Ofdm receiver design in the presence of frequency selective iq imbalance and CFO

Muhammad Asim, Mounir Ghogho, Desmond C. McLernon

Abstract: Direct conversion receivers (DCR) are the preferred choice for the RF front-end in modern communication devices. These devices are simple and cheap to implement but for the case of sensitive multicarrier systems these devices may not maintain the required level of performance as regards image rejection (IR), carrier frequency offset (CFO) and direct current offset. In the presence of this non-ideal behaviour it is not possible to achieve a high signal to interferer ratio (SIR). This situation necessitates the use of digital signal processing (DSP) schemes to efficiently mitigate these effects and also to relax the stringent requirements on receiver design. In this paper we study the design of a receiver architecture which can jointly estimate the channel impulse response (CIR), IQ imbalance and CFO using long training sequences (LTS) which are already a part of WLAN standards. The proposed schemes provide an excellent performance/complexity tradeoff.