Performance of Admission Control Strategies for Dual Transfer Mode in EGPRS Networks

Dual transfer mode (DTM) has been defined by 3GPP for EGPRS networks. It provides simultaneous usage of GSM and GPRS services without requiring a full fledged GPRS class A terminal. DTM relies on the usage of half rate coders that make it possible to share a timeslot between a voice call and a data session. The data session can be extended to more time slots if necessary. This work examines an optimal policy adapted for resource allocation in a cell providing DTM capability. At the end of one part of a DTM call, the policy decides whether the released half slot should be reallocated to an existing data session or not. In earlier work, this optimal policy was proven to be a threshold strategy. The optimal policy is compared with the two policies where the same decision is taken regardless of the state of the system. Its performance is evaluated with respect to system load and configuration parameters