Monday, June 27, 2011

VoIP Voice-Over-Internet Protocol

Voice-Over-Internet Protocol (VoIP)

VoIP (Voice-Over-Internet Protocol) - also known as Internet Protocol telephony (IP telephony) - is becoming a key driver in the evolution of voice communications.

Voice Over Internet Protocol (VoIP) is a telephony technology used to transmit ordinary telephone calls over the Internet. VoIP takes analogue audio signals and turns them into digital signals (packets) that are transmitted using Internet Protocol (IP) networks. VoIP's advantages include low cost, flexibility, and mobility. Conversely, VoIP's disadvantages include sound quality such as latency (delay), jitter, and packet loss. VoIP has a number of cultural, social, and regulatory impacts that solution providers must consider when marketing their services.

VoIP is a relatively new technology useful not only for phones but also as a broad application platform that enables voice interactions on devices such as desktop computers, mobile devices, set-top boxes, gateways, and many devices with applications specific to certain businesses where voice communication is an important feature.

VoIP - Technology Overview

VoIP is a new form of communication that takes analogue audio signals and turns them into digital signals, or packets. This is an innovative alternate to the traditional circuit-switched method of telecommunication, where a dedicated circuit between two parties is maintained. In order to set up a traditional phone call between two telephones, the switched and the intervening network establish a dedicated route from one end of the call to the other. Conversely, VoIP uses a packet-switched method where audio signals are converted into digital data at the originating end, which is then transmitted over the Internet and converted back to analog signal at the receiving end. In other words, VoIP digitizes voice, inserts the digitized data into discrete packets, and sends them over the IP network. The packets have a destination address, but no fixed path through the network. The packets arrive at the address, where they are put back together and converted back to analog audio signals. VoIP integrates voice and data communications and turns any Internet connection into a phone call. VoIP is a revolutionary technology that has the potential to drastically change the way people communicate and talk on the phone around the world.

Advantages of VoIP

VoIP has a number of advantages. First, the major advantage is related to cost. VoIP has tremendous savings potential for anyone who communicates over long distance. For instance in a corporate environment, the cost for leased lines no longer exist if phone calls are transmitted over the Internet. In addition, if an employee moved to a different location within the same office using a regular phone system like the Public Switched Telephone Network (PSTN), fees would be incurred in that move. To make such a move with a VoIP system, however, employees would only need to plug their IP phones into their office's Ethernet jack, with no extra cost. A digital private branch exchange (PBX)1 system already provides for the integration of traditional telephone services and thereby eliminates the aforementioned costs of moving. Secondly, flexibility and mobility are also utilized with the adoption of VoIP. Individuals can simply plug in their laptops, access the Internet, and talk on the phone, potentially improving organizational communication and customer service. In terms of customer service, VoIP has some advantages. Using VoIP's capabilities with different enterprise software, when a customer calls they can be routed easily to whom they want to talk, and the service representative will have easy access to pertinent information that will improve customer service.

Disadvantages of VoIP

VoIP also has its share of disadvantages when compared to the functionality of PSTN. A major disadvantage of VoIP is that it is a new technology. As a result, the long-term benefits and risks are not yet known. These risks include unknown service life of hardware and infrastructure, and details surrounding reliability and quality. The factors that affect the sound quality during transmission include latency (or delay), jitter, and packet loss.2 In terms of latency, human ears can withstand a delay of 150-250 ms and not be able to notice the delay. The PSTN meets this standard with a nominal delay of 150; however, VoIP cannot meet this standard of delay for a consistent period of time.3 Jitter is defined as the variability in packet arrival at the destination.4 Voice packets are transmitted over the same IP network as normal data packets and therefore voice packets have to compete for bandwidth with data packets. When a situation arises whereby there is a burst of network traffic (mostly in the form of data packets) voice packets arrive at sporadic times to the destination. The consequence of sporadic arrival time of the packets is sound distortion at the receiver's end - jitter. Lastly, the issue of packet loss occurs when voice packets that are transmitted over the network do not arrive at the destination. Along the same lines as the causes of jitter, the IP network is to blame for this drawback because it does not guarantee delivery of any packets (data or voice). The consequence of packet loss is distortion at the receivers end as sounds and words may actually never reach the receiver.

With regards to availability, VoIP must meet the "five nines" availability demanded of phone services (i.e. VoIP must be available at least 99.999% of the time). A common misconception is that VoIP will have lower dependability and availability than standard PSTN systems because of power failures, internet service provider "down-time", security issues, etc. Nevertheless, it is has been demonstrated that it is possible to build VoIP systems that are more reliable than circuit based PSTN platforms. Adaptive routing ensures that packets reach their designation using multiple network lines.

