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

R94944007 Kuo-Hsing Juan

OFDM

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

CFO

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

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.

IQ-Imbalance

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

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.

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

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