17-10-2016, 11:08 AM
1459344745-numbertank.pptx (Size: 842.16 KB / Downloads: 5)
There are numerous ways to make free calls from PC/mobile to mobile. Some popular ones are- Google Hangout, Skype, Whats app etc.
But there is one big problem with that i.e. both parties should have an internet connection.
However, many people still don’t have high-speed internet in their phone. (2G is not sufficient for VoIP communication) So we need a workaround that enable to make free calls from that don’t require the recipient to have an internet connection.
Using their service, one can make free calls from web to traditional phone numbers including mobile phones quite easily.
HOW VOIP WORKS ?
VOIP calls or calls over the internet in India are not allowed to terminate over normal PSTN (public switched telephone network) lines, so it is interesting to see how Numbertank functions.
The interesting thing about VoIP is that there is not just one way to place a call. There are three different "flavours" of VoIP service in common use today:
ATA (analog telephone adaptor)
IP Phones
Computer-to-computer
HOW NUMBERTANK WORKS ?
Here they are using an open source technology by Google called WebRTC to allow their client (mobile app) to send voice across to our servers.
They have to decide on the codecs however. WebRTC supports a few natively.
WebRTC ?
Codecs ?
What is WebRTC?
WebRTC is an open framework for the web that enables Real Time Communications in the browser.
It includes the fundamental building blocks for high-quality communications on the web, such as network, audio and video components used in voice and video chat applications.
These components, when implemented in a browser, can be accessed through a JavaScript API, enabling developers to easily implement their own RTC web app.
What is CODEC ?
CODEC. A codec, which stands for coder-decoder, converts an audio signal into compressed digital form for transmission and then back into an uncompressed audio signal for replay.
It's the essence of VoIP. It converts each tiny sample into digitized data and compresses it for transmission.
After that they transfer the call to an A-Z termination provider.
VoIP call termination
Is used to refer to the procedures that are used for routing telephone calls from one provider to the next provider until the call has been routed to the last telephone company and has been received by the recipient. Voice termination is another term that is used for call termination. The telephone companies are also referred to as providers or carriers.
A quick google search will give you a list of all such providers.
These guys have direct tie-ups with telephony service providers (Airtel, Vodafone, etc.) and
they subsequently transfer the call to them which is then relayed to the PSTN (Public Switched Telephone Network) by the telephony provider itself using a switch.
So basically the call routes as follows -
Mobile app > their servers (Near by)> Near by A-Z termination provider's servers > Telephony provider's (Airtel/Vodafone) servers > PSTN (traditional phone) network
ADVANTAGE
VoIP technology uses the Internet's packet-switching capabilities to provide phone service.
VoIP has several advantages over circuit switching. F
or example, packet switching allows several telephone calls to occupy the amount of space occupied by only one in a circuit-switched network.
Using PSTN, that 10-minute phone call we talked about earlier consumed 10 full minutes of transmission time at a cost of 128 Kbps.
With VoIP, that same call may have occupied only 3.5 minutes of transmission time at a cost of 64 Kbps, leaving another 64 Kbps free for that 3.5 minutes, plus an additional 128 Kbps for the remaining 6.5 minutes.