The wireless transmission of an information signal may include formatting the information signal in a transmitter, modulating the formatted information signal over a baseband carrier, receiving the modulated signal at a receiving device, and demodulating the modulated signal. After demodulation, the received signal may be processed further by the receiving device. Orthogonal frequency division multiplexing (OFDM) is a method of encoding digital data on multiple carrier frequencies for high data rate, high performance wireless communication systems. In an OFDM system, bandwidth is divided into closely spaced orthogonal subcarriers (i.e., tones), which are modulated with data symbols. The transmitted data is divided into parallel data streams, one for each subcarrier. A primary advantage of OFDM over single-carrier schemes is OFDM's ability to operate under unfavorable channel conditions (e.g., attenuation of high frequencies in a long copper wire, narrowband interference, and frequency-selective fading, among others) without complex equalization filters. These advantages simplify equalizer design and have resulted in adoption of OFDM in several standards (e.g., IEEE 802.11a/g/n, IEEE 802.16e, and 3G-LTE). Although data is not typically transmitted on a DC subcarrier in OFDM systems, injection of a DC component may occur at the transmitter and the receiver. The injection of the DC component may limit performance of the communication system.
USPTO Backgrounds
USPTO Backgrounds