Handoff with closed-loop power control

• US 6,324,207 B1
• Filed: 03/22/1999
• Issued: 11/27/2001
• Est. Priority Date: 04/29/1996
• Status: Expired due to Term

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Golden Bridge Technology Incorporated
• Inventors: Yuen, Elmer, Parsa, Kourosh, Kanterakis, Emmanuel
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US09/273,507
• Time in Patent Office: 981 Days
• Field of Search: 375/130, 375/133, 375/138, 375/141, 375/145, 375/225, 370/318, 370/331, 370/332, 370/333, 370/412, 455/436, 455/437, 455/439, 455/522, 455/524, 714/748
• US Class Current: 375/141
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 36/023 Buffering or recovering information during reselection
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 36/302 due to low signal strength
• CPC Class Codes: H04W 52/04 TPC

Abstract

In a cellular spread-spectrum communications network, a system and method for handing off a remote station from a source-base station to a target-base station without loss of data. The remote station receives a first spread-spectrum signal having a first signal quality from the source-base station and transmits data to the source-base station at a first data rate and a first power level. Responsive to monitoring the first signal quality and comparing the first signal quality to a plurality of signal qualities of a respective plurality of received-spread-spectrum signals, the remote station initiates handoff when any of a number of predetermined criteria are met. Upon initiating handoff to the target-base station, the remote station stores the data that would otherwise have been transmitted. Once handoff is complete, the remote station transmits the stored data to the target-base station at a second data rate and a second power level, with the second data rate greater than the first data rate and the second power level greater than the first power level. Once the stored data has been transmitted, the remote station transmits data to the target-base station at a data rate and power level comparable to the first data rate and the first power level.

Claims

1. In a spread-spectrum-communications system having a plurality of base stations and a remote station (RS), with the remote station communicating with a source-base station (BS) using spread-spectrum modulation, with the remote station transmitting data to the source-base station at a first BS data rate and a first BS power level, a method comprising the steps of:

monitoring, at the remote station, a first signal quality of a first received-spread-spectrum signal;

scanning, at said remote station, a plurality of received-spread-spectrum signals radiated from the plurality of base stations, respectively;

storing, at said remote station, a plurality of signal qualities for the plurality of received-spread-spectrum signals, respectively;

selecting, from the plurality of received-spread-spectrum signals, at said remote station, using the plurality of signal qualities from the plurality of received-spread-spectrum signals, a second received-spread-spectrum signal having a second signal quality transmitted from a target-base station;

initiating, from said remote station, upon the first signal quality falling below any of a predetermined handoff threshold, a handoff process;

transmitting, from said remote station, an RS-access-burst signal having a plurality of RS segments, with each RS segment having a plurality of RS symbols carrying differentially encoded BS power-control information, with the plurality of RS segments having a plurality of RS power levels, increasing in time, respectively;

queuing, upon requesting the handoff process to the target-base station, RS data for transmission from said remote station;

receiving, at said target-base station, the RS-access-burst signal at an RS detected-power level;

transmitting from said target-base station a BS-access-burst signal having a plurality of BS segments, with each BS segment having a plurality of BS symbols carrying differentially encoded RS power-control information, with the plurality of BS segments having a plurality of BS power levels, increasing in time, respectively;

differentially encoding, responsive to detecting the BS-access-burst signal, the plurality of RS symbols with BS-power control information including power level for said target-base station;

differentially encoding, responsive to detecting the RS-access-burst signal, the plurality of BS symbols with RS-power control information including power level for said remote station;

receiving at said remote station, the BS-access-burst signal from said target-base station;

receiving at said target-base station, the RS-access-burst signal from said remote station;

transmitting, from said remote station to said target-base station, the queued RS data at a second RS data rate, with the second RS data rate greater than a first RS data rate, thereby transferring the queued RS data to said target-base station;

transmitting, from said target-base station to said remote station, the queued BS data at a second BS data rate, with the second BS data rate greater than the first BS data rate, thereby transferring the queued BS data to said remote station;

transmitting, from said remote station to said target-base station, responsive to the queued RS data being transferred to the target-base station, at the first RS data rate; and

transmitting, from said target-base station to said remote station, responsive to the queued BS data being transferred to said remote station, at the first BS data rate.