 station simulator will determine the average power available for the test unit during the measurement. Put the mode stirrers in a constant movement mode and perform a BER measurement during the sequence. Adjust the number of bits tested SO that the BER measurement spans the full mode-stirrer sequence. Increase or decrease the base station output power as needed and repeat steps 5 and 6 until the lowest base station output power is found that gives a BER better than the specified target BER. This specific output power is denoted PBS,lim The AFS value is then found by applying the calibration correction data as in the following equation: (12.24) Alternatively, step 7 in the previous procedure can be replaced by performing steps 5 and 6 for a number of predefined output powers for the base station simula- tor. This will give a relation between available power and BER for the test unit; by interpolating the data points, the lowest average power needed for a BER better than the specified target limit can be determined. Among the advantages of AFS measurements are the potential for very fast sensitivity measurements and that the fading property of the measurement gives the possibility to test in a wide range of real-time conditions. The possibility to test in actual fading conditions is very important for modern, multiantenna systems where, for example, the effect of diversity will only show up in such a test. © 2009 by Taylor & Francis Group, LLC Measuring Performance of 3PPP LTE Terminals 12.3.5 Measuring Antenna Diversity Gain Diversity is a technique based on the use of more than one antenna that experiences different fading. By choosing or combining the signals of two different antennas, it is possibly to gain more than 10 dB of diversity gain in the worst fading dips appear- ing typically 1% of the time [49]. With additional antennas, even higher diversity gains are possible [50]. It is possible to measure diversity gain with drive tests (i.e., driving or walking with multiple antenna configurations through a fa