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Makes efficient use of the spectrum by allowing overlap
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By dividing the channel into narrowband flat fading subchannels, OFDM is more resistant to frequency selective fading than single carrier systems are.
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Eliminates ISI and IFI through use of a cyclic prefix.
•
Using adequate channel coding and interleaving one can recover symbols lost due to the frequency selectivity of the channel.
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Channel equalization becomes simpler than by using adaptive equalization techniques with single carrier systems.
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In conjunction with differential modulation there is no need to implement a channel estimator.
•
Is less sensitive to sample timing offsets than single carrier systems are.
•
Provides good protection against cochannel interference and impulsive parasitic noise.
2.1.3 Drawbacks of OFDM: •
Unfortunately OFDM
is very sensitive to the synchronization errors such as
Carrier frequency offset (CFO), timing jitter and phase noise. •
The CFO arise mainly due to the Doppler shift. The effect is caused by the CFO reduce the signal amplitude and makes interference between the carriers.
• •
Phase noise resulted from the imperfection of the local oscillator (LO). Timing error would occur either when the clock signal is not correctly recovered or when sampling circuit is not perfect. Propagation delay of the IC also causes the timing error.
•
Another term is AWGN. It is introduced in the channel through which data is transmitted.
The purpose of this paper is analysis the Signal To Noise Ratio (SNR) by changing the CFO, timing jitter, phase noise. Analysis has been done from the graphs that have been plotted with the help of MATLAB Program. Another graph also shows the Bit Error Rate according to different SNR. 2.2 System Model and Description: