Mobility patterns in microcellular wireless networks

This study investigates mobility patterns in microcellular wireless networks, based on measurements from the 802.11 based system that blankets the Carnegie Mellon University campus. We characterize the distribution of dwell time, which is the length of time that a mobile device remains in a cell until the next handoff, and sign-on interarrival time, which is the length of time between successive sign-ons from the same mobile device. Many researchers have assumed that these distributions are exponential, but our results based on empirical analysis show that dwell time and sign-on interarrival time can be accurately described using heavy-tailed arithmetic distributions that have infinite mean and variance. We also show that the number of handoffs per sign-on can be modeled accurately with a heavy-tailed distribution.     

Least-mean-square (minimum integrated power loss ratio) lowpass filters with a pair of imaginary-axis zeros

If power is the main interest, then a class of filters with minimum integrated power loss ratio in the passband offers higher cutoff rate than the well known Butterworth filters. A technique is described to improve the cutoff rate further by introducing a pair of imaginary axis zeros, while the integrated power loss ratio in the passband is still kept at minimum. Other advantageous performances of the filters are also indicated.     

Recursive digital filters with predetermined group delay andChebyshev stopband attenuation

Recently, a conformal mapping technique has been described whereby the transfer function of a recursive digital filter with prescribed group delay and Chebyshev stopband can be obtained in such a way that the numerator and denominator polynomials are different in order. It is shown here that such a transfer function can also be determined using the familiar bilinear transformation and the well known method in the s-domain. Numerical examples are included to demonstrate the technique     

Sine-cosine squared-magnitude function for maximally flat digital bandpass filters with adjustable skirt selectivities

A sine-cosine squared-magnitude function for a digital bandpass filter is proposed. It offers a maximally flat passband magnitude response and more flexibility on the number of exchangeable zeros at ?T = 0 and ?T = ? rad.     

Design of recursive digital filters approximating to arbitrary prescribed magnitude responses

A computer-aided design of a recursive digital filter that approximates to an arbitrary prescribed magnitude response in a minimax sense is described. The problem is formulated in a linear-programming form and hence can be solved by the well known simplex method.     

Maximally flat f.i.r. filter with prescribed cutoff frequency

Maximally flat f.i.r. digital filter design provides the advantage of giving a closed-form solution, but there still remains a problem of designing such a filter whose magnitude response passes through a prescribed cutoff frequency point. It is described here how to generate a class of transitional maximally flat f.i.r. digital filters to overcome such a difficulty.     

Transitional Butterworth-Cheby?shev filters

A class of transitional Butterworth-Cheby?shev filters is presented. The filters show gradual transition and, at the same time, maintain the equiripple peaks.