Sectored voice channels with rear lobe protection

• US 5,161,249 A
• Filed: 11/18/1991
• Issued: 11/03/1992
• Est. Priority Date: 12/19/1989
• Status: Expired due to Fees

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Hanley, Donald V., Chaplain, Eugenie M., Meche, Paul S.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): FAILE, ANDREW I
• Application Number:
  US07/794,636
• Time in Patent Office: 351 Days
• Field of Search: 455/32-34, 455/56, 455/62, 455/67, 455/63, 455/53, 455/54, 455/33.1, 455/33.3, 455/33.4, 455/161.2, 379/60
• US Class Current: 455/436
• CPC Class Codes: H04W 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 72/541 using the level of interference

Abstract

An improved method of initiating handoffs between sectors so as to reduce sectored voice channel interference is disclosed. The sectors that are adjacent and to the rear of the sector that is serving the mobile unit are scanned for signal quality. A handoff request message is sent to the cell controller if the signal quality detected by any of the scanned sectors is better than the signal quality read at the sector serving the mobile unit. When the handoff request message is received at the cell controller, a voice channel is allocated to the cell and sector associated with the scanned sector specified as having the better signal. A handoff process from the voice channel currently serving the mobile unit to the newly allocated voice channel in the specified sector, is then initiated.

Claims

1. A method of reducing sectored voice channel interference when a mobile telephone user moves from a serving sector of a cell to a sector adjacent or to the rear thereof, the method comprising the steps of:

a) positioning a first set of antennas in a first set of sectors of the cell;

b) connecting each antenna of said first set to a first receiver;

c) positioning a second set of antennas in a second set of sectors, said second set of sectors comprising sectors adjacent and in between the sectors of said first set;

d) connecting each antenna of said second set to a second receiver;

e) continuously scanning at least the sectors adjacent and to the rear of said serving sector as the mobile moves from the serving sector to another sector;

f) sending a handoff request message to a cell controller if the signal quality detected from a receiver connected to a non-serving sector exceeds the signal quality read by a receiver connected to said serving sector;

g) receiving the handoff request at the cell controller;

h) allocating a voice channel on the scanned sector having the better signal quality; and

i) initiating a handoff process such that the mobile telephone user can e served by a voice channel on said receiver connected to said non-serving sector.

2. A system for reducing sectored voice channel interference when a mobile telephone user moves from a serving sector of a cell to a sector adjacent or to the rear thereof, said system comprising:

a) a first set of antennas positioned in a first set of sectors of the cell, each antenna of said first set being connected to a first receiver;

b) a second set of antennas positioned in a second set of sectors comprising sectors adjacent and in between the sectors of said first set, each antenna of said second set being connected to a second receiver;

c) means for continuously scanning at least the sectors adjacent and to the rear of said serving sector as the mobile moves from the serving sector to another sector;

d) means for sending a handoff request message to a cell controller when the signal quality detected from a receiver connected to non-serving sector exceeds the signal quality read by a receiver connected to said serving sector;

e) means for allocating a voice channel on the scanned sector having the better signal quality; and

i) means for initiating a handoff process such that the mobile telephone user can be served by a voice channel on said connected to said non-serving sector.

3. A mobile communications base station serving a communications cell divided into a plurality of sectors comprising:

at least one directional receive attenna;

separate receive antenna ports for providing a separate signal from each sector within the communications cell, the sectors being grouped into at least a first sector group and a second sector group, each of the sectors of the first sector group covering an area adjacent to and between sectors of the second sector groups;

a plurality of allocatable voice channels connectable to said receive antenna ports;

at least two receivers, a first of the receivers being connected to antenna ports corresponding to the first sector group and a second receiver being connected to antenna ports corresponding to the second sector group, wherein one receiver is selectable by an active voice channel to service communication with a mobile unit in a sector corresponding to a receive antenna port providing a highest signal quality for said active voice channel and wherein remaining receivers are selectable to scan other said antenna ports for signal quality of said active voice channel;

a cell controller dynamically responsive to said active voice channel to hand off a mobile unit from a voice channel corresponding to a first sector to a voice channel corresponding to another sector having a higher signal quality.

4. The method recited in claim 3 wherein said first receiver receives signals from the mobile unit in said sector that is servicing the mobile unit and said second receiver scans a plurality of sectors including at least said sectors adjacent to and to the rear of the sector servicing the mobile.

5. The method recited in claim 4, wherein a cell has an even number of generally triangular shaped sectors having a common intersection point and wherein the first and second receivers respond to signals in alternate sectors.

6. The method recited in claim 3 wherein one of a plurality of receivers receives signals from the mobile unit in said sector servicing the mobile unit and remaining receivers scan a plurality of sectors including a t least sectors adjacent to and to the rear of the sector that is servicing the mobile unit.

7. The apparatus recited in claim 3 wherein said remaining receivers are selectable to scan at least two sectors, one being adjacent to said sector servicing the mobile and the other sector being to the rear of said sector servicing the mobile.