Since Internet traffic is mostly bursty, we have implemented a slot release mechanism for GPRS MS. If the IFQ of the MS is empty and no packet is transmitted or received for four TDMA frames while the MS is holding a channel, we initiate a resource_release. The MS clears its tx_chan[] and rx_chan[] entries and sends a resource_release. On receipt of a resource_release, the BS purges its vlr_.up_table and vlr_.down_table entries. Only an MS can initiate a resource_release.
If the MS later wants to restart transmission, we send another resource_request. This request is treated on par with any other fresh requests by the BS. In the case of traffic from the BS to MS, the BS will allot fresh resources to the MS and send a resource_reply informing the MS.