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快速发展的全球技术市场
面对着今天的挑战以及全球技术市场的快速增长,通信网络的结构和活动转变成了一个聚合网络的基础结构。这个基础设施以信息为基础，包括交换技术、政策基本控制和交叉平台即平台独立。这样的网络平台的目的是建设一个特别的后继的服务质量(QOS)，达成用户想要访问所有服务的要求,减少网络提供者的相关网络运营成本、管理维护，支持所有类型的访问技术,应用程序和服务。建立这样的系统，IMS(IP多媒体子系统) 在设计一个聚合所有这些服务和网络基础设施中扮演着重要的角色，它被认为是下一代蜂窝移动通信技术(NGN)。
由于技术的融合,在未来，他们将需要一个应用程序,可以汇集服务和第三方服务提供商，提供下一代网络(NGN)——蜂窝移动网络运营商提供的网络。网络运营商、第三方服务提供者商将使用这个应用程序添加他们的服务，并且订阅者可以搜索那些他们想认购的服务。
Rapidly growing technological global market
In today’s challenging and rapidly growing technological global market, the behavier and structure of communication networks are changing into a single converged network infrastructure. This infrastructure is based on packet switch technology, policy based control, and cross platform i.e. platform independent. The aim of such network paltform is a particular quality of service (QOS) and access to all services the subscribers wants, and for Network provider’s reduction in the cost related to network operations, management and maintenance and support for all types of access technologies, applications, and services. To built such system IMS (IP multimedia Subsystem) plays a vital role in designing a single converged network infrastructure for all these services and is consider as the Next Generation cellular mobile Technology (NGN).
Due to the technologies convergence, in the future their will be a need of an application program which can bring together services offers in the Next Generation Network (NGN) cellular mobile network by the Network operators, and 3rd party service providers. The network operators, 3rd party service providers will use this application to add their services and the subscribers will use to search service they want to subscribe for.
AIM OF THE PROJECT:
The aim of this project is to develop a unified repository system of services offers in the IMS-Enabled cellular mobile NGN networks. This repository system will provides a searching facility to the subscriber looking for different services and will allow network operators and 3rd party services providers to add i.e. Register their services. The reason is in the future there will be a need of such system due to the revolutionary technology IMS a converged network platform.
PROJECT OBJECTIVES:
The title of this project is “Classification of services offered in IMS-based cellular NGN”, which will focus on the following areas:
Background study of IMS-Enable cellular mobile NGN.
Identification and Classification of services offered in cellular mobile NGN.
Proposed Repository system architecture.
Repository system implementation.
This project is based on the same approach used in IMS-based networks i.e. Converged solution. I hope this project will be useful addition in IMS-based cellular mobile future technologies and will help network operators, 3rd party service providers and subscribers to benefits from this system. For this purpose, I studied in depth IMS-based NGN cellular mobile technology, need of technology, services offered, facilities and benefits. The following diagram describes overview of the overall project
Background study IMS-Based cellular mobile NGN
Services identification and classification cellular mobile NGN
Proposed repository system architecture NGN services
Implementation of the proposed repository system
Figure 1-1: overview of the overall project
PROJECT SCOPE:
This project is a general unified repository system of services such as messaging, voice, video, IPTV, news, general information etc. this system will be helpful for Network operators, 3rd party services providers and the subscribers linked with mobile communication sector.
Literature Review
The Future of mobile network operators is changing due to technological convergence. This is because of some regulatory changes, competition with other operators and fast growing markets. As number of mobile users increasing, per user average income from voice services is decreasing. To cope with this, service providers are trying for long-term and effective income sources. For this purpose they need to quickly develop and launch cost effective new services to keep their existing customers as well as attract new. For Network operators multimedia services are found to be the most attractive source. To provide these services IP-based packet switched technology can be implemented over existing infrastructure for services delivery, which can boost capital expenses and will reduce new services operation cost. For subscriber this will provide high mobility, high quality voice and data services etc, (Motorola, 2005)[1].
In IP-based network presence-enabled services such as instant messaging and video sharing etc, is a trend towards new rising communication tradition. Sharing everyday life activities using any type of devices at any place and any time has changed communication behaviour. For such communication tradition to provide telephony, SMS and MMS etc service to end users, the most important and essential telecom sector support is a global interconnection platform. The success of any new service in the growing markets will require interoperability between different service providers, different networks infrastructures and devices with some global standards. The network operators can take advantage from this tradition, if their infrastructure is built on this successful business Model, (Ericsson, 2007)[3].
