MXPA00009512A - Method and arrangement for determining the presence of a mobile station in a determined area - Google Patents

Abstract

The present invention is related to a method and arrangement in a radio communication system (SYS1) for determining the presence of a mobile station (MS1) in a determined area (101). A first radio channel (DTC1) is allocated for communication of control information and user data information between the mobile station (MS1) and a first base station (BS1). The mobile station (MS1) transmits identity information (ID1) repeatedly on the first radio channel (DTC1). A detecting unit (HBS1) receives at least one occurrence of the transmitted identity (ID1) information. The mobile station (MS1) is registered as present in the vicinity of the detecting unit (HBS1) upon receipt of said at least one occurrence of the identity information (ID1).

Description

METHOD AND ARRANGEMENT TO DETERMINE THE PRESENCE OF A MOBILE STATION IN THE CERTAIN AREA TECHNICAL FIELD OF THE INVENTION The invention relates to a method and an arrangement in a radiocommunication system in which a mobile station is operating. More specifically, the invention relates to a method and arrangement for determining whether the mobile station is present in a specific area.

DESCRIPTION OF RELATED TECHNIQUE A problem that arises at least in connection with mobile stations operating in a radiocommunication system is to determine whether a certain mobile station is present in a specific area. An exemplary scenario where this problem occurs is where a domestic base station, that is, a private base station that can be connected to the public telephony network, is installed in the home of a public cellular network subscriber and the subscriber, using its mobile station, prefers to communicate through the residence base station while it is in the home and within the radio coverage area of the residence base station instead of the cellular network. GB 2 282 735 describes a communication system in which a user carries a portable device that communicates through a residence base station connected to a telephone network or a cellular network when it is far from the residence base station. In addition to the ease of transmitting data and analog signals for purposes of call connection, identification and traffic in its cellular mode, the portable device also transmits narrowband signals of low power that identify the user. When the user approaches the home base station, the identity signals are received by the residence base station and a switch is operated to a second mode of operation in which incoming calls for the user are routed through the network telephone and the residence base station. A handset or portable telephone which, in accordance with GB 2 282 735, transmits a low power identification signal in addition to transmitting signals related to the call needs to be equipped with at least two transmitters that increase the complexity and cost of the handset. In addition, GB 2 282 735 describes how incoming calls are routed by the telephone network and the residence base station after a change to the second mode of operation. There is no description related to transferring an established call in the cellular network to the residence base station.

U.S. Patent No. 5,260,988 discloses a wireless, cellular, portable dual-mode radiotelephone that can operate in a wireless telephone system or a cellular network. The radiotelephone preferably selects the wireless system when it is in range of this system. When the radiotelephone is operating in the idle mode, that is, switched on but without an established call, in the cellular network, the radiotelephone monitors a first control channel transmitted by a base station belonging to the cellular network. The radiotelephone temporarily interrupts the supervision of the first control channel for a certain period. During this time, the radiotelephone scans the radio signals from the wireless system. If the wireless system is found, the radiotelephone moves to the wireless system, otherwise it restarts the supervision of the first control channel. US 5,260,988 also describes the transfer of an established call from the cellular system to the wireless system. However, US 5,260,988 also does not describe what drives the radiotelephone to process and change the wireless system, nor how the radiotelephone can maintain the established call while sweeping for radio signals from the wireless system.

COMPENDIUM OF THE INVENTION The general problem addressed by the present invention is to detect whether a specific mobile station is present in a certain area. The problem is solved mainly by means of a method in which the mobile station transmits information identifying the mobile station in a radio channel assigned for communication between the mobile station and a first base station. When a detection unit receives the identity information transmitted, the mobile station is recorded as present in a certain area. The solution includes the means necessary to carry out the method in the radiocommunication system. More specifically, the problem is solved in the following way. A first radio channel is assigned for communication of control information and information of the user data between the mobile station and the first base station. The mobile station transmits the identity information repeatedly over the first radio channel. The detection unit receives at least one occurrence of the identity information transmitted. The mobile station is recorded as present in the vicinity of the detection unit upon receipt of at least one occurrence of the identity information. A general objective of the present invention is to provide a method and an arrangement that allows a detection unit to detect whether a specific mobile station is present in the vicinity of the unit. A more specific objective of the invention is to provide the method of detecting the presence of the mobile station and the arrangement that does not require the mobile station to include more than one transmitter. Still another objective is to provide a transfer method and arrangement wherein the transfer of the mobile station from the first base station to the second base station is triggered when, using the presence detection method of the mobile station, the mobile station is detected as present within the coverage area of the second base station. An advantage offered by the invention is that it provides a method for detecting the presence of the mobile station and the arrangement that does not require the mobile station to include more than one transmitter. Another advantage is that the invention allows a selective transfer method and the arrangement wherein the decision to drive the transfer of a selected mobile station, communicating with a first base station in a first radio communication network, to a second, separate base station of the first radio communication network, is transparent for the mobile station and the first radio communication [sic].

