e-mobile Call base-mobile Channel handover Channel handover Channel handover Roaming Registration Registration Response time SAT 5.97/6.00/6.03kHz SAT 5.97/6.00/6.03kHz Tx power (3 levels) Tx power (8 levels) Tx power (8 levels) Message analysis Message analysis Message analysis Bit error implant Bit error implant Bit error implant Transmitter Power Frequency accuracy Modulation sensitivity Modulation frequency response Modulation distortion Adjacent- channel power (option), Receiver Sensitivity (S/N SINAD quieting) A.F. level A.F. frequency response A.F. distortion General Power supply voltage Power supply current drain 61/24 Telecommunication system measurements 1. Cellular networks: D-AMPS, PCN. The test equipment must, therefore, be able to generate and measure 2. Paging systems: ERMES. frequency hopping signals. 3. Cordless telephone: CT2, DECT. GSM employs a complex speech coder in order to reduce the data 4. Trunking networks. rate and hence bandwidth required by the system. The traditional 1kHz audio test tone is not considered a meaningful representation Some of the techniques in GSM have been used in other systems. of speech. New test methods employing data sequences have, there- For example, military radios may use frequency hopping. Digital fore, been developed. speech is widely used in telephony. The techniques that are used for GSM, the European digital mobile radio network, require test functions that cannot be handled 61.9 The OSI Model and GSM by conventional equipment. The following section shows the test standards for GSM with special reference to the radio path or The OSI model is a common method of describing any data trans- physical layer. The essential characteristics that this new generation mission system. For GSM applications it is shown in Figure 61.22. of test equipment must have, will then be derived. A more graphical representation is shown in Figure 61.23 Table 61.12 compares conventional and GSM measurements. 61.10 The radio path or Physical Layer 61.8.1.1 Time division multiple ac