Optimization technique for layered modulation

• US 7,469,019 B2
• Filed: 01/18/2007
• Issued: 12/23/2008
• Est. Priority Date: 04/27/2001
• Status: Expired due to Fees

• Current Assignee: The DIRECTV Group, Inc. (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:
  US11/655,001
• Publication Number:
  US 20070116144A1
• Time in Patent Office: 705 Days
• Field of Search: 375/260, 375/295, 375/296, 375/297, 375/259
• 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 system for transmitting a layered modulation signal characterized by a carrier to noise ratio (CNR) having an upper layer signal and a lower layer signal, wherein a power of the upper layer signal is separated from a power of the lower layer signal by a power separation S, the system 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 the lower layer signal (BER_L); and

selecting remaining system parameters in the set of system parameters using the determined optimal power separation S, comprising 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 the required system CNR (CNR_s) from CNR_U, CNR_L, and S.

2. The system of claim 1, wherein the required system (CNR_s) is determined at least in part from the relations:

3. The system of claim 1 wherein C_UL=C_LL.

4. The system of claim 1, wherein C_UL≠

C_LL and wherein the step of determining a required system CNR (CNR_s) from CNR_U, CNR_L, and S, comprises the steps of;

selecting a value for CNR_U and a value for CNR_L; and

determining the required system CNR_s from a relationship between CNR_s and CNR_U, CNR_L, and S.

5. The system of claim 4, wherein the required system CNR

(CNR_s) is determined at least in part from the relation:

6. A system for transmitting a layered modulation signal characterized by a carrier to noise ratio (CNR) of CNR_s having an upper layer signal and a lower layer signal, wherein a power of the upper layer signal is separated from a power of the lower layer signal by a power separation S, the system 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 upper layer CNR compensation (β

) required to produce an upper layer signal error rate (BER_U) defined at least in part by the relationship CNR_U*=CNR_U+β

, wherein CNR_U is the upper layer CNR and CNR_U * is an increased upper layer CNR required to achieve a BER_U defined by BER_U=γ

BER_L, wherein BER_L is a bit error rate of the lower layer signal and γ

<

1;

determining an optimal power separation S to minimize BER_L; and

selecting remaining system parameters in the set of system parameters using the determined optimal power separation S, comprising the step of determining the required system CNR (CNR_s) at least in part from the determined optimal power separation, S, and a relation

7. The system of claim 6, 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

.

8. The system of claim 7, wherein β

is determined at least in part from a relationship between β and

parameters further including a coding rate of the upper layer (C_UL).