OFDM Equalization

1
OFDM Equalization IQ-Imbalance Compensation in
the Presence of IBI and CFO

• R94944007
• Kuo-Hsing Juan

2
OFDM

• OFDM (Orthogonal Frequency Division Multiplexing)
• Use N overlapped orthogonal sub-carriers to carry
  information

3
CFO

• CFO (Carrier Frequency Offset)
• Local oscillators are not synchronized well
• Introduce ICI
• (results in the
• data disturbance)

4
IBI

• IBI (Inter Block Interference)
• Wireless channels are usually multi-path fading
  channels
• If the channel impulse response length is larger
  than the guard interval length in OFDM systems,
  this results in IBI.

5
IQ-Imbalance

• IQ-imbalance arises when the signal in I and Q
  channels do not meet the orthogonality and the
  power balance.

6
Motivation

• The analog front-end imperfections (IQ-Imbalance
  and CFO) and poor channel condition (IBI effect)
  cause a severe degradation in performance for
  OFDM systems.
• Study the equalization techniques that are robust
  against the imperfections.

7
Plan

• Model the channel condition and OFDM system
• Take CFO, IBI and IQ-Imbalance into consideration
• Study the equalization techniques
• Implement the equalization techniques
• Simulation

8
Reference

• 1 Jui-Yuan Yu, Ming-Fu Sun, Terng-Yin Hsu,
  Chen-Yi Lee, "A novel technique for I/Q imbalance
  and CFO compensation in OFDM systems," 2005 IEEE
  International Symposium on Circuits and Systems,
  pp. 6030- 6033, vol. 6, 23-26 May 2005
• 2 I. Barhumi, M. Moonen, "IQ-Imbalance
  Compensation for OFDM in the Presence of IBI and
  Carrier-Frequency Offset," IEEE Transactions on
  Signal Processing, vol.55, no.1, pp.256-266, Jan.
  2007
• 3 J. Tubbax, A. Fort, L. Van der Perre, S.
  Donnay, M. Engels, M. Moonen, H. De Man, "Joint
  compensation of IQ imbalance and frequency offset
  in OFDM systems," 2003 Global Telecommunications
  Conference, vol.4, pp. 2365- 2369, 1-5 Dec. 2003