Now the invention will be described in greater detail with reference to the exemplary embodiments thereof and also with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a view of a first radio communication system comprising a residence base station. Figure 2A is a flowchart illustrating a method of detecting the presence of a mobile station according to an embodiment of the present invention. Figure 2B is a flow chart illustrating a transfer method comprising the method of detecting the presence of a mobile station illustrated in Figure 2A. Figure 3 is a block diagram illustrating the structure of the transmitted identity messages. Figure 4 is a block diagram illustrating an embodiment of a mobile station according to the present invention. Figure 5 is a block diagram illustrating a residence base station. Figure 6 is a view illustrating a second radio communication system comprising a wireless office system.

Figure 7 is a view illustrating a third radiocommunications system comprising a residence presence detector. Figure 8 is a view illustrating a fourth radiocommunication system comprising a cellular network. Figure 9 is a block diagram illustrating the structure of a digital traffic channel.

DETAILED DESCRIPTION OF THE MODALITIES Figure 1 illustrates part of a radiocommunication system according to a first exemplary embodiment of the invention. The radio system SYS1 comprises a public cellular network PLMN1 and a public telephone network PSTN1. The cellular network PLMN 1 comprises a mobile services switching center MSC1 to which a first base station BSl is connected. The radio system SYS1 further comprises a residence base station HBS1. In this exemplary embodiment, the home base station HBSl is installed in the home of a cellular network subscriber. The residence base station HBSl is connected to a local LEI exchange in the public telephone network PSTN1. The telephone network PSTN1 and the cellular network PLMN1 are interconnected with each other and allow communication, for example, telephone calls, between subscribers operating in the respective network. The radio system SYS1 further comprises a mobile station MSI that allows the subscriber of the cellular network to communicate, for example, by initiating and receiving telephone calls. The home base station HBSl, which may otherwise be known as the personal base station, offers radio coverage within a certain area 101 at the residence location of the cellular subscribers. The residence base station HBSl and the first base station BSl in Figure 1 both support the same radio interface, which simplifies the design of the mobile station MSI. In this exemplary mode, the radio interface is used according to the specifications of TIA / EI IS-136. Although the cellular subscriber uses his mobile station MSI within the coverage area 101 of the home base station HBSl, the preferred communication must be handled through the home base station HBSl over the PSTN1 telephone network instead of over the network PLMN1 cell phone Therefore, the radio system SYS1 must be able to detect the presence of the mobile station MSI within the coverage area 101 of the residence base station HBS1. The present invention deals with this problem of presence detection. Figure 2A is a flow chart illustrating a method according to the invention for detecting when the mobile station MSI is present in the vicinity, i.e., within the radio coverage area 101, of the residence base station HBS1. In step 201 of Figure 2A, a dedicated first digital traffic channel (DTC) is assigned for communication between the mobile station MSI and the first base station BS1. The mobile station MSI, the first base station BS1 and the mobile services switching center MSC1 interact in a well-known manner when the channel assignment is made. Channel allocation may occur due to a telephone call to or from a second party being received or initiated by the mobile station MSI while operating in the area (cell) served by the first base station BS1. The channel assignment may also be due to a transfer of an already established call. The digital traffic channel DTCl is a bidirectional channel. In a downlink direction, i.e., from the first base station BSl to the mobile station MSI, the channel is referred to as a digital forward traffic (FDTC) channel and in the uplink direction, i.e., from the station mobile MSI to the first base station BSl, the channel is called a reverse digital traffic channel (RDTC). The digital traffic channel DTCl is used to transfer information of the user's data, such as voice or facsimile, and control information, that is, signaling information. The digital traffic channel comprises a portion called a slow associated control channel (SACCH) SACCH1. The associated slow control channel SACCH1 is used in the uplink direction to transfer channel quality messages (CQM) reporting the results of the measurements made by the mobile station MSI in the assigned digital traffic channel DTCl as well as the measurements made on the signals of other base stations in the PLMNl cellular network. Figure 9 illustrates the structure of a digital traffic channel in accordance with TIA / EIA IS-136 specifications. A TDMA frame 901 contains six time slots 902 in which two slots are assigned to each digital traffic channel. In a time slot for the uplink address, a burst 903 containing a number of fields is transmitted. The burst 903 contains three data fields 904, a sync field 905, a field of the associated slow control channel 906 and a field of the digital code color coded 907. The data fields 904 is used to convey information of the data of the user while the field of the associated slow control channel 906 is used to carry the messages of the associated slow control channel. For the transmission of each slow associated control channel message, a number of bursts 903 are used. In step 202 of Figure 2A, the mobile station MSI begins to