Optimum power and handover control by cellular system mobile unit

• US 5,845,212 A
• Filed: 10/04/1996
• Issued: 12/01/1998
• Est. Priority Date: 10/11/1995
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Tanaka, Shoji
• Primary Examiner(s): Vo, Nguyen
• Assistant Examiner(s): Kincaid, Lester G.
• Application Number:
  US08/726,360
• Time in Patent Office: 788 Days
• Field of Search: 455/437, 455/436, 455/69, 455/522, 455/13.4, 455/126, 455/70, 455/127
• US Class Current: 455/437
• CPC Class Codes: H04W 36/0085 Hand-off measurements
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

A mobile communication system of a cellular type has in each cell a base station (12a-12c) for carrying out bidirectional communication between the base station and a mobile station (11). The base station announces a transmission power of the base station and up link reception power and up link signal quality as information to the mobile station. The mobile station judges whether nor not it is necessary to carry out a hand-over control in accordance with the information and a predetermined hand-over control information. The mobile station judges whether or not it is necessary to carry out said hand-over control in accordance with a down link received signal strength indicator, a down link received signal quality, and the predetermined hand-over control information. The mobile station may judge whether or not it is necessary for the base station to carry out a base transmission power control in accordance with the information and a base maximum transmission power. Furthermore the mobile station may judge whether or not it is necessary for the mobile station to carry out a mobile transmission power control in accordance with the information and a mobile maximum transmission power.

Claims

1. A mobile communication system of a cellular type having a service area divided into a plurality of cells and comprising in each of said cells a base station for carrying out bidirectional communication between said base station and said mobile station, said base station transmitting a base transmission signal to said mobile station at a base transmission power on a bidirectional communication resource, said mobile station transmitting a mobile transmission signal to said base station at a mobile transmission power on a bidirectional communication resource, wherein said base station comprises:

first measuring means for measuring a received signal strength indicator and a received signal quality in accordance with said mobile transmission signal to produce first measured information;

first announcing means for announcing said first measured information and said base transmission power as base announcement information to said mobile station;

first receiving means for receiving mobile announcement information from said mobile station; and

first control means for controlling said base transmission power in accordance with said mobile announcement information;

said mobile station comprising;

second measuring means for measuring a received signal strength indicator and a received signal quality as a base received signal strength indicator and a base received signal quality in accordance with said base transmission signal to produce second measured information;

second receiving means for receiving said base announcement information from said base station;

first judging means for judging whether or not it is necessary to carry out a hand-over control in accordance with said second measured information, said base transmission power, and a predetermined hand-over control information, said first judging means further judging whether or not it is necessary for said base station to carry out a base transmission power control in accordance with said second measured information, said base transmission power and a base maximum transmission power to produce a base power control signal when it is necessary for said base station to carry out said base transmission power control;

second judging means for judging whether or not it is necessary to carry out said hand-over control in accordance with said first measured information and said predetermined hand-over control information, said second judging means further judging whether or not it is necessary for said mobile station to carry out a mobile transmission power control in accordance with said first measured information and a mobile maximum transmission power to produce a mobile power control signal when it is necessary for said mobile station to carry out said mobile transmission power control;

second announcing means for announcing said base power control signal as mobile announcement information to said base station; and

second control means for controlling said mobile transmission power in accordance with said mobile power control signal.

2. A mobile communication system as claimed in claim 1, wherein said base station further comprises broadcasting means for broadcasting said predetermined hand-over control information representative of up link and down link hand-over levels.

3. A mobile communication system as claimed in claim 2, wherein said broadcasting means further broadcasts base maximum power information and mobile maximum power information, said base maximum power information being representative of a maximum transmission power of said base station, said mobile maximum power information being representative of a maximum transmission power of said mobile station.

4. A mobile communication system as claimed in claim 3, wherein said first judging means comprises:

first means responsive to said second measured information and said predetermined hand-over control information for judging whether or not each of said base received signal strength indicator and said base received signal quality is less than said down link hand-over level to produce a first judgement result signal when each of said base received signal strength indicator and said base received signal quality is less than said down link hand-over level;

second means responsive to said first judgement result signal for judging whether or not said base transmission power is less than said base maximum transmission power to produce a second judgement result signal when said base transmission power is less than said base maximum transmission power; and

third means responsive to said second judgement result signal for making said second announcing means announce said mobile announcement information to said base station to increase said base transmission power.

5. A mobile communication system as claimed in claim 3, wherein said first judging means comprises:

first means responsive to said second measured information and said predetermined hand-over control information for judging whether or not each of said base received signal strength indicator and said base received signal quality is less than said down link hand-over level to produce a first judgement result signal when each of said base received signal strength indicator and said base received signal quality is less than said down link hand-over level;

second means responsive to said first judgement result signal for judging whether or not said base transmission power is less than said base maximum transmission power to produce a second judgement result signal when said base transmission power is not less than said base maximum transmission power; and

third means responsive to said second judgement result signal for carrying out said hand-over control.

