This paper studies control format indicator (CFI) estimation methods in 4G-LTE communication systems. CFI is an essential control signal in LTE, and must be correctly detected at the receiver to avoid degraded system performance. The standard method of CFI detection involves the use of the Maximum Likelihood (ML) estimation criterion. Unfortunately, ML decoding performance relies on accurate channel estimation, and as a consequence may result in poor CFI decoding when channel estimates are poor.
To improve CFI detection in severe fading channel conditions, a time-domain decision rule that requires no channel estimation, is proposed. Results show that when compared with the ML approach, the proposed method reduces the probability of CFI estimation error in the form of reduced block error rate.