Optimization technique for layered modulation

• US 7,184,489 B2
• Filed: 10/24/2003
• Issued: 02/27/2007
• Est. Priority Date: 04/27/2001
• Status: Expired due to Term

• Current Assignee: DIRECTV, LLC (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Santoru, Joseph, Chen, Ernest C., Lin, Tung-Sheng, Zhou, Guangcai, Lindsey, William C., Wang, Weizheng
• Primary Examiner(s): Bayard; Emmanuel
• Application Number:
  US10/693,140
• Publication Number:
  US 20040136469A1
• Time in Patent Office: 1,222 Days
• Field of Search: 375/259, 375/260, 375/295, 375/297
• US Class Current: 375/295
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 1/208 involving signal re-encoding
• CPC Class Codes: H04L 27/183 Multiresolution systems
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

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.

Claims

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:

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:

7. The method of claim 1, wherein the error rate of a upper layer modulated signal BER_U=γ

BER_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

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:

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:

18. The apparatus of claim 12, wherein the error rate of a upper layer modulated signal BER_U=γ

BER_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

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.