Abstract: A system for testing a cable network during normal operation interleaves test signals with live data traffic. Installed cable modems are used to generate the test signals. During live communication, such modems send upstream data at allotted time periods. Periodically, there are time slots when no modem is transmitting on the network. During these times, specific modems may be directed to transmit specific test signals. A controller such as a cable modem termination system directs specific modems to transmit signals at defined frequencies and powers during specific time slots. In this manner, the system can monitor the frequency response of the cable network at various locations, and thereby determine “on-the-fly” when maintenance or modification is required.

Abstract: Methods, apparatus, and computer-readable media are disclosed for performing diagnostic tests of a communication link between a headend and a cable modem without having to assign an IP address to the cable modem. The diagnostic tests are performed at the MAC layer and test the state of the hardware between and including the cable modem termination system (CMTS) and a selected cable modem. By doing so, a network operator is able to more easily focus in on a potential problem in cable RF/MAC connectivity between the two components by first eliminating (or identifying) a problem with hardware before focusing on problem-solving at the software level, typically at the Network layer, at which point the cable modem is assigned an IP address.

Abstract: Methods, apparatus, and computer-readable media are disclosed for creating a virtual lookahead upstream receiver in a single physical upstream receiver in a CMTS, thereby avoiding having to dedicate an upstream receiver strictly for lookahead capability. A lookahead receiver is used to determine whether a potential alternative frequency is better than the frequency presently being used. A physical upstream receiver is assigned to operate under a set of operational parameters associated with a logical lookahead receiver during a particular time slot. The logical receiver receives upstream data from a selected test modem using an alternative upstream frequency. It is then determined whether the alternative upstream frequency is preferable over the frequency presently being used. If so, the physical receiver is configured to operate normally under the set of operational parameters associated with the logical receiver.

Abstract: A method and system for locating faulty components in a cable modem network configured within a hybrid fiber-coaxial cable television system by tabulating modem performance data are described. A method of isolating problematic components in a cable modem network includes determining whether a cable modem transmitted a polling message to a central destination during the modem's allotted time interval. A media access control layer, located within a cable modem termination system (CMTS), keeps a miss count for the cable modem that reflects the number of times the cable modem does not transmit a polling message to the CMTS during its allotted time. The media access control layer determines whether the cable modem is changing states. This data and the miss count are tabulated in a form that can be analyzed by a correlation module to determine characteristics of the cable television plant.

Abstract: A media access control (MAC) unit in a CMTS assigns a normal time slot to a cable modem being tested for its upstream transmission quality. An FFT generator or engine operating in conjunction with the CMTS is informed of this normal time slot. A dummy time slot, not assigned to any cable modem, is created and the FFT generator is informed of the dummy time slot. A number of FFT measurements of the upstream channel are generated during the normal time slot and during the dummy time slot. FFT measurements of the upstream spectrum taken during the normal time slot are compared to FFT measurements taken during the dummy time slot. Through this comparison, undesirable noise spurs, if any, can be detected in the upstream spectrum caused by the cable modem being tested.

Abstract: A technique is disclosed for selectively adjusting the power and/or frequency of cable modems without relying solely on the most recent measurement of these values to determine whether a change is necessary. Rather, it considers multiple recent measurements and from these makes its assessment. In one approach, the technique employs an average of the recent measurements to determine whether a change in power or frequency is necessary. There are actually at least three determinations that can make use of multiple recent measurements. These include (1) determining whether the signals are fluctuating to an extent that requires a special adjustment technique, (2) determining whether an adjustment is necessary (using the special technique), and (3) determining how large of an adjustment is necessary.

Abstract: An flexible address translation method allows a computer network to automatically learn that a visiting node has attached and then automatically establish a virtual gateway so that the visiting node can communicate through the network with local nodes, other visiting nodes, and/or Internet sites. The network performs an address translation to enable the connectivity of the visiting node. The network maintains one or more globally unique outside addresses that point to it. When a visiting node connects to the network, the network translates the source address of packets from the node to a particular one of its outside addresses. The network also replaces destination addresses in packets received by the network that are addressed to the particular outside address. Specifically, the network replaces the globally unique outside address with the “home” address of the visiting node.

