Compensation of cascaded radio impairments in MIMO-OFDM systems with direct-conversion architecture

Abstract

Direct-conversion radio architecture is a low-cost, small-size design for the analog front-end subsystem in a wireless communication transceiver. This architecture, however, induces radio impairments such as I-Q imbalance and dc offset that, along with frequency offset, incur severe degradation in communication performance. This paper aims to improve the performance of estimation and compensation for cascaded transmitter and receiver radio impairments in the MIMO-OFDM (multiple-input, multiple-output orthogonal frequency-division multiplexing) systems. First, a novel two-stage compensation scheme is proposed which is applicable to a general form of MIMO operations with any number of transmit and receive antennas. Second, with a periodic training, an improved low-complexity joint estimation and compensation algorithm for radio impairments is proposed. Numerical results show the superiority of proposed method over the existing ones in bit error rate (BER) performance and training overhead.

Efficient Joint Estimation and Compensation of CFO, Tx/Rx Frequency-Selective I/Q Imbalance, and the MIMO Radio Channel in OFDM Systems

“…In contrast, most existing schemes apply different preambles for these two estimation procedures (e.g., [6,7,11,15]). Thus, compared to the preambles used in the reference works, our preamble is much more overhead efficient.…”

“…The most advanced state-of-the-art schemes considering CFO and both Tx-and Rx-frequency-selective I/Qimbalance in MIMO OFDM systems are those in [11,15] as well as in our previous work [16]. The drawback of the schemes in [11,15] is that the used preambles are not overhead and interference optimal.…”

“…The drawback of the schemes in [11,15] is that the used preambles are not overhead and interference optimal. Moreover, the estimation schemes in [11,15] require quite high computational complexity.…”

“…This scheme requires exhaustive numerical search and thus, results in high computational complexity. Improvements have been made by [6,7,11,15], where a closed-form linear least square (LLS) estimator and a suboptimal iterative estimator have been proposed, respectively. Both schemes have lower computational complexity than that in [2].…”

“…(ii) When designing the preamble, the orthogonality between different Tx antennas as well as between direct and image channels (see [19]) is taken into account, allowing better estimation accuracy than [11,15].…”