This document discusses Voice over WiFi (VoWiFi) which allows users to make voice calls over a WiFi network. It provides an overview of WiFi technology, how VoIP works, and the advantages and disadvantages of VoIP. It then discusses VoWiFi specifically - what it is, how it works, examples of deployments and architectures, drivers of its development, and how it may impact 3G networks. Finally, it covers some technical issues and standard development considerations for VoWiFi including quality of service, bandwidth requirements, security, interoperability, and interference.

1. VOICE OVER WiFi

2. 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.

3. 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-Fi Alliance.
• WiFi Alliance An organization made up of leading wireless
equipment and software providers.

4. 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.

5. 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

6. 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.

7. IEEE 802.11 WLAN Standards

8. 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

9. 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.

10. 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).

11. Wifi SECURITY
• 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.

12. 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)

13. Requirements

14. 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.

15. 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.

16. 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.

17. 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).

18. Home phone and one computer

19. Home Phone with more than one computer

20. 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.

21. 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.

22. 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.

23. 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.

24. 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

25. 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.

26. 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

27. 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.

28. 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.

29. 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.

30. Architecture Of VoWiFi

31. 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

32. 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.

33. 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

34. 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.

35. 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.

36. 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.

37. 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

38. 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

39. IEEE 802.11 Protocol Architecture

40. 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

41. 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.

42. 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.

43. 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.

44. 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.

45. 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.

46. 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

47. 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

48. 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.

49. 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

50. Various facts of network capacity planning for the future
deployment of VoWLAN
• Over-subscription of voice networks (voice
concentration)
• Throughput requirements for typical voice, video and
media applications using IP packet technology
• WLAN network capacity for enterprise applications RF
frequency planning and reuse for large network
deployments WLAN network capacity for home
applications
• Consideration of wireless repeaters (mesh) to extend
home coverage

51. Over-subscription of Voice Services
(Concentration)
• A basic understanding of oversubscription, for example, can
assist network planners who are evaluating network capacity
for enterprise VoIP over WLAN applications.
• PSTN Phone lines typically are terminated at a Class 5 switch
or a Digital Loop Carrier (DLC) connected to a Class 5 switch.
The Class 5 switch manages call connections and rejects calls
when the system capacity has been reached

52. Contd..
• In cellular networks, some consideration is given to reserve a
fraction of the active phone line capacity for handoff
purposes between one cell and the next.

53. Voice Throughput over IP
•Voice Compression and VoIP
•Voice compression algorithms help US TO derive as
much capacity from an infrastructure as possible,
but compression algorithms involve tradeoffs
between efficiency and overhead that planners
should consider.
•In wireless networks, voice is digitized with the
G.711 coding standard and
transported at 64 Kbps.

54. Contd..
• While G.711 is the mainstream digital codec for tollquality
voice services, a number of more efficient codes are used for
both cellular and voice "pair gain applications."
• In an IP network, voice codecs are placed into packets with
durations of 5, 10 or 20 msec of sampled voice, and these
samples are encapsulated in a VoIP packet.

55. Throughput of WLAN Access Points
• To optimize the network capacity of a WLAN with a voice
special attention to the throughput of the APs which govern
how quickly data of any sort can be placed on the
network has to be given.

56. Contd..
• The following two basic functions affect the throughput
of an AP:
1. Area and modulation density supported by the cell
a. Small cells can support high data rate
modulations (peak rates)
b. Larger cells will use lower rate 802.11 modulations
and are an
aggregate sum of areas covered and the modulation
rate

57. Contd..
• 2.The WLAN MAC protocols have the following effects:
a. The Ethernet (CSMA/CA) protocols, DCF and EDCF, limit capacity
at approximately 37% of the peak data rate
b. Scheduled TDMA protocols such as HCF can theoretically reach
around 90% capacity of the network, but under full load they will
typically carry only approximately 75% of capacity
c. DCF/EDCF MAC protocols do not effectively manage network
latencies as the capacity limit is approached
d. HCF protocols control latencies by providing fair weighted
queuing so that all users will receive service even under full load
conditions

58. Application of Small-mesh Access Points for
Residential Coverage
• Access points for the residential/SOHO marketplace, cell
coverage and throughput are the most crucial issues facing
WLAN
implementations in this market.
• Wireless repeaters, which can be used to
implement small mesh residential networks, are a low-cost
method of improving coverage and throughput.

59. Contd..
• One possible technique for extending coverage and
improving residential service is the use of multiple APs in a
mesh/repeater architecture.

60. Residential Network Topology

61. A simple example featuring two access
points

62. Contd..
• There are two possibilities for operating a residential mesh
network. They are the following:
Single-Frequency Mode: Access points are not dual-mode
and can only support a single frequency of operation from
an AP to another AP and from an AP to a client/subscriber.
Dual-Frequency Mode: Access points are dual frequency,
supporting two separate links on two separate frequencies
simultaneously.

63. Dual Frequency Mode

64. Access Time Delay
• The time delay and jitter of the VoIP system will be a design
consideration.
• The two following issues relate to time delay and jitter:
1. Signaling for call set up, tear down and other call control
communications will be delayed. (Worst case delay is the principal
concern.)
2. Jitter in the voice traffic/bearer channel will cause delay.

