Method and arrangement of effectively reducing signal strength measurements for a handoff in a cellular mobile communications system

• US 5,450,473 A
• Filed: 01/12/1994
• Issued: 09/12/1995
• Est. Priority Date: 01/12/1993
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Yamaguchi, Kenji, Shiotsuki, Hirofumi
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): TROST IV, WILLIAM GEORGE
• Application Number:
  US08/180,299
• Time in Patent Office: 608 Days
• Field of Search: 379/59, 379/60, 379/63, 455/33.1, 455/33.2, 455/34.1, 455/51.1, 455/54.1, 455/56.1, 370/95.1, 370/95.3, 370/110
• US Class Current: 455/441
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data

Abstract

In order to reduce the number of measurements of signal strength for implementing a handoff of a mobile unit located in a given land site, a strength of a signal transmitted from said mobile unit is measured at the land site. Further, the land site measures a level crossing rate based on the signal transmitted from the mobile to be handed off. The land site applies a handoff request to a MTSO if the land site detects that the measured signal strength falls below a predetermined handoff threshold. The handoff request includes information indicating the level crossing rate. The MTSO compares the level crossing rate with a predetermined value, and determine a plurality of land sites each of which is to measure the signal strength for implementing a handoff according to the comparison result.

Claims

1. A method of reducing the number of measurements of signal strength for implementing a handoff of a mobile unit located in a first land site in a cellular mobile communications system, said handoff being controlled by a MTSO (Mobile Telephone Switching Office) included in said cellular mobile communications system, said method comprising the steps of:

(a) measuring a strength of a signal transmitted from said mobile unit at said first land site;

(b) measuring a level crossing rate based on said signal transmitted from said mobile at said first land site;

(c) applying a handoff request from said first land site to said MTSO if said first land site detects that the strength of said signal from said mobile unit falls below a predetermined handoff threshold, said handoff request including information indicating level crossing rate;

(d) comparing said level crossing rate with a predetermined value at said MTSO; and

(e) selecting, at said MTSO, between at least a first plurality of land sites and a second plurality of land sites, said second plurality comprising at least some of said first plurality of land sites, each of said first and second plurality of land sited being operative to measure said signal strength for implementing said handoff according to a comparison result obtained in step (d).

2. A method of reducing the number of measurements of signal strength for implementing a handoff of a mobile unit located in a first land site in a cellular mobile communications system, said handoff being controlled by a MTSO (Mobile Telephone Switching Office) included in said cellular mobile communications system, said method comprising the steps of:

(a) measuring a strength of a signal transmitted from said mobile unit at said first land site;

(b) measuring a level crossing rate based on said signal transmitted from said mobile at said first land site;

(c) applying a handoff request from said first land site to said MTSO if said first land site detects that the strength of said signal from said mobile unit falls below a predetermined handoff threshold, said handoff request including information indicating level crossing rate;

(d) comparing said level crossing rate with a predetermined value at said MTSO; and

(e) determining, at said MTSO, a plurality of land sites each of which is to measure said signal strength for implementing said handoff according to a comparison result obtained in step (d);

wherein if the land crossing rate is less than the predetermined value, then said plurality of land sites for measuring said signal strength are a second group of land sites each of which borders said first land site, and

wherein if the land crossing rate is greater than or equal to the predetermined value, then said plurality of land sites for measuring said signal strength are a third group of land sites including the land sites included in the second group and additional land sites which border said second group of land sites

3. An arrangement for reducing the number of measurements of signal strength for implementing a handoff of a mobile unit located in a first land site in a cellular mobile communications system, said handoff being controlled by a MTSO (Mobile Telephone Switching Office) included in said cellular mobile communications system, said arrangement comprising:

first means for measuring a strength of a signal transmitted from said mobile unit, said first land site including said first means;

second means for measuring a level crossing rate based on said signal transmitted from said mobile, said first land site including said second means;

third means for applying a handoff request from said first land site to said MTSO if said first land site detects that the strength of said signal from said mobile unit falls below a predetermined handoff threshold, said handoff request including information indicating level crossing rate, said first land site including said third means;

fourth means for comparing said level crossing rate with a predetermined value, said MTSO including said fourth means; and

fifth means for selecting between at least a first plurality of land sites and a second plurality of land sites, said second plurality comprising at least some of said first plurality of land sites, each of said first and second plurality of land sited being operative to measure said signal strength for implementing said handoff according to a comparison result obtained from said fourth means, said MTSO including said fifth means.

4. An arrangement for reducing the number of measurements of signal strength for implementing a handoff of a mobile unit located in a first land site in a cellular mobile communications system, said handoff being controlled by a MTSO (Mobile Telephone Switching Office) included in said cellular mobile communications system, said arrangement comprising:

first means for measuring a strength of a signal transmitted from said mobile unit, said first land site including said first means;

second means for measuring a level crossing rate based on said signal transmitted from said mobile, said first land site including said second means;

third means for applying a handoff request from said first land site to said MTSO if said first land site detects that the strength of said signal from said mobile unit falls below a predetermined handoff threshold, said handoff request including information indicating level crossing rate, said first land site including said third means;

fourth means for comparing said level crossing rate with a predetermined value, said MTSO including said fourth means; and

fifth means for determining a plurality of land sites each of which is to measure said signal strength for implementing said handoff according to a comparison result obtained from said fourth means, said MTSO including said fifth means;

wherein if the land crossing rate is less than the predetermined value, then said plurality of land sites for measuring said signal strength are a second group of land sites each of which borders said first land site, and

wherein if the land crossing rate is greater than or equal to the predetermined value, then said plurality of land sites for measuring said signal strength are a third group of land sites comprising the land sites included in the second group and additional land sites which border said second group of land sites.