FI103468B - Limitation of the mobility of a subscriber terminal in a radio system - Google Patents

Description

1, 103468

Restriction of subscriber device mobility in a radio system

FIELD OF THE INVENTION The present invention relates to a method for monitoring terminal mobility in a system where part of the subscriber line is comprised of a radio link between a radio part of the terminal and a base station. The system may be a cellular cellular telephone system, but a particular application is a radio system implementing a wireless subscriber line, comprising base stations and wireless terminals with limited mobility, to which a subscriber unit may be connected, which may be a standard fixed network telephone.

Background of the Invention

In fixed telephone networks, a subscriber line network is formed such that a pair of subscriber terminals outgoing from a plurality of subscriber terminals is routed to a crossover device, and the outgoing wires from a plurality of subscriber terminals are connected in another crossover device from which the outgoing cable is routed. The signaling interface facing the exchange subscriber lines is standardized and is either a 2-wire analog subscriber line interface, a CCITT V2 recommendation multiplexer interface or a ETSI V5.1 recommendation multiplexer interface. Subscriber lines are a major expense, not only for network construction but also for network maintenance.

When constructing a telephone network, the installation of local loops between the exchange and the subscriber equipment is not only a considerable expense but also a time-consuming operation. Especially in sparsely populated areas, the cost per connection may be high: V 25. One solution to reduce costs is to replace the fixed subscriber loop between the exchange and the subscriber unit with a ::: radio link. The fixed subscriber station is then connected to a terminal containing a radio transmitter / receiver, which converts the subscriber unit's audio frequency signal to radio frequency and transmits it over the radio to the base station 30, respectively, and converts the received radio frequency signal into an audio frequency signal.

Such a solution can be based on either a complete analogue or digital cellular subsystem containing a mobile switching center, where:. , the terminals are connected to the base station or it may be a modified cellular system from which some network elements have been removed and some functions simplified. The common name for the solutions in this application is called the Wireless Local Loop System (WLL).

The WLL system may be constructed by applying components of an existing cellular system. The mobile telephone system may be an analog or digital system. In this case, the signaling of the WLL system is in accordance with that system; the system standard base stations and the radio part of the terminal device similar to the radio part of the mobile station or the terminal may be a mobile station of the mobile system as such, whereby the terminal and the subscriber unit (telephone) are combined into one physical device. An important component of the WLL system is a local area network (LAN) element that connects subscribers to a standard local exchange. In a pure cellular system, the access node is a mobile switching center and in the applied system a network element to be described later. The subscriber network element converts WLL network signaling, e.g., analog NMT system or di-15 digital GSM rigid system signaling, into a fixed network (e.g., PSTN) signaling and respectively adapts the fixed network signaling to the WLL network interface.

The principle of one WLL system is shown in Figure 1. The wireless fixed terminal T comprises a radio part with an antenna and a telephone adapter 20 which connects a standard subscriber unit 5 to the terminal. · The subscriber unit can be a standard telephone machine, a fax machine or a modem. It is connected to the terminal by inserting the standard plug into the adapter connector of the terminal. The subscriber unit 5 is used by the user as in a standard wired network, although the majority of the subscriber line connection consists of a radio link between the terminal T and: 2 or 3 of the base transceiver station BTS.

The subscriber device may also be a conventional mobile station 6 according to the system on which the WLL is based. Each base station can serve a plurality of subscriber equipment. The support stations are connected to a special access network element 1, which in turn is connected to a standard telephone exchange.

The network element 1 connects to the local exchange with type V2 or V5.1. ' with an open 2Mbps PCM multiplexer interface. If *: · the local exchange only supports a 2-wire interface, the network element is · connected to the exchange by converting V2 signaling by a multiplexer to an analog 2-wire: subscriber interface.

• ...: 35 Signaling between a network element and associated base stations is signaling of an applied cellular network, however modified so that functions typical of the cellular network, such as cell handover and roaming, are unnecessarily omitted. Thus, the subscriber must remain within the coverage area of the designated base station. The routing of incoming and outgoing calls is based on the subscriber file of the network element. The function of the network element corresponds to the operation of the hub: the call is transmitted from the subscriber line to the exchange and the analysis of numbers, counting and other functions are performed in the exchange.

