GPRS Quality of Service
The Quality of Service QoS requirements of typical mobile packet data applications are very diverse. For example, different GPRS applications like realtime multimedia, Web browsing, and e-mail transfer need a different QoS support. This QoS becomes a very important feature of GPRS services.
GPRS allows defining QoS profiles using the parameters service precedence, reliability, delay, and throughput. These parameters are described below:
The service precedence is the priority of a service in relation to another service. There exist three levels of priority: high, normal, and low.
The reliability indicates the transmission characteristics required by an application. Three reliability classes are defined which guarantee certain maximum values for the probability of loss, duplication, mis-sequencing, and corruption of packets.
The delay is defined as the end-to-end transfer time between two communicating mobile stations or between a mobile station and the Gi interface to an external packet data network.
This includes all delays within the GPRS network, e.g., the delay for request and assignment of radio resources and the transit delay in the GPRS backbone network. Transfer delays outside the GPRS network, e.g., in external transit networks, are not taken into account.
The throughput specifies the maximum/peak bit rate and the mean bit rate.
Using these QoS classes, QoS profiles can be negotiated between the mobile user and the network for each session, depending on the QoS demand and the current available resources.
The billing of the service is then based on the transmitted data volume, the type of service, and the chosen QoS profile.