Overall, the disadvantages of VoIP are not significant enough to hamper its ability to compete with traditional PSTN. In addition, advances are being made for the technology to get over some of these stumbling blocks. For example, the problem of jitter has been shown to decrease by using specialized gateways that determine whether large network data bursts are currently affecting throughput and the gateway adjusts to decrease jitter. The technology has matured to a state where major players are now offering VoIP solutions as alternatives to traditional telecommunication solutions.

Mobile VoIP

Even when restricted to wired computer networks, VoIP introduces mobility as provided by 'mobile IP'. A 'home agent' serving your home network could be informed where you are and request, at call set-up time, that voice streams be sent to and be received from your temporary IP address or a 'foreign agent' serving your interests.

Mobile VoIP has also come to mean the application of VoIP technology and protocols to battery powered wireless enabled mobile devices including handsets. Most commonly this means VoIP over WiFi referred to sometimes as VoWiFi or VoWLAN. Since IEEE802.11 WLANs provide physical and data link layers suitable for supporting IP and the transport layer protocols UDP and TCP, it may be considered that there is no particular problem in supporting VoWiFi. Indeed many people now routinely use VoIP services provided by Skype, MSN and others over WiFi links at home and in the office. The same H323 or SIP protocols as would be used on a desk-top computer must clearly be expected to work on WiFi connected devices.

VoIP and the Future of Satellite Communications

You may remember a few years ago when everyone first started talking seriously about voice over IP (VoIP). Several companies claimed that the world was in for another technological revolution and that paradigms were going to start shifting dramatically. Now, that market is finally beginning to materialize, and VoIP is poised, once again, to take the communications world by storm.

AT&T plans to make available a consumer VoIP offering for customers in the top 100 markets during the first quarter of 2004, and Verizon has similar VoIP plans for the second quarter. Vonage already has been delivering consumer and business VoIP services successfully and continues to gain subscribers on a regular basis. In the satellite communications industry, VoIP has been quietly but widely available in some format for the past two years.

For the remote ocean communications sector of the satellite communications industry, the news about VoIP and IP communication has traveled slowly. Most ship-to-ship and ship-to-shore (or remote rig-to-shore) communication has operated unchanged for several years. That’s not all that surprising. For workers focused on drilling efficiencies, manual labor or machinery maintenance, communications services always have been a secondary concern. But the Internet and data transmission have become much more important in recent years. And workers require better communications for business and personal reasons.

Offshore workers need to transmit real time operating data to the central office on the mainland, participate in video conferences, dial-in to make reports during important meetings, read stories from the online version of the hometown newspaper, see the digital photos of baby’s first birthday celebration, and make sure they don’t get sniped at the last minute during eBay auctions. For those reasons and many others, traditional remote satellite communications have finally come under pressure to catch up with the wired world.

Frame relay is the current legacy network for people in the drilling world, but it doesn’t offer the flexibility companies have come to expect from their mainland communications. IP via satellite not only provides that flexibility, but also, it offers a boost in reliability. IP is more successful at re-delivering corrupted transmissions than frame relay. The new IP networks use Ethernet to create a virtual private network (VPN) that operates with multi-protocol label switching (MPLS) over satellite. MPLS combines the connection-oriented privacy and quality of service of traditional frame relay or ATM networks with the simple and efficient connectivity of IP.

Remote provisioning is one of the most exciting elements of IP communication via satellite. Services and applications can be added and/or subtracted with ease. For the customer/end user, there’s an element of future-proofing with a network that can be provisioned centrally from a network operations center (NOC). The end user isn’t forced to constantly purchase new equipment or new software applications. All of the new services, in addition to any moves/adds/changes, are provisioned from the NOC. This creates dramatic cost savings and a pleasant reduction in hassle for everyone involved. On land, such efficiencies eliminate truck roll – but on water, the truck roll (which really involves helicopters and boats) is far more costly. Remote provisioning takes care of that issue.

All satellite communications providers do not offer these advanced features, but virtually every offshore provider is offering some form of IP communications. Even so, experts in the industry believe it could be several years before IP becomes the de facto standard for offshore communications. In the meantime, those companies interested in IP via satellite are encouraged to research the technology and look for providers with a strong track record of reliability and technological innovation.


1. Voice Over Internet Protocol (VoIP) – "Crossing the Chasm";
2. Comp60242: Mobile Computing '10, B3.VoIP & VoWLAN;
3. VoIP and the Future of Satellite Communications By Errol Olivier.