As stated above, the WLL network may be based on a digital cellular system. Here, the mobile station must measure the power of the received signal, the BCCH carrier 10 of neighboring base stations, and calculate a bit error rate describing the quality of the received signal. It has to report the measurement results at certain intervals, eg in the GSM system the results can be sent twice per second. In a WLL application, the terminal can, and in most cases also, perform the same measurements as a mobile station, although handover-related measurements are unnecessary.

In time-divisional digital cellular systems, transmission takes place in a transmission time slot burst. At the end of each burst, there is a certain duration of protection so that the received successive bursts do not overlap. The guard time is required because the mobile stations detected on the same radio carrier but at different time intervals are at a random distance from the base station, whereby the propagation time of the radio waves from the base station to the mobile station varies from time to time. Therefore, the duration of bursts transmitted in time slots must be.! slightly shorter than the time slot so that the base station receives no adjacent; ; the bursts transmitted in these time slots would overlap. To keep the protection time as low as possible: f 25, the system is configured so that the base station dynamically adjusts the transmission time of each mobile station based on the bursts it receives. The base station gives the mobile station a so-called. Timing Advance (TA), according to which the mobile station controls the start of the transmission time. In the GSM system, the timing advance can obtain values from 30 0 to 233 ps, which, taking into account the time slot duration, means that the mobile station using the maximum timing advance may be within 35 km of the base station. ·: · Scale. The guard time is determined so that within the timing of the transmit / receive frame, the base station measures the time difference between its transmitted burst and the burst it receives from the mobile station, and calculates a timing advance which it informs the mobile station twice per second.

4, 103468

In a cellular network, all cells are known to be equal in terms of call counting bases, so that no other counting base can be assigned to the subscriber other than the elasticity based on the time of day or a specific number pair. The former sets a special billing parameter that allows calls made from a number associated with the parameter to be charged less than usual at times when the load on the cellular network is low and, accordingly, more than normal when the load on the cellular network is high. This parameter adds a time dependency to the call counting basis. The latter is a so-called. A home call where a call between a mobile station and a subscriber's fixed terminal is priced lower than normal. The distance between the calling and called subscriber or the location of the called subscriber could not be taken into account in the calculation in real time. No specific calculation criteria were available for inter-cellular or inter-cellular calls.

15 Solutions to these problems are provided in Applicant Patent Applications FI-946091 and FI-946092. Accordingly, one cell or a plurality of cells in a cellular network is set up as a group of special cells. Cells in a group may be in different central regions. When establishing a call, the exchange analyzes whether the calling subscriber's location cell and / or the called subscriber's location cell belong to a group of 20 special cells. If the calling and called subscriber's location cells are in a different central area, the applications further provide a method for transmitting the called subscriber's location cell information to the calling subscriber's exchange before the voice call; den. It is also possible to define the order of subscriber numbers; a large group. In this case, depending on whether the subscribers are in a special cell group and / or whether the subscriber numbers belong to the subscriber group, different call rates can be varied.

The second application differs from the first application in that, when establishing a call, the service control point SCP in the intelligent network analyzes whether the calling subscriber location cell and / or the called subscriber location cell belong to a group of special cells. The service control point SCP then applies the call set to the group: ·. the specific basis of calculation. In the central area, information about the location of the called subscriber is transmitted to the service control point of the calling subscriber's mobile switching center, either directly or in a message-to-mobile signaling mass.

5, 103468

The applicant's previous patent applications mentioned above allow one or more specific cells to be defined for a mobile subscriber. a home cell that calls to and from is cheaper than calls elsewhere in the network. This principle is also applicable to the WLL-5 subscriber. After all, the subscriber has a specific home cell and movement from one cell to another is prevented so that handover is not possible.