transmit information repeatedly by identifying itself in the associated control channel portion. slow SACCH1 of the first digital traffic channel DTCl. Identity information is sent in identity messages ID1 that are inserted into the message flow in the associated slow control channel SACCH1 at a predetermined rate, for example, once every 10 seconds. In step 203, the home base station HBSl receives at least one occurrence of the identity messages transmitted by the mobile station MSI. The home base station HBSl scans the radio transmissions belonging to the first digital traffic channel DCT1 assigned in the radio frequency band used for the reverse digital traffic channels in the cellular network PLMN1. Each time the home base station HBSl detects a reverse digital traffic channel, it monitors this channel until it has correctly received and decoded at least one identity message or has monitored the channel long enough to conclude that identity messages are not transmitted in this channel. When an identity message has been received, the home base station HBSl compares the contents of this message with previously stored identity information identifying the mobile station MSI as attached to the home base station HBSl. If the received identity does not match the stored identity, the home base station HBSl continues the sweep for the first assigned digital traffic channel DTCl. If the received identity matches the stored identity, the home base station HBSl registers, in step 204, the mobile station MSI as present in the vicinity of the residence base station HBS1. Figure 3 is a block diagram illustrating the structure of the transmitted identity messages. Like the other TIA / EIA IS-136 messages transmitted in the associated slow control channel, the identity message 300 contains a 2-bit protocol discriminator field 301 and a field of the 8-bit message type 302. 'identity message ~ 300 also contains an identity field 303. The identity field 303 illustrated in the Figure 3 consists of 30 bits. The home base station HBSl generates a 30 bit random identity which is stored in the home base station HBSl and the mobile station MSI. As one skilled in the art will recognize, there are some other ways of selecting the identity information used in the context of the present invention. Other examples include, but are not limited to, the mobile station's identity number (MIN), the identity of the international mobile subscriber (IMSI) or the identity of the equipment of the international mobile station (IMEI). In the method of detecting the presence of the mobile station just described, the home base station HBS1 functions as a detector of the presence of the mobile station. Otherwise, the residence base station HBSl can be considered as consisting of a detector of the presence of the mobile station. The flow chart of Figure 2B illustrates a transfer method according to the invention performed in the radio system SYS1 of Figure 1. The mobile station MSI is transferred from the first home base station HBSl in the cellular network PLMN1 to the home base station HBSl when the mobile station MSI is within the radio coverage area 101 of the residence base station HBS1. In this automatic transfer method, the presence of the mobile station MSI within the radio coverage area 101 of the residence base station HBSl is detected according to the method of the invention described above, ie the automatic transfer method it is started by performing the steps of method 201-204 that are illustrated in Figure 2A. Step 204, where the received identity is determined as corresponding to the identity stored in the home base station HBSl, also implies that the mobile station MSI is determined as a mobile station that preferably must communicate with the home base station HBSl when it is within the scope of the HBS1 residence base station. In this exemplary embodiment only the mobile station MSI is linked to the home base station HBSl, but in other embodiments there are some mobile stations linked to a home base station HBSl forming a series of mobile stations that preferably must communicate with the base station of residence when it is within the scope of the residence base station. In step 205, the automatic transfer is performed from the mobile station MSI from the first digital traffic channel DTCl to the second digital traffic channel DTC2 for communication of the control information and information of the user data between the base station of residence HBSl and the mobile station MSI. The automatic transfer is made as follows. The home base station HBSl initiates a dial-up modem connection via the PSTN1 telephone network to a server of the residence base station within the mobile services switching center MSCl. The residence base server acts as an interface allowing the interaction between the residence base station HBSl and the mobile services switching center MSCl. In the modem connection with manual dialing, the residence base station HBSl sends a request to the mobile services switching center MSCl for automatic transfer to the second digital traffic channel DTC2 in the radio frequency which had previously been assigned for use within the station HBS1 residence base. The assignment of the radio frequency for the home base station HBSl can, for example, be performed as described in U.S. Patent No. 5,428,668. The mobile services switching center MSCL confirms the request that activates the home base station HBSl to start the transmission in the second traffic channel, digital DTC2. The mobile services switching center MSC1 commands the first base station BS1 to transmit an automatic transfer command to the mobile station MSI, ordering the mobile station MSI to tune the second digital traffic channel DTC2. The mobile station MSI tunes to the second digital traffic channel DTC2 and continues to transmit and receive information of the user data and control information in this