Method and apparatus for mobile radio velocity estimation

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figures.
Referring now to FIG.
1, there is shown a block diagram of a velocity estimation system that can be used in a radio communication device.
The velocity estimation system 100 in one embodiment is performed by a Digital Signal Processor (DSP) which performs the functions of the velocity estimation system.
Although a DSP is preferably used, other controllers, hardware and or hardware/software combinations can be used to perform the functions of the velocity estimation system 100.
When a radio communication device (also referred to as a Mobile Station or MS) such as a cellular telephone is in motion, it introduces a Doppler, or frequency shift into the incident plane wave.
The Doppler frequency can be determined as follows, .
lamda.
.
times.
.
times.
##EQU00001## where, v Velocity of the mobile, .
lamda.
Wavelength of the signal, and f.
sub.
d Doppler frequency.
For macro-cellular applications as an example, it is reasonable to assume that the plane waves arrive at the MS antenna from all directions with equal probability.
Under this assumption, R.
Clarke's (see R.
Clarke, "A statistical theory of mobile radio reception", Bell System Technical Journal, Vol.
47, pp.
957 1000, 1968.
) two-dimensional isotropic scattering gives the autocorrelation of the received signal: E[r(t)r(t-.
tau.
)]=E[r(t).
sup.
2]J.
sub.
0(2.
pi.
f.
sub.
d.
tau.
) (Equation 2) where in Equation 2, E[r(t)r(t-.
tau.
)] Autocorrelation of the received signal, .
tau.
Lag associated with the correlation, E[r(t).
sup.
2] Signal power, and J.
sub.
0 Bessel function of order 0.
The scattering model was verified by Clarke with field data.
In heavily built-up areas like New York City, the mobile reception matches the scattered model.
In the suburbs (or other non built-up areas) when the mobile is close to the transmitter, there will be a direct line-of-sight issue that is dealt with in accordance with an embodiment of the invention by adding it to the power and the autocorrelation and taking their division which will help alleviate the line-of-sight problem as well be discussed further below