Adaptive pilot based modulation identification and channel estimation for OFDM systems

Adaptive modulation is an important method for effective usage of channel capacity in Orthogonal Frequency Division Multiplexing (OFDM) systems. Modulation identification algorithms unnecessitate the need of transferring the modulation information to the receiver, thereby these algorithms are very effective methods to increase the channel capacity. However, in practice, separate two sets of pilot symbols are used to identify the modulation type and to estimate the channel impulse response. In this paper, we propose one set of pilot symbols to get information about the channel and the modulation type, jointly. These pilots are named as "adaptive pilots" because they are related with the modulation type. Monte Carlo simulations are performed to observe the performance of the proposed adaptive pilot method and to compare with previously presented algorithm given in [1]. Simulation results indicate that the proposed adaptive pilots successfully help to identify correctly the modulation type without affecting the performance of the channel estimation.