Random access for wireless multiple-access communication systems

• US 20040156328A1
• Filed: 10/23/2003
• Published: 08/12/2004
• Est. Priority Date: 10/25/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Howard, Steven J., Ketchum, John W., Walton, J. Rodney, Wallace, Mark S.
• Granted Patent: US 8,169,944 B2
• Time in Patent Office: Days
• US Class Current: 370/313
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/043 using best eigenmode, e.g. beam forming or beam steering
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• 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 1/0017 where the mode-switching is based on Quality of Service requirement
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals
• CPC Class Codes: H04L 2001/0093 Point-to-multipoint
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 25/0242 using matrix methods
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2601 : Multicarrier modulation systems
• CPC Class Codes: H04L 27/2602 : Signal structure
• CPC Class Codes: H04L 27/261 : Details of reference signals
• CPC Class Codes: H04L 27/2647 : Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04W 28/20 : Negotiating bandwidth
• CPC Class Codes: H04W 52/50 : at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 74/002 : Transmission of channel access control information
• CPC Class Codes: H04W 74/08 : Non-scheduled access, e.g. ALOHA hybrid access H04W74/02
• CPC Class Codes: H04W 74/0833 : Random access procedures, e.g. with 4-step access
• CPC Class Codes: H04W 74/0866 : using a dedicated channel for access
• CPC Class Codes: H04W 88/06 : adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

Techniques for facilitating random access in wireless multiple-access communication systems. A random access channel (RACH) is defined to comprise a “fast” RACH (F-RACH) and a “slow” RACH (S-RACH). The F-RACH and S-RACH can efficiently support user terminals in different operating states and employ different designs. The F-RACH can be used to quickly access the system, and the S-RACH is more robust and can support user terminals in various operating states and conditions. The F-RACH may be used by user terminals that have registered with the system and can compensate for their round trip delays (RTDs) by properly advancing their transmit timing. The S-RACH may be used by user terminals that may or may not have registered with the system, and may or may not be able to compensate for their RTDs. The user terminals may use the F-RACH or S-RACH, or both, to gain access to the system.

Claims

1. A method of accessing a wireless multiple-access communication system, comprising:

determining a current operating state of a terminal;

selecting one random access channel from among at least two random access channels based on the current operating state; and

transmitting a message on the selected random access channel to access the system.

2. The method of claim 1, wherein the at least two random access channels include a first random access channel used by registered terminals for system access and a second random access channel used by registered and unregistered terminals for system access.

3. The method of claim 2, wherein transmissions on the first random access channel are compensated for propagation delay.

4. The method of claim 1, wherein the current operating state is indicative of whether or not the terminal has registered with the system.

5. The method of claim 1, wherein the current operating state is indicative of whether or not the terminal can compensate for propagation delay to an access point receiving the message.

6. The method of claim 1, wherein the current operating state is indicative of whether or not a particular received signal-to-noise ratio (SNR) is achieved for the terminal.

7. The method of claim 1, further comprising:

retransmitting the message until an acknowledgment is received for the message or a maximum number of access attempts has been exceeded.

8. The method of claim 1, further comprising:

if access is not gained via the selected random access channel, transmitting another message on another random access channel selected from among the at least two random access channels.

9. The method of claim 1, wherein the transmitting includes

selecting a slot from among a plurality of slots available for the selected random access channel, and

transmitting the message in the selected slot.

10. The method of claim 1, wherein the message includes an identifier for the terminal.

11. The method of claim 10, wherein the identifier is unique to the terminal.

12. The method of claim 10, wherein the identifier is a common identifier used by unregistered terminals.

13. The method of claim 1, wherein the multiple-access communication system supports terminals with single antenna and terminals with multiple antennas.

14. The method of claim 1, wherein the multiple-access communication system uses orthogonal frequency division multiplexing (OFDM).

15. A method of accessing a wireless multiple-access multiple-input multiple-output (MIMO) communication system, comprising:

determining whether a terminal is registered or unregistered with the system;

if the terminal is registered, transmitting a first message on a first random access channel to access the system; and

if the terminal is unregistered, transmitting a second message on a second random access channel to access the system.

16. The method of claim 15, wherein the first message is transmitted in a manner to account for propagation delay to an access point receiving the first message.

17. A method of facilitating random access in a wireless multiple-access communication system, comprising:

processing a first random access channel used by registered terminals to access the system; and

processing a second random access channel used by registered and unregistered terminals to access the system.

18. The method of claim 17, wherein the processing for each of the first and second random access channels includes detecting for presence of transmissions on the random access channel.

19. The method of claim 18, wherein the detecting is based on a pilot that is included in each transmission on the first and second random access channels.

20. The method of claim 18, further comprising:

determining round trip delay for a terminal whose transmission is detected in the second random access channel.

21. The method of claim 17, wherein transmissions on the first random access channel are compensated for propagation delay, and wherein the processing the first random access channel includes

detecting for presence of a transmission in each of a plurality of slots available for the first random access channel.

22. The method of claim 21, wherein the detecting is based on a decision directed detector.

23. The method of claim 17, wherein the processing the second random access channel includes

detecting for presence of transmissions on the second random access channel by performing sliding correlation.

24. A random access channel for a wireless multiple-access multiple-input multiple-output (MIMO) communication system, comprising:

a first random access channel for use by registered terminals to access the system; and

a second random access channel for use by registered and unregistered terminals to access the system.

25. The random access channel of claim 24, wherein transmissions on the first random access channel are compensated for propagation delay.

26. The random access channel of claim 24, wherein the first and second random access channels are associated with first and second segments, respectively, in a frame.

27. The random access channel of claim 26, wherein the first and second segments are configurable for each frame.

28. The random access channel of claim 26, wherein each of the first and second segments is divided into a plurality of slots.

29. The random access channel of claim 28, wherein the duration of each of the plurality of slots for the second segment is defined to be longer than a largest expected round trip delay for terminals in the system.

30. The random access channel of claim 24, wherein the first and second random access channels are associated with first and second protocol data units (PDUs), respectively.

31. The random access channel of claim 30, wherein the first and second PDUs are associated with different lengths.

32. The random access channel of claim 30, wherein the first and second PDUs are associated with first and second reference portions, respectively.

33. The random access channel of claim 30, wherein the first PDU comprises a reference portion and a message portion that are time division multiplexed.

34. The random access channel of claim 30, wherein the second PDU comprises a reference portion and a message portion that are multiplexed on different sets of subbands.

35. The random access channel of claim 30, wherein the first and second PDUs are associated with different sets of data fields.

36. The random access channel of claim 35, wherein each of the first and second PDUs includes an identifier field.

37. The random access channel of claim 35, wherein the second PDU includes a cyclic redundancy check (CRC) field.

38. The random access channel of claim 30, wherein the first and second PDUs are associated with different coding schemes.

39. A terminal in a wireless multiple-access communication system, comprising:

a controller operative to determine a current operating state of the terminal and to select one random access channel from among at least two random access channels for use to access the system based on the current operating state; and

a data processor operative to process a message for transmission on the selected random access channel.

40. An apparatus in a wireless multiple-access communication system, comprising:

means for determining a current operating state of the apparatus;

means for selecting one random access channel from among at least two random access channels based on the current operating state; and

means for transmitting a message on the selected random access channel to access the system.

41. An apparatus in a wireless multiple-access communication system, comprising:

means for processing a first random access channel used by registered terminals to access the system; and

means for processing a second random access channel used by registered and unregistered terminals to access the system.