The communication 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 frequency bandwidth over the hybrid fiber/coax distribution network. The head end includes a head end multicarrier modem for modulating downstream telephony information on a plurality of orthogonal carriers in the first frequency bandwidth and demodulating 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 downstream control data and telephony. Also provided is a method and apparatus for performing a Fast Fourier Transform (FFT).

Communication system with multicarrier telephony transport

The communication system includes a hybride 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 frequency bandwidth over the hybrid fiber/coax distribution network. The head end includes 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 head end further includes a controller operatively connected to the head end 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 includes 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 modulating 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 downstream telephony information modulated on at least a band of a plurality of orthogonal 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 identifying 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.

Dynamic bandwidth allocation

A method and apparatus for pilot-symbol aided channel estimation in a wireless digital communication system which transmits packets of N OFDM data blocks, each data block comprising a set of K orthogonal carrier frequencies. At the transmitter, pilot symbols are inserted into each data packet at known positions so as to occupy predetermined positions in the time-frequency space. At the receiver, the received signal is subject to a two-dimensional inverse Fourier transform, two-dimensional filtering and a two-dimensional Fourier transform to recover the pilot symbols so as to estimate the channel response.

Pilot-aided channel estimation for OFDM in wireless systems

A radio system having a master station including a wideband receiver, an A/D converter and a digital signal processing module for each of a plurality of space diversity antennas, the digital signal processing module converting the digitized samples into the frequency domain, weighting and combining the frequency domain signals from each of the antennas and separating the signals into signals corresponding to those transmitted from the remote stations.

Block radio and adaptive arrays for wireless systems

A communication system for coupling telephony or other signals to a broadband network such as a CATV network The system transmits a multiplex of telephony signals in the forward band of the broadband network, with individual signals directed to an addressed subscriber Telephony signals returning from subscribers upstream to a headend unit (HIU) are modulated onto the reverse band of the broadband network in a frequency division multiple access (FDMA) arrangement The upstream modulated telephony signals are received at a telephony network interface at the HIU coupled to the broadband network A group of reverse band modulated telephony signals are received at a group receiver or channelizer The group receiver processes all upstream telephony signals within a selected spectral subband in the reverse band to apply a receiver matched filter with a weighted overlap and add circuit, and are then converted to baseband by an FFT circuit The group receiver provides a serial data stream representing the baseband telephony signals The baseband telephony signals are processed to derive demodulated telephony signals The demodulated telephony signals are coupled to the telephony network

Block spectrum receiver for a broadband communications system

A device for the reception of digital data broadcast at a high bit rate for reception by mobile receivers is disclosed. The device operates under adverse conditions of multiple propagation corresponding to the Rayleigh process and imperfect frequency tuning to minimize the inter-symbol interference in the frequency domain. The device receives a digital signal having digital elements distributed in the frequency-time space f-t and transmitted in the form of symbols each constituted by a multiplex of N orthogonal carrier frequencies modulated by a set of digital elements and broadcast simultaneously. The device includes a module for transposition by a local oscillator, baseband filtering and analog-digital conversion, a temporal windowing module for the selection of the useful samples and a mathematical transformation module, the temporal windowing module applying a Nyquist window type of temporal window with non-zero roll-off.

Device for the reception of digital data time frequency interlacing, notably for radio broadcasting at high bit rate towards mobile receivers with nyquist temporal window

Roselyne Halbert-Lasselle

Papers

Device for the reception of digital data time frequency interlacing, notably for radio broadcasting at high bit rate towards mobile receivers with nyquist temporal window