US2008019468A1PendingUtilityA1
Soft sample scaling in a turbo decoder
Est. expiryOct 24, 2022(expired)· nominal 20-yr term from priority
H04L 25/067H03M 13/3905H04L 1/0055H03M 13/658H04L 1/005H03M 13/612H03M 13/2957H03M 13/6337
48
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Cited by
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Claims
Abstract
A receiver for iterative decoding of a received, encoded signal employs slot-based scaling of soft samples. Iterative decoding employs a constituent maximum a priori (MAP) decoder for each constituent encoding of information of the encoded signal. Root mean square (RMS) values for soft samples over a slot are selected for dynamic range scaling. Squared RMS values are combined and equal the squared RMS value for a frame multiplied by a control constant, and this relationship may be employed to derive scaling constants for each slot. Alternatively, the square root of the RMS value multiplied by a constant serves as an SNR estimator that may be employed to scale samples to reduce dynamic range and modify logarithmic correction values for max* term calculation during log-MAP decoding.
Claims
exact text as granted — not AI-modified1 . A method of scaling samples of an encoded signal iteratively decoded to generate decoded data, the method comprising the steps of:
(a) generating a root mean square (RMS) value for samples within a slot of a frame comprising a plurality of slots; (b) calculating a scaling factor based on the RMS value of the slot; and (c) scaling the input samples of the slot based on the scaling factor, wherein, for step (b), the scaling factor is a noise variance estimator.
2 . The invention of claim 1 , wherein a slot is a unit time duration of one fixed-transmission power control.
3 . A method of scaling samples of an encoded signal iteratively decoded to generate decoded data, the method comprising the steps of:
(a) generating a root mean square (RMS) value for samples within a slot of a frame comprising a plurality of slots; (b) calculating a scaling factor based on the RMS value of the slot; and (c) scaling the input samples of the slot based on the scaling factor, further comprising the steps of:
b1) estimating a noise variance as a function of the RMS value;
b2) generating a constant for each logarithmic correction term of log-MAP decoding using the estimated noise variance; and
b3) setting the scaling factor based on the constant.
4 . The invention of claim 3 , wherein a slot is a unit time duration of one fixed-transmission power control.
5 . A method of scaling samples of an encoded signal iteratively decoded to generate decoded data, the method comprising the steps of:
(a) generating a root mean square (RMS) value for samples within a slot of a frame comprising a plurality of slots; (b) calculating a scaling factor based on the RMS value of the slot; and (c) scaling the input samples of the slot based on the scaling factor, wherein the scaling factor accounts for at least one of automatic gain control (AGC) and DC offset signals present within the samples.
6 . The invention of claim 5 , wherein a slot is a unit time duration of one fixed-transmission power control.
7 . The invention of claim 5 , wherein the scaling factor (1/c) accounting for AGC is set as:
1
c
=
F
i
E
(
ξ
i
)
RMS
i
=
F
i
(
1
3
K
∑
i
=
0
3
K
-
1
ξ
i
)
RMS
i
,
where F i is a constant is a constant for the slot, RMS i is the RMS value of the samples over the ith slot, E(●) denotes mathematical “expected value of”, and ξ i is the sequence of input soft samples in the slot.
8 . The invention of claim 5 , wherein the scaling factor (1/c) accounting for DC offset is set as:
1
c
=
G
i
RMS
i
-
[
E
(
ξ
i
)
]
2
=
G
i
RMS
i
-
(
1
3
K
∑
i
=
0
3
K
-
1
ξ
i
)
2
,
where G i is a control constant for the slot, RMS i is the RMS value of the samples over the ith slot, E(●) denotes mathematical “expected value of”, and ξ i is the sequence of input soft samples in the slot.
9 . The invention of claim 5 , further comprising the steps of:
b1) estimating a noise variance as a function of the RMS value; b2) generating a constant for each logarithmic correction term of log-MAP decoding using the estimated noise variance; and b3) setting the scaling factor based on the constant.
10 . The invention of claim 9 , wherein the scaling factor (1/c) accounting for AGC is set as:
1
c
=
F
i
E
(
ξ
i
)
RMS
i
=
F
i
(
1
3
K
∑
i
=
0
3
K
-
1
ξ
i
)
RMS
i
,
where F i is a constant is a constant for the slot, RMS i is the RMS value of the samples over the ith slot, E(●) denotes mathematical “expected value of”, and ξ i is the sequence of input soft samples in the slot.
11 . The invention of claim 9 , wherein the scaling factor (1/c) accounting for DC offset is set as:
1
c
=
G
i
RMS
i
-
[
E
(
ξ
i
)
]
2
=
G
i
RMS
i
-
(
1
3
K
∑
i
=
0
3
K
-
1
ξ
i
)
2
,
where G i is a control constant for the slot, RMS i is the RMS value of the samples over the ith slot, E(●) denotes mathematical “expected value of”, and ξ i is the sequence of input soft samples in the slot.
12 . Apparatus for scaling samples of an encoded signal iteratively decoded to generate decoded data, the apparatus comprising:
a first combiner configured to generate a root mean square (RMS) value for samples within a slot of a frame comprising a plurality of slots; a processor configured to calculate a scaling factor based on the RMS value of the slot; and a second combiner configured to scale the input samples of the slot based on the scaling factor, wherein the scaling factor is a noise variance estimator.
13 . The invention of claim 12 , wherein a slot is a unit time duration of one fixed-transmission power control.
14 . The invention of claim 12 , wherein the scaling factor is calculated using a scaling constant such that the RMS value of samples over a frame approximates a predefined value, wherein the frame comprises one or more slots.
15 . The invention of claim 12 , wherein the second combiner scales the samples within the slot to adjust a dynamic range of the samples.
16 . The invention of claim 12 , wherein, the apparatus is embodied in a receiver operating in accordance with a wideband CDMA telecommunication standard.
17 . The invention of claim 12 , wherein the apparatus is embodied in an integrated circuit.
18 . Apparatus for scaling samples of an encoded signal iteratively decoded to generate decoded data, the apparatus comprising:
a first combiner configured to generate a root mean square (RMS) value for samples within a slot of a frame comprising a plurality of slots; a processor configured to calculate a scaling factor based on the RMS value of the slot; and a second combiner configured to scale the input samples of the slot based on the scaling factor, wherein the processor calculates the scaling factor by:
1) estimating a noise variance as a function of the RMS value;
2) generating a constant for each logarithmic correction term of log-MAP decoding using the estimated noise variance; and
3) setting the scaling factor based on the constant.
19 . The invention of claim 18 , wherein the scaling factor is calculated using a scaling constant such that the RMS value of samples over a frame approximates a predefined value, wherein the frame comprises one or more slots.
20 . The invention of claim 18 , wherein the second combiner scales the samples within the slot to adjust a dynamic range of the samples.
21 . The invention of claim 18 , wherein, the apparatus is embodied in a receiver operating in accordance with a wideband CDMA telecommunication standard.
22 . The invention of claim 18 , wherein the apparatus is embodied in an integrated circuit.
23 . The invention of claim 18 , wherein a slot is a unit time duration of one fixed-transmission power control.Join the waitlist — get patent alerts
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