Preamble design for joint estimation of CFO and I∕Q imbalance for direct conversion OFDM system

Preamble Design for Joint estimation of Channel, CFO and Receiver I/Q-Imbalance in OFDM Systems

“…The DCR is a promising approach as it provides a low cost and low power receiver implementation over the traditional superheterodyne receivers [1,2]. However, DCRs front-ends are sensitive to component imperfections due to manufacturing non-uniformity, resulting to radio frequency (RF) impairments such as inphase and quadrature (I/Q) imbalances and the carrier frequency offset (CFO) [1][2][3][4][5].…”

“…CFO and I/Q mismatch seriously degrade the system performance, and their estimation and compensation are generally difficult as they are entangled in the received signal. I/Qimbalance results in a mirroring effect while CFO destroys the orthogonality among the subcarriers in OFDM systems and gives rise to inter-carrier interferences (ICI) [2,3] .…”

“…In the literature, several algorithms for estimation of CFO, frequency selective channel and/or I/Q imbalance have been proposed (see [3][4][5] and the references therein). Most of the existing schemes are based on the estimation and compensation for individual I/Q imbalance and CFO by using specific preamble [1,[7][8][9].…”

“…In [3][4][5]10], several joint estimation schemes have been proposed to estimate I/Q imbalance as well as CFO. In [10], a low complexity joint estimation method for the preamble of repeated pattern in IEEE 802.11a has been proposed, however, the algorithm in [10] suffers from serious error propagation problem especially for large I/Q imbalances.…”

“…In [3,4] preamble structures for joint estimation of CFO and I/Q imbalance by using several repetitive symbols have been proposed. The method can efficiently estimate and compensate for these impairments, however the overhead is huge as the method requires several repeated symbols to perfectly compensate for the CFO.…”