VoIP telephony: technology, equipment, programs

In this article we will look at VoIP technology, analyze the main advantages and disadvantages of VoIP telephony, as well as the equipment and programs that are used in VoIP networks.

Over the course of more than a century of development, wired telephony, due to technical and economic obstacles, could not become the universal property of mankind. In developed countries, telephones were installed in all government agencies, commercial firms, in almost every city apartment and rural house, but in our country landline telephone communications, even at the end of the 20th century, remained unattainable for many, not only in remote and sparsely populated areas, but also in large villages. But in order to quickly resolve many private and business issues, people need to be able to communicate by voice “here and now.”

Mobile telephony, which began its expansion about forty years ago, has significantly increased the availability of voice communications, especially in areas not covered by landline communications, and in a short time has become a technology of mass application.

Wired and wireless technologies had settled into their niches and coexisted happily, undisturbed by competitors, just ten years ago, when a third “rival” suddenly appeared - VoIP technology. And this rival turned out to be dangerous, first of all, because it provided the opportunity to pay significantly less for the same minutes of voice communication that could have been spent in the networks of its predecessors. Moreover, it can easily “infiltrate” both landline and mobile zones, communicating with subscribers of both the first and second speech communication technologies. Not to mention “our own contingent on our own VoIP territory.”

VoIP technology: why is it cheaper?

To provide landline telephony services, it was necessary to create an infrastructure in the form of cable communication lines of enormous length. For mobile - build base stations for radio signal transmission. And the Internet became the physical environment for VoIP technology, that is, providers of the new telecommunications direction did not have to create their own infrastructure: there is the Internet - there is the possibility of offering VoIP services, which is reflected in the “name” of the technology - Voice over Internet Protocol - “voice over Internet Protocol” "

The costs of building base stations are returned to the operator in payment for calls on mobile phones. Providers of VoIP technology that were integrated into the “ready-made” Internet network did not incur such expenses for VoIP equipment, and, accordingly, they are not included in the tariffs for communication services.

True, the name VoIP does not fully characterize the technology that allows for the reception and transmission of not only speech (this segment is given the name “IP telephony”), but also video content and, in general, any data presented in digital form. However, since IP telephony is the most in demand today, using its example we will consider all the main technical and economic indicators of VoIP, noting at the same time that this technology, in addition to working on the Internet, can be implemented in any dedicated digital channels that support the Internet protocol and components IP network.

So, the first component of the economics of IP telephony (it would probably be more correct to say “deductible”) is the lack of investment in the creation of infrastructure, which for fixed and mobile operators must pay off, for which they are “invisibly present” in their tariffs.

The second circumstance that allowed IP telephony providers to set a minimum level of payment for their services is that in public telephone networks (PSTN, PSTN), payment for a call is determined by its duration and the length of the dedicated channel. And in IP telephony you only pay for the Internet connection and the volume of transmitted traffic.

The third cost item for landline communication providers, included in the tariffs, as paradoxical as it may sound, is payment for pauses in conversations. The fact is that in traditional circuit-switched networks, payment is calculated for the duration of the “rent” of the channel. And the billing system does not take into account the fact that pauses in a conversation are essentially a waste of time, but simply counts the minutes of “renting” the channel and multiplies them by the tariff. And in IP telephony there is a mechanism for blocking the transmission of pauses (dialogue, syllabic, semantic, spent by the subscriber searching for the right words, distractions from the conversation, etc.), which can account for up to 40-50% of the time the transmission channel is occupied.

VoIP: circuit switching

Current telephone systems are controlled by a very reliable, but somewhat inefficient method for connecting calls called circuit switching. Circuit switching is a very simple concept that has been used in telephone networks for over 100 years. When a call is made between two parties, the connection is maintained for the duration of the call. Because you connect two points in both directions, the connection is called a circuit. This is the basis of the Public Switched Telephone Network (PSTN).

Here's how a regular phone call works:

1. You pick up the phone and listen to the dial tone. This lets you know that you have a connection to your local telephone office.

2. You dial the number of the participant you want to talk to.

3. The call is routed through the switchboard at your local operator to the party you are calling.

4. The connection between the telephone and the other party's line is made using several interconnected switches.

5. The phone on the other end rings and someone answers the call.

6. The connection opens the circuit.

7. You talk for some time and then hang up.

8. When you hang up, the circuit closes, freeing your line and all lines in between.

Phone calls over today's traditional telephone network are somewhat more efficient, and they cost much less. Your voice is digitized and, along with thousands of others, can be combined on a single fiber optic cable. These calls travel at a fixed rate of 64 Kbps in each direction, for a total transfer rate of 128 Kbps. Since there are 8 kilobits in a kilobyte, this translates to an open transfer of 16 KB every second and 960 KB every minute. In a 10-minute conversation, the total transfer is 9,600 KB, which is approximately 10 megabytes. If you look at a typical phone conversation, most of this transferred data is wasted.

