PROCEDURE AND SYSTEM FOR LIMITING THE POWER OF A MOBILE STATION

Abstract: In the future, stricter standards regarding the microwave radiation emitted by mobile telephones will be applied. Therefore, in the worst case, the transmission power of mobile telephone systems will have to be reduced, which will affect the quality of service. However, it would be unreasonable to reduce the transmission power of all mobile stations. Therefore, the object of the invention is to create e.g. in the GSM system a property that allows a mobile station to be used at a power level consistent with the safety standards. The invention makes it possible to distinguish between different mobile stations e.g. on the basis of their IMSI and/or IMEI codes. According to the invention, data substantially relating to the transmission power of the mobile station are stored in the mobile communication network separately for each mobile station; device data identifying the mobile station are received in the mobile communication network in conjunction with call setup; the transmission power data for the mobile station are checked and the transmission power of the mobile station is controlled on the basis of a predetermined power control algorithm and the device data for the mobile station.

Description: PROCEDURE AND SYSTEM FOR LIMITING THE POWER OF A MOBILE STATION The present invention relates to a procedure as defined in the preamble of claim 1 for limiting the power of a mobile station. Furthermore, the invention relates to a system as defined in the preamble of claim 9 for limiting the power of a mobile station. At present, the effects of mobile telephones on health are being widely investigated. A special concern is that the microwave radiation emitted by a mobile telephone might be a risk to human health, especially to the human brain. Therefore, stricter standards regarding the microwave radiation and transmission power of mobile telephones are likely to be applied in the future. Telephone manufacturers will have to develop aerial solutions that meet the new standards. As for existing telephones which have been in use for several years, problems will arise. At worst, the power of mobile telephone systems will have to be reduced. However, it seems likely that, especially in GSM (Global System for Mobile Communications) based systems, even with the present power levels, there will be terminals above and below the health standards. It would be unreasonable to reduce the transmission power of all mobile telephones, at the same time impairing the quality of service for all terminals. Thus, the problem is that with current technology it is impossible to taken into account the differences between mobile telephones, which means that a power limit would reduce the operating range of all mobile telephones. Furthermore, to maintain the present service area, the operators would have to make increasing investments in the radio network to be able to maintain the present level of service. The object of the present invention is to eliminate the drawbacks described above A specific object of the present invention is to disclose a procedure and a system in which the transmission power to be used can be limited separately for each terminal device. A further object of the invention is to create a system in which both existing mobile telephones and mobile telephones of a new type can be used without significantly impairing the quality of service. As for the features characteristic of the invention, reference is made to the claims. In the procedure of the invention for controlling the power of a mobile station in a data communication system comprising a mobile communication network, such as a GSM or NMT network, the power of the radio signal fed to the aerial or equivalent of a mobile station is reduced to minimise the unwholesome effects of the microwave radiation generated by the radio signal. The GSM network preferably comprises a home location register (HLR, Home Location Register) , which contains customer-specific basic data, such as the right of access and the functions available to the subscriber. Moreover, the mobile communication network comprises a visitor location register (VLR, Visitor Location Register) , to which the mobile station or subscriber reports on entering the area of a given mobile services switching centre. On receiving the report, the mobile services switching centre retrieves the subscriber and mobile station specific information from the home location register and sends it to the visitor location register of its own area and at the same time updates the location data for the subscriber. According to the invention, data substantially relating to the transmission power of the mobile station are stored in the mobile communication network separately for each mobile station, the device data for the mobile station are received in the mobile communication network in conjunction with call setup, the transmission power data for the mobile station are checked and the transmission power of the mobile station is controlled on the basis of a predetermined power control algorithm and the device data for the mobile station. The mobile station can preferably be identified by an IMEI code (IMEI, International Mobile Station Equipment Identity) or an IMSI code (IMSI, International Mould Subscriber Identity) . In this case, however, each IMEI and/or IMSI code can be associated with data relating to the terminal device in question, such as a power level consistent with the safety standards. In a preferred embodiment of the present invention, the transmission power data stored for the mobile station includes a maximum allowed transmission power of the mobile station. On the other hand, it is also possible store a maximum allowed value of a time integral of the transmission power of the mobile station. The transmission power data stored may also include power levels that differ from the power levels in the network as a whole. In some situations it may also be necessary to define a minimum power level, in which case, when the power level for the whole network is reduced, the power of terminal devices with a minimum power level defined will remain unchanged. Such terminals could include devices operated without a human user near them, e.g. terminal devices installed in conjunction with certain machines or appliances . The transmission power data can preferably be stored in the HLR register and/or in a MSC/VLR element (MSC, Mobile Services Switching Centre) of the mobile communication network. In a preferred embodiment of the present invention, the maximum and/or the mean value of the transmission power of the mobile station is/are monitored in a given period of time, the monitored value is compared with a predetermined limit or threshold value and, if the limit is exceeded, the call is disconnected. On the other hand, the mobile station can be switched to a