Pulse or digital communications – Synchronizers – Self-synchronizing signal
Reexamination Certificate
2001-05-31
2003-10-21
Tran, Khai (Department: 2637)
Pulse or digital communications
Synchronizers
Self-synchronizing signal
C342S357490, C375S150000
Reexamination Certificate
active
06636574
ABSTRACT:
FIELD OF THE INVENTIONS
The present inventions relate generally to mobile wireless communication devices, and more particularly to estimating Doppler spread/velocity in mobile wireless communication devices.
BACKGROUND OF THE INVENTIONS
The performance of many cellular communication systems is dependent on the accuracy of the estimation of unknown parameters, for example, fading channel coefficients in third-generation cellular communication systems, by a mobile wireless communication station or device.
One significant source of parameter estimate inaccuracy is the Doppler phenomenon experienced when a mobile station is in motion. Channel estimation in some cellular communication systems, for example, requires filtering pilot signals received at the mobile station. The optimum bandwidth of the filter is dependent on the Doppler spread.
Velocity is proportional to frequency and thus to Doppler spread. Knowledge of accurate Doppler spread in mobile wireless communication devices is useful for assigning slower mobile stations to micro-cells and for assigning faster mobile stations to macro-cells, and for making relatively precise power control measurements.
It is known how to estimate Doppler spread based on the autocovariance of the square of the magnitude of a signal received at the mobile station. A problem with this approach however is estimator degradation, which results from poor noise immunity associated with estimating the autocovariance of a squared magnitude at lag 0. Another problem with this prior art approach is that it is based upon estimates of 1
st
and 2
nd
order moments of the squared magnitude of the received signal, which are basically 2
nd
and 4
th
order moments of the signal. Higher order moments of the received signal are generally more difficult to estimate than lower order moments thereof, and thus prior art Doppler spread estimates based on estimates of 1
st
and 2
nd
order moments of the squared magnitude of the received signal are susceptible to inaccuracies, which may result in poor system performance.
The various aspects, features and advantages of the present inventions will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description of the Inventions and the accompanying drawings described below.
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patent: 6424642 (2002-07-01), Schmidl et al.
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patent: 6470044 (2002-10-01), Kowalski
Doppler Spread Estimation in Mobile Radio Systems; Authors—Leonid Krasny, Huseyin Arslan, David Koilpillai and Sandeep Chennakeshu; IEEE Communications Letters, vol. 5, No. 5, May 2001; pp. 197-199.
Estimation of Maximum Doppler Frequency for Handoff Decisions; Authors—Ashwin Sampath and Jack M. Holtzman, Wireless Information Network Laboratory (WINLAB), Rutgers University, Piscataway, NJ 08855-0909; pp. 859-862.
Mallette Alexandre
Oliver John Paul
Motorola Inc.
Tran Khai
LandOfFree
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