Mobility Management in MAP

Mobility management happens to be a very important feature in MAP ( Mobile Application Part ).
This is how Wikipedia explains mobility management.
"The aim of mobility management is to track where the subscribers are, allowing calls, SMS and other mobile phone services to be delivered to them."

Mobility management is an essential feature because as the person who is accessing the mobile service moves around, the service should remain.Mobility management in MAP can be further broken
into five more sections.

These are

• Location management
• Handover MSC-MSC during a call
• Authentication and security
• IMEI - mobile equipment id queries
• Subscriber management

Location management is mainly about location updates of the subscribers.

The above flow shows how location management is done in MAP.

SendIdentification operation : used by the new MSC/VLR that sees a
new mobile in its area to request information about the user from the
previous VLR.
UpdateLocation operation :to tell about the change of
responsibility to the HLR of that user once the new VLR takes responsibility
CancelLocation operation : This is for the old VLR to let it know that it can remove its record of the user from its database.
PurgeMS operation : VLR looses track of a mobile it was responsible for. The mobile’s battery may have gone flat or mobile was switched off.

Handover MSC-MSC during a call

When the mobile user keeps moving during a call, the MSC that he is connected to also keeps changing, this needs to be handled also.

Security Operations

Security is assured in MAP by checking the IMEI which is unique for a phone.

Subscriber Management

This is handled using commands such as InsertSubscriberManagement and DeleteSubscriberManagement.As and when the subscribers join and leave services
the stored details in the HLR and VLR.

MAP

The purpose of MAP is to provide all the added signaling functionality required for mobility management in core networks and for several services.MAP has a specification of about 1000 pages.MAP has gone through many phases and releases.MAP works in between many network elements.MAP implements operations as well.

The operations implemented by MAP can be categorized as Mobility management,
Supplementary Services, Call handling, Short messaging, O&M, PDP context
and (Geographical) Location services. The main operation is mobility management.

In the MAP service model, there are two roles called MAP service user and MAP service provider.These can be taken by network elements MSC or HLR in exchange.HLR is the most
important network element when referring to MAP.

MAP communications (when an application is using MAP)

MAP_OPEN : to open a dialogue with the remote element
MAP_CLOSE : to close the dialogue.
MAP_DELIMITER : application decides that all components are in place for the actual communication

MAP_U_ABORT : abort a MAP service (by service user)
MAP_P_ABORT : abort a MAP service (by service provider)
MAP_NOTICE : MAP service provider can notify the user about something without affecting the dialogue

USSD

The most basic introduction to USSD would be when you dial a certain number (#123#) and access a certain menu and select service, you are accessing a USSD menu. Eg: when a Etisalat user dials #141# , he accesses the Appzone developed by hSenidMobile. Currently, USSD services are spreading awareness into the community very fast as it is accessible through even the most basic phones.

USSD stands for Unstructured Supplementary Service Data. Wikipedia defines USSD as “ a protocol used by GSM cellular telephones to communicate with the service provider's computers. “
The difference between USSD and SMS include that the SMS uses store and forward method of message delivery. Short Message is delivered first to SMSC which will try to deliver the message to recipient. So SMS does not guarantee that message will be delivered instantly. USSD information is sent from mobile handset directly to application platform handling service. USSD is very user-friendly as well. If a particular user doesn’t want to visit all the menus and get the service, he can put the numbers and request the service in one dialing as well. (eg : *109*72348937857623#)

What happens when looking at USSD in a more technical perspective is..
• a user requests a service by entering a short code (e.g. *121* 676#) on his mobile phone.
• This code is passed across the mobile network to the USSD gateway and routed to the application.
• The application sends the response back to the subscriber through the USSD Gateway within the same USSD session.

One business sector which has rapidly improved with USSD is micro payment market. Users can transfer money from their mobile prepaid and post paid account to other mobile accounts. There will be a service number associated with it. When the user presses the number and dials, he will be presented with menus where he has to enter the amount and the mobile number to which the money needs to be transferred.

USSD offers many benefits for subscribers such as user-convenient, menu-based direct access from the mobile phone keyboard.Fast response time to service requests and easy access to value-added services. From the operators’ perspective, USSD reduces operational costs and increases ARPU by offering interactive services to all the customers.

INAP and Intelligent Networks

INAP stands for intelligent network application part protocol.

INAP is the signaling protocol used in Intelligent Networking. A total functionality of the IN has been defined and implemented in digestible segments called capability sets . There have been CS – 1 , CS 2 etc.CAMEL Application Part (CAP) is a derivative of INAP. IN is a network architecture intended both for fixed as well as mobile telecom networks. It allows operators to differentiate themselves by providing value-added services in addition to the standard telecom service. These differentiated services include home area discounts and premium rate calls.


There are mainly four planes in Intelligent Network Conceptual Model.


The Service Plane (SP): This plane is of primary interest to service users and providers. It describes services and service features from a user perspective.
The Global Functional Plane (GFP): The GFP is of primary interest to the service designer. It describes units of functionality, known as service independent building blocks (SIBs)
The Distributed Functional Plane (DFP): This plane is of primary interest to network providers and designers. It defines the functional architecture of an IN-structured network in terms of network functionality.
The Physical Plane (PP): Real view of the physical network. The PP is of primary interest to equipment providers.

If we look at a definition of INAP, INAP is a signaling protocol between a service switching point (SSP), network media resources (intelligent peripherals), and a centralized network database called a service control point (SCP).


To understand this definition, it might be required to look into terms separately,
Service switching point (SSP) : Provides the switching functionality and detects special conditions during call processing. Intelligent peripherals provide resources such as customized and concatenated voice announcements, voice recognition.Service Control Point (SCP) main functions are processing SSP requests and issuing responses.

