Data packet numbering in mobile packet switched data transmission

A packet-switched telecommunications system which comprises a terminal and a fixed network, which comprises a network element supporting packet-switched data transmission, data packets being arranged to be sent between the terminal and the network element in the telecommunications system and the telecommunications protocol of the telecommunications system comprising a convergence protocol layer for converting user data packets into convergence protocol packets, and a link layer for transmitting convergence protocol packets as data units and for acknowledging the transmission, whereby in the transmission of data packets between the terminal and the network element the system is arranged to:

• define, by means of a counter in a transmitter, a transmit data packet number for the convergence protocol packets to be sent,
• transfer the convergence protocol packets to be sent to the link layer for transmission,
• define, by means of a counter in a receiver, a receive data packet number for received convergence protocol packets,
• acknowledge the received convergence protocol packets,
• add the transmit data packet number defined by the transmitter's counter to the convergence protocol packet to be sent in response to performance of a predetermined process of the telecommunications system, and
• update the value of the receiver's counter to correspond to said transmit data packet number of the convergence protocol packet.

A network element for a packet-switched telecommunication system, said network element being arranged to transmit data packets to a terminal supporting a packet-switched data transmission, said network element comprising:

• a counter for defining a transmit data packet number for the convergence protocol packets to be transmitted between the network element and the terminal;
• means for transferring the convergence protocol packets to be transmitted to the link layer to be transmitted;
• means for receiving acknowledgements of the received convergence protocol packets from said terminal;
• and
• means, responsive to performance of a predetermined process of the telecommunications system, for adding the transmit data packet number, defined by the counter, to the convergence protocol packet, to be sent to the terminal.

A terminal for a packet-switched telecommunication system, said terminal being arranged to transmit data packets to a network element supporting a packet-switched data transmission, said terminal comprising:

• a counter for defining a transmit data packet number for the convergence protocol packets to be transmitted between the terminal and the network element;
• means for transferring the convergence protocol packets to be transmitted to the link layer to be transmitted;
• means for receiving acknowledgements of the received convergence protocol packets form said network element;
• and
• means, responsive to performance of a predetermined process of the telecommunications system, for adding the transmit data packet number defined by the counter, to the convergence protocol packet to be sent to the network element.