BACKGROUND OF THE INVENTION Generally, base stations in a radio system are sectored. Each sec- tor comprises at least two transceivers and a combiner. A combiner comprises a filtering structure to filter signals as desired. In addition, the combiner com- prises a combining structure to combine the filtered signals to the same an- tenna cable. The transceivers and the combiner are combined by cables such that each transceiver has a cable connection of its own to the combiner. In a prior art method, such combinations are carried out manually, and there has been no way to check the correctness of the connections quickly and reliably.

Each cable connection between the transceivers and the combiner has a unique location determined in the combiner. Usually a sector comprises a plu- rality of transceivers, which means that the sector also comprises a plurality of cable connections to the combiner, as well as inputs for the cables in the com- biner. Hence, due to human errors, it is highly probable that the cables be- come incorrectly combined or do not become combined at all, particularly when a sector in the base station comprises a great number of cable connec- tions. Cables can also be combined to wrong sectors. Since in the prior art method it has not been able to test the combinations quickly and reliably, wrong combinations have caused great financial losses due to delays when wrong or non-existent combinations have been corrected later. Combining a new transceiver to a fully accomplished sector may also have been a prob- lematically time-consuming process.

BRIEF DESCRIPTION OF THE INVENTION An object of the invention is thus to provide a method and an appa- ratus implementing the method so as to alleviate the above-mentioned prob- lems. This is achieved by a method of the invention for checking cable con- nections between transceivers and combiners in a base station of a radio system. In the method, an output of at least two transceivers is connected to a combiner such that each transceiver has a cable connection of its own to a

corresponding input in the combiner. Each transceiver transmits a different signal to the corresponding input in the combiner by the cable, and the trans- ceivers connected to the inputs of the combiner, and thus the cable connec- tions, are identified on the basis of the different signals received by said in- puts.

The invention also relates to an arrangement for checking cable connections between transceivers and combiners. in a base station of a radio system. The arrangement comprises at least two transceivers, at least two cables and a combiner, each output of the transceivers being connected to an input of its own in the combiner by its own cable connection. Each transceiver is arranged to transmit a different signal to a corresponding input in the com- biner by the cable, and the arrangement is arranged to identify the transceiv- ers connected to the inputs of the combiner, and thus the cable connections, on the basis of the different signals received by said inputs.

Preferred embodiments of the invention are disclosed in the de- pendent claims.

The idea underlying the invention is that each transceiver transmits a different signal to the corresponding input in the combiner by the cable, and the transceivers connected to the inputs of the combiner, and thus the cable connections, are identified on the basis of the different signals received by said inputs. If no one of said different signals is received by an input of the combiner, it is assumed that no transceiver has been connected to said input.

The signals can differ in frequencies, and resonators can be provided in the inputs of the combiner to the cable connections from the transceivers. A standing wave according to the frequency of a signal received from the trans- ceiver is then formed in a resonator, and, on the basis of the standing wave, the arrangement and method of the invention are able to identify which trans- ceiver is connected to said resonator located in an input of the combiner. If the arrangement does not find a standing wave in the resonator, no transmitter is connected to the resonator. If no standing wave according to the frequency of a signal transmitted by a transceiver can be found in any resonator, the trans- mitter is not connected to any resonator in the sector at issue. The arrange- ment also identifies a transceiver located in another sector. The cable connec- tions are checked by the combiners. if the cable connecting the transceiver and the combiner is provided with a control wiring, the cable connections can be checked, i. e. controlled, also by the transceivers. In such a case, the trans-

ceiver receives information on the cable connection to the combiner by the control wiring. A new transceiver is connected to a fully accomplished sector such that the base station is provided with address information on the new transceiver; consequently, as described above, it can be checked either by the combiners or the transceivers that the new transceiver will be correctly con- nected to the combiner in its sector. The cable connections are controlled in the above-described manner either by the combiners or the transceivers typi- cally by a base station controller.

The arrangement and method of the invention are used for check- ing, quickly and reliably, the cable connections between combiners and trans- ceivers in the sectors of a base station. The invention enables the cable con- nections of the base station to be efficiently configured. The arrangement and method of the invention enable the cable connections between the combiners and the transceivers to be comprehensively defined. The invention can be used to find out whether a cable connection is totally missing or whether it is incorrectly combined, in which case the invention can be used to find out from which transceiver the cable connection originates and whereto the cable con- nection is connected in the combiner. A potential cable connection between the transceiver and the combiner between different sectors, which is always a wrong connection, can also be tracked down. A further advantage of the in- vention is that when a new transceiver is connected to a fully accomplished sector of the base station, the correctness of the connection can be quickly checked, which means that the connecting procedure is fast and reliable. The invention ensures quick and successful implementation of the cable connec- tions between the combiners and transmitters in the base station, which re- sults in saving financial resources. Additionally, the arrangement and method of the invention comprise an auto-detecting function, which can be used for monitoring all combiners and transceivers in the base station at desired inter- vals. Hence, if for some reason or other a cable connection disappears, it will be detected thanks to the auto-detection.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is now described in closer detail in connection with preferred embodiments and with reference to the accompanying drawings, in which Figure 1 shows a sectored structure of a base station,

