WO2002051173A2

WO2002051173A2 - System and method for communicating data messages from a cell phone terminal, such as a geographical location

Info

Publication number: WO2002051173A2
Application number: PCT/US2000/034434
Authority: WO
Inventors: Ahmad Lamah
Original assignee: Gatco
Priority date: 2000-12-19
Filing date: 2000-12-19
Publication date: 2002-06-27
Also published as: AU2001222781A1; WO2002051173A3

Abstract

A system and method is provided for communicating at least one data message from a cellular telephone terminal through a communications network, comprising at least one cellular telephone terminal having an identification electronic serial number (ESN). To this end, the cellular telephone terminal comprises means for sending the data message in the form of an electronic serial number having a format substantially the same as that of its identification electronic serial number, the system having a set of electronic serial numbers allocated for use as data messages in the form of electronic serial numbers for communicating information other than the identification number of the cellular telephone terminal.The data message sent by the cellular telephone terminal can be variable as a function of a user choice or operating condition of the terminal, and can advantageously correspond to location information expressing a geographical position of the cellular telephone terminal.

Description

SYSTEM AND METHOD FOR COMMUNICATING DATA MESSAGES FROM A CELL PHONE TERMINAL. SUCH AS A GEOGRAPHICAL LOCATION

Background of the invention 1. Field of the invention

The present invention relates to mobile telecommunications, and more particularly to a way of sending data messages from cellular telephone terminal, e.g. for automatically sending information concerning a caller's geographical location to a destination point linked to the telephone network.

2. Prior art

Cellular (or mobile) telephones have rapidly become a widespread means of personal communication, not only for standard telephony, but also for exchanging data messages through an ever-increasing range of different services. By its very nature, a cellular phone call number cannot be ascribed to a permanent geographical location, by contrast with a fixed, cable telephone terminal access point. This means that the techniques currently used for physically locating the origin of a telephone call with a fixed access point cannot be employed for cellular telephones. Yet the ability to locate a call from a cellular telephone, notably in emergency situations, can provide tremendous assistance in many outdoor and indoor situations. Indeed, the cellular phone terminal can then take on a new function as a lifeline when its user is in peril (assault, accident, loss of direction, etc.).

Aware of this potential, the Federal Regulations have now imposed that US wireless telephone network operators offering services for Public Answering Service Points (PSAPs) must also be able to communicate the position of a calling party during an emergency call to the appropriate emergency authority, e.g. a nearby police station or fire department. As from

October 1, 2001, it will be required that a cellular telephone terminal shall be locatable within a range of less than 125 meters using a root mean square (rms) methodology.

Various proposals have been contemplated in view of meeting this requirement. Patent document US-A-5 873 040, for instance, discloses a wireless 911 emergency location system in which several mobile switching offices share a common database. In order to locate a caller, the strength of the received signal is measured at a base station communicating with the calling cellular phone. The measured signal value is passed through the switching offices to a shared computer to calculate a search area. A large-scale map corresponding to that area is provided to the emergency assistance center. This approach, which depends on analog signal parameters, is subject to substantial inaccuracies on account of such variables as instantaneous reception conditions, interference, signal strength at the transmitting aerial, etc. European patent application EP-A-0 897 119 discloses a cellular transmitter for automatically providing position location and emergency information. The mobile telephone set comprises a global positioning system (GPS) terminal device from which the location of the caller can be obtained in terms of geographical coordinates. A stored telephone number is transmitted to a switching office together with the position data. Co-pending US patent application 09/022558 entitled "System and method for communicating information through a telephone network" filed on February 12, 1998 discloses a system for communicating a position of a mobile object having a cellular transceiver. The position data are transformed into one or more of a multitude of assigned telephone numbers. The telephone numbers correspond to location information to be transmitted to a switch using the "callback" or direct inward dialing (DID) service. The transmission of each DID number is accomplished during the handshake when the calling telephone set is establishing the communication link to the switch as long as the connection in not yet fully established, which means that the switch is still "on hook". As a result, communication charges are avoided. A set of DID telephone numbers is obtained from the telephone network operator on a rental basis for a fixed, e.g. monthly, fee.

Co-pending US patent application 09/345548 contemplates a "911" emergency location system which uses DIDs as a way to send location information from a cellular telephone to a 911 Emergency Office or a Public Safety Answering Point (PSAP). The location information is derived from a GPS terminal built into a mobile telephone terminal which is coupled to a transforming unit that generates signals according to a DID format corresponding to a geographical location. A territory is thus divided into sectors, to each of which is assigned a "location DID".

Summary of the invention with objects It is an object of the invention to allocate a set of electronic serial numbers (ESNs) - the set possibly counting up to millions of ESNs depending applications and embodiments - to be used for sending data messages. These data messages can be sent in short bursts and made to correspond to positioning information, for instance, the information being obtained e.g. from GPS satellites. The data messages can however be used to convey other information.

It is also an object of the invention to facilitate and simplify the transmission of an emergency call from a cell phone to a public service answering point (PSAP) by converting the ESN into a direct inward dialing (DID) format.

In an embodiment, when a call is made from a cell phone with positioning means, such as a GPS terminal, the call set-up is as follows: the cell phone sends the ESN that represents its identification (ID), then the mobile identification number (MIN) of the cell phone, then the ESN that represents its position, then the destination number, which could be the emergency number (911 ) or any other dialed number.

The DID may be sent instead of the ESN that represents the position along with the MIN to the proper authority, such as a PSAP, fire department, etc.

Part of the ESN can be made to have a phone number format (NPA, NXXX), or may be turned into a phone number format at the mobile telephone switch office (MTSO) or at the local exchange carrier (LEC).

There can be provided a dual ESN per MIN or cell phone: one ESN for emergency service, and the other for direction service.

There can be provided one set of DIDs but dual ESN or dual MIN: one for emergency setup and for location and direction setup. An object of the present invention is to allow cellular telephone terminals (hereafter referred to a cell phones) to send data messages such as location information to a remote point, e.g. a telephone network, using a data structure that corresponds in form to an electronic serial number (ESN) of the calling cell phone terminal. Thus, the invention proposes to ascribe a new function to ESNs by reserving a set of these numbers for data transmission, e.g. for the purposes of providing location information. In this case, the "location ESNs" correspond to respective geographical sectors and are processed in the transmission protocol in a manner at least partially analogous to a classical ESN.

By using the standard ESN format for these messages, the methodology and means required for handling the latter can be significantly simplified, both at the level of the cellular telephone terminal and at the level of the network.