While it is possible to define a home cell for a mobile and WLL subscriber, the problem remains that the cell area is the smallest regional unit. Thus, it is not possible, for example, to limit the area of cheaper calls to an area smaller than 10 cells. The problem is especially true for those mobile subscribers who do not have a landline phone at all but would still like to have cheaper calls from home or any place they like, such as from a cottage. In addition, in some WLL cases, the operator may wish to limit the mobility of the WLL terminal to a smaller area of the cell and prevent mobility outside that area. It would also be desirable to be able to select only certain terminals whose greater cellular mobility is prevented.

It is therefore an object of the present invention to provide a method for defining a specific area smaller than a cell area for a subscriber unit and to monitor in real time whether the subscriber unit is within this defined area. The area should be defined either by the operator or the subscriber should be able to define at least the cell to which the specific area belongs. The cell may be a normal cell in a mobile network or a cell in a WLL system. Another object is to provide a method. ; which allows the user to make cheaper calls within a user-selected range of less than 25 cells.

The objectives set are achieved by the attributes set forth in the independent claim.

BRIEF SUMMARY OF THE INVENTION According to the basic idea of the invention, a quantity proportional to the distance between the terminal and the base station communicating with the terminal is determined several times during the connection and thus proportional to the signal propagation time. The quantity may be directly the propagation time of the signal or, in practice, a proportional factor. In digital time-division systems' · ... · 35, a pre-existing time advance calculation is used as a proportional measure. In CDMA systems, delayed 103 1038 shifts between two base station pilot signals can be estimated by correlating their spreading codes. In analog systems, the signal propagation time is determined, for example, on the basis of a known signal used as a basis for handover decision, which is transmitted to the terminal by the base station and returned by the terminal. If there are no suitable existing signals in the system from which the travel time can be calculated, they must be generated separately.

According to the first embodiment, a magnitude proportional to the time of the signal is compared in advance to a reference value (s) set on a terminal stored in the network, which defines a allowed range of less than 10 cells. If the network detects that a quantity or change thereof exceeds the allowable limits, it determines that the terminal has left the allowable range and proceeds in a predetermined manner. The method may be, for example, disconnecting, giving a voice announcement, changing the call tariff, etc. This embodiment is particularly suitable for limiting the mobility of WLLLs.

According to another embodiment, the terminal itself activates the large measuring process. For example, the activation can be performed once, and the resulting value is permanently stored in the network database. Activation can also be performed whenever desired, whereby the activation result updates the result of the previous 20 activations. In both cases, in response to activation, the network performs a large measurement and stores a cell identifier and a 'large value' in the database. As the terminal moves, the network continuously evaluates its distance.:: From the base station and does not react at all if the size change is allowed; within. This creates a permissible area inside the cell, which the terminal itself is; · '25 activated for use. If the change in the quantity exceeds the allowable value, the network interprets the terminal to leave the allowed area and proceeds in a predetermined manner. The ways may be those of the first embodiment. Another embodiment is particularly well suited to a cellular mobile communication system, whereby the subscriber can himself determine the area in which he wants the cheaper call charges. Only one area or areas may be allowed at a time:. there may be several.

According to a preferred embodiment, the signal propagation times between the terminal and the plurality of base stations are measured, and from the travel times a more accurate location of the terminal is calculated.

C. 35 • · 7 103468

List of figures

The invention will be explained in more detail with reference to the accompanying schematic figures, of which: Figure 1 illustrates the principle of a WLL system, Figure 2 illustrates a cell having a WLL terminal and Figure 3 illustrates another embodiment.

DETAILED DESCRIPTION OF THE INVENTION The principle and first embodiment of the invention will be described using the WLL system as an example, but the same principle is of course applicable to any cellular cellular telephone system. In this case, the terminal is a normal system mobile station and the base station is connected to the mobile switching center via the base station controller. Figure 2 shows a cell formed by the radio coverage of a base station BTS. Within the cell, a subscriber line connection to a network element 21 is established by a radio link between a base station BTS and a WLL terminal 22 connected by a fixed line. Usually, the terminal is comparable to a fixed unit and is located in a residential building with its subscriber equipment, which may be e.g. a landline telephone or a fax machine. There is no terminal. allowed to leave outside the cell. This is prevented by the fact that the WLL system does not allow handover between cells. Within the cell, the terminal may present; free movement in those systems. In the case of a digital WLL system:. ; therefore, the network continuously calculates its base station transmitting to the WLL terminal:; Based on the time difference between the burst 25 and the burst received from it, the prediction value TA, which is a numerical number.