VoIP telephony: equipment and programs

VoIP telephony terminals: wired and cordless phones, fax machines, USB, WiFi, soft, IP and video IP phones.

VoIP telephony provides speech transmission and reception between computers (with connected microphones and headphones or speakers), a computer and a landline (analog and digital) telephone, mobile and IP telephones, as well as between any of the listed types of telephones in arbitrary combinations. Note that the analog telephone set we are used to can be converted into an IP telephone by connecting an analog telephone adapter (VoIP ATA) between its input and the Internet outlet.

Each IP phone (with wired and wireless input/output or built-in analog modem) is connected to the Network by an Internet provider, then registered with an IP telephony service operator, receiving a login and password.

But to use this technology, it is not necessary to have a special device if you install a client program on your computer that simulates a phone and connect headphones and a microphone or a USB phone that performs the functions of headphones and a microphone to the PC. Such a computer-software complex is called a softphone (softphone). SoftPhone software can be downloaded for free on the website of your IP telephony provider, and then you can register your device there. The most popular free VoIP telephony program in the world is Skype.

A type of softphone are dual-mode GSM/WiFi (cellular/VoIP) mobile phones, used in two “guises”: in the GSM network they behave like a cell phone, and in the WiFi zone (with SoftPhone software installed in the phone) - in IP -networks Moreover, in the second mode, roaming on the mobile network is practically free.

Videophone – equipment operating using VoIP technology provides the effect of the presence in the office of a subscriber who is “on the other end of the line”, thereby increasing the effectiveness of business negotiations.

To organize voice communication between computers, IP phones and video phones, just connect them with a cable to an Internet outlet and log into the Internet. And to connect an IP network to the PSTN, it is necessary to use analog VoIP gateways FXS or FXO. In the case of ISDN (Integrated Services Digital Network) digital telephone networks, their connection to the World Wide Web is provided by digital VoIP gateways.

VoIP gateways allow you to connect to the networks of several operators to create several traffic routes with minimal tariffs, reserve them for use in case of overloads and failures in fixed and mobile networks. At the same time, thanks to the availability of alternative routes, companies can achieve a significant reduction in costs for communication services, while also increasing the availability of subscribers located in networks that support various voice transmission technologies.

In VoIP gateways, virtual objects can be created that determine the routing of telephone calls, which allows you to connect direct numbers in any country on the planet (this technology is called Direct Inward Dialing, DID).

VoIP gateways are VoIP gateway equipment for transferring voice traffic between traditional telephony networks and data networks.

Another advantage of IP telephony: the ability to simply increase the number of numbers in the office (the so-called “number capacity”), which, as a rule, can be done with great difficulty in the PSTN (and only if the landline operator has the technical capability).

As noted at the beginning of the article, the attractiveness of IP telephony for the mass user lies in the savings in payment for voice communications compared to payment for the same conversations in fixed and mobile networks. This indicator, of course, is also important for the business segment, for which, it turns out, there is another “bonus” - low costs for creating a corporate IP telephony network (hardware IP PBX, software PBX, virtual PBX) based on an existing PBX.

What is IP telephony for the office

Creating a virtual PBX allows you to organize digital IP telephony, which:

will unite employees working remotely into work groups;
will help build connections with clients through numerous text and voice channels;
integrates cloud services for communication and business applications (CRM/BPM/SCM/BI).

It is the optimal solution for enterprises, offices, organizations, thanks to:

accessibility, mobility;
high potential for expanding configurations when introducing new services;
privacy, security;
wide application possibilities - from voice calls, organizing audio conferences to sending text information.

A special case of IP communication is IP-PBX (corporate telephony), based on the VoIP protocol. Unites phones within the office into a single intelligent network that supports voice services. By contacting the provider, the client receives a ready-made virtual PBX with a VoIP server and connected equipment.

Pitfalls of VoIP technology

You have already heard about the advantages and benefits of IP telephony and have even repeatedly seen equipment and programs for VoIP in use by one of your friends. Liked. And so you decide to implement it yourself. But have you been told about a couple of “pitfalls” that can nullify all your expectations? But they exist.

vThe well-known saying that “disadvantages are a continuation of our advantages” can be applied to all technologies without exception. And, of course, to IP telephony. This technology lacks voice quality and security. But these defects can be eliminated if you understand their roots.

So, in PSTN the quality of speech did not cause any complaints because in this technology, based on switching communication channels, the “song flows” continuously in the same “pipe”. And VoIP technology transmits the same “song” in parts (in currently free channels) in accordance with the Internet protocol, switching data packets (as is customary in transmitting any information over the Internet). And if, for example, in the transmission of texts and photographs, this packet sequence can end “when it happens”, and we calmly wait for its end and open the “finished work”, then voice communication works in real time and does not wait for the next packet to arrive .

