Patent application number | Description | Published |
20100246726 | RECEIVER AND METHOD OF RECEIVING - A receiver recovers data from Orthogonal Frequency Division Multiplexed (OFDM) symbols, the OFDM symbols including sub-carrier symbols carrying data symbols and sub-carrier signals carrying pilot symbols. The receiver includes a Fourier transform processor arranged in operation to receive a time domain digital version of the OFDM symbols and to form a frequency domain version of the OFDM symbols, from which the pilot symbol sub-carriers and the data symbol bearing sub-carriers can be recovered, and a detector arranged in operation to recover the data symbols from the data bearing sub-carriers of the OFDM symbols. The receiver includes a noise estimator arranged in operation to generate a long term estimate of noise power in the frequency domain version of the OFDM symbols at a plurality of frequencies, by accumulating an average noise power at the plurality of frequencies from a plurality of the OFDM symbols, and for generating an estimate of a current level of the noise power in the frequency domain version of a current one of the OFDM symbols at the plurality of frequencies. An impulsive noise detector detects the presence of an impulse of noise in the current OFDM symbol, by comparing the noise power in the current OFDM symbol with the long term noise power at the plurality of frequencies, and to generate an impulse noise flag to indicate that the current OFDM symbol is affected by an impulse of noise if the comparison indicates the presence of an impulse of noise. Impulsive noise in the time domain will generate an increase in noise level across the frequency bandwidth of the OFDM symbols. If all frequencies experience an increase then an impulse of noise can be detected. Thereafter the detector can conceal the effect of the impulse noise on the recovering of the data symbols from the data bearing sub-carriers, for example by adapting channel state information for use in de-mapping modulated symbols into data symbols. | 09-30-2010 |
20100309384 | DATA PROCESSING APPARATUS AND METHOD - A receiver for detecting and recovering data from Orthogonal Frequency Division Multiplexed (OFDM) symbols. The OFDM symbols include within a repeating time frame a signalling OFDM symbol and one or more data bearing OFDM symbols, the signalling OFDM symbol including a pre-amble guard interval and a post-amble guard interval, the pre-amble and the post-amble guard intervals being formed by copying samples from a useful part of the signalling OFDM symbol in the time domain. The receiver includes a signalling and guard detector, which includes a correlator comprising a first branch which includes a first moving averaging filter, which is arranged to form pre-amble average correlated samples by averaging a value of a plurality of pre-amble correlated samples within a moving window, the plurality of samples averaged within the moving window corresponding to a temporal length of the post-amble (Tb), a second branch which includes a second moving averaging filter, which is arranged to form post-amble average correlated samples by averaging a value of a plurality of post-amble correlated samples within a moving window, the plurality of samples averaged within the moving window corresponding to a temporal length of the pre-amble (Tc), a combiner, which is arranged to combine the averaged pre-amble correlated samples and the averaged post-amble correlated samples to form output correlation samples. A post processing detector can detect the signalling OFDM symbol and moreover a synchronisation point derived from a centre of the signalling OFDM symbol with improved accuracy. The receiver finds application, for example, with DVB-T2 in detecting the P | 12-09-2010 |
20100310022 | DATA PROCESSING APPARATUS AND METHOD - A receiver detects and recovers data from Orthogonal Frequency Division Multiplexed (OFDM) symbols, the OFDM symbols including a plurality of sub-carrier symbols formed in the frequency domain and transformed into the time domain for transmission, the time domain OFDM symbols including a guard interval. The guard interval of the OFDM symbols is one of a plurality of predetermined temporal lengths and the guard interval is formed by repeating time domain samples of the OFDM symbol from useful samples of the OFDM symbols for a period corresponding to the guard interval from the OFDM symbols. The receiver includes a correlator operable to correlate the time domain samples at a separation determined in accordance with the useful samples of the OFDM symbols and for each of a plurality of possible guard intervals combining the correlated samples for a period equal to the guard interval, for a plurality of consecutively received OFDM symbols, to form for each of the possible guard intervals a correlation output value, and a guard interval identifier arranged to receive the output from the correlator and to identify one of the guard intervals used for the received OFDM symbols from the correlation output value for each of the plurality of possible guard intervals. Accordingly in a system such as DVB-T2, where the guard interval is provided in signalling data communicated with the OFDM symbols, the guard interval can be detected without or before the signalling data is detected, thereby reducing a time for detecting the data conveyed by the OFDM symbols or the guard interval and/or improving an integrity with which the guard interval and therefore the data can be detected. | 12-09-2010 |
