rference Normalization PathLoss Averaging the z-Superscript(1) (Kalman Filter) filtered info Interference Figure 8.12 Closed-loop control theoretic view on the link adaptation. The scheduler relies on channel measurements, which allow dynamic subcarrier assignment, adaptive power control, and adaptive modulation and coding. In this control circuit, the desired SINR of approximately 20 dB at the receiver is the target value. In border regions of the cell where the path loss is too high, limiters within the power control block reduce the actual SINR. The control is vectorized. Each subchannel is one element. subchannel. Interference, noise, and time-dependent path loss are disturbing values for which the control loop aims to compensate. In the lower part of the block diagram is the feedback loop. The BS (or RN) receives CQI measurements in regular intervals, which arrive delayed compared to the current state (block The received signal power is then normalized by the known transmit power SO that, after normalization, the path loss and interference measurements are available. A prediction unit processes the data and estimates the path loss for the short-term future on all subchannels. DSA is now done based on the path loss vector, assigning the best subchannels to each user (multidimensional control). On the chosen subchannels, the SINR at the UT is estimated, assuming the use of a nominal transmit power level. At the output of the comparator, it is now known if there was too much power (reduce it) or too little power (reduce the PhyMode in AMC). The reaction time of the control system is at least one round- trip time or two TTI frame lengths, depending on the frequency of CQI updates. © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology 8.4.4 Forward Error Correction (FEC) The PhyMode consists of modulation and coding. This coding allows for correcting some bit errors before further processing SO that the PDU is received without any packet errors. The performance is incor