Abstract:
At least one of voice and data information is transmitted in connection mode via a radio interface in first radio zones. In second radio zones, voice or data information is transmitted exclusively in packet mode via a radio interface. When an emergency call is issued by a subscriber station from one of the first radio zones, a voice and/or data connection is established between the subscriber station and an emergency control center. When an emergency call is issued by a subscriber station from one of the second radio zones, at least one piece of emergency information which identifies the second radio zone is transmitted to an emergency control center.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is based on and hereby claims priority to German Application No. 100 37 740.8 filed on Aug. 2, 2000, the contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   Until now, it has been possible to send emergency call messages only from radio cells in which connection-oriented services are available. A document (Tdoc SMG2 EDGE 298/99) which was submitted at the ETSI SMG2 EDGE Workshop from Aug. 24 to 27, 1999 in Paris relates to the sending of emergency call messages from areas of a radio communications system in which only packet-oriented services or only connection-oriented services are available in some radio cells while, in contrast, packet-oriented and connection-oriented services are available in other radio cells. This document proposes that, when an emergency call message is to be sent from a subscriber station in a radio cell with exclusively packet-oriented services, a handover process be initiated for this subscriber station, with the aim of associating the relevant subscriber station with a radio cell with connection-oriented services. 
   In order to speed up the handover process, Section 11.2.19, page 160 requires that the subscriber station be informed via a signaling channel that connection-oriented services are not available in the originally selected radio cell. A message such as this is advantageous whenever, for example, connection-oriented services are available in one of the adjacent radio cells and this radio cell is selected by the handover process. However, if connection-oriented services are not available in any of the feasible radio cells, a procedure such as this runs into considerable problems. 
   SUMMARY OF THE INVENTION 
   The present invention is based on the object of specifying a method for transmitting emergency call messages which originate from a subscriber station in a radio cell in which no connection-oriented service is available. 
   One major aspect of the method according to the invention is that, in the case of an emergency call originating from a subscriber station in a radio cell in which at least one of speech and data information are transmitted exclusively in a packet-oriented manner via a radio interface, an emergency call center is signaled that an attempt has been made to set up a connection to an emergency call center in a radio cell in which no connection-oriented services are available. The aim in the signaling of the emergency call is to detect information that is as valid as possible about, for example, the location or the identity of a user who is sending the emergency call, and to transmit this to the emergency call center. A minimum requirement in this sense is thus the transmission of information which identifies the radio cell of the user who is sending the emergency call. According to one preferred development of the method according to the invention, a unidirectional speech information interchange also takes place, from the relevant subscriber station to the emergency call center. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which: 
       FIG. 1  is a block diagram of a conventional radio communications system, in which only connection-oriented services are available, having an emergency call center, and 
       FIG. 2  is a block diagram of a radio communications system in which connection-oriented and packet-oriented services are available, having an emergency call center. 
       FIG. 3  is a flowchart of a method according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
   The structure of the radio communications system which is illustrated in  FIG. 1  corresponds to that of a known GSM mobile radio network which has a large number of mobile switching centers MSC for connection-oriented services, which are networked to one another and allow access to a landline network PSTN or to some other radio communications network PLMN. The mobile switching centers MSC may be connected to an emergency call center EC either directly or indirectly via the landline network PSTN. A connection is also possible between the mobile switching centers MSC and the emergency call center EC via some other radio communications network PLMN. 
   Furthermore, the mobile switching centers MSC are connected to at least one base station controller BSC. Each base station controller BSC allows a connection to be set up to at least one base transceiver station BTS. Base station controllers BSC and associated base transceiver stations BTS are combined to form a base station subsystem BSS. A base transceiver station BTS may set up a unidirectional or bidirectional speech and/or data connection to a subscriber station TS via a radio interface. A large number of radio channels Ch 1  to CHn are available at the radio interface for connection-oriented transmission of speech and/or data information within a radio cell C. 
   If an emergency caller HC sends an emergency call via a subscriber station TS, then the process of setting up the connection between the subscriber station TS of the emergency caller HC and the emergency call center EC is subject to numerous simplifications. These simplifications include, for example, higher-prioritized handling of the process of setting up the connection, dispensing with any check of information which is stored on a SIM card (Subscriber Identification Module) for granting of network or service access authorizations, or dispensing with terminal-identification-dependent blocking of access authorizations. 
   In the radio communications system illustrated in  FIG. 2 , packet-oriented services are also available, in addition to connection-oriented services. Packet-oriented services are used predominantly for the transmission of data information, while connection-oriented services are intended primarily for the transmission of speech information. 
   In GSM mobile radio systems by way of example, packet-oriented services are provided by GPRS (General Packet Radio Services). GPRS allows a theoretical data transmission rate of 182 kb/s. In practice, data transmission rates of 150 to 170 kb/s can be expected. In addition to the components which have already been illustrated in  FIG. 1 , the radio communications system which is illustrated in  FIG. 2  has a number of additional components especially for packet-oriented services. For example, for packet-oriented services, the base station controller BSC is coupled to a packet data network PDN via a router SGSN (Serving GPRS Support Node) and a gateway GGSN (Gateway GPRS Support Node). The router SGSN is also coupled to a mobile switching center MSC via a further gateway GMSC. 
