2. 2
INDEX
____________
1. Introduction 4
2. Features in Google Voice 6
3. Networking protocols involved 8
4. Benefits of Google Voice 14
5. Conclusion 15
6. References 16
3. 3
Introduction and History
Google Voice is a telecommunications service by Google launched on
March 11, 2009. The service provides a US phone number, chosen by
the user from available numbers in selected area codes, free of charge
to each user account. Inbound calls to this number are forwarded to
other phone numbers of the subscriber. Outbound calls may be placed
to domestic and international destinations by dialing the Google Voice
number or from a web-based application. Inbound and outbound calls
to US (including Alaska and Hawaii) and Canada are free of charge.
International calls are billed according to a schedule posted on the
Google Voice website.
The service is configured and maintained by the user in a web-based
application, styled after Google's e-mail service, Gmail. Users must have
an established US telephone service to activate Google Voice. Users
must configure this and optionally, additional phone numbers that ring
simultaneously when the Google Voice number receives a call. The user
may answer and receive the call on any of the ringing phones. Google
Voice provides additional features such as voicemail, call history,
conference calling, call screening, blocking of unwanted calls, and voice
transcription to text of voicemail messages. Received calls may be
moved between configured telephones during a call.
Google Voice is available only for users in the United States. Users may
select a single US phone number from various area codes. Incoming
4. 4
calls to the number may ring simultaneously any of the user's
configured phones or the account's Google Talk feature. Based on the
calling number, or contact group (e.g., Family, Friends, Work), or on
time of day, e.g., disabling a home phone during business hours and
routing calls to mobile or business number, individual numbers may be
configured to ring. The service also features voicemail with indexable
automated voicemail transcription, accessible via a web browser, e-
mail, or by phone. Google Voice provides automatic blocking of known
numbers, e.g., telemarketers, the ability to switch lines in mid-call,
differentiated voice mail greetings based on caller, SMS forwarding,
and call recording. Additionally, customers of Gizmo5, a Session
Initiation Protocol (SIP) service vendor, may forward calls to their
Gizmo service which may be answered using a free computer
application or a web application.
GrandCentral, founded in 2005 by Craig Walker and Vincent Paquet
with funding by Minor Ventures, was acquired by Google on July 2,
2007, for US$95 million in a transaction led by Wesley Chan. On March
11, 2009, the management of the service revealed that the team had
been working on it throughout that period, apparently in secret, and
that it was being rebranded "Google Voice”.] It was to keep most of the
functionality originally offered in GrandCentral and add new features
The following figure shows the interface of Google voice.
5. 5
Features in Google Voice
1. A single Google forwarding number to all of the user's
phones
Using Google Voice we are able to establish a abstraction layer by
providing a single “Google number” to the world, which underneath is
connected to several telephone numbers at a time. Using such a
feature enables the caller to ring all the phones of the person he/she is
calling to ensure that the call is picked at any cost. This feature also
enables a user to customize which phone to ring depending on the time
of the day or the caller calling the number.
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2. Call screening
Announcement of callers based on their number or by an automated
identification request for blocked numbers
3. Blocking calls from specified numbers
In an enhancement to the existing services provided by the telephony
companies, Google voice allows handset independent blocking of calls
from specific users. Those callers will hear a “number not in service”
message when they call to the Google number of the said user.
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4. Send, receive, and store SMS online
Connecting the internet and the mobile phone has always been an
objective of Google. Using Google Voice we can send and receive
SMSes absolutely free of carrier charge. It also provides a facility to
store the SMSes in form of email in your gmail account.
5. Voicemail transcripts
Voicemail is a feature using which we can hear audio messages of
callers when we cannot pick up their calls. Google takes this feature a
step further using which we can get a transcript of the voicemail
delivered to our inbox and sms which we can read rather than listening.
Networking protocols involved
As with any internet telephony service, Google voice is primarily based
on the Voice over Internet Protocol (VoIP) and coupled with the Session
Initiation Protocol (SIP) in the application layer.
8. 8
1. Voice over Internet Protocol
Voice over Internet Protocol (Voice over IP, VoIP) is a general term for a
family of methodologies, communication protocols, and transmission
technologies for delivery of voice communications and multimedia
sessions over Internet Protocol (IP) networks, such as the Internet.
Other terms frequently encountered and often used synonymously
with VoIP are IP telephony, Internet telephony, voice over broadband
(VoBB), broadband telephony, and broadband phone.
Internet telephony refers to communications services — voice, fax,
SMS, and/or voice-messaging applications — that are transported via
the Internet, rather than the public switched telephone network
(PSTN). The steps involved in originating an VoIP telephone call are
signaling and media channel setup, digitization of the analog voice
signal, optionally compression, packetization, and transmission as
Internet Protocol (IP) packets over a packet-switched network. On the
receiving side similar steps reproduce the original voice stream.