Figure 2 shows a first preferred embodiment of the invention, and Figure 3 shows a second preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION Generally, base stations of a radio system are sectored, and each sector comprises a combiner and at least two transceivers, the transceivers being connected to the combiner.

Figure 1 shows an example of a sectored structure of a base sta- tion, which comprises three sectors 102 to 106, and each of the sectors has a combiner 108, transceivers 110, and cables 112 of its own. In the combiner, a unique input 114 is provided for each transceiver in the sector at issue. Each transceiver is connected to the input in the combiner by its own cable. The cable connections should all take place within the sector. Hence, cable con- nections from sector to sector between the combiners and the transceivers are incorrect. In addition, for transmitting and receiving, the base station com- prises unique antennas 116 for each sector. The number of transceivers may vary in different sectors. A base station controller 118 comprises a configura- tion of the base station, in other words information indicating how the cable connections in the base station between the transceivers 110 and the combin- ers 108 should be arranged. When the cables are combined manually, the cables may be connected to a wrong input in the combiner in the correct sec- tor or the cables may be connected to a combiner of another sector, or the cables may not become connected at all.

The sectors 102 to 106 in the base station transmit and receive in transmitting and receiving areas that may overlap. The transmitting and re- ceiving areas may vary in size in the different sectors 102 to 106 in the base station.

Using the arrangement and method of the invention, each trans- ceiver 110 in the base station shown by Figure 1 transmits a different signal by the cable 112 to the corresponding input 114 in the combiner 108. A corre- sponding input is an input assigned to each transceiver by the base station configuration. The transceivers 110 connected to the inputs 114 in the com- biner, and thus the cable connections 112, are identified on the basis of the different signals received by said inputs.

Figure 2 shows a first preferred embodiment of the invention, which comprises similar parts to those shown in Figure 1 and, in addition, parts that

will be introduced in the following. Outputs of the transceivers are typically ra- dio frequency outputs. The transceivers are connected to the combiner from their outputs such that each transceiver has its own cable connection to the corresponding input in the combiner. The combiner comprises filters 202, and usually each transceiver 110 in the sector has a filter of its own. Signals are filtered, typically band-pass filtered, by the filters as desired. The filtered sig- nais are combined by a combining structure 203 of the combiner 108 to a sector-specific, common antenna cable 204. The combiner can be a summing unit, for example a GMSK transmission combiner. GMSK (Gaussian Minimum Shift Keying) transmission is typically used transmission in telecommunica- tions, where a desired number of samples are collecte during a given period of time. The samples can be divided into two groups. The samples are proc- essed event by event, and a bit sequence is formed for the actual signal proc- essing, such as decoding. A resonator 206 is provided for each cable connec- tion 112 in the inputs 114 of the combiner from different transceivers 110. The resonator is preferably a cavity resonator. The combiner is preferably used in macrocells having great cell radius, in which case the combiner is used at high transmission power levels, typically being 10-100W. In such a case, the cell has a great transmitting and receiving range, or cell radius, which typically means 5-35 kilometres at the above-mentioned power range, and the cell can thus be called a macrocell.

The base station controller 118 of the base station typically has a logical structure which knows how the cable connections should be arranged between the combiner 108 and the transceiver 110 in each sector 102 to 106 of the base station. In the first preferred embodiment of the invention shown in Figure 2, the base station controller 118 finds all combiners 108 and trans- ceivers 110 in the base station. The base station controller commands all de- tected transceivers to transmit a signal to the combiner. Each transceiver transmits a signal with a different frequency to the combiner by the cable 112.

