VOICE OVER WiFi by Narendranath Kanukolanu Rahul Datta Kalyan Valluri
TOPICS • 1. Introduction • What is WiFi • What is voice over WiFi • What is voice over IP • 2.Features • 3.Architecture of Voice over WiFi • 4.Future prospects • 5. Conclusion
WHAT IS WiFi(wireless fidelity) • WiFi is the wireless way to handle networking. • It is also known as 802.11 networking and wireless networking. • The big advantage of WiFi is its Simplicity. • Can connect computers anywhere in home or office without the need for wires. • The computers connect to the network using radio signals.
Contd… • Wireless Fidelity is meant to be used generically when referring of any type of 802.11 network, whether 802.11,802.11a, 802.11b, 802.11g dual-band, etc. The term is promulgated by the Wi-FiAlliance. • WiFi Alliance An organization made up of leading wireless equipment and software providers.
Over view of IEEE 802.11? • Wireless networking hardware requires the use of underlying technology that deals with radio frequencies as well as data transmission. • The most widely used standard is 802.11 produced by the Institute of Electrical and Electronic Engineers (IEEE). This is a standard defining all aspects of Radio Frequency Wireless Networking.
Specifications in the 802.11 family • 802.11 Applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band using either Frequency Hopping Spread Spectrum(FHSS) or Direct Sequence Spread Spectrum (DSSS). • 802.11a An extension to 802.11 that applies to Wireless LANs and provides up to 54 Mbps in the 5GHz band. 802.11a uses an Orthogonal Frequency Division Multiplexing encoding scheme rather than FHSS or DSSS. H
Contd.. • 802.11b (also referred to as 802.11 High Rate or Wi-Fi) An extension to 802.11 that applies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1 Mbps) in the 2.4 GHz band. • 802.11g Applies to wireless LANs and provides 20+ Mbps in the 2.4 GHz band.
An 802.11 WLAN History • 1940: Spread spectrum technology first used by the military • 1980: Limited applications using narrowband technology • 1989: FCC assigns frequency for commercial use. ISM bands authorized (900 MHz, 2.4 GHz, 5 GHz) • 1990: *900 MHz products begin shipping *IEEE begins work on industry standard • 1994: 2.4 GHz products begin shipping • 1997: *IEEE 802.11 standard approved. *2.4 GHz products begin dominating the scene • 1999: *IEEE 802.11a&b supplements ratified. *WECA formed for interoperability testing *Wide Band Frequency Hopping NPRM Released by FCC “Enhanced MAC - QoS and Security” Task Group chartered • 2001 QoS/Security draft standard formulated • 2002 Has over 130 participating companies with voting members
Technology that makes WiFi networking possible The Walkie Talkie Network These are small radios that can transmit and receive radio signals. When you talk into a Walkie-Talkie, your voice is picked up by a microphone, encoded onto a Radio frequency and transmitted with the antenna. Another walkie-talkie can receive the transmission with its antenna, decode your voice from the radio signal and drive a speaker.
WiFi's Radio Technology • WiFi radios that work with the 802.11b and 802.11g standards transmit at 2.4 GHz. • while those that comply with the 802.11a standard transmit at 5 GHz. • WiFi radios use efficient coding techniques that also contribute to the much higher data rates. • For 802.11a and 802.11g, the technique is known as Orthogonal Frequency-Division Multiplexing (OFDM). For 802.11b, it is called Complementary Code Keying (CCK).
WifiSECURITY • WiFi hotspots can be open or secure. If a hotspot is open, then anyone with a WiFi card can access the hotspot. If it is secure, then the user needs to know a WEP key to connect. • WEP stands for Wired Equivalent Privacy.
Hardware needed to create WiFi Network • One of the best things about WiFi is how simple it is. • 802.11a, 802.11b or 802.11g network card. 802.11g has the advantage of higher speeds and good interoperability on 802.11b equipment. • For a laptop, this card will normally be a PCMCIA card that you slide into a PCMCIA slot on your laptop. Or you can buy a small external adapter and plug it into a USB port. • For a desktop machine, you can buy a PCI card that you install inside the machine, or a small external adapter that you connect to the computer with a USB cable. • Install the card • Install the drivers for the card • Find an 802.11 hotspot • Access the hotspot. (A hotspot is a connection point for a WiFi network)
VoIP(Voice over Internet Protocol) • A category of hardware and software that enables people to use the Internet as the transmission medium for telephone calls by sending voice data in packets using IP rather than by traditional circuit transmissions of the PSTN (Public Switched Telephone Network). • In short VoIP transfers voice through IP packets over the Internet.
