HK1066139B

HK1066139B - Subscription-based mobile station idle mode cell selection

Info

Publication number: HK1066139B
Application number: HK04108928.6A
Authority: HK
Inventors: Viola Nordstrand Ingrid
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 1997-03-07
Filing date: 2000-11-24
Publication date: 2009-09-04

Description

User based mobile station idle mode cell selection

Technical Field

The present invention relates to wireless communication systems (e.g., cellular or satellite systems), and more particularly to techniques for scheduling wireless communications to a preferred server (e.g., a base station) when there is more than one server.

Background

In today's advanced wireless telecommunication networks, the demand for the ability to differentiate between different kinds of end users (e.g. telephone users) is constantly increasing, which may be due to e.g. market factors, an example of a market driven reason for end user differentiation is that an operator wants to ensure that a selected group of end users (e.g. employees of a specific company) have a certain call capacity in situations where the operator wants to be within the area covered by some servers (e.g. in the area covered by servers installed at the company's premises). To make this possible, it is important to prevent other users not belonging to this group from making any calls in these particular servers.

Another example of a reason for market differentiation that end users differentiate is that operators wish to provide only a limited portion of their network for calls that are allowed access, the allowed area being determined by the geographic area that covers one or more wireless communication servers (e.g., base stations). In this case it is important that the mobile station does not enter the wireless communication system when it is outside the allowed service area, and that the user needs to be alerted at this time that he/she has gone outside the allowed service area, which can be indicated by the mobile station.

Another market-driven reason for differentiating end users is that operators want to offer users different levels of speech depending on the region where service is requested and/or received, in which case it is important that the mobile station has information of the user's preferred service area in order to select the best service area among the existing service areas; in this case, it is also important to let the user know in advance whether to establish a service application in the preferred area.

Apart from the actual need for end user differentiation, the existing idle mode cell selection/reselection procedures for GSM Mobile Stations (MS) do not include any consideration of user area in the selected "public land mobile network" (PLMN). For GSM network operators, it is preferable to use conventional techniques to:

1) only in one part of the network (e.g. a predefined subset of cells) the subscription is defined with allowed access;

2) access to a certain number of users (e.g. a group of users) is restricted to one part of the network (e.g. a predefined subset of cells).

3) Setting up a special charging table and allowing special services according to the reservation and the access place of the user;

however, if the operator wants such a function/service, this must be handled by the network itself, since the current GSM standard does not provide any support for any service area considerations during idle mode cell selection by the MS, which does not have any subscription area information. Thus, cell selection will be made by all MSs within the PLMN in the same manner, independent of the subscription.

For example, looking at the conventional method of restricting a subscriber's subscription to a portion of the network, when an MS is camped on a cell and ready for service, the subscriber may initiate the establishment of a call, which initially results in the establishment of a signaling connection between the MS and the network, and the network may then authenticate the MS and make the necessary subscription control. Depending on factors such as the data of the reserved service area (if any), the network either accepts or rejects the call to be set up.

If the network refuses to set up the call, either because the subscriber is subscribed because it is outside the allowed area, or if a cell is used exclusively by a subscriber group to which the subscriber does not belong, the signaling connection is released. However, in conventional systems, it is not possible for the network to prevent a user (e.g., an MS) from trying to make a reservation again in the same cell, which would result in rejection by the network. It can be seen that the use of conventional techniques would cause this type of end-user differentiating functionality to detrimentally occupy radio and network resources.

Defining a restricted coverage area for the user in a conventional manner has further consequences as will be appreciated by examining an example where an MS is in the coverage area of two cells, designated areas a and B, each of which is suitable for camping, assuming that the C1 criterion is calculated for each of cells a and B, cell a is found to be the best call and camped on, if the user's subscription data indicates that only call B is allowed, the user attempts to initiate a call to be rejected by the network (i.e. for example due to the user attempting to set up a call via cell a). However, conventional techniques do not provide any mechanism for a user or network to force an MS to camp on another cell (e.g., a B cell). Thus, if the radio conditions remain the same (i.e., the user is not moving), the MS will continue to camp on cell a and subsequent attempts to establish a call will be ineffective.