More generally, the invention relates to system for communicating at least one data message from a cellular telephone terminal through a communications network, comprising at least one cellular telephone terminal having an identification electronic serial number (ESN), the cellular telephone terminal comprising means for sending the data message in the form of an electronic serial number having a format substantially the same as that of its identification electronic serial number (both notably having the same of bits), the system having a set of electronic serial numbers allocated for use as data messages in the form of electronic serial numbers for communicating information other than the identification number of the cellular telephone terminal.

The data message sent by the cellular telephone terminal can be variable as a function of a user choice or operating condition of the terminal, and may contain location information expressing a geographical position of the cellular telephone terminal.

Preferably, the data message is sent in short bursts over a control channel during a call set-up phase.

The cellular telephone terminal is preferably operative to send its identification electronic serial number, then its mobile identification number (MIN), then at least one the data message, and then a destination number.

A mobile identification number (MIN) of the cellular telephone terminal can be sent to a destination point along with said data message.

Format conversion means in may be provided at the communications network — for instance at the mobile telephone switching office (MTSO) or the local exchange carrier (LEC), for converting the data message from its format as an electronic serial number sent by the cellular telephone terminal into another format, such as a direct inward dialing (DID) format prior to forwarding location information contained therein.

Advantageously, the electronic serial number corresponding to the data message sent by the cellular telephone terminal comprises at least a part having a telephone number format. At least a part of the electronic serial number corresponding to the data message sent by the cellular telephone terminal may be converted into a telephone number format by one of: a mobile telephone switching office (MSTO) and a local exchange carrier (LEC).

Where the network so allows, the data message can be sent all along from the cellular telephone terminal through to an end point destination in the form of an electronic serial number. The invention also relates to a system for communicating a geographical location of a cellular telephone terminal through a communications network, comprising at least one cellular telephone terminal having an identification electronic serial number (ESN), the terminal being operative to acquire and send location data representative of its location to a receiving point of the communications network, wherein the cellular telephone terminal comprises means for sending the location data in the form of an electronic serial number having a format substantially the same as that of its identification electronic serial number, the system having a set of electronic serial numbers allocated for location information.

The electronic serial number format used for sending location information may contain an indication as to whether the location information is intended for an emergency service or a non-emergency service, e.g. in the form of a code contained in the electronic serial number used for location information, or by pre-assigning separate sets of electronic serial numbers containing location information respectively for use in emergency situations and in non-emergency situations.

Analyzing means may be comprised within the network for analyzing an electronic serial number containing location information sent by the cellular telephone terminal, e.g. for determining whether the electronic serial number containing location information corresponds to an emergency or a non-emergency situation and for forwarding location information contained therein to a specific service on the basis of the analysis.

Preferably, each electronic serial number containing location information corresponds to a specific one of a set of contiguous geographical zones, which can have an area such as to allow a location of a cellular telephone terminal to an accuracy of 50 meters or better. Each electronic serial number containing location information can correspond to a specific one of a set of elementary zones, and a territory can be divided into a plurality of blocks, each containing at least one cell tower. The elementary zones can then be defined within a said block, e.g. in terms of their relative positions within a block. This allows a duplication of the identification ESNs, the same ones being usable for different blocks. Thus, at least some of a set of electronic serial numbers containing location information are repeated for different blocks, a specific location being further specified by data indicative of its block.

The cellular telephone terminal can be provided with means for storing information relative to a map of said territory, blocks and elementary zones and means to determine from an absolute position a corresponding elementary zone identified according to a predetermined topology.

The invention also relates to a communications system operative with cellular telephones, the system disposing of electronic serial numbers allowing to identify individual cellular telephone terminals, wherein a set of the electronic serial numbers is allocated for the communication of data messages other than cellular telephone terminal identification data.

The invention also relates to a cellular telephone terminal for a communications system disposing of electronic serial numbers allowing to identify individual cellular telephone terminals, wherein a set of the electronic serial numbers is allocated for the communication data messages other than cellular telephone terminal identification data, the cellular telephone terminal comprising means for selectively sending at least some of the set of allocated electronic serial numbers to convey a message.

The physical position may be determined by a GPS positioning device, the terminal having means for converting coordinate data supplied by the device into a format of electronic serial number corresponding to that position.

The cellular telephone terminal can comprise a look-up table containing a set of electronic serial numbers allocated to location information and means for assigning a specific one of the allocated electronic serial numbers in response to information indicative of the physical position of the terminal.

The invention also relates to a method of communicating at least one data message from a cellular telephone terminal through a communications network comprising at least one cellular telephone terminal having an identification electronic serial number (ESN), wherein the data message is sent from the cellular telephone terminal in the form of an electronic serial number having a format substantially the same as that of its identification electronic serial number, the system having a set of electronic serial numbers assigned for use as data messages in the form of electronic serial numbers for communicating information other than the identification number of the cellular telephone terminal.

The invention also relates to a method of communicating a geographical location of a cellular telephone terminal through a communications network comprising at least one cellular telephone terminal having an identification electronic serial number (ESN), comprising the step of:

- acquiring, at the level of the cellular telephone terminal, location data representative of the location of the terminal, - setting the location data into a format of an electronic serial number substantially the same as the format of its identification electronic serial number, a set of electronic serial numbers being pre-assigned for location information, and - sending the location information in the format of an electronic serial number.

The various embodiments and possibilities disclosed herein in the context of a system are applicable to the above methods mutatis mutandis.

As shall be described in more detail, the preferred embodiment uses ESNs to send position information in small bursts of data from the cell phone to the cell tower, and then either continue sending the ESN to the PSAP using SS7 network or other appropriate means. The ESN that represents the data may also be sent to the MTSO; then the MTSO transfers that data into a phone number format (DID) and sends it to the PSAP. The reason for this alternative is that sometimes the SS7 or comparable network does not exist, whereupon the only means of communicating the position information is through the DID. The position information represented by the ESN is received e.g. from a GPS terminal device located inside the cell phone.

Brief description of the figures

Other characteristics and advantages of the invention shall become apparent from reading the following description of the preferred embodiments, given purely as non-limiting examples, in conjunction with the appended drawings in which :

- Fig. 1 is a simplified schematic diagram showing the basic organization of a cell phone location system according to a preferred embodiment of the invention;

- Fig. 2 is a flow chart showing process steps involved in transmitting location information from a cell phone terminal to a service point in accordance with a preferred embodiment of the invention; and

- Figs. 3a and 3b are symbolic representations showing the division of a territory into blocks and elementary zones, the latter corresponding to a location ESN in accordance with a preferred embodiment of the invention.

