Method for defining a zone for location based billing and/or location based services

The present invention is directed to a method for defining a zone for location based billing and/or location based services, wherein the zone is a part of a geographical area which is served by nodes of a telecommunications network such as a telecommunications network according to the GSM or UMTS standard.

Operators providing service over an air interface medium may provide service differentiation to their end users based upon location. The location is physically defined by a communicated geographical area which is assimilated by the operator into a radiation footprint propagated by nodes which provide communication to and from the terminal devices such as cell phones of the end users.

The end user is aware of being located in such location or zone through a distinct indication, for example visually or audibly and/or through differentiation in the billing and/or through use differentiation in service experience, e.g. higher output, privileged service capabilities regarding the use of the terminal device.

For any given location the effective boundaries change over time due to subsequent topological change to the network node infrastructure, i.e. new rollout, rede-

ployment or physical removal. Over time the network-operator must continually reassess and re-communicate the location to the affected end user over time.

It is the object of the present invention to define a zone for location based billing and/or services that optimally anticipates future undisclosed topology evolutions and hence minimises the occurrence of updating existing end user location definitions.

This object is solved by a method defined in claim 1 and by a system defined in claim 12.

According with the invention the method comprises the steps of:

a) defining a zone within the geographical area,

b) determining all serving nodes of the telecommunications network which serve said zone defined in step a),

c) determining an initial area whose geographical perimeter envelopes the physical location of said serving nodes,

d) determining a density vector which has its basis in the centroid of said initial area defined in step c) and which points into the direction of the smallest density of said serving nodes being located in said initial area and

e) determining a final area which has its centroid on said density vector and which is enlarged compared to the initial area so that no serving nodes are located in said final area which are not located in said initial area, wherein the final area is said zone for location based billing.

For example a database maintains a physical location attribute of all nodes resident in the network offered by the network provider to the end user.

According to step b) all node members who are considered as delivering the location are defined, i.e. all serving nodded are identified.

In step c) a so called initial area is defined whose geographical perimeter envelopes the physical location of said serving nodes. This initial area may have any shape such as a polygon or a circle.

According to step d) a density vector is determined which has its origin at the cen- troid of the initial area. The direction of this vector points towards the area of lowest density of serving nodes, i.e. to the least densely serving node-populated area of the initial area.

In step e) the maximum size of a final area is determined that can be achieved so that there is preferably no modification to the relative shape of the initial area to the final area, wherein the centroid of the final area is located on said vector and wherein the final area shall not envelope any non-serving node.

The final area thus exhibits the following characteristics:

• it envelopes the same nodes as the initial area, these being the nodes required that point of the network node topology to describe the location

• enveloped nodes may lie at a non-zero distance from its perimeter, which gives some tolerance of movement to these nodes without requiring a redefinition of the location

• non-enveloped nodes which through re-positioning are most likely to become serving nodes are given maximum freedom of movement to be enveloped, since the perimeter of the final area may lie close to their present position. Non-enveloped nodes which through re-positioning are less likely to become serving nodes are given less freedom of movement to be envel-

oped because the perimeter of the final area generally lies further from their present position.

• the final area envelopes an area which considering the positions of existing nodes represents the most likely area in which new cells also serving the location will be incorporated without requiring a redefinition of the location.

The above mentioned initial area and the final area may have the shape of a circle. However, any other shape is also conceivable.

The zone defined in step a) may be a circle centered on a defined location, in particular on an address of the user of the telecommunications network. The circle my have a predefined radius. For example the zone is a circle having a radius of 500 m and being centered at the home or office address of the user. All nodes which provide radio coverage in part of this area are considered as serving nodes. The circle is extended, but centroid is not moved, such that the radius touches the furthest away serving node. This larger circle is considered as the initial area.

In accordance with a further embodiment of the invention the density of said serving nodes is defined by the proximity of these nodes inside the initial area to one another and to the centroid of the initial area. Thus the density vector points towards the area which is least densely populated by the service nodes of the initial area.

