2 Digital subscriber line VDSL2
2.5 Data transfer capabilities

Block PMS-TC is designed to adapt and secure the subscriber data into a format suitable for transmission over twisted pair. It accepts from block TPS-TC individual participant data streams. Block PMS-TC includes into these data flow headers, formats it into VDSL2 frames, and ensures randomization of periodic sequences by scrambling, adding a bit of security and interleaving. These procedures are applied to each data flow path separately.

The basic procedure for data processing in the block PMS-TC.

Transmission paths for VDSL2 connections can be in general:

- without data interleaving (mode FAST) - that means, low delay in transmission which is necessary for real-time transmission, but also a low resistance against impulse interference.
- with data interleaving (mode INTERLEAVE) - a higher delay in transmission, which is not a defect, for example, when transferring data to the Internet (typically realized through FTP (File Transfer Protocol)), but also with higher resistance against impulsive interference.

Interleaving is a technique that enhances the ability to detect and correct errors resulting from impulse interference during transmission. Corrupted data is possible in the terminal equipment repair and it is not possible to be re-transferred data from the source. This capability leads to increase the transmission efficiency.

Disadvantage of interleaving is the increasing of transmission delay.

Interleaving gradually created a data frame with subscriber data divides into a number of parts. Ranking individual parts are defined manner swaps (interleaves). This modified frame is sent to the transmission path. Impulse noise during transmission may cause the cluster of errors in the transmitted data frame. On the receiving side, parts of the damaged frames are re-ordered again into the original order. It is very likely that the burst error during re rearrangement into different parts of the framework. Such errors can be stretched to better detect and repair using Reed-Solomon coding (see. Below). The disadvantage is the increase in delay (tens to hundreds of milliseconds) because the data frame to the transmitting side does not transmit immediately after assembly of the lead, but it is necessary to delay it for rearrangement. Similarly, there is a delay on the receiving side. The advantage of striping is to obtain a higher resistance against impulsive noise that bothers especially during video transmissions of encoded MPEG (Moving Picture Experts Group) standards. For video broadcasts with MPEG encoding, the effect of impulse noise manifests itself as so-called “blocking effect”. To restore the image information is necessary to wait for the transfer key frame.