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ency analyzer to measure and characterize the cable and antenna system. Several different measurement methods are used. The return loss and VSWR measurements are key measurements used in making cable and antenna measurements on the field. These measurements show the user the match of the system and if it conforms to system engineering specifications. The difference is that the VSWR displays the match of the system linearly and the return loss is specified in dB, with a maximum value of 60 dB as a perfect match. If the antenna reflects too much power the quality of the receiving signal decreases and the transceiver power amplifier can be destroyed. A return loss of a maximum of 15dB is a common limit for a cable and antenna system. Furthermore the Wiltron measurement system is equipped with a cable loss mode that displays the average cable loss of the swept frequency range. By placing a short on the end of the cable the measurement signal is reflected and the average loss can be computed. Return loss or VSWR measurements characterize the performance of the overall system. If one of them fails, the distance-to-failure (DTF) measurement can be used to check the system and to indicate the exact area of the fault. The DTF measurement sweeps in the frequency domain and using the Inverse Fast Fourier Transform (IFFT), the data can be converted from the frequency domain to the time domain. Together with the constant phase velocity, the distance to fault is calculated.

Another task done by the department of operation and maintenance is monitoring signal strengths at different locations. The company usually gets a phone call by some customer complaining about call drops or signal weakness in their area. The complaint is forwarded to the department of operation and maintenance, where then a team of usually two people go out to the specified area using a GPS system along with a mobile phone connected to a laptop. A software is used which monitors the signal through the cell phone, by attempting to make a call and checking the strength of the signal as well as monitoring the handovers occurring during a call, and when a call drop occurs. A report is then written regarding the problem at that area and is forwarded to the department of cell planning, where then they figure out a solution by either increasing the signal at a certain base station or even sometimes building a new base station.

If a cell phone is switched on but not in operation, it measures all radio frequencies of the GSM network and records the different signal strengths. Then the cell phone tunes the strongest signal, monitors the neighboring cells and transmits the collected information to the BSC, this is called the ideal mode. During a conversation, the mobile phone and the RBS perform signal strength measurements and send them also to the BSC. If a better signal is tunable, the BSC will accomplish a handover onto another cell, here the cell phone is in the active mode. To collect these data, the engineer needs a mobile measurement system. The system used is the TEMS equipment, consisting of a cell phone connected to a laptop and a special software tool. With the TEMS equipment the engineer is able to evaluate the signal strength of each neighboring base station. The software displays all information about the tuned and neighboring cells, namely the signal strength, the base station identification code, the used synchronization and the traffic channels