It is assumed that the operator wants to limit the mobility of the WLL subscriber device to the allowed area A only. According to the invention, a distance proportional to the distance between the WLL terminal 22 and the base station BTS 30 connected to the terminal is determined. The mobile station has moved over the allowed range. Since the signal time ·: · time is proportional to the aforementioned timing advance value TA, this value can be used directly to control the movement of the terminal. in the area farthest from the base station, the time advance • ·. ·: · would be approximated by TA2 This fact is exploited by comparing the measured timing advance value TA with the timing advance values TA1 and TA2 stored in the data of that terminal. comparison applies to TA1 <TA <TA2 so the network will not respond in any way. If the comparison applies TA <TA1 or TA> TA2 proceed as set. Can be e.g.

5 alert the network, prevent a call, give a subscriber a voice announcement, automatically switch to another, more expensive billing tariff, etc.

The same result is achieved by the network observing the change in the subscriber terminal timing prediction. As a reference, the timing prefix TAref, measured at the location location of the subscriber unit's nor-10 and stored in the network database, is taken and if the change ΔΤ exceeds a predetermined limit,

TA2 - OR

fuck in the set way. The limit could be eg---.

Terminals using TA1 located at a radius R 'from the base station BTS and terminals using TA2 at a radius R 15 from the base station. Thus, when using these two values to control the motion of the terminal, the result is that the terminal can move unreactedly within the cell segment defined by these beams, i.e. the annular region, without reacting. In practice, due to the influence of the terrain, the allowed area is of course not purely annular.

This terminal prediction information for the terminal may be stored in a · · subscriber database located in a pure cellular system: · Home Location Register (HLR) or a WLL-: system based on it in a subscriber network element.

By modifying the aforementioned boundaries TA1 and TA2, it is possible to change: [25 annular areas in which the terminal is allowed to move.

The use of a timing advance value in the method according to the invention is advantageous because in digital time-division systems such a value is calculated anyway, whereby this numeric value can be used as such. If there is some function in the WLL system or digital cellular system that the mobile station returns bursts to base stations other than the one with which it is communicating, in other words, it sometimes communicates with neighboring base stations: Y utilizes womanhood to control terminal mobility. It has been proposed in the art, for example, to include in the GSM system such a feature that the network 35 would also display the signal propagation time between the mobile station and the neighboring base stations to determine the timing advance. Then, each neighboring base station would send a burst which the mobile station would return to that base station. Travel time is calculated from the time difference between the base station's transmit and receive times. If such a feature already exists or is implemented in the network, the positioning of the WLL terminal or the mobile station can be calculated from the propagation times of the 5 signals using known radio positioning methods with reasonable accuracy. In this case, it is sufficient to know the signal propagation times for the three base stations.

The invention has been described above in a digital time-sharing WLL environment. The monitoring according to the invention requires measuring the propagation time of the signal 10 between the terminal and the base station. In the analogue WLL environment, so-called. color signal. In analog cellular systems such as AMPS, TACS and NMT, the base station generates a continuous monitoring signal during a call (commanded by a mobile switching center) and transmits it to the mobile station. In NMT, the control signals are in the range of about 15 to 4000 Hz. The mobile station returns the signal back to the base station, which evaluates the received signal and determines on the basis of the evaluation whether the transmission quality is such that it requires transferring the connection to another base station, i.e. a handover, or disconnecting. The quality of transmission is measured by a signal-to-noise ratio integrated over a period of time.

This monitoring signal can be utilized in the method of the invention. Because the base station transmits a certain frequency signal and. , the terminal returning the same signal back to the base station, adding means for calculating the propagation time of the signal between the terminal and the base station to the network. order. The devices are preferably a suitable program. The calculated travel time is compared with 1 · 25 paths to setpoints as described above for the digital system.