   There are a number of options, as shown in  FIG. 2 , for coupling an emergency call center EC to the radio communications system. Firstly, in the radio communications system illustrated in  FIG. 1 , the mobile switching centers MSC may be connected to an emergency call center EC either directly or indirectly via the landline network PSTN. By analogy with  FIG. 1 , a connection is also possible between the mobile switching centers MSC and the emergency call center EC via some other radio communications network PLMN. In addition to this, it is possible to couple the emergency call center EC directly to the packet data network PDN. In this case, the emergency call center EC could also be equipped with packet-data-processing terminals, which allow data packets to be converted to analog speech information. 
   Depending on the requirements resulting from the network plan, scenarios are possible in which only connection-oriented or only packet-oriented services are available in some radio cells, and both types of service are available in other radio cells. It is thus possible for only packet-oriented services to be available in a chosen radio cell.  FIG. 2  considers a scenario in which speech and/or data information can be transmitted  10  ( FIG. 3 ) on a connection-oriented or packet-oriented basis via the radio interface in a first radio cell C 1 , while only packet-oriented services are available  20  in a second radio cell C 2 . 
   On the basis of the method according to the invention, when an emergency call occurs which is sent from a subscriber station TS 1  of a first emergency caller HC 1 , a speech and/or data connection is set up  12  to the emergency call center EC via one or more of the radio channels CDCH 1  to CDCHn, which are available in the first radio cell C 1 , for connection-oriented services. In the case of an emergency call which is sent from a subscriber station TS 2  of a second emergency caller HC 2  in the second radio cell C 2 , at least one emergency call information item which identifies the radio cell C 2  is transmitted  22  to the emergency call center EC. 
   The emergency call information is, for example, transmitted at least in sections in a packet-oriented manner via radio channels PDCH 1  to PDCHn, the base transceiver station BTS, the base station controller BSC, the router SGSN, the gateway GMSC and the mobile switching center MSC to the emergency call center EC. 
   Data which has until that point been transmitted in a packet-oriented manner is converted at the gateway GMSC to data based on a connection-oriented transmission protocol. As an alternative to the sketched procedure, it is possible to transmit the emergency call information via a further gateway GGSN and the packet data network PDN to the emergency call center EC. In this case, no transmission-protocol-dependent conversion is required for the data. 
   The emergency call information may also optionally identify the physical position of the subscriber station TS 2  of an emergency caller HC 2 . Corresponding position information may be generated either at the network end from the knowledge of the microcell, nanocell or picocell in a radio network in which the emergency caller HC 2  is currently located, or at the subscriber station end if, for example, a subscriber station TS 2  is equipped with a GPS transmitter and receiver, and this position information can be added  24  to the emergency call information. If the emergency call information is also used to transmit to the emergency call center EC details relating to the identification of a subscriber station TS 2 , by which the emergency caller HC 2  can also be indirectly identified, then these details can be used to access data recording devices which, for example, contain information relating to a debilitation pattern, profile or medication incompatibilities of a patient, to simplify the preparations for medical assistance measures, or, in particular, also to speed them up. 
   In addition to the transmission of emergency call information, it is also possible to receive analog speech information at the subscriber station TS 1 , TS 2  of an emergency caller HC 2 , for this information to be converted to digital packets, and to be transmitted to the emergency call center EC. The analog speech information may in this case be transmitted  26 , for example, via a VoIP connection (Voice over Internet Protocol) or by a tone file (wave file). A speech information interchange such as this may be carried out both unidirectionally from the subscriber station TS 2  of an emergency caller HC 1 , HC 2  to the emergency call center EC and bidirectionally between the emergency call center EC and the subscriber station TS 2 . In the latter case, analogue speech information which is received at the emergency call center EC can be converted to digital data packets and can be transmitted  28  in a packet-data-oriented manner to the subscriber station TS 1 , TS 2  for reproduction. 
   In order to signal to an emergency caller HC 2  who is sending an emergency call from the second radio cell C 2  by his subscriber station TS 2  that, for example, only unidirectional emergency call connections or emergency call connections with restricted speech quality are possible from the second radio cell C 2 , the emergency caller HC 2  is informed from the network end about a corresponding signaling channel in the sense of user guidance that only packet-oriented services are available in the chosen radio cell. Furthermore, emergency call data packets which have emergency call information that identifies the second radio cell HC 2  and/or which contain speech information received at the subscriber station end are assigned an increased transmission priority. 
   The functionality and the structure of the radio communications system illustrated in  FIG. 2  can in principle also be transferred to other radio communications systems in which the invention may be used, in particular for subscriber access networks with wire-free subscriber access. The use of the method according to the invention is thus not restricted to the exemplary embodiments described here. 
   The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.