digital traffic channel DTC2. When the residence base station HBSl detects the mobile station MSI in the second digital traffic channel DTC2, it informs the mobile services switching center MSCl that the automatic transfer was successful. The mobile services switching center MSCl combines the connection from the second part and the connection with the home base station HBSl, and the continued conversation between the subscriber of the cellular network and the second part is carried out by this combined connection. The mobile services switching center orders the first base station BSl to release the first digital traffic channel (DTCl). The mobile services switching center MSC1 can indicate in the response to the automatic transfer request from the home base station HBSl that instead of the radio frequency proposed by the home base station HBSl, another frequency must be used for the second home channel. digital traffic DTC2. The residence base station EBS \, the mobile services switching center MSC1, the first base station BSl and the mobile station MSI interact with each other when they perform the automatic transfer as already described and can thus collectively be considered as a means for the automatic transfer of the mobile station MSI to the second digital traffic channel TDC2. Figure 4 illustrates a schematic block diagram of the mobile station MSI. The blocks that are needed only when operating in the analog traffic channel have not been included in Figure 4. The mobile station MSI contains a microphone 401 and a hearing aid 402 connected to a speech processor 403. The speech processor 403 performs conversion analog to digital and digital to analog as well as voice coding and decoding. The speech processor 403 is connected to a channel codee 404. The channel codee 404 performs channel coding and channel decoding as well as interleaving and deinterleaving. The channel codee 404 is connected to a transceiver 405 consisting of a radio transmitter and a radio receiver. The transceiver 405 is connected to an antenna 406. A control processor 407 is responsible for the total control of the mobile station MSI and is thus connected to and controls the speech processor 403, the channel codee 404 and the transceiver 405. A unit of storage 408 provides storage of program instructions for execution by control processor 407 as well as data used when program instructions are executed. As illustrated in Figure 1, when the mobile station MSI communicates with the first base station BS1 on the first digital traffic channel DTC1, the control processor 407 provides the channel codee with a flow of messages to be transmitted on the channel of associated control slow SACCH1. In this message flow, the control processor 407 inserts identity information messages ID1 according to the format illustrated in Figure 3. The identity of the mobile station is kept in the storage unit 408 which is updated each time that the mobile station MSI is loaded by the residence base station HBS1. The control processor 407, the codec of the channel 404 and the transceiver 405 can be collectively considered as a transmission medium for the repeated transmission of the ID1 identity messages, i.e. information identified by the mobile station MSI, in the first DTCl digital traffic channel assigned. In addition to the provisions described above for transmitting identity messages, the mobile station MSI is similar to other mobile server or flexible TIA / EIA IS-136 stations well known to those skilled in the art. Figure 5 illustrates a schematic block diagram of the residence base station HBS1. The home base station HBSl consists of an antenna 501 to which a transceiver 502 is connected, consisting of a radio receiver and a radio transmitter. A channel codec 503 is connected to the transceiver 502 and in turn is connected to a voice processor 504. The channel codec 503 and the speech processor 504 perform similar functions as the codec of the channel 404 and the speech processor 403 in the mobile station MSI illustrated in Figure 4. The voice processor 504 is connected to a PSTN 505 interface comprising a modem 506. The PSTN 505 interface is used to connect the HBSl residence base station to the telephone network PSTNl in Figure 1 and provides the functions that allow the residence base station HBSl to interact with the telephone network PSTNl and the mobile services switching center MSCl in the cellular network PLMN1. A control processor 507 is responsible for the total control of the residence base station HBSl and is connected to and controls the other units 502-506. A storage unit 508 provides storage of the program instructions for execution by the control processor 507 as well as the data used when the program instructions are executed. The residence base station HBSl also comprises a battery charger 509 connected to an electrical connector 509 [sic]. The control processor 507 is also connected to the electrical connector 510. When the mobile station MSI of Figure 1 is connected to the electrical connector 509 [sic], the battery charger 509 loads the mobile station MSI. Further details on the aspects of the HBS1 residence base station described so far can be found in U.S. Patent No. 5,428,668. The base station is described more specifically with reference to Figures 2-3 of this specification. These common aspects will not be elaborated in this description. Each time that the mobile station MSI of Figure 1 is connected to the electrical connector 510, the control processor 508 generates a new 30-bit random identity and transfers this identity to the mobile station MSI through the electrical connector 510. The new 30-bit random identity is stored in the mobile station MSI as well as the storage unit 508 and replaces any of the previously stored random identities. In addition to the units illustrated in Figure 4 and discussed in the foregoing, the residence base station HBSl also contains