Mobile radio handover initiation determination

• US 5,491,834 A
• Filed: 08/27/1993
• Issued: 02/13/1996
• Est. Priority Date: 12/27/1990
• Status: Expired due to Term

• Current Assignee: Steelhead Licensing LLC
• Original Assignee: British Telecommunications PLC (BT Group PLC)
• Inventors: Chia, Si Tak S.
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): SOBUTKA, PHILIP
• Application Number:
  US08/081,291
• Time in Patent Office: 900 Days
• Field of Search: 455/33.2, 455/33.3, 455/33.4, 455/54.1, 455/54.2, 455/56.1, 455/33.1, 379/60
• US Class Current: 455/441
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: H04W 36/04 Reselecting a cell layer in multi-layered cells

Abstract

An intelligent mobile radio unit is served by one of a network of macrocells and microcells. The unit is arranged to monitor, for example, the signal strength or bit error ratio of signals transmitted from each of a set of candidate base stations of cells surrounding the serving base based on the assessment of a running average of the rise/fall in signal quality, the unit is arranged to determine from a look-up table of stored templates of conditions for handover whether a handover between base stations and bewtween macro- and microcells is

Claims

1. A handover determination system for a mobile radio network including a plurality of cells, each cell having associated with it a base station for supporting communications with a mobile unit, the system comprising:

means for monitoring a quality of a signal respectively transmitted between each of a plurality of candidate base stations and the mobile unit;

means for producing an indication of the rise or fall in the said quality as a function of time; and

control means for initiating a handover from a serving base station, supporting communications with the mobile unit, to another base station, the initiation being based on the rise/fall as a function of time in the said quality of the signals associated with the plurality of candidate base stations being monitored;

said mobile unit including the means for monitoring and the means for producing, the mobile unit further comprising signalling means for addressing the serving base station with an indication of the need for a handover to be initiated; and

said signalling means being arranged to address the serving base station with an indication of the level of priority of a handover and/or with an indication of the possibility of a handover contingent upon the proceeding results of monitoring the quality of the transmitted signal.

2. A system as in claim 1, in which the monitored signal is transmitted from each mobile unit to the base station.

3. A system as in claim 1, in which the monitored quality of the signal is the received signal power or the bit error ratio.

4. A system as in claim 1, in which the means for producing an indication include a quality decrement/increment estimater which is arranged to determine the rise or fall in the quality from the calculation of the running average of the indications.

5. A system as in claim 1, in which the control means are arranged to instruct the means for monitoring to monitor a set of signals, each signal being distinctive of one of a corresponding set of candidate base stations, the composition of the set of candidate base stations being defined in accordance with the identify of the serving base station.

6. A system as in claim 5, in which each signal in the set of signals distinguishes a respective base station by the frequency of the signal.

7. A handover determination system for a mobile radio network including a plurality of cells, each cell having associated with it a base station for supporting communications with a mobile unit, the system comprising:

means for monitoring a quality of a signal respectively transmitted between each of a plurality of candidate base stations and the mobile unit;

means for producing an indication of the rise or fall in the said quality as a function of time; and

control means for initiating a handover from a serving base station, supporting communications with the mobile unit, to another base station, the initiation being based on the rise/fall as a function of time in the said quality of the signals associated with the plurality of candidate base stations being monitored;

said mobile unit including the means for monitoring and the means for producing, the mobile unit further comprising signalling means for addressing the serving base station with an indication of the need for a handover to be initiated; and

means storing a set of templates of changes in signal quality and/or rates thereof as a function of time, the control means being arranged to initiate a handover based at least partially on the recognition of a substantial match between the incoming signal quality as a function of time and a template.

8. A handover determination method for a mobile radio network including a plurality of cells, each cell having associated with it a base station for supporting communications with a mobile unit, the method comprising:

monitoring a quality of a signal as a function of time respectively transmitted between each of a plurality of candidate base stations and the mobile unit;

producing an indication of the rise or fall as a function of time in the said quality; and

initiating a handover from a serving base station, supporting communication with the mobile unit, to another base station, the initiation being based on the rise/fall as a function of time in the said quality of the signal associated with the plurality of candidate base stations being monitored.

9. A method as in claim 8, in which said monitoring step includes causing the mobile unit to determine the quality of signals received from each of the candidate base stations.

10. A method as in claim 8, in which the monitored quality is the received signal power or the bit error ratio.

11. A method as in claim 8, including monitoring a set of signals, each signal being distinctive of one of a corresponding set of candidate base stations, the composition of the set of candidate base stations being defined in accordance with the identify of the serving base station.

