Abstract: A method and apparatus for classifying the state of a system are described. The state of the system can be in one of a plurality of different classes and the system can have at least one property represented by a set of data items. A current data item representing a property of the system is received. The system is classified as being in one of a plurality of different classes based on the probability that the system is in any one of the plurality of classes calculated using the current data item, a recursively calculated mean value for the set of data items representing the property of the system and at least one recursively calculated statistical parameter for the set of data items representing the property. It is determined whether to output a signal based on the class in which the system is classified.

Abstract: The present invention relates to a method and apparatus for decoding symbols each representing a digital word including a turbo encoded bit, a parity bit and at least one uncoded bit. A first soft metric generator produces a soft metric of the encoded bit in each symbol and one or more second soft metric generators generate a soft metric of the or each uncoded bit in each symbol. A turbo decoder decodes the soft metric of the encoder bit so as to produce a hard value and a soft estimate of the encoded bit. A turbo encoder encode the hard value of the encoded bit to produce a reconstruction of the encoded bit and two parity bits. A puncture module punctures the parity bits once. One or more hard decision modules produce a hard decision for the or each uncoded bit of each symbol.

Abstract: The present invention relates to a method and apparatus for encoding input words consisting of a plurality of information bits so as to produce encoded output symbols. The invention has particular application to the production of encoded output symbols which are to be subject to phase shift key (PSK) modulation. The invention is advantageously employed in generating phase shift key modulated signals for digital television signal transmission. A turbo encoder is used to receive and encode a first portion of each input word so as to generate corresponding encoded and parity bits from the input words. A puncturing module punctures the parity bits once for each encoded bit. A mapping circuit receives an uncoded second portion of each input word and forms an output symbol for each input word from the uncoded second portion and from the corresponding encoded and punctured parity bits.

Abstract: An apparatus for producing a product code having a first dimension systematic block code of length nx elements and a second dimension systematic block code of length ny elements has a first dimension encoder 12 for receiving a data element stream 11 to produce the first dimension block code having kx data elements and nx−kx parity elements, the parity elements being derived from the data elements. The first dimension encoder is arranged to produce ky first dimension code vectors where ky is the data element length of the second dimension systematic block code. The second dimension encoder 14-16 is representative of nx encoders. The second dimension encoder receives the first dimension code vectors as they are produced and derives (nxny-nxky) parity elements for the second dimension systematic block code.

Abstract: The present invention relates to the use of complex non-linear elements in improvements to the recovery of a carrier phase reference from a modulated input signal where the modulation is in accordance with the M-PSK modulation format and where M has a value greater than 4 and the signal-to-noise ratio in the channel is low. A voltage-controlled oscillator is employed to generate first and second oscillations in phase quadrature with respect to each other. The modulated input signal is mixed with the first of the oscillations to detect the (I) signal component and the modulated input signal is mixed with the second of the oscillations to detect the (Q) signal component. A control signal is derived from the (I) and (Q) signal components as an estimate of the phase difference between the input signal carrier and the voltage-controlled oscillator.