lower power level, especially in an NMT network, even if no actual power regulation is used. This makes it possible to limit the amount of unwholesome radiation emitted by the mobile station. As compared with prior art, the present invention has the advantage that the invention allows a mobile communication network, such as a GSM network, to be adapted to a reduction of transmission power levels that may be required in the future because of stricter health standards for RF transmissions. Further, the invention allows parallel use in the same mobile communication network of both new terminals consistent with the standards and existing terminals of the present generation that may exceed the future health standards. A further advantage of the invention as compared with prior art is that the invention provides a handy way of limiting the power levels by limiting the level of transmission power of only those mobile stations for which a limitation is necessary. Furthermore, the invention makes it possible for operators to use the existing wireless network even in the future while still offering the users the present level of service. The system of the invention for controlling the transmission power of a mobile station in a mobile communication system comprises a mobile communication network. The system is used to regulate the power of the radio signal fed into the aerial or equivalent of the mobile station to minimise unwholesome effects and it comprises storage means for storing in the mobile communication network mobile station-specific transmission power data substantially relating to trans- mission power, a receiver in the mobile communication network for receiving device data identifying the mobile station in conjunction with call setup, means for checking the transmission power data for the mobile station and controlling the transmission power of the mobile station on the basis of a predetermined power control algorithm and the device data for the mobile station. The above-mentioned means can be implemented using appropriate components in the telecommunication network. In a preferred embodiment of the present invention, the transmission power data stored for the mobile station includes a maximum allowed transmission power (P out(max) ), a minimum transmission power (P ou ( m i n )) to be used and/or a desired constant power (P 0ut ( con )) • Thus, the operator can set the transmission power to a desired level separately for each mobile station. In the following, the invention will be described in detail by the aid of a few examples of its preferred embodiments by referring to the attached drawing, in which Fig. 1 presents a diagram representing a system according to the present invention; and Fig. 2 presents two graphs drawn on a power/time co-ordinate system. The system presented in Fig. 1 comprises a mobile communication network, a GSM network, and a register connected to it, which may be a HLR or VLR register and which may be located in any component of the GSM network. Further, the GSM network is provided with a power regulation algorithm, which is used to determine the magnitude of the transmission power I? output of the mobile station. In addition, Fig. 1 shows β a mobile station 1 with a radio signal, represented by a line with an arrowhead, transmitted from its aerial at a power level of P output ' which may be of a level detrimental to health. Furthermore, Fig. 1 shows a so- called radio interface, over which the mobile station 1 communicates with the GSM network. Although in Fig. 1 both the register and the power regulation unit are depicted as separate components, it is obvious that they can be integrated in the normal manner in the mobile communication network. Let it be further stated that the procedure of the invention is used to control the transmission power in the so-called uplink channel, i.e. the power of the signal transmitted from the mobile station to the base station. Fig. 2 shows two graphs, the first one I of which and the associated broken line form a coherent whole and the second one II and the associated area shaded with broken lines form another coherent whole. In the first case, the horizontal broken line represents the P output (max) value of the uplink channel, which is a predetermined threshold value for the output power of a mobile station. As is clearly visible from the Figure, the maximum output power is exceeded four times. In this case, the output power value can be limited e.g. in steps of 2 dBm or the call can even be disconnected. The power is monitored by measuring the transmission power P outPut °f tπe mobile station. When the power exceeds or is close to the predetermined limit, a control command is sent to the mobile station, causing the mobile station to reduce its transmission power in the uplink channel. The horizontal broken line could also represent a minimum value that the transmission power of the mobile station must reach. In the latter case II, the figure presents another power graph, illustrating the variation in the transmission power of the mobile station in another case. Further, the figure shows an area shaded with broken lines, representing a time integral calculated for the time interval t - t 2 with respect to power. The integral obtained is again compared with a predetermined value P outpu (ave) , and if it is established that the limit value is exceeded, then a power control command is sent to the mobile station, causing the mobile station either to stop transmitting, i.e. to disconnect the call, or to reduce its transmission power in the uplink direction. In summary, referring to Fig. 1 and 2, a preferred example of power control is presented. When the mobile station starts a new call or when the mobile communication network is setting up a new call to the mobile station, i.e. generally in conjunction with call setup, the mobile station sends to the mobile communication network e.g. its IMEI or IMSI code, which is stored by the mobile communication network as data identifying the mobile station. During the call, based on the code received, the transmission power data for the mobile station, i.e. data indicating whether the transmission power of the mobile station has to be separately controlled or whether the mobile station is a new-generation device with built-in regulation of transmission power in accordance with safety standards, is retrieved from the HLR or VLR register. The transmission power data obtained is used as input to a power regulation algorithm, which monitors the transmission power P output of the mobile station and, based on this monitoring, controls the transmission power of the mobile station by means of transmission power commands given over the radio interface. The invention is not restricted to the examples of its embodiments described above, but many variations are possible within the scope of the inventive idea defined by the claims.

