ower normalized by transmission bandwidth) for each data and control subchannel below a certain level that is determined by the maximum permissible power level for the MS, emission mask, and other regulatory constraints. In other words, when the number of active logical resource units assigned to a particular user is reduced, the total transmitted power must be reduced proportionally by the MS in the absence of any additional change of power control parameters. When the number of resource blocks is increased, the total transmitted power must be proportionally increased such that the transmitted power level does not exceed the permissible power levels specified by the regulatory specifications. For interference level control, the information about the current interference level of each BS may be shared among the base CHAPTER 10 The IEEE 802. 16m Physical Layer (Part II) stations via backhaul. In an OFDMA system, the power per sub-carrier and per stream is calculated as follows: (10-19) where SINRtarget is the target uplink SINR, PT is the uplink transmit power level in dBm per stream and per sub-carrier for the current transmission, PL denotes the average downlink path loss calculated by the MS based on the total power received on the active subcarriers of the frame preamble which is inclusive of mobile station's antenna gain, PNI is the estimated average power level in dBm of the noise plus interference per sub-carrier at the BS as indicated in the AAI_ULPC-NI MAC control message, and Poffset is an MS-specific power correction factor which is controlled by the BS through power control signals. The power offset values for data and control are different and thereby are individually specified. The SINRtarg for the traffic channels is calculated as follows: (10-20) where SINR min is the required SINR for the minimum data rate expected by the BS (typically 0 dB), Y denotes the Interference over Thermal (IoT) control factor, SIRDL is the linear ratio of the downlink signal to interference power measured by the MS, a is