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Baseband compensation of transmitter and receiver IQ imbalance for OFDM in frequency selective fading channels

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  • Astronomy
  • Communication
  • Computer Science
  • Design


BASEBAND COMPENSATION OF TRANSMITTER AND RECEIVER IQ IMBALANCE FOR OFDM IN FREQUENCY SELECTIVE FADING CHANNELS Job C. Oostveen Philips Research Laboratories Eindhoven The Netherlands job.oostveen ABSTRACT In this paper, we present a baseband algorithm for estima- tion and compensation of transmitter and receiver IQ imbal- ance for OFDM in a frequency-selective fading channel. We show by simulations that the negative effect of IQ imbalance on system performance can be almost completely removed by the proposed algorithm. The algorithm is an iterative loop, consisting of consecutively channel estimation, Rx IQ imbalance estimation, Tx IQ imbalance estimation and data estimation. 1. INTRODUCTION Because of the strong price erosion in the market for wire- less local area network (WLAN) devices, it is crucial to de- velop low cost transceivers. One important way to do so is by ensuring a high level of integration, without requiring ex- ternal IF components like SAW filters. Zero-IF front-ends have the potential to fulfill that promise. On the other hand, Zero-IF front-ends are suffering relatively strong imperfec- tions, like for instance IQ imbalance. Modern communication standards, like the 802.11 a, g and n systems, have been developed to achieve high spectral efficiency. As a consequence, OFDM has become the mod- ulation technology of choice for many systems. In addition, each of the OFDM-subcarriers is modulated by a high-order QAM constellation, e.g. 64-QAM or 256-QAM. As a result, a high accuracy transmission is needed. It would take expensive RF designs to achieve the nec- essary accuracy in the front-ends of transmitter and receiver. This would potentially remove all advantages of the zero-IF receiver. Therefore, in this paper, we study the estimation and compensation of IQ imbalance by additional baseband processing at the receiver. The paradigm of estimating and compensating the IQ imbalance in baseband at the receiver is not new. A number of articles have b

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