Orthogonal Frequency Division Multiplexed (OFDM) transmission schemes are widely used in digital communications, including wireless networking, television and audio broadcasting, internet access, etc. In an OFDM scheme, the overall system bandwidth is partitioned into a number of orthogonal subcarrier frequencies, commonly referred to as tones. A stream of informational bits is converted to a series of frequency-domain symbols, and these symbols are transmitted over the subcarrier frequencies. Each subcarrier is modulated with a modulation scheme, such as quadrature amplitude modulation, phase-shift keying, etc. OFDM is used in the IEEE 802.11 wireless local area networking standards.
OFDM systems, like other wireless systems, are susceptible to the effects of residual carrier offsets, phase noise, and phase and quadrature imbalance. These impairments may cause interference between the separate symbols, referred to as inter-symbol interference (ISI), which can degrade system performance.
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