Survey based on Channel Estimation in MIMO Techniques

In wireless communication system, Signals are distorted due to noise, fading of multipath and interference. Different methods are used to counteract such effects. By using the MIMO technique, effects of fading can be reduced. In these techniques multiple signals are transmitted and received through multiple antennas, the received signal can be distorted by fading. To retrieve the signal that is transmitted, received signal could be estimated by using channel estimation techniques. Space Time Block Codes (Alamouti code), Minimum Mean Square and Zero forcing are the channel estimation techniques for MIMO scheme. The paper mainly focuses to analyse and simulate the channel estimation technique with modulation techniques like BPSK schemes. In addition to that, simulation can be performed implemented in MATLAB.

Pilot Symbol Error Re - Orthogonalization in 2 × 2 MIMO Systems of Wireless Communication

A 2×2 MIMO wireless communication system with channel estimation is simulated, in which two transmit, and two receive antennas are employed. The orthogonal pilot signal approach is used for the channel estimation, where the Hadamard sequences are used for piloting. Data are modulated by coherent binary phase-shift keying, whereupon an orthogonal space-time block coding subsystem encodes information symbols by using the Alamouti code. Based on the simulation, it is ascertained a possibility to decrease the bit-error rate by substituting the Hadamard sequences for the sequences having irregular structures, and constituting the eight known orthogonal bases. Considering a de-orthogonalization caused by two any pilot sequence symbol errors, the bit-error rate is decreased by almost 2.9 %. If de-orthogonalizations are caused by two repeated indefinite, and definite pilot sequence symbol errors, the decrements are almost 16 % and 10 %, respectively. Whichever sequences are used for piloting, the 2×2 MIMO system is ascertained to be resistant to the de-orthogonalization if the frame is of 128 to 256 symbols piloted with 32 to 64 symbols, respectively.