MNP - Mobile Number Portability

              Mobile Number Portability (MNP) enables Mobile telephone users to RETAIN their mobile telephone number, when changing from one service provider to another or their Location.
              In this, if a customer is dissatisfied on the service by mobile operator either he has to reluctantly accept the service or switch to another service provider that he wishes. In the later case, he has to drop his identity, the mobile number. In most cases when the mobile number is used for all business and family correspondence, it becomes generally impossible to leave the number. To overcome these hardships, the concept of MNP (Mobile Number Portability) was introduced.

Types of Number Portability :-
               The various types of number portability are:

• Service Provider Number Portability: Subscribers can change the service provider while retaining the same phone number It is also called operator portability.
• Location Number Portability: Subscribers can change their service location while keeping the same mobile telephone number.
• Service Portability: Subscribers can change the subscribed services while retaining the same telephone number. It allows the subscribers to enjoy the subscribed services in the same way when they roam outside their home networks.

Concept :-
              MNP functionality is used only in MT (Mobile Terminating) transactions of voice and messaging. For MO (Mobile Originating) transactions, the current flow scenario remains unchanged.
             Only for the MT functionality, the mobile number has to be identified and the corresponding service provider has to be interrogated for optimal routing of the service.

Basic Terms :-

• Ported out – If a subscriber moves to new service provider, for the old service provider, he is a “ported out” subscriber.
• Ported in - If a subscriber moves to new service provider, for the new service provider, he is a “ported in” subscriber.
• Donor – The service provider left by the subscriber. OR  It is the network that first assigns a telephone number to a subscriber
  
• Recipient – The service provider joined by the subscriber. OR  It is the network that currently serves the ported number. A recipient network is a network that a subscriber’s number is ported to when the subscriber switches the service provider.
• Old Serving Network – The old serving network is the network that previously served the ported number before the number was ported to the new serving network. Since a subscriber can switch
  service provider any number of times, the old service provider is not necessarily the same as the donor network.
• Participant – A Participant is a service provider who is not related to the porting process in any way and still needs the routing information for call routing and various other activities.
  
• CDB / NPDB – Central Database or Number Portability Database.
  
• ACQ – All Call Query

There are two basic implementation of MNP.

• Indirect Routing or decentralized or bilateral architecture: 

This model works bilaterally between the donor and recipient service providers who are responsible for informing all others of the change. It would suit to markets with less number of service providers. Each provider will have a dedicated setup and comprehensive database of ported out and ported in subscribers. As the number of service providers increases, the bilateral approach becomes a great burden to all service providers involved in terms of time, cost and resources. FNR (Flexible Number Register) will help the service providers have the ported database in addition to the original HLR database.

• Direct Routing or centralized architecture:

In direct routing, the concept of CDB comes into picture. This central database or Central clearing house will handle all activities related to porting of subscribers between service providers. This model is suited for markets with several service providers and this model is currently used almost in all MNP implementations. Two options are available with this model with all the service providers updating the ported number database in synchronization with the CDB and the other is to query the CDB for all call interrogation to get proper routing procedure. After obtaining the rules, rest of the call is handled normally.

Call Routing Schemes :-

    There are 4 schemes of call routing that support number portability.

1. All Call Query (ACQ) - Most Efficient (No dependency on other network for routing the call, Easy Billing, Minimum Call Set-Up Time, Minimal Impact on Signaling, Impact on network complexity is very less, etc.)
   
2. Query on Release (QoR).
3. Call Dropback.
4. Onward Routing (OR) - Least Efficient. 
   

More Information from Readers are Expected !!!

Thanks
telecomtigers@gmail.com
http://homepageforu.webs.com/

NGN - Next Generation Network

             The general idea behind NGN is that one network transports all information and services (voice, data, and all sorts of media such as video) by encapsulating these into packets, like it is on the Internet. NGNs start making sense when voice, data, video are all in IP format.

              Basically, the core network should have a common service delivery architecture, with any access network hanging off the core.
Some important service characteristics for NGN would be real-time, multi-media communications, more personal intelligence, more network intelligence, more simplicity for users, personal service customization and management.

             It will benefit from its advanced control, management, and signaling capabilities, enabling a much broader array of service types, such as  

• Specialized resource services (provision and management of transcoders, multimedia multipoint-conferencing bridges, processing and storage services),  
• Middleware services (brokering, security, licensing, transactions),  
• Application-specific services (business applications, e-commerce applications, supply-chain management applications, interactive video games), 
  
• Content-provision services (electronic training, information push services).