• I

or observe the change in travel time. If the travel time exceeds or falls below the set points, or the travel time change exceeds the allowable value, proceed as set.

The Code Division Multiple Access (CDMA) system does not use 30 time slots and thus does not calculate a timing advance value. However, the invention is so-; * ·, chargeable in a cellular system based thereon or in a WLL-based system, because in a CDMA cellular system, the propagation time difference between two so-called. between the pilot signal. Each base station transmits its own pilot signal having its own unique spreading code: ... 35. The mobile station or WLL terminal receives the pilot signals transmitted by a plurality of base stations and correlation between the pilot stations of the two base stations (BTS1 and BTS2) can be directly measured, which is the difference in signal propagation times between the mobile station and the base stations. This aspect is well known in the art. In practice, the measurement can be implemented as part of the reception algorithm. If large changes in this time difference are denied, i.e. there is only a certain allowed change, then the allowed operating range of the mobile station or WLL may be severely limited. The result is an allowed area in the cell.

Another embodiment of the invention will be described with reference to Figure 3. The figure shows a typical cellular network in which base stations BS are connected to their own base station controller BSC, which in turn is connected to a mobile switching center MSC, which in the figure has two MSC1 and MSC2, thus having two central areas.

Mobile station 1 can communicate with a network from any cell in the network and the cost of a call is always the same in traditional networks. However, a mobile subscriber 15 whose home is located, for example, in cell area a of the location area 11, might want cheaper call rates while the mobile station is at home. According to another embodiment of the invention, this is made possible by creating an area A around the subscriber's home and using a cheaper tariff for calls within this area. The area A is determined as described above in FIG. 20, based on a basic amount that is proportional to the distance between the mobile station 1 and the base station BTS 2, in the TDMA system. . basis. The timing advance value TA can be used directly to control the mobile station's movement. In the case of a CDMA system, the pilot signal transmitted by the base station 2 and 6 is used to determine the area.

: '. · 25 There are several ways to determine the area. Firstly, when the subscriber buys a mobile station, a separate measurement can be performed, which determines a timing advance between base station 2 or pilot signals to determine the propagation time difference between the signals from base stations 2 and 6. This timing estimate / propagation time difference 30 and the identifier of cell a are stored in the subscriber data in the HLR. Therefore, the position of the allowed range of cells cannot be changed without a repeat measurement. Secondly, a function may be provided in the network which, in response to a message sent by the mobile station, stores the current timing estimate and cell identifier in the home location register. The user can generate a message by keying in a specific code, or the message can be sent programmatically so that pressing a specific key automatically transmits the message 103468. In this case, it is easy to change the location of the allowed area.

The latter case is particularly advantageous when more than one permitted area is desired. When the subscriber moves to his summer cottage, for example, in the central area of the switchboard MSC2 in cell h, he performs the above registration function, whereby the new timing advance value and the cell identifier are stored in the home location register. Now the subscriber has the option of cheaper calls within the allowed area B. New subscriber data can replace the old ones or allow a certain number of allowed areas, such as home, cottage, workplace, etc. with cheaper calls.

In both cases, at the beginning of the call, the network compares the cell ID and its measured timing advance value with its subscriber data stored in the home location register HLR. If they show that the mobile station is at home, i.e. its allowed area A is using its cheaper billing. If this is not the case, or during the pu-15 call, the timing preset value or its change exceeds a predetermined limit, the subscriber has been deemed to have left his home and the billing tariff may be made more expensive. Once the subscriber has moved out of the cell area, there is no need to monitor the propagation delay at all.

In the manner of the invention, the mobility of the terminal can be restricted to a much smaller area than the cell area. Limiting mobility facilitates network frequency planning and allows the use of smaller cellular billing zones. While remaining within the scope of the claims, the invention may be implemented in a number of ways which have in common the determination of a size proportional to the distance between the terminal and the base station.