Detailed description of the preferred embodiments

Referring to Fig. 1, the cell phone location system 1 operates in conjunction with cell phone terminals 2 of the type equipped with a GPS terminal device. In the figure, the GPS terminal device is integrated into the cell phone terminal housing and uses a miniature satellite receiving aerial 4 for receiving position signals from an array of geostationary satellites 6. In alternative embodiments, the GPS terminal device may be housed in a separate portable unit and connected to the cell phone terminal 2 by a wire or wireless link. The cell phone terminal 2 sends and receives telephone signals with a nearby cell tower 8 through its antenna 10 using standard telecommunications channels. The cell tower 8 acts as a relay between the cell phone terminal 2 and a mobile telephone switch office (MTSO) which serves as an interface between fixed and mobile (cellular) telephone networks. The MTSO 12 is operatively connected to a local exchange carrier (LEC) 14 which ensures the flow of telephone communications through different operators. The LEC 14 is connected inter alia to two utilities: a public safety answering point (PSAP) 16 that handles emergency situations, such as a police station or fire department, and one or a group of location services 18 that handle non-emergency situations. The PSAP or location services constitute end destination points of network. An ESN is a number which uniquely defines each cell phone in use. Under present specifications, it is formatted on 32 bits, so allowing combinations of hundreds of millions of different numbers. The ESN consists of the manufacturer's code and a reserved area. Paired with the mobile identification number (MIN) of the cell phone, the ESN and MIN are automatically transmitted to the mobile base station every time a cellular call is placed. The mobile switching office checks the ESN/MIN pair combination to ensure that both numbers are valid.

The ESN/MIN pair combination is sent systematically to a control tower when a call is initiated. To this end, every analog cell phone has two channels: a voice channel, through which incoming and outgoing speech or data signals (generically referred to as user information) are exchanged between the calling parties, and a control channel through which the ESN and MIN, ter alia, are conveyed. The control channel is used for establishing the telephone call to inform the cell tower that it is acquiring a voice channel, to process the telephone call, and to identify a call with an associated MIN. This routine is performed through a predefined protocol between the cell phone terminal and the cell tower. After the control channel completes its setup, the voice channel sends and transmits the user information. The duration of a telephone call over the voice channel is arbitrary, varying from a few seconds to several hours, while the data exchanges over the control channel can only last for a few seconds. It can be noted that all the while a cell phone's power is on, the control channel is periodically connected (at a few seconds interval) with the cell tower using its ESN and MIN numbers, irrespective of whether or not a telephone link is established on the voice channel. The cell phone terminal 2 is configured to send location information obtained through its GPS terminal in the form of data structured as an electronic serial number (ESN), as shall be explained further in more detail.

The GPS terminal has a classical coordinate extractor 20 which analyzes the signals received from the satellites 6 tlirough the aerial 4 to determine the position coordinates of the cell phone terminal 2, e.g. in terms of longitude and latitude bearings. The thus-obtained location information is sent to a zone calculator, whose function is to determine from the coordinates an elementary zone of a corresponding ESN (hereafter referred to as a "location ESN" to distinguish from the cell phone's classical and unique ESN that serves as a serial number identification). To this end, the zone locator 22 operates in conjunction with an ESN formatter 24 which can contain a set of location ESNs arranged in a look-up table indexed to the above elementary zones, as explained in more detail with reference to Fig. 3. The elementary zone in question covers an area which is sufficiently restricted to allow the cell phone terminal 2 to be pin-pointed to within a radius of 50 meters using a root-mean-square technique according to the FFC stipulations. In this context, it is recalled that the ESNs currently in use have a 32-bit format, so allowing several hundred million different possible values. The total number of different location ESNs required to cover an operational territory within the US, or even the entire US territory, with the required precision thus occupies a very small percentage of the available ESNs.

When the zone locator 22 receives a set of coordinate values from the GPS terminal, it can identify the corresponding elementary zone within which the cell phone terminal is located. This information is then outputted upon request.

The location ESNs in the look-up table may be .stored in abbreviated form to save on memory space. In this case, they are processed by the ESN formatter 24 to set them into a format corresponding to a classical ESN, notably as regards the number of bits and other information-carrying data configurations.

The thus-formatted location ESN is then supplied to the standard microprocessor-based communications circuitry 26 of the cell phone terminal 2 as and when required. To this end, the circuitry 26 is equipped with a an ESN interface 28 which handles the insertion of location ESNs into the transmitted data stream. The location ESN is supplied to the ESN interface 28 by an ESN inserter 30 connected to the output of the ESN formatter 24.

In the example, the GPS terminal portion, i.e. the coordinate extractor 20, has a sufficiently fast response time - time taken to extract position coordinates after being activated - to allow it be kept in the off state by default, thus saving on power consumption. However, the GPS device can alternatively be kept active all the while the cell phone is in the standby mode. The signals from the satellites 6 are then processed through the aerial 4 and coordinate extractor 20 periodically and automatically, for instance every few seconds, to ensure that the extracted coordinates reflect the actual position of the terminal with sufficient accuracy. The ESN look-up table 22 and ESN formatter 24 may then be activated at each coordinate update so that an exploitable location ESN is immediately available upon request from the ESN interface 28. However, these circuit elements 22 and 24 can be made to respond sufficiently fast to allow them to be activated in view of delivering a location ESN only upon request, so saving on power consumption. In this case, the coordinate extractor 20 contains an updatable memory which stores the latest coordinate bearings acquired.

When a call is made from a cell phone terminal 2, the latter uses its built in GPS device to locate its position. It also has dual or more than one MIN/ESN associated with it. The microprocessor based circuitry within the terminal checks if the call is emergency or non- emergency. If emergency, the phone sends an "emergency" ESN or MIN to the MSTO office before dialing the DID emergency number that has the position information embedded in it. The MSTO 12 queries its data base to check the status of that ESN ; accordingly, the MSTO determines that it is dedicated to an emergency only and sends the dialed DID to the LEC 14. That in turn sends it immediately to the local emergency service. The local emergency service decodes the emergency DID call and displays it on a PC map, showing exact street location. The emergency dispatch office can locate the emergency call and send the proper authority.

If the call is not an emergency call, the cell phone sends another ESN or MIN to the MTSO office before dialing the DID that represents the position of the caller. The MTSO checks if that ESN/MIN is emergency ESN. Since the ESN/MIN is not in this case emergency, the DID representing the position will be sent to the LEC 14, and then to the location service bureau for direction or other service.

