ofdm & cognitive radio
DESCRIPTION
Communication EngineeringTRANSCRIPT
A Talk on
Carrier Frequency Offset Estimation for Non-Contiguous
OFDM Receiver in Cognitive Radio Systems
Presented By: Md. Shahidullah KawsarEEE, Khulna University of Engineering & Technology
Source: GLOBECOM 2013 IEEE, Georgia, USA
System model: Cognitive Radio & NC-OFDM Importance of CFO estimation Proposed scheme for CFO estimation Simulation Results Future work opportunity
Outlines
Cognitive Radio (CR)
Possible Applications
Mobile multimedia downloads.Emergency communications services.Broadband wireless networking.Multimedia wireless networking services.
A Software Defined Radio (SDR) with a Cognitive Engine Brain
NC-OFDM: Non-Contiguous Orthogonal Frequency Division Multiplexing
NC-OFDM is normal OFDM with a mask just as string of 1s and 0sindicates the presence or absence of a carrier.
Applications
To acquire (SSI) SpectrumSynchronization Information.
To suppress the carriers whichinterfere with the primarytransmission.
Why do we estimate Carrier Frequency Offset (CFO)?
CFO means frequency error in OFDM systems.
Causes of CFO
Frequency differences between the transmitter and receiver oscillators.
Doppler shift of mobile channels.
Oscillator instabilities.
Categories of CFO
Fractional CFO: It introduces Inter-Carrier Interference (ICI) andresults in Bit Error Rate (BER)degradation.
Integer CFO: It introduces a cyclicshift of data sub-carriers and aphase change.
Proposed scheme for CFO estimation
To verify the accuracy
[A] Hard-Decision-Based Active Subchannel Detection
To distinguish active subchannels from inactive ones
[B] HDD Based MLE Algorithm
To recover the CFO
[C] Cramer-Rao lower Bound with Ideal SSI
MSEE vs SNR with SIR = 0dBMSEE: Mean Square Estimation ErrorSNR: Signal to Noise RatioSIR: Signal to Interference Ratio
MSEE vs SNR with SIR = -6 dB
MSEE vs SIR with SNR = 10 dB
MSEE vs Active Subchannel Ratio with SNR = 10 dB & SIR = 0dB
Conclusion
In order to estimate CFO: HDD is used to distinguish active subchannels from inactive ones. HDD based MLE algorithm is used to recover the CFO. Corresponding CRB with Ideal SSI to verify the accuracy.
Simulation results: Similar MSEE as the relevant CRB when a broad range of SIR is
considered. to set up the SSI and decode the received code bits successfully at
the CR receiver.
Thank You