Preamble Based Joint CFO, Frequency-Selective I/Q-Imbalance and Channel Estimation and Compensation in MIMO OFDM Systems

Abstract

A very promising technical approach for future wireless communication systems is to combine MIMO OFDM and Direct (up/down) Conversion Architecture (DCA). However, while OFDM is sensitive to Carrier Frequency Offset (CFO), DCA is sensitive to I/Q-imbalance. Such RF impairments can seriously degrade the system performance. For the compensation of these impairments, a preamble-based scheme is proposed in this paper for the joint estimation of CFO, transmitter (Tx) and receiver (Rx) frequency-selective I/Q-imbalance and the MIMO channel. This preamble is constructed both in time- and frequency domain and requires much less overhead than the existing designs. Moreover, Closed-Form Estimators (CLFE) are allowed, enabling efficient implementation. The advantages and effectiveness of the proposed scheme have been verified by numerical simulations

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].…”

“…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.…”

Preamble design for estimation and compensation of channel distortion parameters 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 [4,5]. However, DCRs front-ends are sensitive to component imperfections due to manufacturing non-uniformity, resulting to radio frequency (RF) impairments such as in-phase and quadrature (I/Q) imbalances and the carrier frequency offset (CFO) [4][5][6][7][8][9].Since RF impairments are unavoidable in low-cost and low-power DCRs front-ends, then, to obtain better performance for such communication systems, efficient estimation and compensation for the RF impairments is crucial [5,10]. 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.…”