Considering now an example, the "preferred zones" are accomplished using conventional techniques and technologies, i.e., some zones of the system are designated as being preferred over others in handling calls initiated by a particular subscriber's MS. Assuming for ease of description that the MS is in two cell coverage areas (set as areas a and B), each of which is suitable for camping, further assuming that the C1 criterion is calculated for each of cells a and B, cell a is found to be the best call, which results in the MS camping on cell a.

However, assuming that the user's subscription data indicates that cell B is more suitable than cell a, (e.g., assuming that the user is free of charge using cell B and cell a is not), the user's MS would like to camp on cell B instead of a. However, although the radio conditions remain the same (e.g., the user is not moving), the MS will continue to camp on cell a and any calls will be established in a "more expensive" area. Simply put, the conventional approach cannot force the MS to camp on other cells.

In summary,

1) for a user who is allowed access to a restricted part of a PLMN (i.e. a restricted part of a GSM radio network), the mobile station can occupy radio and network resources in the PLMN even if it is outside the allowed area.

2) For a user who is allowed access to the entire PLMN but preferably to a restricted part of the PLMN, the mobile station may establish a connection outside the preferred area of the PLMN, although there is also another suitable cell belonging to the preferred part. For "suitable" definitions, see TS GSM03.22, v.4.11.0, published by ETSI, which is herein written by reference.

3) Even if only a particular subscriber group is allowed access to a restricted portion of the PLMN, it is not possible to completely prevent other mobile stations (i.e., mobile stations associated with other subscribers) from occupying the radio and network resources of that portion of the PLMN.

Conventional systems do not provide a satisfactory solution to these problems, for example international patent application No. wo95/07010 discloses a communication system in which mobile stations can switch between areas of overlapping coverage provided, the areas being selected based on the service used. However, it does not disclose any technique for distinguishing between allowed areas, disallowed areas, and respective preferred areas, based on user identification rather than service to enable a mobile network user to occupy and log in these areas.

Us patent No.5,627,877 discloses an adaptive relocation of user data between network entities when the user moves in order to reduce the need for traffic in the network, which does not disclose the possibility of reducing network traffic by defining allowed/disallowed service areas based on the user data during the cell selection process performed by the mobile station, which areas are distinguished from each other.

Us patent No.5,404,580 discloses the possibility of a particular radiotelephone (i.e. a particular mobile device) operating with only one particular "subscription identity module" (SIM) by embedding a memory unit in the radiotelephone, the memory unit storing subscription data, the service obtained being dependent on a combination of the memory unit data and the SIM card inserted in the radiotelephone. Us patent No.5,444,764 discloses a special case of the functionality provided by us patent No.5,404,580, which gives a special case of defining the use of a particular radiotelephone for a subscriber having a SIM with an IMSI in the range of valid IMSIs, information about the valid IMSIs being programmed into a memory module of the radiotelephone.

Us patent No.5,499,386 discloses a multi-tier cellular radio architecture that serves mobile subscriber stations moving within the system. The best server is selected for the mobile station by setting a reference value in each cell for each of the other cells in relation to the vicinity of the service area. The strength of the radio signal received by the mobile station from the serving cell and the radio channel associated with the cell are measured and the best serving area is determined for the mobile station based on the preference values associated with the associated cells and the signal strengths of their respective radio channels. In this way, a "hierarchical cell structure" (HCS) is established. However, the preferred parameters determined during cell selection are the same for all mobile stations regardless of the subscription.

Disclosure of Invention

It is an object of the present invention to provide an arrangement and a method for enabling a selected user to exclusively access certain specific service areas in a mobile communication network.

It is a further object of the present invention to provide an apparatus and method that limits certain users to only a portion of a communication network that accesses an operator.

It is a further object of the present invention to provide an apparatus and method for alerting a user that he/she has gone outside his/her allowed service area.

