IQ-imbalance compensation for OFDM in the presence of IBI and carrier-frequency offset

Imad Barhumi, Marc Moonen

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


In this paper, we propose a frequency-domain equalization technique for orthogonal frequency division multiplexing (OFDM) transmission over frequency-selective channels. We consider the case where the receiver analog front-end suffers from IQ-imbalance and the local oscillator suffers from carrier-frequency offset (CFO). While the IQ-imbalance results in a mirroring effect, the CFO induces inter-carrier interference (ICI). In addition to ICI, we consider the channel delay spread is larger than the cyclic prefix (CP). This means that inter-block interference (IBI) is present. The frequency-domain equalizer is obtained by transferring a time-domain equalizer (TEQ) to the frequency-domain resulting in a per-tone equalizer (PTEQ). Due to the presence of IQ-imbalance the conventional TEQ (where only one TEQ is applied to the received sequence) is not sufficient to cope with the mirroring effect. A sufficient TEQ consists of two time-domain filters; one applied to the received sequence and another applied to a conjugated version of the received sequence. For the case of IQ-imbalance and CFO, the TEQs are designed according the basis expansion model (BEM) which showed to be able to cope with the ICI problem. Finally, in addition to the frequency-domain PTEQ design procedure, a training-based RLS type initialization scheme for direct per-tone equalization is also proposed.

Original languageEnglish
Pages (from-to)256-266
Number of pages11
JournalIEEE Transactions on Signal Processing
Issue number1
Publication statusPublished - Jan 2007


  • Basis expansion model (BME)
  • Carrier-frequency offset (CFO)
  • IQ-imbalance
  • Orthogonal frequency-division multiplexing (OFDM)
  • Per-tone equalizer (PTEQ)

ASJC Scopus subject areas

  • Signal Processing
  • Electrical and Electronic Engineering


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