There shall now be explained in more detail by way of an example how a location ESN is inserted into the communications data sent by the cell phone terminal 2 when location information needs to be transmitted, and how the data contained in this location ESN is acted upon and processed at the MTSO 12, LEC 14 and, from there, at the PSAP 16 or location services 18. Referring to the Fig. 2, the procedure starts with an initial step SI in which the cell phone terminal 2 is switched on. In this state, the terminal periodically goes through a routine of acquiring a control channel (step S2) and sending on that channel its ESN and MIN as an ESN/MIN pair combination to the MTSO 12 via its nearby cell tower 8 in accordance with a standardized communications protocol. In this way, the cell phone terminal 2 is constantly ready to send and terminate a phone call. The ESN in question here is the cell phone terminal's unique identifier, expressed in the form of an electronic data word of 32 bits. The ESN is attributed to the terminal at its initial entering into service under the terms and conditions set out by its operator company and does not normally change. The operator receiving the transmitted ESN is thus able to identify the physical device (or more specifically the smart card inside) at the origin of this transmission. The MIN is generally the cell phone terminal's call number and is different from its ESN. Steps S2 and S3 are repeated periodically starting from the moment the terminal 2 is switched on (loop LI and wait step S4).

In parallel, the cell phone terminal 2 is active to detect an event that requires a location ESN to be sent (step S5). This event may be a request to make to make an outgoing call or the depression of a special key or key code. All the while there is no event or request to make an outgoing call, the process cycles through loop LI, so repeating steps S2 and S3 at regular intervals determined by the duration of the wait step S4.

As soon as an event is detected at step S5, it is determined whether or not it stems from an emergency situation (step S6).

It shall be assumed that the call is made in response to an emergency situation, in which case the procedure follows along branch line L2 after step S6. Various possibilities can be envisaged for establishing this situation : the user may dial a call number such as "911" which is automatically recognized within the internal circuit functions 26 of the cell phone terminal 2 as arising from an emergency situation, a special "panic" or "emergency" button is depressed, so creating the event detected at step S5, or a specific code is entered on the keypad.

Thereafter, the cell phone terminal 2 acquires the position (or reads out the latest position previously acquired) from its GPS positioning device 4, 20 (step S7). This position, expressed in coordinate bearings, is transformed into an ESN format (designated location ESNl) using the ESN look-up table 22, as explained above (step S8). In addition to location information, ESNl also contains an indication that it is elaborated in the context of an emergency situation. This indication can be expressed, e.g. by special bit values, or by the fact that it belongs to a set of location ESNs pre-assigned to emergency location services. The location ESNl is temporarily stored. All the information is thus ready to be sent to the cell tower 8.

The cell phone terminal 2 then sends its identification ESN together with its MIN to the cell tower 8 through the control channel acquired at step S2 (step S9). In response, it receives from the MTSO 12 an acknowledgment indicating that the communication can proceed through an allocated communications channel.

In response, the cell phone terminal 2 processes the location ESNl through its ESN interface 28 and ESN inserter 30, and sends it to the cell tower 8 for relaying to the MTSO 12 (step SI 1) through the control channel. Upon receipt of this data, the MTSO identifies the ESNl as being a location ESN as opposed to an identification ESN, and processes it accordingly. This identification can be achieved e.g. by immediately comparing the number contained in ESNl with numbers known to correspond to location ESNs for the area under control, or by identifying a special code within ESNl indicating that it is a location ESN in accordance with a pre- established protocol. The location information contained in ESNl is then passed on to the PSAP 16 competent for handling the emergency.

In the present example, this requires first of all transforming the location ESNl into a telephone number (i.e. DID) format at the level of the MTSO 12, if it is not already in such a DID format. The reason for this transformation is that there may not be a network between the MTSO 12 and PSAP 16 capable of handling and forwarding an ESN format. Such a network would require an appropriate protocol for switching, such as the "signaling system 7" (SS7) network.

Classically, a DID number is an item of information sent by a telephone terminal which gives its own telephone number to the receiving party. A set of DID numbers is obtained from the network operator on a rental basis for a fixed fee. DIDs are assigned by the North American Dialing Plan Commission to any telephone company that needs certain criteria and regulatory issues.

Various possibilities exist for producing a DID corresponding to the received ESNl (hereafter referred to as a location DID). In the embodiment considered, it shall be assumed that there is a one-to-one correspondence between a location ESNl and its corresponding location DID. The MTSO 12 thus includes a data base which contains all the location ESNs it may be expected to handle and a cross reference to the corresponding location DIDs, in the manner of a look-up table. This table also takes account whether or not the location ESN being processed originates from an emergency situation, this being indicated by the coding contained in the location ESNl, as explained above. Thus, an emergency location ESN 1 will give rise to a location DID which also contains an indication of the emergency situation. Thus the process continues with the step S12 of determining whether the location ESNl has a DID format therein. This would be the case if a reformatting to produce a location DID has taken place upstream.

If the location ESNl has not been converted into a DID format, the process proceeds by turning the location ESNl into a DID (step SI 3). If the location ESNl already contains a location DID format (as determined at step SI 2), then that DID is extracted for further processing (step SI 4).

The MTSO 12 then compares the thus-obtained location DID with emergency DIDs stored in its data base to determine whether it corresponds to an emergency (step SI 5). Note that this step can also be performed directly by reading the emergency-indicating code contained in the DID corresponding to location ESNl, or by comparing the location DID/ESNl received with a table of emergency location DID/ESNs.

The location ESNl in question originating from an emergency, the MTSO sends the corresponding location DID to the competent PSAP through the LEC 14 (line L3 and step SI 6).

Advantageously, the MTSO does not just simply convert location ESNs into location DIDs, with or without an emergency indication, but also reads the location information contained therein to determine the geographical location of the sending cell phone terminal 2. In this way, the MTSO

12 can use this information to direct the location DID to the PSAP nearest the cell phone terminal, for instance the local police station, fire department or rescue patrol center.

In the preferred embodiment, the cell phone terminal's mobile identification number (MIN) is sent to the PSAP along with the location DID (or location ESN if the network so allows it).

The receiving PSAP 16 receives the location DID (step SI 7) and performs a reverse operation through its data base look up table to covert it back into the corresponding area from which the cell phone terminal 2 issued the call. The above steps S5 through to S17 take place during the initial set up of the telephone call through the control channel. Thereafter, the system 1 performs the standard procedure for establishing a two-way telephone communication between the cell phone terminal 2 and the PSAP on the voice channel.

At the level of the PSAP 16, the thus-obtained position data is processed in a facility where it is combined with data representing the area of the call location to produce an automatic location identification (ALI) function. The facility thus electronically creates a map of the call area, showing e.g. a large-scale street plan with the main landmarks (significant buildings, water hydrants, etc.). The location of the caller can thus be displayed on computer screen with the mapping information. It can be noted that most "911 " dispatch offices or police facilities are linked to an ALI system. The information from the ALI system is sent to the PSAP at the latter's request. In this way, the PSAP can locate the emergency call and activate the competent authority to assist the caller.

The above location service is not limited to emergency situations. Indeed, it may be useful for a calling party using the cell phone terminal 2 to disclose its position automatically for other services, e.g. when communicating with a location service bureau for directions on how to reach a certain point, etc.

