Method of measuring transmit quality in a closed loop diversity communication system
View Patent ↗In a method for determining channel quality information in a high speed packet access communication system with closed loop transmit diversity, power and variance related to a common pilot channel (CPICH) are determined for a rake receiver to obtain a closed loop transmit gain adjustment and to determine the CPICH signal-to-noise ratio. Thereafter, a high speed downlink shared channel (HS-DSCH) signal-to-noise ratio is determined from the CPICH signal-to-noise ratio and is mapped to derive channel quality information.
1. A method, carried out by a mobile station, for determining channel quality information in a high speed packet access communication system with closed loop transmit diversity, the method comprising:
determining common pilot channel (CPICH) power and variance in each finger of a rake receiver;
adjusting the CPICH power in each finger with a closed loop transmit gain adjustment;
combining the adjusted CPICH power and variance in all fingers of the rake receiver;
determining a CPICH signal-to-noise ratio;
determining a high speed downlink shared channel (HS-DSCH) signal-to-noise ratio from the CPICH signal-to-noise ratio; and
mapping the HS-DSCH signal-to-noise ratio to derive the channel quality information,
wherein the closed loop transmit gain adjustment for each finger is calculated from complex channel estimates for a first antenna and a second antenna complex antenna weight,
wherein:
the closed loop transmit gain adjustment ΔG k applied to each finger k is determined from the following:
Δ
G
k
=
1
+
2
α
_
1
I
k
α
_
2
I
k
w
2
I
-
α
_
1
I
k
α
_
2
Q
k
w
2
Q
+
α
_
1
Q
k
α
_
2
Q
k
w
2
I
-
α
_
1
Q
k
α
_
2
I
k
w
2
Q
α
_
1
k
2
+
α
_
2
k
2
where
k is a finger index,
w is the complex antenna weight,
α
_
1
=
1
N
∑
n
α
1
(
n
)
and
α
_
2
=
1
N
∑
n
α
2
(
n
)
with
N
=
5
;
and
α 1 k (n) and α 2 k (n) denote complex channel estimates for the first antenna and the second antenna.
2. A mobile station forming part of a high speed packet access communication system with closed loop transmit diversity, the mobile station, comprising:
circuitry for carrying out processing which comprises:
determining common pilot channel (CPICH) power and variance in each finger of a rake receiver;
adjusting the CPICH power in each finger with a closed loop transmit gain adjustment;
combining the adjusted CPICH power and variance in all fingers of the rake receiver;
determining the CPICH signal-to-noise ratio;
determining a high speed downlink shared channel (HS-DSCH) signal-to-noise ratio from the CPICH signal-to-noise ratio; and
mapping the HS-DSCH signal-to-noise ratio to derive the channel quality information,
wherein:
the closed loop transmit gain adjustment for each finger is calculated from complex channel estimates for a first antenna and a second antenna complex antenna weight; and
wherein:
the closed loop transmit gain adjustment ΔG k applied to each finger k is determined from the following:
Δ
G
k
=
1
+
2
α
_
1
I
k
α
_
2
I
k
w
2
I
-
α
_
1
I
k
α
_
2
Q
k
w
2
Q
+
α
_
1
Q
k
α
_
2
Q
k
w
2
I
+
α
_
1
Q
k
α
_
2
I
k
w
2
Q
α
_
1
k
2
+
α
_
2
k
2
where k is a finger index,
w is the complex antenna weight,
α
_
1
=
1
N
∑
n
α
1
(
n
)
and
α
_
2
=
1
N
∑
n
α
2
(
n
)
with
N
=
5
;
and
α 1 k (n) and α 2 k (n) denote complex channel estimates for the first antenna and the second antenna.
