|
Introduction:
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:
1.
Bearer
Services
2.
Teleservices
3.
Supplementary
Services
4.
Service
Capabilities
Lets discuss each of them below
Bearer Services:
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.
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.
Information transfer:
Connection oriented /
connectionless services
Both Connection oriented and
connectionless services shall be supported.
Traffic type:
It is required that the bearer
service provides one of the following:
·
guaranteed/constant
bit rate,
·
non-guaranteed/dynamically
variable bit rate, and
·
real
time dynamically variable bit rate with a minimum guaranteed bit rate..
Real time and non real time applications
shall be supported.
·
Real
time video, audio and speech shall be supported. This implies the:
·
ability
to provide a real time stream of guaranteed bit rate, end to end delay and
delay variation.
·
ability
to provide a real time conversational service of guaranteed bit rate, end to
end delay and delay variation.
·
Non real
time interactive and file transfer service shall be supported. This implies
the:
·
ability
to support message transport with differentiation as regards QoS between
different users.
·
Multimedia
applications shall be supported. This implies the:
·
ability
to support several user flows to/from one user having different traffic types
(e.g. real time, non real time)
Traffic characteristics
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
1.
Point-to-Point
o
Uni-Directional
o
Bi-Directional
o
Symmetric
o
Asymmetric
2.
Uni-Directional
Point-to-Multipoint
o
Multicast
o
Broadcast
Information Quality
Information quality characterises
the bit integrity and delay requirements of the applications.
Maximum transfer delay
Transfer delay is the time between
the request to transfer the information at one access point to its delivery
at the other access point.
Delay variation
The delay variation of the
information received information over the bearer has to be controlled to
support real-time services.
Bit error ratio
The ratio between incorrect and
total transferred information bits.
Data rate
The data rate is the amount of
data transferred between the two access points in a given period of time.
Supported bit rates
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
& 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:
·
At least
144 kbits/s in satellite radio environment.
·
At least
144 kbits/s in rural outdoor radio environment.
·
At least
384 kbits/s in urban/suburban outdoor radio environments.
·
Greater
than 2 Mbits/s in urban/suburban outdoor radio environments.
·
At least
2048 kbits/s in indoor/low range outdoor radio environment.
·
Greater
than 2 Mbits/s in indoor/low range outdoor radio environment.
Teleservices
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
- Speech/Telephony
- Emergency Calls
- Short Message Service - Point
to Point (SMS-PP)
- Short Message Service - Cell
Broadcast (SMS-CB)
- Internet Access
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.
Supplementary Services (SS)
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.
The following is list of some of
the supplementary services (see [5] for more details)
- Call Forwarding
- Call Deflection
- Call Waiting
- Call Hold
- Call Restriction and Call
barring
- Number Identification
Service Capabilities
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.
Two different types of service
capability features can be distinguished (see [8] for details:
- Framework service capability
features: these
shall provide commonly used utilities, necessary for the non-framework
service capability features to be accessible, secure, resilient and
manageable.
- Non-Framework service
capability features: these
shall enable the applications to make use of the functionality of the
underlying network capabilities (e.g. User Location service capability
features).
Examples of Framework Service
Capability features are
- Authentication
- User-Network Authentication
- Application-Network
Authentication
- User-Application
Authentication
- Authorisation
- Application-Network
Authorisation
- User-Application
Authorisation
- Registration
- Discovery
- Notification.
Examples of Non-Framework service
capability features are
- Session Control
- Security/Privacy
- Address Translation
- Location
- User Status
- Terminal Capabilities
- Messaging
- Data Download
- User Profile Management
- Charging
References:
[1] 3GPP TS 22.105: Service
Aspects; Services and Service capabilities
[2] 3GPP TS 23.107: Quality of Service
(QoS) concept and architecture
[3] 3GPP TS 22.002: Circuit
switched Bearer Services supported by PLMN
[4] 3GPP TS 22.060: General Packet
Radio Service; Service Description; Stage 1
[5] 3GPP TS 22.004: General on
Suplementary Services
[6] 3GPP TS 22.001: Principles of
circuit telecommunication services supported by a Public Land Mobile Network
[7] 3GPP TS 22.003: Circuit
Teleservices supported by a Public Land Mobile Network
[8] 3GPP TR 22.121: The Virtual
Home Environment
[9] 3GPP TS 22.038: SIM Toolkit;
Stage 1
[10] 3GPP TS 22.057: Mobile
Execution Environment (MExE); Service Description; Stage 1
[11] 3GPP TS 22.078: Customised
Applications for Mobile network Enhanced Logic (CAMEL); Service Definition -
Stage 1
|
