US 5,930,231 A · Block spectrum receiver for a broadband communications system

Abstract

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.

Claims8

Dependent claims

A system for coupling telephony signals modulated on a carrier in a predetermined spectral subband of a broadband communication network from a subscriber to a telephony network interface, comprising:

a tuner for tuning to and selecting the predetermined spectral subband;
a block channelizer for collecting a group of telephony signals from said tuner and providing time division multiple access (TDMA) sampled signals corresponding to the modulated telephony signals at baseband;
a baseband demodulator for demodulating the TDMA sampled signals and deriving demodulated telephony signals;
and
an output interface for coupling said demodulated telephony signals to a telephony network,
wherein the baseband demodulator comprises:
an input port for receiving a serial data stream comprising a plurality of digital signal samples representing a plurality of QPSK-modulated DS0 telephony channels at baseband;
an automatic gain control (AGC) stage for adjusting the gain of the digital signal samples for each of the DSO telephony channels;
a symbol timing recovery (STR) stage coupled to the AGC stage for extracting timing information for each of the QPSK-modulated DSO telephony channels from the digital signal samples and delaying the sampling of the digital signal samples at a decoding stage to a time such that the sampling will be at optimized symbol instants;
a carrier phase recovery (CPR) stage coupled to the STR stage for locking the demodulator to the frequency of the carrier for each of the QPSK-modulated DS0 telephony signals;
and
a symbol decoding stage for sampling the digital signal samples and providing a digital signal output corresponding to the demodulated DS0 telephony channels.

9 more elements

Dependencies are inferred from the claim text.

Block spectrum receiver for a broadband communications system

Life of this patent

Block spectrum receiver for a broadband communications system

Life of this patent

Abstract

Claims8