             Next generation IP networks or NGN IP will be the key enabler of mobility and convergence. This would mean that convergence would not just be limited to wired networks. WLAN too can run voice, data, & video.
            NGN IP would help organizations achieve new levels of enhanced productivity, reduced operational costs, increased operational efficiency and better overall profitability.
            NGN IP would also support new levels of personal mobility, allowing for seamless integration of fixed and mobile networks. And, for enterprises it helps to scale their network architecture and prioritize bandwidth usage, and reduce network management complexities.
           In an NGN environment, almost 60–70% bandwidth would be reserved for data, and as voice would be on the same pipe, it would come almost free. With no additional costs for using voice, the usage of voice services would increase. And it is voice over IP (VoIP) that would be the killer application for NGNs.

Fundamental to Next Generation Networking :-

• Packet-Based Data Transfer.
• Separate control functions for bearer capabilities, calls/sessions and applications/services.
• De-coupling of service provision from the network, and provision of open interfaces.
• Support for a wide range of service applications and mechanisms based on service building blocks (including real-time/streaming/non-real-time services and multi-media).
• Broadband capabilities with end-to-end QoS and transparency.
• Interworking with legacy networks via open interfaces.
• Generalized mobility.
• Converged services between Fixed and Mobile networks.

Issues to be kept in mind while planning for NGN deployment :-

1. Latency (Delay)
2. Jitter
3. Bandwidth
4. Packet Loss
5. Reliability
6. Security
7. Inter-operability

NGN involves three main architectural changes that need to be looked at separately :-

• In the Core Network, NGN implies a consolidation of several (dedicated or overlay) transport networks each historically built for a different service into one core transport network (often based on IP and Ethernet). It implies amongst others the migration of voice from a circuit-switched architecture (PSTN) to VoIP, and also migration of legacy services such as X.25, Frame Relay (either commercial migration of the customer to a new service like IP VPN, or technical emigration by emulation of the "legacy service" on the NGN).
• In the Wired Access Network, NGN implies the migration from the dual system of legacy voice next to xDSL setup in the local exchanges to a converged setup in which the DSLAMs integrate voice ports or VoIP, making it possible to remove the voice switching infrastructure from the exchange.
• In Cable Access Network, NGN convergence implies migration of constant bit rate voice to PacketCable (CableLabs standards that provide VoIP and SIP services).

PacketCable Networks use the Internet Protocol (IP) to enable a wide range of multimedia services, such as Voice over IP (IP telephony), multimedia conferencing, interactive gaming, and general multimedia applications.

NGN Technology Components :-

• NGNs are based on Internet technologies including Internet Protocol (IP) and Multiprotocol Label Switching (MPLS). At the application level, Session Initiation Protocol (SIP) seems to be taking over from ITU-T H.323.
• For voice applications, one of the most important devices in NGN is a Softswitch - a programmable device that controls Voice over IP (VoIP) calls. It enables correct integration of different protocols within NGN. The most important function of the Softswitch is creating the interface to the existing telephone network, PSTN, through Signalling Gateways and Media Gateways.
• Gatekeeper - This was originally a VoIP device, which converted (using gateways) voice and data from their analog or digital switched-circuit form (PSTN, SS7) to the packet-based one (IP). It controlled one or more gateways. As soon as this kind of device started using the Media Gateway Control Protocol, the name was changed to Media Gateway Controller (MGC).
• IP Multimedia Subsystem (IMS) is a standardized NGN architecture for an Internet media-services capability.