Therefore, if the delay time in receiving packages and their loss exceed the values established by the standard, this inevitably affects the intelligibility, purity, volume level, the appearance of echoes, wheezing and other sounds that are uncomfortable for auditory perception. But, as the popular cartoon says, “we will survive this trouble.” Naturally, with the help of a system integrator who will be able to carry out all the work for intelligent processing of packet receipt delays, interpolation (partial recovery) of information contained in lost packets, echo cancellation and voice signal level control. And everything will be as good as your friend allowed you to see at his company.

Security is more difficult, because the program of your visit did not include a presentation on this topic. You've probably been told that it's easier to listen to conversations on an IP phone than when using a regular landline phone. And these rumors are not unfounded, since in order to interfere with a conversation taking place over the PSTN, you need a physical connection to the line on which you are having a conversation. And this is quite difficult (although possible).

If you use the services of an IP network, then an experienced hacker can easily “figure out” your IP address and quietly (programmatically) get into your conversations, not only eavesdropping on them, but also blocking and even correcting them! And here, in order not to go into details that are unnecessary for the reader, we can say that specialists in the installation of VoIP technology are able to create an IP network, the level of protection of which will be higher than that of a traditional wired telephone network.

VoIP telephony providers

Since almost all companies have access to the Internet, they have already implemented their corporate networks over IP.

Thus, they are given a first-class opportunity to use the IP network infrastructure, which includes, in addition to communication lines, other equipment such as routers, switches, etc. This IP network infrastructure can be used for telephony as well. Even if an IP telephony system is limited within a business, the benefits are significant.

When a company uses leased circuits to connect to remote branches, using these circuits for both IP telephony and data provides significant benefits and cost savings for the company.

The best and most popular operators include:

Name	Description	Price, cheapest tariff	Rating
Zadarma	This operator has been working in the field for more than 14 years. He cooperates with both individuals and corporate clients.	240 rub.	★★★★★
Mango Office	This is a cloud telephony that allows you to organize sales and customer service for businesses of any size. Multi-channel city numbers, 8-800, numbers for advertising, voice menu and other services.	350 rub.	★★★★★
VOTBOX	Cloud PBX and IP telephony service with calls starting from 0.75 rubles per minute. Subscribers of the same account can communicate for free. Telephony connection is also free.	330 rub.	★★★★★

What are the VoIP protocols:

The protocols ensure registration of an IP device on the server or gatekeeper of the provider, calling and/or call forwarding, establishing a voice or video connection, transferring the name and/or number of the subscriber. Currently, the following VoIP protocols are widely used:

SIP
H.323
IAX2
MGCP (Media Gateway Control Protocol)
Megaco/H.248
SIGTRAN
SCTP (Stream Control Transmission Protocol)
SGCP
SCCP (Skinny Call Control Protocol)
Unistim

VoIP: Packet Switching

Packet switched telephone network is an alternative to circuit switching. The way it works is that while you're talking, the other side is listening, meaning that only half of the connection is in use at any given time. Based on this, we can assume that we could cut the file in half, down to 4.7 MB, to improve efficiency. Additionally, a significant portion of most conversations are dead air—several seconds without either party speaking. If we could remove these quiet intervals, the file would be even smaller.

Data networks do not use circuit switching. Your Internet connection would be much slower if it maintained a constant connection to the web page you were viewing at any given time. Instead, data networks simply send and retrieve data as needed. And instead of routing data along a dedicated line, data packets travel through a chaotic network along thousands of possible paths. This is called packet switching.

While circuit switching keeps the connection open and persistent, packet switching opens a short connection—long enough to send a small piece of data, called a packet, from one system to another. It works like this:

The sending computer discards the data into small packets, each with an address that tells network devices where to send it.
Inside each package there is a payload. The payload is a piece of email, a music file, or any other type of file that is transferred within a packet.
The sending computer sends the packet to the nearest router and forgets about it. The closest router sends the packet to another router that is closer to the receiving computer. This router sends the packet to another, even closer router, and so on.
When the receiving computer finally receives the packets, it uses the instructions contained in the packets to reassemble the data.

Packet switching is very efficient. It allows the network to route packets over the least congested and cheapest lines. It also frees up two computers communicating with each other so that they can receive information from other computers.

VoIP Gateway Features

In addition to its main function - encoding and decoding voice when transmitted via the IP protocol - the VoIP gateway has all the usual options that regular mobile and city operators have. These options increase the performance of processing incoming calls and improve the quality of telephony services:

holding an incoming call;
call forwarding;
automatic call back;
Caller ID (automatic number identification);
conference call

Using a voice IP gateway, you can make and receive calls over the Internet from regular mobile and landline phones. You don't even need to have a computer to use it.