IMS Benefits

As you will already notice, I have given an introduction to IMS in a previous blog post.
This is to stress on the business benefits. We all know technology, if it does not
facilitate any kind of benefits will not be very useful.

So IMS basically means the integration of internet technologies and cellular technologies.
But we all know , that even today it is integrated! Many of us access internet services through
the mobile. Surfing webpages, chatting, checking mail... the list of appealing services offered in the internet goes on. What the mobile offers is ubiquitous access.

Then WHY do we need IMS ? If ubiquitous access to internet services are already there ?

There are three main reasons for IMS existence.

1 - Quality of service

IMS offers a predictable , enjoyable experience. The skype call we take today undergo so many
ups and downs in quality. But using IMS, this quality will be predictable and consistent.

2 – Specific charging mechanisms

Currently the operators charge based on the number of bytes transferred, it is not recognized by the operator what service the user is using. With IMS, the operator will be able to recognize whether the user is having a video call , instant message etc.
The operator will be able to charge more specifically.
Eg : In a video call , the operator might charge based on the duration.
In an instant message exhange, the operator could charge based on the number of messages.

3 - Integration of services

IMS offers standardized interfaces and functionalities. This offers a high level of flexibility and operators don’t have to be locked into one vendor. For example, if the operator already has voice message recording solution and a third party comes up with a text to speech capability, the operator would be able to integrate them and offer a new service for the blind users.

This flexibility allows an operator to offer better services.The business benefits are also immense due to these three main reasons.

- The users will be able to enjoy more services because the operator is not locked
into one vendor.
-Users can enjoy better quality in services.
-As IMS , has a layered architecture, as the market trends change, it will be able to change irrespective of the lower layers.

I hope this post makes it clear as to why IMS is still important even though
internet services are already available through the cellular world.

DRBD - Distributed Replicated Block Device

This is a distributed storage system for the Linux platform. It consists of a kernel module, several userspace management applications and some shell scripts. DRBD is normally used on high availability (HA) clusters.

In very simple terms what happens is DRBD takes over the data, writes it to the local disk and sends it to the other host. Then on that second host, it takes it to the disk there. However, the reads are always carried out locally.

The main point is carrying out the work without the user being affected of any failure.If the primary node fails, the services will be carried out on the secondary host. If the failed node, comes again it has to take the backups from the secondary node.The resynchronization will happen on the failed nodes.

DRBD works on top of block devices.

Fully synchronous

Mirroring can be done tightly coupled. That means that the file system on the active node is notified that the writing of the block was finished only when the block made it to both disks of the cluster.Synchronous mirroring is the right choice for HA clusters.

Asynchronous

Asynchronous means that the entity that issued the write requests is informed about completion as soon as the data is written to the local disk.Asynchronous mirroring is necessary to build mirrors over long distances.

DRBD also offers some advantages over shared cluster storage.

- Shared storage resources usually introduce a single point of failure in the cluster setup. In DRBD, issues like this don't exist as the cluster resource data is replicated.

-Shared storage resources may face situations where both cluster nodes are still alive, but lose all network connectivity between them. In this kind of situation, each cluster node will assume that it is the only node in the cluster. DRBD reduces this problem by keeping two replicated sets.

IP multimedia Subsystem

IMS stands for IP Multimedia Subsystem. It is a new architecture based on new concepts, new technologies, new partners and ecosystem. IMS provides real-time multimedia sessions (voice session, video session , conference session, etc) and non real-time multimedia sessions (Push to talk, Presence, instant messaging) over an all-IP network. It targets convergence of services supplied by different types of networks like fixed, mobile, Internet.

The idea is to integrate mobile / fixed with internet technologies.IMS is different networks that inter operate due to the roaming agreements of any IMS provider.

IMS enables the service provider to offer
- Real-time and non real-time communication services
- Mobility of services and mobility of users
- Multiple sessions and services simultaneously over the same connection

The main concepts that have been considered in the design of IMS are explained below.

The most fundamental thing is that the client needs to have IP connectivity.(IPv6 needs to be used). Access independence is needed so that IMS services can be provided over any IP network.Ensuring the quality of services is done through a terminal negotiating its capabilities and expressing QoS requirements through a SIP set up or modification procedure. IP Policy control to ensure the authorization of the bearer traffic.Secure communication can be requested when engaging in a session and IMS assures security as the corresponding GSM / GPRS networks.Roaming facilities allow the user to enjoy the services even though he may be out of the home network.

IMS is the future for IP multimedia telephony.

INAP - Intelligent Network Application Part

The INAP stands for Intelligent Network Application Part. It allows for the implementation of carrier-grade, signaling infrastructure targeted to the world wide fixed telephony market. It is a signaling protocol between a service switching point (SSP), network media resources and a centralized network database called a service control point (SCP). The SCP consists of operator or 3rd party derived service logic programs and data. Through INAP, operators have gained independence from the software features offered by switch vendors. With intelligent network, operators are able to implement value added services giving them competitive advantages in the market.

Services that can be defined with INAP include:

• Single number service: one number reaches a local number associated with the service
• Personal access service: provide end user management of incoming calls
• Disaster recovery service: define backup call destinations in case of disaster
• Do not disturb service: call forward
• Virtual private network short digit extension dialing service

Following are some short descriptions on relevant terms.

Service Switching Point (SSP) is a physical entity in the Intelligent Network that provides the switching functionality. SSP is also the point of subscription for the service user.

Service Control Point (SCP) authenticates information from the service user, processing requests from the SSP and issuing responses.

Intelligent Peripheral (IP) provides resources. These may include customized and concatenated voice announcements, voice recognition, and contains switching matrix to connect users to these resources.

Service Management Point (SMP) performs service management control, service provision control, and service deployment control.