Re-acquisition of symbol index in the presence of sleep timer errors for mobile multimedia multicast systems

• US 7,940,865 B2
• Filed: 04/04/2008
• Issued: 05/10/2011
• Est. Priority Date: 04/04/2008
• Status: Expired due to Fees

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Newport Media Inc. (Nexstar Media Group, Inc.)
• Inventors: Yousef, Nabil
• Primary Examiner(s): Corrielus; Jean B
• Application Number:
  US12/062,712
• Publication Number:
  US 20090252238A1
• Time in Patent Office: 1,131 Days
• Field of Search: 375259-260, 375/316, 375/342, 375/377, 370/203, 370/206, 340/10.33, 340/539.3
• US Class Current: 375/342
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols
• CPC Class Codes: H04L 27/2695 with channel estimation, e.g. determination of delay spread, derivative or peak tracking channel estimation H04L25/0202

Abstract

A technique for re-acquiring a symbol index in the presence of sleep timer errors in a MediaFLO™ (Forward Link Only) mobile multimedia multicast system comprising a receiver and a transmitter, wherein the method comprises receiving a digital signal comprising a superframe comprising one or more Orthogonal Frequency Division Multiplexing (OFDM) symbols in the receiver comprising a timer; waking up the receiver from a sleep mode of operation by an amount of time equal to a maximum error introduced by the timer plus a time to reacquire a beginning of each OFDM symbol plus a time to reacquire a symbol index; and reacquiring the symbol index.

Claims

1. A method for re-acquiring a symbol index in a presence of sleep timer errors in a mobile multimedia multicast system, said method comprising:

receiving a digital signal comprising a superframe comprising a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols in a receiver that is in a sleep mode of operation, wherein said receiver comprises a timer;

waking up said receiver from said sleep mode of operation by an amount of time equal to a maximum error introduced by said timer plus a time to reacquire a beginning of each OFDM symbol plus a time to reacquire the symbol index; and

reacquiring said symbol index.

2. The method of claim 1, further comprising:

setting an index search space;

setting a first index in said index search space as said symbol index;

generating a local copy of Frequency Division Multiplexing (FDM) pilots that belong to a received symbol depending on said symbol index and whether said OFDM belongs to wide area or local area symbols;

dividing said FDM pilots of said received symbol by said local copy of said FDM pilots;

computing an Inverse Fast Fourier Transform (IFFT) process of the result of the division process to get a time-domain channel estimate; and

computing a sparseness index for each said time-domain channel estimate of said plurality of OFDM symbols.

3. The method of claim 2, further comprising determining whether an index value is positioned last in said index search space.

4. The method of claim 3, further comprising setting a second value in said search space as said index value.

5. The method of claim 2, further comprising obtaining an OFDM symbol number of an index having a maximum sparseness value.

6. The method of claim 5, wherein said OFDM symbol number alerts said receiver to wake up when a required Multicast Logical Channel (MLC) arrives in said receiver.

7. The method of claim 1, wherein said superframe comprises an Overhead Information System (OIS) channel, a Multicast Logical Channel (MLC), and multiple Frequency Division Multiplexing (FDM) pilots.

8. The method of claim 1, wherein said plurality of symbols comprises Frequency Division Multiplexing (FDM) pilots.

9. An apparatus for re-acquiring a symbol index in a presence of sleep timer errors in a mobile multimedia multicast system, said apparatus comprising:

a receiver that is in a sleep mode of operation and adapted to receive a digital signal comprising a superframe comprising a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols, wherein said receiver comprises a timer;

a processor adapted to (i) wake up said receiver from said sleep mode of operation by an amount of time equal to a maximum error introduced by said timer plus a time to reacquire a beginning of each OFDM symbol plus a time to reacquire the symbol index; and

(ii) reacquire said symbol index.

10. The apparatus of claim 9, wherein said processor is further adapted to:

set an index search space;

set a first index in said index search space as said symbol index;

generate a local copy of Frequency Division Multiplexing (FDM) pilots that belong to a received symbol depending on said symbol index and whether said OFDM belongs to wide area or local area symbols;

divide said FDM pilots of said received symbol by said local copy of said FDM pilots;

compute an Inverse Fast Fourier Transform (IFFT) process of the result of the division process to get a time-domain channel estimate; and

compute a sparseness index for each said time-domain channel estimate of said plurality of OFDM symbols.

11. The apparatus of claim 10, wherein said processor is further adapted to determine whether an index value is positioned last in said index search space.

12. The apparatus of claim 11, wherein said processor is further adapted to set a second value in said search space as said index value.

13. The apparatus of claim 10, wherein said receiver is further adapted to obtain an OFDM symbol number of an index having a maximum sparseness value.

14. The apparatus of claim 13, wherein said OFDM symbol number alerts said receiver to wake up when a required Multicast Logical Channel (MLC) arrives in said receiver.

15. The apparatus of claim 9, wherein said superframe comprises an Overhead Information System (OIS) channel, a Multicast Logical Channel (MLC), and multiple Frequency Division Multiplexing (FDM) pilots.

16. The apparatus of claim 9, wherein said plurality of symbols comprises Frequency Division Multiplexing (FDM) pilots.

17. A non-transitory program storage device readable by computer, tangibly embodying a program of instructions that, when executed by said computer, cause the computer to perform a method for re-acquiring a symbol index in a presence of sleep timer errors in a mobile multimedia multicast system, said method comprising:

receiving a digital signal comprising a superframe comprising a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols in a receiver that is in a sleep mode of operation, wherein said receiver comprises a timer;

waking up said receiver from said sleep mode of operation by an amount of time equal to a maximum error introduced by said timer plus a time to reacquire a beginning of each OFDM symbol plus a time to reacquire the symbol index; and

reacquiring said symbol index.

18. The program storage device of claim 17, wherein said method further comprises:

setting an index search space;

setting a first index in said index search space as said symbol index;

generating a local copy of Frequency Division Multiplexing (FDM) pilots that belong to a received symbol depending on said symbol index and whether said OFDM belongs to wide area or local area symbols;

dividing said FDM pilots of said received symbol by said local copy of said FDM pilots;

computing an Inverse Fast Fourier Transform (IFFT) process of the result of the division process to get a time-domain channel estimate; and

computing a sparseness index for each said time-domain channel estimate of said plurality of OFDM symbols.

19. The program storage device of claim 18, wherein said method further comprises:

determining whether an index value is positioned last in said index search space;

setting a second value in said search space as said index value; and

obtaining an OFDM symbol number of an index having a maximum sparseness value.

20. The program storage device of claim 18, wherein said method further comprises obtaining an OFDM symbol number of an index having a maximum sparseness value, wherein said OFDM symbol number alerts said receiver to wake up when a required Multicast Logical Channel (MLC) arrives in said receiver.