It is yet another object of the present invention to provide an apparatus and method to allow an operator to provide different charging levels to a user depending on the area where a service is requested and/or received.

It is yet another object of the present invention to provide an apparatus and method that allows a mobile station to select an optimal one of a plurality of provided service areas and that makes it possible for a user of such a mobile station to know in advance whether a service establishment will be applied in the preferred area.

Accordingly, a mobile communication apparatus according to the present invention for use in a communication system including a public land mobile network and divided into a plurality of cells, comprises: a wireless device for contacting a public land mobile network; means for determining whether any one cell is part of a predetermined service area in which the mobile communication device is permitted to use a cell and at least one other mobile communication device in the communication system is not permitted to use a cell within the predetermined service area, wherein information identifying the different parts of the public land mobile network to which a user is permitted access is stored in said mobile communication device, which information is used by said mobile communication device to compare in idle mode with cell information broadcast from a cell to determine whether said mobile communication device is camped on the cell.

The method according to the invention for use in a communication system divided into a plurality of cells comprises the steps of:

broadcasting information about a cell from at least one cell;

in a mobile communication device for use in a communication system, the steps of:

receiving information on a cell from at least one cell;

determining, using the received information about the cells, whether the at least one cell belongs to a part of a predetermined service area, the mobile communication device being allowed to use cells within the predetermined service area, and at least one other mobile communication device for use in the communication system not being allowed to use cells within the predetermined service area,

wherein the information about the cell is a cell identification number uniquely identifying a corresponding cell, an

Wherein information identifying different parts of a public land mobile network to which a user is allowed access is stored in the mobile communication device, which information is used by the mobile communication device in idle mode to compare with cell information broadcast from a cell in order to determine whether the mobile communication device is camped on the cell.

The foregoing and other objects are achieved by the methods and apparatus for use in a communication system including a public land mobile network and a plurality of cells. Viewed from one aspect the invention comprises a mobile communication device comprising means for contacting a public land network and means for determining whether the mobile communication device is allowed to camp on a cell. This may be achieved in part by means of a memory device, such as a "subscriber information module" (SIM), which is used to store information about which cell may be camped on. In one embodiment, the stored information includes a list of cells that may camp on, with the information of the list arranged to show a priority order for camping on the cells. The means for determining whether the mobile communication device is allowed to camp on a cell may further comprise means for receiving information about a cell broadcast from a cell in the communication system in a radio control channel indicating whether the cell is part of a public land mobile network in which access is allowed controlled by the subscription information data.

Viewed from a further aspect of the invention, the information about the cell indicates that the cell is part of a public land mobile network in which access is allowed controlled by the subscription information data, and the cell may further issue a standard "cell barring" signal. The mobile communications device may include means responsive to the determining means for ignoring the cell barring information if the determining means determines that the cell may be camped on, the information regarding which cell may be camped on being stored in the SIM.

Viewed from another aspect the present invention provides a mobile communications system and method comprising a public land mobile network; there is provided information about cells for broadcast transmission from at least one cell, the information about cells indicating, for each cell, whether the cell is part of a public land mobile network in which access is allowed controlled by subscription information data.

A mobile communication device for use in such a system may determine whether the mobile communication device is allowed to camp on at least one cell by receiving information about the cell from the at least one cell.

Viewed from another aspect the present invention consists in a mobile communications device for a communications system including a public land mobile network and divided into a plurality of cells, comprising wireless means for contacting the public land mobile network and means for determining whether each cell is part of a predetermined service area, the mobile communications device being permitted to use cells within the predetermined area and at least one other mobile communications device for the communications system not being permitted to use the predetermined service area.

The means for determining whether each cell is part of a predetermined service area may comprise a memory means for storing information about which cell is part of the predetermined service area.

Viewed from another aspect of the invention, the mobile communication device may further comprise means for determining a list of cells suitable for camping, and for selecting a suitable cell by giving higher priority to cells of the part of the predetermined service area than to cells not belonging to the predetermined service area.