6. A mobile communication system as claimed in claim 3, wherein said first judging means comprises:

first means responsive to said second measured information and said predetermined hand-over control information for judging whether or not each of said base received signal strength indicator and said base received signal quality is less than said down link hand-over level to produce a first judgement result signal when said base received signal quality is less than said down link hand-over level and when said base received signal strength indicator is not less than said down link hand-over level;

second means responsive to said first judgement result signal for judging whether or not said base transmission power is less than said base maximum transmission power to produce a second judgement result signal when said base transmission power is not less than said base maximum transmission power; and

third means responsive to said second judgement result signal for selecting another radio channel as a communication channel to communicate with said base station.

7. A mobile communication system as claimed in claim 3, wherein said second judging means comprises:

first means responsive to said first measured information and said predetermined hand-over control information for judging whether or not each of said mobile received signal strength indicator and said mobile received signal quality is less than said up link hand-over level to produce a first judgement result signal when each of said mobile received signal strength indicator and said mobile received signal quality is less than said up link hand-over level;

second means responsive to said first judgement result signal for judging whether or not said mobile transmission power is less than said mobile maximum transmission power to produce a second judgement result signal when said mobile transmission power is less than said mobile maximum transmission power; and

third means responsive to said second judgement result signal for making said second control means increase said mobile transmission power.

8. A mobile communication system as claimed in claim 3, wherein said second judging means comprises:

first means responsive to said first measured information and said predetermined hand-over control information for judging whether or not each of said mobile received signal strength indicator and said mobile received signal quality is less than said up link hand-over level to produce a first judgement result signal when each of said mobile received signal strength indicator and said mobile received signal quality is less than said up link hand-over level;

second means responsive to said first judgement result signal for judging whether or not said mobile transmission power is less than said mobile maximum transmission power to produce a second judgement result signal when said mobile transmission power is not less than said mobile maximum transmission power; and

third means responsive to said second judgement result signal for carrying out said hand-over control.

9. A mobile communication system as claimed in claim 3, wherein said second judging means comprises:

first means responsive to said first measured information and said predetermined hand-over control information for judging whether or not each of said mobile received signal strength indicator and said mobile received signal quality is less than said up link hand-over level to produce a first judgement result signal when said mobile received signal quality is less than said up link hand-over level and when said mobile received signal strength indicator is not less than said up link hand-over level;

second means responsive to said first judgement result signal for judging whether or not said mobile transmission power is less than said mobile maximum transmission power to produce a second judgement result signal when said mobile transmission power is not less than said mobile maximum transmission power; and

third means responsive to said second judgement result signal for selecting another radio channel as a communication channel to communicate with said base station.

10. A cellular communication power and handover control system directed by a mobile unit evaluating system parameters and providing instruction to a base unit, comprising:

a base unit announcer for said base unit announcing to said mobile unit an up link received signal strength indicator, an up link received signal quality, and a current base unit transmission power;

a base unit controller for controlling said base unit transmission power responsive to a base power control instruction from said mobile unit;

mobile unit system parameter evaluation unit for receiving said announced up link received signal strength indicator, said up link received signal quality, and said current base unit transmission power, a down link received signal strength indicator, a down link signal quality, and a current mobile transmission power, said mobile unit system parameter evaluation unit structured and arranged to evaluate;

i) whether to issue a said base power control instruction to said base unit controller by comparing said down link received signal quality to a down link signal quality hand-over point, and by comparing said current base transmission power to a maximum base transmission power;

ii) whether to issue a hand-over command to change bases by comparing said down link received signal quality to a down link signal quality hand-over point, and by comparing said down link received signal strength indicator to a down link received signal strength hand-over point;

iii) whether to issue a mobile power control instruction by comparing said up link received signal quality to an up link signal quality hand-over point, and by comparing said current mobile transmission power to a maximum mobile transmission power; and

iv) whether to issue a hand-over command to change channels by comparing said up link received signal quality to an up link signal quality hand-over point, and by comparing said up link received signal strength indicator to an up link received signal strength hand-over point.

11. The system of claim 10, wherein said mobile unit system parameter evaluation unit further evaluates:

v) whether to issue a said hand-over command to change bases by comparing said up link received signal quality to an up link signal quality hand-over point, by comparing said up link received signal strength indicator to an up link received signal strength hand-over point, and by comparing up link received signal strength indicators from additional base units to said up link received signal strength hand-over point.

12. The system of claim 11, wherein said mobile unit system parameter evaluation unit further evaluates:

vi) whether to issue a said hand-over command to change bases by comparing said down link received signal quality to a down link signal quality hand-over point, by comparing said down link received signal strength indicator to a down link received signal strength hand-over point, and by comparing down link received signal strength indicators from additional base units to said down link received signal strength hand-over point.

13. The system of claim 12, wherein said down link signal quality hand-over point, said maximum base transmission power, said down link received signal strength hand-over point, said up link signal quality hand-over point, said maximum mobile transmission power, and said up link received signal strength hand-over point, are transmitted from said base unit to said mobile unit.