21-07-2014, 03:35 PM
PHASE NOISE COMPENSATION IN
OFDM BASED COMMUNICATION SYSTEM
[attachment=66080]
OBJECTIVE
AIM- To compensate the effects of phase noise in OFDM based communication system and enhanced the performance of the system in terms of Bit error rate (BER) by using RS coding with LSA channel estimation technique.
Primary objectives:
To analysis the BER Performance of Uncoded OFDM system without considering PHN.
To analysis the BER performance of Uncoded OFDM system at different values of PHN.
To analysis the comparision between Uncoded OFDM and RS coded OFDM system at different values of PHN .
To analysis the comparision between RS coded OFDM and RS coded with LSA channel Estimated OFDM system at different values of PHN.
INTRODUCTION
With the rapid growth of digital communication in recent years, the need for high speed data transmission is increased.
OFDM is a promising candidate for achieving high data rates in mobile environment because of its multicarrier modulation technique and ability to convert a frequency selective fading channel into several nearly flat fading channels
OFDM is a multicarrier transmission technique, which divides the bandwidth into many carriers . Each one is modulated by a low rate data stream.
OFDM
Basic idea
A form of Multi Carrier Modulation
Divide one wide frequency channel into several component sub channels
Multiplex multiple sub channels into one fast combined channel
Different symbols are transmitted over different subcarriers
Spectra overlap, but signals are orthogonal
FDM vs. OFDM
FDM needs guard bands. But OFDM use overlapping subcarriers to avoid wasteful guard bands
Data rate and Bandwidth efficiency of FDM is lower than OFDM
CDMA vs. OFDM
CDMA transforms multiple transmissions onto a single carrier (more complicated than OFDM)
OFDM encodes a single transmission into multiple subcarriers
PROBLEM FORMULATION
Local oscillator of transmitter and receiver inherently produce high levels of phase noise
Phase noise is the frequency domain representation of rapid, short-term, random fluctuations in the phase of a waveform, caused by time domain instabilities
Phase noise cannot be removed by filtering without also removing the oscillation signal. And since it is predominantly in the phase, it cannot be removed with a limiter. so phase noise removing is a major problem in OFDM
The phase noise in the local oscillator of transmitter and receiver affects on the orthogonality between the adjacent subcarriers and finally increases inter sub-carrier interference(ICI) . This ICI degrades the bit error rate (BER) performance of the system.
Phase noice is typically expressed in units of dBc/Hz(dB below the carrier per Hz of bandwidth)
OFDM BASED COMMUNICATION SYSTEM
[attachment=66080]
OBJECTIVE
AIM- To compensate the effects of phase noise in OFDM based communication system and enhanced the performance of the system in terms of Bit error rate (BER) by using RS coding with LSA channel estimation technique.
Primary objectives:
To analysis the BER Performance of Uncoded OFDM system without considering PHN.
To analysis the BER performance of Uncoded OFDM system at different values of PHN.
To analysis the comparision between Uncoded OFDM and RS coded OFDM system at different values of PHN .
To analysis the comparision between RS coded OFDM and RS coded with LSA channel Estimated OFDM system at different values of PHN.
INTRODUCTION
With the rapid growth of digital communication in recent years, the need for high speed data transmission is increased.
OFDM is a promising candidate for achieving high data rates in mobile environment because of its multicarrier modulation technique and ability to convert a frequency selective fading channel into several nearly flat fading channels
OFDM is a multicarrier transmission technique, which divides the bandwidth into many carriers . Each one is modulated by a low rate data stream.
OFDM
Basic idea
A form of Multi Carrier Modulation
Divide one wide frequency channel into several component sub channels
Multiplex multiple sub channels into one fast combined channel
Different symbols are transmitted over different subcarriers
Spectra overlap, but signals are orthogonal
FDM vs. OFDM
FDM needs guard bands. But OFDM use overlapping subcarriers to avoid wasteful guard bands
Data rate and Bandwidth efficiency of FDM is lower than OFDM
CDMA vs. OFDM
CDMA transforms multiple transmissions onto a single carrier (more complicated than OFDM)
OFDM encodes a single transmission into multiple subcarriers
PROBLEM FORMULATION
Local oscillator of transmitter and receiver inherently produce high levels of phase noise
Phase noise is the frequency domain representation of rapid, short-term, random fluctuations in the phase of a waveform, caused by time domain instabilities
Phase noise cannot be removed by filtering without also removing the oscillation signal. And since it is predominantly in the phase, it cannot be removed with a limiter. so phase noise removing is a major problem in OFDM
The phase noise in the local oscillator of transmitter and receiver affects on the orthogonality between the adjacent subcarriers and finally increases inter sub-carrier interference(ICI) . This ICI degrades the bit error rate (BER) performance of the system.
Phase noice is typically expressed in units of dBc/Hz(dB below the carrier per Hz of bandwidth)