US 8,411,555 B2 · Quality based handover procedure between co-located cells

Abstract

The present invention relates to cellular system and especially to handover between cells on different frequency carriers in an OFDM system or between cells in 2 systems adopting different radio access technologies (RAT), at least one of them being OFDM technology. A problem is the intra-cell interference impact on the quality a connected mode terminal measures in the own cell and in neighbor cells. This is a problem for cells based on OFDM technology, because intra-cell interference has no impact as compared to the inter-cell interference on the quality provided by the cell to a connected mode terminal, whereas in UTRA the intra-cell and inter-cell interference have the same impact on the quality provided. The solution to the problem is based on the insight that for cells that are located on the same site, the eNode B possess information on the power transmitted on the respective frequency carrier, and can adjust the quality as reported from the terminal on co-located OFDM cells. The adjusted quality measure enables an improved evaluation of the quality of co-located cells, for a potential handover. The invention also relates to embodiments on a 2-step handover, wherein handover to inter-frequency, or inter-RAT cell on another site is made as a handover to co-located inter-frequency/inter-RAT cell and a handover to an intra-frequency cell located at the other site.

Claims17

Dependent claims

A method for evaluating a second cell for a potential handover of a terminal that is served by a first cell, wherein the first and the second cells are co-located, and wherein the second cell is operating on a second frequency carrier in a OFDM system and the first cell operating on a first frequency carrier other than the second frequency carrier in the OFDM system or the first cell is operating in another radio access technology system than the OFDM system, the method comprising:

receiving measures from the terminal on the quality of the first and the second cell, wherein the quality measure of the first and second cells comprises an intra-cell interference component and the quality measure of the first cell includes an intra-cell interference component if the first cell is included in the OFDM system;
detecting the downlink carrier power of the second cell;
adjusting the quality measure received from the second cell, by compensating for the intra-cell interference component in the quality measures and compensating for the intra-cell interference component in the quality measure of the first cell if the first cell is included in the OFDM system;
evaluating the best cell for serving the terminal by comparing the adjusted quality measure of the second cell with the quality measure of the first cell, as adjusted if the first cell is included in the OFDM system.

1 more element

A mobile terminal arranged for communication with a cellular radio network via a serving cell, and arranged for performing quality measurements on the serving ceil and on OFDM technology cells neighbouring the serving cell, and further arranged for receiving information on which neighbouring cell/s that is/are co-located with a serving radio base station, further comprising:

means for receiving, from the serving radio base station, a compensation factor for the co-located neighbouring cell/s and for the serving cell if the serving cell is an OFDM technology cell;
means for adjusting the quality measure of the co-located neighbouring cell/s with their respective compensation factor, and for adjusting the quality of the serving cell if the serving cell is of OFDM technology;
and,
means for evaluating the cells by comparing the adjusted quality measure/s of the one or more co-located neighbouring cell/s with the quality measure of the serving cell, as adjusted if adjustment has been made on the serving cell, for the purpose of potentially reporting an event to the serving radio base station.

1 more element

Dependencies are inferred from the claim text.

Quality based handover procedure between co-located cells

Life of this patent

Quality based handover procedure between co-located cells

Life of this patent

Abstract

Claims17