Method and apparatus for a sectored cell of a cellular radio communications system

• US 6,167,036 A
• Filed: 11/24/1998
• Issued: 12/26/2000
• Est. Priority Date: 11/24/1998
• Status: Expired due to Fees

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Beven, David Damian Nicholas
• Primary Examiner(s): Marcelo, Melvin
• Assistant Examiner(s): Nguyen, Phuongchau Ba
• Application Number:
  US09/198,387
• Time in Patent Office: 763 Days
• Field of Search: 370/331, 370/335, 370/342, 455/442, 455/435, 455/440
• US Class Current: 370/331
• CPC Class Codes: H04B 7/0491 using two or more sectors, i.e. sector diversity
• CPC Class Codes: H04W 16/24 Cell structures
• CPC Class Codes: H04W 36/00692 using simultaneous multiple data streams, e.g. cooperative multipoint [CoMP], carrier aggregation [CA] or multiple input multiple output [MIMO] allocation of physical resources in CoMP or in CA H04L5/0035
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

A nine-sectored cell (20) of a cellular radio communications system has three base transceiver stations (BTSs) colocated at its cell site (26). Each BTS is substantially independently coupled to a remote base station controller (BSC). Each BTS handles communications with subscriber units within a respective coverage area including three mutually-adjacent sectors (e.g. a1, b1, c1). When a subscriber unit moves between the coverage areas of different BTSs, a soft handoff is controlled by the BSC. When a subscriber unit moves between two sectors in the same coverage area, a softer handoff is implemented by the respective BTS.

Claims

1. Cell-site equipment for location at a cell-site of a cell in a code division multiple access (CDMA) cellular radio communications system, said cell having more than one sector, comprising:

one or more antennas for generating a plurality of radio communications main beams, a respective one of said main beams covering each one of said sectors; and

a plurality of base transceiver stations (BTS), each BTS being independently coupled to a base station controller (BSC) and coupled to one or more of said antennas for handling communications in a respective coverage area comprising one or more of said sectors, at least one of said BTSs handling communications in a coverage area comprising two mutually-adjacent sectors, such that a subscriber unit located in a sector in a coverage area of a BTS communicates with said BTS using said respective main beam covering said sector;

said cell-site equipment operating such that, if a subscriber unit moves from a first of said sectors to a second of said sectors, said first of said sectors being in said coverage area of a first of said BTSs and said second of said sectors being in said coverage area of a second of said BTSs, then radio communication between said subscriber unit and said second of said BTSs is set up by means of a soft handoff, said soft handoff being controlled bv said BSC;

and said cell-site equipment operating such that, if a subscriber unit moves from a first of said sectors to a second of said sectors, said first of said sectors and said second of said sectors being in said coverage area of the same one of said BTSs, then radio communication in said second sector between said subscriber unit and said one of said BTSs is set up by means of a softer handoff, said softer handoff being controlled by said one of said BTSs.

2. Cell-site equipment according to claim 1, in which said plurality of BTSs is a plurality of substantially identical BTSs.

3. Cell-site equipment according to claim 1, in which said coverage area of one of said BTSs comprises more than one sector, and said one or more antennas to which said one of said BTSs is coupled comprises a phased-array antenna which generates a plurality of main beams, a respective one of said main beams covering each of said sectors.

4. Cell-site equipment according to claim 3, in which said phased-array antenna comprises a row of spaced antenna elements or columns of antenna elements, and amplitude tapering is applied to one or more elements or columns of elements at each end of said row, or is applied across the row so that the amplitude-tapering decreases towards the centre of the row.

5. Cell-site equipment according to claim 1, comprising one or more antennas coupled to each BTS for generating one or more beams to cover said respective coverage area, in which said one or more antennas coupled to one of said BTSs includes a main beam antenna and a diversity beam antenna.

6. Cell-site equipment according to claim 5, in which said coverage area of one of said BTSs comprises three sectors, said main-beam antenna generates three main beams, one covering each sector, and said diversity-beam antenna generates two diversity beams covering the cusp regions between said main beams.

7. Cell-site equipment according to claim 1, comprising a means for identifying a subscriber unit communicating from a position close to a cell-site at which said cell-site equipment is located, and enabling adequate control of the power of transmissions from said subscriber unit to prevent swamping of communications with other subscriber units.

8. A cell site of a cellular radio communications system comprising cell-site equipment as defined in claim 1.

9. A base station controller for use in cell-site equipment as defined in claim 1.

10. An antenna for use in cell-site equipment as defined in claim 1.

11. A method for operating a cell of a code division multiple access (CDMA) cellular radio communications system, said cell having a cell site at which a plurality of base transceiver stations (BTSs) is located, each BTS being independently coupled to a base station controller (BSC), and each BTS being coupled to one or more antennas for generating one or more radio communications main beams, said cell being divided into a plurality of sectors such that a respective one of said main beams carries communications to and from subscriber units located in each one of said sectors, and each of said BTSs handles such communications in a coverage area comprising one or more of said sectors, said method comprising:

handling communications with subscriber units in each of said coverage areas using a respective one of said BTSs;

when a subscriber unit moves between a first of said sectors and a second of said sectors within different ones of said coverage areas, handling a transfer of communications from said first of said sectors to said second of said sectors by means of a soft handoff, under the control of said BSC; and

when a subscriber unit moves between a first of said sectors and a second of said sectors, both of said sectors being within said coverage area of one of said BTSs, handling a transfer of communications between said first of said sectors and said second of said sectors by means of a softer handoff, under the control of said one of said BTSs.

12. A method according to claim 11, comprising the step of identifying a subscriber unit communicating from a position near said cell site and controlling the power of communications from said subscriber unit to avoid swamping of communications with other subscriber units.

13. A method for upgrading a cell of a code division multiple access (CDMA) cellular radio communications system having a cell site at which one or more BTSs are located, each said BTS being coupled to a base station controller (BSC), by increasing the number of BTSs at said cell site and increasing the sectorisation of said cell, communications with subscriber units in each sector being carried by a respective radio communications main beam generated by an antenna at said cell site, and each BTS handling communications in a coverage area comprising one or more respective sectors of said cell, a transfer of communications between sectors when a subscriber unit moves between two sectors in said coverage areas of two different BTSs being handled by means of a soft handoff, under the control of said BSC, and a transfer of communications between sectors when a subscriber unit moves between two sectors in said coverage area of the same BTS being handled by means of a softer handoff, under the control of said BTS.

14. A method according to claim 13, in which said cell is of a predetermined area before upgrading and the area of said cell after upgrading is greater than the area of said cell before upgrading.

15. A method according to claim 13, in which each BTS at said cell site after upgrading is independently coupled to a base station controller (BSC), and in which a soft handoff is implemented substantially under the control of the BSC, and a softer handoff is implemented substantially under the control of the BTS handling communications in the first and second sectors.