Different communication networks are known. Communication networks typically operate in accordance with a given standard or specification which sets out what the various elements of the network are permitted to do and how that should be achieved. For example, the standard or specification may define whether the user, or more precisely, user equipment or terminal is provided with circuit switched or packet switched service. The standard or specification may also define the communication protocols and/or parameters which shall be used for the connection. In other words, the standards and/or specifications define the “rules” on which the communication within a communication system can be based on. Examples of the different standards and/or specifications include, without limiting to these, specifications such as GSM (Global System for Mobile communications) or various GSM based systems (such as GPRS: General Packet Radio Service), AMPS (American Mobile Phone System), DAMPS (Digital AMPS), WCDMA (Wideband Code Division Multiple Access) or 3rd generation UMTS (Universal Mobile Telecommunications System), IMT 2000 (International Mobile Telecommunications 2000) and so on.
In a cellular communication system a base station serves mobile stations or other user equipment (UE) via a wireless interface. Each of the cells of the cellular system can be served by an appropriate transceiver apparatus. The wireless communication may be controlled by an appropriate radio access network controller. The access network controller may be connected to and controlled by another controller facility that is typically in the core network side of the communication system. An example of the core network controller is a serving GPRS support node (SGSN). The controller may be interconnected and there may be one or more gateway nodes for connecting the cellular network to other communication networks. For example, the SGSN may be connected to a Gateway GPRS support node (GGSN) for connecting the mobile network to the Internet and/or other packet switched networks.
In addition to transmitting data, the third generation telecommunication systems such as the UMTS enable also voice transmission over the packet data connection, for example Voice over Internet Protocol (VoIP) calls. So called PDP contexts can be used for the Internet Protocol (IP) based telephony. The term ‘PDP context’ typically refers to the part of the data connection or data bearer that goes through the packet switched network (e.g. the GPRS/UMTS network). The PDP context can be seen as a logical connection or “pipe” from the wireless station to the access point of a gateway node, such as the GGSN, the access point being the connection point between the packet switched network (e.g. GPRS/UMTS mobile network) and an external data network. The PDP context may also be referred to, instead of the term logical connection, as a logical association between the access point and the user equipment (UE).
For example, in a Session Initiation Protocol (SIP) call set-up in the 3rd generation UMTS networks, a Packet Data Protocol (PDP) context will have to be established before the actual call is established (i.e. before the phone starts alerting the user thereof) to ensure that necessary resources for the connection are available. However, the inventor has found that the reserved data bearer resources may enable transmission of data on the PDP context while the phone is still alerting the user thereof. This may occur e.g. since a PDP context can be set up without restricting the use thereof in any way. Thus the user may be able to have a full voice call or other data transmission already during the alerting time. This may be disadvantageous, at least from the operators pint of view, as the alerting or ringing time is usually not charged from the caller or receiver of a call. Therefore it could be advantageous to have a possibility to either prevent the user from sending data before the call is established or at least to be able to detect and gather information regarding data transmission during the call set-up proceedings so that it is possible later on to determine whether any charges have incurred during the call establishment proceedings.
Instead of enabling this, the current call establishment procedures are adapted to optimise usage of resources. A possibility could be to proceed the call set-up procedure such that no radio bearer is established before the call set-up is completed. Another possibility could be that although the resources on the radio bearer may be pre-reserved, the resources cannot be used for data transmission until the connection set-up is completed.
However, these possibilities may have some drawbacks. One of the possible drawbacks is long post-pickup delay. The radio bearer has to be either modified or established after the incoming call is answered e.g. by picking the phone up. Furthermore, it may be that ring-back tone cannot be played by the network. If no radio bearer is established on the side of the calling party while the phone alerts, then it may not be possible for the network to play the ring-back tone (as is currently the case e.g. in a GSM system). This means that the ring-back tone would have to be generated by the phone itself. This may prevent the network from using any network-specific ring-back tones. In addition, announcements cannot typically be played without prior establishment of the radio bearer. If an announcement has to be played by the network, it is typically necessary to establish/modify the radio bearer first. The simplest and most usual case where this applies is the busy signal, but there are many other announcements which may be sent between the phone and the network.
Not all wireless data communication system enable “pre-reservation” of resources on the radio bearer. If the radio resources are not reserved or at least “pre-reserved” before the call is established, then it is possible that the user attempts to answer the call e.g. by picking up the phone, and then, if the attempt to establish the radio bearer fails, the call is dropped. This is a situation that should be avoided.