Present time demands for high-speed 4G broadband wireless network is enabled by the practice of multiple antennas at both the transmitter and receiver ends. The multiple-input multiple-output MIMO transmission creates parallel channels over the same time and frequency i.e. spatial multiplexing to achieve high capacity and link reliability without the need for additional power of spectrum. Thus, MIMO transmission exploits the multipath fading mechanism to increase data rate and system capacity. However, in order for MIMO systems to function, there has to be a means of “slicing” the carrier signal into multiple subcarriers that modulate the low-frequency information data. These parallel low-rate subcarriers can then be transmitted and received via the multiple antenna configurations. Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation technique that creates these parallel sub-channels that are low-rate or narrowband in nature. By inserting cyclic prefix between the sub-channels, orthogonality is maintained and inter-symbol interference is totally eliminated. Hence, a combination of MIMO and OFDM i.e. MIMO-OFDM not only drastically improves channel capacity and data rates, it also combats frequency-selective fading thereby improving link.

MIMO, OFDM, Spatial multiplexing and frequency selective fading

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