Viewed from another aspect of the present invention, the means for determining whether each cell is part of a predetermined service area may further comprise means for receiving information about the cell broadcast from a cell in the communication system from a radio control channel.

Viewed from another aspect the present invention comprises a method for a communication system divided into a plurality of cells, comprising broadcasting from at least one cell information transmitted about the cell. In a mobile communication device for use in a communication system, information regarding cells is received from at least one cell. Using the received information about the cells, it is determined whether the at least one cell is part of a predetermined service area, where the mobile communication device is allowed to use cells within the predetermined service area and at least one other mobile communication device for the communication system is not allowed to use the predetermined service cell.

The information on the cell may be a cell identification number uniquely identifying the corresponding cell. Here, the step of determining whether the at least one cell is part of the predetermined service area using the received information on the cells may include retrieving stored information on which cells are within the predetermined service area.

In an alternative embodiment, the information about the cell may be an identification number that uniquely identifies a service area containing one or more cells. Here, the step of determining whether at least one cell is part of the predetermined service area using the received information on the cells may include retrieving a stored service area identifier of the predetermined service area.

Viewed from another aspect the present invention provides a mobile communications device for use in a communications system comprising a public land mobile network and being divided into a plurality of cells. The mobile communication device comprises wireless means for receiving information about cells from one or more cells, and means for determining from the information about cells, during idle mode operation of the mobile communication device, whether to select a cell to camp on given one or more cells that are preferred over other cells with respect to the selection of a cell to camp on.

Viewed from another aspect of the present invention, means for selecting a cell to camp on by determining from information about cells whether to give one or more cells a higher priority than other cells during idle mode operation of a mobile communication device comprises storage means for storing information about which cells are given priority.

Viewed from another aspect of the present invention, the mobile communication device further comprises means for determining a list of suitable cells to camp on, and means for selecting a suitable cell by giving priority to the preferred cell over the non-preferred cell.

Viewed from another aspect of the present invention, a method for a communication system divided into a plurality of cells comprises the steps of: broadcasting and transmitting information on a cell from at least one cell; a mobile communication device for a communication system performs the steps of: receiving information on a cell from at least one cell; the received information about the cells is used during idle mode operation of the mobile communication device to determine whether to give at least one cell higher priority than other cells to select a cell to camp on. The information on the cell may be a cell identification number uniquely identifying the corresponding cell. Here, the received information about cells is used to determine whether at least one cell is given a higher priority than other cells during idle mode operation of the mobile communication device, including retrieving stored information about which cells are to be given a higher priority than other cells during idle mode operation of the mobile communication device to select the cell to camp on.

Alternatively, the information about the cell may be a service area identification number that uniquely identifies a service area containing one or more cells. Here, the step of using the received information about cells to determine which cells are to be given a higher priority than other cells during idle mode operation of the mobile communication device to select the cell to camp on includes retrieving a stored service area identification number of a service area given a higher priority than other cells during idle mode operation of the mobile communication device.

Drawings

The above and other objects and advantages of the present invention will be understood by reading the following detailed description in conjunction with the accompanying drawings.

FIG. 1 is a block diagram depicting a portion of a cellular communication network in which cells are overlapping coverage;

fig. 2 is a block diagram of a mobile station incorporating apparatus embodying various aspects of the present invention;

fig. 3 is a flow diagram illustrating the need for additions in the cell selection/reselection process for the processing of data containing a user's preferred service area, in accordance with an aspect of the present invention;

fig. 4 is a flow diagram depicting an added portion of an idle mode cell selection/selection process of an MS in order to handle a unique subscribed cell in accordance with an aspect of the present invention;

fig. 5 is a flow diagram depicting an added portion of an idle mode cell selection/reselection procedure for an MS in order to handle a subscription that has been allowed to access a restricted portion of a network in accordance with an aspect of the present invention.

Detailed Description

Various features of the invention will be described hereinafter with reference to the drawings, in which like parts are designated by the same reference numerals.

