 The importance of emulation and simulation can be best understood if We were to look at the services which we want to migrate to NGN or The NGN based services which we want to Import to the legacy network This is actually the change of perspective So we look at the migration or evolution from the emulation and simulation perspective We'd consider some options and those options are going to Necessitate the adaption of some functionality and we'd look at the architecture that realizes so as for the implementation the classical Valuated services in PSTN and particularly the ISDN such as the caller line identification and its presentation or its Restriction then call waiting forwarding barring etc Are the features which we want to be to see in NGN as well? At the same time the engine services could be provided to existing PSTN and ISDN services So as far as the emulation is concerned It is a step that encourages Existing services and capabilities to be provided to PSTN ISDN based migration to NGN environment This involves IP enablement Such IP enablement is implemented by the call server but if We are looking at the NGN Services, which we want to provide to PSTN and ISDN But not all classical services may be opted for we would go big time and we'll replace the core Transit exchanges with the IMS Multimedia system in order to realize the simulation or the emulation emulation being more rudimentary or primitive and simulation being more radical the functions which need to be adapted are usually modified using the adaptation functions on both the sides number one On one side that is on the non IP side The IP Multimedia Services are provided for instance using session initiation protocol and then on the other side that is towards the Primitive side we use simulation and emulation So what we are doing is the adaptation is taking place on the user equipment side or the last mile site and Adaptation is equally taking place on the core site for adapting the Services and the functions using simulation The user is going to receive regular engine services like a Typical engine user which is using engine compliant or engine compatible user interface For that We need to install residential gateways in Customer premises, so we would require to have some kind of specific CPE customer premises equipment as for emulation is concerned since we are interested in Ensuring that the legacy services are provided the user receives a standard services and Some additional engine services here the access gateway Implements the Responsibility of adaptation functions and it is on the network side, so it means on the core side The engine providers premises are going to host the access gateway, which will make sure that engine becomes interoperable With the Classical network So let's look at the architecture for simulation and emulation together the complete architecture of PST and ISTN integration Into the NGN either using simulation or emulation Let's look at this figure here. We have NGN carriers A and B, but A is the reference architecture Carrier that we are going to look at to have a better understanding of emulation and simulation as for the non NGN IP networks are concerned or the Traditional PSTNs are concerned. We look at those only briefly. Let's start from The left-hand side on the left-most side. We have user equipment such as a Telephone or typical terminal for Making and receiving calls using ADF one it is going to be simulating the NGN to the user equipment of course the user to network interface as defined in the NGN architecture would be the bridge between the ADF one and the user equipment ADF two that implements emulation is going to allow the user equipment to use NGN services or have access to the NGN architecture both of these Telephones or the primitive terminal equipment are using the Legacy interface it means from their perspective there isn't much change But the ADFs Through adaptation are making sure that this translation to and from NGN takes place smoothly so the user to network interface for simulation is Implementing the VoIP and SIP based services. You can see at the top. We have IP based user equipment That is very smoothly Implementing the user to network interface by directly using VoIP and SIP Let's look at the Non-NGN based IP network here also using VoIP and SIP is possible But having access to the complete suite of services in NGN is not possible And then we have the public land mobile network below here. We have circuit switched voice and Integrated services user part which is going to be connected to the NGN by the network to network interface so it means the NNI allows different networks to be interoperable, but if we really want the Devices to become compatible with NGN. We need to emulate or simulate the services as in NGN