SoftSwitch :- It's a central device in a telecommunications network which connects calls from one phone line to another, entirely by means of software running on a computer system. This work was formerly carried out by hardware, with physical switchboards to route the calls.
             It is typically used to control connections at the junction point between circuit and packet networks. A single device containing both the switching logic and the switching fabric can be used for this purpose. however, modern technology has led to a preference for decomposing this device into a Call Agent and a Media Gateway.
            Call Agent takes care of functions like billing, call routing, signalling, call services and so on and is the 'brains' of the outfit. A Call Agent may control several different Media Gateways in geographically dispersed areas over a TCP/IP link.
            Media Gateway connects different types of digital media stream together to create an end-to-end path for the media (voice and data) in the call. It may have interfaces to connect to traditional PSTN networks like DS1 or DS3 ports (E1 or STM1), it may have interfaces to connect to ATM and IP networks and in the modern system will have Ethernet interfaces to connect VoIP calls. The call agent will instruct the media gateway to connect media streams between these interfaces to connect the call.
              In more recent times (i.e., in IP Multimedia Subsystem or IMS), the Softswitch element is represented by the Media Gateway Controller (MGC) element, and the term "Softswitch" is rarely used in the IMS context, but another word of AGCF(Access Gateway Control Function).
             Feature Server, often built into a call agent/softswitch, is the functional component that provides call-related features. Capabilities such as call forwarding, call waiting, and last call return, if implemented in the network, are implemented in the feature server. The feature server works closely with the call agent, and may call upon the media server to provide these services. These features do not require the subscriber to explicitly request them but tend to be triggered within the call handling logic.


More Information from Readers are Expected !!!

Thanks
telecomtigers@gmail.com
http://homepageforu.webs.com/

Location Update Procedure

                 In order to make a mobile terminated call, The GSM network should know the location of the MS (Mobile Station), despite of its movement. For this purpose the MS periodically reports its location to the network using the Location Update procedure.

Location Area (LA)
                A GSM network is divided into cells. A group of cells is considered a location area. A mobile phone in motion keeps the network informed about changes in the location area. If the mobile moves from a cell in one location area to a cell in another location area, the mobile phone should perform a location area update to inform the network about the exact location of the mobile phone.

The  Location Update procedure is performed:

• When the MS has been switched off and wants to become active, or
• When it is active but not involved in a call, and it moves from one location area to another, or
• After a regular time interval.

                     
Location registration takes place when a mobile station is turned on. This is also known as IMSI Attach because as soon as the mobile station is switched on it informs the Visitor Location Register (VLR) that it is now back in service and is able to receive calls. As a result of a successful registration, the network sends the mobile station two numbers that are stored in the SIM (Subscriber Identity Module) card of the mobile station.

These two numbers are :-

1. Location Area Identity (LAI) 
2. Temporary Mobile Subscriber Identity (TMSI). 

The network, via the control channels of the air interface, sends the LAI. The TMSI is used for security purposes, so that the IMSI of a subscriber does not have to be transmitted over the air interface. The TMSI is a temporary identity, which regularly gets changed.

• A Location Area Identity (LAI) is a globally unique number.
• A Location Area Code (LAC) is only unique in a particular network.

Every time the mobile receives data through the control channels, it reads the LAI and compares it with the LAI stored in its SIM card. A generic location update is performed if they are different. The mobile starts a Location Update process by accessing the MSC/VLR that sent the location data.
A channel request message is sent that contains the subscriber identity (i.e. IMSI/TMSI) and the LAI stored in the SIM card. When the target MSC/VLR receives the request, it reads the old LAI which identifies
the MSC/VLR that has served the mobile phone up to this point. A signalling connection is established between the two MSC/VLRs and the subscriber’s IMSI is transferred from the old MSC to the new MSC. Using this IMSI, the new MSC requests the subscriber data from the HLR and then updates the VLR and HLR after successful authentication.


Periodic location update is carried out when the network does not receive any location update request from the mobile in a specified time. Such a situation is created when a mobile is switched on but no traffic is carried, in which case the mobile is only reading and measuring the information sent by the network. If the subscriber is moving within a single location area, there is no need to send a location update request.
A timer controls the periodic updates and the operator of the VLR sets the timer value. The network broadcasts this timer value so that a mobile station knows the periodic location update timer values.
Therefore, when the set time is up, the mobile station initiates a registration process by sending a location update request signal. The VLR receives the request and confirms the registration of the mobile in
the same location area. If the mobile station does not follow this procedure, it could be that the batteries of the mobile are exhausted or the subscriber is in an area where there is no network coverage. In such
a case, the VLR changes the location data of the mobile station to “unknown”.

The Location Update process consists of the following phases

• Request for service; the MS detects that it has entered a new Location Area and requests to update its location. The new MSC/VLR identifies the MS.
• Authentication - The new MSC/VLR requests to the AUC for authentication parameters (SRES, Kc, RAND). Using these parameters the MS is authenticated.
• Ciphering - Using the parameters which were made available earlier during the authentication the uplink and the downlink are ciphered.
• Update HLR/VLR - The new MSC/VLR requests to update the MS location in the HLR. The MS is de-registered in the old VLR.
• TMSI re-allocation - The MS is assigned a new TMSI.

