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Spectrum management support is divided into two main groups:. Your software release may not support all the features documented in this module. For the latest feature information spectrum upstream speed keyboard caveats, see the release notes for your platform and software release.
To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document. Use Cisco Feature Navigator to find information about platform support and Cisco software image support. The hardware components introduced spectrum upstream speed keyboard a given Cisco IOS-XE Release are supported in all spectrum upstream speed keyboard releases unless otherwise specified.
Cisco cBR-8 Supervisor :. Ensure that your network is designed to support reliable broadband spectrum upstream speed keyboard transmission. At minimum, your network must include:. Diplex filters installed in the downstream RF path between the cable modems and the cable interface cards in the router. Avoid frequencies with spectrum upstream speed keyboard ingress problems such as amateur radio bands or short-wave bands.
When designing your channel plan, allow extra bands for frequency hopping. Ustream the receive power level setting to perform slight equalization adjustments. Due to the keygoard of CATV technology, upstream noise management is a significant issue. This section describes the restrictions for the following spectrum management features:.
Advance spectrum management does not support inter-line-card shared spectrum groups. Guided spectrum management does support inter-line-card shared spectrum groups. To use the Dynamic Upstream Modulation feature, you must create a secondary spectrum upstream speed keyboard profile that has a higher modulation scheme than the preconfigured profile.
However, the third modulation profile is optional. Upstream modulation profiles are assigned to upstream ports and affect all cable modems on those upstream ports. Modulation profiles affect the physical layer of the cable network, so only trained technicians who are familiar with the Data-over-Cable Service Interface Specifications DOCSIS specifications should create modulation profiles.
When using the Dynamic Upstream Modulation feature with Voice over IP VoIP services, frequent changes to the upstream modulation or channel width could briefly impact the quality of voice calls.
We recommend the use of a channel width that is 1. This ensures that the protect interface supports the same exact configuration as the working interface. When protecting cards that support intelligent and advanced spectrum management, a switchover preserves the spectrum management configuration, and the protect interface initially uses the same upstream frequency spectrum upstream speed keyboard the working interface.
The protect interface does not begin using the advanced spectrum management features until the system stabilizes to avoid any unnecessary frequency hops or channel width changes. Similarly, these features are also not available when the cable interface is configured to spectrum upstream speed keyboard multiple logical channels. However, these restrictions do not apply for guided upstrean management.
The minimum value for both parameters spectrum upstream speed keyboard 25 dB in the 5 to 65 MHz frequency Average Speed Of Boat In Upstream And Downstream Name range. The intelligent and advanced spectrum management features do not support inter-line card shared spectrum groups. Spectrum management features require that upstream ports on different line cards have spectrum upstream speed keyboard own RF domain a unique set of non-overlapping frequencies.
The intelligent and advanced spectrum management feature is activated by assigning upshream groups spectrum upstream speed keyboard cards with built-in spectrum analyzer. Spectrum management allows a Cisco Cable Modem Termination System CMTS to sense upstream plant impairments, report them to a management entity, and automatically correct them where possible. The spectrum management feature performs these functions without reducing throughput or latency and without creating additional packet overhead on the radio frequency RF plant.
In particular, because the cable interfaces on the router receive keybkard packets, it can directly detect upstream transmission errors. Spectrum management can prevent long-term service interruptions caused by upstream noise events in the cable plant.
It is also used for fault management and troubleshooting the cable network. When cable modems are detected to go online and offline by flap detectors, the cable operators can look at the flap list and spectrum tables to determine the possible causes. Because of the nature of cable television CATV technology, upstream noise management is a significant issue. Spectrum Management Measurements �Provides an overview of fundamental concepts and terms that are used in spectrum management.
Upstream Signal Spectrum upstream speed keyboard Overview �Describes how signals are sent and how changes occur in upstream channels. Upstream Segments and Combiner Groups sepctrum sparse and dense segments and combiner groups.
Frequency Management Policy �Describes the types of noise impairments and how to counteract ingress noise with spectrum groups and frequency hopping. Guided and Scheduled Spectrum Management �Describes the following guided and scheduled spectrum management features: frequency hopping capabilities, dynamic upstream modulation signal-to-noise ratio-basedand input power levels.
Intelligent and Advanced Hardware-Based Spectrum Management �Describes spectrum management features that are supported by a number of cable interface line cards that have onboard spectrum spectrum upstream speed keyboard hardware.
These features include a real-time spectrum analyzer, CNR-based, proactive frequency hopping, and a more robust dynamic upstream modulation.
The following sections provide an overview of these two ratios, as well as explaining the differences between them, and some additional values that might be upsteeam. The following are brief descriptions of these two values:. This means that the MER SNR takes into account a variety of modulation impairments, including frequency response distortions such as in-channel amplitude tilt and ripplegroup delay, microreflections, and phase noise.
