This paper gives a brief idea of how the mobile communication has evolved, its generations. Different generations have been developing since then each generation coming out overcoming previous generation drawbacks. One such technology in fourth generation is OFDM. OFDM based technique looks more promising as a 4G standard surpassing the 3G standards .So, a complete review of OFDM is provided explaining its spectrum utilization, transmitter, receiver, its mathematical description, advantages and disadvantages. This paper presents how signals are multiplexed using OFDM and transmitted using MIMO technology. We discussed MIMO technology, its transmission, advantages and disadvantages. Different multiple access techniques like TDMA, FDMA, CDMA, SDMA are discussed. And finally the various fields that are being explored to improve the utility of 4G systems.
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