OFDM/DPSK System Performance Improvement in the Presence of Frequency Offset using a Reconfigurable Detection Algorithm

摘要

The popularity of OFDM systems is rising due to its ability to support high-data-rate transmission over time-variant multipath fading channels. OFDM transmission techniques have found applications in the two digital terrestrial broadcasting services - digital audio broadcasting (DAB) and digital terrestrial video broadcasting (DTVB) [1, 2]. OFDM is used in the standards for wireless local area networks [3]. Asymmetric digital subscriber lines (ADSL) based on OFDM technology are used to deliver high-rate digital data over existing plain old telephone lines [4]. OFDM can also serve as an alternative transmission method to DECT-like digital cordless systems [5]. One of the challenging problems faced in the design of OFDM systems is the frequency offset between the local oscillators at the transmitter and the receiver [6, 7]. The frequency offset destroys the orthogonality of the OFDM subcarriers, arising from discrete orthogonal transforms [8], and therefore creates Inter-Carrier Interference (ICI). The sensitivity of OFDM to the frequency offset is the major factor limiting the use of OFDM at smaller carrier spacing. To mitigate this effect two types of solutions have been proposed in the literature: Frequency Offset Estimation and Self-Cancellation [9].