a sweep receiver 511 connected to the antenna 501 and a channel decoder 512. Both the sweep receiver 511 as the channel decoder 512 are connected to and controlled by the control processor 507. When the method 203 is performed in FIGS. 2A and 2B, the control processor 507 determines a series of frequencies where radio transmissions potentially belonging to the assigned traffic channel DTCl of Figure 1. This series of frequencies can, for example, include all frequencies potentially used in the SYS1 radio system for reverse digital traffic channels. The control processor 507 then commands the sweep receiver 511 to tune one of these frequencies in turn. The sweep receiver 511 measures the intensity of the received signal. If this signal strength is above a defined threshold, the control processor 507 instructs the decoder of the channel 512 to perform decoding and de-interleaving of the channel at the output of the sweep receiver 511. The control processor 507 analyzes the output of the decoder of channel 512. If the control processor 507 determines that it has not found the reverse digital traffic channel with a signal strength above the defined threshold, the control processor 507 commands the scan receiver 5.11 to tune to the next frequency in the frequency series. If a reverse digital traffic channel has been found, the control processor 507 continues to monitor the output data from the decoder of channel 512 until it determines that an identity message has been received or the digital traffic channel is monitored. current inverse for a sufficient time to ensure that identity messages are not transmitted on this channel. If no identity message was found, the control processor 507 instructs the sweep receiver 511 to tune to the next frequency in the series of frequencies. If an identity message was found, the control processor 507 compares the content of the received identity message with the random identity previously stored in the storage unit 508. If the received identity does not match the stored identity, the control processor 5Q7 commands the sweep receiver 511 to tune to the next frequency in the series of frequencies. If the received identity matches the stored identity, the control processor 507 concludes that the mobile station MSI attached to the home base station HBSl is within the radio coverage area 101 of the home base station HBS1. When the control processor 507 has detected the mobile station MSI within the radio coverage area 101 of the home base station HBSl, the home base station HBSl proceeds to activate an automatic transfer of the mobile station MSI as already described in step 205 of the method in Figure 2B. During the automatic transfer process, the control processor 507 exchanges signaling information with the mobile services switching center MSC1 through the modem 506. Instead of having a separate channel decoder 512 connected to the sweeping receiver 511, the codec of the channel 503 can be adapted to perform decoding and de-interleaving of the channel likewise for the output of the sweep receiver 511. The control processor 507, the sweep receiver 511 and the channel decoder 512 can be collectively considered as a means receiver to receive identity information transmitted by the mobile station M: YES. The control processor 507 can be considered as a registration means to register the mobile station MSI as present in the vicinity of the residence base station HBSl with the reception of the identity information transmitted by the mobile station MSI. The control processor 507 can also be considered as a means to determine that the mobile station MSI is linked to the home base station HBSl and thus preferably should be communicated through the home base station HBSl instead of the first base station BSl. In addition to the exemplary embodiment of the invention described above, there are several other possible embodiments of the current invention. Instead of repeatedly transmitting the identity information of the mobile station over a slow associated control channel, this information can be transmitted over a fast associated control channel (FACCH).

As will be appreciated by a person skilled in the art, a residence base station may be conne to another type of public wired network different from the public telephone network as illustrated in Figure 1. An alternative network would be an Integrated Digital Services Network (ISDN). Digital Network of integrated services) . The network to which the home base station conne can use a mode oriented to the information transfer connection, for example using circuit switched connections or ATM virtual channels, or an information transfer mode without connections, for example, using the User Datagram Protocol (UDP, User Datagram Protocol). There are some other possible applications for the method of detecting the presence of a mobile station of the inventive different means of activating automatic transfer to a residence base station. An alternative application would be to use the method of detecting the presence of the mobile station to activate the automatic transfer of the mobile stations, together with a wireless office system, from a public cellular network to the wireless office system. In Figure 6, a radio system SYS4 is illustrated comprising the cellular network PLMN1 of Figure 1, a mobile station MS3 and a wireless office system W0S1 consisting of a private automatic switch (PABX) PABX1 to which different base stations are conne 0BS1-0BS4. The PABX PABX1 is conne to the mobile services switching center MSC1 via the main line 601. In this exemplary embodiment of the invention, a similar automatic transfer method as the automatic transfer method illustrated in Figure 2B is used for the automatic transfer of the mobile stations linked to the wireless office system WOS1, from the cellular network PLMN1 to the wireless office system WOSl as soon as they are within the coverage