IMS (IP Multimedia Subsystem)

Hi All,

    Here is an introduction to upcoming technology, which is set of standards, developed by the wireless standards body 3rd Generation Partnership Project (3GPP), for providing IP based multimedia services including IP telephony.

It creates new opportunities for operators who want to deliver attractive, easy-to-use, reliable and profitable multimedia services – including voice, pictures, text and video, or any combination of these – with existing services. 

IMS addresses key issues such as convergence, service creation and delivery, service interconnection and open standards. 

Access-Independent: it is open standardized way to deliver IP-based consumer and enterprise services, enabled by one common core and control, to the fixed, mobile and cable communities. 

When implemented according to agreed standards, IMS enables operators to mix and match equipment and applications from multiple vendors, and enables mobile users to access their personal set of services wherever they roam, whichever operator network they are connected to.

IMS includes the tools and functions needed to handle numerous non-standardized services in a standardized way – ensuring the interoperability, access awareness, policy support, charging, security and quality of service functionality required to meet consumer demand for attractive and convenient offerings.

IMS is not intended to standardize applications, but rather to aid the access of multimedia and voice applications from wireless and wireline terminals. This is done by having a horizontal control layer that isolates the access network from the service layer.

Users Benefits:-

• All services, such as voice, video, SMS, conferencing, IPTV etc. will be available on the device being used. This will provide user with rich media experience.

• Safe and secure communication.

• The users will be able to personalize their communication need, such as preferred medium of communication depending on, who is calling etc.

• The use of Internet technologies will allow a seamless communication irrespective of user’s location and the platform of communication

Service Providers Benefits:-

• Use of IP backbone by IMS will provide an optimized transport and coding.

• IMS provides a common standardized platform with reusable components for development of new services. This will reduce development time and allow roll out of new multimedia services quickly, as per the market requirement.

• Quality of service (QoS) has been as issue with IP services. The IMS has been designed keeping in mind quality of service (QoS) requirement, so that the guaranteed bandwidth requirement can be met.

• IMS allow flexibility in charging users as per the services utilized by them.

• The open standards used by IMS allow inter-networking and interoperability between various service providers. This enables them to provide seamless communication to user irrespective of network he is in and the device he is using.

• The open architecture, available common services and converged IP backbone will reduce system complexity, thereby bringing down the CapEx and OpEx for the operators.

• The IMS design has been done keeping in mind operators & allows operators to deploy third party developers for developing application without losing the control of their network.

Main Nodes of IMS System:-

        The Call Session Control Function (CSCF) and the Home Subscription Server (HSS) are the essential nodes in the IMS system. 

• The IETF (Internet Engineering Task Force) Session Initiation Protocol (SIP) is the control signaling routed by the CSCF. 
• The HSS provides the user profile database to manage user authentication and authorization for the subscribed services.

More Information will be Updated Soon....

Comments are most Welcomed.

CheEeEeRrRrRsSsS...
Telecom Tigers Team
telecomtigers@gmail.com
http://homepageforu.webs.com/

How GPRS Works

Hi All,

   Lets have some details regarding GPRS Working, As we all know, It’s a Packet Switched Network, 

          

          In a GPRS Network, a user station doesn't occupy a dedicated path during an Internet connection. However, each end user station (e.g. mobile phone) is allocated several time slots out of 8 GSM/TDMA available time-slots for GPRS service. 

          
          Each time slot has a maximum capacity of 14.4 kbps, depending on how many time slots are allocated for the downlink (from a base station to a user station) and the uplink (from a user station to a base station), 

          
          GPRS devices are divided into multi-slot classes. A multi-slot class is often represented by the number of downlink and uplink slots. For example, Class 10 is also known as Class 4+2. While active slots indicate the maximum number of slots that can be allocated for both downlink and uplink in a specific class.

Class Types :-

• 2+1 (two slots for download + 1 for upload)
• 3+1 (three slots for download + 1 for upload)
• 4+1 (four slots for download + 1 for upload)

          GPRS is a mobile data upgrade to a GSM mobile phone network. This provides users with packet data services (similar to the Internet) using the GSM digital radio network. Each voice circuit in GSM transmits the speech on a secure 14kbps digital radio link between the mobile phone and a nearby GSM transceiver station.