In accordance with a preferred embodiment of the invention the density vector points into a direction which may be determined as follows:

• defining a reference line passing through the centroid of the initial area,

• determining the angle φi between a line connecting the centroid of the initial area with a serving node i and the reference line for each of said serving nodes being physically located within the initial area

• determining the distance η between the physical location of each of the nodes i being physically located within the initial area and the cen- troid of the initial area and

• determining the angle φv _ecto r between said reference line and the density vector by the following formula: φvector = σ (φi n) / ∑ n + π, wherein the summations are performed for all serving nodes i which are located within the initial area.

The initial area may be determined such that it is the smallest area which just covers the serving nodes determined in step b). The initial area may have the shape of a circle which has a radius such that the serving node having the greatest distance to the centroid is just enveloped or lies on the perimeter.

The final area may be determined such that it is the largest possible area which does not include any non serving node determined in step b). It is also conceivable that the final area is enlarged such that a non serving node lies on the perimeter thereof.

In case that two network mediums are offered by a network provider such as GSM and UMTS the method for defining a zone for location based billing is performed for each of said mediums independently. In other words the method according to the invention is performed for the GSM network as well as for the UMTS network, the result of which are two final areas, one for each of the networks.

In order to obtain an "overall" consolidated area it is possible to define such area having its centroid at the median point one the line connecting the centroids of the final areas determined for each of the network mediums and have a shape expanded such that it envelopes the final areas determined for each of the network

mediums. In this case additional non-serving nodes may by subsumed into the consolidated area and these nodes shall be considered also as serving the location.

The invention is further directed to a system or apparatus comprising means for performing the method according to any one of claims 1 to 12. These means for example may comprise databases for storing physical location attributes of all nodes resident in the network and means for performing each of the steps by which the method claims are defined such as computing means for performing steps b) - e) of claim 1.

Further advantages of the invention are explained on the basis of the exemplary embodiment shown in the drawings. The figures show:

Fig. 1 : The initial area determined in step c)

Fig. 2: the way to determine the direction of the vector (left hand picture) and the initial area together with said vector (right hand picture)

Fig. 3: the final area determined in step e) and

Fig. 4: a consolidated area in case of two network standards being available.

An operator defines a location to a subscriber in GSM and UMTS access networks such that serving nodes are identified as being those which provide radio coverage within a predefined distance to a given address (geographical latitude and longitude).

An initial area which is shown in Fig. 1 as circle is subscribed which just envelopes the serving nodes in GSM, i.e. one or more nodes lie on the circle.

As shown in Fig. 1 two nodes lie within the initial area which is the smallest circle which envelopes the physical locations of the serving nodes of a predefined location.

Two further nodes are determined as not being serving nodes.

In the next step a density vector is calculated by a distance-weighted / angular formula φ _vector = σ (φi π) / X η + π, wherein the angle φi is the angle between a line connecting the centroid of the initial area with a serving node i and a reference line for each of said serving nodes being physically located within the initial area and wherein η is the distance between the physical location of each of these nodes i and the centroid. The reference line is shown in Fig. 2 (left hand part) as vertical line which runs through the center of the initial area.

Referring to the example shown in Fig. 1 and Fig. 2 (right hand part) there are just two nodes which both lie a similar distance from the centre. Hence the density vector points towards a direction which is opposite the average polar angle of the two.

In a next step the centroid of the polygon, in the present example the centre of the circle is moved on the above determined vector whereby the size of the polygon is increased which is shown in Fig. 4 by a series of increasingly larger broken circles.

The largest possible circle which does not envelope additional, i.e. non-serving nodes is set as the final area which is defined as the zone for location based billing and/or services.

Fig. 5 refers to an example in accordance to which two network standards are available. In this case the method described above is performed for each of these standards, i.e. in the present example for GSM and UMTS. The result are two circles having differing centres and differing sizes. The consolidated area is depicted in the figure as the largest broken circle whereas the inner, smaller broken circles are the final areas of the respective network standards.

The consolidated area is defined by having its centroid as a median of the centroids of the final areas of the respective networks and by having a dimension so that both initial areas of the respective networks are enveloped as shown in Fig. 5.

In this case all nodes, in the present example GSM or UMTS which are physically inside the consolidated area are considered as serving the location.