The different frequencies can be determined, for example, such that a con- stant frequency is multiplie by a bit number according to the address of each transceiver. A standing wave is thus generated for each resonator 206 in the input 114 of the combiner which has a cable connection 112 from a trans- ceiver transmitting a frequency signal. The standing wave is a spatially con- stant wave. A standing wave ratio is the ratio of the maximum and the mini- mum of the standing wave. Typically, the standing wave is a voltage wave, in

which case, when the standing wave ratio is at issue, the ratio is a ratio of the voltage maximum and the voltage minimum. The arrangement and method of the invention measure preferably the minimum standing wave ratio that can be found in the standing wave. The base station controller 118 finds and meas- ures the minimum standing wave ratios in the resonators 206 and, on the ba- sis of the minimum standing wave ratios, identifies which transceiver is com- bined to which resonator by the cable. The cables have their unique, deter- mined positions, or resonators, in the combiner. The base station controller thus identifies if a resonator has a cable connection from a wrong transceiver.

If the base station controller does not find a standing wave in a resonator at all, and thus no minimum standing wave ratio either, no transceiver has a ca- ble connection to the resonator. The base station controller can also identify a transceiver incorrectly connected from another sector. If the base station con- troller does not find, in any cavity resonator, a minimum standing wave ratio according to the frequency of a transceiver, the transceiver is not connected to any cavity resonator of the combiner in the sector at issue. In the first pre- ferred embodiment of the invention, the standing wave minimums are searched and found, and the transceivers are identified on the basis of the standing wave minimums by the combiner of each sector. The aforementioned information on the cable connections include comprehensive information on the cable connections between the combiner and the transceiver in the differ- ent sectors of the base station. The information is collecte from the combin- ers of the different sectors to the base station controller 118, which checks whether or not the cable connections conform with the logical configuration, i. e. the correct cable connections. The information on the cable connections is processed by microprocessors in the base station controller, and, as a result, potential incorrectly connected cable connections in the base station can be found.

In a second preferred embodiment of the invention shown by Figure 3, the cables 112 connecting the transceivers 110 in the sectors 102 to 106 of the base station and the combiner 108 are provided with a control wiring 302.

The second preferred embodiment of the invention is otherwise similar to the first preferred embodiment of the invention shown in Figure 2 except that in this case, the cable connections between the transceivers and the combiners are controlled by the transceivers. The transceiver transmits by the cable a signal having, for example, a constant frequency multiplie by a bit number

according to the address of the transceiver at issue. By using the control wir- ing, the transceiver receives the information on the minimum standing wave ratio from the resonator 206, preferably a cavity resonator, located in the input 114 of the combiner, which thus indicates that a cable connection to the com- biner exists. If, in the above-mentioned situation, the transceiver does not re- ceive a minimum standing wave ratio according to the transmitted frequency, no cable connection to the combiner exists. Since in this embodiment the ca- ble connections are controlled by the transceivers, the combiner 108 can be a so-called dumb unit, in other words the amount of necessary logic therein can be considerably lower than in the first preferred embodiment of the invention.

The role of the base station controller in the second preferred embodiment of the invention can be similar to that in the first preferred embodiment of the in- vention, but the cable connections are controlled by the transceivers, as de- scribed above.

The standing wave can have combiner-and resonator-specific dif- ferences, and, consequently, the signals transmitted by the transceivers to the combiner should have sufficiently different frequencies so as to ensure that the transceivers are identified correctly. In view of the above, it can be determined that in the preferred embodiments of the invention, the signals transmitted by the transceivers should have a frequency difference of at least 1 MHz between different transceivers. In the GSM, said frequency difference of 1 MHz can be determined such that it is five times an ARFN (Absolute Radio Frequency number). In the second preferred embodiment of the invention, the necessity for the above-disclosed minimum frequency difference can also be caused by the control wiring and the properties of the transceiver side.

Using the preferred embodiments of the invention, a new trans- ceiver can be connected to a fully accomplished sector of a base station quickly and reliably. The address of the new transceiver in the base station configuration is programmed to said new transceiver. Similarly, a configuration or an addition thereof also comprising the new transceiver is programmed to the base station, typically to the base station controller in the base station. Af- ter the new transceiver has been connected to the combiner, a checking pro- cedure can take place to check whether or not the new transceiver is con- nected to the combiner of its sector according to the configuration.

The base station, typically the base station controller in the base station, may carry out auto-detection, which means that at desired intervals it

can be monitored which transceivers and combiners are interconnected in the base station. Similarly, it can also be checked how the connections are ar- ranged. The auto-detection is important if, for example, a cable connection for some reason or other disappears. After the new transceiver has been con- nected to the base station, auto-detection can be used for checking whether or not the new transceiver is correctly connected to the base station, in other words according to the correct base station configuration. Also the auto- detection can be carried out by the base station controller either by the com- biners or the transceivers.

Although the invention has been described above with reference to the examples in accordance with the accompanying drawings, it is obvious that the invention is not restricted thereto but can be modified in many ways within the scope of inventive idea disclosed in the attached claims.