System and method for maintaining timing of synchronization messages over a reverse link of a CDMA wireless communication system

• US 7,936,728 B2
• Filed: 11/29/2001
• Issued: 05/03/2011
• Est. Priority Date: 12/17/1997
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Tantivy Communications Incorporated (InterDigital, Inc.)
• Inventors: Proctor, James A. Jr.
• Primary Examiner(s): Mattis; Jason E
• Application Number:
  US09/997,732
• Publication Number:
  US 20020080742A1
• Time in Patent Office: 3,442 Days
• Field of Search: 370/502, 370/329, 370/335, 370/350
• US Class Current: 370/335
• CPC Class Codes: H04B 7/2668 Arrangements for Wireless Code-Division Multiple Access [CDMA] System Synchronisation, for code acquisition H04B1/7075, for code tracking H04B1/7085
• 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: 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 56/00 Synchronisation arrangements
• 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, time and power synchronism while maintaining optimal timing control over synchronization messages. This in turn allows fast acquisition of additional reverse link capacity as needed by allocating additional orthogonal codes within the same code phase and by varying the spreading factor of the codes, as well as by adding additional code phases.

Claims

1. A code division multiple access (CDMA) subscriber unit comprising:

a wireless transceiver configured to transmit a digital signal over a CDMA reverse channel, and the wireless transceiver further configured to receive a digital signal over a CDMA forward channel, the CDMA forward channel having a plurality of subchannels with an assigned orthogonal code to each of the plurality of subchannels;

a bandwidth manager configured to receive a time slot assignment over the CDMA forward channel, wherein the time slot assignment is used for uplink transmissions during an idle mode only;

the wireless transceiver configured to transmit an idle mode signal over the CDMA reverse channel, the idle mode signal based on the time slot assignment on a condition that the wireless transceiver is powered on but not actively transmitting data, to maintain timing alignment; and

the wireless transceiver is further configured to alternate between sending bits and not sending bits in time slots while in the idle mode.

2. The CDMA subscriber unit of claim 1 wherein the bandwidth manager is further configured to receive an updated time slot assignment over the CDMA forward channel for transmission of a subsequent idle mode signal.

3. The CDMA subscriber unit of claim 1 wherein each of the time slots is 1.25 ms.

4. The CDMA subscriber unit of claim 1 wherein the transceiver is further configured to request allocation of additional available orthogonal subchannels.

5. A code division multiple access (CDMA) subscriber unit comprising:

a wireless transceiver configured to transmit a digital signal over a CDMA reverse channel, and the wireless transceiver further configured to receive a digital signal over a CDMA forward channel, the CDMA forward channel having a plurality of subchannels with an assigned orthogonal code to each of the plurality of subchannels;

wherein the digital signals include an idle mode signal;

a bandwidth manager configured to

allocate subchannels on an as needed basis on a condition that the wireless transceiver is actively transmitting data, and

receive a time slot assignment over the CDMA forward channel, wherein the time slot assignment is used for uplink transmissions during an idle mode only;

the wireless transceiver is further configured to transmit the idle mode signal over the CDMA reverse channel based on the time slot assignment on a condition that the wireless transceiver is powered on but not actively transmitting data, to maintain timing alignment; and

the wireless transceiver is further configured to alternate between sending bits and not sending bits in time slots while in the idle mode.

6. The CDMA subscriber unit of claim 5 wherein the bandwidth manager is further configured to receive an updated time slot assignment over the CDMA forward channel for transmission of a subsequent idle mode signal.

7. The CDMA subscriber unit of claim 5 wherein each of the time slots is 1.25 ms.

8. The CDMA subscriber unit of claim 5 wherein the transceiver is further configured to request allocation of additional available orthogonal subchannels.