To cater for such services, the cell phone terminal 2 is also equipped to create non- emergency location ESNs. Depending on the protocol used, these may be identical to the emergency location ESN for any given corresponding area, except for the contents of the above- mentioned special code bits. Alternatively, they may be independent of each other, in which case the ESN look-up table 22 is doubled, one table being assigned to emergency location ESNs, the other to non-emergency location ESNs. The precision of the locations ESNs may then be different. For instance, the non-emergency location ESNs may be made to correspond to larger unit areas to economize on resources.

The procedure for enabling a cell phone terminal 2 to identify its location to a non- emergency service (here the location services 18) shall now be described referring again to the flow chart of Fig. 2. In this description, the steps which are analogous to those performed in the case of an emergency situation are identified by the same reference numerals, but followed by a "prime" symbol.

The steps SI to S5 from power on to detecting an outgoing call are identical to the previous case. At step S6, it is determined that the outgoing call is not made in connection with an emergency, whereupon the process continues along line L4. Subsequently, it is determined whether it is necessary to send the location information acquired by the GPS device to the receiving party (step SI 8). This branching accommodates for normal calls where the location information would not be sent. In such a case, the process continues as a normal outgoing call with the setting up of a communications channel (line L5 and step SI 9).

If it is required to send the location information, then the process continues along line L6. This branching can be determined in various ways: the caller may initially enter a code or depress a key signifying that the location information is to be sent in the context of a non- emergency situation, or the terminal may have a look-up table which automatically determines that the location information must be sent in association with certain dialed telephone numbers, e.g. corresponding to a location service 18. After line L6, the process goes through a routine of acquiring the cell phone terminal's position from its GPS device (step S7'), turning that position information into a non-emergency location ESN, designated ESN2, (step S8'), sending its identification ESN/MIN pair (step S9'), receiving an acknowledgement via the cell tower 8 (step S10'), and sending the non-emergency location ESN2 to the cell tower (step SI T) through the control channel. The above steps S7' to S 11 ' are substantially identical to steps S7 to S 11 , except that location ESN2 is processed instead of location ESNl.

At the MTSO 12, the ESN2 is turned into a corresponding non-emergency DID format (step S13') or, if the location information is already in a DID format, that DID is extracted (step S14'). As in the case of step S13 above, this conversion can be established through look-up tables in a data base controlled by the MTSO, each non-emergency location ESN having a one- to-one correspondence with a non-emergency location DID. The thus-obtained location DID is then analyzed to determine whether or not it originates from an emergency situation (step SI 5). This analysis is performed in a manner analogous to that described in connection with the same step for the case of an emergency situation, i.e. by comparing the number contained in the DID with numbers corresponding to emergency or non-emergency DIDs, or by detecting an emergency -indicating code in the bits that make up the location DID. The analysis can also be made also prior to the conversion into a DID format, e.g. on the basis of corresponding emergency-indicating code bits at the level of ESN2.

Because the DID shall be sent to a destination different from a PSAP, it is possible to use the same location DIDs for emergency and non-emergency services without risk of confusion. In other words, after conversion from an location ESN, the resulting location DID corresponding to a given area is the same whether it arises from an emergency or non-emergency situation; only its destination point differs.

Having determined that ESN2 corresponds to a non-emergency situation, the corresponding location DID is sent via the LEC 14 to an appropriate service, in this case to a direction and road service (step S20). The caller's MIN number can also be sent to the direction and road service together with the location information, in this case the location DID.

There, the location DID is transformed into a form yielding a physical location in terms of coordinate bearings, if needs be with the cooperation of an ALI service to provide a mapped context to location coordinates, as explained above. The outgoing telephone call is also routed to the direction and road service to establish on the voice channel a two-way speech link with a service operator.

In instances where the communications link from the cell phone terminal 2 right through to the PSAP, location services 18 or other end point can support the transmission of the location information contained in an ESN format, the steps S14 and SI 4' of converting the location ESN (ESNl or ESN2) can be omitted. In this case, the emergency nature of the call (step SI 5) is established by examining the data contained in the location ESN. Thereafter, the location ESN is sent through the telephone network to the PSAP 16 or location services 18, where it is decoded into position coordinate values using techniques analogous to those employed in the case of a location DID. In the example of Fig. 2, the location ESNs are analyzed at the level of the MTSO 14, where they are also converted into location DIDs. However, this analysis and/or conversion can be effected at another facility linked to the MTSO, such as a central office (CO) able to identify the nature of the call, or a controller able to perform automatic number identification (ANI) and/or evaluate the cell phone terminal identification (MIN) number. In this alternative, the controller would then e.g. pass the call to the PSAP 16. As the location ESN (or corresponding location DID obtained therefrom) represents the location of the caller, the MTSO, CO and ANI/MIN controller are able to pass the call to the appropriate PSAP (e.g. a "911" station) that is nearest the emergency location and best able to handle the emergency.

In all the embodiments described, it preferable to make part of the location ESN (ESNl or ESN2) have a telephone number format. Depending on protocols, this can correspond to the numbering plan area (NPA) or exchange numbering switching system (NXXX) formats. It can also be noted that the PSAP 16 or location services 18 need not necessarily be fixed at a given location ; they can e.g. be in the form of mobile assistance units which regularly report their position so that they can be called whenever they are sufficiently close to assist the caller. There shall now be described with reference to Fig. 3 an example of how a set of location DIDs or ESNs - whether they be for emergency or non-emergency calls - can be allocated to a given geographical sector in conformity with the present invention.

Fig. 3 a is a map of a territory 40 to be covered by the location system. For the purpose of the example, the territory is greatly simplified and mapped as a rectangle. In a real-life situation, the territory can be a county, a state, or a country such as the US, etc. The map 40 is divided into a mosaic of non-overlapping areas 42. These areas are rectangular or square blocks 42 forming a regular grid of m rows and n columns on the map 40. Each block 42 is to contain at least one cell tower 8. This can be ensured by conferring appropriate dimensions to a block. For instance, assuming that the entire territory is covered by the cell phone network and that each cell tower 8 covers a range not exceeding 10 miles, then the requirement of at least one cell tower per block can be met by making the blocks have 10 mile sides.

The cell phone terminal 2 designed to operate in the above territory is programmed to store the above map 40 and its constituent grid of blocks 42 e.g. explicitly in the form of memory map, or else to construct it algorithmically from basic information to save on memory space. In this last case, the zone calculator 22 (cf Fig. 1) can be provided with the following information: the bearing of the origin Om of the map, here identified as corresponding to the south-west corner of the map, expressed in terms of a longitude L0 and latitude M0, the number m of rows of blocks 42, the number n of columns of blocks, the elementary dimensions of each block.

