show controllers cable-modem mac

Table 12

show controllers cable-modem MAC State Field Descriptions (continued)

 

 

 

Field

 

Description

 

 

 

DS Frequency

 

Downstream frequency acquired by the Cisco uBR900 series during its last

 

 

initialization sequence.

 

 

 

DS Symbol Rate

 

Downstream frequency in symbols per second.

 

 

 

DS QAM Mode

 

Downstream modulation scheme being used by the Cisco uBR900 series.

 

 

 

DS Search

 

Frequency bands scanned by the Cisco uBR900 series when searching for a

 

 

downstream channel. The Cisco uBR900 series’ default frequency bands correspond

 

 

to the North American EIA CATV channel plan for 6 MHz channel slots between 90

 

 

MHz and 858 MHz.

 

 

 

US ID

 

Identifier of the upstream channel to which this MAC management message refers.

 

 

This identifier is arbitrarily chosen by the CMTS and is only unique within the

 

 

MAC-sublayer domain.

 

 

 

US Frequency

 

Transmission frequency used by the Cisco uBR900 series in the upstream direction.

 

 

 

US Power Level

 

Transmit power level of the Cisco uBR900 series in the upstream direction.

 

 

 

US Symbol Rate

 

Upstream frequency in symbols per second.

 

 

 

Ranging Offset

 

Delay correction (in increments of 6.25 µs/64) applied by the Cisco uBR900 series to

 

 

the CMTS upstream frame time derived at the Cisco uBR900 series. Used to

 

 

synchronize the upstream transmissions in the time division multiple access

 

 

(TDMA) scheme, this value is roughly equal to the round-trip delay of the

 

 

Cisco uBR900 series from the CMTS.

 

 

 

Mini-Slot Size

 

Size T of the mini-slot for this upstream channel in units of the timebase tick of

 

 

6.25 µs. Allowable values are 2, 4, 8, 16, 32, 64, or 128.

 

 

 

Change Count

 

Incremented by 1 by the CMTS whenever any of the values of this channel descriptor

 

 

change. If the value of this count in a sebsequent upstream channel descriptor (UCD)

 

 

remains the same, the Cisco uBR900 series can quickly decide that the remaining

 

 

fields have not changed, and may be able to disregard the remainder of the message.

 

 

 

Preamble Pattern

 

Byte pattern used for the preamble.

 

 

 

Burst Descriptor:

 

A compound type/length/value (TLV) encoding that defines, for each type of

 

 

upstream usage interval, the physical-layer characteristics that are to be used during

 

 

that interval. Each burst descriptor is given an identifying number.

Interval Usage Code

Each upstream transmit burst belongs to a class which is given a number called the

 

 

IUC (interval usage code). Bandwidth MAP messages are used by IUC codes to

 

 

allocate upstream time slots. The following types are currently defined:

 

 

1. Request: bandwidth request slot

 

 

2. Request/Data: bandwidth request or data slot

 

 

3. Initial Maintenance: initial link registration contention slot

 

 

4. Station Maintenance: link keep-alive slot

 

 

5. Short Data Grant: short data burst slot

 

 

6. Long Data Grant: long data burst slot

 

 

Modulation Type

Upstream modulation format. (1 = QPSK; 2 = 16QAM)

 

 

Differential Encoding

Indicates whether or not differential encoding is used. (1 = yes; 2 = no)

 

 

 

Preamble Length

 

Length of the preamble in bits. This value must be an integral number of symbols—a

 

 

multiple of 2 for QPSK; a multiple of 4 for 16QAM.

 

 

FEC Error Correction

Length of the forward error correction in bytes. The range is 0-10 bytes; a value of 0

 

 

implies no forward error correction.

 

 

FEC Codeword Info Bytes

Number of information bytes in the FEC codeword.

 

 

 

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Cisco Systems UBR900 specifications Us Id