Contd.. • Internet telephony products are sometimes called IP telephony,Voice over the Internet (VOI) or Voice over IP (VoIP) products. • The voice traffic is converted into Data packets then routed over the Internet, or any IP network as normal data packets would be transmitted. When the data packets reach their destination, they are converted back to voice data again for the recipient.
How does VoIP work? • A number of years ago sending a signal to a remote destination could be done digitally. VoIP works by digitalizing voice in data packets, sending and reconverting them in voice.
Advantages of Digital Formats • Digital format can be better controlled. • Compressed. • Routed and converted to a new better format. • Noise is tolerant than analog signals. • VoIP uses TCP/IP (TCP/IP is an Internet protocol with a leading IP packet to control communication and the payload).
Advantages of VoIP • It makes long-distance calls less expensive by removing some of the access charges required for use of the public telephone network. • A user's physical location also becomes irrelevant. • VoIP also enables WiFi’s advanced features like checking voice mail or programming call forwarding through a web application.
Disadvantages of VoIP • VoIP services do not work in blackouts. • VoIP services are only as reliable as the customer’s broadband connection. • A poor quality connection can lead to voice quality issues. Luckily, high quality broadband is getting easier and easier to find these days.
VoWiFi(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.
Contd.. • Mobile voice over IP (VoIP) is currently limited to voice over WiFi (VoWiFi) but, with the introduction of cellular technologies providing higher bandwidth capabilities, VoIP is likely to move towards cellular networks.
Over view of VoWiFi • VoWiFi is a term used for technologies or services which provide voice over WiFi • WiFi refers to any wireless LAN products or services that are based on the IEEE 802.11 WLAN standard with theoretical data rates ranging from 11M to 54 Mbit/sec. • A hotspot is a wireless LAN node that provides Internet connection and virtual private network (VPN) access from a given location
Contd.. • With combined VoWiFi/cellular phone and seamless roaming between those two networks, subscribers could use voice over a WiFi network, where available, and cellular connections where WiFi is missing or outside of a WiFi area. • Combining VoIP with WiFi has a great potential to reduce the cost of voice services, in particular for roaming and for access to broadband services, while increasing the convenience to users.
Deployment of VoWiFi • The requirements of the three main segments making up the WLAN marketplace also will have an effect on the deployment parameters of WLANs. These three market segments are
Contd.. • Residential/SOHO (small office, home office) cordless phones or scaled down PBXs that will function as part of an integrated gateway • Enterprise mobile VoIP WLAN network (private network) • Cellular off-load network (VoIP over WLAN in hot spots, which in turn interfaces to the public telephone network) • Such a network would allow seamless multiple access options for most of the more prevalent voice and data services.
Architecture Requirements • In the context of Vo WiFi and VoWiFi-Mobile roaming many of the current deployments of VoWiFi involve integration with enterprise PBXs • One method of integrating with a traditional PBX is to use a Vo WiFi gateway.The calls are routed from the Vo WiFi phone to Vo WiFi gateway via the WiFi Access Point and the Vo WiFi gateway transmits calls to the existing PBX.Integration with PBX allows calls to be placed to and received from the PSTN, and also supports PBX features such as call forwarding messaging and conference calling.
Contd.. • Another way to use Vo WiFi is to use softphones on mobile computers or PDAs which route calls entirely over the internet in WiFi areas such as HOT SPOTS.
Contd.. • The gateway connects to the mobile switching centre for cellular calls, and connects to the data network for WiFi calls. • The gateway manages subscriber access and handoff. As the subscriber moves within range of a wireless access point, the gateway authorizes the subscriber’s access and all network services — both voice and data — are delivered over the WiFi. • When the subscriber moves outside of the WiFi coverage area, the gateway seamlessly switches control over to another WiFi network or the mobile networkdeploying a VoWiFi/mobile roaming solution requires dual-mode handsets that support both VoWiFi as well as mobile
Drivers of VoWiFi Development and VoWiFi/mobile Convergence • WiFi and VoIP are being widely deployed in enterprises. • WiFi is easy and flexible to deploy, and is claimed to be more reliable in terms of coverage while costing less than traditional cellular services. • It is also expected that using VoWiFi new converged applications can be developed for mobile workers with new capabilities such as geographic location information and instant messaging.
Contd.. • In this early stage of the VoWiFi market, the handsets and VoWiFi services have been focused on enterprise or corporate users and are expected to do so in the next few years • The main reason is because VoWiFi is related to the increasing deployment of WiFi and VoIP in corporate environments
Why would mobile service providers want to provide VoWiFi? • At first glance, it would seem that mobile operators would be disadvantaged by providing roaming services with WiFi because they may lose revenue generated by traditional mobile roaming services. • Generally, WiFi services are provided at a lower price than mobile services or even free, which has induced mobile service providers, especially 3G service providers, to consider WiFi and VoWiFi services to be competitive with their mobile services.
