11-05-2013, 02:28 PM
Voice over Wi-Fi
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INTRODUCTION
The advances of VoIP and Internet telephony in general have come a long way since their inception. Most recently, the "next big thing" has been to merge Wi-Fi with VoIP, producing one of the oddest acronyms you'll ever see. VoWiFi, or Voice over Wireless Fidelity, simply means a Wi-Fi based VoIP service — or in even more general terms, a wireless based VoIP system.
Where VoIP consists of the hardware and software that enables people to use the Internet as the transmission medium for telephone calls, VoWiFi is the wireless version of this technology that is designed to work on wireless devices such as a laptop or PDA. Some may wonder why a person or organization wouldn't simply use a cell phone for mobile communications, but again business and organizations can take advantage of a decreased communications cost while having a mobile system that offers more reliable coverage indoors and higher voice quality than traditional cellular service with VoWiFi.
Along with added benefits to business and those with a need for wireless communications, VoWiFi also opens up the door for a whole new market of consumer products such as a standalone VoWiFi handheld. Many cellular phone companies such as Nokia and Motorola have already announced dual-mode cellular phones that will support seamless roaming from WiFi to cellular networks when WiFi is unavailable to a caller. That is one of the biggest challenges facing VoWiFi — roaming access. A WiFi access point offers a communication range of up to 90 meters (commonly called a hotspot), and continuous conversations would mean that the caller must stay within an area of overlapping hotspots, or as already suggested, have a VoWiFi dual-mode phone that would switch to a regular cellular phone transmission when the caller moves out of a hot spot range.
WIRELESS FIDELITY (WiFi)
Wi-Fi, which stands for wireless fidelity, in a play on the older term Hi-Fi, is a wireless networking technology used across the globe. Wi-Fi refers to any system that uses the 802.11 standard, which was developed by the Institute of Electrical and Electronics Engineers (IEEE) and released in 1997.It provides secure, reliable, fast wireless connectivity. Wi-Fi is the trademark of the Wi-Fi Alliance, the trade organization that defines the Wi-Fi standards.
It refers to a local area network which uses high frequency radio signals to send and receive data over short distances (approx. 200 feet). It can connect computers anywhere in home or office without the need for wires. It is also known as 802.11 networking and wireless networking.
Hot spots are areas with Wi-Fi service and are either accessed for free or for a fee. It is possible to purchase access using a metered system or passes good for a certain time frame, such as day, week or month. There may be metered access or with a pass for, for example, a day, month or year. Access can be for a complete chain of locations or just one hot spot. Hot spots can be in bookstores, cafes or airports.
In a Wi-Fi network, computers with wifi network cards connect wirelessly to a wireless router. The router is connected to the Internet by means of a modem, typically a cable or DSL modem. Any user within 200 feet or so (about 61 meters) of the access point can then connect to the Internet, though for good transfer rates, distances of 100 feet (30.5 meters) or less are more common. Retailers also sell wireless signal boosters that extend the range of a wireless network.
Wi-Fi network s operate in the unlicensed 2.4 and 5 GHz radio bands, with an 11Mbps (802.11b) or 54 Mbps (802.11a) data rate or with products that contain both bands.
Interference
Interference is an issue with any form of radio communication, and a wireless network is no exception. The potential for interference is especially great indoors, where different types of building materials (concrete, wood, drywall, metal, glass and so on) can absorb or reflect radio waves, affecting the strength and consistency of a wireless network's signal. Similarly, devices like microwave ovens and some cordless phones can cause interference because they operate in the same 2.4 frequency range as 802.11b/g/n networks. You can't avoid interference entirely, but in most cases it's not significant enough to affect the usability of the network. When it does, you can usually minimize the interference by relocating wireless networking hardware or using specialized antennas.
Data Security
In the same way that all you need to pick up a local radio station is a radio, all anyone needs to detect a wireless network within nearby range is a wireless-equipped computer. There's no way to selectively hide the presence of your network from strangers, but you can prevent unauthorized people from connecting to it, and you can protect the data traveling across the network from prying eyes. By turning on a wireless network's encryption feature, you can scramble the data and control access to the network.
Wireless network hardware supports several standard encryption schemes, but the most common are Wired Equivalent Privacy (WEP), Wi-Fi Protected Access (WPA), and Wi-Fi Protected Access 2 (WPA2). WEP is the oldest and least secure method and should be avoided. WPA and WPA2 are good choices, but provide better protection when you use longer and more complex passwords (all devices on a wireless network must use the same kind of encryption and be configured with the same password).
VOICE OVER IP (VOIP)
The advances of VoIP and Internet telephony in general have come a long way since their inception. VOIP in simple terms is the process of breaking up audio or video into small chunks, transmitting those chunks over an IP network, and reassembling those chunks at the far end so that two people can communicate using audio and video, instead of the plain old telephone system (POTS).
