Analysis of why ADSL2 becomes a new favorite of the Network

This article analyzes the reasons why the ADSL2 standard has become a new favorite of the network. There are many problems with the ADSL2 standard on the network. For various ADSL2 standards, the following is a question and answer topic, hoping to cover all questions about the use of ADSL2 standards by netizens.

Enhanced interoperability

In the ADSL2 standard, more parameters will be transmitted during the training phase. In addition, many parameters are determined by the receiver end rather than the CO end. For example, the receiver selects the Pilot channel Pilot Tone Based on the noise ).

PTM Transmission Mode

The ADSL2 standard defines the PTM packet transfer mode outside of the STM and ATM. In this mode, the IP package is directly encapsulated in the HDLC frame format. If the chicken ribs ATM can finally be left behind. Only the DSLAM with the PTM architecture is the pure ip dslam. Without the Access System of ATM, it can provide higher transmission efficiency, lower cost, and simpler network management.

Further reachable distance

Traditional G. DMT does not define single-bit star map modulation, which makes it impossible to establish a connection when the signal-to-noise ratio is small over a long distance. The ADSL2 standard allows single-bit modulation so that further distances can be reached.

Improved data transmission efficiency

In the traditional G. DMT physical layer frame format, the minimum overhead is 32 Kbps, while in the ADSL2 standard, the minimum overhead is 4 Kbps.

ADL Mode

The ADSL2 standard defines the full digital loop mode. In this mode, the bandwidth of ADSL covers the voice part of the low-frequency end, it can provide more powerful data services for users who do not need voice services.

Enhanced Power Management

The ADSL products that comply with the definition of G. DMT are always in Full-Power Transmission regardless of whether the data is actually transmitted. In the ADSL2 standard, three transmission statuses are defined: L0, L2, and L3. L0 is full-power transmission during normal operation. When the user does not transmit data at intervals, such as browsing the webpage, the CO end will quickly enter the L2 low-power state, when the user transfers data again, the CO end quickly enters the L0 status.

When the user has not transmitted data for a limited period of time, both the CO and CPE end enter the L3 sleep mode to further reduce the transmit power. At this time, the physical layer link is still connected, however, there is no payload transfer. When there is a data transfer requirement again, it takes about three seconds to quickly enter the L0 mode after training.

In addition to maintaining the CO-end Power Cutback defined in G. DMT, The ADSL2 standard Power management also defines the CPE-end Power Cutback. In this way, both CO and CPE can reduce transmission power, reduce power consumption, and reduce Line crosstalk when the signal quality of the line is good.