What is CFI (control format indicator)?

CFI is an indicator measure of OFDM symbols that are utilized for conveying control channels at each subframe. The Control Format Indicator value characterizes the time span, in OFDM symbols, of the Physical Downlink Control Channel transmission for a specific downlink subframe, in LTE. The CFI is sent utilizing the Physical Control Format Indicator Channel. The CFI is restricted to the value 1, 2, or 3. With more than ten resource blocks of bandwidths, the number of OFDM symbols utilized to contain the downlink control data is equivalent to the genuine CFI value.