          The GPRS service joins together multiple speech channels to provide higher bandwidth data connections for GPRS data users. The radio bandwidth remains the same, it is just shared between the voice users and the data users. The network operator has the choice of prioritizing one or the other.

           
          GPRS users will also benefit from being able to use GPRS while traveling as the GSM system should transparently hand over the GPRS connection from one base station to another.

GPRS Roaming - There are two type of GPRS Roaming

Home Network Roaming - Here all data is transmitted from wherever you connect to a GPRS network to your home GPRS network where it is connected to the Internet or your company LAN as if you were indeed in your home country.

Local Network Roaming - Data is just connected to a local Internet connection point and will be subject to local conditions for security and performance.

Radio Interface

           
          Each GSM radio transceiver uses Time Division Multiplexing to deliver eight voice circuits on one radio channel. Each radio site may have one or more transceivers to provide sufficient channels to end users (maximum numbers are limited by many factors including - operators radio license, interference with other nearby GSM cells, cost of equipment, capacity of radio site infrastructure, etc.)

          Each 14kbps channel may be shared by multiple 'connected' GPRS users (many users will be connected to the network but transmitting very little data). As a user's data requirements grow, they will use more of the available capacity within that timeslot, and then more available timeslots up to the maximum available or the maximum supported by their device.

In general the higher the data rate, the more power the mobile device will use and the shorter the battery life and the higher the transmitted RF power.

GPRS Tunneling Protocols will be updated soon….

Comments and Appreciations are most welcome.

ChEeEeEeErRrRrRs!!!

Telecom Tigers Team

telecomtigers@gmail.com

http://homepageforu.webs.com/

SIP (Session Initiation Protocol) Call Flow

Hi All,

        We have already discussed the basics of SIP in our last post. Here we would like to share the SIP call flow. Here we have also included PSTNs, so that the reader can co-relate the message of SIP and ISUP.

Scenario:
   
     A Number wants to call  B Number which is catered by PSTN B.

• PSTN A to MSS X protocol used in ISUP.
• MSS X to MSS Y protocol used in SIP.
• MSS Y to PSTN B protocol is ISUP.

1) After receiving IAM  from PSTN A with called party number as B number  MSS X after number analysis detects the B number has to be routed to MSS Y which is connected by SIP. MSS X send a INVITE message.
Major components of INVITE are "Called Party", "Calling Party", "Bearer information", "Codec".

2) MSS Y receives INVITE and responds with 100 (Trying) message.
This response indicates that the request has been received by the next-hop server and that some unspecified action is being taken on behalf of this call (for example, a database is being consulted). At the same time after number analysis its send IAM to PSTN B.

3) MSS Y send 183 message to MSS X. This message is called as Session progress indicated that session is in progress. In response to 183 MSS A sends PRACK. PRACK (PRovisional ACKnowledgement) is like any another request within a dialog.
** PRACK is response for 1XX mesages
    ACK is response for 2XX messages.

4) After analysis of B number PSTN B sends ACM with "Called Party status indicator = no indication" to MSS Y. MSS Y sends 200 message to MSS X in turn MSS X forwards ACM message to PSTN A.

5) When B number starts ringing PSTN B send CPG message with "Called Party status indicator = Subscriber free". Indicates that subscriber is free and ringing.
MSS Y send 180 ringing message to MSS X.

Which is communicated to PSTN A in CPG message and A number can hear a ringtone.

6) B number answers the call in response PSTN B send ANM message to MSS Y. MSS Y send 200(With ANM) message to MSS X. MSS X responds with ACK , also forwards ANM message to PSTN A. At this point of time speech path is through.

7) After conversation A number releases the call. REL is send from PSTN A to MSS X in response MSS X sends BYE message to MSS Y. MSS Y send the REL message to PSTN B.

8) PSTN B release the resources and respond with RLC message to MSS Y. MSS Y relays the 200(with RLC) message to MSS X. RLC is then forwarded to PSTN A. This complete the release of all resources used for call.

Comments and Appreciations are most welcome.

ChEEeeeEEeeeErs!!!
Telecom Tigers Team
telecomtigers@gmail.com
http://homepageforu.webs.com/