Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-03-10
2001-09-11
Trost, William G. (Department: 2683)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S439000, C455S562100, C455S452200, C455S450000
Reexamination Certificate
active
06289219
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for performing a handover between sub-cells in a cellular radio network base station applying dynamic channel allocation, the base station comprising: at least two sub-cells; in each sub-cell, an antenna unit with a fixed connection to the base station; a radio connection via the antenna unit to a subscriber terminal located in a sub-cell; at least one transceiver arranged to measure reception power from the radio connection; in which method: the reception power of a signal sent by the subscriber terminal on the radio connection is measured via an antenna unit of a serving sub-cell; the reception power of a signal sent by the subscriber terminal on the radio connection is measured in turn via antenna units of other than the serving sub-cell; a handover between sub-cells is performed from an antenna unit of the serving sub-cell to an antenna unit of another sub-cell providing a better reception power.
BACKGROUND OF THE INVENTION
A problem in the above described arrangement is that a transceiver providing a radio connection can only measure the power of a received signal via one antenna unit at a time. When another antenna, other than the serving sub-cell's antenna unit, is connected to the transceiver and is used for measuring a received signal, the data the signal in question can be lost if its quality is too poor for it to be interpreted. In the worst case the radio connection can even be terminated.
A possible solution would be to receive every second received signal, at the most, via another than the serving sub-cell's antenna unit. Then the quality of the radio connection might not be as degraded, because of lost bursts. A problem would arise, however, because the measurements for performing a handover may take too long, which impairs the success of the handover.
BRIEF DESCRIPTION OF THE INVENTION
An object of the invention is thus to provide a method and an equipment implementing the method so as to allow the above problems to be solved.
This is achieved with a method described in the preamble, characterized in that: signals sent by the subscriber terminal on the radio connection and received via the antenna unit of the serving sub-cell and the antenna unit of the other sub-cell are combined to provide a combined signal; a handover is performed from the antenna unit of the serving sub-cell to the antenna unit of the other sub-cell when, as a result of a comparison of the combined signal with the signal of the serving sub-cell, the reception power of the signal received via the antenna unit of the other sub-cell is detected to be better than the reception power of the signal received via the antenna unit of the serving sub-cell.
The invention also relates to a cellular radio network base station comprising: dynamic channel allocation; at least two sub-cells; in each sub-cell, an antenna unit with a fixed connection to the base station; a radio connection via an antenna unit to a subscriber terminal located in a sub-cell; at least one transceiver arranged to measure reception power from the radio connection; a switching field for connecting radio connection signals to travel between a particular transceiver and antenna unit; a control unit controlling the switching field and communicating with the transceivers.
The base station is characterized in that the switching field comprises at least one switch for combining signals sent by the subscriber terminal on the radio connection and received via the antenna unit of the serving sub-cell and the antenna unit of another sub-cell to generate a combined signal; the control unit is arranged to perform a handover from the antenna unit of the serving sub-cell to the antenna unit of the other sub-cell when a comparison of the combined signal with the signal of the serving sub-cell shows that the reception power of the signal received via the antenna unit of the other sub-cell is better than the reception power of the signal received via the antenna unit of the serving sub-cell.
Preferred embodiments of the invention are disclosed in the dependent claims.
The basis of the invention is that two signals, i.e. one of a serving sub-cell and of another cell, received via different antenna units are combined and the reception power is measured from the combined signal, instead of the individual signals being measured. A comparison of the measurement result of the combined signal with the measurement result of the signal of the serving sub-cell allows conclusions to be made about the mutual relationship between the reception powers on the basis of which the best antenna unit for a handover can be selected.
A method and arrangement of the invention provide several advantages. The reliability of handover improves. The quality of radio connection remains good also during handover because bursts are not lost due to reception power measurement because also the signal received via the antenna unit of the serving sub-cell is utilized all the time.
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M. Mouley Et Al, “The GSM System for Mobile Communications”, The GSM System, 1992, p. 396, line 3—line 22.
“Aspects of Discontinuous Tranmissions (DTX)),” The GSM System, Apr. 1993, pp. 18-20.
Patronen Petri
Ryynänen Jari
Milord Marceau
Nokia Networks Oy
Pillsbury & Winthrop LLP
Trost William G.
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