You can reduce costs - virtual PBX

The cost of a digital PBX for a company starts from 50 thousand rubles, depending on the functionality. IP-PBX cards are somewhat cheaper, but there is a way to save even more - use the services of a virtual PBX. A typical example of this is the virtual PBX from the IP provider Zadarma. Its advantages:

Does not require the purchase of equipment - an Internet channel with workstations connected to it is enough;
Free connection - no multi-thousand bills;
Subscription fee – from 0 rubles, depending on the selected tariff plan;
Free communication within the company;
Any functions of traditional office PBXs - from call recording to analytics;
Possibility of connecting multi-channel numbers in 90 countries;
Free CRM integration and much more.

A virtual PBX eliminates the need to purchase equipment - you just need to configure applications or IP phones at your workplaces. Regional and international branches are connected in a similar way - they can be located anywhere in the world. Need to move? No problem - rent a new office, install internet there and connect workstations. The equipment will automatically connect to the virtual PBX and start working. If necessary, the number of jobs can be expanded in a matter of seconds - just create a new account in the management system.

How to choose a VoIP gateway

The cost of voice gateways on the market has recently decreased significantly, so this method of connecting to IP telephony is considered one of the most budget-friendly. But the price largely depends on the various characteristics of the gateways.

To choose the voice gateway that can best solve your problems, pay attention to the following operating conditions:

Compatible with other VoIP equipment. When purchasing a gateway, you need to find out from the manufacturer which stations it works with.
Gateway DSP processor. It is responsible for voice quality, the absence of echo and extraneous noise.
In order for the voice gateway to serve for a long time and not unexpectedly fail due to overheating, you need to find out all the requirements for its installation and study what cooling system is installed by the manufacturer and whether it will work well.
There are simple voice gateways that are used to connect only one telephone set. And to simultaneously transmit multiple conversations to the network, multi-channel gateways will be required.

Also pay attention to the additional functionality of gateways. Using various services will help build an effective communication network in the company.

Connect IP telephony

Content:

This is a technology with which Internet users make calls over the network. With the development of broadband communications, it has become especially popular. In general, people like to use VoIP. Why? The technology offers much more options than analog phones. All this can be done at almost two – and sometimes more – times cheaper.

In addition, cloud telephony providers include powerful features in their plans that are not included in standard offerings. For example, an auto attendant, call recordings, transcribing voice mail to email, etc. VoIP allows you to receive calls from anywhere in the world where there is Internet. But let's not get ahead of ourselves.

In this article, we will tell you everything you need to know about VoIP technology.

How does a voice gateway work?

A standard VoIP gateway is a device that connects to the telephone network. The main task of a voice gateway is to record and convert human speech into a digital code that will be transmitted to the recipient.

The human voice is encoded using pulse code modulation. At the input, speech sounds are converted into a digital signal, which is fragmented into individual packets and transmitted via the IP protocol. At the receiving end, the received packets undergo a decoding procedure and are converted into synthesized speech. You can transmit a voice signal to any device - a browser or another computer program such as Skype, as well as to mobile and landline phones.

Many models of voice gateways, in addition to voice transmission, are capable of performing many other functions: routing, managing transmitted traffic, and analyzing it.

Optimizing the signal transmission process

During the signal transmission process, there is a slight difference between the moment the voice sounds at one end of the “wire” and the signal is converted into synthesized speech at the other. On average, the delay is about 10–45 milliseconds.

Question:

What causes delay in data transfer?

Answer:

This slight delay in sending packet data is due to the operation of the signal accumulation buffer, as well as computational and algorithmic delays. In rare cases, distortion of synthesized speech occurs during the decoding process, caused by the loss of some codecs, as well as by exceeding the signal transmission time. Modern providers use various speech compression algorithms to improve the quality of data transmission and eliminate technical shortcomings.

Packaging and subsequent signal transmission via the IP protocol also has different algorithms. Some packets remain almost at the original level and are transmitted at a speed of 64 Kb/s. Other algorithms allow you to compress the speech signal up to 8 times or more, which improves the quality of telephone communications.

Ways to improve communication quality

The data transfer process becomes more efficient due to other assistive technologies. For example, blocking the transmission of pauses, which saves network time when semantic and dialogue pauses occur during conversations. They can account for up to 50% of the airtime, and the voice gateway passes them through to optimize telephony communications.

Most providers use statistical data to evaluate the quality of data transfers and use them to optimize communications. For example, ASR/ABR is statistical data that determines the quality of communication through a specific IP telephony switch. ACD is another quantitative indicator that indicates the percentage of completed calls that lasted more than 30 seconds to the total number of incoming calls. Based on these figures, the provider evaluates the dynamics of changes in communication quality and makes changes to improve it.