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show controllers cable-modem mac
Table 8
Field
DS Symbol Rate
DS QAM Mode
DS Search
US ID
US Frequency
US Power Level
US Symbol Rate
Ranging Offset
Mini-Slot Size
Change Count
Preamble Pattern
Burst Descriptor:
Interval Usage Code
Modulation Type
Differential Encoding
Preamble Length
FEC Error Correction
FEC Codeword Info Bytes
Scrambler Seed
50
Cisco IOS Release 12.0(5)T
Show Controllers Cable-Modem MAC State Field Descriptions (continued)
Description
Downstream frequency in symbols per second.
Downstream modulation scheme being used by the Cisco uBR924.
Frequency bands scanned by the Cisco uBR924 when searching for a downstream
channel. The Cisco uBR924's default frequency bands correspond to the North
American EIA CATV channel plan for 6 MHz channel slots between 90 MHz and
858 MHz.
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.
Transmission frequency used by the Cisco uBR924 in the upstream direction.
Transmit power level of the Cisco uBR924 in the upstream direction.
Upstream frequency in symbols per second.
Delay correction (in increments of 6.25 µs/64) applied by the Cisco uBR924 to the
CMTS upstream frame time derived at the Cisco uBR924. 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 uBR924 from the CMTS.
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.
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 uBR924 can quickly decide that the remaining fields
have not changed, and may be able to disregard the remainder of the message.
Byte pattern used for the preamble.
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.
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
Upstream modulation format. (1 = QPSK; 2 = 16QAM)
Indicates whether or not differential encoding is used. (1 = yes; 2 = no)
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.
Length of the forward error correction in bytes. The range is 0-10 bytes; a value of 0
implies no forward error correction.
Number of information bytes in the FEC codeword.
15-bit seed value loaded at the beginning of each burst after the register has been
cleared. Not used if scrambler is off.
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