Abstract: A cable mode includes a processor configured to receive fractional OFDM offset frequency spacing parameter and locations of CWT tone signals relative to locations of scattered pilot signals across an OFDM channel. The processor inserts pairs of CWT tone signals relative to the locations of the scattered pilot signals. The CWT tone signals are offset from each of the scattered pilot signals by a positive offset frequency and a negative offset frequency based on the fractional OFDM offset frequency spacing parameters. The CWT tone signals are transmitted in an upstream full duplex (FDX) subband. The CWT tone signals are processed to determine an average value of a Receive Modulation Error Ratio (RxMER) over a period of time in order to determine assigns of cable modems to interference groups.

Abstract: Disclosed is a system and method that allows a plurality of modems to transfer data simultaneously within a single frequency channel of a cable. Each modem is assigned a frequency band within the frequency channel. A receiving unit captures a block of data from the frequency channel, processes the data and separates data for each frequency band. Data for each frequency band is demodulated to recover encoded data. The receiving unit may process a plurality of channels. Simultaneous transfer of data by a plurality of modems within a single channel may be employed to carry a plurality of simultaneous lower-speed data streams such as voice conversations. The frequency of a band employed for voice information transfer may be reassigned if the band is scheduled for other transmission or exhibits an error rate greater than or equal to a predetermined value.

Abstract: Disclosed is a system for allowing on-demand delivery of data, such as MPEG-2 compressed video data, to a subscriber from a content server. The system utilizes a managed IP network that is coupled to the one or more content servers that allows the content servers to deliver data such as video, audio, and textual data with a guaranteed quality of service that is at least as good as broadcast quality service. The managed IP network is connected to a head end or other local cable service provider where video is delivered locally to subscribers. The IP transport data is translated to MPEG transport data, multiplexed onto an MPEG transport system, digitally modulated onto an rf carrier and up-converted to a specific frequency channel. The signal is then applied to the cable for delivery to the subscriber. Upstream signaling occurs through a set top box or computer that is connected to the cable and subsequently to a digital modulator/demodulator and ISP to a managed IP network 66.

Abstract: Disclosed is a quantizer that uses optimum decision thresholds that are determined by the average of the optimum reconstruction levels of a detected signal in the presence of noise. The Lloyd-Max Quantizer is used to determine the optimum reconstruction levels yK using a minimum means squared error technique. Decision thresholds xK are therefore established at levels where influences of noise or other distortions are equally likely to occur between adjacent transmitted points. The present invention can be utilized in quadrature amplitude modulation (QAM) systems or any quantizer design that quantizes an analog signal.

Abstract: A system and method for demodulation of an RF signal on a transmission channel is provided. The RF signal is demodulated to baseband as an in-phase (I) data signal and a quadrature (Q) data signal. A first block of I data is captured and a first block of Q data is captured. A time domain guard interval is provided in the captured first blocks of I and Q data. A complex discrete Fourier transform is performed on the captured first I and Q data blocks. An inverse frequency response for the transmission channel is determined. The inverse frequency response is multiplied by the complex discrete Fourier transform of the guard-interval protected first I and Q data blocks to generate a frequency domain product signal. An inverse Fourier transform on the product of the multiplying step is performed to generate a first equalized time domain signal. In a preferred embodiment, the method also includes using an overlapped Fourier transform and discarding a first portion of each equalized time domain signal.