Mitigating Phase Noise Effects in Orthogonal Frequency Division Multiplexing System Using Phase Locked Loop
Ojasvi Bhatia1, Yogesh Kumar Gupta2
1Ojasvi Bhatia, Department of Electronics and Communications Engg and Electrical Engineering,  Agra, India.
2Yogesh Kumar Gupta, Department of Electronics and Communications Engg and Electrical Engineering,  Agra, India.
Manuscript received on May 17, 2013. | Revised Manuscript received on June 09, 2013. | Manuscript published on June 30, 2013. | PP: 48-51 | Volume-2, Issue-5, June 2013. | Retrieval Number: E1670062513/2013©BEIESP

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Abstract: Orthogonal Frequency Division Multiplexing System are better suited to the today’s generation 3G networks and upcoming 4G networks in terms of bandwidth efficiency due to overlapping of frequency bands, high speed data transfer due to parallel data transfer, maintaining high quality of wireless link even under multipath conditions due to low symbol rate it minimizes ISI effects. The application of channel codes like convolution codes further reduces the Bit Error Rate and improves the link reliability. Although OFDM systems shows superior performance over single carrier and FDM system but there is one disadvantage that is the over sensitivity to Phase noise of the local oscillator which hinders the orthogonality of the sub carriers and increases inter carrier interference. OFDM system performance is degraded due to phase noise. Accordingly going deep into the various parameters of the OFDM system it was observed that Phase Locked Loop (PLL) could better control the phase noise problem in comparison to free running oscillator. It is deployed at the downlink side of incoming signal received from Antenna generating its own local frequency slightly higher than the incoming frequency to generate IF signal (after mixing the incoming and the local frequency) for further processing. Accordingly to examine closely the other aspects of PLL in relation to Free Running Local Oscillator various parameters of PLL in relation to OFDM system were studied in detail.
Keywords: Bit Error Rate, Signal to Noise Ratio, Phase Locked Loop, Power spectral densitys.