Remote wireless unit having reduced power operating mode for a discrete multitone spread spectrum communications system

• US 6,347,236 B1
• Filed: 02/24/1997
• Issued: 02/12/2002
• Est. Priority Date: 02/06/1997
• Status: Expired due to Term

• Current Assignee: Clearwire Ip Holdings LLC (Deutsche Telekom AG)
• Original Assignee: AT&T Wireless Services Incorporated (AT&T, Inc.)
• Inventors: Gibbons, David, Golden, James Timothy
• Primary Examiner(s): TO, DORIS HA
• Application Number:
  US08/803,835
• Time in Patent Office: 1,814 Days
• Field of Search: 455/422, 455/423-425, 455/38.3, 455/343, 455/522, 455/572, 455/574
• US Class Current: 455/574
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 12/10 Current supply arrangements
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 5/026 using code division
• CPC Class Codes: H04W 52/0296 switching to a backup power supply
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A remote unit for a personal wireless area network includes a receiver, an AC power supply, a battery-backup power supply and a controller. The battery-backup becomes operative when the AC power supply fails and supplied power to the receiver. The controller detects when the AC power supply fails and controls the receiver and the battery-backup power supply by invoking a sleep mode of operation. The sleep mode of operation is periodically interrupted by the controller controlling the receiver and the battery-backup power supply to enter a standby mode of operation in which the receiver scans for a CONNECT message from a base station indicating an incoming call. The controller coordinates the sleep mode and the standby mode of operations based on a frame count that is generated from an identification number of the remote unit. A highly bandwidth-efficient communications method is employed in the base station to enable it to coordinate communication with the remote unit when it changes from the sleep mode to the standby mode.

Claims

1. In a wireless communications network, a method in a base station to communicate with a remote unit that is in a sleep mode, the remote unit having a unique identification value, comprising the steps of:

establishing a periodic reference instant at the base station and at the remote station;

determining a delay interval following said periodic reference instant at the base station, said delay interval being derived from said unique identification value of said remote unit; and

transmitting a message from the base station to the remote unit at a second instant following said delay interval, said remote unit having changed from said sleep mode to a standby mode after said delay interval;

wherein said periodic reference instant is established by a beginning subframe count instant that is incremented by a packet count value at the base station and at the remote unit.

2. The method of claim 1, wherein said delay interval is determined by a value N of a quantity of M least significant bits of said unique identification value of said remote unit, the delay interval being an interval required for the occurrence of a plurality of N of said beginning subframe count instants.

3. The method of claim 2, wherein said remote unit changes from said sleep mode to a standby mode after said delay interval.

4. In a wireless communications network, a method in a base station to communicate with a remote unit that is in a sleep mode, the remote unit having a unique identification value, comprising the steps of:

establishing a periodic reference instant at the base station and at the remote unit;

determining a delay interval following said periodic reference instant at the base station, said delay interval being derived from said unique identification value of said remote unit;

attempting to initiate a communication from said base station to said remote unit;

concluding at the base station that the remote unit is in said sleep mode if said attempting step fails to initiate communications with the remote unit;

waiting for said delay interval following said periodic reference instant at the base station; and

transmitting a message from the base station to the remote unit at a second instant following said delay interval, said remote unit having changed from said sleep mode to a standby mode after said delay interval;

wherein said periodic reference instant is established by a beginning subframe count instant that is incremented by a packet count value at the base station and at the remote unit.

5. The method of claim 4, wherein said delay interval is determined by a value N of a quantity of M least significant bits of said unique identification value of said remote unit, the delay interval being an interval required for the occurrence of a plurality of N of said beginning subframe count instants.

6. The method of claim 5, wherein said remote unit changes from said sleep mode to a standby mode after said delay interval.

7. A highly bandwidth-efficient communications method in a base station to communicate with a remote unit that is in a sleep mode, the remote unit having a unique identification value, comprising the steps of:

establishing a periodic reference instant at the base station and at the remote unit;

determining a delay interval following said periodic reference instant at the base station, said delay interval being derived from said unique identification value of said remote unit;

receiving at a base station a spread signal comprising an incoming data traffic signal spread over a plurality of discrete traffic frequencies;

adaptively despreading the signals received at the base station by using despreading weights;

attempting to initiate a communication from said base station to said remote unit;

concluding at the base station that the remote unit is in said sleep mode if said attempting step fails to initiate communications with the remote unit;

waiting for said delay interval following said periodic reference instant at the base station; and

transmitting at the base station to the remote unit a spread signal comprising an outgoing data traffic signal spread over a plurality of discrete traffic frequencies;

wherein said periodic reference instant is established by a beginning subframe count instant that is incremented by a packet count value at the base station and at the remote unit.

8. The method of claim 7, wherein said delay interval is determined by a value N of a quantity of M least significant bits of said unique identification value of said remote unit, the delay interval being an interval required for the occurrence of a plurality of N of said beginning subframe count instants.

9. The method of claim 8, wherein said remote unit changes from said sleep mode to