3. A method, being carried out by a mobile station, for determining channel quality information in a high speed packet access communication system with closed loop transmit diversity, the method comprising:
determining common pilot channel (CPICH) combined power and variance in a plurality of fingers of a rake receiver;
adjusting the CPICH combined power and variance in each finger with a closed loop transmit gain adjustment for each slot;
determining a CPICH signal-to-noise ratio;
determining a high speed downlink shared channel (HS-DSCH) signal-to-noise ratio from the CPICH signal-to-noise ratio by the mobile station; and
mapping HS-DSCH signal-to-noise ratio to derive the channel quality information,
wherein:
the closed loop transmit rain adjustment for CPICH power is calculated from complex channel estimates for a first antenna and a second antenna and complex antenna weight, and
wherein:
the closed loop transmit gain adjustment for CPICH combined power
P
CPICH_Rake
_Adj
=
P
CPICH_Rake
∑
k
(
c
-
k
+
G
k
)
is calculated, for each slot from k-th multipath output, according to
G
k
=
1
10
∑
n
=
1
10
(
2
α
1
I
k
(
n
)
α
2
I
k
(
n
)
w
2
I
-
α
1
I
k
(
n
)
α
2
Q
k
(
n
)
w
2
Q
+
α
1
Q
k
(
n
)
α
2
Q
k
(
n
)
w
2
I
+
α
1
Q
k
(
n
)
α
2
I
k
(
n
)
w
2
Q
)
and
c
-
k
=
1
10
∑
n
(
α
1
k
(
n
)
α
1
k
*
(
n
)
+
α
2
k
(
n
)
α
2
k
*
(
n
)
)
,
where w 2 is the complex antenna weight for the corresponding slot, n is a symbol index in a slot, α 1 k (n) and α 2 k (n) denote complex channel estimates for the first antenna and the second antenna, respectively, α 1 k* (n) and α k* (n) are complex conjugates of α 1 k (n) and α 2 k (n), and I and Q in subscripts correspond to I and Q components of a complex number.
4. The method according to claim 3 , wherein the closed loop transmit gain adjustment for CPICH variance is calculated from complex channel estimates for the first antenna and the second antenna and complex antenna weight.
5. The method according to claim 4 , wherein the closed loop transmit adjustment for CPICH variance
σ
CPICH_Rake
_Adj
=
σ
CPICH_Rake
∑
k
c
-
k
is calculated, for each slot from k-th multipath output, according to
c
-
k
=
1
10
∑
n
(
α
1
k
(
n
)
α
1
k
*
(
n
)
+
α
2
k
(
n
)
α
2
k
*
(
n
)
)
where
α 1 k (n) and α 2 k (n) denote complex channel estimates for the first antenna and the second antenna, and
α 1 (n) and α 2 (n) are complex conjugates of α 1 k (n) and α 2 k (n).
6. A mobile station configured to communicate with a high speed packet access communication system with closed loop transmit diversity, the mobile station comprising:
at least one antenna able to receive a signal which includes a plurality of multipath signal components, on which high speed packet access data is transmitted, and a channel quality estimator,
wherein:
the channel quality estimator is configured to determine channel quality information and carries out processing which comprises:
determining common pilot channel (CPICH) combined power and variance in a plurality of fingers of a rake receiver;
adjusting the CPICH combined power and variance in each finger with a closed loop transmit gain adjustment for each slot;
determining a CPICH signal-to-noise ratio;
determining a high speed downlink shared channel (HS-DSCH) signal-to-noise ratio from the CPICH signal-to-noise ratio by the mobile station; and
mapping the HS-DSCH signal-to-noise ratio to derive the channel quality information;
wherein:
the channel quality estimator further comprises:
a rake combiner for calculating the closed loop transmit gain adjustment for CPICH power from complex channel estimates for a first antenna and a second antenna and complex antenna weight; and
wherein:
the closed loop transmit gain adjustment for CPICH combined power
P
CPICH_Rake
_Adj
=
P
CPICH_Rake
∑
k
(
c
-
k
+
G
k
)
is calculated, for each slot from k-th multipath output, according to
G
k
=
1
10
∑
n
=
1
10
2
(
α
1
I
k
(
n
)
α
2
I
k
(
n
)
w
2
I
-
α
1
I
k
(
n
)
α
2
Q
k
(
n
)
w
2
Q
+
α
1
Q
k
(
n
)
α
2
Q
k
(
n
)
w
2
I
+
α
1
Q
k
(
n
)
α
2
I
k
(
n
)
w
2
Q
)
and
c
-
k
=
1
10
∑
n
(
α
1
k
(
n
)
α
1
k
*
(
n
)
+
α
2
k
(
n
)
α
2
k
*
(
n
)
)
where
w 2 is the complex antenna weight for the corresponding slot,
n is a symbol index in a slot,
α 1 k (n) and α 2 k (n) denote complex channel estimates for the first antenna and the second antenna, respectively,
α 1 k* (n) and α 2 k* (n) are complex conjugates of α 1 k (n) and α 2 k (n), and I and Q in subscripts correspond to I and Q components of a complex number.
