Symbol error detection for bluetooth enhanced data rate packets

• US 8,401,120 B1
• Filed: 05/13/2010
• Issued: 03/19/2013
• Est. Priority Date: 05/13/2010
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ozgur, Soner
• Primary Examiner(s): Timory, Kabir A
• Application Number:
  US12/779,209
• Time in Patent Office: 1,041 Days
• Field of Search: 375/329, 375/331, 375/332, 375/340, 375/373, 375/376
• US Class Current: 375/329
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes 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 1/0061 Error detection codes
• CPC Class Codes: H04L 1/205 jitter monitoring

Abstract

A symbol error detector can be configured to detect symbol errors of a Bluetooth enhanced data rate (EDR) packet without relying solely on a CRC error detection mechanism. After a phase of a current symbol is demodulated to determine a demodulated current symbol, the phase of the demodulated current symbol can be subtracted from the phase of the current symbol prior to demodulation to yield a phase error. The phase error can be compared against a phase error threshold to determine a potential unreliability of the demodulated current symbol. The phase error being greater than the phase error threshold can indicate that the demodulated current symbol may be unreliable. Accordingly, a symbol error notification can be generated to indicate that the demodulated current symbol may be unreliable.

Claims

1. A method comprising:

determining, at a wireless network device, a phase of a first symbol of a received signal;

determining, based on comparing the phase of the first symbol to a plurality of predefined phases, that the phase of the first symbol is within a predetermined threshold of a first of the plurality of predefined phases, wherein each of the plurality of predefined phases is associated with a corresponding each of a plurality of predefined symbols;

demodulating the first symbol to a first of the plurality of predefined symbols associated with the first of the plurality of predefined phases based on said determining that the phase of the first symbol is within the predetermined threshold of the first of the plurality of predefined phases;

determining a phase error that indicates a difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases;

determining, based on comparing the phase error with a predetermined phase error threshold, whether the phase error is greater than the predetermined phase error threshold; and

generating a symbol error notification in response to determining that the phase error is greater than the predetermined phase error threshold.

2. The method of claim 1, wherein said determining the phase error that indicates the difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases further comprises:

determining an absolute value of the difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases, or

determining a squared magnitude of the difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases.

3. The method of claim 1, wherein said generating the symbol error notification in response to determining that the phase error is greater than the predetermined phase error threshold further comprises:

determining a number of symbols between a current symbol error and a previously detected symbol error, wherein the current symbol error is associated with the first symbol of the received signal;

comparing the number of symbols between the current symbol error and the previously detected symbol error to a predetermined burst length threshold, wherein the predetermined burst length threshold indicates a minimum number of symbols between two consecutive symbol errors that will cause an erroneously demodulated symbol to be undetected; and

generating the symbol error notification in response to determining that the phase error is greater than the predetermined phase error threshold and that the number of symbols between the current symbol error and the previously detected symbol error is greater than the predetermined burst length threshold.

4. The method of claim 3, further comprising discarding the first symbol based, at least in part, on determining that the phase error is greater than the predetermined phase error threshold and on determining that the number of symbols between the current symbol error and the previously detected symbol error is greater than the predetermined burst length threshold.

5. The method of claim 1, wherein said comparing the phase of the first symbol to the plurality of predefined phases further comprises comparing the phase of the first symbol with symbol phase boundaries associated with the plurality of predefined phases.

6. The method of claim 5, wherein said demodulating the first symbol to the first of the plurality of predefined symbols associated with the first of the plurality of predefined phases further comprises mapping the first symbol to the first of the plurality of predefined symbols associated with the first of the plurality of predefined phases based on determining that the phase of the first symbol lies within symbol phase boundaries associated with the first of the plurality of predefined phases.

7. The method of claim 1, further comprising, for each additional symbol of the received signal:

determining, at the wireless network device, a phase of the additional symbol;

determining, based on comparing the phase of the additional symbol to the plurality of predefined phases, that the phase of the additional symbol is within the predetermined threshold of the first of the plurality of predefined phases;

demodulating the additional symbol to the first of the plurality of predefined symbols associated with the first of the plurality of predefined phases based on said determining that the phase of the additional symbol is within the predetermined threshold of the first of the plurality of predefined phases;

determining a second phase error that indicates a difference between the phase of the additional symbol of the received signal and the first of the plurality of predefined phases;

determining, based on comparing the second phase error with the predetermined phase error threshold, whether the second phase error is greater than the predetermined phase error threshold; and

generating a second symbol error notification in response to determining that the second phase error is greater than the predetermined phase error threshold.

8. The method of claim 1, further comprising applying a phase correction to the phase of the first symbol of the received signal, wherein the phase correction is determined, at least in part, on a frequency offset and a phase offset associated with a packet that comprises the first symbol.

9. The method of claim 8, further comprising recalculating the phase correction based, at least in part, on the phase error.

10. The method of claim 1, further comprising discarding the first symbol and a packet that comprises the first symbol based, at least in part, on said determining that the phase error is greater than the predetermined phase error threshold.

