| 摘要 |
<p>In mobile radio networks of second (GSM-GPRS) and third Generation (3G) a packet data service is provided. Packed data are transmitted on temporary connections named temporary block flow (TBF) set up in one or both the transmission directions independently. To open and maintain a TBF some dedicated resources shall be allocated by the network, for example: carrier, timeslots, codes (in case of CDMA), buffer memory for data queues. Mobiles shall forward to the network a request to open a TBF, while the the release automatically follows the end of the active session, when the network acknowledges the uplink radio block marked as the last. Due to the bursty nature of packet services, it can very well happen that packet data are delivered by the application layer not continuously in time but with some delay in between, like the case which after sending the last assumed data packet, the uplink TBF will be released, and that some time later a new data packet is delivered for transmission by the same application. This requires, if no downlink TBF is in progress, the opening of a new uplink TBF through the common channels, thus resulting more time consuming and less efficient. To delay the final release of the resources temporarily allocated to an uplink TBF, the network sends an acknowledgement message granting the last received uplink radio block, including in the ACK message content a valid extension field (Txxxx,E/D) containing a counting value of the radio frames passed since then. Then the network starts the extension counting (Txxxx) during which a request for the new uplink TBF from the mobile, or any downlink message involving the listening by the mobile, is valid up to said counting expires. The mobile receives via ACK message the extension field (Txxxx,E/D) and starts the extension counting during which it knows the resources allocated to uphold the uplink packet transmission are kept reserved by the network until said counting expires and that during that time it is allowed to request for new uplink TBF as well as the network can request for a downlink TBF (fig 10). <IMAGE></p> |