of any of the base stations OBS1-OBS4 belonging to the wireless office system . In Figure 6, the mobile station MS3, which is initially communicating with the first base station BS1 in the cellular network PLMN1 and transmitting ID4 identity messages over a portion of the associated slow control channel SACCH4 of a first digital traffic channel DTC4, it is automatically transferred to a second digital traffic channel DTC5 for communication with a second base station OBS1 belonging to the wireless office system WOSl. In this exemplary embodiment of the invention, each base station OBS1-OBS4 belonging to the wireless office system W0S1 is provided with a list of identities of the mobile stations linked to the wireless office system W0S1 of the PABX PABX1 which handles a master copy of this list of mobile stations linked. The base stations 0BS1 scavenge for the mobile stations linked to the wireless system W0S1 which are communicating with the base stations in the cellular network PLMN1. When a united mobile station, using the detection method of the presence of the invention, it is detected within the coverage area of one of the base stations 0BS1-0BS4, the base station informs the PABX PABX1 of this fact. The PABX PABX1 sends an automatic transfer request to the mobile services switching center MSC1 and the automatic transfer is performed in a similar manner as described above. However, note that the signaling exchange and the continuous communication of the user's data information is done by the main line 601 interconnected by the PABX PABX1 and the mobile services switching center MSC1 instead of by a dial-up connection . The mobile station MS3 functions mainly as the mobile station MSI illustrated in Figure 4. The mobile station MS3 in this example, however, receives a random identity of 30 bits each time it is registered with the wireless office system WOSl. The PABX PABX1 with the detection that the mobile station MS3 has introduced to the service area of the wireless office system W0S1, generates the random identity, sends this new identity in an identity message (see Figure 3) to the mobile station MS3 at through the base station that detected the mobile station MS3, updates the master copy of the list of mobile stations joined with this new random identity and distributes this new identity also to its joined base stations 0BS1-0BS4. Another application would be to use the method of detecting the presence of the mobile station, not to activate the automatic transfer, but instead to verify the presence of a certain mobile station within a candidate cell of automatic transfer. Such an application is illustrated in Figure 7. Figure 7 shows a radio system SYS2 consisting of a cellular network PLMN2 together with a mobile station MS2. The cellular network PLMN2 is illustrated as comprising a mobile services switching center MSC2 to which a first base station BS1 and a second base station BS2 are connected. A first digital traffic channel DTC3 is assigned dedicated for communication between the mobile station MS2 and the first base station BS1. The mobile station MS2 repeatedly transmits the identity messages ID2 containing information identifying the mobile station MS2 on a portion of the slow associated control channel SACCH2 of the first digital traffic channel DTC3. In this alternative application of the invention, the transmitted identity information is selected as a Temporary Mobile Station Identity (TMSI, Temporary Identity of the Mobile Station) which is dynamically assigned by the cellular network PLMN2 to the mobile station MS2. The mobile station MS2 performs measurements on the first digital traffic channel DTC3 and on the radio signals from other base stations, including the second base station BS2 and reports the results of these measurements to the first base station BS1. As the mobile station MS2 approaches the second base station BS2, the signal strength of the first digital traffic channel DTC3 decreases while the signal strength of the signals coming from the second base station BS2 increases. The first base station BSl evaluates the reported results from the mobile station as well as the results of its own measurements on the first digital traffic channel DTC3. When an automatic transfer activation criterion is met, the first base station BSl sends a request message of the automatic transfer to the mobile services switching center MSC2, identifying the second base station BS2 as the primary target for an automatic transfer . The mobile services switching center MSC2 sends a verification request message to the second base station BS2 ordering the second base station BS2 to verify that the second base station BS2 can receive the transmissions from the mobile station MS2 on the uplink of the first DTC3 digital traffic channel. In the prior art it is known that this verification is performed by tuning the uplink portion of the first digital traffic channel DTC3, that is, to the time slot and frequency over which the mobile station MS2 is transmitting when communicating in the first digital traffic channel DTC3, and in the target base station it measures and evaluates the decoded digital verification color code, the intensity of the received signal and the quality of the received burst. In the base station BS2 illustrated in Figure 7, these prior art tests are complemented by the method of detecting the presence of the inventive mobile station. The verification request sent from the mobile services switching center MSC2 contains information defining the first digital traffic channel DTC3, that is, information of the frequency and time slot, and the temporary identity of the mobile station assigned to the mobile station MS2. The base station BS2 tunes a radio receiver to the second base station BS2 according to the information provided defining the first digital traffic channel DTC3 and tries to receive identity messages