METHOD AND APPARATUS FOR PERFORMING RANDOM ACCESS IN A WIRELESS COMMUNICATION SYSTEM

• US 20070291696A1
• Filed: 06/15/2007
• Published: 12/20/2007
• Est. Priority Date: 06/19/2006
• Status: Abandoned Application

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Zhang, Guodong, Pan, Kyle, Tsai, Allan
• Application Number:
  US11/763,862
• Publication Number:
  US 20070291696A1
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04J 3/0602 Systems characterised by the synchronising information used
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/26132 using repetition
• CPC Class Codes: H04L 27/26134 Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601

Abstract

A method and apparatus for random access in an evolved universal terrestrial radio access (E-UTRA) system are disclosed. For code division multiplexing (CDM), a basic preamble is generated using a constant amplitude zero auto-correlation (CAZAC) sequence. The basic preamble is repeated for M time for generating a random access channel (RACH) preamble. For time division multiplexing/frequency division multiplexing (TDM/FDM), an extended CAZAC sequence is used to generate the basic preamble. Alternatively, a hybrid RACH access period including at least one CDM random access slot and at least one TDM/FDM random access slot may be provided. For synchronized random access, a RACH burst including a preamble part, a message part, and two cyclic prefixes may be generated and transmitted

Claims

1. A method for random access in a wireless communication system including a wireless transmit/receive unit (WTRU) and a Node-B, the method comprising:

the WTRU generating a constant amplitude zero auto-correlation (CAZAC) sequence;

the WTRU performing a discrete Fourier transform (DFT) on the CAZAC sequence to generate a frequency domain sequence;

the WTRU mapping the frequency domain sequence to subcarriers;

the WTRU performing inverse discrete Fourier transform (IDFT) on the subcarrier mapped frequency domain sequence to generate a basic preamble;

the WTRU repeating the basic preamble for M times to generate a random access channel (RACH) preamble; and

the WTRU transmitting the RACH preamble to the Node-B.

2. The method of claim 1 wherein the CAZAC sequence is a generalized chirp like (GCL) sequence.

3. The method of claim 1 wherein a RACH access slot for transmitting the RACH preamble is for duration of at least one RACH preamble.

4. The method of claim 1 wherein a RACH access slot for transmitting the RACH preamble is no less than one RACH preamble plus maximum uplink timing difference between two WTRUs.

5. The method of claim 1 further comprising:

the Node-B generating RACH preamble samples using a search window;

the Node-B performing DFT on the RACH preamble samples to generate frequency domain data;

the Node-B performing subcarrier demapping on the frequency domain data;

the Node-B down-sampling the subcarrier demapped frequency domain data to generate down-sampled data;

the Node-B performing correlation of the down-sampled data with a conjugate of a corresponding RACH preamble to generate frequency domain correlation values;

the Node-B performing IDFT on the frequency domain correlation values to generate time-domain correlation values; and

the Node-B detecting the RACH preamble based on a ratio of the time-domain correlation values to a noise variance.

6. The method of claim 5 wherein both stage 1 correlation and stage 2 correlation are performed, the stage 1 correlation being performed to detect a rough peak with a shorter search window and the stage 2 correlation being performed to detect a more precise peak with a longer search window based on the rough peak.

7. The method of claim 5 wherein only stage 2 correlation with a longer search window is performed.

8. The method of claim 5 further comprising:

the Node-B performing interference cancellation.

9. The method of claim 8 wherein at each random access slot, the Node-B decodes regular uplink data channel signals first, and removes the received uplink data channel signals before processing the RACH preamble samples.

10. The method of claim 8 wherein the Node-B, after finding specific user timing, uses the detected timing to further perform intra-cell interference cancellation.