According to one aspect of the invention, a SIM card on a Mobile Station (MS) contains information identifying one or more allowed portions of a PLMN that a user of the MS is allowed to access, which information is used by the MS in idle mode to determine whether a cell is suitable for camping (i.e., whether the cell is within the allowed area) or not (i.e., whether the cell is outside the allowed portions of the PLMN).

By providing the MS with user service area information, the MS can estimate whether it is allowed to camp on any particular cell (i.e., for the purpose of making the user served) and can do so without instigating any communication with the network (i.e., without occupying any radio and network resources).

According to another aspect of the invention, different portions of the PLMN that the subscriber is allowed to access are prioritized on the SIM card on the MS. Using these lists may enable the MS to select which candidate cell should camp on, which may result in a camping decision that is different from that made in existing normal systems. For example, if two cells are found to be suitable for camping, a cell belonging to the part of the PLMN with a higher priority is selected according to the list on the SIM card, regardless of whether the cell has the highest signal strength, so that the frequency overhead of the cell is avoided or minimized.

A second benefit of the present invention is that by providing the MS with the user's service area priority information, the MS can select and camp on the most preferred cell (of the provided cells), as can be seen from a subscription point of view, and this can be achieved without causing any communication with the network (i.e. without occupying any radio and network resources).

In another aspect of the invention, the information broadcast on the cell radio control channel may contain information indicating that the cell is part of a PLMN, wherein access is allowed to be controlled by the subscription data. That is, only the designated users are allowed to access the cell. As mentioned above, the SIM may be programmed to include a portion that identifies a PLMN on which the MS is allowed to obtain service, so that the newly broadcast information is utilized by the MS in conjunction with the new SIM information to determine whether the cell is suitable for camping.

In another aspect of the invention it is recognised that in practice an existing (normal) MS (i.e. an MS which does not support the new functionality) may coexist with the MS described herein, so that in order to prevent an existing MS which does not support the new functionality from camping on a cell which is controlled by subscription data to allow access, this cell may be prevented according to existing techniques, defined by existing TS GSM03.22 standards such as the ETSI publication, which is hereby incorporated by reference. In this case, an MS supporting the new functionality described herein ignores this "cell barring" information if the cell belongs to a part of a PLMN for which access is allowed under the control of subscription data. The MSs may camp on the cell if the subscription service area data indicates that the cell allows the subscription.

By broadcasting information indicating that a given cell is restricted to users whose subscription data specifies that the given cell is a cell to which they are allowed to access, the MS is enabled to estimate whether the cell is allowed to camp on to obtain user service. This benefit can be obtained without causing any communication with the network, i.e. without occupying any radio and network resources, in combination with other aspects of the invention.

Various aspects of the invention will be described in greater detail with reference to exemplary embodiments. Referring first to fig. 1, an exemplary service area is defined by microcells 101, 102 and 103, and the macrocell 10 covers this service area. When an MS (not shown in fig. 1) is powered on, the C1 standard, as determined by the 4.18.2 version of TS GSM05.08, published by ETSI and written herein by reference, finds the most suitable for camping cells, which need not be cells within the service area, since these cells have only a very limited coverage according to the C1 standard. The TS GSM05.08 specified C2 standard is activated after a few seconds and performs cell reselection.

All MSs use the above cell selection and cell reselection when in idle mode, regardless of the particular SIM inserted in the MS (i.e., independent of the subscription data).

Referring again to figure 1, assuming that the exemplary service area determined by the mini-cells 101, 102 and 103 is the preferred service area for employees of a particular company, this function may be accomplished, according to one aspect of the invention, by having each employee receive subscription data indicating that the service area is the preferred area, that is, the SIM card (MS for those employees to use) is programmed to store information identifying the preferred service area.