7. The mobile station of claim 6 further comprising a plurality of multipath processing fingers configured to demodulate at least one channel on which a determination of the channel quality information will be based.
8. The mobile station of claim 6 further comprising an antenna weight calculator configured to generate antenna weights for use as a feedback signal.
9. The mobile station of claim 6 , wherein the multipath processing fingers comprising adjustment means configured to adjust a relative power of the multipath signal components prior to determination of the channel quality information.
10. The mobile station according to claim 6 ,
wherein:
the channel quality estimator comprises circuitry for calculating the closed loop transmit gain adjustment for CPICH variance from complex channel estimates for the first antenna and the second antenna, and
the closed loop transmit adjustment for CPICH variance
σ
CPICH
_
Rake
_
Adj
=
σ
CPICH
_
Rake
∑
k
c
-
k
is calculated, for each slot from k-th multipath output, according to
c
-
k
=
1
10
∑
n
(
α
1
k
(
n
)
α
1
k
*
(
n
)
+
α
2
k
(
n
)
α
2
k
*
(
n
)
)
.
where
α 1 k (n) and α 2 k (n) denote complex channel estimates for the first antenna and the second antenna, and
α 1 k* (n) and α 2 k* (n) are complex conjugates of α 1 k (n) and α 2 k (n).
11. A mobile station configured to communicate with a high speed packet access communication system with closed loop transmit diversity, the mobile station comprising:
at least one antenna able to receive a signal which includes a plurality of multipath signal components, on which high speed packet access data is transmitted, and a channel quality estimator,
wherein:
the channel quality estimator is configured to determine channel quality information and carries out processing which comprises:
determining common pilot channel (CPICH) combined power and variance in a plurality of fingers of a rake receiver;
adjusting the CPICH combined power and variance in each finger with a closed loop transmit gain adjustment for each slot;
determining a CPICH signal-to-noise ratio;
determining a high speed downlink shared channel (HS-DSCH) signal-to-noise ratio from the CPICH signal-to-noise ratio by the mobile station; and
mapping the HS-DSCH signal-to-noise ratio to derive the channel quality information;
wherein:
the closed loop transmit gain adjustment for CPICH variance is calculated from complex channel estimates for a first antenna and a second antenna and complex antenna weight;
wherein:
the closed loop transmit adjustment for CPICH variance
σ
CPICH
_
Rake
_
Adj
=
σ
CPICH
_
Rake
∑
k
c
-
k
is calculated, for each slot from k-th multipath output, according to
c
-
k
=
1
10
∑
n
(
α
1
k
(
n
)
α
1
k
*
(
n
)
+
α
2
k
(
n
)
α
2
k
*
(
n
)
)
.
where
α 1 k (n) and α 2 k (n) denote complex channel estimates for the first antenna and the second antenna, and
α 1 k* (n) and α 2 k* (n) are complex conjugates of α 1 k (n) and α 2 k (n).