PREAMBLE SEQUENCING FOR RANDOM ACCESS CHANNEL IN A COMMUNICATION SYSTEM

Abstract

A system and method for initializing a system communication without previous reservations for random access channel (RACH) access includes a first step of defining at least one spread sequence derived from at least one constant amplitude zero autocorrelation sequence. A next step includes combining the spread sequence with a Walsh code to form an extended spread sequence. A next step includes using the extended spread sequence in a preamble for a RACH. A next step includes sending the preamble to a BTS for acquisition. A next step includes monitoring for a positive acquisition indicator from the BTS. A next step includes scheduling the sending of a RACH message. A next step includes sending the RACH message.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by making reference to the following description, taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify identical elements, wherein:

FIG. 1 illustrates a TDM/FDM RACH structure;

FIG. 2 is a table of RACH parameters for the structure of FIG. 1;

FIG. 3 is a graphical representation of a circular auto/cross correlation of a Chu-sequence with M=15, in accordance with the present invention;

FIG. 4 is a graphical representation of a correlation sequence in the presence of two RACH requests with delays of 0 and 2, in accordance with the present invention;

FIG. 5 is a graphical representation of a detection error rate and false alarm performance of TDM-RACH over an AWGN channel, in accordance with the present invention;

FIG. 6 is a graphical representation of a detection error rate and false alarm performance of TDM-RACH over an TU channel at 3 kilometers/hour, in accordance with the present invention;

FIG. 7 is a graph of an example of a RACH preamble, in accordance with the present invention;

FIG. 8 is a block diagram of RACH preamble generation using time-domain modulation, in accordance with the present invention;

FIG. 9 is a block diagram of RACH preamble generation using frequency-domain modulation, in accordance with the present invention;

FIG. 10 is a graphical representation of a circular auto/cross correlation of a Chu-sequence with M=300, in accordance with the present invention;

FIG. 11 is a graphical representation of RACH detection error and false alarm performance over an AWGN channel, in accordance with the present invention;

FIG. 12 is a graphical representation of RACH detection error and false alarm performance over an TU channel at 3 kilometers/hour, in accordance with the present invention;

FIG. 13 is a table showing a comparison of the TDM/FDM and hybrid/CDM embodiments of the present invention; and

FIG. 14 comprises a flow diagram of a method, in accordance with the present invention; and

FIG. 15 illustrates a block diagram of a communication system, in accordance with the present invention.

Claims

1. A method for initializing a communication in a communication system without previous reservations for initial access preamble, the method comprising the steps of: defining at least one spread sequence derived from at least one constant amplitude zero autocorrelation sequence;combining the spread sequence with an orthogonal code to form an extended spread sequence;using the extended spread sequence in a preamble for a RACH;transmitting the preamble to a BTS for acquisition;monitoring for a positive acquisition indicator from the BTS;signaling BTS for RACH message transmission; andsending the RACH message.

2. The method of claim 1, wherein the communication system is frequency domain based, and the transmitting step includes transmitting the preamble to a BTS for acquisition in parallel with the bearer data.

3. The method of claim 1, wherein the communication system is one of the group frequency domain based communication systems including; OFDMA, DFT-SOFDM, and IFDMA based multiple access systems.

4. The method of claim 1, wherein the defining step includes a plurality of frequency-spread sequences derived from a plurality of constant amplitude zero autocorrelation sequences, wherein the combining step results in a plurality of extended frequency-spread signature sequences, and further comprising the step of selecting a signature sequence from the plurality of frequency-spread signature sequences.

5. The method of claim 1, wherein the defining step includes a plurality of frequency-spread sequences derived from a plurality of constant amplitude zero autocorrelation sequences, the combining step formulates a plurality of unique extended frequency-spread signature sequences, and further comprising the step of allocating of signature sequences for use by sector.

6. The method of claim 5, wherein the unique signature sequences are derived using a different prime number to formulate each signature sequence.

7. The method of claim 5, wherein the unique signature sequences derived with different prime numbers are used for different sectors/cells, and/or different user equipments.

8. The method of claim 1, wherein the defining step uses a general chirp-like (GCL) sequence for the at least one constant amplitude zero autocorrelation sequence.

9. The method of claim 1, wherein the defining step uses Chu-sequence for the at least one constant amplitude zero autocorrelation sequence.

10. The method of claim 1, wherein the defining step uses delayed constant amplitude zero autocorrelation sequences.

11. The method of claim 1, wherein the sending step includes the BTS detecting the signature spread sequence of the RACH preamble, and the monitoring step includes receiving an acknowledgement with a preamble sequence number.

12. The method of claim 11, wherein the detection is performed using one of the group of a frequency-domain correlator and/or a time-domain correlator.

