Fast acquisition of traffic channels for a highly variable data rate reverse link of a CDMA wireless communication system

• US 6,452,913 B1
• Filed: 02/29/2000
• Issued: 09/17/2002
• Est. Priority Date: 12/17/1997
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Tantivy Communications Incorporated (InterDigital, Inc.)
• Inventors: Proctor, James A. Jr.
• Primary Examiner(s): NGO, RICKY QUOC
• Application Number:
  US09/515,487
• Time in Patent Office: 931 Days
• Field of Search: 370/329, 370/335, 370/336, 370/342, 370/345, 370/347, 370/349, 370/350, 370/442, 370/448, 370/437
• US Class Current: 370/335
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/70754 Setting of search window, i.e. range of code offsets to be searched H04B1/70758 takes precedence
• CPC Class Codes: H04B 2001/70706 using a code tracking loop, e.g. a delay locked loop
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04B 2201/70709 with discontinuous detection
• CPC Class Codes: H04B 2201/70715 with application-specific features
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/165 Variable formats
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 25/14 Channel dividing arrangements , i.e. in which a single bit stream is divided between several baseband channels and reassembled at the receiver
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 7/06 the synchronisation signals differing from the information signals in amplitude, polarity or frequency or length
• CPC Class Codes: H04Q 11/0428 Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
• CPC Class Codes: H04Q 2213/13098 Mobile subscriber
• CPC Class Codes: H04Q 2213/13202 Network termination [NT]
• CPC Class Codes: H04Q 2213/13204 : Protocols
• CPC Class Codes: H04Q 2213/13209 : ISDN
• CPC Class Codes: H04Q 2213/13216 : Code signals, frame structure
• CPC Class Codes: H04Q 2213/1327 : Release and resetting of connection
• CPC Class Codes: H04Q 2213/13298 : Local loop systems, access network
• CPC Class Codes: H04Q 2213/13332 : Broadband, CATV, dynamic bandwidth allocation
• CPC Class Codes: H04Q 2213/1336 : Synchronisation
• CPC Class Codes: H04Q 2213/13389 : LAN, internet
• CPC Class Codes: H04W 24/00 : Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/20 : Negotiating bandwidth
• CPC Class Codes: H04W 28/22 : Negotiating communication rate
• CPC Class Codes: H04W 56/00 : Synchronisation arrangements
• CPC Class Codes: H04W 56/0045 : compensating for timing error by altering transmission time
• CPC Class Codes: H04W 56/0075 : based on arrival time vs. expected arrival time
• CPC Class Codes: H04W 72/044 : based on the type of the allocated resource
• CPC Class Codes: H04W 72/0446 : Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/0453 : Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 72/0466 : the resource being a scrambling code
• CPC Class Codes: H04W 72/21 : in the uplink direction of a wireless link, i.e. towards the network
• CPC Class Codes: H04W 74/00 : Wireless channel access
• CPC Class Codes: H04W 74/04 : Scheduled access hybrid access H04W74/02
• CPC Class Codes: H04W 76/28 : Discontinuous transmission [DTX]; Discontinuous reception [DRX]
• CPC Class Codes: H04W 84/14 : WLL [Wireless Local Loop]; RLL [Radio Local Loop]

Abstract

A service option overlay for a CDMA wireless communication in which multiple allocatable subchannels are defined on a reverse link by assigning different code phases of a given long pseudonoise (PN) code to each subchannel. The instantaneous bandwidth needs of each on-line subscriber unit are then met by dynamically allocating none, one, or multiple subchannels on an as needed basis for each network layer connection. The system efficiently provides a relatively large number of virtual physical connections between the subscriber units and the base stations on the reverse link for extended idle periods such as when computers connected to the subscriber units are powered on, but not presently actively sending or receiving data. These maintenance subchannels permit the base station and the subscriber units to remain in phase and time synchronism. This in turn allows fast acquisition of additional subchannels as needed by allocating new code phase subchannels. Preferably, the code phases of the new channels are assigned according to a predetermined code phase relationship with respect to the code phase of the corresponding maintenance subchannel.

Claims

1. A method for communication of data between a base station and multiple subscriber units over one or more CDMA communication channels, the method comprising:

providing a plurality of subchannels within each of at least one CDMA channel;

assigning subchannels for communication between the base station and subscriber units on an as-needed basis; and

maintaining a synchronizing idle mode connection between at least one subscriber unit and the base station, wherein the step of maintaining an idle mode connection further comprises;

analyzing a signal received form a subscriber unit at the base station and detecting whether a corresponding message from a subscriber unit is early or late; and

in response thereto, transmitting a timing alignment correction message on a predetermined channel to the corresponding subscriber unit in the idle mode to achieve synchronization with the base station.

2. A method for communication of data as described in claim 1 wherein the at least one CDMA channel is defined by long pseudo-random noise (PN) codes.

3. A method for communication of data as described in claim 1 wherein an idle mode connection is maintained if no subchannels are assigned for data transfers between a particular subscriber unit and the base station.

4. A method for communication of data as described in claim 1 wherein a data rate of a subchannel is less than a nominal communication data rate between the base station and a subscriber unit.

5. A method for communication of data as described in claim 1 wherein subchannels are defined by orthogonal codes on a single radio frequency carrier.