Abstract: A method and system for locating faulty components in a cable modem network configured within a hybrid fiber-coaxial cable television system by tabulating modem performance data are described. A method of isolating problematic components in a cable modem network includes determining whether a cable modem transmitted a polling message to a central destination during the modem's allotted time interval. A media access control layer, located within a cable modem termination system (CMTS), keeps a miss count for the cable modem that reflects the number of times the cable modem does not transmit a polling message to the CMTS during its allotted time. The media access control layer determines whether the cable modem is changing states. This data and the miss count are tabulated in a form that can be analyzed by a correlation module to determine characteristics of the cable television plant.

Abstract: A device, system and method are disclosed for locating clean channels for upstream data carriers that are certain to have lower noise levels than the currently utilized channel used for carrying data upstream, thereby enabling intelligent placement of an upstream data carrier in a cable television system utilizing cable modems for two-way data transmission. A spectrum analyzer is placed in a cable modem termination system located in a headend of a cable television system. The spectrum analyzer contains a programmable device comprised of programmable circuitry. The circuitry is operable in a first mode to receive a signal having an associated frequency spectrum made up of several channels. The circuitry also determines a noise level for each of the channels. The circuitry is also operable in a second mode to receive the signal described above and filter the signal to generate several filtered signals where each filtered signal corresponds to one of the channels.

Abstract: Methods, apparatus, and computer-readable media are disclosed for performing diagnostic tests of a communication link between a headend and a cable modem without having to assign an IP address to the cable modem. The diagnostic tests are performed at the MAC layer and test the state of the hardware between and including the cable modem termination system (CMTS) and a selected cable modem. By doing so, a network operator is able to more easily focus in on a potential problem in cable RF/MAC connectivity between the two components by first eliminating (or identifying) a problem with hardware before focusing on problem-solving at the software level, typically at the Network layer, at which point the cable modem is assigned an IP address. A network command is received from a network operator causing the CMTS to place a service identifier corresponding to a cable modem in possible need of diagnosing into a poll list.

Abstract: A method and system for locating faulty components in a cable modem network configured within a hybrid fiber-coaxial cable television system by tabulating modem performance data are described. A method of isolating problematic components in a cable modem network includes determining whether a cable modem transmitted a polling message to a central destination during the modem's allotted time interval. A media access control layer, located within a cable modem termination system (CMTS), keeps a miss count for the cable modem that reflects the number of times the cable modem does not transmit a polling message to the CMTS during its allotted time. The media access control layer determines whether the cable modem is changing states. This data and the miss count is tabulated in a form that can be analyzed by a correlation module to determine characteristics of the cable television plant.

Abstract: Disclosed are a method apparatus for performing periodic ranging with a cable modem. It is determined whether an actual power level of the cable modem requires adjustment to a desired power level and it is indicated to the cable modem that it should adjust the actual power level to an adjusted power level that differs from the actual power level of the cable modem by less than or equal to a first dynamic range associated with the cable modem. In one extension of this method, the first dynamic range represents a difference between a modem dynamic range of the actual power level output by the cable modem and a head end dynamic range for recognizing the actual power level output by the cable modem.

Abstract: An flexible address translation method allows a computer network to automatically learn that a visiting node has attached and then automatically establish a virtual gateway so that the visiting node can communicate through the network with local nodes, other visiting nodes, and/or Internet sites. The network performs an address translation to enable the connectivity of the visiting node. The network maintains one or more globally unique outside addresses that point to it. In other words, packets addressed to the one or more outside addresses are routed to the network. When a visiting node connects to the network, the network translates the source address of packets from the node to a particular one of its outside addresses. The network also replaces destination addresses in packets received by the network that are addressed to the particular outside address. Specifically, the network replaces the globally unique outside address with the “home” address of the visiting node.

Abstract: 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.

Abstract: A system and method are disclosed for calibrating a line card having a gain control circuit and memory device. The gain control circuit is configured to receive an input signal and an adjustment signal and to output an adjusted output signal that is based on the input signal and the adjustment signal. The gain control circuit also is configured to alter the adjustment signal to a nominal adjustment value so that an adjusted amplitude value of the adjusted signal converges with a nominal amplitude value. A first input signal, a first adjustment signal, and a nominal amplitude value are provided to the gain control circuit. A first nominal adjustment value is determined. The first nominal adjustment value is substantially permanently stored within a first address of the memory device with the first address being associated with the first input signal.