conventional MS algorithm, it has a better code acquisition performance than the conventional MS algorithm. We analyze the code acqu...

One of the most critical problem in the asynchronous DS/CDMA reception consists of the effective acquisition of the initial pseudo-noise (PN) synchronism. In particular the multi-user interference (MUI) contrasts the operation to synchronise correctly the system. In this paper1, an adaptive PN acquisition scheme based on a statistical hypothesis testing and able to reduce the detrimental effect...

Consider independent long range percolation on Z2, where horizontal and vertical edges of length n are open with probability pn. We show that if lim supn→∞ pn > 0, then there exists an integer N such that PN (0 ↔ ∞) > 0, where PN is the truncated measure obtained by taking pN,n = pn for n ≤ N and pN,n = 0 for all n > N .

On a weighted graph G, a total acquisition move transfers weight from a vertex u to a neighbor v provided that the weight on v is at least as much as the weight on u. Starting with all vertices having weight 1, the total acquisition number of G, denoted at(G), is the minimum number of vertices with positive weight after a sequence of total acquisition moves. In [D. Lampert and P. Slater, Congr....

Let Fpm be a finite field of cardinality p m and R = Fpm[u]/〈u 〉 = Fpm +uFpm (u = 0), where p is a prime and m is a positive integer. For any λ ∈ Fpm, an explicit representation for all distinct λ-constacyclic codes over R of length pn is given by a canonical form decomposition for each code, where s and n are positive integers satisfying gcd(p, n) = 1. For any such code, using its canonical fo...

The aim of this paper is to explain how, starting from a Goppa code C(X,G, P1, ..., Pn) and a cyclic covering π : Y → X of degree m, one can twist the initial code to another one C(X,G + Dχ, P1, ..., Pn), where Dχ is a non-principal degree 0 divisor on X associated to a character χ of Gal(Y/X), in the hope that `X(G + Dχ) > `X(G). We give, using a MAGMA program, several examples where this occu...

The essence of GPS signal acquisition is a two-dimensional search process for the carrier Doppler and code phase, generally including correlator, signal capture device, and logic control module. The disposal efficiency of correlator would affect the capture speed of the whole acquisition process. Because of the corresponding relation between frequencydomain multiplication and time-domain convol...

A blind joint estimator for multipath diversity and PN code timing error is proposed in this paper for direct-sequence spread-spectrum signaling on a frequency-selective fading channel. In the multipath diversity combiner, a modi ed known modulus adaptive (KMA) algorithm is used to cope with time-varyingmultipath e ects and to perform multipath diversity combining in the blind mode. In the code...

BACKGROUND Myocardial arterial spin labeling (ASL) is a noninvasive MRI based technique that is capable of measuring myocardial blood flow (MBF) in humans. It suffers from poor sensitivity to MBF due to high physiological noise (PN). This study aims to determine if the sensitivity of myocardial ASL to MBF can be improved by reducing image acquisition time, via parallel imaging. METHODS Myocar...