A BLUE-Based Approach to Frequency Recovery in OFDM Receivers with I/Q Imbalance

Direct conversion receivers (DCRs) are an effective means to obtain user terminals with reduced cost, size, and power consumption. Their major drawback is the possible insertion of I/Q imbalances in the demodulated signal, which can seriously degrade the performance of conventional synchronization algorithms. In this paper, we investigate the problem of carrier frequency offset (CFO) recovery in an OFDM receiver equipped with a DCR front-end. Our approach is based on the best linear unbiased estimation (BLUE) theory and aims at jointly estimating the CFO, the useful signal component, and its mirror image. In doing so, we exploit knowledge of the pilot symbols transmitted within a conventional repeated training preamble appended in front of each data packet. Two solutions are proposed, and both of them provides the CFO in closed-form, thereby avoiding any grid-search procedure. The accuracy of the proposed methods is assessed in a scenario compliant with the 802.11a WLAN standard. Compared with existing solutions, the novel schemes achieve improved performance at the price of a marginal increase of the processing load.

[1]  Ananthram Swami,et al.  Training Design for CFO Estimation in OFDM Over Correlated Multipath Fading Channels , 2007, IEEE GLOBECOM 2007 - IEEE Global Telecommunications Conference.

[2]  Y. Lee,et al.  Preamble design for joint estimation of CFO and I/Q imbalance for direct conversion OFDM system , 2009, IET Commun..

[3]  Alfred O. Hero,et al.  Space-alternating generalized expectation-maximization algorithm , 1994, IEEE Trans. Signal Process..

[4]  Sailes K. Sengijpta.  Fundamentals of Statistical Signal Processing: Estimation Theory , 1995 .

[5]  Mounir Ghogho,et al.  Ofdm receiver design in the presence of frequency selective iq imbalance and CFO , 2013, 21st European Signal Processing Conference (EUSIPCO 2013).

[6]  Yong Hoon Lee,et al.  Joint ML estimation of carrier frequency, channel, I/Q mismatch, and DC offset in communication receivers , 2005, IEEE Transactions on Vehicular Technology.

[7]  Liesbet Van der Perre,et al.  Joint estimation of carrier frequency offset and IQ imbalance for 4G mobile wireless systems , 2006, 2006 IEEE International Conference on Communications.

[8]  Wei-Ping Zhu,et al.  Carrier frequency offset estimation for OFDM systems with I/Q imbalance , 2004, The 2004 47th Midwest Symposium on Circuits and Systems, 2004. MWSCAS '04..

[9]  Masayuki Kurosaki,et al.  Low complexity compensation of frequency dependent I/Q imbalance and carrier frequency offset for direct conversion receivers , 2010, Proceedings of 2010 IEEE International Symposium on Circuits and Systems.

[10]  Hai Lin,et al.  Repeated preamble based carrier frequency offset estimation in the presence of I/Q imbalance , 2012, 2012 IEEE International Conference on Communications (ICC).

[11]  Antonio A. D'Amico,et al.  Frequency Estimation in OFDM Direct-Conversion Receivers Using a Repeated Preamble , 2016, IEEE Transactions on Communications.

[12]  Wern-Ho Sheen,et al.  Joint Least Squares Estimation of Frequency, DC Offset, I-Q Imbalance, and Channel in MIMO Receivers , 2009, IEEE Transactions on Vehicular Technology.

[13]  Hai Lin,et al.  ESPRIT-Based Carrier Frequency Offset Estimation for OFDM Direct-Conversion Receivers , 2013, IEEE Communications Letters.

[14]  Hai Lin,et al.  Estimation and Compensation of CFO and I/Q Imbalance in OFDM Systems Under Timing Ambiguity , 2011, IEEE Transactions on Vehicular Technology.

[15]  Hui Liu,et al.  Frequency offset and I/Q imbalance compensation for direct-conversion receivers , 2005, IEEE Transactions on Wireless Communications.

[16]  Xiaolong Wang,et al.  Carrier Frequency Offset estimation in the Presence of I/Q Mismatch for Wideband OFDM systems , 2012, 2012 IEEE 55th International Midwest Symposium on Circuits and Systems (MWSCAS).

[17]  Umberto Mengali,et al.  An improved frequency offset estimator for OFDM applications , 1999, 1999 IEEE Communications Theory Mini-Conference (Cat. No.99EX352).

[18]  Marco Moretti,et al.  A SAGE Approach to Frequency Recovery in OFDM Direct-Conversion Receivers , 2014, IEEE Communications Letters.

[19]  See-May Phoong,et al.  A New Algorithm for Carrier Frequency Offset Estimation in the Presence of I/Q Imbalance , 2010, 2010 IEEE 71st Vehicular Technology Conference.

[20]  Hai Lin,et al.  Low-complexity pilot-aided compensation for carrier frequency offset and I/Q imbalance , 2010, IEEE Transactions on Communications.

[21]  Michael D. Zoltowski,et al.  OFDM blind carrier offset estimation: ESPRIT , 2000, IEEE Trans. Commun..

[22]  Teresa H. Y. Meng,et al.  Direct-conversion RF receiver design , 2001, IEEE Trans. Commun..

[23]  Marco Moretti,et al.  Carrier Frequency Offset Estimation for OFDM Direct-Conversion Receivers , 2012, IEEE Transactions on Wireless Communications.

[24]  Mikko Valkama,et al.  Advanced methods for I/Q imbalance compensation in communication receivers , 2001, IEEE Trans. Signal Process..

[25]  See-May Phoong,et al.  A Time-Domain Joint Estimation Algorithm for CFO and I/Q Imbalance in Wideband Direct-Conversion Receivers , 2012, IEEE Transactions on Wireless Communications.