Fig. 2 is a block diagram of a mobile station 201 including components to implement various aspects of the present invention, such as a SIM105 containing PLMN access information as described herein, and a processor 103 for controlling PLMN access in accordance with various techniques taught herein. Of course, those skilled in the art will recognize that the mobile station 201 will also contain many other components in order to interact with the conventional portions of the PLMN. To complete the preferred service area for the employee in the above example, the processor 103 may perform a process such as the flowchart of fig. 3, fig. 3 being a flowchart depicting the portions that need to be added in the cell selection/reselection process to include the processing of the reserved preferred area data in accordance with an aspect of the present invention.

The existing criteria for selecting a cell in a GSM system, which is performed by all MSs in idle state, is based on a parameter called C1. According to known techniques, the MS finds all Radio Frequency (RF) channels defined for the mobile system (one RF channel per cell) and measures the received RF signal strength on each RF channel, and then the MS calculates an average received level on each RF channel based on a number of measured samples of each RF channel spread over a period of time. A parameter C1 is then calculated for each RF channel (i.e., for each cell), the parameter C1 being based on the average of the received levels and the minimum signal strength level set by the network. The cells are prioritized in descending order of C1, and the MS typically camps on the cell at the top of the list.

According to one aspect of the invention, the above technique is modified to take into account the priorities of the service areas, in particular, after calculating the C1 values for each cell and deciding which cells are suitable for camping, the cells are first prioritized so that those cells belonging to the user service area (as defined by the data of the SIM 205) are given a higher priority than those cells not belonging to the user service area (step 301).

Next, in each cell category (i.e., serving area versus non-serving area), these areas are prioritized by a decreasing value of C1 (step 303), and MS201 then finds out and camps on a cell among the cells with decreasing priorities (step 305). Then, the cell selection/selection process continues according to known techniques, which are not described in detail herein.

Viewed from another aspect of the present invention, the MS may avoid interfering with radio frequency planning in the network by further introducing a new parameter, referred to herein as a "quality assurance parameter", which prevents the MS201 from camping on a cell whose C1 value is much smaller than the highest C1 value associated with any other cell, i.e., the quality assurance parameter is defined as the maximum difference allowed between deciding the highest C1 value of one cell and experimentally choosing the C1 value of a "preferred" cell, and so, not choosing the "preferred" cell.

The new quality assurance parameter values may be obtained in a number of ways, e.g. defined by the mobile system's standards and then stored at the MS201, alternatively it may be characteristic of the cell and determined by the network operator, in which case the quality assurance parameters should be broadcast in each cell so that the MS can read it while in idle mode. In another alternative, the quality assurance parameter value may be characteristic of the cell and determined by the network operator, in which case the parameter value may be stored with the subscription service area data, such that the parameter value and service area data are available to the MS 201.

Considering now one aspect of the present invention, it is desirable to ensure that there is a minimum communication capacity envisioned, such as the number of company employees, given that an operator wishes to provide wireless network coverage at a company's premises. It is further assumed that to achieve this guarantee, the network operator has to pre-establish a certain number of cells dedicated for the use of company employees. For example, referring to fig. 1, a corporate premises may be served by private microcells 121 and 122 residing within the macrocell 12, it being seen that the macrocell 12 also contains other microcells such as microcells 120, 123, and 124. Under conventional systems, such reservations pose a problem because there is no way to prevent non-employee users entering the coverage area of "private" cells (e.g., microcells 121 and 122) from camping on these cells and occupying radio resources, and therefore, using communication capacity is contemplated for exclusive use by only company employees.

According to one aspect of the invention, this problem is solved. Wherein the MS used by a particular user group considers the private cell, referred to herein as the "uniquely visited cell", as "allowed" and given the highest priority. By comparison, the existing MSs in the system (i.e., the MSs used by the other user groups) will no longer consider these cells as "allowed" and will not use/camp on these cells.

In accordance with this aspect of the invention, the "unique subscribed cells" (e.g., microcells 121 and 122) broadcast information indicating that these cells are dedicated for use only by those subscribers whose subscription data indicates that these cells are "allowed", which information is used by the MSs in each system to determine whether a cell is suitable for camping and registering.