transmitted by the mobile station MS2. If the base station BS2 is successful in receiving at least one occurrence of an identity message ID2 containing a temporary identity of the mobile station that matches the identity assigned to the mobile station MS2, the second base station BS2 concludes that the The received radio signal is transmitted by the mobile station MS2 and returns a verification result message to the mobile services switching center indicating that the mobile station MS2 has been detected as present in the vicinity of the base station BS2. Another application of the invention is illustrated in Figure 8. The SYS3 radio communication system illustrated in Figure 8 consists of the public cellular network PLMN1, the public telephone network PSTN1 and the mobile station MSI of Figure 1. In the radiocommunication system SYS3 of Figure 8, the base station of residence HBSl of Figure 8 has been replaced by a detector of the presence of residence DET1. The idea behind this arrangement is that when the subscriber of the cellular network uses his MSI mobile station to communicate while he is at home, the communication is still handled by the cellular network PLMNl but the subscriber of the cellular network will obtain a discount, that is, lower airtime costs. The presence of the mobile station MSI in the vicinity of the detector of residence presence DETl is detected using a method similar to that illustrated in Figure 2A where the residence presence detector DETl in Figure 8 replaces the station residence base HBSl of Figure 1. When the residence presence detector DETl registers the mobile station MSI as present in the vicinity of the residence presence detector DETl, i.e., within the area illustrated as a shaded circle 801 in Figure 7, the residence presence detector DETl records the time when the mobile station MSI is detected as present, that is, the time at which a first occurrence of identity information ID1 transmitted by the station is received. MSI mobile in the first digital traffic channel DTCl. The residence presence detector DETl continues to verify the first digital traffic channel DTCl for more repetitions of identity information ID1 until it decides that the first digital traffic channel DTCl has been released or that the mobile station MSI has moved away from the proximities of the residence presence detector DETl, ie, that the mobile station MSI has moved away from the area 801. The residence presence detector MSI records the reception time of the last received repetition of the identity information ID1. The residence presence detector DETl initiates a modem connection with manual dialing via the telephone network PSTNl to the mobile services switching center MSC1 and transfers a message to the mobile services switching center MSC1 informing it of the reception times of the first and last occurrence received from identity information ID1. The mobile services switching center MSC1 stores this information. When the subscriber of the cellular network is invoiced, charges for airtime are reduced according to the information stored when the subscriber of the cellular network has been at his residence while communicating. The residence presence detector DETl comprises a subset of these blocks illustrated in Figure 5, ie the blocks 501, 505-512 which functions mainly as described above when the 30-bit random identity is generated and detects the presence of the mobile station MSI. When the mobile station MSI has been detected communicating in the vicinity of the residence presence detector DETl, the residence presence detector DETl proceeds to record the time of receipt of the first and last occurrence of the identity message IDl in the first DTCl digital traffic channel. The residence presence detector DETl then initiates a modem connection with manual dialing to the mobile services switching center MSC1 and transfers the reception times of the first and last occurrence received from the ID1 identity information together with the subscriber number of the cellular network subscriber. Instead of starting a modem connection with manual dialing and transferring a message to the mobile services switching center MSC1 each time the residence resilience detector DETl detects the mobile station MSI communicating within the 801 area, the detection of the presence of residence DETl may store information related to a number of communication occurrences within the 801 area and send a single message to the mobile services switching center MSCI transporting this stored information. This single message can, for example, be sent once every night. As one skilled in the art will appreciate, there are several other possible ways for a residence presence detector to communicate with a mobile services switching center in addition to the telephone network as illustrated in Figure 8. The detector of the Presence of residence can of course be connected to and communicated by another type of wired network, such as, for example, an Integrated Digital Services Network (ISDN, Integrated Services Digital Network). The residence presence detector can also communicate with the switching center and mobile services using radio communication such as mobitex or Cellular Digital Packet Data (CDPD, Data in Digital Cellular Packet). The method of detecting the presence of the mobile station of the invention can, of course, be supplemented with other methods to determine the positioning of the mobile station, such as differences in time of arrival, to determine a more accurate position of a mobile station. mobile station. The invention, of course, is not limited to being used only in TIA / EIA IS-136 flexible radio systems, but can also be used in connection with other air interface specifications such as Global Systems for Mobile communication (GSM, Global Systems). for Mobile Communications), Personal Ditigal Cellular (PDC, Personal Digital Cellular) or TIA / EIA IS-95.

