Figure 6-22: 2D12U Cable Access Module (CAM) and PIC Rear POWER OOS Power Out of Service Front POWER OOS Power Out of Service Front DOW N TES T (- 30 dV ) Downstream Test Upstream: Port 0-7 - available Downstream: Port 0 - available Port 1 - available D1 D2 ARRIS
PIC-CAM (E)ARRIS PIC-SCMARRIS ARRIS PIC-SCM (O)PIC-SCMARRIS
ARRIS
PIC-CAM (O) PIC-CAMARRIS SPARE ARRIS
Even Odd Spare
U0 U2 U1 U3 U4 U5 U6 U7 D1 D0 U7 U0 U4 U5 U6 U1 U3 D0 D1
Overview
The 2Dx12U Cable Access Module provides full DOCSIS 2.0 functionality including ATDMA and SCDMA plus PHY-layer ingress cancellation and a number of other key features. This new functionality enables the use of parts of the spectrum previously unavailable due to noise. It also provides improved spectral efficiency (bits/Hz) in upstream carriers.
Each 2Dx12U CAM supports:
• Two 30-42 Mbps downstream IF channels with integrated upcon- verters, with configurable downstream center frequencies from 91- 857 (North America) or 112-858 (Europe) MHz
• Eight upstream physical connectors (numbered 0-7)
• Up to twelve 0.32-30.72 Mbps physical upstream channels (numbered 0-11)
• Range of upstream frequencies configurable for North America, Japan, or Europe:
-
5-42 MHz (DOCSIS)-
5-55 MHz (Japan)-
5-65 MHz (EuroDOCSIS)• Multiple logical channels per physical upstream channel
If desired, each physical upstream channel can be subdivided into two logical upstream channels (numbered 0 and 1). They are subchannels that dynamically share the upstream channel’s bandwidth using time division multiplexing. The share of upstream bandwidth allocated to each of the two logical channels changes according to the requests made by the modems on each logical channel.
• Four channel types are supported: TDMA, ATDMA, SCDMA, and TDMA&ATDMA.
Typically, one logical upstream channel would be SCDMA and the other would be configured for either TDMA, ATDMA, or TDMA&ATDMA
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Installing Modules and System Bring-upPrimary Software Function The primary software function on the Cable Access Module includes:
• CM Ranging and Registration • MAC Address Learning
• DOCSIS Functionality: Packet Classification, Service Flows, Dynamic Signaling (DSx), Baseline Privacy Interface (BPI+), CM Upstream Bandwidth Scheduling (MAPs), Payload Header Suppression (PHS), Packet defragmentation, packet de-concatenation, and counts collec- tion.
• Upstream and Downstream Policing
• Operations, Administration, Maintenance & Provisioning (OAM&P) including initialization and fault recovery code.
• Connection Admission Control (CAC) • PacketCable DSx processing
CAC is a proprietary means of controlling set-up and distribution of service flows across the shared resources in a cable data network.
Downstream Test Ports in
CAM Faceplate The CAM faceplate test points are meant to verify the presence of a down-stream signal. They provide a power level that is 30 dB (± 3 dB) less than the configured downstream signal strength. These test points are not meant to be used for signal calibration or for detecting signal spurs. Down- stream testing at these points does not interfere with CAM functionality. When the test ports are not in use, 75 Ohm terminations should be in place.
LED Status The LED status descriptions for the CAM are listed in Table 6-9 below:
Physical Interface Cards There are three types of CAM PICs: Even, Odd, and Spare.
Table 6-9: 2Dx12U Cable Access Module LED Descriptions
Front LEDs
Module Status Power Out of Service
On Off Powered and in normal service state
Flashing On Flashing = 1.6 second period. Module power is off: either slot is not provisioned or module has been disabled. Persistent
Fast Flashing
On
Fast flashing = 6 times/second. Normal when card is first powered or restored. If fast flashing persists for more than
2 seconds, there is a serious power problem. On On Powered and out of service.
On Flashing Downloading data from SCM, initializing or running diagnostics.
The two basic variations of the Physical Interface Card for the CAM are illustrated in Figure 6-22, 2D12U Cable Access Module (CAM) and PIC, on page 6-46. One is intended for even-numbered slots; the other for odd. These PICs have offsetting upstream connectors in order to facilitate cabling. Order any system upgrades with this even/odd pairing in mind. A third type of PIC used behind CAMs is the CAM sparing PIC. It is required only for those CAMs acting as spares in a sparing group.
CAM PIC LED Status The LED status descriptions for the CAM PIC are listed in Table 6-10 below:
CAM Sparing PIC LED Status All three types of CAM PICs are equipped with a Sparing LED at the bottom
of the faceplate. These LEDs show which CAM in a sparing group has failed and which CAM is its group leader. Under normal conditions all Sparing LEDs will be off. When a CAM in a sparing group fails, traffic is transferred to its sparing group leader. In this case, the Sparing LEDs of the PICs of the failed CAM are and its group leader CAM are on.
Advanced Spectral Analysis Although not a function of the DOCSIS standard, the ARRIS 2Dx12U CAM
provides channel utilization statistics that can help operators characterize the noise on an HFC plant. This can help determine which frequencies, modulation rates, and multiplexing techniques deliver the best signal-to- noise ratios. Upon entry into the 2Dx12U CAM, the entire available spec- trum of each upstream input port is digitized. Digital signal processing techniques are used to measure SNRs with increased accuracy and to report on problems at the channel and even CM levels. Expected in release 5.x, these techniques will be the basis for channel optimization and frequency agility features.
2Dx12U Ingress Noise
Cancellation The 2Dx12U Ingress Cancellation feature provides administrative control over certain proprietary capabilities of the Broadcom BCM3140 dual- channel burst receiver. The BCM3140 has an ingress cancellation block that analyzes the noise environment of an upstream channel. It then suppresses narrow-band ingress or adjacent-channel interference.
NOTE
Ingress cancellation technology benefits cable operators by improving the immunity of upstream carriers to normal plant noise. It is not capable of providing perfect immunity and should not be considered a substitute for
Table 6-10: CAM PIC LED Descriptions
If CAM PIC LED Is… Then F-Connector Supports…
On (green) On (amber) Off
active downstream channel active upstream channel no active channel
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Installing Modules and System Bring-upThis feature enables the CMTS operator to perform the following tasks: • Enable or disable ingress cancellation on a per-receiver basis
• Control the amount of bandwidth allocated to ingress canceller oper- ation
• Monitor processing gain attributed to ingress cancellation
By default ingress cancellation is disabled because it consumes bandwidth. It can be enabled for any upstream channel using QPSK or QAM 8, 16, 32, or 64.
Analysis only occurs during unused burst intervals. These bursts have an SID that is not assigned to any service flow. The results of any given anal- ysis are applied to every burst up to the next unused burst. This implies that the potential accuracy of the canceller is directly proportional to the frequency of unused bandwidth allocations. Depending on the nature of the noise, however, an increase in potential accuracy does not necessarily result in a proportional increase in processing gain. Since real-world ingressors are static over relatively long intervals (ranging from millisec- onds to minutes), analysis rates that are smaller than the average ingress duration have little effect. On the other hand, if the frequency of ingress analysis bursts is set too high, this could have a negative impact on throughput.