FIGURE 32 TEDS enhanced air interface protocol stack 3.2.1 IP packet data in TEDS The TETRA standard provides TETRA MSs with the means to support packet data, and the TEDS extends this to higher bit rates, adds new QoS features as well as some performance enhancing features. Multiple TETRA MSs may share a packet data channel (PDCH) assigned for the exchange of packet data between the BS and MSs. MSs contend for resource on the shared channel the BS – then allocates resource to individual MSs. TEDS extends this concept by providing guaranteed resources for packet data at regular intervals (scheduled access) by allowing MSs to indicate differing data priorities for their resource allocations (data priority) and by providing the BS with an efficient method to transmit resource allocations that fit around scheduled resources. Scheduled access provides an efficient method for the SwMI to accommodate regularly recurring intermittent data. 3.2.2 MEX layer The multimedia exchange (MEX) layer is an optional layer located above the MS SNDCP. The chief purpose of MEX layer is to manage the multiplexing of IP packets from multiple applications according to a relative MEX precedence so that, where delivery is limited by lack of channel resources, each application using MEX gets a prearranged share of the total resource (this is different from data priority). This is useful for controlling the relative flow rate of data packets serving different aspects of a multimedia application (e.g. audio and video). Applications using MEX connect to the TCP/UDP layers via a port number and IP address (i.e. a socket) for routing the application data and control signalling. The port specification eliminates the need for using a MEX layer at the SwMI. The MEX layer provides internal data precedence management for up to eight simultaneous applications. Each application can choose one of eight unique precedence levels. The MEX precedence mechanism consists of an application list, eight buffers and a precedence switch as shown in Fig. 33. 33 MEX precedence to PDP context activation, the application chooses the MEX precedence level. After an application chooses its MEX precedence, its payload is routed to a particular buffer. Each buffer output is connected to a precedence switch, which services highprecedence buffers more frequently than lower precedence buffers. In the example of Fig. 33, three applications have populated the precedence list. Application 1 data will be serviced eight times more frequently than application 3
FIGURE 32 TEDS enhanced air interface protocol stack 3.2.1 IP packet data in TEDS The TETRA standard provides TETRA MSs with the means to support packet data, and the TEDS extends this to higher bit rates, adds new QoS features as well as some performance enhancing features. Multiple TETRA MSs may share a packet data channel (PDCH) assigned for the exchange of packet data between the BS and MSs. MSs contend for resource on the shared channel – the BS then allocates resource to individual MSs. TEDS extends this concept by providing guaranteed resources for packet data at regular intervals (scheduled access) by allowing MSs to indicate differing data priorities for their resource allocations (data priority) and by providing the BS with an efficient method to transmit resource allocations that fit around scheduled resources. Scheduled access provides an efficient method for the SwMI to accommodate regularly recurring intermittent data. 3.2.2 MEX layer The multimedia exchange (MEX) layer is an optional layer located above the MS SNDCP. The chief purpose of MEX layer is to manage the multiplexing of IP packets from multiple applications according to a relative MEX precedence so that, where delivery is limited by lack of channel resources, each application using MEX gets a prearranged share of the total resource (this is different from data priority). This is useful for controlling the relative flow rate of data packets serving different aspects of a multimedia application (e.g. audio and video). Applications using MEX connect to the TCP/UDP layers via a port number and IP address (i.e. a socket) for routing the application data and control signalling. The port specification eliminates the need for using a MEX layer at the SwMI. The MEX layer provides internal data precedence management for up to eight simultaneous applications. Each application can choose one of eight unique precedence levels. The MEX precedence mechanism consists of an application list, eight buffers and a precedence switch as shown in Fig. 33. 33 MEX precedence to PDP context activation, the application chooses the MEX precedence level. After an application chooses its MEX precedence, its payload is routed to a particular buffer. Each buffer output is connected to a precedence switch, which services highprecedence buffers more frequently than lower precedence buffers. In the example of Fig. 33, three applications have populated the precedence list. Application 1 data will be serviced eight times more frequently than application 3
R12-WP5A-C-0079!N16!MSW-E.docx