Abstract: A method and a receiver system for subcarrier-specific frequency offset correction including frequency offset estimation, updating and compensation. The method includes initial frequency offset estimation in time domain using packet preamble, frequency offset compensation during channel estimation symbols using the initial frequency offset estimate, and frequency offset update tracking during header and data part both being performed in the frequency domain. The initial frequency offset estimation includes using a sum over a number of time lagged autocorrelation results, corresponding to a number of the last consecutive symbols of the preamble part of the packet with the autocorrelations being the result of a sum over a window of cross-correlations between the incoming signal and the respective packet synchronization sequence.

Abstract: A receiver including a channel estimation function in which an initial channel estimate is filtered to increase receiver operation, particularly when the receiver may only have a limited number of channel estimation symbols with which to form the channel estimate. In some embodiments the filtering is performed by transforming the initial channel estimate to the time domain, zeroing some of the samples to filter the time domain channel estimate, and transforming the filtered time domain channel estimate to the frequency domain for use in channel compensation.

Abstract: Systems and methods for packet detection for frequency hopping networks. Multiple receiver chains are set to different frequencies to check for packets at the different frequencies, at least until receipt of a preamble sequence in a packet is received. After detection of a packet at least some of the receiver chains are used to process received signals according to a frequency hopping pattern.

Abstract: Pairs of parallel Viterbi decoders use windowed block data for decoding data at rates above 320 Mbps. Memory banks of the deinterleavers feeding the decoders operate such that some are receiving data while others are sending data to the decoders. Parallel input streams to every pair of decoders overlap for several traceback lengths of the decoder causing data input to a first decoder at the end of an input stream to be the same as the data input to a second decoder of the same pair at the beginning of an input stream. Then, the first decoder is able to post-synchronize its path metric with the second decoder and the second decoder is able to pre-synchronize its path metric with the first. Either, the deinterleaver data length is an integer multiple of the traceback length or the data input to only the first block of the first interleaver is padded.

Abstract: Frame synchronization methods and systems suited for packet communications systems, and particularly time frequency hopping packet communication systems, are disclosed. Frame synchronization is performed by performing a first correlation on information of received symbols and performing a second correlation on results of the first correlation. In systems with repeating synchronization information modulated by a cover sequence, the results of the second correlation may be used to determine symbol numbering of symbols in a packet.

Abstract: Transmission systems and methods for reducing interference by wideband communication systems with narrowband communications systems are disclosed. In some embodiments an ultrawideband system employing orthogonal frequency division multiplexing (OFDM) with a null post-fix nulls symbols for sub-carriers at potentially interfering frequencies prior to transformation to the time domain and filters a time domain representation using a notch filter to further reduce spectral components at the potentially interfering frequencies. In further embodiments pre-emphasis is applied to a frequency domain representation of symbols to reduce ripples introduced by the notch filter.

Abstract: A method and system for estimating DC offset and removing the excess DC offset from samples used by an overlap-and-add operation at the receiver of OFDM symbols in UWB communication. The DC offset for each sample within the overlap-and-add interval may be estimated using a sliding window, of the size required for an FFT, operation over past samples. The DC offset may be estimated for a sample within the overlap-and-add interval and updated for the succeeding samples. A size of the overlap-and-add interval may be fixed or may be allowed to vary according to switching characteristics of an analog RF stage preceding the overlap-and-add operation.

Abstract: Methods and systems for packet preamble sequences are provided. The preamble sequences are produce by multiplying preestablished base sequences by cover sequences. The cover sequences are chosen for high-performance in multi-band OFDM systems with modes that include two-band hopping.

Abstract: A method and system for detecting the presence of narrowband transmitters utilizing frequencies also utilized by wider band communication systems. In some embodiments an ultrawideband transceiver detects signals at specific frequencies within a spectrum of frequencies, and analyzes the signals to determine if the signals indicate transmissions by a narrowband transmitter in a narrowband communication system. In further embodiments transmission circuitry reduces signal components at frequencies occupied by the narrowband transmitters.

Abstract: Transmission systems and methods for reducing interference by wideband communication systems with narrowband communications systems are disclosed. In some embodiments an ultrawideband system employing orthogonal frequency division multiplexing (OFDM) with a null post-fix nulls symbols for sub-carriers at potentially interfering frequencies prior to transformation to the time domain and filters a time domain representation using a notch filter to further reduce spectral components at the potentially interfering frequencies. In further embodiments pre-emphasis is applied to a frequency domain representation of symbols to reduce ripples introduced by the notch filter.

Abstract: A receiver including a channel estimation function in which an initial channel estimate is filtered to increase receiver operation, particularly when the receiver may only have a limited number of channel estimation symbols with which to form the channel estimate. In some embodiments the filtering is performed by transforming the initial channel estimate to the time domain, zeroing some of the samples to filter the time domain channel estimate, and transforming the filtered time domain channel estimate to the frequency domain for use in channel compensation.