Method, arrangement and communication receiver for SNIR estimation
View Patent ↗A method, arrangement ( 512 ) and communication receiver ( 500 ) for SNIR estimation of a received signal, by: deriving ( 512 A) an estimation {circumflex over (Z)} of SNIR of the received signal in accordance with the relation Z ^ = [ E { r ( t ) } ] 2 E { r 2 ( t ) } - [ E { r ( t ) } ] 2 , where E represents mean value and r(t) represents the level of the received signal; and correcting ( 512 B, 512 C) the estimation {circumflex over (Z)} to produce a corrected estimation Z based on the relation Z=α({circumflex over (Z)})×{circumflex over (Z)}, where α({circumflex over (Z)}) represents a correction factor. The estimation may be corrected by calculating the correction factor, retrieving the correction factor from a predetermined table ( 512 B) or retrieving the corrected estimation from a predetermined table. The correction may be effected by adding to a logarithmic estimation a logarithmic correction factor. This provides the advantage of improved performance under conditions of low signal to noise ratio.
1. A method for estimating an accurate signal quality metric of a received signal, the method comprising:
receiving a signal;
calculating an estimated signal quality metric {circumflex over (Z)} of the received signal, wherein the estimated signal quality metric {circumflex over (Z)} is based on
Z
^
=
[
E
{
r
(
t
)
}
]
2
E
{
r
2
(
t
)
}
-
[
E
{
r
(
t
)
}
]
2
,
wherein E is mean value and r(t) is the level of the received signal, [E{|r(t)|}] 2 is the estimated signal power, and E{r 2 (t)}−[E{|r(t)|}] 2 is a difference of the estimated total power and the estimated signal power;
determining a correction factor based on a received signal variance and an estimated amplitude; and
applying the correction factor to the estimated signal quality metric to determine a corrected signal quality metric.
2. The method of claim 1 wherein the signal quality metric is a logarithmic quantity and the step of correcting the estimated signal quality metric comprises adding a logarithmic correction factor to the estimated signal quality metric {circumflex over (Z)} to produce a corrected signal quality metric Z.
3. The method of claim 1 wherein the step of correcting the estimated signal quality metric comprises retrieving the correction factor from a predetermined table.
4. The method of claim 1 wherein the step of correcting the estimated signal quality metric comprises retrieving the corrected signal quality metric from a predetermined table.
5. The method of claim 1 wherein the received signal is a wireless signal.
6. The method of claim 5 wherein the wireless signal is a Universal Mobile Telecommunication System (UMTS) air interface signal.
7. A computer-readable medium encoded with computer program instructions for performing the method of claim 1 .
8. The method of claim 1 , wherein applying the correction factor comprises multiplying the estimated signal quality metric by the correction factor.
9. The method of claim 1 , wherein determining the correction factor is further based on a measured amplitude of the received signal.
10. The method of claim 1 ,
wherein determining the correction factor is based on
Z =α( {circumflex over (Z)} )×{circumflex over (Z)},
wherein α is the correction factor, {circumflex over (Z)} is the estimated signal quality metric, Â is the estimated signal amplitude, Z is the corrected signal quality metric, A is signal amplitude, and σ 2 is the variance, and
wherein
Z
^
=
A
^
2
A
2
+
σ
2
-
A
^
2
,
Z
=
A
2
σ
2
,
and
A
^
=
A
[
1
+
2
π
Z
e
-
Z
/
2
-
erfc
(
Z
2
)
]
.
11. The method of claim 10 wherein
Z =α({circumflex over ( Z )})×{circumflex over ( Z )}
is based on
Z
^
=
[
1
+
2
π
Z
ⅇ
-
z
2
-
erfc
(
Z
2
)
]
2
1
+
1
Z
-
[
1
+
2
π
Z
ⅇ
-
z
2
-
erfc
(
Z
2
)
]
2
.
12. The method of claim 1 , wherein the received signal is a symmetric binary-valued signal.
13. The received signal of claim 12 , wherein the symmetric binary-valued signal is a Binary Phase Shift Keyed signal (BPSK).