Claims: CLAIMS 1. Procedure for controlling the power of a mobile station in a mobile communication system comprising a mobile communication network, in which procedure the power of the radio signal fed into the aerial or equivalent of the mobile station is regulated to minimise unwholesome effects, c h a r a c t e r i z e d in that data substantially relating to the transmission power of the mobile station are stored in the mobile communication network separately for each mobile station; device data identifying the mobile station are received in the mobile communication network in conjunction with call setup; the transmission power data for the mobile station are checked and the transmission power of the mobile station is controlled on the basis of a predetermined power control algorithm and the device data for the mobile station. 2. Procedure as defined in claim 1, c h a r a c t e r i z e d in that the mobile station is identified on the basis of an IMEI device code and/or an IMSI code. 3. Procedure as defined in claim 1 or 2 , c h a r a c t e r i z e d in that the transmission power data stored for the mobile station include a maximum allowed transmission power (P outp t ( max ) ) a minimum transmission power (P output ( m i n ) ) to ^ e used and/or a desired constant power (P 0utput ( con ) ) °f the mobile station. 4. Procedure as defined in claim 1 or 2 , c h a r a c t e r i z e d in that the transmission power data stored for the mobile station include the highest allowed mean transmission power value in a given time. 5. Procedure as defined in any one of claims 1 - 4, c h a r a c t e r i z e d in that the transmission power data are stored in a HLR, VLR or MSC element of the mobile communication network. 6. Procedure as defined in any one of claims 1 - 5, c ha r a c t e r i z e d in that the maximum and/or the mean value of the transmission power of the mobile station is/are monitored in a given period of time, said values are compared with a predetermined limit value and, if the limit is exceeded, the call is disconnected. 7. Procedure as defined in any one of claims 1 - 6, c h a r a c t e r i z e d in that the mobile communication network is a GSM network. 8. Procedure as defined in any one of claims 1 - 6, c h a r a c t e r i z e d in that the mobile communication network is an NMT network. 9. System for controlling the transmission power of a mobile station in a mobile communication system comprising a mobile communication network, said system being used to regulate the power of the radio signal fed to the aerial or equivalent of the mobile station (1) to minimise unwholesome effects, c h a r a c t e r i z e d in that the system comprises: storage means (2) for storing in the mobile communication network mobile station specific transmission power data substantially relating to transmission power; a receiver (3) in the mobile communication network for receiving device data identifying the mobile station in conjunction with call setup; means (4) for checking the transmission power data for the mobile station and controlling the transmission power of the mobile station on the basis of a predetermined power control algorithm and the device data for the mobile station. 10. System as defined in claim 9, c h a r a c t e r i z e d in that the mobile station is identified by means of an IMEI device code and/or an IMSI code. 11. System as defined in claim 9 or 10, c h a r a c t e r i z e d in that the transmission power data stored for the mobile station comprise a maximum allowed transmission power (P 0ut ( max )) > a minimum transmission power (P 0ut ( m i n )) to t> e used and/or a desired constant power (P out ( con )) °f ne mobile station. 12. System as defined in claim 9 or 10, c h a r a c t e r i z e d in that the transmission power data stored for the mobile station comprise a highest and/or lowest allowed mean value of transmission power in a given time. 13. System as defined in any one of the preceding claims 9 - 12, c ha ra c t e r i z e d in that the storage means are located in a HLR, VLR or MSC element of the mobile communication network. 14. System as defined in any one of claims 9 13, c h a r a c t e r i z e d in that the maximum and/or the mean value of the transmission power of the mobile station is/are monitored in a given period of time, said values are compared with a predetermined limit value and, if the limit is exceeded, the call is disconnected.

Inventors: HOKKANEN TUOMO, HOKKANEN, TUOMO
Applicants: FINLAND TELECOM OY, HOKKANEN TUOMO, HOKKANEN, TUOMO, TELECOM FINLAND OY
Application year: 1998
Main classification: H04B7
IPC codes: H04B7