11. The method of claim 8 wherein the Node-B performs successive interference cancellation.

12. A method for random access in a wireless communication system including a wireless transmit/receive unit (WTRU) and a Node-B, the method comprising:

the WTRU generating an extended constant amplitude zero auto-correlation (CAZAC) sequence with a CAZAC sequence and an orthogonal sequence;

the WTRU mapping the extended CAZAC sequence to subcarriers;

the WTRU performing inverse discrete Fourier transform (IDFT) on the subcarrier mapped extended CAZAC sequence to generate a basic preamble;

the WTRU repeating the basic preamble for M times to generate a random access channel (RACH) preamble; and

the WTRU transmitting the RACH preamble to the Node-B within a RACH access slot with a guard time, the RACH access slot being defined with respect to at least one of frequency band and time duration of at least one sub-frame.

13. The method of claim 12 further comprising:

the WTRU performing a discrete Fourier transform (DFT) on the extended CAZAC sequence before performing subcarrier mapping.

14. The method of claim 12 wherein the guard time covers a maximum propagation round-trip delay and a small time that is equal to a cyclic prefix (CP) used in an uplink shared channel.

15. The method of claim 12 further comprising:

the Node-B generating RACH preamble samples using a search window;

the Node-B performing DFT on the RACH preamble samples to generate frequency domain data;

the Node-B performing subcarrier demapping on the frequency domain data;

the Node-B down-sampling the subcarrier demapped frequency domain data to generate down-sampled data;

the Node-B performing correlation of the down-sampled data with a conjugate of a corresponding RACH preamble to generate frequency domain correlation values;

the Node-B performing IDFT on the frequency domain correlation values to generate time-domain correlation values; and

the Node-B detecting the RACH preamble based on a ratio of the time-domain correlation values to a noise variance.

16. A method for random access in a wireless communication system including a wireless transmit/receive unit (WTRU) and a Node-B, the method comprising:

defining a hybrid RACH access period, the hybrid RACH access period including at least one code division multiplexing (CDM) random access slot and at least one time division multiplexing (TDM)/frequency division multiplexing (FDM) random access slot;

the WTRU generating a RACH preamble; and

the WTRU transmitting the RACH preamble via either the CDM random access slot or the TDM/FDM random access slot.

17. A method for random access in a wireless communication system including a wireless transmit/receive unit (WTRU) and a Node-B, the method comprising:

the WTRU generating a random access channel (RACH) burst, the RACH burst comprising a preamble part, a message part, a first cyclic prefix (CP) attached to the preamble part and a second CP attached to the message part, the preamble part comprising M repetition of a basic preamble and a guard time and carrying an implicit message; and

the WTRU sending the RACH burst in synchronization with the Node-B.

18. The method of claim 17 wherein the message part occupies subcarriers in one of a distributed mode and a localized mode.

19. The method of claim 17 wherein the preamble part occupies a bandwidth wider than a defined random access region such that the Node-B obtains a channel quality indicator (CQI) of more resource blocks.

20. A wireless transmit/receive unit (WTRU) for random access in a wireless communication system, the WTRU comprising:

a constant amplitude zero auto-correlation (CAZAC) sequence generator for generating a CAZAC sequence;

a discrete Fourier transform (DFT) unit for performing DFT on the CAZAC sequence to generate a frequency domain sequence;

a subcarrier mapping unit for mapping the frequency domain sequence to subcarriers;

an inverse discrete Fourier transform (IDFT) unit for performing IDFT on the subcarrier mapped frequency domain sequence to generate a basic preamble;

a repeater for repeating the basic preamble for M times to generate a random access channel (RACH) preamble; and

a transmitter for transmitting the RACH preamble to a Node-B.

21. The WTRU of claim 20 wherein the CAZAC sequence is a generalized chirp like (GCL) sequence.

22. The WTRU of claim 20 wherein a RACH access slot for transmitting the RACH preamble is for duration of at least one RACH preamble.

23. The WTRU of claim 20 wherein a RACH access slot for transmitting the RACH preamble is no less than one RACH preamble plus maximum uplink timing difference between two WTRUs.

