Optimization technique for layered modulation
View Patent ↗A method and apparatus for optimizing a system for transmitting a layered modulated signal is disclosed. The method comprises the steps of defining the system in terms of a set of system parameters, including an optimal power separation S between a power of a first modulation layer and a power of a second modulation layer and a required system carrier-to-noise ratio (CNR S ), determining an optimal power separation S to minimize the error rate of a lower layer modulated signal BER L , and selecting the remaining system parameters in the set of system parameters using the determined optimal power separation S.
1. A method of optimizing a system for transmitting a layered modulated signal, comprising the steps of:
defining the system in terms of a set of system parameters, including an optimal power separation S between a power of a first modulation layer and a power of a second modulation layer and a required system carrier-to-noise ratio (CNR S );
determining an optimal power separation S to minimize an error rate of a lower layer modulated signal BER L ; and
selecting remaining system parameters in the set of system parameters using the determined optimal power separation S.
2. The method of claim 1 , wherein:
the layered modulation signal comprises an upper layer signal and a lower layer signal, and
the step of selecting the remaining system parameters using the determined optimal power separation P x comprises the steps of:
determining a required CNR for the upper layer (CNR U ) and a required CNR for the lower layer (CNR L ) from a relationship between an upper layer coding rate C UL and CNR U , and a lower level coding rate C LL and CNR L ; and
determining a required system CNR (CNR s ) from CNR U , CNR L , and S.
3. The method of claim 2 , wherein the required CNR s is determined at least in part from the relations:
CNR
U
=
10
log
10
10
(
CNR
S
+
S
)
10
1
+
10
S
10
+
10
CNR
S
10
;
and
CNR
L
=
10
log
10
10
CNR
S
1
+
10
S
10
,
wherein (CNR s ) from CNR U , CNR L , and S are expressed in decibels.
4. The method of claim 2 , wherein C UL =C LL .
5. The method of claim 2 , wherein C UL ≠C LL and wherein the step of determining a required system CNR (CNR s ) from CNR U , CNR L , and P x , comprises the steps of:
selecting a value for CNR U and a value for CNR L ; and
determining the required CNR s from a relationship between CNR s and CNR U , CNR L , and S.
6. The method of claim 5 , wherein the required CNR s is determined at least in part from the relation:
10
log
10
10
(
CNR
S
+
S
)
10
1
+
10
S
10
+
10
CNR
S
10
=
10
log
10
10
CNR
S
10
1
+
10
S
10
.
7. The method of claim 1 , wherein the error rate of a upper layer modulated signal BER U =γBER L , wherein γ<1, and wherein:
the method further comprises the step of determining an upper layer CNR compensation β required to produce an upper layer modulated signal error rate BER U defined at least in part by the relationship CNR* U =CNR U +β; and
the step of selecting the remaining system parameters using the determined optimal power separation S comprises the steps of:
determining the required system CNR, CNR s , at least in part from the determined optimal power separation, S, and a relation
10
log
10
10
(
CNR
s
+
S
)
10
1
+
10
S
10
+
10
CNR
s
10
=
10
log
10
10
CNR
s
10
1
+
10
S
10
+
β
.
8. The method of claim 7 , wherein the upper layer CNR compensation β is determined at least in part from a relationship between β and parameters including CNR U and γ.
9. The method of claim 8 , wherein β is determined at least in part from a relationship between β and parameters further including C UL .
10. The apparatus of claim 7 , wherein the upper layer CNR compensation β is determined at least in part from a relationship between β and parameters including CNR U and γ.
11. The apparatus of claim 8 , wherein β is determined at least in part from a relationship between β and parameters further including C UL .
12. An apparatus for optimizing a system for transmitting a layered modulated signal, comprising:
means for defining the system in terms of system parameters, including an optimal power separation S between a power of a first modulation layer and a power of a second modulation layer and a required system carrier-to-noise ratio (CNR S );
means for determining an optimal power separation S to minimize an error rate of a lower layer modulated signal BER L ; and
means for selecting remaining system parameters using the determined optimal power separation S.
13. The apparatus of claim 12 , wherein:
the layered modulation signal comprises an upper layer signal and a lower layer signal, and
the means for selecting the remaining system parameters using the determined optimal power separation P x comprises:
means for determining a required CNR for the upper layer (CNR U ) and a required CNR for the lower layer (CNR L ) from a relationship between an upper layer coding rate C UL and CNR U , and a lower level coding rate C LL and CNR L ; and
means for determining a required system CNR (CNR s ) from CNR U , CNR L , and S.
14. The apparatus of claim 13 , wherein the required CNR s is determined at least in part from the relations:
CNR
U
=
10
log
10
10
(
CNR
s
+
S
)
10
1
+
10
S
10
+
10
CNR
s
10
;
and
CNR
L
=
10
log
10
10
CNR
s
10
1
+
10
S
10
,
wherein (CNR s ) from CNR U , CNR L , and S are expressed in decibels.
15. The apparatus of claim 13 , wherein C UL =C LL .
16. The apparatus of claim 13 , wherein C UL ≠C LL and wherein the means for determining a required system CNR (CNR s ) from CNR U , CNR L , and P x , comprises:
means for selecting a value for CNR U and a value for CNR L ; and
means for determining the required CNR s from a relationship between CNR s and CNR U , CNR L , and S.
17. The apparatus of claim 13 , wherein the required CNR s is determined at least in part from the relation:
10
log
10
10
(
CNR
s
+
S
)
10
1
+
10
S
10
+
10
CNR
s
10
=
10
log
10
10
CNR
s
10
1
+
10
S
10
.
18. The apparatus of claim 12 , wherein the error rate of a upper layer modulated signal BER U =γBER L , wherein γ<1, and wherein:
the apparatus further comprises means for determining an upper layer CNR compensation β required to produce an upper layer modulated signal error rate BER U defined at least in part by the relationship CNR* U =CNR U +β; and
the means for selecting the remaining system parameters using the determined optimal power separation S comprises:
means for determining the required system CNR, CNR s , at least in part from the determined optimal power separation, S, and a relation
10
log
10
10
(
CNR
s
+
S
)
10
1
+
10
S
10
+
10
CNR
s
10
=
10
log
10
10
CNR
s
10
1
+
10
S
10
+
β
.
19. An system for transmitting a layered modulation signal characterized by a CNR of CNR s having an upper layer signal characterized and a lower layer signal, wherein a power of the upper layer signal is separated by a power of the lower layer signal by a power separation S, the apparatus defined by performing the steps of:
defining the system in terms of a set of system parameters, including an optimal power separation S between a power of a first modulation layer and a power of a second modulation layer and a required system carrier-to-noise ratio (CNR S );
determining an optimal power separation S to minimize an error rate of a lower layer modulated signal BER L ; and
selecting remaining system parameters in the set of system parameters using the determined optimal power separation S.