Investigation effect of phase noise of OFDM system and realization LO (local oscillator) with and without phase locked loop (PLL)

A phase locked loop (PLL) operates on the serialized received modulation symbols and provides an independent phase correction value for each received modulation symbol. Each received modulation symbol is corrected with its own phase correction value to obtain a phase-corrected symbol. The phase error in each phase-corrected symbol is detected to obtain a phase error estimate for that phase-corrected symbol. Orthogonal Frequency Division Multiplexing (OFDM) technique has received a great attention and has been widely used in the wireless communication systems for its high spectrum efficiency and robustness to the narrowband interference and multipath fading. OFDM can provide enormous data rates with sufficient robustness to radio channel impairments. Orthogonal frequency division multiplexing is one of the multi-carrier modulation (MCM) techniques that transmit signals through multiple carriers. These carriers (subcarriers) have different frequencies and they are orthogonal to each other. But it yields however some disadvantages too, one being an increased sensitivity to phase noise, which is generated in the local oscillators. The phase-corrected symbols are not correlated because independent phase correction values are used for the received. In this Paper, We are investigating the effect of phase noise upon OFDM system and realized local oscillator (LO)by using phase locked loop (PLL)[1][2]. Then system performance is evaluated as a degradation of the effective signal-to-noise ratio due to phase noise, in terms of BER simulations with and without PLL for different channel conditions.