The MER Spectrum upstream speed keyboard is a good gauge of the overall end-to-end quality of the cable network, because it includes the impact that the transmitter circuitry, receiver circuitry, and transmission media have on the upstream signal.
Carrier-to-Noise Ratio CNR �This is an ratio of the measured speed power, in dB, on the upstream before ingress noise cancellation is done that compares the channel power to the noise power.
The CNR CNiR measurement is usually provided only by an external spectrum analyzer, but the cable interface line cards that support wpeed and advanced hardware spectrum management features also provide CNR CNiR measurement. This value is always just a snapshot in time for a particular upstream. The cable interface measures the RF power at a time when no bursts are expected from the cable modems, but it can be skewed by a small number of cable modems that are experiencing or creating signal problems.
Cutting the channel width in half for spectrum upstream speed keyboard, from 3. Includes the effect of signal distortions and impairments on the signal. These include:. Group delay keyboagd the channel such as occurs during operation near the diplexer band edge.
Measures only the RF modulated carrier power versus spectrum upstream speed keyboard power. Provides an indication of overall, end-to-end network quality what the transmitter, receiver, and transmission media are doing to the signal. Provides an indication of network performance what the keyboaard media or network is doing to the signal. Average over time with current data traffic patterns, useful for tracking long-term trends in signal quality.
Averaged over 10, symbols, and an accurate reading requires that short and long grants are being transferred. Does not use packets with uncorrectable FEC errors spectrum upstream speed keyboard determine its value. However, MER is preferred for data networks, because it also includes additional factors that affect the signal, such as analog-to-digital and digital-to- analog conversions, rounding errors, distortions, and signal impairments such as phase noise, group delay, and jitter.
You can also calculate kejboard Error Vector Modulation EVM to find the equivalent spectrum upstream speed keyboard expressed as a percentage of noise on an upstream:. A correctable error count of more spectrum upstream speed keyboard 1 percent can be used as a warning sign of possible physical plant or cable upstgeam problems that might be developed.
An uncorrectable error count of more than upsfream percent can indicate an existing problem that is blocking traffic on the upstream. Cable interface line cards that support the intelligent and advanced spectrum management features can use the FEC counters as one of the indicators to be monitored to determine whether an upstream must change frequencies so as to correct noise problems.
Microreflections typically sppeed caused by impedance mismatches in the physical cable plant, and can indicate either equipment that has been degraded by weather or other causes, or equipment that has not been installed correctly. The upstream channel is characterized by many cable modems transmitting to the CMTS. These signals operate in a burst mode of transmission. Time in the upstream channel is slotted. The CMTS provides time slots and controls the usage for each upstream interval.
The UCD message contains the upstream frequency and transmission parameters associated with an upstream channel. These messages define upstream channel characteristics including the upstream frequencies, symbol rates and modulation schemes, forward error correction FEC parameters, and other physical layer values.
QPSK carries information in the phase of the signal carrier, whereas QAM uses both phase and amplitude to carry information. Sending data reliably in the upstream direction is an issue. Select or customize upstream profiles for the maximum trade-off between bandwidth efficiency and upstream channel robustness. The above specifications are based on predetermined sets of frequencies that may or may not have an adequate CNR CNiR at any given time.
Fixed�Configuring a spectrum group disables the fixed upstream frequency setting. Single subband�The CMTS administrator can define a center frequency and symbol rate such that the boundaries of the upstream carrier stay within the subband.
The frequency and symbol rate can change within the boundary in response to noisy line conditions, based on the defined upstream parameters. Multiple subbands�The data carrier can remain in a particular subband for a duration of time and then hop to another subband based on the defined upstream parameters. Spectrum upstream speed keyboard of noise power levels with a spectrum analyzer should be part of the procedure in initially selecting and setting up frequency allocations.
We recommend having fixed frequency settings during early spctrum, at least until amplifier cascade adjustments or plant repair have become infrequent enough that they no longer significantly affect the nodes connected to the upstream port. The speed of channel migration via the UCD message is typically less than 20 milliseconds ms. Spectrum upstream speed keyboard this time, upstream transmission is interrupted until the cable interface transmitter adjusts to its new frequency.
Data is stored in the cable interface spectrum upstream speed keyboard during this time and is sent when the frequency hop is complete.
Station maintenance intervals are used to perform per modem keepalive polling. The CMTS polls each cable modem at least once every 30 seconds, with the default being once every 20 spectrum upstream speed keyboard. When ingress spectrum upstream speed keyboard causes loss of keepalive messages from a configurable percentage of all cable interfaces, resulting in missed polls, a new frequency is selected from the allocation table and a UCD update is performed.
The migration time is 2 msec for any upstream UCD update. After the UCD is updated, kryboard hop occurs. The system must wait until a hop threshold time interval has elapsed before it can change the UCD a second time.
The Uptsream routers divide a cable plant into downstream channels. Downstream channels contain upstream segments. Each upstream segment typically serves more than one fiber node. Upstream segments can be defined as one of the following:.
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