20130038739 | SIGNAL EVALUATION SYSTEM AND METHOD - A digital television receiver includes smart antenna signaling that sends, to a smart antenna configuration, data specifying reception directions available to the smart antenna. The receiver includes an event monitor that detects a predetermined event, and a smart antenna configuration estimator that, in response to the detected event and for each of a current reception direction and available reception directions adjacent on either side of the current reception direction, to obtain an estimate and the maximum value of a channel impulse response from the receiver, to calculate an average value of the channel impulse response, including channel impulse response values for additional signal paths. The estimator calculates a respective quality value as the ratio of the maximum value to the average value of the channel impulse response. The receiver also includes a selector that selects a direction corresponding to the largest respective quality value as a new reception direction. | 02-14-2013 |
20130182124 | SIGNAL EVALUATION SYSTEM AND METHOD - A smart antenna configuration estimator for use in a digital TV receiver comprises data input means operable to obtain an estimate of an impulse response of a channel through which the television signal has passed to the receiver, maximum finding means operable to find the maximum value of the channel impulse response, the maximum value corresponding to a main signal path, averaging means operable to calculate a mean of values of the channel impulse response comprising channel impulse response values corresponding to one or more additional signal paths, and ratio calculating means operable to calculate a quality value as the ratio of the maximum value to the mean of values of the channel impulse response. | 07-18-2013 |
20140269981 | TRANSMITTERS, RECEIVERS AND METHODS OF TRANSMITTING AND RECEIVING - A receiver comprises a demodulator configured to detect a signal representing the OFDM symbols and to generate a sampled digital version of the OFDM symbols in the time domain. A Fourier transform processor is configured to receive the time domain digital version of the OFDM symbols and to form a frequency domain version of the OFDM symbols, from which the pilot symbol bearing sub-carriers and the data symbol bearing sub-carriers can be recovered. A detector is configured to recover the data symbols from the data bearing sub-carriers of the OFDM symbols and to recover the pilot symbols from the pilot bearing sub-carriers of the OFDM symbols in accordance with the scattered pilot symbol pattern and the continuous pilot symbol pattern. The scattered pilot symbol pattern is one of a plurality of scattered pilot symbol patterns and the continuous pilot pattern is independent of the scattered pilot symbol pattern. | 09-18-2014 |
20140269982 | TRANSMITTERS, RECEIVERS AND METHODS OF TRANSMITTING AND RECEIVING - The receiver comprises a demodulator configured to detect a signal representing the OFDM symbols and to generate a sampled digital version of the OFDM symbols in the time domain. A Fourier transform processor is configured to receive the time domain digital version of the OFDM symbols and to form a frequency domain version of the OFDM symbols, from which the pilot symbol bearing sub-carriers and the data symbol bearing sub-carriers can be recovered. A detector is configured to recover the data symbols from the data bearing sub-carriers of the OFDM symbols and to recover the pilot symbols from the pilot bearing sub-carriers of the OFDM symbols in accordance with the continuous pilot symbol pattern. The continuous pilot symbols are present at the same sub-carrier locations in first OFDM symbols and as second OFDM symbols. A transmitter is also provided. | 09-18-2014 |
20140294124 | TRANSMITTER AND METHOD OF TRANSMITTING AND RECEIVER AND METHOD OF DETECTING OFDM SIGNALS - A transmitter transmits payload data using Orthogonal Frequency Division Multiplexed (OFDM) symbols. The first OFDM symbol is a first type having a number of sub-carriers which is less than or equal to the number of sub-carriers of the one or more second OFDM symbols of a second type and a guard interval for the first OFDM symbol is selected in dependence upon the longest possible guard interval of the second OFDM symbol. Accordingly an OFDM communications system can be formed in which data is transmitted using a frame structure in which a guard interval is adapted to allow a mix of different types of OFDM symbols. | 10-02-2014 |