t units have an average BER better than a specified BER limit. As opposed to TIS measurements, AFS is measured under real-time fad- ing conditions. This means that the mode stirrers are continuously moved during the measurement sequence, while the output power of the base station simulator is fixed. By doing this, the test unit will effectively experience a signal varying with Rayleigh distributed amplitudes. Due to the multiple reflections in the reverberation chamber and the constantly moving stirrers, it is important to have control of the time domain properties of the channel created in the chamber, which may have an effect on the measured BER. This effect may be wanted or unwanted, depending on the specific test situa- tion. For measurements where only noise impairment is considered, it is important to test that there are no irreducible bit errors present (e.g., by a similar procedure as mentioned in the TIS section). It is worth noting that, for AFS measurements © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology where SNR is the limiting factor, TIS can be derived from the AFS value because there is a theoretical connection between the two values. The instrumentation and setup for AFS measurements are the same as for the TIS measurements. The procedure can be performed in the following way: Perform the calibration measurement procedure as described in the cali- bration measurement section, including the calculations of mismatch and reference transfer function. Measure the transmission loss of the cable connecting the base station sim- ulator to the fixed-measurement antenna. Page the test unit, direct it to the traffic channel of interest, and put it in loopback mode to enable BER measurement. Place the test unit in the chamber. In the case of simulated-use testing, place the unit in the intended position relative to the tissue-simulating object (e.g., head or hand phantom). Set the base station simulator to a specific output power. The output power of the base