Abstract:
Method for digitally compensating a phase response of an optical channel The invention relates to a method (100) for digitally compensating the phase response of an optical channel in frequency domain by using filter bank structure. The method (100) comprises: partitioning (101) a time-domain digital signal representing an optical signal transmitted over the optical channel in to overlapping sub-sequences; decomposing and filtering (103) the overlapping sub-sequences in the polyphase network obtaining polyphase filtered sub-sequences; transforming (105) the polyphase filtered subsequences into frequency domain by using a Fast Fourier Transform obtaining frequency sub-band signals; equalizing (107) the frequency sub-band signals by using a sub-band equalizer obtaining equalized frequency sub-band signals; transforming (109) the equalized frequency sub-band signals back into time domain by using an inverse Fast Fourier Transform obtaining equalized sub-sequences; filtering (111) the equalized sub-sequences in the polyphase network obtaining equalized polyphase filtered sub-sequences; and reconstructing (113) the sub-sequences compensated by the inverse of the phase response of the optical channel by applying a block overlap procedure to the equalized sub-sequences.
Abstract:
A receiving apparatus and method for performing carrier detection in a frequency domain for a digital wavelet multi-carrier transmission. A wavelet transform of received data is performed to output complex data and then the complex data is delayed for one sampling period. Subsequently, the delayed complex data and delayed complex data are divided. A number of the divided complex data present within each of plural quadrants on orthogonal coordinates is calculated and a maximum number of data present within one of the quadrants is selected and compared with a threshold in order to decide whether the received data is intended data.
Abstract:
The comminication system includes a hybrid fiber/coax distribution network. A head end provides for downstream transmission of telephony and control data in a first frequency bandwidth over the hybrid fiber/coax distribution network and reception of upstream telephony and control data in a second frequeny bandwidth over the hybrid fiber/coax distribution network. The head end includes a head end multicarrier modem for modulating at least downstream telephony information on a plurality of orthogonal carriers in the first frequency bandwodth and demodulating at least upstream telephony information modulated on a plurality of orthogonal carriers in the second frequency bandwidth. The head end further includes a controller operatively connected to the head en multicarrier modem for controlling transmission of the downstream telephony information and downstream control data and for controlling receipt of the upstream control data and upstream telephony information. The system further includs service units, each service unit operatively connected to the hybrid fiber/coax distribution network for upstream transmission of telephony and control data in the second frequency bandwidth and for receipt of the downstream control data and telephony in the first frequency bandwidth. Each service unit includes a service unit multicarrier modem for modulation at least the upstream telephony information on at least one carrier orthogonal at the head end terminal to another carrier in the second frequency bandwidth and for demodulating at least the downstream telephony information modulated on at least a band of a plurality of orthonogal carriers in the first frequency bandwidth. Each service unit also includes a controller operatively connected to the service unit multicarrier modem for controlling the modulation of and demodulation performed by the service unit multicarrier modem. A method of monitoring communication channels, a distributed loop method for adjusting transmission characteristics to allow for transmission of data in a multi-point to point communication system, a polyphase filter technique for providing ingress protection and a scanning method for indetifying frequency bands to be used for transmission by service units are also included. Also provided is a method and apparatus for performing a Fast Fourier Transform (FFT). In one embodiment, a scalable FFT system is built using a novel dual-radix butterfly core.
Abstract:
A method for monitoring at least one telephony communication n-bit channel, wherein one of the bits is a parity bit, includes sampling the parity bit of the n-bit channel. A probable bit error rate is derived from the sampling of the parity bit. The probable bit error rate can be compared to a pre-determined bit error rate value to determine if the at least one telephony communication n-bit channel is corrupted. If the at least one telephony communication n-bit channel is corrupted, the at least one telephony communication n-bit channel is re-allocated to an uncorrupted and unallocated telephony communication n-bit channel. Further, at least one unallocated telephony communication channel can be periodically monitored and error data accumulated to indicate the quality thereof.
