Tag - ADSL

XDSL speeds

Different xDSL Equipment Overview

DSL has come a long way since its humble ADSL beginnings. The following is the final part in The History of DSL Trilogy. If you missed the Part I discussing the history of DSL, click here.  For a quick overview  of the 6 xDSL technologies in use today, visit Part II of the series.  Receive a Complementary Consultation

Equipment Used For DSL

There are a range of products on the market that deploy DSL services. The following are a few examples of Digital Subscriber Line Access Multiplexers (DSLAMs) and modems that deliver DSL broadband. Visit Part II of this series to learn more about the different types of DSL.


Some ADSL DSLAMs are compatible with all three ADSL standards such as the VX-1000HDX and the VX-1000MDX.
best DSLAM

The VX-1000HDX ADSL2+ IP DSLAM unit from Versa Technology is a mini-DSLAM designed for the deployment of access networks.


The VX-1000MDX ADSL2+ IP DSLAM unit from Versa Technology is a mini-DSLAM that supports ADSL, ADSL2/2+ AnnexA and AnnexM.


Some VDSL2 IP DSLAMs such as the VX-M2024S and the VX-MD4024 come with ADSL2/2+ ports for added flexibility.  

The VX-M2024S from Versa Technology is a 1.5U compact 24-port VDSL2 IP DSLAM with 2 Gigabit Ethernet Combo interfaces and built-in POTS/ISDN splitter.


The VX-MD4024 is a rack-mountable VDSL2 IP DSLAM. The unit supports two Gigabit Ethernet (GbE) trunk interfaces and 24 VDSL2 ports (ADSLx backward compatible).

VDSL2 Modems

Many VDSL2 modems offers ADSL2+ fallback such as the VX-VER522.

Versa Technology's VDSL2 with ADSL2+ fall back 802.11n router has integrated wireless 802.11n draft 2.0 technology, making it possible to provide high-speed wireless data rates of up to 300mbps and superior wireless coverage.


Most ADSL2+ modems support ADSL2 fallback such as theVX-VER170S.  

The VX -VER170S ADSL2+ bridge/router from Versa Technology provides advanced long Reach/Rate, and crosstalk-free technology.

Limiting Factors

One of the main limiting factors to DSL services is aging copper lines. Companies that seek to compete at fiber speeds like Verizon Communications and AT&T, have been accused of allowing their copper lines to deteriorate so as to replace them with fiber. In fact, Verizon communications has recently sold its wireline liabilities to Frontier Communications, a smaller telecom company that delivers DSL broadband to rural cities.  Another limiting factor to DSL is that subscriber speed directly correlates with how far away subscribers reside from the exchange.

The Future of xDSL

Even though DSL subscribers are declining, ISPs still desire to retain the profitability of copper lines. ISPS are investing in researching new vectoring methods to transmit broadband at faster speeds.  As WinterGreen research reports: “Copper represents an installed infrastructure worth trillions and too expensive to just replace. Fiber is too expensive to use it to replace all the copper.” The utility of copper lines will continue to defy the laws of obsolescence with improved vectoring methods such as G.fast and XG.Fast, which have successfully achieved downlink speeds of 1 Gbps and 5 Gbps respectively. Openreach has already begun trial test runs with the new chipset to determine its integrity in real world settings.  G.fast is still considered bleeding edge technology, but supporting standards such as G.inp promise to stabilize the consistency of signal speeds. To learn more about G.imp click here.  

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History of DSL - Part 1

Behind the Obscure History of DSL

If fiber and cable provide faster data rate transmission speeds than DSL services, have you ever wondered why many ISPs offer DSL?