This information allows the zone calculator 22 to determine in which block 42 of the map 40 is located the cell phone 2 from a bearing delivered by the GPS device 4,20. For instance, the zone calculator 22 uses the coordinate bearing delivered by the GPS device first to determine its distance from the origin 0m in the north direction, and from that the block row number r corresponding to that distance, and similarly its distance from the origin Om in the east direction, and from that the block column number s corresponding to that distance. This gives a unique bloc 42 at the row and column address P(r,s). Now each cell tower 8 is pre-assigned a specific identifier which it transmits to the

MTSO together with the location ESN. This identifier is exploited to allow the same set of ESNs to be used for each block 42. Specifically, a location ESN will specify where the cell phone terminal 2 is within a block 42, and the cell tower identifier specifies the block in question. In the embodiment, this scheme is implemented by having the cell towers 8 informed of the map system used and of the block 42 to which it belongs using a recognized identification scheme. In this way, the cell phone terminal does not in fact need to specify the block in which it is located. Naturally, the correspondence between the identifier and the blocks 42 according to the map 40 is also known along the chain leading to the PSAP 16 and location services 18 to extract the required location information at that level specifying the block 42 within the map 40.

The combination of the location ESN and cell tower ID is then sent to and processed by the MTSO 12 to yield either a specific location ESN or a location DID that can be processed by the PSAP 16 or location services 18. This allows the same set of location ESNs to be used for different cell towers 8.

Having determined the block 42 in which it is located (hereafter referred to as coarse location) for its own internal calculations, the zone calculator 22 performs an algorithm to determine its position within that block (hereafter referred to as fine location). To this end, each block 42 is itself subdivided into elementary boxes 44, referred to as elementary zones (or simply zones). It is with these elementary zones 44 that a one-to-one correspondence is established with the ESNs. In other words, each elementary zone 44 of a given block 42 has a unique location ESN. The size of an elementary zone shall depend on the location accuracy required. In the example, a positioning accuracy of 50 meters or better is required. This can be ensured with square elementary zones 44 each of 50 meter sides, with the center point of the zone serving as its absolute positional reference. Thus, each block 42 is formed of an array of 320 x 320 elementary zones (approximating 1 mile to 1600 meters).

To determine in which elementary zone 44 the cell phone terminal 2 is located, the zone calculator 22 performs a calculation similar to the one described for determining its block 42. In the example, it makes reference to an origin point Ob(0,0) of the block 42 in which it is located, corresponding to its south-west corner (Fig. 3b). This origin point is fixed by the structure of the grid system, so its absolute position is known implicitly. Each zone 44 is assigned a unique reference number Z(i) within the block 42, for instance starting from Z(0) at the origin and incrementing along the rows, the zone at the north-west corner being assigned the number Z(102399) (=320x320-1).

The position P coordinates acquired from the GPS device are used to calculate the distance separating the cell phone terminal from this origin Ob(0,0) of the block 42, along the north and east directions (respectively XP and YP, Fig. 3b). This information gives the zone 44 that contains the position P of the cell phone terminal, the zone calculator 22 also being fed with the size of the zones (50 meter sides) and their row and line numbering system. In the example, the point P is thus determined to be located in the zone having the reference Z(k). The reference Z(k) is fed to a look-up table, in the zone calculator or in the ESN formatter

24, from which the corresponding location ESN is obtained.

The thus-obtained location ESN is then transmitted in accordance with the protocol already described with reference to Fig. 2.

It will be noted that the cell phone terminal 2 needs only to store the correspondence between a reference number Z(i) of an elementary zone and an ESN, for i=0 tol02399. It can be envisaged to generate an ESN format number directly from that zone reference number, thus obviating the need to store all 102400 correspondences.Naturally, there are many other ways of forming a grid system and determining the elementary zone with the required accuracy using GPS values and prestored map data. For instance, the elementary zone of point P can be . calculated directly from the coordinate distances separating that point and the origin, using modulo arithmetic algorithms.

Also, it can be appreciated that the size and shape of the territory and of its blocks can be adapted to any real life situation as a function of the geography and density of cell towers.

It can be noted that the ESN format of 32 bits can allow a much larger number of ESNs to be reserved for use as location ESNs. This makes it possible to consider other area allocation schemes in which each location ESN is assigned to a substantially smaller area, so improving location accuracy and/or allowing less complex root-mean-square techniques to be used.

In some cases, it may be possible to obviate the need for a coarse location in terms of blocks 42 and simply divide a territory into unique elementary zones. Finally, while the embodiments have been described in the context of a location service, the invention allows ESN formats to be used for sending other types of messages. For instance, the system can be configured so that ESNs are allocated for sending short bursts of data messages (other than the usual cell phone identification number) to communicate various items of information such as: - sending metering information (gas meter, electricity meter, water meter), vending machine, telephone communication charges,

- personal messages pre-assigned to respective ESNs, - diagnostic test messages, indicating to the operator through a pre-assigned ESN that the terminal has diagnosed a fault within its own electronics or in the network,

- configuration messages, for instance to request a change in the subscription conditions, communications set-up, etc.,

- authorization codes, e.g. to allow access to various services in accordance with a predetermined protocol in which specific ESNs are used as entry codes,

- etc.

It shall be understood that many variants and other embodiments and variants can be envisaged while remaining within the scope and spirit of the claimed invention.

Claims

1. A system for communicating at least one data message from a cellular telephone terminal tlirough a communications network, comprising at least one cellular telephone terminal having an identification electronic serial number (ESN), said cellular telephone terminal comprising means for sending said data message in the form of an electronic serial number having a format substantially the same as that of its identification electronic serial number, said system having a set of electronic serial numbers allocated for use as data messages in the form of electronic serial numbers for communicating information other than the identification number of said cellular telephone terminal.

2. The system of claim 1, wherein said data message sent by said cellular telephone terminal is variable as a function of a user choice or operating condition of said terminal.

3. The system of claim 1, wherein said data message contains location information expressing a geographical position of said cellular telephone terminal.

4. The system of claim 1, wherein said identification electronic serial number and said data message both have a same number of bits.

5. The system of claim 1 , wherein said data message is sent in short bursts over a control channel during a call set-up phase.

6. The system of claim 1 , wherein said cellular telephone terminal is operative to send its identification electronic serial number, then its mobile identification number (MIN), then at least one said data message, and then a destination number.

7. The system of claim 1 , characterized in that a mobile identification number (MIN) of the cellular telephone terminal is sent to a destination point along with said data message.

8. The system of claim 1 , comprising format conversion means in said communications network for converting said data message from its format as an electronic serial number sent by said cellular telephone terminal into another format prior to forwarding location information contained therein.