65. Delays in the communication path for an enterprise network

66. Delays in the communication path for an Residential network

67. Deploying VoIP over WLANs
• The technology needed to deploy VoIP over WLANs and the
other wireless applications is being incorporated into next
generation handsets, mobile devices, personal digital
assistants (PDAs), laptop computers, infrastructure systems
and other types of systems.

68. Dartmouth Deployment
• Full VOIP Software by end of 2003
• Campus wide WLAN Network
• 1000 Freshman
• Outbound, Inbound Calls
• Free Wired, Wireless & LD
• PCs, PDAs, other devices
• Traffic & Usage Study
• 13,000 Students, Faculty & Staff

69. Advantages of VoWiFi
• Mobility is the primary selling point, much as it is with cell
phones.
• VoWiFi has the advantage of no airtime charges. As a
wireless technology, there are no wires to run to Wi-Fi
phones. Therefore, network configuration and
reconfiguration processes are fast.

70. Disadvantages of VoWiFi
• VoIP and Wi-Fi are both immature technologies, so merging
the two into VoWiFi carries some associated risks.
• Standards are still in development, and some early pre-
standard versions may not be upgradeable to compliance
level.
• As a data-centric LAN technology, Wi-Fi involves a shared
medium in the form of frequency bands creating issues of
contention and congestion.

71. Contd..
• Troublesome for stream-oriented communications such as
voice, and especially so when handoffs are required as the
user roams between APs.
• Costs have to be considered, of course, and the cost of a
VoWiFi LAN can be double that of a data-only WLAN.
• Wi-Fi phones are easily double the cost of a typical cordless
phone.

72. Contd..
• Current Wi-Fi phones don’t have much, although the next
generation or two should overcome that issue.

73. Benefits
• VoWiFi delivers a simpler, less expensive and more flexible
system for providing mobile data and voice communications
than other technologies that require the implementation
and maintenance of separate systems for each.
• VoWiFi also offers greater reliability and voice quality than
alternatives such as cellular technology.

74. Technical Challenges
• Deliver High Quality without QoS
• Deal with High Packet Loss on WLANs
• Roaming Across WLAN Network Segments
• Roaming From WLAN to Cellular
• Compatibility with Firewalls

75. FUTURE
• The number of businesses using voice over wireless local
area networks (VoWLAN) is set to triple over the next two
years
• A new report from Infonetics Research has found that 10 per
cent of north American businesses are now using VoWLAN.
The researchers expect that percentage to reach 31 per cent
by 2007.
• The main reasons now holding back the uptake of wireless
LANs in business are fears over security and privacy.

76. Wireless VOIP Growth
Wi-Fi
PDAs
&
Laptops
More Wi-Fi Devices
More Places to Use
More Mobile Users

77. Conclusion
• Technology exists today to implement VoIP over WLANs applications
as an integral part of next-generation seamless
wireless voice/data networks.
• The wireless industry has already begun to
migrate toward an environment where one phone number can be
used practically anywhere for voice and data applications.
• To accomplish this goal, mobile device designers, carriers, service
providers and enterprise/home
network designers face deployment, provisioning and
implementation issues.

78. QUESTIONS
• 1.What are the technical issues and challenges involved in VoWiFi?
Write about the quality of service in VoWiFi?
• 2.Advantages and Disadvantages of VoWiFi?
• 3.What are the Common Vo WiFi Infrastructure Problems?

79. SOLUTIONS
• 1. The Technical issues of VoWiFi are
Quality of Service (QoS)
Proper bandwidth
Security and privacy
Interoperability
Interference and complexity
• The Technical challenges are
Deliver High Quality without QoS
Deal with High Packet Loss on WLANs
Roaming Across WLAN Network Segments
Roaming From WLAN to Cellular
Compatibility with Firewalls

80. • 2. The Advantages of VoWiFi-
• Mobility is the primary selling point, much as it is with cell phones.
• VoWiFi has the advantage of no airtime charges. As a wireless technology,
there are no wires to run to Wi-Fi phones. Therefore, network configuration and
reconfiguration processes are fast.
• VoWiFi delivers a simpler, less expensive and more flexible system for
providing mobile data and voice communications than other technologies that
require the implementation and maintenance of separate systems for each.
• VoWiFi also offers greater reliability and voice quality than alternatives such
as cellular technology

81. • Disadvantages of VoWiFi-
• VoIP and Wi-Fi are both immature technologies, so merging the two into VoWiFi
carries some associated risks.
• Standards are still in development, and some early pre-standard versions may not be
upgradeable to compliance level.
• As a data-centric LAN technology, Wi-Fi involves a shared medium in the form of
frequency bands creating issues of contention and congestion
• Troublesome for stream-oriented communications such as voice, and especially so
when handoffs are required as the user roams between APs.
• Costs have to be considered, of course, and the cost of a VoWiFi LAN can be double
that of a data-only WLAN.
• Wi-Fi phones are easily double the cost of a typical cordless phone.
• Current Wi-Fi phones don’t have much, although the next generation or two should
overcome that issue.

82. 3. Scalability
Quality of Service
Usability