11. The method of claim 1, wherein the received signal is modulated using π

/4 rotated differential encoded quadrature phase shift keying (π

/4 DQPSK) or 8-phase differential encoded phase shift keying (8-DPSK).

12. A wireless network device comprising:

a phase detector operable to determine a phase of a first symbol of a received signal;

a symbol demodulator operable to;

determine, based on comparing the phase of the first symbol to a plurality of predefined phases, that the phase of the first symbol is within a predetermined threshold of a first of the plurality of predefined phases, wherein each of the plurality of predefined phases is associated with a corresponding each of a plurality of predefined symbols; and

demodulate the first symbol to a first of the plurality of predefined symbols associated with the first of the plurality of predefined phases based on the symbol demodulator determining that the phase of the first symbol is within the predetermined threshold of the first of the plurality of predefined phases; and

a symbol error detector operable to;

determine a phase error that indicates a difference between the phase of the first symbol in the received signal and the first of the plurality of predefined phases;

determine, based on the symbol error detector comparing the phase error with a predetermined phase error threshold, whether the phase error is greater than the predetermined phase error threshold; and

generate a symbol error notification in response to the symbol error detector determining that the phase error is greater than the predetermined phase error threshold.

13. The wireless network device of claim 12, wherein the symbol error detector operable to determine the phase error that indicates the difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases further comprises:

the symbol error detector operable to determine an absolute value of the difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases, or

the symbol error detector operable to determine a squared magnitude of the difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases.

14. The wireless network device of claim 12, wherein the symbol error detector operable to generate the symbol error notification in response to the symbol error detector determining that the phase error is greater than the predetermined phase error threshold further comprises the symbol error detector operable to:

determine a number of symbols between a current symbol error and a previously detected symbol error, wherein the current symbol error is associated with the first symbol of the received signal;

compare the number of symbols between the current symbol error and the previously detected symbol error to a predetermined burst length threshold, wherein the predetermined burst length threshold indicates a minimum number of symbols between two consecutive symbol errors that will cause an erroneously demodulated symbol to be undetected; and

generate the symbol error notification in response to the symbol error detector determining that the phase error is greater than the predetermined phase error threshold and that the number of symbols between the current symbol error and the previously detected symbol error is greater than the predetermined burst length threshold.

15. The wireless network device of claim 12, wherein the symbol demodulator is further operable to discard the first symbol and a packet that comprises the first symbol based, at least in part, on the symbol error detector determining that the phase error is greater than the predetermined phase error threshold.

16. The wireless network device of claim 12, wherein the phase detector is further operable to apply a phase correction to the phase of the first symbol of the received signal, wherein the phase correction is determined, at least in part, on the phase error.

17. A non-transitory machine-readable storage media, having instructions stored therein, which, when executed by one or more processors causes the one or more processors to perform operations that comprise:

determining a phase of a first symbol of a received signal;

determining, based on comparing the phase of the first symbol to a plurality of predefined phases, that the phase of the first symbol is within a predetermined threshold of a first of the plurality of predefined phases, wherein each of the plurality of predefined phases is associated with a corresponding each of a plurality of predefined symbols;

demodulating the first symbol to a first of the plurality of predefined symbols associated with the first of the plurality of predefined phases based on said determining that the phase of the first symbol is within the predetermined threshold of the first of the plurality of predefined phases;

determining a phase error that indicates a difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases;

determining, based on comparing the phase error with a predetermined phase error threshold, whether the phase error is greater than the predetermined phase error threshold; and

generating a symbol error notification in response to determining that the phase error is greater than the predetermined phase error threshold.

18. The non-transitory machine-readable storage media of claim 17, wherein said operation of determining the phase error that indicates the difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases further comprises:

determining an absolute value of the difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases, or

determining a squared magnitude of the difference between the phase of the first symbol of the received signal and the first of the plurality of predefined phases.

19. The non-transitory machine-readable storage media of claim 17, wherein said operation of generating the symbol error notification in response to determining that the phase error is greater than the predetermined phase error threshold further comprises:

determining a number of symbols between a current symbol error and a previously detected symbol error, wherein the current symbol error is associated with the first symbol of the received signal;

comparing the number of symbols between the current symbol error and the previously detected symbol error to a predetermined burst length threshold, wherein the predetermined burst length threshold indicates a minimum number of symbols between two consecutive symbol errors that will cause an erroneously demodulated symbol to be undetected; and

generating the symbol error notification in response to determining that the phase error is greater than the predetermined phase error threshold and that the number of symbols between the current symbol error and the previously detected symbol error is greater than the predetermined burst length threshold.

20. The non-transitory machine-readable storage media of claim 17, wherein said operation of comparing the phase of the first symbol to the plurality of predefined phases further comprises comparing the phase of the first symbol with symbol phase boundaries associated with the plurality of predefined phases.

21. The non-transitory machine-readable storage media of claim 20, wherein said operation of demodulating the first symbol to the first of the plurality of predefined symbols associated with the first of the plurality of predefined phases further comprises mapping the first symbol to the first of the plurality of predefined symbols associated with the first of the plurality of predefined phases based on determining that the phase of the first symbol lies within symbol phase boundaries associated with the first of the plurality of predefined phases.