14. The received signal of claim 1 , wherein the received signal is a Quadrature Phase Shift Keyed signal (QPSK).
15. The method of claim 1 , wherein the signal quality metric is a Signal to Noise-plus-Interference Ratio (SNIR).
16. An apparatus for estimating an accurate signal quality metric estimation of a received signal, the apparatus comprising:
control logic for determining a correction factor for an estimated signal quality metric of a received signal,
wherein the correction factor is based on the received signal variance and an estimated amplitude; and
signal processing logic for determining an estimated signal quality metric {circumflex over (Z)} of the received signal and applying the correction factor to the estimated signal quality metric to provide a corrected signal quality metric, wherein the signal quality metric {circumflex over (Z)} is based on
Z
^
=
[
E
{
r
(
t
)
}
]
2
E
{
r
2
(
t
)
}
-
[
E
{
r
(
t
)
}
]
2
,
wherein E is mean value and r(t) is the level of the received signal, [E{|r(t)|}] 2 is the estimated signal power, and E{r 2 (t)}−[E{|r(t)|}] 2 is a difference of the estimated total power and the estimated signal power.
17. The apparatus of claim 16 wherein the estimated signal quality metric is a logarithmic quantity and the signal processing logic for correcting the estimated signal quality metric comprises logic for adding a logarithmic correction factor to the estimated signal quality metric {circumflex over (Z)} to produce a corrected signal quality metric Z.
18. The apparatus of claim 16 wherein the means for correcting the estimated signal quality metric comprises means for retrieving the correction factor from a predetermined table.
19. The apparatus of claim 16 wherein the means for correcting the estimated signal quality metric comprises means for retrieving the corrected signal quality metric from a predetermined table.
20. The apparatus of claim 16 wherein the received signal is a wireless signal.
21. The apparatus of claim 20 wherein the wireless signal is a Universal Mobile Telecommunication System (UMTS) air interface signal.
22. A communication receiver comprising the apparatus of claim 16 .
23. User equipment for use in a wireless communication system, the user equipment comprising the communication receiver of claim 22 .
24. A base station for use in a wireless communication system, the base station comprising the communication receiver of claim 22 .
25. An integrated circuit comprising the apparatus of claim 16 .
26. The apparatus of claim 16 , wherein the signal processing logic is operable to multiply the estimated signal quality metric by the correction factor.
27. The apparatus of claim 16 , wherein the control logic is operable to determine a measured amplitude of the received signal.
28. The apparatus of claim 16 ,
wherein the correction factor is based on
Z =α( {circumflex over (Z)} )×{circumflex over (Z)},
wherein α represents the correction factor, {circumflex over (Z)} is the estimated signal quality metric; Â is the estimated signal amplitude, Z is the corrected signal quality metric, A is signal amplitude, and σ 2 is the variance, and
wherein
Z
^
=
A
^
2
A
2
+
σ
2
-
A
^
2
,
Z
=
A
2
σ
2
,
and
A
^
=
A
[
1
+
2
π
Z
e
-
Z
/
2
-
erfc
(
Z
2
)
]
.
29. The apparatus of claim 28 wherein the relationship
Z =α({circumflex over ( Z )})×{circumflex over ( Z )}
is based on
Z
^
=
[
1
+
2
π
Z
ⅇ
-
z
2
-
erfc
(
Z
2
)
]
2
1
+
1
Z
-
[
1
+
2
π
Z
ⅇ
-
z
2
-
erfc
(
Z
2
)
]
2
.
30. The apparatus of claim 16 , wherein the received signal is a symmetric binary-valued signal.
31. The received signal of claim 30 , wherein the symmetric binary-valued signal is a Binary Phase Shift Keyed signal (BPSK).
32. The received signal of claim 16 , wherein the received signal is a Quadrature Phase Shift Keyed signal (QPSK).
33. The apparatus of claim 16 , wherein the signal quality metric is a Signal to Noise-plus-Interference Ratio (SNIR).