Reliable Decoding of a High-Speed Shared Control Channel

• US 20090003377A1
• Filed: 11/26/2007
• Published: 01/01/2009
• Est. Priority Date: 06/28/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Andersson, Lennart, Reial, Andres
• Granted Patent: US 9,209,937 B2
• Time in Patent Office: Days
• US Class Current: 370/464
• CPC Class Codes: H03M 13/3738 with judging correct decoding
• CPC Class Codes: H03M 13/3776 using a re-encoding step during the decoding process
• CPC Class Codes: H03M 13/41 using the Viterbi algorithm or Viterbi processors
• CPC Class Codes: H03M 13/653 3GPP HSDPA, e.g. HS-SCCH or DS-DSCH related
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 1/208 involving signal re-encoding

Abstract

Methods and apparatus are disclosed for detecting a control channel message transmitted on one of a plurality of shared control channels and targeted to a wireless receiver. In an exemplary method, messages transmitted over a plurality of shared control channels are decoded, and at least one likelihood metric is determined for each of the decoded messages. A best candidate is selected from the decoded messages, based on the likelihood metrics, and the at least one likelihood metric for the best candidate is compared to corresponding likelihood metrics for the messages other than the best candidate to determine whether the best candidate is a valid message. Wireless communication receivers configured correspondingly are also disclosed.

Claims

1. A method for detecting a control channel message, the method comprising:

decoding messages transmitted over a plurality of shared control channels;

determining at least one likelihood metric for each of the decoded messages;

selecting a best candidate from the decoded messages, based on the likelihood metrics; and

comparing the at least one likelihood metric for the best candidate to the corresponding likelihood metrics for the decoded messages other than the best candidate to determine whether the best candidate is a valid message.

2. The method of claim 1, further comprising generating one or more additional candidate messages and calculating additional likelihood metrics corresponding to the additional candidate messages, wherein comparing the at least one likelihood metric for the best candidate to the corresponding likelihood metrics for the messages other than the best candidate comprises comparing the likelihood metric for the best candidate to the likelihood metrics for the decoded messages other than the best candidate and to the additional likelihood metrics.

3. The method of claim 2, wherein generating one or more additional candidate messages comprises randomly selecting the one or more additional candidate messages from a set of possible messages.

4. The method of claim 2, wherein determining at least one likelihood metric for each of the decoded messages comprises re-encoding the decoded message to obtain a re-encoded bit sequence and correlating the re-encoded bit sequence with a received sequence of soft values corresponding to the decoded message to obtain a correlation value for use as the at least one likelihood metric, and wherein calculating additional likelihood metrics corresponding to the additional candidate messages comprises encoding the additional candidate messages and correlating the encoded additional candidate messages with the received sequence of soft values to obtain the additional likelihood metrics.

5. The method of claim 2, wherein generating one or more additional candidate messages comprises selecting one or more frequently used messages for use as additional candidate messages.

6. The method of claim 2, wherein generating one or more additional candidate messages comprises determining one or more next-most-likely decoding results corresponding to one or more of the decoded messages.

7. The method of claim 6, wherein determining one or more next-most-likely decoding results comprises perturbing an information bit sequence corresponding to one of the decoded messages to recover potential lost paths in a reduced-trellis Viterbi decoder.

8. The method of claim 2, further comprising eliminating decoded messages or additional candidate messages having impossible information bit sequences before comparing the likelihood metric for the best candidate to the likelihood metrics for the decoded messages other than the best candidate and to the additional likelihood metrics.

9. The method of claim 1, wherein determining at least one likelihood metric for each of the decoded messages comprises re-encoding the decoded message to obtain a re-encoded bit sequence and correlating the re-encoded bit sequence with a received sequence of soft values corresponding to the decoded message to obtain a correlation value for use as the at least one likelihood metric.

10. The method of claim 9, wherein selecting a best candidate from the decoded messages comprises selecting the message corresponding to a best decoder metric, and wherein comparing the at least one likelihood metric for the best candidate to the corresponding likelihood metrics for the messages other than the best candidate to determine whether the best candidate is a valid message comprises comparing the correlation value for the best candidate to correlation values for the messages other than the best candidate.

11. The method of claim 1, wherein comparing the correlation value for the best candidate to correlation values for the messages other than the best candidate comprises comparing the correlation value for the best candidate to an average of the correlation values for the messages other than the best candidate multiplied by a scaling constant.

