Difference Between Naked DSL ADSL 2 and ADSL 2
Naked DSL or ADSL2+ and ADSL2+ are broadband access technologies which are used to deliver high speed Internet access. Naked ADSL2+ will not come with PSTN while ADSL2 comes with a line PSTN. So in ADSL2 you must pay for additional line rental on the top of the payment of Internet access while in Naked ADSL2+ you do not need to pay the price of line rental. There are some advantages and disadvantages on both. You can choose either Naked ADSL2+ OR ADSL2 according to your requirements.
ADSL2+
ADSL2+ is the next generation technology of ADSL to give the high band of frequency by using the same copper lines. ADSL2+ can give up to 24 Mbps, but which depends on a lot of parameters. ADSL2+ was introduced in 2003 and it is an ITU norm g992.5.
ADSL2 utilizes two times the band of frequency of ADSL2 (2.2 MHz) downloads data rates is possible about 24 Mbps. The upload speed of ADSL2+ the speed stays as 1Mbps.
In short, ADSL2+ is better that ADSL2 or ADSL as far as speed of acess is concerned, but it does not mean that you can go through Internet faster in ADSL2+ than ADSL2 or ADSL. There are a lot of other parameters (more details here) which influence the speed or the throughput.
Naked DSL or Naked ADSL2+
Naked ADSL also comes from the same family of ADSL but main difference is, it does not come with a PSTN telephone line. That does not mean that it will not include a copper line, it comes via your copper pair only. It also gives the speed of ADSL2+, 24Mbps uplink and 1Mbps downlink.
In ADSL2+, you need to splitter at your end (the end of user) to separate the telephone line and data before you connect to the ADSL2+ router and the telephone. Splitter is not necessary in Naked ADSL2+
Naked ADSL2+ provisioned with all IP digital modes in ADSL2+ Annex I or Appends J (for POTS and PSTN) can give another 256 kbps on uplink since we do not use the low frequency band of PSTN voice.
Naked ADSL2+ is in general partnered with VoIP services and you can be allotted a local telephone number via Voice over IP services. It is referred as Local DID. (Direct Inward Dial) on the top of ADSL2+ router you may get a VoIP device or ADSL2 router it self comes with VoIP built-in functionality where you will get RJ11 (normal) phone output. You can connect your normal telephone in this port and get dial tone.
The entire telephone system work via Voice over IP protocol and these days there are available in very cheap packets in the market. You can either get the service of your naked ADSL2+ provider or you can buy the number from anyone else and configure. There are plans for 10 dollars to get unlimited minutes to anywhere in the world (Except certain countries and mobiles).
General Summary:
Comparatively Naked ADSL2+ has better plans of data and VoIP but even then people have mentality to go for a traditional PSTN telephone. Therefore they go with ADSL2+ rather than Naked ADSL2+. It will take time for people to change their mentality towards IP services until it hits the comparative price. The portability of number is less possible with the Naked ADSL2+ telephone numbers (DID). When you go for Naked ADSL2+ it is less likely that you can bring your existing telephone number to Naked ADSL2+ phone.