1. The MS detects that it has entered a new Location Area and transmits a Channel Request message over the Random Access Channel (RACH).
2. Once the BSS receives the Channel Request message, it allocates a Stand-alone Dedicated Control Channel (SDCCH) and forwards this channel assignment information to the MS over the Access Grant Channel (AGCH). It is over the SDCCH that the MS will communicate with the BSS and MSC.
3. The MS transmits a location update request message to the BSS over the SDCCH. Included in this message are the MS Temporary Mobile Subscriber Identity (TMSI) and the old Location Area Identification (oldLAI). The MS can identify itself either with its IMSI or TMSI. The BSS forwards the location update request message to the MSC.
4. The VLR analyzes the LAI supplied in the message and determines that the TMSI received is associated with a different VLR (old VLR). In order to proceed with the registration, the IMSI of the MS must be determined. The new VLR derives the identity of the old VLR by using the received LAI, supplied in the location update request message. It also requests the old VLR to supply the IMSI for a particular TMSI.
5. The new VLR sends a request to the HLR/AUC (Authentication Center) requesting the “authentication triplets” (RAND, SRES, and Kc) available for the specified IMSI.
6. The AUC, using the IMSI, extracts the subscriber's authentication key (Ki). The AUC then generates a random number (RAND), applies the Ki and RAND to both the authentication algorithm (A3) and the cipher key generation algorithm (A8) to produce an authentication Signed Response (SRES) and a Cipher Key (Kc). The AUC then returns to the new VLR an authentication triplet: RAND, SRES, and Kc.
7. The MSC/VLR keeps the two parameters Kc and SRES for later use and then sends a message to the MS. The MS reads its Authentication key (Ki) from the SIM, applies the received random number (RAND) and Ki to both its Authentication Algorithm (A3) and Cipher key generation Algorithm (A8) to produce an authentication Signed Response (SRES) and Cipher Key (Kc). The MS saves Kc for later, and will use Kc when it receives command to cipher the channel.  
8. The MS returns the generated SRES to the MSC/VLR. The VLR compares the SRES returned from the MS with the expected SRES received earlier from the AUC. If equal, the mobile passes authentication. If unequal, all signaling activities will be aborted.
9. The new MSC/VLR requests the BSS to cipher the radio channel. Included in this message is the Cipher Key (Kc), which was made available earlier during the authentication.
10. The BSS retrieves the cipher key, Kc, from the message and then transmits a request to the MS requesting it to begin ciphering the uplink channel.
11. The MS uses the cipher key generated previously when it was authenticated to cipher the uplink channel, and transmits a confirmation over the ciphered channel to the BSS.
12. The BSS upon ciphering the downlink channel sends a cipher complete message to the MSC. At this point, we are ready to inform the HLR that the MS is under control of a new VLR and that the MS can be de-registered from the old VLR.
13. The new VLR sends a message to the HLR informing it that the given IMSI has changed locations and can be reached by routing all incoming calls to the VLR address included in the message.
14. The HLR requests the old VLR to remove the subscriber record associated with the given IMSI. The request is acknowledged.
15. The HLR updates the new VLR with subscriber data (mobiles subscriber’s customer profile).
16. The MSC forwards the location update accept message to the MS. This message includes the new TMSI.
17. The MS retrieves the new TMSI value from the message and updates its SIM with this new value. The mobile sends then an update complete message back to the MSC.
18. The MSC requests from the BSS that the signaling connection be released between the MSC and the MS.
19. The MSC releases its portion of the signaling connection when it receives the clear complete message from the BSS.
20. The BSS sends a "radio resource" channel release message to the MS and then frees up the Stand-alone Dedicated Control Channel (SDCCH) that was allocated previously. The BSS then informs the MSC that the signaling connections has been cleared.

More Information from Readers are Expected !!!

Thanks
telecomtigers@gmail.com
http://homepageforu.webs.com/

SS7 Protocol - Signal Units

Hi,
      Different types of Signaling Units used in SS7 Protocols are: -

1. FISU - Fill-In Signal Unit
2. LSSU - Link Status Signal Unit.
3. MSU - Message Signal Unit

FISU - Its a lowest Level Signal Unit, Its generated automatically in both directions on all links as traffic volume decreases. It Provides continuous Error Checking on signaling links when there are no MSUs. It allows SS7 network to maintain its reliability. It contains basic level 2 information only i.e. acknowledgment of signal unit receipt by a remote signaling point.