Claims (8)

1. A method for detecting the presence of a mobile station in a radiocommunication system (SYS1), comprises a first base station (BS1) and a mobile station (MSI), the method comprising the steps of: a) assigning (201) a first radio channel (DTCl) for communication of the control inforon (906) and inforon of the user data (904) between the mobile station (MSI) and the first base station (BS1); b) transmitting (202) inforon (ID1) identifying the mobile station (MSI) repeatedly in a portion (SACCH1) of the first radio channel (DTCl) used for the transmission of the control inforon (906); c) receiving (203) at least one occurrence of the transmitted identity inforon (ID1); d) registering (204) the mobile station (MSI) as present in a certain area (101) with the reception of at least one occurrence of the transmitted identity inforon (ID1), characterized in that the reception (203) in accordance with step c) includes sweeping for radio transmissions belonging to the first assigned radio channel (DTCl) on at least a subset of the radio frequency band used in the radio communication system (SYS1). The method according to claim 1 is characterized in that the inforon (ID1) identifying the mobile station is transmitted on a portion of the slow associated control channel (SACCH1) of the first radio channel (DTCl). 3. An autoc transfer method in a radio communication system (SYS1) comprises a first base station (BS1), a mobile station (MSI) and a second station (HBS1), the method is to determine the mobile station (MSI) as present within a coverage area (101) of the second base station (HBSl) performing the detection method according to any of claims 1-2 and further comprises the steps of: e) determining (204) whether the mobile station (MSI) is one of a series of at least one mobile stations that preferably should communicate with the second base station (HBSl) instead of the first base station (BSl) with the determination of the mobile station (MSI) as present within the coverage area (101) of the second base station (HBSl); f) making the autoc transfer of the mobile station (MSI) from the first radio channel (DTCl) to the second radio channel (DTC2) for communication of the control inforon (906) and inforon of the user data (904) between the second base station (HBSl) and the mobile station (MSI), then determine the mobile station (MSI) as being included in the series of mobile stations. 4. A radiocommunication system (SYS1) comprises a first base station (BS1), a mobile station (MSI) and a presence detector of the mobile station (HBS1), wherein: the radiocommunication system (SYS1) comprises the means (MSC1, BS1, MSI) to assign a first radio channel (DTC1) for communication of the control inforon (906) and user data inforon (904) between the mobile station (MSI) and the first base station (BSl); the mobile station (MSI) comprises the transmission means (404, 405, 407) adapted to transmit repeatedly the identity inforon (ID1) identifying the mobile station (MSI) in a portion (SACCH1) of the first radio channel (DTCl) used for the transmission of the control inforon (906); the detector of the presence of the mobile station (HBSl) comprises the receiving means (507, 511, 512) adapted to receive at least one occurrence of the transmitted identity inforon (ID1), the radiocommunication system (SYS1) comprises the medium receiver (507, 511, 512) adapted to receive less one occurrence of the transmitted identity inforon (ID1), the radio communication system (SYS1) comprises the registration means (507) adapted to register the mobile station (MSI) as present in the vicinity of the detector of the presence of the mobile station (HBSl) with the reception of identity inforon (ID1) by the receiving means (507, 511, 512), characterized in that the receiving means (507, 511, 512) is adapted to sweep the radio transmissions belonging to the first assigned radio channel (DTCl) on. minus one substring of the radio frequency band used in the radio communication system (SYSl) to receive the at least one occurrence of the transmitted identity information (ID1). The radio communication system (SYSl) according to claim 4, characterized in that the transmission means (404, 405, 407) is adapted to transmit the identity information (ID1) in a portion of the associated slow control channel ( SACCH1) of the first radio channel (DTCl). 6. The radiocommunication system (SYSl) according to any of claims 4-5 is characterized in that the radiocommunication system (SYSl) comprises: a second base station (HBSl) comprising the detector of the presence of the mobile station, the means for determining (507) whether the mobile station is one of a series of at least one mobile station that preferably must be communicated by the second base station (HBSl) instead of the first base station (BSl) with the record of the mobile station (MSI) as present in the vicinity of the detector of the presence of the mobile station (HBSl), the medium (HBSl, MSC1, BSl, MSI) for performing the automatic transfer of the mobile station (MSI) to the second radio channel (DTC2) for the communication of the control information (906) and information of the user data (904) between the second base station (HBSl ) and the mobile station (MSI), after determining the mobile station (MSI) as being included in the series of mobile stations. The radio communication system (SYSl) according to claim 6, characterized in that the first base station (BSl) belongs to a cellular public network (PLMNl), the second base station (HBSl) is a residence base station (HBSl). ) connected to a public wire network (PSTNl), and that the registration means (507) and the determination means (507) [sic] are included in the residence base station (HBSl). The radio communication system (SYS4) according to claim 6, characterized in that the first base station (BSl) belongs to a cellular public network (PLMNl), the second base station (OBS1) belongs to a wireless office system ( WOS1) and that the recording medium and the means of determination are included in the wireless office system (WOS1).