13. The method of claim 1, further comprising the setting a minimum transmitter power before the sending step, wherein if the monitoring step does not receive a positive acquisition indicator from the BTS, further comprising the substep of increasing the transmitter power with a new access slot and/or a new signature sequence until a positive acquisition indicator is received from the BTS.

14. The method of claim 1, further comprising the randomly signature selection step, wherein if the monitoring step does not receive a positive acquisition indicator from the BTS, further comprising the substep of randomly selecting a new signature sequence until a positive acquisition indicator is received from the BTS.

15. The method of claim 1, wherein the monitoring step includes monitoring a downlink control channel for a fixed amount of time to obtain acknowledge information for the RACH request.

16. The method of claim 1, wherein the sending step includes sending the RACH message in a next time slot of a pre-defined time-frequency region.

17. The method of claim 1, wherein the sending step includes sending the RACH message which is scheduled by the BTS.

18. The method of claim 1, wherein the sending step includes sending the RACH message at the reserved RACH message channel, when an acknowledge information of using this channel is received from BTS.

19. The method of claim 1, wherein the communication system is an EUTRA communication system.

20. A system for initializing a communication between a BTS and user equipment in a communication system without previous reservations for random access channel (RACH) access, the system comprising: a user equipment including a receiver, transmitter, and a processor, the user equipment processor defines at least one spread sequence derived from at least one constant amplitude zero autocorrelation sequence, combines the spread sequence with an orthogonal code to form an extended spread sequence, and uses using the extended spread sequence in a RACH preamble transmitted to a BTS; anda BTS including a receiver, transmitter, and a processor, the BTS acquires the RACH preamble, sends a positive acquisition indicator to the user equipment, schedules the sending of a RACH message, and receives the RACH message.

21. The system of claim 20 wherein the user equipment processor defines a plurality of frequency-spread sequences derived from a plurality of constant amplitude zero autocorrelation sequences resulting in a plurality of extended frequency-spread signature sequences, and wherein the user equipment processor selects a signature sequence from the plurality of frequency-spread signature sequences.

22. The system of claim 20, wherein the user equipment processor defines a plurality of frequency-spread sequences derived from a plurality of constant amplitude zero autocorrelation sequences resulting in a plurality of unique extended frequency-spread signature sequences, and wherein the BTS processor allocates the use of signature sequences by sector.

23. The system of claim 20, wherein the unique signature sequences are derived using a different prime number to formulate each signature sequence.

24. The system of claim 20, wherein the user equipment processor uses a general chirp-like (GCL) sequence for the at least one constant amplitude zero autocorrelation sequence.

25. The system of claim 20, wherein the user equipment processor uses Chu-sequence for the at least one constant amplitude zero autocorrelation sequence.

26. The system of claim 20, wherein the user equipment processor uses delayed constant amplitude zero autocorrelation sequences.

27. The system of claim 20, wherein the BTS detects the signature spread sequence of the RACH preamble, and the user equipment receiving an acknowledgement with a preamble sequence number.

28. The system of claim 27, wherein the BTS detects the spread sequence using one of the group of a frequency-domain correlator and/or a time-domain correlator.

29. The system of claim 20, wherein the user equipment transmitter sets a minimum transmitter power before the sending the preamble, wherein if the user equipment receiver does not receive a positive acquisition indicator from the BTS the user equipment processor increases the transmitter power with a new access slot and a new signature sequence until a positive acquisition indicator is received from the BTS.

30. The system of claim 20, further comprising the randomly signature selection step, wherein if the monitoring step does not receive a positive acquisition indicator from the BTS, further comprising the substep of randomly selecting a new signature sequence until a positive acquisition indicator is received from the BTS.

31. The system of claim 20, wherein the user equipment monitors a downlink control channel for a fixed amount of time to obtain scheduling information for the RACH message.

32. The system of claim 20, wherein the user equipment sends the RACH message in a next time slot of a pre-defined time-frequency region.

33. The system of claim 20, wherein the sending step includes sending the RACH message at a BTS scheduled channel.

34. The system of claim 20, wherein the sending step includes sending the RACH message at the reserved RACH message channel, when an acknowledge information of using this channel is received from BTS.

35. The system of claim 20, wherein the communication system is an EUTRA communication system.

36. A method for initializing a communication in an EUTRA communication system without previous reservations for random access channel (RACH) access, the method comprising the steps of: defining a plurality of frequency-spread sequences derived from a plurality of constant amplitude zero autocorrelation sequences;combining the spread sequences with a Walsh code to form a plurality of extended spread sequences;selecting one of the extended spread sequences for use in a preamble for a RACH;transmitting the preamble to a BTS for acquisition;detecting the preamble using a frequency-domain correlator;monitoring for a positive acquisition indicator from the BTS;scheduling the sending of a RACH message;signaling BTS for RACH message transmission; andsending the RACH message as scheduled.