Customers are demanding for easy access and use of high level of intelligent services in today “always-on” world for personalise usage, which are not restricted to a specific place, technology and device. A converged multimedia and entertainment technology fulfils user’s demands for these services delivery across all types of access media, technologies and devices transparently, (Nortel Networks, 2006) [2].
IP-based mobile devices with large terminals, high quality display unit, built in camera and other extras resources using different types of high-level applications, and have always-on i.e. connected mode, introducing a completely new communication concept. The most interesting aspect of the next generation technologies is peer-to-peer link between end users to allow them share application experiences such as browsing, video conferencing, push to talk, gaming etc, over IP-based infrastructure, (Poikselka et al, 2004)
Achieving business goal is very hard in unstable emerging mobile markets, particularly a tight competition with new players joining market, offers attractive services on lower price. To stay in the market, Telco can convert to all- IP platforms, which will allow them to deliver stylish, powerful and attractive services to end users. The most interesting and powerful aspect is they can deliver all their existing services such as voice etc and new services as well, (Nokia Siemens Networks, 2009)[4].
From the discussion in the this section we can conclude that a revolutionary technology named IMS (IP Multimedia Subsystem) is considered as a backbone for next generation communication network, because of its converged infrastructure, which is not restricted to a specific network technology, place, device, software, services, network operator and 3rd party services provider etc. The next section contains a precise description of the technology.
IMS (IP MULTIMEDIA SUBSYSTEM):
IMS is a common control network architecture providing access to all services apart from type of media used. It means that different services such as voice, messaging, video, data or any combination is delivered over a single common control plane. Furthermore new services can be delivered without changing common control plane, because everything is controlled by a single common session control protocol SIP (Session Initiation Protocol). This one common control network architecture eliminates the needs of using vendors, operators and 3rd party proprietary based equipments, protocols and applications etc, (Russell, 2008).
According Ericsson (2007), IMS is a converge network architecture combines the best of both telecom industry and the Internet, by implementing quality of service and interpretability of the telecom sector using fast development process of Internet applications. As a single common core and organized infrastructure, IMS can deliver any type of services such as voice, video, or any other combination using standard rules to an IP-based fixed, mobile and cable users. IMS is IP-based core network infrastructure connected to any types of access networks such as GSM, UMTS, CDMA, WiMax etc, provides a converged network services to wireline, cable and wireless end users, (AudioCodes, 2006). Nokia Siemens Network (2009), describe IMS is IP-based long-term future network architecture, which is based on open standard interfaces, interoperability between different vendors and platforms.#p#分页标题#e#
Nortel Networks (2006) explains IMS as a common services platform originally designed to support GSM/UMTS networks but later its popularity and support for all types of provider networks such as CDMA, cable network, wireless networks, internet services and telephone network has made it as future technology. Apart from converged infrastructure, it assures quality of service, boost up revenue and future motivation.
IBM (2009) describes IMS as a system, which makes it possible for service providers to deploy new and powerful multimedia services over a simplified common IP-based network infrastructure, which facilitates the convergence of networks. It will allow an easy transport of a high quality multimedia, voice and data services on personal, workgroup, and enterprise level as will support for Virtual Private Network (VPN), Furthermore it can give quick revenue rise due to its integrated service platform.
The diagrammatical description of IMS Network convergence scenario (1)
The diagrammatical description of IMS Network convergence scenario (2)
IMS HISTORY:
The history of IMS can be described in following lines: [3GPP, http://www.3gpp.org/specs/specs]
1999, the industry forum 3G.IP developed the IMS initial architecture.
2000, the 3GPP working group included IMS as a part in their standardisation work.
2001, 3GPP release 4, all-IP core network and bearer independent core network capabilities were introduced.
2002 3GPP release 5, preliminary IMS services were introduced such as IMS call control and roaming in UMTS, IMS access security, Message compression etc.
2004 3GPP release 6, IMS is enhanced with extra features such as Wireless LAN integration, HSUPA (High Speed Uplink Data Access), Push-To-Talk over cellular (POC) etc.
Mid 2007 3GPP release 7, service identification in IMS, Multimedia telephony service for IMS, improved QOS of service is provided for real time application such as VoIP.
2008 3GPP release 8, IMS centralised service controll, IMS security enhancement, enhanced cable access support etc.
