Mimo

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MIMO IN WIRELESS COMMUNICATION

Wireless communication refers to the transfer of information between two or more points that are not physically connected. Distances between the two points can be short or as far as thousands or even millions of kilometers. Different ways can be used to establish wireless communication. Basically, antennas are used as transmitter and receiver in wireless communications like cellular telephones, satellite communications, radio broadcasting, etc. Despite many advantages of wireless communication there are many factors that affect the quality of wireless communication systems. In urban and indoor environments, there are many obstacles between the clear line-of-sight (LOS) between transmitter and receiver. Instead the signal is reflected along multiple paths before finally being received. Each of these bounces can introduce phase shifts, time delays, attenuations, and distortions at the receivers. These destructively and constructively interfere with one another at receiving antenna degrading the quality of signal sent. Many researches have been done to mitigate this problem. One of the most prominent ways is to use MIMO techniques. MIMO (Multiple Input and Multiple Output) is a technique in which multiple antennas are used both at the receiver and the transmitter for better communication performance. In 1996, Greg Raleigh and Gerard J. Foschini refined new approaches to MIMO technology, considering a configuration where multiple transmit antennas are co-located at one transmitter to improve the link throughput effectively. It is been said that MIMO offers significant increase in data throughput and quality without additional bandwidth or increased transmit power. It achieves this goal by spreading the same total transmit power over the antennas to achieve an array gain that improves the spectral efficiency (more bits per second per hertz of bandwidth) or to achieve a diversity gain that improves the link reliability. It mitigates...
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