Mobile transmitters I/Q imbalances in LTE uplink: Analysis and digital mitigation

The single-carrier frequency-division multiple access (SC-FDMA), also known as discrete Fourier transform (DFT)- spread OFDMA, has been adopted as uplink transmission scheme for the 3GPP Long Term Evolution (LTE). Such OFDM-based systems are known to be particularly sensitive to radio frequency (RF) impairments. The major sources of these RF impairments are in-phase and quadrature-phase imbalance (IQI) and carrier frequency offset (CFO). In this paper, we investigate the impact of radio impairments on the LTE uplink by mathematically formulating the received signal as a function of transmitted signals, IQI, CFO, and channel distortions. Then, two alternative joint equalization schemes are proposed for coping with such impairments, stemming from the minimum mean square error (MMSE) and the zero forcing (ZF) principles, respectively. LTE uplink computer simulations are then carried out to assess the validity and performance of the proposed equalizers. The results demonstrate that the proposed schemes significantly improve the uplink performance, the performance of the MMSE solution being very close to the zero RF impairments scenario.

[1]  Hüseyin Arslan,et al.  IQ Imbalance Correction for OFDMA Uplink Systems , 2009, 2009 IEEE International Conference on Communications.

[2]  Gerard Faria,et al.  DVB-H: Digital Broadcast Services to Handheld Devices , 2006, Proceedings of the IEEE.

[3]  A. Abidi.  Direct-conversion radio transceivers for digital communications , 1995, Proceedings ISSCC '95 - International Solid-State Circuits Conference.

[4]  Asad A. Abidi.  Direct-conversion radio transceivers for digital communications , 1995 .

[5]  F. E. Abd El-Samie,et al.  Carrier frequency offset problem in DCT-SC-FDMA systems: investigation and compensation , 2010, ICC 2010.

[6]  Mikko Valkama,et al.  3.9G Radio Reception with SC-FDMA Waveforms Under I/Q Imbalance , 2007, 2007 IEEE International Symposium on Circuits and Systems.

[7]  T.B. Sorensen,et al.  Extension of the ITU channel models for wideband (OFDM) systems , 2005, VTC-2005-Fall. 2005 IEEE 62nd Vehicular Technology Conference, 2005..

[8]  Mikko Valkama,et al.  On Circularity of Receiver Front-end Signals Under RF Impairments , 2011, EW.

[9]  Mikko Valkama,et al.  Advanced Receiver Design for Mitigating Multiple RF Impairments in OFDM Systems: Algorithms and RF Measurements , 2012, J. Electr. Comput. Eng..

[10]  Michele Morelli,et al.  Timing and frequency synchronization for the uplink of an OFDMA system , 2004, IEEE Transactions on Communications.

[11]  Ali H. Sayed,et al.  Joint compensation of transmitter and receiver impairments in OFDM systems , 2007, IEEE Transactions on Wireless Communications.

[12]  Khaled Ben Letaief,et al.  An interference-cancellation scheme for carrier frequency offsets correction in OFDMA systems , 2005, IEEE Transactions on Communications.

[13]  Xianhua Dai,et al.  Carrier frequency offset estimation and correction for OFDMA uplink , 2007, IET Commun..

[14]  Uwe Ladebusch,et al.  Terrestrial DVB (DVB-T): A Broadcast Technology for Stationary Portable and Mobile Use , 2006, Proceedings of the IEEE.

[15]  Hideaki Sakai,et al.  Analysis and Compensation of Transmitter IQ Imbalances in OFDMA and SC-FDMA Systems , 2009, IEEE Transactions on Signal Processing.

[16]  See-May Phoong,et al.  Joint estimation of transmitter and receiver I/Q imbalances, CFO, and channel response for OFDM systems , 2010, The 2010 International Conference on Green Circuits and Systems.

[17]  Heung-Gyoon Ryu,et al.  Suppression of ICI and MAI in SC-FDMA communication system with carrier frequency offsets , 2010, IEEE Transactions on Consumer Electronics.