12. A method as in claim 11, in which each signal in the set of signals distinguishes a respective base station by the carrier frequency of the signal.

13. A method as in claim 8, in which the monitoring of the said quality and producing the said indication is conducted by the mobile unit, the method further including addressing the serving base station from the mobile unit with an indication of the need for a handover to be initiated.

14. A handover determination method for a mobile radio network including a plurality of cells, each cell having associated with it a base station for supporting communications with a mobile unit, the method comprising:

monitoring a quality of a signal as a function of time respectively transmitted between each of a plurality of candidate base stations and the mobile unit;

producing an indication of the rise or fall as a function of time in the said quality; and

initiating a handover from a serving base station, supporting communication with the mobile unit, to another base station, the initiation being based on the rise/fall as a function of time in the said quality of the signal associated with the plurality of candidate base stations being monitored;

said monitoring of the said quality and producing the said indication being conducted by the mobile unit, the method further including addressing the serving base station from the mobile unit with an indication of the need for a handover to be initiated; and

wherein said mobile unit addresses the base station with an indication of the level of priority of a handover and/or with an indication of the possibility of a handover contingent upon proceeding results of monitoring the quality of the transmitted signal.

15. A handover determination method for a mobile radio network including a plurality of cells, each cell having associated with it a base station for supporting communications with a mobile unit, the method comprising:

monitoring a quality of a signal as a function of time respectively transmitted between each of a plurality of candidate base stations and the mobile unit;

producing an indication of the rise or fall as a function of time in the said quality; and

initiating a handover from a serving base station, supporting communication with the mobile unit, to another base station, the initiation being based on the rise/fall as a function of time in the said quality of the signal associated with the plurality of candidate base stations being monitored;

said monitoring of the said quality and producing the said indication being conducted by the mobile unit, the method further including addressing the serving base station from the mobile unit with an indication of the need for a handover to be initiated; and

recognising a set of unique template conditions for joining, leaving and/or staying within a microcell based on interpretation of the rise/fall as a function of time in signal quality, the initiation of a handover being at least partially determined on the basis of a substantial match between an incoming signal quality as a function of time and a template.

16. A mobile unit for a mobile radio system, the mobile unit comprising:

means for receiving a plurality of signals each respectively transmitted by one of a set of candidate base stations;

means for monitoring the quality of the signal;

means for producing an indication of the rise or fall in the said quality as a function of time; and

signalling means for transmitting to a serving base station, supporting communication with the mobile unit, a signal indicating the need for a handover to a candidate base station on the basis of the rise/fall as a function of time in the said quality of the signals associated with the plurality of candidate base stations being monitored.

17. A mobile unit as in claim 16, in which the monitoring means are arranged to monitor received signal power or bit error ratio.

18. A mobile unit as in claim 16, in which the means for producing an indication include a quality increment/decrement estimator which is arranged to determine the rise/fall in the quality as a function of time from the calculation of a running average of the indications.

19. A mobile unit for a mobile radio system, the mobile unit comprising:

means for receiving a plurality of signals each respectively transmitted by one of a set of candidate base stations;

means for monitoring the quality of the signal;

means for producing an indication of the rise or fall in the said quality as a function of time; and

signalling means for transmitting to a serving base station,

supporting communication with the mobile unit, a signal indicating the need for a handover to a candidate base station on the basis of the rise/fall as a function of time in the said quality of the signals associated with the plurality of candidate base stations being monitored; and

wherein said signalling means are arranged to address the base station with an indication of the level of priority of a handover and/or with an indication of the level of priority of a handover contingent upon proceeding results of monitoring the quality of the transmitted signal.

20. A mobile unit for a mobile radio system, the mobile unit comprising:

means for receiving a plurality of signals each respectively transmitted by one of a set of candidate base stations;

means for monitoring the quality of the signal;

means for producing an indication of the rise or fall in the said quality as a function of time; and

signalling means for transmitting to a serving base station,

supporting communication with the mobile unit, a signal indicating the need for a handover to a candidate base station on the basis of the rise/fall as a function of time in the said quality of the signals associated with the plurality of candidate base stations being monitored; and

means storing a set of templates of changes in signal quality and/or rates thereof as a function of time, the signalling means being at least partially responsive to a substantial match of a template with an incoming signal as a function of time for transmitting to the serving base station the indication of the need for a handover.