Why We Need DSL

Digital Subscriber Line (DSL) is a type of access technology that delivers high-speed data via legacy copper lines. Internet Service Providers (ISPs) will oftentimes opt for DSL technology to extend the life of legacy copper lines and forego costly infrastructure investments. This post is part of a three-part series that overviews the History of DSL, Different DSL Types, and Different xDSL Equipment Types. Click here for Part II of the series which overviews the different DSL technologies available. Receive a Complementary Consultation Telephone companies initially deployed copper lines to support a booming analog telephone industry.  But with the emergence of new communication modes such as cellular data and the Internet, the demand for landline phones plummeted. As a result, telephone companies pivoted into becoming ISPs and repurposed copper lines to deliver high-speed broadband. But faster access technologies such as cable and fiber have caused DSL’s market share to steadily decline. According to TheNextWeb “DSL is the second-ranked access technology... At the end of June 2013, the 31 million DSL connections, or 34 percent of the fixed broadband market, lost 258,000 lines”. The future of DSL faces a paradox —while deployments are declining, the demand to deliver faster speed via copper lines is on the rise. New copper transmission methods such as G.Fast have achieved up to 1 Gbps in laboratory settings. Evolving DSL technologies such as G.Fast will prolong the utility of the legacy infrastructure. In addition, copper cables can be paired with fiber to create Hybrid Fiber-Coaxial (HFC) deployments, a more cost-efficient alternative to Fiber-To-The-Curb (FTTC) deployments. Though DSL is a mature technology, DSL is by no means obsolete.

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If we were to roll out a new G.Fast DSLAM, how many ports would it ideally support?
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The History of DSL

One of the Fathers of DSLEven though telephone companies such as Bell Systems were reaping profits from the monopolization of their industry, the profitability of emerging cable companies lured telephone companies to research new ways to transmit video across their existing copper lines. Once engineers discovered how to transmit digital signals via copper by using a higher frequency, they faced another setback — symmetrical download and upload speeds caused significant interference that delayed data transmission rates. Joseph W. Lechleider, known as one of the fathers of DSL, became part of Bell Labs in 1955. But it was not until the early 1980’s that he proposed to unevenly allocate bandwidth between download and upload speeds. Now known as Asymmetrical DSL, the new technology significantly eliminated electrical interference in copper lines. Unfortunately, the invention failed to create viable competition for cable. Asymmetrical DSL had to wait until the dawn of the Internet to prove its utility. Initially, dial-up speeds more than satisfied early internet browsing functions. But as websites grew more complex and began to use more data-rich content, dial-up speeds would no longer suffice.  Phone companies now had to compete with cable, satellite, and other broadband providers that offered faster data rates. That is when Joseph W. Lechleider’s invention finally came into play. ADSL allowed phone companies to retain a portion of their subscriber-base by boosting data speeds at a fraction of a cost if they were to upgrade to fiber or cable. At the same time, telecom companies did not have to invest in replacing their copper line infrastructures with other expensive (albeit faster) alternatives. To find out more about the most popular types of DSL technology in use today, stay tuned and follow us on Facebook, Twitter, or Linkedin to receive updates for Part II of this series.
adsl2/2+ FAQ

The 11 Most Frequently Asked Questions About ADSL2 & ADSL2+ Answered

ADSL2 and ADSL2+ technologies have enabled ISP providers to provide their customers with high-speed broadband via legacy copper lines.  We've compiled a list of  the 11 most commonly asked questions about ADSL2 & ADSL2+ to demystify the Digital Subscriber Line (DSL) technologies. If you’re interested in learning more about VDSLs, visit our VDSL/2 FAQ here. Receive a Complementary Consultation

1. What is ADSL2/ADSL2+?

ADSL2 and ADSL2+ are DSL technologies that deliver high-speed broadband using Plain Old Telephone Services (POTS). Copper telephone wires consist of at least 25 or more twisted wire pairs making transmission signals susceptible to crosstalk. ADSL2 and ADSL2+ utilize sophisticated modulation technologies to eliminate noise and interference in transmission signals. This allows for relatively error-free transmission via legacy copper lines.

