Method for determining a candidate cell for an active set

Abstract

A method (200, 300, 400) according to the invention is a method for determining a condidate cell for an active set, where the quality factor of each cell in the active set is determined (202), a quality factor of a test cell is determined (203), and the test cell is accepted (205) as a candidate cell for the active set if an acceptance criterion is fulfilled. The method is characterized in that the acceptance criterion is selected (201) so that for a certain first quality factor of a test cell and for a certain first set of quality factors, consisting of quality factors of the cells in a first active set, the acceptance criterion has the same value as for a certain second quality factor of a test cell and for a certain second set of quality factors, consisting of quality factors of cells in a second active set, when the first quality factor is equal to the second quality factor multiplied with any finite number and the first set of quality factors is the same as a set formed of the quality factors belonging to the second set of quality factors multiplied with the same finite number. The invention relates also to an arrangement, to a mobile station and to a network element where decisions about accepting a cell as a candidate cell for the active set are done.

Description

PRIORITY CLAIM[0001]This is a national stage of PCT application No. PCT / FI00 / 00796, filed on Sep. 20, 2000. Priority is claimed on that application, and on patent application No. 19992005 filed in Finland on Sep. 20, 1999.FIELD OF THE INVENTION[0002]The invention relates in general to cellular networks. In particular the invention relates to soft handovers in cellular networks.BACKGROUND OF THE INVENTION[0003]Transmission diversity refers to a situation where at least two transmitters are transmitting the same data flow to a receiver. For example, a mobile station may receive radio transmissions from two base stations of a cellular network simultaneously. One of the advantages of the transmission diversity is that if the quality or strength of one of the received radio transmissions decreases, the quality of some other received transmissions may still be high enough for receiving data reliably.[0004]A situation where a mobile station communicates with more than one base stations sim...

AI Technical Summary

Benefits of technology

"The invention is a method for determining which cells should be included in an active set for a certain network. The method selects an acceptance criterion that is independent of the specific quality factors of the cells. The method uses a finite number of limit values to determine if a cell should be included in the active set. The method also includes a method for determining which cells should be removed from the active set. The invention provides a network element that includes means for determining quality factors for cells and means for selecting an acceptance criterion. The technical effects of the invention include improved network performance and more efficient use of network resources."

Problems solved by technology

There may be other conditions, for example that the active set may not be modified too frequently, that hinder the adding of a new cell to the active set.

The problem with the current acceptance criterion is that it does not ensure proper acceptance decisions when the value of S is different from 0 or 1.

A further problem with the acceptance criterion is that for an active set whose cells have the same quality factors, from here on called an uniform active set, the acceptance limit is not equal to the quality factor.

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