IMS STANDARDS:
In late 1980s Global System for Mobile Communication (GSM) developed by the European Telecommunications Standard Institute (ETSI), (Camarillo & Miguel, 2006). GSM last standard was introduced in 1998, at the same time 3rd Generation Partnership Project (3GPP) was formed by the standardization institutions from Europe, USA, China, Japan and South Korea for specifications and standards of 3rd generation mobile system beyond GSM. Furthermore 3GPP IMS, closely working with ETSI TISPAN (Telecommunication and Internet Converged Services and Protocol for advanced Networking) specification, was created in 2003 and is the bases of next generation network specification and the Multimedia Domain CDMA2000 3GGP2 system, which is based on IMS specification.
The standardization bodies involved in IMS specification and standardization are:
3GPP and ETSI
IETF (Internet Engineering Task Force)
ITU-R (Institute of Telecommunication Radio communication sector)
OMA (Open Mobile Alliance)
3GGP2 (3rd Generation Partnership Project 2)
Why we need IMS?
There are many reasons we need IMS, first its managed QOS for multimedia services, means that it is possible to allocate bandwidth to a media type according to its requirements. Secondly it is a single common protocol for session management that allows all services in a single session, which is not available in traditional IP networks. Thirdly it is interoperability between different platforms, devices and services etc, does not matter who is providing these services. Apart from these, IMS also provides billing (charging) feasibility and subscribers are charged according to the services used, (Russell, 2008).
According Camarillo and Miguel (2006), the aim of IMS is the integration of Internet and cellular technologies to provide Internet services using cellular technologies everywhere at any time. But already many of the Internet services are provided through cellular networks such as web browsing, e-mail, instant messaging etc using a data connection. Apart from this, in IMS all services are provided through packet switched domain instead of circuit switch, which is more efficient data transmission technique. But 3G is also using packet switching techniques and almost all services can be used, which other broadband internet connection such as ISDN, DSL, Cable etc also provide. It means that a user can use VoIP application to establish call using packet switch domain can access all services the internet service provider offers over the internet such as voice, video conferencing and messaging etc., then, why we need IMS?
If 3G users can have all the above-mentioned services through packet switch domain, then the need of IMS is to provide QOS (Quality of Service), charging (Billing) and different services integration facilities. QOS is a major issue in packet switch domain, means that best effort data transmission service is provided without any QOS, which does not guarantee particular amount of bandwidth, packet delay, packet lose etc. for real time application such as VoIP, real time Video etc a particular Quality of service is required otherwise the end parties will experience delay in communication or even impossible to communicate, (Camarillo & Miguel, 2006).
REASONS BEHIND IMS CREATION:
The first reason is establishment of session with a particular QOS for real time application such VoIP and Video conferencing etc.
The second reason is to charge a subscriber session properly. It means that if one subscriber is using multimedia session will send more data need a guaranteed QOS while a subscriber surfing the Internet, sending email etc transmitting less data and even do not need QOS. For operator it is not feasible to charge subscribers using different business model. IMS offers generalise business model based on service invoked by the subscriber. Means IMS informs the operator’s about the services currently in use, allow them to charge a subscriber session (Voice, Video, audio etc) as they want with flat rates, QOS based, Data usage based, time-based or any other type.
The third reason is services integration means platform, vendor, operators, and 3rd party independent services facility. It gives the operator’s freedom of integrating 3rd parties and other services with their existing services they offer, giving a completely new package of services to the subscribers. For example a 3rd party develop a text-to-voice conversion application, which translates incoming message to voice. An operator can integrate this service with the existing services to help blind subscribers. IMS facilitate developers to integrate multi-vender services using standard interfaces based on the Internet protocol removing restriction from operator’s of sticking with a single vender.
Besides from the above-mentioned reasons, the IMS is not restricted to only new services but will also provide all existing and future services the Internet provides. IMS truly combines the Internet and cellular technologies, provides standard interfaces for services integration based on an open standard Internet protocol and technologies. Furthermore all the above services can be provided by non-IMS platform such as a user can have video conferencing using circuit switch domain with acceptable QOS, and web browsing, e-mail etc using packet switch domain (GPRS etc), then why still IMS?
