Traditional phone to ToIP gateways

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Traditional phone to VoIP gateways are a sort of communication service, which permits a classic phone subscriber (landline, cellular or satellite) to communicate at a local price to a Voice over IP (or Telephony over IP) user, who doesn't have a classic phone number.

However, with the democratisation of internet access, and especially due to the large market share of communication apps in the 2000s on computers, and years later on mobile devices, these solutions are generally unknown to the large public.

History

This type of system benefited from the arrival of the Telephony Over IP protocols, such as SIP for VoIP, or Jingle for XMPP protocol. It permits internet users to communicate for free and unlimited, generally through independent and low-cost phone providers, whereas outgoing calls to PSTN are charged.

It's similar to Skype, where only from internet to internet calls are free of charge. However, calls to the PSTN are always charged, but at a different price. And Skype or others, such as Whatsapp (lately), require both correspondents to use the same software, whereas SIP or XMPP users can choose different client-software, and even communicate with other providers' subscribers.

SIPBroker (SIP protocol)

It's the oldest one still in service. Started in 2005, managed by an Australian consultant, it still processes about hundreds of calls every year. This service is financially maintained by various providers of Voice over IP, who are not big phone providers with consequent infrastructures, but small or medium businesses retailing time of call. Their customers are mainly individuals, small and medium organisations.. They have a certain success with a small range of customers, but bring to them, for free, several gateways to SIPBroker, free to call all over the world. These small providers are mainly DIDWW, voip.ms, callcentric and several others.

Functionning

A PSTN to SIP gateway is a computing server, accessible from the common phone network. A public landline phone number has been attributed to it. For example, +34-97-157-99-12, located in Spain, allows reaching a VoIP user located everywhere in the world. However, some attention has to be paid to the latency.

When the communication to the gateway, using a traditional phone number, is established, the caller must compose the asterisk (or star, *) on the keyboard, then the network (VoIP provider) number, then the VoIP user number. A VoIP number is also called an alias or DID.

Example, to illustrate :

Alice gets a VoIP number, 9839, from her voip.ms provider, which is the 228 network number. Thus, when the communication starts, the robot's voice, Bob will have to enter *2289839 on his phone's keyboard. Until processed in a few seconds by the gateway, if Alice's phone is connected, her phone will ring.

The network number, depending on the VoIP provider, can be obtained on the SIPBroker website.

Steps :

1. Firstly, the phone number of the most adapted gateway (e.g. the country) might be composed on the phone. Those gateways can be found on the sipbroker website.
2. When the robot starts its voice, enter the star/asterisk *, then the VoIP service's network number. It can be found too, on the sipbroker website.
3. If the VoIP user is online, the phone will ring.

In addition to being reachable via the PSTN-to-SIP gateways, Alice, at a specific VoIP provider (e.g. voip.ms), can be reached from other providers, such as callcentric, DIDWW, etc., for free and unlimited, e.g. like Skype, but using any type of SIP-client. So Alice ('at\) first . org could communicate unlimited and for free with Bob ("at\) last . net, because SIP protocol is interoperable.

Advantages :

• These communications are generally unlimited and toll-free by VoIP brokers
• These pstn-to-sip gateways are present in many countries (about half of the world, where North America has a lot)
• It doesn't require the caller to have a smartphone or even a mobile phone; it will even work on a landline.

Disadvantages :

• Like any call on the PSTN (traditional phone), it can be tapped.
• Some gateways have a maximum capacity of simultaneous calls.
• Less than half of countries in the world have a gateway; In Asia, only Japan has one. But generally, countries all over the world have providers that permit free calls to border countries.
• Some rare providers in the world toll (meaning apply fees) the calls to this type of service. This is not due to the VoIP providers, but because their commercial rates apply fees to any call not going to mobiles or landlines.
• This type of service could be considered obsolete, mainly due to the mass adoption of smartphones in the world. Also, some countries don't charge fees for calling to borders or other countries' landlines. However, not all providers, all over the world, accept incoming calls to landlines for free, e.g. Switzerland mainly applies fees to calls to any number, even landlines.

