Method of noise factor computation for chip equalizer in spread spectrum receiver

1. An apparatus for computing a noise factor for a chip equalizer in a spread spectrum receiver, the apparatus comprising:

first computing means for computing channel and noise variance estimates for multiple resolvable fading paths of chip signals received at said spread spectrum receiver;

second computing means for computing a sum of power of the channel estimates;

estimating means for estimating chip energy of the chip signals; and

third computing means for computing the noise factor from the chip energy estimate, the channel and noise variance estimates, the sum of power of the channel estimates, and spreading factor of a pilot signal,

wherein the third computing means computes the noise factor by selecting the channel and noise variance estimates from the fading path having greatest power.

2. The apparatus according to claim 1 , wherein the third computing means selects the channel ĥ m and noise variance σ m 2 estimates from the fading path having the greatest power is carried out in accordance with following expression (2):

m

=

arg

[

max

⁢

{



h

^

l



2

}

]

where m is an index of the fading path having the greatest power and ĥ l is the channel estimate of l-th fading path.

3. The apparatus according to claim 2 , wherein the third computing means computes the noise factor β in accordance with following expression:

β

=

E

^

c

⁢



h

^

m



2

E

^

c

-

SF

⁢

⁢

σ

m

2

-

P

~

.

(

3

)

where Ê c is the estimated chip energy of the chip signals, ĥ m is the channel estimate of the fading path having the strongest power, σ m 2 is the noise variance estimate of the fading path having the strongest power, SF is the spreading factor of the pilot signal received at said spread spectrum receiver and {circumflex over (P)} is sum of power of the channel estimates.

4. An apparatus for determining filter coefficients for use in a chip equalizer (FIR) Finite Impulse Response filter making up a spread spectrum receiver, the apparatus comprising:

first computing means for computing channel and noise variance estimates for multiple resolvable fading paths of chip signals received at said spread spectrum receiver;

second computing means for computing a sum of power of the channel estimates;

estimating means for estimating chip energy of the chip signals;

third computing means for computing a scalar noise factor from the chip energy estimates, the channel and noise variance estimates, the sum of power of the channel estimates, and spreading factor of a pilot signal;

constructing means for constructing a matrix G according to expression;

G=H H H+βI

where H H H is a channel correlation matrix, I is identity matrix, and β is the scalar noise factor; and

calculating means for calculating the filter coefficients based on the matrix G.

5. An apparatus for computing a noise factor for a chip equalizer in a spread spectrum receiver, the apparatus comprising:

a first computing unit configured to compute channel and noise variance estimates for multiple resolvable fading paths of chip signals received at said spread spectrum receiver;

a second computing unit configured to compute a sum of power of the channel estimates;

an estimating unit configured to estimate chip energy of the chip signals; and

a third computing unit configured to compute the noise factor from the chip energy estimate, the channel and noise variance estimates, the sum of power of the channel estimates, and spreading factor of a pilot signal,

wherein the third computing unit computes the noise factor by selecting the channel and noise variance estimates from the fading path having greatest power.

6. The apparatus according to claim 5 , wherein the third computing unit selects the channel ĥ m and noise variance σ m 2 estimates from the fading path having the greatest power is carried out in accordance with following expression:

m

=

arg

[

max

⁢

{



h

^

l



2

}

]

where m is an index of the fading path having the greatest power and ĥ l is the channel estimate of l-th fading path.

7. The apparatus according to claim 6 , wherein the third computing unit computes the noise factor β in accordance with following expression:

β

=

E

^

c

⁢



h

^

m



2

E

^

c

-

SF

⁢

⁢

σ

m

2

-

P

^

where Ê c is the estimated chip energy of the chip signals, ĥ m is the channel estimate of the fading path having the strongest power, σ m 2 is the noise variance estimate of the fading path having the strongest power, SF is the spreading factor of the pilot signal received at said spread spectrum receiver and {circumflex over (P)} is sum of power of the channel estimates.

8. An apparatus for determining filter coefficients for use in a chip equalizer (FIR) Finite Impulse Response filter making up a spread spectrum receiver, the apparatus comprising:

a first computing unit configured to compute channel and noise variance estimates for multiple resolvable fading paths of chip signals received at said spread spectrum receiver;

a second computing unit configured to compute a sum of power of the channel estimates;

an estimating unit configured to estimate chip energy of the chip signals;

a third computing unit configured to compute a scalar noise factor from the chip energy estimates, the channel and noise variance estimates, the sum of power of the channel estimates, and spreading factor of a pilot signal;

a constructing unit configured to construct a matrix G according to expression;

G=H H H+βI

where H H H is a channel correlation matrix, I is identity matrix, and β is the scalar noise factor; and

a calculating unit configured to calculate the filter coefficients based on the matrix G.