Transcript VOICE OVER WiFi - Computer Science and Engineering

VOICE OVER WiFi
by
Narendranath Kanukolanu
Rahul Datta
Kalyan Valluri
TOPICS
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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-Fi Alliance.
 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
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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).
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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..
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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.
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802.11g
Applies to wireless LANs and provides 20+ Mbps in the 2.4
GHz band.
IEEE 802.11 WLAN Standards
An 802.11 WLAN History
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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).
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.
Hardware needed to create
WiFi Network
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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.
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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)
Requirements
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
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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).
Home phone and one computer
Home Phone with more than one
computer
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.
Architecture Of VoWiFi
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.
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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
IEEE 802.11 Protocol Architecture
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
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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..
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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..
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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.
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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
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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
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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
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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
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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.
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Consequently, as WiFi or VoWiFi deploys further, the spectrum
will become increasingly crowded and the possibility of
interferences will grow
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
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
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.
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.
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.
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.
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
Contd..
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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
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.
Contd..
 One possible technique for extending coverage
and improving residential service is the use of
multiple APs in a mesh/repeater architecture.
Residential Network Topology
A simple example featuring two
access points
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.
Dual Frequency Mode
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.
Delays in the communication path for an
enterprise network
Delays in the communication path for an
Residential network
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.
Dartmouth Deployment
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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
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.
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.
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.
Contd..
 Current Wi-Fi phones don’t have much,
although the next generation or two should
overcome that issue.
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.
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
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.
More Places to Use
Wi-Fi PDAs & Laptops
Wireless VOIP Growth
More Mobile Users
More Wi-Fi Devices
Conclusion
 Technology exists today to implement VoIP over
WLANs applications as an integral part of nextgeneration 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.
References
 http://www.wifiplanet.com/news/article.php/1015241
 http://www.cisco.com/en/US/products/hw/phon
es/ps379/products_administration_guide_chapter
09186a008024662c.html
 http://www.technologyreview.com/articles/04/0
8/wo_brown081104.asp
 http://www.wired.com/wired/archive/11.06/star
t.html?pg=8
 http://www.wi-fitechnology.com/wifi_forum_submit_news.shtml
 http://www.crm2day.com/experts/EEpAZyuAuVg
LprsEUp.php
 Source: http://news.zdnet.com/2100-1035_225571870.html
 http://www.wi-fitechnology.com/user.php
 http://www.telecomasia.net/telecomasia/article/
articleDetail.jsp?id=168107
 http://www.commweb.com/showArticle.jhtml?art
icleId=168601894
 http://www.google.com/search?hl=en&q=find+v
oice+over+wifi
 www.intel.com
 www.doceotech.com
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?
SOLUTIONS
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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
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2. The Advantages of VoWiFiMobility 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
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Disadvantages of VoWiFiVoIP 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.
3. Scalability
Quality of Service
Usability
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