Communication infrastructures suitable for mobile users (in particular, though not exclusively, Public Land Mobile Networks, PLMN, in the form of cellular radio infrastructures) have now become widely adopted. Whilst the primary driver has been mobile telephony, the desire to implement mobile data-based services over these infrastructures, has led to the rapid development of data-capable bearer services across such infrastructures. This has opened up the possibility of many Internet-based services being available to mobile users.
Data-capable bearer services can be provided, for example, by a Short Message Service (SMS), by using a voice traffic circuit for data, or by using specialised data facilities such as provided by GPRS for GSM PLMNs (GPRS—General Packet Radio Service—enables IP (or X.25) packet data to be sent through the PLMN and full details of GPRS can be found in the ETSI, European Telecommunications Standards Institute, GSM 03.60 specification).
The availability of data-capable services to mobile devices has led to the development of suitable operating environments and applications; of particular note in this connection is the “WAP” (Wireless Application Protocol) standard. Details of WAP can be found, for example, in the book “Official Wireless Application Protocol” Wireless Application Protocol Forum, Ltd published 1999 Wiley Computer Publishing. Where a PLMN is WAP enabled, the data-capable bearer service involved will be routed to the outside world via a WAP proxy gateway.
A number of technologies also exist for the short range wireless communication of information to and between mobile devices. These technologies include infra-red based technologies and low-power radio technologies (including, in particular, the recent “Bluetooth” short range wireless standard). Depending on the technology implementation, differing types of message propagation will be enabled including asynchronous message broadcast, and multicast and point-to-point duplex connections established after coordination and negotiation between communicating devices.
The increasingly widespread deployment of the foregoing technologies in mobile devices has led to an increased interest in ways of determining the location of mobile devices, primarily with a view either to providing user-location information to emergency services or to enabling the provision of location-aware information services. A number of methods exist for determining the location of a mobile user as represented by an associated mobile equipment. Some of these methods result in the user knowing their location thereby enabling them to transmit it to a location-aware service they are interested in receiving; other of the methods result in the user's location becoming known to a network entity from where it can be supplied directly to a location-aware service (generally only with the consent of the user concerned). Two known approaches to location determination are described briefly below with reference to FIGS. 1 and 2 of the accompanying drawings, both approaches having in common the fact that the location of the mobile device is derived from a knowledge of the location of fixed infrastructure elements.
FIG. 1 shows how location determination can be effected using local, fixed-position, beacons here shown as infra-red beacons IRD though other technologies, such as short-range radio systems (in particular, “Bluetooth” systems) may equally be used. The right hand half of FIG. 3 show a number of independent beacons 13 that continually transmit their individual locations. Mobile entity 11A is arranged to pick up the transmissions from a beacon when sufficiently close, thereby establishing its position to the accuracy of its range of reception. This location data can then be appended to a request 17 made by the mobile entity 11A to a location-aware service available from service system 40, the request being sent over any suitable communications infrastructure 10 (for example, a PLMN where entity 11A has cellular radio capability, the service system being connected directly to the PLMN or via a network such as the Internet). A variation on this arrangement is for the beacons 13 to transmit information which whilst not directly location data, can be used to look up such data (for example, the data may be the Internet home page URL of a store housing the beacon 13 concerned, this home page giving the store location—or at least identity, thereby enabling look-up of location in a directory service).
In the left-hand half of FIG. 1, the IRB beacons 12 are all connected to a network that connects to a location server 15. The beacons 12 transmit a presence signal and when mobile entity 11B is sufficiently close to a beacon to pick up the presence signal, it responds by sending its identity to the beacon. (Thus, in this embodiment, both the beacons 12 and mobile entity 11B can both receive and transmit IR signals whereas beacons 13 only transmit, and mobile entity 11A only receives, IR signals). Upon a beacon 12 receiving a mobile entity's identity, it sends out a message over network 14 to location server 15, this message linking the identity of the mobile entity 11B to the location of the relevant beacon 12. Now when the mobile entity wishes to invoke a location-aware service provided by the service system 40, since it does not know its location it must include it's identity in the service request 16 and rely on the service system 40 to look up the current location of the mobile entity in the location server 15.