First, IMS is using packet switch domain for all services, But the most interesting feature as compare with non-IMS services is that IMS provide a unified service platform where all services are interrelated, allowing any service to access any aspect of the session. When services are able to access session any aspect in the network, more operations can take place with out sending data over the air interface such as user presence status change, call diverting, and event notification etc. this way the radio channel capacity is reserve to accommodate extra user and allow them to communicate with good QOS.Figure 2.1: 3GPP IMS architecture
Reproduced from Camarillo & Miguel, (2006),IP Multimedia Subsystem
The diagram describes a general architectural overview of the IMS. Always remember that inside IMS only functions are standardized by the 3GPP not Nodes, This makes IMS a collection of functions connected together by standard interfaces. The implementation of IMS depends on the providers, operators, venders etc. They can assign single function to a node or can combined two functions, but most common implantations are single function nodes, (Camarillo & Miguel, 2006).
COMPONENTS INSIDE THE IMS:
Databases:
HSS (Home Subscriber Server) and SLF (Subscriber Location Function):
The HSS is the main database stores user related all information such as subscription, user profile, and is identical to HLR (Home Location Register) in GSM. The information store in the HSS is user authentication, authorization, location, and Subscribed services, allocated servicing CSCF to user etc. during registration process user information is provided to CSCF for multimedia session establishment. If in the network there are more than one HSS due to more subscribers, then SLF is required otherwise with single HSS there is no need of SLF. SLF act as indexing database, used to locate the appropriate HSS for user information to those nodes query with user address, (Camarillo & Miguel, 2006; Ericsson, 2007).
CSCF (Call/Session Control Function):
The CSCF is SIP (Session initiation Protocol) server, which is the primary and vital node in IMS and is responsible to process SIP signaling. In IMS three different nodes P-CSCF, I-CSCF and S-CSCF are used as CSCF.
P-CSCF (Proxy – CSCF): P-CSCF is the first entrance point to get access to IMS networks through user equipment i.e. IMS terminal, the functionality of this node is the exchange of messages between user equipment and IMS network i.e. Requests and Reponses. During registration user equipment is connect to a single P-CSCF, and for the whole process P-CSCF is the same i.e. unchanged. The operations of P-CSCF are Security, Authentication, Messages compression and decompression, distribution of user identity in the network, (Camarillo & Miguel, 2006; Ericsson, 2007).
I-CSCF (Interrogating – CSCF): I-CSCF act as a gateway and in the administrative domain of the IMS it is situated at the edge of the network, The I-CSCF address is in the DNS (Domain Name System) of the domain. The role of I-CSCF is forwarding request and response messages to the correct destination network based on the user information. This information is provided by SLF, retrieved from S-CSCF (Location) and from HSS (Subscription). Furthermore I-CSCF is connected to HSS and SLF through standard interfaces based on Diameter protocol. Apart from that to protect network I-CSCF hides domain information from other operators by encrypting SIP sensitive messages, (Camarillo & Miguel, 2006; Ericsson, 2007).
S-CSCF (Serving – CSCF): S-CSCF act as a central and key node in IMS signaling plane. Apart from the SIP signaling functionality, it controls the session imitated by the subscriber. To control session, it registers the location of the subscriber and provides this information to nodes involve in the session i.e. application server, HSS etc, and this way the subscriber session is maintained. S-CSCF helps HSS and SLF during registration to authenticate and retrieve subscriber services profile. Another function of the S-CSCF is SIP signaling routing i.e. to Route the user request for services to the correct Application servers, (Camarillo & Miguel, 2006; Ericsson, 2008).
AS (Application Server): The AS is multipurpose SIP application server executes all applications and services in the IMS. AS use both SIP and Diameter protocol and is connected to CSCF (Call Session Control Function). In IMS there are different AS such as Application, contents delivery, video conferencing, presence server, and can behave as SIP user agent, SIP user agent, SIP redirect server etc. in the AS a service identifier identify services in the IMS, it is possible to merge services from different SIP application server and provide user an integrated/Unified service, (Camarillo & Miguel, 2006; Ericsson, 2007; Ericsson, 2008).
BGCF (Breakout Gateway Control Function): the BGCF serve as a gateway when routing is required based on telephone number to other operator’s network. When user in the IMS initiates a session and the session is with user in circuit switch network such as PSTN, PLMN (Public Land Mobile Network) etc then BGCF is use. The BGCF is only communicating with another network BGCF, for security, (Camarillo & Miguel, 2006; Ericsson, 2007).
MRF (Media Resource Function): the responsibility of MRF in the home network is the supply of media source for running services such as announcement, codec conversion, mixed media stream, and conferencing etc. there are two types of MRF used in IMS, MRFC (Media Resource Function Controller) and MRFP (Media Resource Function Processer). MRFP administers media related all functions such as Conferencing, Announcement, tone detection, mixed media etc. while MRFC is a controller control resources i.e. media stream in the MRFP through H.248 interface, (Camarillo & Miguel, 2006; Ericsson, 2007).
