Interleave Delay; Fast Mode; Configured Versus Actual Rate - ZyXEL Communications AAM1212 User Manual

Adsl2+ module over pots in ip dslam

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AAM1212 User's Guide

For example, you could set up different profiles for different kinds of accounts (for example,

economy, standard and premium). Assign the appropriate profile to an ADSL port and it takes

care of a large part of the port's configuration maximum and minimum transfer rates. You still

get to individually enable or disable each port, as well as configure its channels and

operational mode. See later in this chapter for how to configure profiles.

8.4 Interleave Delay

Interleave delay is the wait (in milliseconds) that determines the size of a single block of data

to be interleaved (assembled) and then transmitted. Interleave delay is used when transmission

error correction (Reed- Solomon) is necessary due to a less than ideal telephone line. The

bigger the delay, the bigger the data block size, allowing better error correction to be

performed.

Reed-Solomon codes are block-based error correcting codes with a wide range of applications.

The Reed-Solomon encoder takes a block of digital data and adds extra "redundant" bits. The

Reed-Solomon decoder processes each block and attempts to correct errors and recover the

original data.

Fast mode means no interleaving takes place and transmission is faster (a "fast channel"). This

would be suitable if you have a good line where little error correction is necessary.

You configure the maximum rate of an individual ADSL port by modifying its profile or

assigning a different profile to the port. However, due to noise and other factors on the line, the

actual rate may not reach the maximum that you specify.

Even though you can specify arbitrary numbers for a profile, the actual rate is always a

multiple of 32 Kbps. If you enter a rate that is not a multiple of 32 Kbps, the actual rate will be

the next lower multiple of 32Kbps. For instance, if you specify 60 Kbps for a port, the actual

rate for that port will not exceed 32 Kbps, and if you specify 66 Kbps, the actual rate will not

be over 64Kbps.

Regardless of a profile's configured upstream and downstream rates, the AAM automatically

limits the actual rates for each individual port to the maximum speeds supported by the port's

ADSL operational mode. For example, if you configure a profile with a maximum

downstream rate of 25000 Kbps, and apply it to a port set to use G.dmt, the AAM

automatically uses a maximum downstream rate of 8160 Kbps. This means that if you

configure a profile with very high rates, you can still use it with any port. See

for a list of the maximum rates supported by the different ADSL standards.

Table 14 on page

Chapter 8 ADSL Port Setup

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