Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system is a new wireless broadband technology which has gained great popularity for its capability of high rate transmission and its robustness against multi-path fading and other channel impairments. Irrespective of the techniques being employed in wireless communication System (such as OFDM, MIMO, or MIMO-OFDM techniques) to combat the effects of the channel on the transmitted signals, the availability of the channel state information (CSI) at the receiver end of the communication system remains a crucial factor for effective functioning of these techniques as well as for the successful recovery of the transmitted signal. The major challenge faced in MIMO-OFDM systems is how to obtain the channel state information accurately and promptly for coherent detection of information symbols In this paper, Least Squares (LS) channel estimation and Discrete Prolate Spheroidal Sequences based channel estimation methods are implemented for 2x2 MIMO OFDM systems with Alamouti technique and their performance is compared. In order to improve the performance of the systems further, Adaptive Modulation concept is introduced. The simulation outcome shows that the performance of MIMO OFDM is much better than the conventional methods. © 2005 - 2013 JATIT & LLS. All rights reserved.