Abstract: An orthogonal frequency division multiplexing (OFDM) transmitter maps a digital level into I and Q components. The transmitter uses every other digital level as an I or Q component or divides the MSBs and LSBs of a digital level into the I and Q components. An analog OFDM transmitter uses a pair of input analog levels as the I and Q components. An inverse FFT outputs a complex value and OFDM symbols are transmitted. An inverse FFT may also output a real value using complex conjugates. An optional encoder encodes digital or analog samples into L levels using N orthogonal codes before input into the OFDM transmitter. OFDM receivers receive the OFDM signal and output digital or analog samples. Video signals are input into a distributor that distributes analog or digital samples into vectors, each vector input into an OFDM transmitter that transmits to a corresponding receiver.

Abstract: A quadrature amplitude modulation (QAM) transmitter separates an input digital level into I and Q components. In a variation, a QAM transmitter uses every other input digital level as an I or Q component. A QAM receiver receives a QAM modulated signal and outputs digital levels. A QAM transmitter for transmitting analog levels uses a pair of input analog levels as the I and Q components. A QAM receiver receives a QAM modulated signal and outputs analog levels. The digital and analog input levels are produced by encoding N samples using L orthogonal codes.