9. The system of claim 8, wherein said another format is a direct inward dialing (DID) service format.

10. The system of claim 8, wherein said format conversion means are located at a mobile telephone switching office (MTSO) operative for said cellular telephone terminal.

11. The system of claim 8, wherein said format conversion means are located a local exchange carrier (LEC).

12. The system of claim 1, wherein said electronic serial number corresponding to said data message sent by said cellular telephone terminal comprises at least a part having a telephone number format.

13. The system of claim 1 , wherein at least a part of said electronic serial number corresponding to said data message sent by said cellular telephone terminal is converted into a telephone number format by one of: a mobile telephone switching office (MSTO) and a local exchange carrier (LEC).

14. The system of claim 1, wherein said data message is sent all along from said cellular telephone terminal through to an end point destination in the form of an electronic serial number.

15. A system for communicating a geographical location of a cellular telephone terminal through a communications network, comprising at least one cellular telephone terminal having an identification electronic serial number (ESN), said terminal being operative to acquire and send location data representative of its location to a receiving point of said communications network, wherein said cellular telephone terminal comprises means for sending said location data in the form of an electronic serial number having a format substantially the same as that of its identification electronic serial number, said system having a set of electronic serial numbers ^' allocated for location information.

16. The system of claim 15, wherein said identification electronic serial number and said location information in the form of an electronic serial number both have a same number of bits.

17. The system of claim 15, wherein said location information in the form of an electronic serial number is sent over a control channel during a call set-up phase.

18. The system of claim 15, wherein said cellular telephone terminal is operative to send its identification electronic serial number, then its mobile identification number (MIN), then the location information in the form of an electronic serial number, and then a destination number.

19. The system of claim 15, characterized in that a mobile identification number (MIN) of the cellular telephone terminal is sent to a destination point along with said data message.

20. The system of claim 15, comprising format conversion means in said communications network for converting said location information from its form as an electronic serial number sent by said cellular telephone terminal into another format prior to forwarding location information contained therein.

21. The system of claim 20, wherein said another format is a direct inward dialing

(DID) service format.

22. The system of claim 20, wherein said format conversion means are located at a mobile telephone switching office (MTSO) operative for said cellular telephone terminal.

23. The system of claim 20, wherein said format conversion means are located a local exchange carrier (LEC).

24. The system of claim 15, wherein said electronic serial number format used for location information sent by said cellular telephone terminal comprises at least a part having a telephone number format.

25. The system of claim 15, wherein, wherein at least a part of said serial number format used for location information sent by said cellular telephone terminal is converted into a telephone number format by one of: a mobile telephone switching office (MSTO) and a local exchange carrier (LEC).

26. The system of claim 15, wherein said location information is sent in the form of an electronic serial number all along from said cellular telephone terminal through to an end point destination.

27. The system of claim 15, wherein a said cellular telephone terminal is operative to send said location information in short bursts.

28. The system of claim 15, wherein said electronic serial number format used for sending location information contains an indication as to whether said location information is intended for an emergency service or a non-emergency service.

29. The system of claim 28, wherein said indication is in the form of a code contained in said electronic serial number used for location information.

30. The system of claim 28, said indication is provided by pre-assigning separate sets of electronic serial numbers containing location information respectively for use in emergency situations and in non-emergency situations.

31. The system of claim 15, further comprising analyzing means within said network for analyzing an electronic serial number containing location information sent by said cellular telephone terminal and for forwarding location information contained therein to a specific service on the basis of said analysis.

32. The system of claim 31, wherein analyzing means determines whether said electronic serial number containing location information corresponds to an emergency or a non- emergency situation.

33. The system of claim 15, wherein each electronic serial number containing location information corresponds to a specific one of a set of elementary zones.

34. The system of claim 33, wherein a territory is divided into a plurality of blocks, each containing at least one cell tower and wherein said elementary zones are defined within a said block.

35. The system of claim 34, wherein at least some of a set of electronic serial numbers containing location information are repeated for different blocks, a specific location being further specified by data indicative of its block.

36. The system of claim 35 wherein said cellular telephone terminal has means for storing information relative to a map of said territory, blocks and elementary zones and means to determine from an absolute position a corresponding elementary zone identified according to a predetermined topology.

37. The system of claim 33, wherein each said elementary zone has an area such as to allow a location of a cellular telephone terminal to an accuracy of 50 meters or better.

38. A communications system operative with cellular telephones, said system disposing of electronic serial numbers allowing to identify individual cellular telephone terminals, wherein a set of said electronic serial numbers is allocated for the communication of data messages other than cellular telephone terminal identification data.

39. The system of claim 36, wherein a said cellular telephone terminal is operative to send said data messages in short bursts.

40. The system of claim 36, wherein said data messages contain location information of a sending cellular telephone terminal.

41. A cellular telephone terminal for a communications system disposing of electronic serial numbers allowing to identify individual cellular telephone terminals, wherein a set of said electronic serial numbers is allocated for the communication data messages other than cellular telephone terminal identification data, said cellular telephone terminal comprising means for selectively sending at least some of said set of allocated electronic serial numbers to convey a message.

42. The cellular telephone terminal of claim 41 , wherein said cellular telephone terminal is operative to send said data messages in short bursts.

43. The cellular telephone terminal of claim 41 , wherein said data messages contain location information of a sending cellular telephone terminal.

44. A cellular telephone terminal comprising means for sending location data representative of its physical position in the form of a location electronic serial number having a format substantially the same as that of an identification electronic serial number by which said cellular telephone is identified.

45. The cellular telephone terminal of claim 44, wherein said location information in the form of an electronic serial number and said identification electronic serial number both have a same number of bits.

46. The cellular telephone terminal of claim 44, wherein said location information is in the form of an electronic serial number is sent over a control channel during a call set-up phase.

47. The cellular telephone terminal of claim 44, wherein said location information is sent in short bursts.

48. The cellular telephone terminal of claim 44, operative to send its identification electronic serial number, then its mobile identification number (MIN), then its location information in the form of an electronic serial number, and then a destination number.

49. The cellular telephone terminal of claim 44, wherein said electronic serial number corresponding to location information comprises at least a part having a telephone number format.

50. The cellular telephone terminal according to claim 44, wherein said physical position is determined by a GPS positioning device, said terminal having means for converting coordinate data supplied by said device into a format of electronic serial number corresponding to that position.

51. The cellular telephone terminal of claim 44, comprising memory and determination means containing a set of electronic serial numbers allocated to location information and means for assigning a specific one of said allocated electronic serial numbers in response to information indicative of the physical position of said terminal.

52. The cellular telephone terminal of claim 53, comprising indicating means for indicating through said electronic serial number containing location information whether location information contained therein is intended for an emergency service or a non-emergency service.

