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mansoor2
2008-10-03, 10:59 AM
<i>Introduction: </i>
</font>Services are
communication capabilities that are made available to the users by the
Home Environment (HE) and the Serving Network(SN). The services are
divided into four main classes:
</font><blockquote>
<ol><li>Bearer Services
</li><li>Teleservices
</li><li>Supplementary Services
</li><li>Service Capabilities
</li></font></ol>
</blockquote>
Lets discuss each of them below

</font><i>Bearer Services: </i>
</font>Bearer services in UMTS
are negotiable (unlike GSM where they are not) and can be used flexibly
by applications. Bearer services provide the capability for information
transfer between access points and only lower layer functions. PS (see
[4]) and CS (see [3]) domains provide a specific set of bearer
capabilities. </font>Bearer services are
charachterised by a set of end-to-end charachteristics with
requirements on QoS. QoS (or Quality of Service) is the quality of the
service that has been requested. The service charachteristics includes
things like traffic type, supported bit rates and the quality of
information. These parameters are negotiated when a connection is being
established. If the network is unable to provide the required QoS, it
will re-negotiate the QoS depending on what is available. After the
connection has been established, if there is a need then these
parameters can be re-negotiated again. The following are the brief
description of the bearer services.
</font><blockquote>
<i>Information transfer: </i>
</font><i>Connection oriented / connectionless services</i>
</font>Both Connection oriented and connectionless services shall be supported.

</font><i>Traffic type:</i>
</font>It is required that the bearer service provides one of the following:
</font><ul><li>guaranteed/constant bit rate,
</li><li>non-guaranteed/dynamically variable bit rate, and
</li><li>real time dynamically variable bit rate with a minimum guaranteed bit rate..
</li></font></ul>
Real time and non real time applications shall be supported.
</font><ul><li>Real time video, audio and speech shall be supported. This implies the:
</li><li>ability to provide a real time stream of guaranteed bit rate, end to end delay and delay variation.
</li><li>ability to provide a real time conversational service of guaranteed bit rate, end to end delay and delay variation.
</li><li>Non real time interactive and file transfer service shall be supported. This implies the:
</li><li>ability to support message transport with differentiation as regards QoS between different users.
</li><li>Multimedia applications shall be supported. This implies the:
</li><li>ability to support several user flows to/from one user having different traffic types (e.g. real time, non real time)
</li></font></ul>

<i>Traffic characteristics</i>
</font>It shall be possible for
an application to specify its traffic requirements to the network by
requesting a bearer service with one of the following configurations </font><ol><li>Point-to-Point
<ul><li>Uni-Directional
</li><li>Bi-Directional
</li><li>Symmetric
</li><li>Asymmetric
</li></ul>
</li><li>Uni-Directional Point-to-Multipoint
<ul><li>Multicast
</li><li>Broadcast
</li></ul>
</li></font></ol>

<i>Information Quality</i>
</font>Information quality characterises the bit integrity and delay requirements of the applications.

</font><i>Maximum transfer delay</i>
</font>Transfer delay is the
time between the request to transfer the information at one access
point to its delivery at the other access point. </font><i>Delay variation</i>
</font>The delay variation of the information received information over the bearer has to be controlled to support real-time services.
</font><i>Bit error ratio </i>
</font>The ratio between incorrect and total transferred information bits.
</font><i>Data rate</i>
</font>The data rate is the amount of data transferred between the two access points in a given period of time.

</font><i>Supported bit rates</i>
</font>It shall be possible for
one application to specify its traffic requirements to the network by
requesting a bearer service with any of the specified traffic type,
traffic characteristics, maximum transfer delay, delay variation, bit
error ratios &amp; data rates. It shall be possible for the network to
satisfy these requirements without wasting resources on the radio and
network interfaces due to granularity limitations in bit rates. It
shall be possible for one mobile termination to have several active
bearer services simultaneously, each of which could be connection
oriented or connectionless. The only limiting factor for satisfying
application requirements shall be the cumulative bit rate per mobile
termination at a given instant (i.e. when summing the bit rates of one
mobile termination’s simultaneous connection oriented and
connectionless traffic, irrespective of the traffic being real time or
non real time) in each radio environment:
</font><ul><li>At least 144 kbits/s in satellite radio environment.
</li><li>At least 144 kbits/s in rural outdoor radio environment.
</li><li>At least 384 kbits/s in urban/suburban outdoor radio environments.
</li><li>Greater than 2 Mbits/s in urban/suburban outdoor radio environments.
</li><li>At least 2048 kbits/s in indoor/low range outdoor radio environment.
</li><li>Greater than 2 Mbits/s in indoor/low range outdoor radio environment.
</li></font></ul>

</blockquote>


<i>Teleservices</i>
</font>Teleservices provide the
full capabilities for communications by means of terminal equipment,
network functions and possibly functions provided by dedicated centres.
Basically it is a service that provides complete end-to-end capability
for communication between mobile users according to standards.
Teleservices contain both single media and miultimedia services. Some
of the teleservices are listed below
</font><ul><li>Speech/Telephony
</li><li>Emergency Calls
</li><li>Short Message Service - Point to Point (SMS-PP)
</li><li>Short Message Service - Cell Broadcast (SMS-CB)
</li><li>Internet Access
</li></font></ul>
Teleservices utilises the bearer
services provided by lower layers. The Bearer Services and the
Teleservices are not coupled to each other so as to aid independent
development and changes to one may not necessarily mean changes to
other.
</font><i>Supplementary Services (SS)</i>
</font>A supplementary service
modifies or supplements a basic telecommunication service.
Consequently, it cannot be offered to a user as a stand alone service.
A stand alone service can be either Bearer Service or Teleservice but
cannot be Supplementary service. It shall be offered together or in
association with a basic telecommunication service. The same
supplementary service may be applicable to a number of basic
telecommunication services. Also, one basic telecommunication service
may use several SS simultaneously.
</font>The following is list of some of the supplementary services (see [5] for more details)
</font><ul><li>Call Forwarding
</li><li>Call Deflection
</li><li>Call Waiting
</li><li>Call Hold
</li><li>Call Restriction and Call barring
</li><li>Number Identification
</li></font></ul>

<i>Service Capabilities</i>
</font>Services Capability
Features are open, technology independent building blocks accessible
via a standardised application interface. This interface shall be
applicable for a number of different business and applications domains
(including besides the telecommunication network operators also service
provider, third party service providers acting as HE-VASPs, etc.). All
of these businesses have different requirements, ranging from simple
telephony and call routing, virtual private networks, fully interactive
multimedia to using UE based applications. Since the API is
standardised but not the services, Mobile operators can utilise the API
to build unique value-added services. </font><br>