Contd.. • recent proliferation of WiFi in enterprises and in the number of hotspots in densely populated areas in a relatively short period of time, several mobile service providers have started to regard VoWiFi and VoWiFi/mobile roaming as a way of reducing prices for their customers and consider WiFi as a means to enhance competition and differentiate their service from that of competitors.
Impact of WiFi and VoWiFi on 3G Development • VoWiFi, or VoIP over WiFi, allows users to make voice calls and access video and data at a low price. • The development of this service will have an impact on 3G services and the way they are structured and priced • While 3G has the advantage of ubiquitous access, the data transfer speed is about a half megabit per second slower than WiFi’s top speed.
User benefits from VoWiFi interconnecting with mobile networks • Users of dual handsets will be able to make calls more cheaply than those using mobile phones. • Calls generated in hotspots or WLANs are likely to result in considerable savings by consumers. • VoWiFi also provides innovative new features such as the ability to access e-mail, Internet, location information, etc. at a lower price
Contd.. • Another benefit for existing users of VoWiFi service is that they are no longer constrained in obtaining service from a limited area such as a hotspot or within a company, but are able to have real mobility and ubiquitous access to voice calls as well as data and video by seamless interconnection with mobile networks with a single handset or portable computer
Technical issues and standard development of VoWiFi • Since VoWiFi is technically based on VoIP over WiFi, quite a few technical issues and challenges are similar to those in WiFi and VoIP • Quality of Service (QoS) • WiFi has its own QoS challenges in that throughput may fluctuate when roaming among Access Points. • Subscribers are more sensitive to perceptible service degradation for voice or video than for data. Therefore, more reliable QoS is necessary for voice to be delivered satisfactorily over WiFi
Contd.. • The issue of QoS will be increasingly important when roaming between WiFi and mobile networks is supported, given that network hand-off can result in quality of service degradation. • Up to now, most wireless equipments did not yet incorporate QoS because they were to emerge. Without standards, local voice systems over WiFi have been provided as bundles of proprietary wireless network hardware and software. • The WiFi Alliance announced a new WiFi Multimedia (WMM) program to deal with quality of service issues in September 2004.41 The WMM program combines core elements of the 802.11e draft and a simplified packet priority access category scheme borrowed from IEEE 802.11d. WMM is designed to improve the QoS for voice, audio, video and multi-media applications over WiFi.
Contd.. • Quality of Service is hard to find these days, but QoS standards for high quality VoWiFi are a work in progress. 802.11e • 802.11e includes what the Wi-Fi Alliance phrases as Wi-Fi Multimedia Extensions (WMM, or WME) for prioritization.
Contd.. • WMM includes four access categories: • Voice Priority, the highest level, is intended to support multiple simultaneous, toll-quality voice calls with low latency. • Video Priority, the next highest level, prioritizes video relative to all other data traffic. One 802.11a/g channel can support three-four SDTV (Standard Definition TV) data streams, or one HDTV (High Definition TV) stream.
Contd.. • Best Effort Priority is intended to support traffic from legacy devices, or from applications or devices that lack QoS capabilities. Best effort traffic is less sensitive to latency than voice or video. Internet surfing is an example. • Background Priority is intended to support low priority traffic that does not have strict latency and throughput requirements. File downloads and print jobs are cited as examples.
Contd.. • There exist a number of proprietary QoS mechanisms such as SpectraLink Voice Priority (SVP), used on SpectraLink phones. • QoS requires not only prioritization, but also smooth handoffs as the handset moves from cell to cell.
Proper bandwidth • With the wide deployment of WiFi in hotspots and in enterprises, the need for higher-speed WiFi is also increasing. • Applications over WiFi use an increasing amount of bandwidth • The number of users and devices connecting to WiFi are increasing and the bandwidth demand is expected to increase with the provision of WiFi/mobile roaming
Security and privacy • The potential security and privacy risks arising from using WiFi for voice have been an obstacle to further development of VoWiFi/mobile roaming • Those risks include stealing packets, unauthorised access to the network and intentional interference by outsiders whichhas a greater impact on business users than residential subscribers. • In general, encryption presently used such as Wired Equivalent Privacy (WEP) is considered weak and susceptible to outside intrusion
Interoperability • The adoption of heterogeneous WiFi technologies may cause incompatibilities • With the advance of WiFi and VoWiFi, a growing number of vendors are trying to differentiate their products beyond existing standards, mainly by boosting speed or security.
Interference and complexity • The spectrum for WiFi is not dedicated and licensed for use by certain entities as in the case of mobile services. Therefore, the users of WiFi share spectrum with other devices, including household devices such as microwaves. • Consequently, as WiFi or VoWiFi deploys further, the spectrum will become increasingly crowded and the possibility of interferences will grow