Cisco Technology, Inc.

Gte Laboratories Incorporated

Verizon Laboratories Inc.

Hung-San Chen

Charles J Naegeli

Alejandro Schwartzman

Harry Edward Mussman

Xiong Yang

Mark E Millet

Stephen S Liu

Wei-Sing Chen

Stephen P Hartman

Apparatus, methods, and computer program products for utilizing a frequency channel determined to be unacceptably noisy by finding a cleaner, narrower bandwidth within the frequency channel. Initially data is received on a frequency channel at a CMTS, specifically an upstream receiver, and by a narrow bandwidth detector, connected to a processor also used by components in the CMTS. The narrow bandwidth detector performs a Fast Fourier Transform (FFT) on the frequency channel thereby creating multiple FFT points within the frequency channel. A clean bandwidth for transmitting data within the frequency channel is identified where the clean bandwidth is derived from a subset of FFT points from the full set of FFT points. The subset of FFT points are contiguous points that have a noise level below a predetermined noise threshold.

Method and apparatus for locating a cleaner bandwidth in a frequency channel for data transmission

Transitions among different upstream frequency channels in a cable television plant in order to transmit data occur while considering the noise level of the upstream frequency channel presently being used to transmit data. By taking into account the noise level of the presently used upstream frequency channel, the CMTS in a cable plant can make a more intelligent decision as to whether it is worthwhile changing the upstream frequency channel for a group of cable modems. A spectrum analyzer determines the noise level of a presently used frequency channel. A bit error rate for the present frequency channel is detected. The spectrum analyzer then determines whether the bit error rate exceeds a threshold value. Is so, it is then determined whether the noise level of the present frequency channel is greater than or less than the noise level of another frequency channel having the lowest noise level plus a buffer noise value. If the present noise level is greater, a transition is made to the other frequency channel with the lower noise level. If not, the cable plant continues using the present frequency channel. The noise level of the presently used frequency channel is measured at the CMTS upon receipt of an empty data packet arriving at a known timing mark.

Method and apparatus for upstream frequency channel transition

A network (,) includes a broadband customer service module (B-CSM) (,). The B-CSM (,) includes a plurality of feeder interface cards (FICs) (,) and optical line cards (OLCs) (,) which are coupled together through a midplane assembly (,) so that each FIC (,) couples to all OLCs (,) and each OLC (,) couples to all FICs (,) through junctor groups (,). A reference clock which oscillates at a frequency slower than the data rate is routed with payload data so that it receives delays similar to those imposed on the payload data due to processing. At second stage switching fabrics (,) where data need to be extracted from signals flowing within the B-CSM (,), a clock regeneration circuit (,) generates a master clock signal oscillating at twice the data rate and phase synchronized to a delayed reference clock. A geometric compensation scheme corrects for timing skew which occurs when clocks and data are distributed to points or small areas from widely dispersed locations, and when clocks and data are distributed from points or small areas to widely dispersed locations. The B-CSM (,) ranks the junctor groups (,) according to signal occupancy and manages signal traffic to efficiently utilize the FICs (,) and to reduce the probability of signal blocking. The junctor groups (,) can include a number of bidirectional junctors. The bidirectional junctors are configured to carry upstream or downstream signals according to current upstream and downstream signal traffic volume.

Broadband switch that manages traffic and method therefor

A network (10) includes a broadband customer service module (B-CSM) (20). The B-CSM (20) includes a plurality of feeder interface cards (FICs) (36) and optical line cards (OLCS) (38) which are coupled together through a midplane assembly (34) so that each FIC (36) couples to all OLCs (38) and each OLC (38) couples to all FICs (36) through junctor groups (68). The B-CSM (20) interfaces many OC-12 SONET feeders to many OC-12 SONET lines. Within the B-CSM (20) circuit switching is performed electrically at an STS-1 rate. A reference clock which oscillates at a frequency lower than the data rate is routed with payload data so that it receives delays similar to those imposed on the payload data due to processing. At second stage switching fabrics (50) where data need to be extracted from signals flowing within the B-CSM (20), a clock regeneration circuit (32) generates a master clock signal oscillating at twice the data rate and phase synchronized to a delayed reference clock. A geometric compensation scheme corrects for timing skew which occurs when clocks and data are distributed to points or small areas from widely dispersed locations, and when clocks and data are distributed from points or small areas to widely dispersed locations.

Data transferring circuit which aligns clock and data

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San Jose, CA, United States of America

Hung-San Chen