As mentioned previously, existing (legacy) MSs (i.e., MSs that do not support the new functionality) may co-exist with the new MSs described herein. Thus, in order to prevent an existing MS that does not support the new functionality from camping on a cell of allowed access controlled by subscription data, the cell may be prevented according to the prior art defined by existing standards such as TS GSM03.22 published by ETSI. If they are detected. In addition to the conventional "cell barring" indication, the cell broadcasts new information indicating that the cell belongs to a part of the PLMN, where the allowed access is controlled by the subscription data, in which case the MS supporting the new functionality described herein ignores the "cell barring" information. The MSs may camp on the cell if the subscription service area data indicates that the cell is allowed.

No new software or hardware is required to support the unique access cell for an existing (legacy) MS, since the cell will be blocked according to known techniques, (the "unique access cell" indication from the cell will be understood by the legacy MS and ignored). For a new MS, additional steps such as the flowchart shown in fig. 4 should be performed as part of the idle mode cell selection/reselection process. In particular, fig. 4 shows the steps performed by the processor 203 when a cell transmits "cell barring" information according to known techniques. Despite the "cell barring" information, MS201 determines whether the cell is suitable for camping/registering (decision block 401). If not, the cell is excluded from further consideration and the cell selection/reselection procedure continues (step 409).

If the cell is suitable for camping/logging on, a test is made to determine if the cell is uniquely visited (decision block 403). That is, MS201 determines whether the cell broadcasts a new "unique access cell" indication in addition to the standard "cell barring" indication. If it is not broadcast, the cell is otherwise blocked and the cell selection/reselection procedure continues (step 409).

If the cell is for unique access, a test is made to determine if the particular cell belongs to the user's allowed service area (decision block 405). To perform this step, the processor 203 accesses the subscriber information stored on the SIM205 and compares the cell identification numbers with the received information identifying the cells to establish an allowed service area.

If the particular cell belongs to the user's allowed service area, it is added to the list of suitable cells (step 407) and the cell selection/reselection procedure continues (step 409). For example, cell selection (to camp on/register) may continue in accordance with conventional techniques. Alternatively, referring to fig. 3, the list of suitable cells may be arranged as described above. In the latter case, the subscription service information may be used in part to order the last list of suitable cells.

Consider now another scenario in which a network operator wishes to provide a subscription that is only allowed to access a defined part of the network. For example, consider the macrocell 14 depicted in fig. 1. It includes microcells 110, 111, 112, 113, 114, 115, and 116. It is assumed that it is desirable to allow only a certain user to access the service area defined by the microcells 114, 115, and 116. This is not possible in conventional systems because such systems do not prevent the MS from camping on a cell that is outside of the allowed area, which is determined by the function of the subscription information.

According to another aspect of the present invention, this problem is solved in that the MS will not perform a general camping on a cell if the cell is outside the allowed area set by the subscription service data stored in the sim 205. Fig. 5 is a flow chart depicting particular exemplary steps that may be incorporated into an MS idle mode cell selection/reselection procedure to handle a subscription that allows access in a defined portion of the network. In particular, after discovering a cell suitable for camping/logging on, the processor 203 in the MS201 accesses information in the SIM205 to determine whether the user has access to only a limited portion of the network (decision block 501). If not, the cell is added to the list of suitable cells (step 505) and the cell selection/reselection process continues (step 507).

If the cell does not belong to the user's allowed area ("No" leg of decision block 503), then the cell is No longer considered as a suitable candidate and the cell selection/reselection process continues directly (step 507).

Turning now to another aspect of the present invention, in order for the MS201 to determine whether a cell belongs to a service area in which a user of the MS201 has the right to allow/prioritize access, information defining the service area must be defined. For this purpose, there are two alternatives as follows:

in a first alternative, the service area may be defined by a service area identification. Service area identities are broadcast in the cells that make up the service area. For example, the mini-cells 101, 102 and 103 (see figure 1) will broadcast the same service area identification. The MS201 can obtain the service area identification number of one (or all) cells and compare this service area identification number to the subscriber service area information (e.g., service area list) stored in the SIM 205. This scheme is advantageous in that it is less dependent on changes in the wireless network. For example, adding a cell to the service area does not create any need to update the user service area information in MS 201. Also, the storage length of the memory in the SIM205 for storing the user service area information is independent of the number of constituent service areas.