2. How fast is ADSL2?

Actual speeds vary depending on networking environments and copper loop lengths. ADSL2 can achieve downstream data rates of up to 12 Mbps speeds at its source while ADSL2 can achieve up to 24 Mbps. ADSL2/2+ are best suited for longer loop lengths. ADSL2 can reach distances of up to 5,000 meters while ADSL2+ can achieve up to approximately 6,000 meters. Refer to the chart below to compare ADSL2, ADSL2+, and VDSL2 speeds. ADSL2/2+ vs. VDSL Speed Comparison Chart

3. What is the farthest ADSL2/2+ can reach?

ADSL2 can reliably support high-speed broadband to loop lengths as far as 5,000 meters while ADSL2+ can achieve slightly longer distances at 6,000 meters.

4. What are some ADSL2 improvements?

ADSL2 improves:
  •         Modulation Efficiency
  •         State Machine Initialization
  •         Coding Gain
  •         Signal Processing Algorithms
  •         Framing Overhead Reduction
  •         Seamless Rate Adaptation (SRA)
Seamless Rate Adaptation (SRA) allows the transceivers to adjust transmission rates according to changing networking conditions in real-time. SRA is a functionality that allows ADSL2 to decouple packets in the modulation layer while maintaining the framing layer parameters intact. This preserves the synchronicity of the information transmitted while modulation rates are adapted.  

5. Are ADSL2/2+ DSLAMs energy-efficient?

Yes. Most ADSL units provide consistent power feeding which not only wastes energy and resources but also increases heat dissipation which can damage equipment after prolonged usage. ADSL2 provides two energy-efficient power modes: L2 and L3 low-power modes to help conserve energy.  The L2 low-power mode can adjust power based on the traffic demands of an individual-per-use-case. ADSL2 units will kick into full power mode during traffic intensive applications such as occurs when downloading large files and revert back to L2 low-power mode when the surplus power is no longer necessary. The L3 low-power mode puts the transceiver at the Central Office (CO) to sleep after a period of inactivity.  

6. How does ADSL2/2+ achieve high data rates?

One of the features that enables ADSL2/2+ to achieve high data rates is channel bonding. ADSL2/2+ has the capacity to bond several telephone phone lines together to achieve higher bandwidth. ISPs can bond several channels to achieve a wider bandwidth and increase downstream and upstream data rates. Channel bonding resembles the process of adding more lanes to a freeway so that it can support more traffic. This flexibility enables Internet Service Providers (ISPs) to offer different tiered data rate services to subscribers.

7. Are ADSL2/2+ units compatible with previous versions of ADSL2?

Units with the “ADSL2 fallback” feature provide support for previous versions of ADSL standards. Units will revert to previous standards if connected to devices that support older standards so as to preserve compatibility.  

8. What is the difference between ADSL2/ADSL2+?

ADSL2 and ADSL2+ are variations of the same technology. ADSL2 utilizes frequencies between .14 MHz and 1.1 Mhz. ADSL2+ offers double the frequency range, between .14 Mhz and 2.2 Mhz. The wider channel bandwidth of ADSL2+ doubles its downstream data rates. ADSL2+ technology also has the capability of eliminating crosstalk. Since ADSL operates between the .14 to 1.1 Mhz frequency range, ADSL2+ will automatically transmit signals on the 1.1 to 2.2 range to prevent crosstalk. This functionality is especially useful when both ADSL2 and ADSL2+ services are present in the same binder on course to a customer’s premises.

9. What is the difference between Annex A vs. Annex B?

ADSL over POTS, more commonly known as Annex A, is used in North America. Europe on the other hand, utilizes Annex B which delivers ADSL over ISDN.  Annex A and Annex B provides approximately  24 D / 1.4 U Mbps rates.

10. What is the difference between Annex A vs. Annex M?

Also known as ADSL2 M and ADSL2+ M, Annex M provides a slight improvement in upstream rates when compared to Annex A. Annex M yields up 3.3 Mbps upstream data rates as opposed to the typical upstream rates of 1.4 Mbps in Annex A.

11. How old are the ADSL2/ADSL2+ standards?

The G.992.3 and G.992.4 ADSL2 standards were introduced in July 2002. The G.992.5 ADSL2+ standards received official standardization in 2003. Did you know that copper lines can now transmit gigabit speeds in laboratory settings? Find out more about the up and coming G. Fast technology here.
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