JMP.chat (XMPP protocol):

At the end of the 2010s, the massive adoption of mobile apps, especially Whatsapp, was a bit shaken by contract modifications. As a result of this, millions of users decided either to leave or delete Whatsapp, or to add another one, or just move to another service. Some other types of communications, started a few years ago, started to gather amounts of new users, such as Matrix protocol, but also XMPP. This last one, created at the end of the 90s, supports VoIP since 2005, and is now ready to compete with bigger apps. For example, Monal on iOS, Conversations or Quicksy for Android/AOSP, Dino for Windows/Linux/BSD/Macos, which supports Voice over IP and Videoconference for years. A new type of operator based on XMPP is starting: JMP.chat.

JMP permits registering and redirecting a North-American phone number (+1 prefix) to a specific xmpp address. The subscription is cheap and benefits from the popularity of smartphones; however, it's possible to connect to JMP.chat from any xmpp-compatible device (computer, tablet..). This service is provided by the non-profit Canadian association of Soprani, to promote only-internet based communications with interoperability and standards used. In addition, JMB permits its subscribers, and xmpp users in general, to be reached via the SIPBroker network, but the process is not convenient; the xmpp address has to be converted into a numbers-only chain, which can take too much time to be typed at the robot's voice, resulting in a timeout effect.

iNum (SIP protocol)

At the end of the 2000s, several actors started the iNum standard, in case a virtual phone number starting with +882 and +883 prefixes, to permit internet users everywhere in the world to be called for free. But even with that initiative, firstly the traditional network operators weren't playing fair game, charging those communications (from traditional (pstn) to iNum users) at a higher price, such as satellite communication, to discourage this practice. The massive adoption of internet-mobile applications, such as Whatsapp, Signal, Telegram, iMessage and RCS commercial-based alternatives, definitely stopped the maintain of the service. Thus, the iNum service was shut down a decade later.

That service was provided by Voxbone, available through few retailers such as Ippi, who provided free iNum numbers to its users, even without paying, and was standardised by ITU.

Tricks :

Uses for non-VoLTE compatible devices

A trick not well known consists of using the PSTN to SIP gateways to bypass the lack of software support of Voice over LTE for non-compatible devices. The trick consists of using the alias provided by the VoIP service to register it into the phone through SIP-software client app. Thus, calling from PSTN to the VoIP number will make Voice over LTE possible. However, this system is totally independent of the cellular service; it will not magically enable VoLTE, but enable a different number, permitting communications to VoIP users through gateways to be reached from the common phone network. It's mainly used in case of absence of 2G coverage, 3G coverage, or just to permit calls on non-VoLTE devices still using 4G service.

Uses as VoWifi device

The same trick could be used as a sort of VoWifi call, requiring being connected and close to a Wifi AP. It permits reusing non-VoLTE or non-VoWifi compatible phones as a device to receive calls, or do directly through the internet.

Observations

Some engineers believe that both SIP and XMPP protocols are for messaging, voice and video over IP, what email is for, especially because they work on the same scheme.

It's interoperable, decentralized, as it's possible to send email from "first . org" domain to "second . net" one, meaning between different service providers, contrary to popular messaging apps, which require having the app for each participant and being connected to a unique service provider.

It's the same functioning for XMPP and SIP, as messaging, voice and video communications. The only case is if a service provider isn't compatible with a feature, which is rare. Mainly, they all accept voice, video features, and file sharing or encryption features. In addition, these services are "domain-opened", meaning that providers' users can communicate with each other, but it appears some VoIP operators are still domain-closed for specific reasons, or bill all calls, even to direct internet users, but it's rare. In addition, even if VoLTE and VoWifi work with SIP protocol to carry Telephony, they will never accept being called from direct VoIP communication, requiring incoming calls coming from the traditional phone network, not internet users.

References

This article "Traditional phone to ToIP gateways" is from Wikipedia. The list of its authors can be seen in its historical and/or the page Edithistory:Traditional phone to ToIP gateways. Articles copied from Draft Namespace on Wikipedia could be seen on the Draft Namespace of Wikipedia and not main one.

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