24. A Node-B for processing random access channel (RACH) from a wireless transmit/receive unit (WTRU), the Node-B comprising:

a receiver for generating RACH preamble samples using a search window, the RACH preamble being generated by repeating a basic preamble for M times, the basic preamble being generated from a constant amplitude zero auto-correlation (CAZAC) sequence;

a discrete Fourier transform (DFT) unit for performing DFT on the RACH preamble samples to generate frequency domain data;

a subcarrier demapping unit for performing subcarrier demapping on the frequency domain data;

a down-sampler for down-sampling the subcarrier demapped frequency domain data to generate down-sampled data;

a correlator for performing correlation of the down-sampled data with a conjugate of a corresponding RACH preamble to generate frequency domain correlation values;

an inverse discrete Fourier transform (DFT) unit for performing IDFT on the frequency domain correlation values to generate time domain correlation values; and

a RACH preamble detector for detecting the RACH preamble based on a ratio of the time domain correlation values to a noise variance.

25. The Node-B of claim 24 wherein both stage 1 correlation and stage 2 correlation are performed, the stage 1 correlation being performed to detect a rough peak with a shorter search window and the stage 2 correlation being performed to detect a more precise peak with a longer search window based on the rough peak.

26. The Node-B of claim 24 wherein only stage 2 correlation with a longer search window is performed.

27. The Node-B of claim 24 further comprising:

an interference cancellation unit for performing interference cancellation.

28. The Node-B of claim 27 wherein at each random access slot, the interference cancellation unit removes received uplink data channel signals before processing the RACH preamble samples.

29. The Node-B of claim 27 wherein the interference cancellation unit, after finding specific user timing, uses the detected timing to further perform intra-cell interference cancellation.

30. The Node-B of claim 27 wherein the interference cancellation unit performs successive interference cancellation.

31. A wireless transmit/receive unit (WTRU) for random access in a wireless communication system, the WTRU comprising:

an extended constant amplitude zero auto-correlation (CAZAC) sequence generator for generating an extended CAZAC sequence with a CAZAC sequence and an orthogonal sequence;

a subcarrier mapping unit for mapping the extended CAZAC sequence to subcarriers;

an inverse discrete Fourier transform (IDFT) unit for performing IDFT on the subcarrier mapped extended CAZAC sequence to generate a basic preamble;

a repeater for repeating the basic preamble for M times to generate a random access channel (RACH) preamble; and

a transmitter for transmitting the RACH preamble to a Node-B within a RACH access slot with a guard time, the RACH access slot being defined with respect to at least one of frequency band and time duration of at least one sub-frame.

32. The WTRU of claim 31 further comprising:

a discrete Fourier transform (DFT) unit for performing DFT on the extended CAZAC sequence before performing subcarrier mapping.

33. The WTRU of claim 31 wherein the guard time covers maximum propagation round-trip delay and a small time that is equal to a cyclic prefix (CP) used in an uplink shared channel.

34. A wireless transmit/receive unit (WTRU) for random access in a wireless communication system, the WTRU comprising:

a random access channel (RACH) preamble generator for generating a RACH preamble; and

a transmitter for transmitting the RACH preamble during a hyper RACH access period, the hyper RACH access period including at least one of a code division multiplexing (CDM) random access slot and at least one time division multiplexing (TDM)/frequency division multiplexing (FDM) random access slot.

35. A wireless transmit/receive unit (WTRU) for random access in a wireless communication system, the WTRU comprising:

a random access channel (RACH) burst generator for generating a RACH burst, the RACH burst comprising a preamble part, a message part, a first cyclic prefix (CP) attached to the preamble part and a second CP attached to the message part, the preamble part comprising M repetition of a basic preamble and a guard time and carrying an implicit message; and

a transmitter for sending the RACH burst in synchronization with a Node-B.

36. The WTRU of claim 35 wherein the message part occupies subcarriers in one of a distributed mode and a localized mode.

37. The WTRU of claim 35 wherein the preamble part occupies a bandwidth wider than a defined random access region such that the Node-B obtains a channel quality indicator (CQI) of more resource blocks.