SP-RFI-I03-980202 datasheet(39/200 Pages) ETC

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Radio Frequency Interface Specification

SP-RFI-I03-980202

The CM MUST support all burst profiles commanded by the CMTS via the Burst Descriptors in the UCD

(Section 6.3.2.2), and subsequently assigned for transmission in a MAP (Section 6.3.2.3).

Table 4-4. Burst Profile Attributes

Table 4-5. User Unique Burst Parameters

The CM MUST implement the Offset Frequency to within

±10 Hz.

Ranging Offset is the delay correction applied by the CM to the CMTS Upstream Frame Time derived at the CM,

in order to synchronize the upstream transmissions in the TDMA scheme. The Ranging Offset is an advancement

equal to roughly the round-trip delay of the CM from the CMTS. The CMTS MUST provide feedback correction

for this offset to the CM, based on reception of one or more successfully received bursts (i.e., satisfactory result

from each technique employed: error correction and/or CRC), with accuracy within 1/2 symbol and resolution of

1/64 of the frame tick increment (6.25 µsec/64 = 0.09765625 µsec = 1/4 the symbol duration of the highest

symbol rate = 10.24 MHz-1). The CMTS sends adjustments to the CM, where a negative value implies the

Ranging Offset is to be decreased, resulting in later times of transmission at the CM. CM MUST implement the

correction with resolution of at most 1 symbol duration (of the symbol rate in use for a given burst), and (other

than a fixed bias) with accuracy within

±0.25 µsec plus ±1/2 symbol owing to resolution. The accuracy of CM

Burst Profile Attributes

Configuration Settings

Modulation

QPSK, 16 QAM

Diff Enc

On/Off

Preamble Length

0-1024 bits (Note Section 4.2.5)

Preamble Value offset

0 to 1022

FEC Error Correction (T bytes)

0 to 10 (0 implies FEC = off)

FEC Codeword Information Bytes (k)

Fixed: 16 to 253 (assuming FEC on)

Shortened: 16 to 253 (assuming FEC on)

Scrambler Seed

15 bits

Maximum Burst Length (minislots)1

A burst length of 0 mini-slots in the Channel Profile means that the burst length is vari-

able on that channel for that burst type. The burst length, while not fixed, is granted

explicitly by the CMTS to the CM in the MAP.

0 to 255

Guard Time

5 to 255 symbols

Last Codeword Length

Fixed, shortened

Scrambler On/Off

On/Off

User Unique Parameter

Configuration Settings

Power Level

Values in table apply for this given channel and symbol rate.

+8 to +55 dBmV (16QAM)

+8 to +58 dBmV (QPSK)

1-dB steps

Offset Frequency

Range =

±32 kHz; increment = 1 Hz;

implement within

±10 Hz

Ranging Offset

0 to (2

16 - 1), increments of 6.25

µsec/64

Burst Length (mini-slots) if variable on this

channel (changes burst-to-burst)

1 to 255 mini-slots

Transmit Equalizer

Coefficients

1(advanced modems only)

Up to 64 coefficients; 4 bytes per

coefficient:2 real and 2 complex

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