53. The cellular telephone terminal of claim 52, wherein said indicating means produces a code contained in said allocated electronic serial number.

54. The cellular telephone terminal of claim 52, wherein said indicating means uses pre-assigned separate sets of allocated electronic serial numbers respectively for use in emergency situations and in non-emergency situations.

55. The cellular telephone terminal of claim 44, wherein each electronic serial number allocated to location information corresponds to a specific one of a set of contiguous geographical sectors.

56. The cellular telephone terminal of claim 55, wherein each said geographical sector has an area such as to allow a location of a cellular telephone terminal to an accuracy of 50 meters or better.

57. A method of communicating at least one data message from a cellular telephone terminal through a communications network comprising at least one cellular telephone terminal having an identification electronic serial number (ESN), wherein said data message is sent from said cellular telephone terminal in the form of an electronic serial number having a format substantially the same as that of its identification electronic serial number, said system having a set of electronic serial numbers assigned for use as data messages in the form of electronic serial numbers for communicating information other than the identification number of said cellular telephone terminal.

58. The method of claim 57, wherein said data message sent by said cellular telephone terminal is variable as a function of a user choice or operating condition of said terminal.

59. The method of claim 57, wherein said data message contains location information expressing a geographical position of said cellular telephone terminal.

60. The method of claim 57, wherein said identification electronic serial number and said data message both have a same number of bits.

61. The method of claim 57, wherein said data message is sent in short bursts over a control channel during a call set-up phase.

62. The method of claim 57, wherein said cellular telephone terminal sends its identification electronic serial number, then its mobile identification number (MIN), then at least one said data message, and then a destination number.

63. The method of claim 57, characterized in that a mobile identification number (MIN) of the cellular telephone terminal is sent to a destination point along with said data message.

64. The method of claim 57, wherein said communications network converts said data message from its format as an electronic serial number sent by said cellular telephone terminal into another format prior to forwarding location information contained therein.

65. The method of claim 64, wherein said another format is a direct inward dialing (DID) service format.

66. The method of claim 64, wherein said format conversion takes place at a mobile telephone switching office (MTSO) operative for said cellular telephone terminal.

67. The method of claim 64, wherein said format conversion takes place at a local exchange carrier (LEC).

68. The method of claim 57, wherein said electronic serial number format corresponding to said data message sent by said cellular telephone terminal comprises at least a part having a telephone number format.

69. The method of claim 57, wherein at least a part of said electronic serial number format corresponding to said data message sent by said cellular telephone terminal is converted into a telephone number format by one of: a mobile telephone switching office (MSTO) and a local exchange carrier (LEC).

70. The method of claim 57, wherein said data message is sent all along from said cellular telephone terminal through to an end point destination in the form of an electronic serial number.

71. A method of communicating a geographical location of a cellular telephone terminal through a communications network comprising at least one cellular telephone terminal having an identification electronic serial number (ESN), comprising the step of :

-acquiring, at the level of said cellular telephone terminal, location data representative of the location of said terminal,

- setting said location data into a format of an electronic serial number substantially the same as the format of its identification electronic serial number, a set of electronic serial numbers being pre-assigned for location information, and

- sending said location information in said format of an electronic serial number.

72. The method of claim 71 , wherein said identification electronic serial number and said location information in the form of an electronic serial number both have a same number of bits.

73. The method of claim 71 , wherein said location information in the form of an electronic serial number is sent in short bursts over a control channel during a call set-up phase.

74. The method of claim 71 , wherein said cellular telephone terminal send its identification electronic serial number, then its mobile identification number (MIN), then the location information in the form of an elecfronic serial number, and then a destination number.

75. The method of claim 71 , wherein a mobile identification number (MIN) of the cellular telephone terminal is sent to a destination point along with said data message.

76. The method of claim 71 , wherein said communications network for converts said location information from its form as an electronic serial number sent by said cellular telephone terminal into another format prior to forwarding location information contained therein.

77. The method of claim 76, wherein said another format is a direct inward dialing (DID) service format.

78. The method of claim 76, wherein said format conversion takes place at a mobile telephone switching office (MTSO) operative for said cellular telephone terminal.

79. The method of claim 77, wherein said format conversion takes place at a local exchange carrier (LEC).

80. The method of claim 71, wherein said electronic serial number format used for location information sent by said cellular telephone terminal comprises at least a part having a telephone number format.

81. The method of claim 71 , wherein, wherein at least a part of said serial number format used for location information sent by said cellular telephone terminal is converted into a telephone number format by one of: a mobile telephone switching office (MSTO) and a local exchange carrier (LEC).

82. The method of claim 71, wherein said location information is sent in the form of an electronic serial number all along from said cellular telephone terminal through to an end point destination.

83. The method of claim 71, wherein said electronic serial number format used for sending location information contains an indication as to whether said location information is intended for an emergency service or a non-emergency service.

84. The method of claim 83, wherein said indication is in the form of a code contained in said electronic serial number used for location information.

85. The method of claim 83, said indication is provided by pre-assigning separate sets of electronic serial numbers containing location information respectively for use in emergency situations and in non-emergency situations.

86. The method of claim 71 , further comprising the step of analyzing within said an electronic serial number containing location information sent by said cellular telephone terminal and for forwarding location information contained therein to a specific service on the basis of said analysis.

87. The method of claim 86, wherein analyzing step determines whether said electronic serial number containing location information corresponds to an emergency or a non- emergency situation.

88. The method of claim 71 , wherein each electronic serial number containing location information corresponds to a specific one of a set of contiguous geographical zones.

89. The method of claim 88, wherein each electronic serial number containing location information corresponds to a specific one of a set of elementary zones.

90. The method of claim 89, wherein a territory is divided into a plurality of blocks, each containing at least one cell tower and wherein said elementary zones are defined within a said block.

91. The method of claim 90, wherein at least some of a set of electronic serial numbers containing location information are repeated for different blocks, a specific location being further specified by data indicative of its block.

92. The method of claim 90 wherein said cellular telephone terminal has means for storing information relative to a map of said territory, blocks and elementary zones and means to determine from an absolute position a corresponding elementary zone identified according to a predetermined topology.

93. The method of claim 88, wherein each said geographical sector has an area such as to allow a location of a cellular telephone terminal to an accuracy of 50 meters or better.

94. A method of communicating data messages in a communications system operative with cellular telephones, said system disposing of elecfronic serial numbers allowing to identify individual cellular telephone terminals, comprising the step of allocating a set of said electronic serial numbers for the communication of data messages other than cellular telephone terminal identification data.

95. The method of claim 94, wherein said data messages are sent in short bursts from a cellular telephone terminal.

96. The method of claim 94, wherein said data messages contain location information of a sending cellular telephone terminal.