real/Wireshark measurement of the EDGE UDP transfer (bps) on client side (receiving) for Time/Div. from 100 to 2 ms. Tele-Measurement Services for m-Learning 12.1.3.2.2 EDGE UL Access on UDP It uses the scenarios as in Figure 12.2b. The bandwidth is investigated first, using Jperf/Iperf both at the probe and at the client (Figure 12.11). The same phenomenon can be observed for UDP as for TCP, the buffers at the server first fill up, then they are emptied causing a peak in the traffic. It can be seen that the network accepts very short peaks of data. The available bandwidth is smaller in UL than in DL (because usually fewer radio channels are available for DL than for UL) but the overall behavior is similar to the DL case. One can notice that jitter is not constant at the beginning of the transmission due to the radio channels setup. The connection is reliable as soon as all the radio channels are setup, after a measured time of approximately 10 S. Concluding these technical considerations, the performance of the transmission was assessed at the upper OSI layers. The study was not done on the physical radio- wave characteristics, but to the service level provided by the radio capabilities. Nevertheless, we observed that, for all test scenarios, the setup period (~10 s) involved a large variation of the transmission rate due to the establishment of radio channels. Similar fluctuations were determined also by the interruptions caused by buffer filling (and unfilling). The performance of the streaming and the quality of measurement was given, in our case study, directly by the accuracy of the received data, as no modifications Time (s) Figure 12.11 Jperf/Iperf measurement of the bandwidth (kbps) on UL UDP for 61 kbps at the probe. Service Delivery Platforms were done on the communication channel. Data itself were completely discarded if transmission failed, with the advantage that no erroneous information was on display at the receiving side at any time. The disturbance in the packet-oriented network resulted in the 