British Broadcasting Corporation

Peter Neil Moss

Jonathan Highton Stott

Oliver Paul Haffenden

Adam Wiewiorka

Christopher Ryan Nokes

Methods and apparatus for processing an OFDM MIMO signal in a system having at least two transmitters arranged to transmit an output signal pair that includes operating a series of transformations on a pair of input signals so that each stream of the output signal pair contains decodable information from both streams of the input signal pair.

Transmission techniques

A method of operating a wireless network operating on a single frequency across a geographical area involves dividing the network into regions and arranging that the transmission of signals in subsets of adjacent regions on the same frequency is such that a receiver does not receive signals from more regions than can be separated using demapping techniques. The transmission method evolves a pattern of time slots such that the number of adjacent regions of a subset of regions transmitting simultaneously on a single frequency is less than the number of signals that each receiver is capable of demapping. The demapping arrangements may include MIMO techniques, constellation schemes, QAM.

Broadcast network

An on-channel repeater has a receiving antenna for receiving an RF signal and a transmitting antenna for transmitting on the same frequency as the input signal. An amplification path between the antennas provides substantially linear processing and includes a combiner, a decorrelating delay and a power amplifier. A filter estimator receives a reference signal and the combiner output and generates a plurality of control coefficients which are applied to an adaptive filter which filters the reference signal accordingly and applies its output to the combiner. The reference signal is derived not from the output of the decorrelating delay but rather from the output antenna after the power amplifier. Where there is an adjacent transmitter generating potentially interfering signals, the transmitter output is coupled to the same transmitter antenna.

On-channel repeater

A diversity receiver for receiving digital signals has a soft-decision decoder in each of its receiving sections, to provide confidence values for the received decoded digital values, and combines the values from the receiving sections in dependence upon the confidence values. The receiver is especially suitable for use with COFDM, and has two sections, the outputs of which are applied to a soft-decision combiner which combines the signals in dependence upon confidence values received from the demodulators. The output is then applied to a Viterbi decoder. The combining can simply involve switching but preferably involves averaging. Synchronisation and squelching can be provided. The system can be used with frequency diversity, spatial or polarisation diversity, or with antenna pattern diversity, in which case it can constitute an automatic rotator. The system automatically switches between different types of diversity reception, e.g. frequency and spatial diversity, in dependence upon the received signal quality.

Diversity reception method and diversity receivers

A digital audio broadcasting (DAB) receiver designed for receiving a signal with 1536 active carriers generated by an inverse fast Fourier transform (FFT) with 2048 points, includes the usual RF stage ( ), an IF filter ( ), and a demodulator ( ) providing baseband I and Q signals. This is followed by an anti-aliasing filter ( ), a sampler ( ), and an FFT ( ). The FFT is a 4096-point FFT, and is thus twice as long as required, and gathers twice as many points during each symbol period. However this is found to substantially simplify the construction of the IF filter ( ) and, more particularly, the anti-aliasing filter ( ). For use with real signals rather than quadrature demodulated signals, an 8192-point FFT is employed.

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Peter Neil Moss