Fading is the most important drawback for wireless systems. One way to deal with the fading is to equip transmitter and receiver with more than one antenna, so-called MIMO. In MIMO, multiple copies of data are transmitted by each antenna of the transmitter. Also, these systems can be used for achieving higher data rates. In this case, each transmitted antenna send a stream of data. Based on MIMO for P2P communication, massive MIMO are proposed for cellular systems. In these systems, base station is equipped with numerous antennas while users use devices with only one antenna. Reliability, high rate information exchange and simplicity in processes are advantages of these systems. All of the mentioned advantages are based on the assumption that the channel state information is available at base station. Therefore, a method with proper accuracy for channel estimation should be established. One conventional way for channel estimation is using overlay (conventional) pilots. Pilots are sequence of symbols, known between transmitter (user) and receiver (BS). In channel estimation with overlay pilots, all the users send time-multiplexed sequence of data and pilot symbols together. Each user must use a pilot sequence orthogonal to the other pilot sequences used by other users. In TDD scenario, for downlink, due to reciprocity, downlink channel can be considered as the traose of the uplink channel. Due to the limited number of orthogonal pilot sequences, some users must use same pilot sequnces and this causes pilot contamination. Pilot contamination causes a big error in channel estimation and eclipse all system operations, specially in data detection and precoding processes. One suggested method for mitigating pilot contamination is using superimposed pilot for channel estimation. In this method, data and user-specific pilot sequences transmitted together in a same period of time and each transmitted symbol is the sum of the a data and a pilot symbol. In this thesis, a new scheme for channel estimation and data detection based on superimposed pilot will be presented. System is assumed to be a point to point MIMO scheme. Quality of channel estimation and data detection processes are evaluated using simulation results. Key Words: MIMO, channel state information, channel estimation, superimposed pilot