• Check Sum - It is calculated from the transmitted message by the transmitting signaling point & inserted in the message. On receipt it is recalculated by receiving signaling point. If not the same, the message is corrupt & retransmission is requested.
• Spare - Used as a filler since the LI only uses 6 of the possible 8 bits.
• LI - Indicates length of Signaling Unit (SU). FISU LI=0, LSSU LI=1 or 2, MSU LI=3 to 63. If MSU is larger than 63 octets (bytes) it will not be indicted, max.273 octets.
  
• FIB - Used in error recovery like BIB, When messages are transmitted in error, & the BIB has changed from 1 to 0 or 0 to 1, the FIB will change to match the BIB, when corrupted messages have been successfully retransmitted. If there are no error message, BIB & FIB will have the same value 0 or 1.
• FSN - Contained the sequence number of a transmitted SU, can be between 0-127, or 128 possible SUs in transmit buffer.
• BIB - Indicates the negative acknowledgment, if the bit does not match the FIB bit value, either 0 or 1.
• BSN - Used to confirm the receipt of SUs & to ensure they are received in the order they were transmitted. The BSN value will match that of the last successfully received SUs FSN. Value can be 0-127 or 128 possible SUs in received buffer.
• Flag - It act as a delimiter for SUs. A flag marks the end of the SU & the start of the next SU, Always looks like 01111110.

LSSU - It is used to control Link Alignment. It contains one or two octets of link status information. It indicates the status of a signaling point (e.g. local processor outage) to the remote signaling point.

It has one unique field, the Status Field (SF). The SF can have any one of the six different status indications, those are.

1. Busy (SIB) - Level 2 is busy, or congested at transmitting signaling point(SP). A SP will suspend MSUs when it receives a busy LSSU. If the condition lasts 3-6 sec, Level 3 will be informed of a link failure & begin alignment process.
2. Processor Outage (SIPO) - Transmitting signaling point cannot communicate with Level 3 & 4, possible due to a CPU or total nodal failure. or being manually taken out of service with the canc-slk command.
3. Out of Service (SIOS) - SP cannot transmit or receives any MSUs for the reason other than processor outage. Upon receipt of an SIOS the receiving SP stops the transmission of MSUs & begin transmitting FISUs. It is also sent at the beginning of the alignment process.
4. Out of Alignment (SIO) - Sent when a link has failed, is restored & alignment procedure has been initiated, but proving period parameters have not been met.
5. Normal Alignment (SIN) - Procedure used when there is more than one SLK in the affected linkset. During the alignment process, the slk is looking for 4 successfull normal alignment LSSUs in a 2.3sec. proving period, if it fails it goes out of alignment again.
6. Emergency Alignment (SIE) - Procedure used when there is only 1 slk in a linkset. During the alignment process, the slk is looking for 1 successful emergency alignment LSSU in a 0.6sec. proving period.

MSU - It is used for Call Control, Database query & response, Network Management, Network Maintenance, Routing Labels which consists of an Origination & a Destination point Code.

 
It provides the structure for transmitting all messages types such as ISUP, TUP, TCAP, MAP.
It has 2 unique fields -

1. Service Information Octet (SIO) - It tells level 4 the type of service requested & the type of network message, & the priority of the MSU.

The Service Indicator field tells :-

• Value 0 - indicates a signaling network management message.
• Value 1 - indicates a signaling network test & maintenance message.
• Value 2 - indicates a special signaling network test & maintenance message.
• Value 3 - indicates a SCCP message.
• Value 4 - indicates a TUP message.
• Value 5 - indicates a ISUP message.

The Network type is 2 Bits :

• Value 0 - indicates an International Network.
• Value 1 - indicates a National Network.

 The Message Priority is 2 Bits :
                      Message priority values are from 0-3

• Value 0 - indicates Lowest Priority Message.
• Value 3 - indicates Highest Priority Message.

   2.    Signaling Information Field (SIF) - It has

• The Routing Label of the message (OPC / DPC).
• A Signaling Link Selector (SLS), used to distribute traffic over multiple signaling links within a linkset if available.

More Information from Readers are Expected !!!

Thanks
telecomtigers@gmail.com
http://homepageforu.webs.com/