• * • • • • • • • • • • • • • • • • • • • • •

Claims (15)

A method for observing the movement of a mobile telephony in a system in which part of a subscriber connection is the radio connection between a terminal equipment and a base station, characterized in that for each terminal equipment whose position it is desired to determine: a quantity proportional to the propagation time of a signal between the terminal equipment and at least one base station, the magnitude is compared with a comparison value and on the basis of the comparison conclusions are drawn if the terminal equipment is within the permissible range. Method according to claim 1, characterized in that the magnitude proportional to the propagation time is achieved by requesting a time-divided system by using the time offset value for a transmission from the terminal equipment which is calculated on the basis of a burst which the base station communicates with has transmitted. to the terminal equipment and which the terminal equipment has returned. Method according to claim 1, characterized in that the magnitude proportional to the propagation time is achieved by requesting a time-divided system by calculating the difference between the propagation time of the signals between the terminal equipment and the base station with which the terminal equipment communicates respectively for the signals between the terminal equipment; the armor and at least one neighbor base station. Method according to claim 1, characterized in that the magnitude proportional to the propagation time in respect of a spread-spectrum system (CDMA) is achieved in that the terminal equipment receives pilot signals from the base station with which it communicates and from the etmine. -tone a neighbor base station and calculate the difference between propagation times. ·: ·. by correlating these. • · · I .., 5. A method according to claim 1, characterized in that, in the case where the value of the measured proportional quantity is located within a predetermined range, it is concluded that the terminal equipment is: ***: within the permissible range. 6. A method according to claim 5, characterized in that, in the event that the measured proportional quantity is located outside said range, it is concluded that the terminal equipment is outside the allowed range and it is operated in a predetermined manner. 16 103468 7. A method for determining the basis for which a call is priced at a system in which a portion of a subscriber connection is the radio connection between a terminal equipment located within a cell and the base station of the cell, characterized in that it measures a quantity which is proportional to the propagation time of a signal between a terminal equipment and at least one base station and this quantity and the cell identifier is stored in a subscriber database, the quantity and identifier of the terminal equipment defining an allowable area less than said cell area, said proportional quantity being measured again upon connection of a call and it and the identifier of the cell currently being used are compared with the values stored in the database, a special calculation basis is used during the call if the comparison indicates that the terminal equipment is within the allowed range. 15 Method according to claim 7, characterized in that the magnitude proportional to the propagation time in respect of a time-division system is achieved by using the time offset value for a transmission from the terminal equipment which is calculated on the basis of a burst which the base station communicates with the terminal equipment. the terminal equipment and which the terminal equipment has returned. Method according to claim 7, characterized in that the magnitude proportional to the propagation time in respect of a time-divided system is achieved by calculating the difference between the propagation time of the signals between the terminal equipment and the base station with which the terminal equipment communicates and for signals between the terminal equipment, respectively. - • · · armor and at least one neighbor base station. Method according to claim 7, characterized in that the magnitude proportional to the propagation time in respect of a spread spectrum system (CDMA) is achieved in that the terminal equipment receives pilot signals from the base station with which it communicates and from the transmission memory. V ·! tone a neighbor base station and calculate the difference between propagation times by correlating them. 11. A method according to claim 7, characterized in that a base station proportional to the propagation time of a signal between the terminal equipment and the terminal memory and the cell identifier is permanently stored in the subscriber database. 17 103468 Method according to claim 7, characterized in that a base station proportional to the propagation time of a signal between the terminal equipment and the tone station is stored and the cell identifier is stored in the database in response to an activation performed by the terminal equipment user, the user himself being able to create a permissible area in the desired cell. Method according to claim 12, characterized in that the user can create several permissible areas in the network himself. 14. A method according to claim 7, characterized in that a lower call price is applied than in the case of connections that are connected outside the permitted area in the question of the particular calculation basis. 15. A method according to claim 7, characterized in that a quantity proportional to a base station proportional to the propagation time of a signal between the terminal equipment and the eating station is measured and the comparison is carried out several ginger during the call, the basis for calculating the price of the call changing as the user departs from the permissible range. • I ♦ · · • «« «· · · · ♦ ♦ · · ·« · · · · · · · · · · · · · · · · · ♦ ♦ 1 · ·