Systems and methods for frame synchronization

• US 8,935,160 B2
• Filed: 09/02/2011
• Issued: 01/13/2015
• Est. Priority Date: 09/02/2011
• Status: Active Grant

• Current Assignee: Harris Global Communications, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Nair, Sujit, Amirapu, Sree B., Peterson, Eugene H.
• Primary Examiner(s): YEN, ERIC L
• Application Number:
  US13/224,622
• Publication Number:
  US 20130060565A1
• Time in Patent Office: 1,229 Days
• US Class Current: 704/228
• CPC Class Codes: H04B 7/2643 using time-division multiple access [TDMA] H04B7/2615, H04B7/2618 take precedence
• CPC Class Codes: H04L 1/0047 Decoding adapted to other signal detection operation in conjunction with sequence estimation or equalization H04L25/03286
• CPC Class Codes: H04L 1/203 Details of error rate determination, e.g. BER, FER or WER
• CPC Class Codes: H04L 7/048 using the properties of error detecting or error correcting codes, e.g. parity as synchronisation signal

Abstract

Systems (1600) and methods (1500) for frame synchronization. The methods involve: extracting bit sequences S₀ and S₁ from a Bit Stream (“BS”) of a Data Burst (“DB”); decoding S₀ and S₁ to obtain decoded bit sequences S′₀ and S′₁; using S′₀ and S′₁ to determine Bit Error Rate (“BER”) estimates (516, 518); combining the BER estimates to obtain a combined BER estimate; modifying S₀ and S₁ so that each includes at least one bit of BS which is not included in its current set of bits and so that it is absent of at least one of the bits in the current set of bits; iteratively repeating the decoding, using, combining and modifying steps to obtain more combined BER estimates; analyzing the combined BER estimates to identify a minimum combined BER estimate; and using the minimum combined BER estimate to determine a location of a vocoder voice frame within DB.

Claims

1. A method for frame synchronization between a transmitting device and a receiving device, comprising:

extracting, by an electronic circuit, two different bit sequences from a bit stream of a data burst received by the electronic circuit, where a first bit sequence of the two different bit sequences comprises a plurality of first bits of the bit stream that is different than a plurality of second bits of the bit stream, where the plurality of second bits is contained in a second bit sequence of the two different bit sequences;

decoding, by the electronic circuit, the two different bit sequences to obtain two decoded bit sequences;

using, by the electronic circuit, a first decoded bit sequence from the two decoded bit sequences to determine a first Bit Error Rate (“

BER”

) estimate for a vocoder voice frame;

using, by the electronic circuit, a second decoded bit sequence from the two decoded bit sequences to determine a second BER estimate for the vocoder voice frame;

combining, by the electronic circuit, the first and second BER estimates to obtain a first combined BER estimate;

generating, by the electronic circuit, a third bit sequence by modifying the first bit sequence of the two different bit sequences so that the first bit sequence includes at least one bit of the bit stream which is not included in the plurality of first bits and so that the first bit sequence is absent of at least one of the plurality of first bits;

generating, by the electronic circuit, a fourth bit sequence by modifying the second bit sequence of the two different bit sequences so that the second bit sequence includes at least one bit of the bit stream which is not included in the plurality of second bits and so that the second bit sequence is absent of at least one of the plurality of second bits;

repeating the decoding, using, and combining steps by the electronic circuit to obtain a second combined BER estimate for the third and fourth bit sequences;

analyzing, by the electronic circuit, the first combined BER estimate and the second combined BER estimate to identify a minimum combined BER estimate therefrom; and

using, by the electronic circuit, the minimum combined BER estimate to determine a location of the vocoder voice frame within the data burst.

2. The method according to claim 1, wherein the first BER estimate is determined by:

comparing, by the electronic circuit, the first bit sequence with the respective one of the two decoded bit sequences to identify bit values of the first bit sequence which were changed during a decoding process; and

counting, by the electronic circuit, the number of bit values which were changed during the decoding process.

3. The method according to claim 2, wherein the first BER estimate is further determined by dividing the number of bit values by a total number of bits contained in the first bit sequence.

4. The method according to claim 1, wherein the first combined BER estimate is obtained by adding the first and second BER estimates together.

5. The method according to claim 1, wherein the first combined BER estimate is obtained by computing an average of the first and second BER estimates.

6. The method according to claim 1, wherein the minimum combined BER estimate is identified by selecting a combined BER estimate with a relatively low value from the first combined BER estimate and the second combined BER estimate.

7. The method according to claim 1, wherein the minimum combined BER estimate is identified by selecting, from the first combined BER estimate and the second combined BER estimate, a combined BER estimate that has a value less than a threshold value.

8. The method according to claim 7, wherein the threshold is selected to maximize a probability of detection of a correct location of the vocoder voice frame within the data burst and minimize a probability of a false detection of the correct location of the vocoder voice frame.

9. The method according to claim 7, wherein the bit stream of the data burst is discarded if none of the first combined BER estimate and the second combined BER estimate has a value that is less than the threshold.