12. The method of claim 11, further comprising selecting the scaling constant based on whether a receiving mobile terminal is configured to receive unannounced transmissions on one or more traffic channels corresponding to the shared control channels.

13. The method of claim 11, further comprising selecting the scaling constant based on whether a receiving mobile terminal is configured for multiple-input-multiple-output (MIMO) operation.

14. The method of claim 1, wherein comparing the correlation value for the best candidate to correlation values for the messages other than the best candidate comprises comparing the correlation value for the best candidate to a scaled average of the correlation values for the messages other than the best candidate.

15. The method of claim 1, further comprising selectively (a) decoding a traffic channel using decoding parameters determined from the best candidate or (b) blind decoding one or more traffic channels using one or more pre-determined decoding parameters, based on whether the best candidate is a valid message.

16. The method of claim 15, wherein the plurality of shared control channels comprise High-Speed Shared Control Channels (HS-SCCHs) in a Wideband Code-Division Multiple Access (W-CDMA) system, the traffic channel comprises a High-Speed Physical Downlink Shared Channel (HS-PDSCH), and the messages comprise Part 1 messages of the HS-SCCHs.

17. A wireless communications receiver comprising one or more processing circuits configured to:

detect messages transmitted over a plurality of shared control channels;

determine at least one likelihood metric for each of the decoded messages;

select a best candidate from the decoded messages, based on the likelihood metrics; and

compare the at least one likelihood metric for the best candidate to the corresponding likelihood metrics for the messages other than the best candidate to determine whether the best candidate is a valid message.

18. The wireless communication receiver of claim 17, wherein the one or more processing circuits are further configured to generate one or more additional candidate messages and calculate additional likelihood metrics corresponding to the additional candidate messages, and wherein the one or more processing circuits are configured to compare the at least one likelihood metric for the best candidate to the corresponding likelihood metrics for the messages other than the best candidate comprises by comparing the likelihood metric for the best candidate to the likelihood metrics for the decoded messages other than the best candidate and to the additional likelihood metrics.

19. The wireless communication receiver of claim 18, wherein the one or more processing circuits are configured to generate one or more additional candidate messages by randomly selecting the one or more additional candidate messages from a set of possible messages.

20. The wireless communication receiver of claim 18, wherein the one or more processing circuits are configured to determine at least one likelihood metric for each of the decoded messages by re-encoding the decoded message to obtain a re-encoded bit sequence and correlating the re-encoded bit sequence with a received sequence of soft values corresponding to the decoded message to obtain a correlation value for use as the at least one likelihood metric, and wherein the one or more processing circuits are configured to calculate additional likelihood metrics corresponding to the additional candidate messages by encoding the additional candidate messages and correlating the encoded additional candidate messages with the received sequence of soft values to obtain the additional likelihood metrics.

21. The wireless communication receiver of claim 18, wherein the one or more processing circuits are configured to generate one or more additional candidate messages by perturbing an information bit sequence corresponding to one of the decoded messages to recover potential lost paths in a reduced-trellis Viterbi decoder.

22. The wireless communication receiver of claim 18, wherein the one or more processing circuits are further configured to eliminate decoded messages or additional candidate messages having impossible information bit sequences before comparing the likelihood metric for the best candidate to the likelihood metrics for the decoded messages other than the best candidate and to the additional likelihood metrics.

23. The wireless communication receiver of claim 17, wherein the one or more processing circuits are configured to determine the at least one likelihood metric for each of the decoded messages by re-encoding the decoded message to obtain a re-encoded bit sequence and correlating the re-encoded bit sequence with a received sequence of soft values corresponding to the decoded message to obtain a correlation value for use as the at least one likelihood metric.

24. The wireless communication receiver of claim 23, wherein the one or more processing circuits are configured to select a best candidate from the decoded messages by selecting the message corresponding to a best decoder metric, and wherein the one or more processing circuits are configured to compare the at least one likelihood metric for the best candidate to the corresponding likelihood metrics for the messages other than the best candidate to determine whether the best candidate is a valid message by comparing the correlation value for the best candidate to correlation values for the messages other than the best candidate.

25. The wireless communication receiver of claim 17, wherein the one or more processing circuits are further configured to selectively (a) decode a traffic channel using decoding parameters determined from the best candidate or (b) blindly decode one or more traffic channels using one or more pre-determined decoding parameters, based on whether the best candidate is a valid message.