6. A method for communication of data as described in claim 1 wherein subchannels are defined by code phases.

7. A method for communication of data as described in claim 1 wherein the idle mode connection is maintained using a heartbeat signal.

8. A method of data as described in claim 7 wherein the data rate of the heartbeat signal is from about 37 to 80 bps.

9. A method for communication of data as described in claim 1 wherein the predetermined channel is divided into time slots, and a subscriber unit is assigned at least one of the time slots for receiving timing adjustment messages.

10. A method for communication of data as described in claim 9 further including the step of:

determining a minimum possible time slot duration based upon a detected signal to noise ratio on a corresponding CDMA channel; and

defining a time slot duration in the predetermined channel based upon the determined minimum possible time slot duration.

11. A method for communication of data as described in claim 1 further comprising the step of:

detecting a need for a higher data rate on a link between the base station and a subscriber unit and assigning additional subchannels to provides support for the higher data rate.

12. A method for communication of data as described in claim 11 wherein the additional subchannels are related to an originally assigned code phase.

13. A method for managing data transmissions between a base station and a plurality of field units in a wireless CDMA communication system comprising:

reserving at least one channel having an estimated bandwidth for wireless communications, the at least one channel being defined by pseudo-random noise codes;

dividing the at least one channel to include multiple data channels, each data channel having a bandwidth that is less than the estimated bandwidth, the data channels being defined by phases of corresponding pseudo-random noise codes;

assigning the data channels among selected field units for data transmissions between the field units and the base station; and

maintaining synchronization between the base station and field units not assigned data channels, wherein multiple data channels are assigned for data transfers between the base station and a particular field unit, wherein the assigned data channels are derived from a common channel.

14. A method for managing data transmissions as described in claim 13 wherein the at least one channel is defined by a pseudo-random noise code.

15. A method for managing data transmissions as described in claim 13 wherein the at least one channel is defined by a long pseudo-random noise code.

16. A method for managing data transmissions as described in claim 13 wherein the data channels are defined by short pseudo-random noise (PN) codes.

17. A method for managing data transmissions as described in claim 13 wherein the at least one channel is defined by a short pseudo-random noise code.

18. A method for managing data transmissions as described in claim 13 wherein the data channels are defined by orthogonal pseudo-random noise codes.

19. A method for managing data transmissions as described in claim 13 wherein the at least one channel is divided to include at least one maintenance channel for synchronizing field units not assigned data channels.

20. A method for managing data transmissions as described in claim 13 wherein the at least one maintenance channel includes a heartbeat channel.

21. A method for managing data transmissions between a base station and a plurality of field units in a wireless CDMA communication system comprising:

reserving at least one channel having an estimated bandwidth for wireless communications, the at least one channel being defined by pseudo-random noise codes;

dividing the at least one channel to include multiple data channels, each data channel having a bandwidth that is less than the estimated bandwidth, the data channels being defined by phases of corresponding pseudo-random noise codes;

assigning the data channels among selected field units for data transmissions between the field units and base station;

maintaining synchronization between the base station and field units not assigned data channels;

detecting a need to transmit at a higher data transfer rate between the base station and a particular field unit; and

assigning additional data channels for transmitting data at the higher data rate, wherein the additional channels are related to previously assigned channels based on a common channel.

22. A method for managing data transmissions as described in claim 21 wherein the additional channels are data channels having different code phases of the at least one channel.

23. A method of supporting variable rate data transfers on communication links between a base station and each of a plurality of field units in a wireless CDMA communication system, the method comprising:

estimating a maximum bandwidth of at least one channel based on an acceptable bit error rate, wherein an available bandwidth is determined;

dividing the available bandwidth for data transfers on the communication links, wherein a greater portion of available bandwidth is assigned to links requiring higher data transfer rates; and

allocating a portion of the available bandwidth for maintaining synchronizing links between the base station and subscriber units not actively transmitting data, wherein the step of allocating a portion of the available bandwidth for maintaining synchronous communication links further comprises;

providing a channel divided into time slots, wherein a time slot is assigned to a communication link not actively supporting data transmissions.

24. A method of supporting variable rate data transfers as described in claim 23, wherein the available bandwidth is divided into a plurality of channels, each channel capable of supporting data transfers at a predefined data rate.

25. A method of supporting variable rate data transfers as described in claim 23 further comprising the steps of:

detecting a need for a higher data transfer rate on a communication link; and

in response, allocating a larger portion of the available bandwidth for a data transfer between the base station and corresponding subscriber unit.

26. A method of supporting variable rate data transfers as described in claim 23 further including the steps of:

estimating a minimum possible time slot duration based on a detected signal to noise ratio of the at least one channel; and

defining a time slot duration greater than the minimum possible time slot duration.

27. A method of supporting variable rate data transfers as described in claim 26, wherein each of the plurality of channels is capable of supporting an approximately equal data rate.

28. A method of supporting variable rate data transfers as described in claim 26, wherein a portion of the available bandwidth is allocated to support a heartbeat channel.

29. A method of supporting variable rate data transfers as described in claim 26 wherein the channels are defined by pseudo-random noise codes.

30. A method of supporting variable rate data transfers as described in claims 26 wherein the channels are defined by orthogonal codes.

31. A method of supporting variable rate data transfers as described in claim 23 wherein the channels are defined by code phases.

32. A method of supporting variable rate data transfers as described in claim 31 wherein multiple channels assigned to a communication link have common code phases.