Interference Avoidance In A WCDMA System

• US 20100178921A1
• Filed: 05/31/2007
• Published: 07/15/2010
• Est. Priority Date: 05/31/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Ghasemzadeh, Farshid, Aqvist, Hans
• Granted Patent: US 8,725,157 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04W 36/04 Reselecting a cell layer in multi-layered cells
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B

Abstract

A method for a cellular system comprising base stations of a first and a second kind, which control cells of a first and second kinds, and a control function for the base station of the first kind. The control function maintains a list of cells in the vicinity of the first cell, a Neighbour Cell list, and a UE in the first cell measures transmissions from Neighbour Cells and reports them, and said UE makes Detected Set, DS, measurements, and reports them to the control function. The control function searches DS measurement reports for cells of the second kind, and if a cell of the second kind is found, a hand over of the UE is initiated, to prevent transmissions from the UE to cause interference in the base station of the second kind.

Claims

1. A method (200) for use in a wireless cellular telephony system (100), said system comprising a first base station (111) of a first kind and a second base station (125-127) of a second kind, which control a cell of a first (110) and a second (120-122) kind respectively, each cell being able to accommodate a number of user terminals, UEs, the cells of the first and second kinds having respective coverages which at least partially coincide with each other, the system (100) additionally comprising a control function (140) for the base station of the first kind (111), the method comprising the following:

letting (210) said control function (140) maintain a first list of cells which are in the vicinity of the first cell, a Neighbour Cell list,

letting (220) a first UE (112) in the first cell measure transmissions from Neighbour Cells and report them to said control function,

letting (230) said first UE (112) detect transmissions from cells which are not Neighbour cells of the first cell, so called Detected Set, DS, measurements, and report them to said control function,

the method being characterized in that it additionally comprises;

letting (240) said control function (140) search DS measurement reports to identify cells of the second kind (120-122),

if (250) a cell of the second kind is found in a DS measurement report, the control function initiates a hand over of the reporting UE, in order to prevent transmissions from the reporting UE to cause interference in the base station of the second kind.

2. The method (200, 260) of claim 1, according to which said hand over is a hand over to another operating frequency.

3. The method (200, 270) of claim 1, according to which said hand over is a hand over to a wireless cellular telephony system of another standard.

4. The method (200, 280) of any of the previous claims, applied to a WCDMA system.

5. The method (200, 280) of claim 4, according to which the control function (140) maintains a list of scrambling codes used by the base stations of the second kind (125-127), by means of which cells of the second kind can be identified in the DS reports.

6. The method (200, 280) of claim 4 or 5, according to which the controlling function (140) is a Radio Network Controller, an RNC.

7. A node (300) for use in a wireless cellular telephony system (100), said system comprising a first base station (110) of a first kind and a second base station (125-127) of a second kind, which control a cell of a first (110) and a second (120-122) kind respectively, each cell being able to accommodate a number of user terminals, UEs, the cells of the first and second kinds having respective coverages which at least partially coincide with each other, the node (300) being intended to serve as a control function (140) for the base station of the first kind, and comprising the following:

means (350) for maintaining a first list of cells which are in the vicinity of the first cell, a Neighbour Cell list,

means (310, 330) for receiving from a first UE in the first cell reports regarding measured transmissions from Neighbour Cells,

means (310, 330) for receiving from said first UE reports regarding detected transmissions from cells which are not Neighbour cells of the first cell, so called Detected Set, DS, measurements,

the node (300) being characterized in that it additionally comprises;

means (340, 350) for searching DS measurement reports to identify cells of the second kind,

means (340, 320, 310) for initiating a hand over of the reporting UE, if a cell of the second kind is found in a DS measurement report, in order to prevent transmissions from the reporting UE to cause interference in the base station of the second kind.

8. The node (300) of claim 7, in which said means (340, 320, 310) for hand over initiate a hand over to another operating frequency.

9. The node of claim 7, in which said means (340, 320, 310) for hand over initiate a hand over to a wireless cellular telephony system of another standard.

10. The node (300) of any of claims 7-9, being a Radio Network Controller in a WCDMA system.

11. The node (300) of claim 10, which maintains a list of scrambling codes used by the base stations (125-127) of the second kind, by means of which cells (120-122) of the second kind can be identified in the DS reports.