s digital cellular from. In addition each message will have a timestamp associated systems. 61/22 Telecommunication system measurements such as gaussian minimum shift keying (GMSK). Various forms of coding including high redundancy error correcting techniques are in 61.7 Analogue cellular test equipment In addition to all the conventional r.f. and a.f. measurements, test equipment for cellular radio mobiles must also be capable of testing the various signalling procedures. As a minimum requirement, it must be possible to simulate the base station function to the extent of opening the normal voice channel SO that conventional measurements can be performed. It may also be necessary to analyse the actual bit streams of the Figure 61.20 A seven cell cliuster messages in order to detect single bit errors in the transmitted data. With a view to simulating the effects of interference in practical systems, the test equipment should also be capable of generating special code sequences, for example, with implanted errors. In the past this was done using discrete instrumentation controlled 61.6.1 Data signalling via computer. Today it is more commonly performed by integrated Radiotelephone Test Sets. The management of the mobile network calls for information ex- change between the mobiles and the base stations in each cell or 61.7.1 Analogue cellular test set cluster of cells. Among the procedures to be handled in this way we can identify: The cellular radio test set generates and analyses all data signals required to simulate the cellular base station. It must also provide 1. Selection of r.f. channels. all the facilities required for r.f. and a.f. measurements on the radio 2. Transfer of call numbers. itself. For example, the Rohde and Schwarz CMTA provides these 3. Transmitter power level control. functions. Special signalling firmware is installed for the common 4. Handover of mobile between cells. cellular systems. These are AMPS, TACS, Radiocom 2000, 5. Registration and call charging. NMT450/900 and Network C. A typic