10. The method according to claim 1, wherein a start bit of the vocoder voice frame comprises a bit contained in the first bit sequence and wherein an end bit of the vocoder voice frame comprises a bit contained in the second bit sequence.

11. A system for frame synchronization between a transmitting device and a receiving device, comprising:

at least one electronic circuit configured to

extract two different bit sequences from a bit stream of a received data burst, where a first bit sequence of the two different bit sequences comprises a plurality of first bits of the bit stream that is different than a plurality of second bits of the bit stream, where the plurality of second bits is contained in a second bit sequence of the two different bit sequences;

decode the two different bit sequences to obtain two decoded bit sequences;

use a first decoded bit sequence from the two decoded bit sequence to determine a first Bit Error Rate (“

BER”

) estimate for a vocoder voice frame;

use a second decoded bit sequence from the two decoded bit sequence to determine a second BER estimate for the vocoder voice frame; and

combine the first and second BER estimates to obtain a first combined BER estimate;

generate a third bit sequence by modifying the first bit sequence from the two different bit sequences so that the first bit sequence includes at least one bit of the bit stream which is not included in the plurality of first bits and so that the first bit sequence is absent of at least one of the plurality of first bits;

generate a fourth bit sequence by modifying the second bit sequence of the two different bit sequences so that the second bit sequence includes at least one bit of the bit stream which is not included in the plurality of second bits and so that the second bit sequence is absent of at least one of the plurality of second bits;

repeat the decoding, using, and combining steps to obtain a second combined BER estimate for the third and fourth bit sequences;

analyze the first combined BER estimate and the second combined BER estimate to identify a minimum combined BER estimate therefrom; and

use the minimum combined BER estimate to determine a location of the vocoder voice frame within the data burst.

12. The system according to claim 11, wherein the first BER estimate is determined by:

comparing the first bit sequence with the respective one of the two decoded bit sequences to identify bit values of the first bit sequence which were changed during a previous decoding process; and

counting the number of bit values which were changed during the previous decoding process.

13. The system according to claim 12, wherein the first BER estimate is further determined by dividing the number of bit values by a total number of bits contained in the first bit sequence.

14. The system according to claim 11, wherein the first combined BER estimate is the sum of the first and second BER estimates together.

15. The system according to claim 11, wherein the first combined BER estimate is an average of the first and second BER estimates.

16. The system according to claim 11, wherein the minimum combined BER estimate comprises a combined BER estimate with a relatively low value that is selected from the first combined BER estimate and the second combined BER estimate.

17. The system according to claim 11, wherein the minimum combined BER estimate comprises a combined BER estimate which has a value less than a threshold value and is selected from the first combined BER estimate and the plurality of second combined BER estimates.

18. The system according to claim 17, wherein the threshold is selected to maximize a probability of detection of a correct location of the vocoder voice frame within the data burst and minimize a probability of a false detection of the correct location of the vocoder voice frame.

19. The system according to claim 17, wherein the electronic circuit is further configured to discard the bit stream of the data burst if none of the first combined BER estimate and the second combined BER estimate has a value that is less than the threshold.

20. The system according to claim 11, wherein said electronic circuit is further configured to select a bit, contained in the first or second bit sequence, which is associated with the minimum combined BER estimate to be a start bit or an end bit of the vocoder voice frame.

21. A method for frame synchronization between a transmitting device and a receiving device, comprising:

determining, by an electronic circuit, a plurality of first combined Bit Error Rate (“

BER”

) estimates for a first vocoder voice frame;

determining, by the electronic circuit, a plurality of second combined BER estimates for a second vocoder voice frame;

combining, by the electronic circuit, the plurality of first combined BER estimates with the plurality of second combined BER estimates to obtain a plurality of third combined BER estimates;

analyzing, by the electronic circuit, the third combined BER estimates to identify a lowest combined BER estimate therefrom; and

using, by the electronic circuit, the lowest combined BER estimate to determine the locations of the first and second vocoder voice frames within a data burst received by the electronic circuit.

22. The method according to claim 21, wherein each of the plurality of first and second combined BER estimates is determined by extracting, by the electronic circuit, two different bit sequences from a bit stream of said data burst, where a first bit sequence of the two different bit sequences comprises a plurality of first bits of the bit stream that is different than a plurality of second bits of the bit stream, where the plurality of second bits is contained in a second bit sequence of the two different bit sequences,

decoding, by the electronic circuit, the two different bit sequences to obtain two decoded bit sequences,

using, by the electronic circuit, a first decoded bit sequence from the two decoded bit sequences-to determine a first BER estimate for a respective one of the first and second vocoder voice frames,

using, by the electronic circuit, a second decoded bit sequence from the two decoded bit sequences to determine a second BER estimate for the respective one of the first and second vocoder voice frames, and

combining, by the electronic circuit, the first and second BER estimates to obtain a combined BER estimate of the plurality of first or second combined BER estimates.