In a second scheme, the service area is defined by a list of cell identification numbers. In this case, no special service area identification is broadcast for the cells making up a single service area. For example, each of the mini-cells 101, 102 and 103 (see fig. 1) broadcasts its own cell identification number, even though, in general, they constitute a single service area. The MS201 receives these respective cell identification numbers and compares them to a list of service area cell identifications (e.g., subscriber service area information stored in the SIM 205). This solution is advantageous in that since the cell identity is already broadcast in the cell, there is no need to broadcast additional identity information in the cells belonging to the service area.

The above technique relies on subscriber service area information stored on the SIM 205. There are several alternative embodiments that may provide such information to the SIM 205. In one arrangement, the network operator or service provider may pre-program the SIM205 before handing it to the user. This has the consequence that the user must return the SIM205 to the network operator or service provider for updating if the information is to be changed for some reason, but this solution has the advantage that it reduces the interference with the operation of the network and is potentially more secure.

In an alternative embodiment, the user's service area information may be stored in a database (e.g., the user's local storage or other service node) within the mobile network. When a user first logs on to the network after establishing the user service area information or after the user service area information is changed, the network will send the information to MS 201. The benefits of this arrangement include that changes to the user service area information require only simple processing by the operator, service provider or end user, without defining actions.

The above-described techniques involve the use of service area information when the MS is in idle mode. When the MS is actively in contact with the network, the network may use the user service area information to make a handover decision (i.e., to decide which cell may be a candidate for taking over responsibility for the ongoing call). Techniques for using subscriber service area information in this manner are described in U.S. patent application No.08/872,065, entitled "tailor structural Cell Structures in Communications System," and filed on 10/6 1997 in the name of Tomas Fried et al.

The invention has been described with reference to a specific embodiment. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other specific ways than the preferred embodiments described above. This can be done without departing from the spirit of the invention. The preferred embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is given by the appended claims, rather than the preceding description, and all variations and equivalents which fall within the range of the claims are intended to be embraced therein.

Claims

1. A mobile communication device for use in a communication system comprising a public land mobile network and being divided into a plurality of cells, comprising:

a wireless device for contacting a public land mobile network;

means for determining whether any one cell is part of a predetermined service area in which the mobile communication device is permitted to use a cell and at least one other mobile communication device in the communication system is not permitted to use a cell within the predetermined service area, wherein information identifying the different parts of the public land mobile network to which a user is permitted access is stored in said mobile communication device, which information is used by said mobile communication device to compare in idle mode with cell information broadcast from a cell to determine whether said mobile communication device is camped on the cell.

2. The mobile communication device of claim 1, wherein the means for determining whether any one of the cells is part of a predetermined service area comprises memory means for storing information regarding which of the cells are part of the predetermined service area.

3. The mobile communication device of claim 2, further comprising:

means for determining a list of suitable cells to camp on;

means for selecting one of the suitable cells by giving higher priority to cells that are part of the predetermined service area than to cells that are not part of the predetermined service area.

4. The mobile communication device of claim 3 wherein the means for determining whether any of the cells is reserving a portion of a service area further comprises means for receiving information about the cells broadcast from a cell in the communication system on a radio control channel.

5. Method in a communication system divided into a plurality of cells, comprising the steps of:

broadcasting information about a cell from at least one cell;

receiving information on a cell from at least one cell;

6. The method of claim 5, wherein storing information in said mobile communication device about which cells are within a predetermined service area, and using said received information about cells to determine whether said at least one cell is part of the predetermined service area comprises: the stored information about which cells are in the predetermined service area is retrieved.