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

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.

Channel selection for a hybrid fiber coax network

Systems and methods for orthogonal frequency division multiplexing are provided. In one embodiment, a multi-carrier modem comprises: a receiver configured to de-modulate symbols from at least one of a plurality of spectrally overlapping carrier signals to produce a receiver output; a transmitter configured to modulate symbols onto at least one of a plurality of the spectrally overlapping carrier signals; a processor coupled to the transmitter, wherein the processor outputs data for transmission by the transmitter, wherein the processor applies an inverse Fourier transform to the data transmitted by the transmitter; the processor coupled to the receiver, wherein the processor applies a Fourier transform to the receiver output; and a controller programmed to instruct the transmitter to transmit at least one symbol representing a request for bandwidth allocation on a first carrier; wherein the controller is further programmed to determine when a collision has occurred on the first carrier.

Systems and method for orthogonal frequency divisional multiplexing

A apparatus for providing a Fast Fourier Transform (FFT) and an inverse FFT is provided. The apparatus comprises a radix-N core. The radix-N core includes at least N multipliers. The radix-N core also includes a twiddle-factor lookup table that stores complex twiddle-factors. The twiddle-factor lookup table is coupled to one input of each of the multipliers. The radix-N core also includes a conversion random access memory (RAM) that stores transform points. The conversion RAM is coupled to another input of each of the multipliers. The radix-N core also includes an array of at least N-times-N adder-subtracter-accumulators.

Fast fourier transform apparatus and method

A head end controller is described. The head end controller controls a plurality of service units in a telecommunications system with a multi-carrier transmission scheme. The head end controller includes a logic circuit that generates control messages for the plurality of service units. Each service unit is assigned to at least one subband of a transmission bandwidth. The head end controller further includes a transceiver that is coupled to a distribution network of the transmission system, wherein the transceiver broadcasts control messages to the plurality of service units. The plurality of service units are configured to use a multiple access scheme to transmit on a radio frequency carrier using orthogonal frequency division multiplexing (OFDM) so that transmissions from the plurality of service unit are received from the distribution network at the transceiver synchronized within an OFDM waveform.

Systems for synchronous multipoint-to-point orthogonal frequency division multiplexing communication

The authors present the architecture of a fast Fourier transform processor which has high performance characteristics and an embedded test structure that allows the processor to test itself during normal operation. The properties of separable residue codes have been used for error detection in the arithmetic unit of the processor. Offline error detection which tests for the classic stuck at faults is based on the properties of the dynamic CMOS logic design used. The testing circuitry used in the architecture accounts for only a 20% area overhead and no time ahead, an important saving in a signal-processing environment. >

M.A. Boyoumi

Papers

A testable CMOS signal processor for fast Fourier transforms