We know, the main cause for signal deterioration in a communication channel is multipath fading. MIMO helps us to get the best quality signal and OFDM ofcourse helps in attaining lower Bandwidth

The “Orthogonal” part of the name refers to a precise mathematical relationship between the frequencies of the sub-channels that make up the OFDM system. Each of the frequencies is an integer multiple of a fundamental frequency. This ensures that even though the sub-channels overlap they do not interfere with each other. This results in high spectral efficiency. Also the use of IFFT and FFT for modulation and demodulation results in computationally efficient OFDM modems.

OFDM has many attractive features (as listed above) but it also has a few disadvantages. The peak-to-average-power ratio (PAPR) can be large which makes it difficult to construct energy-efficient power amplifiers. Furthermore, the cyclic prefix (which enables simple demodulation) wastes some resources that could have been used to transmit data.

That said, I believe that OFDM will continue to be the modulation of choice for quite some time.

is there any paper about frequency synchronization on MIMO OFDM system? thanks

Tyas Wulanarl: If you refer to the "carrier frequency offset" then there are plenty of papers. For example, "Blind Carrier Frequency Offset Estimation in SISO,

MIMO, and Multiuser OFDM Systems" by Yingwei Yao and Georgios B. Giannakis.

@ Tyas: This paper proposes a technique for frequency synchronization suitable in burst mode communication of MIMO-OFDM system:

https://www.researchgate.net/publication/2932331_Frequency_Synchronization_for_MIMO_OFDM_Wireless_LAN_Systems?ev=srch_pub

Article Frequency Synchronization for MIMO OFDM Wireless LAN Systems

I agree with Neeraj's version moreover, using MIMO , signal processing is exploiting the benifit from the channel , rather than having to remove its impact.

Also with OFDM the frequency domain provides an additional dimension in which channel coding can be applied to achieve immuinity against interference and noise.

The MIMO - OFDM combination is the best way to exploit the spatial diversity, time diversity and frequency diversity. This improves the overall system performance.

OFDM adds another dimension in Cellular technology in resource scheduling of multiple users in cellular network with cell frequency reuse efficiency of one by scheduling the suband frequencies with minimum interference

Almost every aspect related to ofdm is discussed above like mitigation the effect of multipath fadings, and problems associated with ofdm are carrier frequency offset, High PAPR, bandwidth efficiency is poor because of cyclic prefixing etc. While we process input signal to ofdm the first part is to convert input signal into parallel stream and effectively time required to process one bit increases and effect of ISI also not introduced and if we intoduce wavelet instead of fft then bandwidth effiency will increase as cyclic prefixing can be avoided in wavelet ofdm. MIMO exploites multipath environment for increasing data rate which is possible with space time coding techniques. MIMO and wavelet based OFDM can give better results.