VoIP systems employ session control protocols to control the set-up
and tear-down of calls as well as audio codecs which encode speech
allowing transmission over an IP network as digital audio via an audio
stream. Codec use is varied between different implementations of VoIP
(and often a range of codecs are used); some implementations rely on
narrowband and compressed speech, while others support high fidelity
stereo codecs.
VoIP can be a benefit for reducing communication and infrastructure
costs. Examples include:
1. Routing phone calls over existing data networks to avoid the need
for separate voice and data networks.
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2. Conference calling, IVR, call forwarding, automatic redial, and
caller ID features that traditional telecommunication companies
(telcos) normally charge extra for are available free of charge
from open source VoIP implementations.
3. VoIP can facilitate tasks and provide services that may be more
difficult to implement using the PSTN. Examples include:
4. The ability to transmit more than one telephone call over a single
broadband connection.
5. Secure calls using standardized protocols (such as Secure Real-
time Transport Protocol). Most of the difficulties of creating a
secure telephone connection over traditional phone lines, such as
digitizing and digital transmission, are already in place with VoIP.
It is only necessary to encrypt and authenticate the existing data
stream.
6. Location independence. Only a sufficiently fast and stable Internet
connection is needed to get a connection from anywhere to a
VoIP provider.
7. Integration with other services available over the Internet,
including video conversation, message or data file exchange
during the conversation, audio conferencing, managing address
books, and passing information about whether other people are
available to interested parties
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The Session Initiation Protocol (SIP) is an IETF-defined signaling
protocol, widely used for controlling multimedia communication
sessions such as voice and video calls over Internet Protocol (IP). The
protocol can be used for creating, modifying and terminating two-party
(unicast) or multiparty (multicast) sessions consisting of one or several
media streams. The modification can involve changing addresses or
ports, inviting more participants, and adding or deleting media streams.
Other feasible application examples include video conferencing,
streaming multimedia distribution, instant messaging, presence
information, file transfer and online games.
SIP was originally designed by Henning Schulzrinne and Mark Handley
starting in 1996. The latest version of the specification is RFC 3261 from
the IETF Network Working Group. In November 2000, SIP was accepted
as a 3GPP signaling protocol and permanent element of the IP
Multimedia Subsystem (IMS) architecture for IP-based streaming
multimedia services in cellular systems.
The SIP protocol is an Application Layer protocol designed to be
independent of the underlying transport layer; it can run on
Transmission Control Protocol (TCP), User Datagram Protocol (UDP), or
Stream Control Transmission Protocol (SCTP). It is a text-based
protocol, incorporating many elements of the Hypertext Transfer
Protocol (HTTP) and the Simple Mail Transfer Protocol (SMTP).
SIP employs design elements similar to the HTTP request/response
transaction model. Each transaction consists of a client request that
invokes a particular method or function on the server and at least one
response. SIP reuses most of the header fields, encoding rules and
status codes of HTTP, providing a readable text-based format.
A motivating goal for SIP was to provide a signaling and call setup
protocol for IP-based communications that can support a superset of
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the call processing functions and features present in the public
switched telephone network (PSTN). SIP by itself does not define these
features; rather, its focus is call-setup and signaling. However, it was
designed to enable the construction of functionalities of network
elements designated proxy servers and user agents. These are features
that permit familiar telephone-like operations: dialing a number,
causing a phone to ring, hearing ringback tones or a busy signal.
Implementation and terminology are different in the SIP world but to
the end-user, the behavior is similar.
SIP-enabled telephony networks can also implement many of the more
advanced call processing features present in Signaling System 7 (SS7),
though the two protocols themselves are very different. SS7 is a
centralized protocol, characterized by complex central network
architecture and dumb endpoints (traditional telephone handsets). SIP
is a peer-to-peer protocol, thus it requires only a simple (and thus
scalable) core network with intelligence distributed to the network
edge, embedded in endpoints (terminating devices built in either
hardware or software). SIP features are implemented in the
communicating endpoints (i.e. at the edge of the network) contrary to
traditional SS7 features, which are implemented in the network
The diagram next page clearly describes the working of the SIP
protocol.
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Benefits of Google Voice
1. Lowering costs
Free calls and SMS
International calls as low as $0.02 per minute
2. Managerial Benefits
Voicemail transcripts. Reading of voicemail messages online
Downloading of voicemails.
Call recording and online archiving.
Blocking calls from specified numbers
3. Personal Benefits
Answering incoming calls on any configured phone
Switching of phones during a call
Conference calling
Notification of voicemail messages via email or SMS
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Conclusion
Google has always tried to change the way we look at computing.
And by creating the Google Voice application, the Mountain View
giant has shown its intentions again.
Google Voice is the future of telephony as VoIP takes over
traditional and orthodox telephony protocols.
The amount of services Google has been able to wrap with a free
price tag itself is an example of cheaper technology enabling its
access to all sections of the human society to improve its living
standard.
Although Google Voice is currently available only in the US, it has
plans of expanding its usage in the Asia Pacific within the next 8-10
months.
Its advent is surely revolutionary and with stiff competitors like
Skype and Verizon in the market, the end user is surely going to
benefit from all the rush.
