 modem in order to connect to a PC)-see Figures 12.2 and 12.3. 12.1.2.1 Mobile Network The PLMN was formed of real equipment starting with core network components (see Figure 12.1): SGSN, MSC (HLR-Home Location Register and VLR-Visitor Location Register), GGSN and continuing with the GSM-UMTS/GPRS Enhanced Radio Access Network. All these components are interconnected but transmission errors can occur by interferences, deficient network processing, and SO on. The interfaces used for data transmission [14-16] cover the physical range from air (radio waves), to electrical and optical: Uu/Um air interfaces for GSM/GPRS/ UMTS, optical UMTS interfaces lub, Iu, Iur, Ethernet electrical/optical Interfaces Gn and Gi. Most of the tests were performed on a GPRS/EDGE platform. Service Delivery Platforms From the radio access point of view, the transmission is Up Link (UL) if it is from the mobile terminal towards the network and Down Link (DL) if it is vice versa. Generally, the network improvements are applied first to the DL, in order to enlarge the download bandwidth. Enhanced Data Rates for GSM Evolution (EDGE) is a bolt-on enhancement of the 2G/2.5 GSM. Data Rates possible for DL are up to 236.8 kbit/s for 4 timeslots (theoretical maximum is 473.6 kbit/s for 8 timeslots) in the packet mode. After Context Activation is accepted by the network at the request of the mobile terminal (for a valid SIM/subscriber) the mobile/subscriber and the PC attached to it via USB/Bluetooth are able to communicate on the Internet or with other subscribers in the network based on the IP (assigned by the GGSN). At the other end, the sta- tion or client (depending on the situation, see Figure 12.2) are connected on the Gi Interface/Internet. 12.1.2.2 Data Acquisition: The Digital Oscilloscope Data were acquired using a Digital Oscilloscope [17] (see Figure 12.4) either on simulated data (in the "demo mode") or with real measurement. The oscilloscope Oscilloscope File Edit Options View Math Help Oscilloscope Spectrum Analyzer Transient Record