The basic principle of Voip is very simple. It's the same technology you have probably used already to listen to music over the Internet. Voice sounds are picked up by a microphone and digitized by the sound card. The sounds are then converted to a compressed form, compact enough to be sent in real time over the Internet, using a software driver called a codec. The term codec is short for "encoder/decoder". The sounds are encoded at the sending end, sent over the Internet and then decoded at the receiving end, where they are played back over the speakers. The only requirements are a connection between the two computers of an adequate speed, and matching codecs at each end.
To be usable, a Voip system also needs a method for establishing and managing a connection, for example, calling the other computer, finding out if they accept the call, and closing the connection when a user hangs up. Because Voip allows two way communication, and even conference calls, it's a lot more complicated than simple audio streaming. How calls are managed is the area in which Voip systems fundamentally differ, and two Voip users must be using the same system (or compatible ones) in order to be able to call each other.
VOICE OVER WI-FI (VOWiFi)
Wireless and VoIP have joined forces. Installing a WLAN network card into your computer uses wireless technology. After installing the card, your computer will become “wireless”. This means that you will be able to enjoy an Internet connection without the use of cables and cords.
VoIP is the technology that allows the transmission of audio files by transmitting them into data packets across the Internet. By integrating Wireless and VoIP a new generation of audio telecommunications has been birthed. By having a VoIP service and a wireless connection, you can enjoy the best of both worlds- wireless VoIP connections.
Wireless networks are activated by what is known as a “hotspot”. A hotspot is an area where there is an access point. Wireless connections are basically created by radio signals. An access point is where the network has established their main signal. It is possible for wireless users to basically “jump” from hotspot to hotspot and utilize various networks access points.
The combination of Wireless and VoIP has led to the invention - VoWiFi technology. VoWiFi stands for Voice over Wireless Fidelity. VoWiFi has also produced the new VoWiFi phones. These phones operate like cell phones, only they use VoIP technology, (transmit over the Internet) and are wireless, operating in various hotspots.
VoWiFi phones are very inexpensive to use, as is all of VoIP technology. It is much cheaper to submit audio as data packets over the Internet and it uses considerably less bandwidth. This is a reason why VoIP technology is gaining in strength and momentum.
Many people are choosing the freedom that is offered by VoIP. VoIP can offer nearly free or free long distance phone calls. Since VoWi-Fi operates from hotspot to hotspot or network-to-network, you may think that there are roaming charges involved. There are no roaming charges involved with VoIP. That’s right, you can take your VoWiFi phone from hotspot to hotspot, maintaining your connection (provided you easily go from hotspot to hotspot) absolutely free.
WHY VOWi-Fi CELL PHONES ?
Mobile VoWiFi phones support VoIP or VoIM services, but not both. Some connect to hotspots automatically, others require manual configuration. (Manual configuration is more secure.) And most incorporate some form of Wi-Fi security.
You may be wondering why not just use cellular? Why go wireless? Well, for those who travel a lot or are consistently out of their cellular range, roaming charges will apply and can be expensive. By using your VoWiFi in hotspots while you are traveling, you can pick up a connection and make your calls for free.
Be careful not to confuse a VoWiFi phone with a cordless VoIP phone. They are two distinctively different products. A VoWiFi phone will enable you to access hotspots, but a cordless VoIP phone is simply a way to have a cordless phone in your house that is compatible with your VoIP service provider.
An interesting trend is the creation of the hybrid phone. If someone is a traveling salesman, or just simply travels frequently and is on their cell phone, then leave their network range- they can take advantage of the new hybrid phone. The hybrid phone, which is part cellular, part VoWiFi, will be able to access hotspots, and pick up a signal. - no more roaming charges!
Wireless VoIP does show promising signs towards the future and many look anxiously awaiting new products and increasing performance by these products. You will have to have a VoIP service provider before you can access VoWiFi. However, you can still find many free hotspots that will give your phone a connection.
VOWIFI AND QUALITY OF SERVICES
Wi-Fi networks are inherently a shared medium, in which all users accessing the network have equal access to the available bandwidth. As the proliferation of WiFi-enabled devices continues, more and more end-points are vying for this increasingly limited resource. For many services using WiFi as a communications network, periodic delays in receiving or transferring data result in no perceptible problems. However, the real-time nature of voice communications makes the delays or interruptions that can occur in congested WiFi networks less acceptable.
With the initial 802.11 specifications, there were no direct provisions for quality of service; the protocols were designed to provide fair and equal access to all devices accessing the medium. However, as WiFi has grown and applications for it broadened, the need for a level of inherent QoS has become apparent. The industry has responded to this need through the development of the 802.11e specification, of which the primary goal is to define QoS for WiFi networks. One of the primary characteristics designed into the 802.11e specification is the use of "classes of priority" for various types of traffic.