Abstract:
A physically compact, multichannel wireless communication transceiver architecture employs overlap and add or polyphase signal processing functionality, previously applied to narrowband speech analysis research, for wideband signal processing. A receiver section receives a plurality of multiple frequency communication channels and outputs digital signals representative of the contents of the plurality of multiple frequency communication channels. The receiver section contains an FFT-based channelizer that processes the digital signals output by a wideband digital receiver and couples respective channel outputs to a first plurality of digital signal processor units, which process (e.g. demodulate) respective ones of the digital channel signals and supply processed ones of the digital channel signals at respective output ports for distribution to an attendant voice/data network. On the transmit side, a transmit section contains a plurality of digital signal processors, respectively associated with respective ones of a plurality of incoming (voice/data) communication signals to be transmitted over respectively different frequency channels. Their processed (modulated, encoded) outputs are supplied to an inverse FFT combiner. The FFT combiner supplies a combined multichannel signal to a wideband transmitter which transmits a multiple frequency communication channel signal. Each of the channelizer and combiner may be implemented using overlap and add or polyphase filtering.
Abstract:
System and method embodiments are provided for a receiver for circularly convolved signals. In an embodiment, a universal decoder for a circularly convolved signal includes a first decoder configured to decode the circularly convolved signal; a second decoder configured to decode a plurality of symbol lengths signal from a first portion of the circularly convolved signal, wherein the plurality of symbol lengths signal is time aligned with the circularly convolved signal before passing through the second decoder; and an adder component configured to sum a first decoder output coming from the first decoder and a second decoder output coming from the second decoder to produce a symbol value from which a log likelihood ratio (LLR) output is obtained.
Abstract:
L'invention concerne un récepteur multi-porteuse à banc de filtres (FBMC) mettant en œuvre une synchronisation dans le domaine fréquentiel. Le récepteur comprend un module de synchronisation (620) comportant un estimateur d'erreur sur les instants d'échantillonnage (621) et, pour chaque sous-porteuse, un filtre interpolateur (622) pour reconstruire les échantillons aux instants exacts d'échantillonnage. Un déphaseur (626) est prévu, pour chaque sous-porteuse, en sortie du filtre interpolateur, pour effectuer une compensation de phase. Le déphaseur (626) peut être suivi d'un égaliseur (627) dans le domaine fréquentiel.
Abstract:
L'invention concerne un dispositif de démodulation d'un signal multiporteuse suréchantillonné. Selon l'invention, un tel dispositif comprend Δ étages, Δ étant un entier supérieur ou égal à 1, alimentés par des données reçues représentatives de données source, chacun desdits étages comprenant un banc de filtres d'analyse présentant N 0 branches et un facteur de décimation égal à M 0 , avec N 0 et M 0 premiers entre eux et M 0 > 1, un banc de filtres d'analyse comprenant une matrice de décomposition V (i) (z) et une matrice de Fourier F N0 . La matrice de décomposition est une matrice para-unitaire, dont certains coefficients sont forcés à zéro selon un critère prédéterminé tenant compte dudit facteur de décimation M 0 et du nombre de branches N 0 , de façon à permettre une reconstruction parfaite desdites données source.
Abstract:
The invention concerns a method for transmitting a biorthogonal multicarrier signal BFDM/OM, using a transmultiplexer structure providing: a modulating step, using a synthesis filter bank (11), having two 2M parallel branches, M >/= 2, each supplied by source data, and comprising an expander of order M and filtering means; a demodulating step, using an analysis filter bank (12), having two 2M parallel branches, each comprising a decimation unit of order M and filtering means, and delivering received data representing said source data; said filtering means being derived from a predetermined prototype modulating function.
Abstract:
The comminication system includes a hybrid fiber/coax distribution network. A head end provides for downstream transmission of telephony and control data in a first frequency bandwidth over the hybrid fiber/coax distribution network and reception of upstream telephony and control data in a second frequeny bandwidth over the hybrid fiber/coax distribution network. The head end includes a head end multicarrier modem for modulating at least downstream telephony information on a plurality of orthogonal carriers in the first frequency bandwidth and demodulating at least upstream telephony information modulated on a plurality of orthogonal carriers in the second frequency bandwidth. The system includes service units operatively connected to the hybrid fiber/coax distribution network for upstream transmission of telephony and control data and for receipt of the downstram control data and telephony. Also provided is a method and apparatus for performing a Fast Fourier Transform (FFT).