SGW (Signalling Gateway): the function of SGW is conversion of lower layer protocols between CS (Circuit switch i.e. PSTN) and IMS in the singling plane. To transport over IP, SGW replaces lower layer protocol MTP (Message Transport Part) with SCTP (Stream Control Transmission Protocol). The reason is to convert ISUP (ISDN User Part) or BICC (Bearer Independent Call control) over MTP in circuit switch into ISUP or BICC over SCTP/IP.
(Camarillo G & Miguel A., 2006)
MGCF (Media Gateway Control Function): The MGCF is the core node of circuit switch gateway i.e. PSTN in IMS. The function of MGCF is media resources control in MGW (Media Gateway) when traffic flow is between Circuit switch (PSTN) and IP (Packet Switch) network.
Between MGCF and MGW ITU-T H.248 protocol is used. MGCF also performs protocol translation by mapping SIP (IMS call control protocol) to ISUP or BICC (Circuit switch call control protocols) over IP, (Camarillo G & Miguel A., 2006), (Ericsson AB, 2007).
MGW (Media Gateway): The function of MGW is internetworking between different media transport format used in circuit switch i.e. PSTN and IMS. The internetworking involves sending and receiving over RTP/UDP/IP (Real Time Protocol/ User Datagram Protocol/ Internet protocol) on IMS side and over TDM (time Division Multiplexing) on circuit switch side i.e. PSTN side. Apart from that it also performs transcoding if required for terminal.
(Ericsson AB, 2007; Camarillo G & Miguel A., 2006).
Protocols in IMS:
SIP (Session Initiation Protocol): SIP is developed by IETF (Internet Engineering Task Force) and selected by the 3GPP as a key signaling protocol for the IMS network. It is designed based on the two well known and the most popular protocol used on the internet the SMTP (Simple Mail Transport Protocol) and HTTP (Hypertext Transfer Protocol). The function of SIP is control over user session such as session establishment, maintenance, and termination and services used such as Voice, Video, and Messaging etc. apart from that SIP is capable of providing end-to-end session establishment between users. The reason behind SIP used in IMS is it is a single, flexible, secure, and robust protocol allowing fast and easy development and deployment of new services and functionalities.
(Camarillo & Miguel, 2006;Ericsson AB, 2007; Russell .T, 2008)
Authentication Authorization and Accounting (AAA) Protocol:
The Diameter uses AAA as a base protocol, the diameter is an enhancement to the RADIUS (Remote Authentication dial-In User Service) used over the internet to authenticate and authorize remote user using the authentication server. The SIP application servers, S-CSCF, I-CSCF use diameter when communicating with HSS for user information. The Diameter is more secure, has control over session and uses reliable protocol TCP (Transmission Control Protocol) or SCTP (Stream Control Transmission Protocol) for transport.(Camarillo & Miguel, 2006;Ericsson AB, 2007).
H.248 Media Control Protocol: The H.248 protocol is developed by ITU-T and IETF, used by the signaling nodes in media plane such as MGCF (Media Gateway Control Function) and MRFC (Media Resource Function Controller) to control media resources and function in MGW (Media Gateway) and MRFP (Media Resource Function Processor), (Camarillo & Miguel, 2006;Ericsson AB, 2007).
IPv6: The IPv6 is an advanced and the latest network layer protocol used in today’s network and will replace IPv4 in the future. The IMS was designed to use IPv6 as network layer protocol, because IPv6 has more futures, address space and other enchantment as compare with IPv4. IMS also support IPv4 and private addresses in IPv4, because most of the internet devices use IPv4 as a network layer protocol, (Ericsson AB, 2007).
H.248 Media Control Protocol: The H.248 protocol is developed by ITU-T and IETF, used by the signaling nodes in media plane such as MGCF (Media Gateway Control Function) and MRFC (Media Resource Function Controller) to control media resources and function in MGW (Media Gateway) and MRFP (Media Resource Function Processor)[6], [3].
IPv6: The IPv6 is an advanced and the latest network layer protocol used in today’s network and will replace IPv4 in the future. The IMS was designed to use IPv6 as network layer protocol, because IPv6 has more features, address space and other enchantment as compare with IPv4. IMS also support IPv4 and private addresses in IPv4, because most of the internet devices use IPv4 as a network layer protocol [3].
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