Spatial multiplexing is required to configure MIMO antenna. Spatial multiplexing require a high data rate to split into multiple lower data rate stream is transmitted from different transmit antenna in the same frequency channel. If these signals arrive at the receiver antenna array with sufficiently different spatial signature, the receiver can separate these streams, creating parallel channel free. Spatial multiplexing is very powerful technique for increasing channel capacity at higher SNR [1]. The maximum number of spatial stream is limited by lesser number of antennas at the transmitter and receiver. To implement spatial multiplexing in MIMO based Mobile Ad-hoc network we can achieve up to eight times higher data rates compare to selecting only one user pair at a time [2]. To get more data rate we implement MIMO-OFDM scheme for MIMO based Mobile Ad-hoc networks. In this paper we implement a MIMO-OFDM system model for MIMO based mobile ad-hoc network and compare its BER (Bit Error rate) with different modulation technique. Keywords: ad hoc networks, , Multi Input Multi Output (MIMO), Spatial Multiplexing, OFDM, Bit Error Rate. 1. INTRODUCTION OFDM is a modulation Technique as well as multiplexing technique as it is divide a single high data rate stream into a number of lower rate streams that are data transmitted simultaneous over some narrow sub channel. OFDM is multi-carrier modulation technique for transmission of signals over wireless channels, which converts frequency selective fading channel into a collection of parallel fading sub channels. In time domain sub carriers are orthogonal and over lap in frequency domain which can save some band width rather than other modulation technique without causing ICI (Inter carrier Interference).OFDM system create high data rate with long symbol duration by combining low data rate multiple carrier that eliminate ISI. In this paper we implement a MIMO-OFDM system. OFDM reduces equalization complexity by implementing with IFFT at the transmitter and FFT at the receiver, that converts the wideband signal , affected by frequency selective fading into N narrowband flat fading signals. The beneficial since OFDM enables support of more antennas and large band widths since it simplifies equalization dramatically in MIMO system. Hence, the available bandwidth is utilized very efficiently in OFDM systems without Causing the ICI (inter-carrier interference). By combining multiple lowdata- rate sub-Carriers, OFDM systems can provide a composite high-data-rate with a long symbol duration. That helps to eliminate the ISI (inter-symbol interference), which often occurs along with signals of a short symbol duration in a multipath channel.
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