FIG. 2 depicts two general methods of location determination from signals present in a cellular radio infrastructure, PLMN 25. However, first, it can be noted that in general both the mobile entity and the network will know the identity of the cell in which the mobile entity currently resides, this information being provided as part of the normal operation of the system. (Although in a system such as GSM, the network may only store current location to a resolution of a collection of cells known as a “location area”, the actual current cell ID will generally be derivable from monitoring the signals exchanged between a Base Station Controller, BSC, and the mobile entity). Beyond current basic cell ID, it is possible to get a more accurate fix by measuring timing and/or directional parameters between the mobile entity and multiple BTSs (Base Transceiver Stations), these measurement being done either in the network or the mobile entity (see, for example, International Application WO 99/04582 that describes various techniques for effecting location determination in the mobile and WO 99/55114 that describes location determination by the mobile network in response to requests made by location-aware applications to a mobile location center—server—of the mobile network).
The left-hand half of FIG. 2 depicts the case of location determination being done in the mobile entity 11C by, for example, making Observed Time Difference (OTD) measurements with respect to signals from BTSs 18 and calculating location using a knowledge of BTS locations. The location data is subsequently appended to a service request 21 sent to service system 40 in respect of a location-aware service. The calculation load on mobile entity 11C can be reduced and the need for the mobile to know BTS locations avoided, by having a network entity do some of the work. The right-hand half of FIG. 2 depicts the case of location determination being done in the network, for example, by making Timing Advance measurements for three BTSs 18 and using these measurements to derive location (this derivation typically being done in a unit associated with BSC 19). The resultant location data is passed to a location server 20 from where it can be made available to authorised services. When the mobile entity 11D of FIG. 2 wishes to invoke a location-aware service available on service system 40, it sends a request 22 to the service system 40; the service system then obtains the current location of the mobile entity 11D from the location server 20.
It has also been proposed to geographically route messages to mobile devices. The paper “Geographic Addressing, Routing and Resource Discovery with GPS” (Tomasz Imielinski and Julio C. Navas; Computer Science Department, Rutgers, The State University Piscataway, N.J.) describes various geographic routing applications including geographic e-mail, geographic broadcasting, and geographically directed multicasting, for example, to all police cars in a specified area. In one described arrangement, “geonodes” provide entry/exit points to a geographic routing system which comprises “georouters” that know which geonodes cover which areas and therefore can make routing decisions for messages that are being geographically routed. The paper also describes a DNS (Domain Name System) solution for geographic routing. The methods described in this paper are not directed at how a mobile entity may obtain its own location.
Also of interest as prior art relevant to the present invention is the “Traceroute” utility for identifying intermediate nodes along a communication path established through an IP (Internet Protocol) network. The operation of this utility is illustrated in FIG. 3 and relies on the fact that a time-to-live field, generally operating as a “hops-remaining” counter, can be set in an IP datagram and when this field is decremented to zero by a receiving node, the latter will return an ICMP message to the source entity, this ICMP message carrying the sending node's IP address as its source address. More particularly, in FIG. 3 a communications path is depicted between a source node 31 and a destination node 32, this path passing through three intermediate nodes 33 (IP routers N1, N2 and N3). In order to identify these intermediate nodes, the source node 31 repeatedly sends a datagram addressed to destination node 32 but with the time-to-live (TTL) field set successively to 1, 2, 3 and 4. The first of these datagrams 34 (TTL=1), on reaching node N1 is not sent on but causes node N1 to return an ICMP “time exceeded” message 35 to the source node 31. The second datagram 36 (TTL initially equal to 2) passes through node N1 without problem but has its TTL field decremented to 1; on reaching node N2, a “time exceeded” ICMP message 37 is returned to source node 31. The third datagram 38 (TTL initially set to 3) passes through nodes N1 and N2 before being stopped at node N3 which returns a “time exceeded” ICMP message 39 to source node 31. Finally, the source node 31 sends a datagram 30 with TTL=4 and this reaches destination node 32.
It is an object of the present invention to provide location information about a communicating entity that can take advantage of communication infrastructure elements that are not of themselves location aware.