Control channel decoding of neighboring cells

• US 8,625,516 B2
• Filed: 06/30/2011
• Issued: 01/07/2014
• Est. Priority Date: 06/30/2011
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Lindoff, Bengt, Kamuf, Matthias, Andres, Reial
• Primary Examiner(s): Nguyen, Steven H
• Assistant Examiner(s): Nguyen, Phuongchau B
• Application Number:
  US13/172,908
• Publication Number:
  US 20130003569A1
• Time in Patent Office: 922 Days
• Field of Search: 370/329
• US Class Current: 370/329
• CPC Class Codes: H04J 11/005 of intercell interference
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04W 28/04 Error control

Abstract

A method of determining a radio network temporary identifier (RNTI) includes descrambling a control channel, decoding control messages included in the control channel wherein the decoded control messages include control bits and received cyclic redundancy check (CRC) bits, generating a CRC from the decoded control bits, determining the RNTI from the generated CRC and received CRC and utilizing the RNTI for decoding subsequent subframes.

Claims

1. A method in a user equipment for determining a radio network temporary identifier (RNTI), the method comprising the steps of:

descrambling a control channel;

decoding control messages included in the control channel wherein the decoded control messages include control bits and received cyclic redundancy check (CRC) bits;

generating a CRC from the decoded control bits;

determining the RNTI from the generated CRC and received CRC;

associating a timestamp to the determined RNTI;

storing the determined RNTI with the associated timestamp in a candidate RNTI list;

updating a count associated with the determined RNTI;

comparing the count of the RNTI with a pre-specified threshold value;

storing the RNTI in a reliable candidate RNTI list if the count is equal to or greater than the threshold value; and

utilizing the RNTI for decoding subsequent subframes.

2. The method of claim 1, further comprising:

detecting a neighboring cell; and

measuring signal strength on a serving cell of the user equipment and on the detected neighboring cell.

3. The method of claim 2, further comprising:

descrambling sub frames of physical downlink control channels (PDCCHs) originating from the neighboring cell.

4. The method of claim 1, further comprising:

removing RNTIs from the candidate RNTI list if a time lapse from the timestamp of the RNTI in the candidate RNTI list exceeds a first pre-specified time period.

5. The method of claim 1, further comprising:

utilizing a RNTI from the reliable candidate RNTI list to decode subsequent subframes.

6. The method of claim 5, wherein the subsequent subframes are from a cell serving the user equipment.

7. The method of claim 5, wherein the subsequent subframes are from neighboring cells detected by the user equipment.

8. The method of claim 1, further comprising:

assigning a timestamp for the RNTI stored in the reliable candidate RNTI list.

9. The method of claim 8, further comprising:

removing a RNTI from the reliable candidate RNTI list upon a time lapse from the timestamp of the RNTI in the reliable candidate RNTI list exceeding a second pre-specified time period.

10. The method of claim 1, wherein the de-scrambling is based on at least a cell identity and a sub frame number associated with the control channel.

11. The method of claim 1, further comprising:

determining the RNTI by applying an exclusive OR (XOR) function between the generated CRC and the received CRC.

12. The method of claim 1, further comprising:

removing a RNTI from the candidate RNTI list upon placement of the RNTI in the reliable candidate RNTI list.

13. A user equipment comprising:

a receiver for down converting a received radio signal to a baseband signal;

an analog to digital converter for transforming the baseband signal to a digital signal;

a cell search and measuring unit for detecting neighboring cells and for measuring signals on a serving cell and on the detected cells;

a decoder for decoding the digital signal wherein the decoded signal includes control bits and received cyclic redundancy check (CRC) bits;

a control unit for

generating a CRC from the decoded control bits;

determining a radio network temporary identifier candidate (RNTI) from the generated CRC and received CRC; and

associating a timestamp to the determined RNTI; and

a memory for storing the determined RNTI in a candidate RNTI list with an associated timestamp and a count, wherein the control unit is further for;

updating a count associated with the determined RNTI;

comparing the count of the RNTI with a pre-specified threshold value;

storing the RNTI in a reliable candidate RNTI list if the count is equal to or greater than the threshold value; and

utilizing the RNTI for decoding subsequent subframes.

14. The user equipment of claim 13, wherein the control unit is further for:

providing RNTIs from the reliable candidate RNTI list to the decoder for decoding subsequent subframes.

15. The user equipment of claim 13, wherein the control unit is further for:

removing a RNTI from the candidate RNTI list if a time lapse from the timestamp associated with the RNTI in the candidate RNTI list exceeds a first pre-determined threshold.

16. The user equipment of claim 13, wherein the control unit is further for:

removing a RNTI from the reliable candidate RNTI list if a time lapse from the timestamp associated with the RNTI exceeds a second pre-determined threshold.

17. The user equipment of claim 13, wherein the control unit is further for:

removing a RNTI from the candidate RNTI list upon placement of the RNTI in the reliable candidate RNTI list.

18. A computer program comprising non-transitory computer readable program modules which when run on a user terminal causes the user terminal to:

descramble a control channel;

decode control messages included in the control channel wherein the decoded control messages include control bits and received cyclic redundancy check (CRC) bits;

generate a CRC from the decoded control bits;

determine the RNTI from the generated CRC and received CRC;

associate a timestamp to the determined RNTI;

store the determined RNTI with the associated timestamp in a candidate RNTI list;

update a count associated with the determined RNTI;

compare the count of the RNTI with a pre-specified threshold value;

store the RNTI in a reliable candidate RNTI list if the count is equal to or greater than the threshold value; and

utilize the RNTI for decoding subsequent subframes.