21-06-2014, 03:00 PM
4G TEHNOLOGY-A SENSATION
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Abstract
This paper describes an architecture for differentiation of Quality of Service in heterogeneous wireless-wired networks. This architecture applies an “all-IP” paradigm, with embedded mobility of users. The architecture allows for multiple types of access networks, and enables user roaming between different operator domains. The overall 4G architecture discussed in this paper is IPv6-based, supporting seamless mobility between different access technologies. Mobility is a substantial problem in such environment, because inter-technology handovers have to be supported. In our case, we targeted Ethernet (802.3) for wired access; Wi-Fi (802.11b) for wireless LAN access; and W-CDMA - the radio interface of UMTS - for cellular access.The architecture is able to provide quality of service per-user and per-service An integrated service and resource management approach is presented based on the cooperative association between Quality
INTRODUCTION
WIRELESS COMMUNICATION
A wireless network is an infrastructure for communication “through the air”, in other words, no cables are needed to connect from one point to another. These connections can be used for speech, e-mail, surfing on the Web and transmission of audio and video. The most widespread use is mobile telephones. Wireless networks are also used for communication between computers. This note focuses on ways to set up wireless connections between computers. It gives a basic overview without becoming too technical. It will help to determine whether a wireless network might be a suitable
2 AN ALL-IP 4G NETWORK ARCHITECTURE
The overall 4G architecture discussed in this paper is IPv6-based, supporting seamless mobility between different access technologies. Mobility is a substantial problem in such environment, because inter-technology handovers have to be supported. In our case, we targeted Ethernet (802.3) for wired access; Wi-Fi (802.11b) for wireless LAN access; and W-CDMA - the radio interface of UMTS - for cellular access (Fig. 1). With this diversity, mobility cannot be simply handled by the lower layers, but needs to be implemented at the network layer. An "IPv6-based" mechanism has to be used for interworking, and no technology-internal mechanisms for handover, neither on the wireless LAN nor on other technology, can be used. So, in fact no mobility mechanisms are supported in the W-CDMA cells, but instead the same IP protocol supports the movement between cells. Similarly, the 802.11 nodes are only in BSS modes, and will
PROVIDING QUALITY OF SERVICE
The design principle for QoS architecture was to have a structure which allows for a potentially scalable system that can maintain contracted levels of QoS. Eventually, especially if able to provide an equivalent to the Universal Telephone Service, it could possibly replace today's telecommunications networks. Therefore, no specific network services should be presumed nor precluded, though the architecture should be optimised for a representative set of network services. Also, no special charging models should be imposed by the AAAC system, and the overall architecture must be able to support very restrictive network resource usage. In terms of services, applications that use VoIP, video streaming, web, e-mail access and file transfer have completely different prerequisites, and the network should be able to differentiate their service. The scalability concerns favour a differentiated services (DiffServ) approach [5]. This approach is laid on theassumption to control the requests at the borders of the network, and that end-to-end QoS assurance is achieved by a concatenation of multiple managed entities. With such requirements, network resource control must be under the control of the network
Service and Network Management in Mobile Networks
Our approach for 4G networks and to service provisioning is based on the separation of service and network management entities. In our proposal we define a service layer, which has its own interoperation mechanisms across different administrative domains (and can be mapped to the service provider concept), and a network layer, which has its own interoperation mechanism between network domains. An administrative domain may be composed of one or more technology domains. Service definitions are handled inside administrative domains and service translation is done between administrative domains [6]. Each domain has an entity responsible for handling user service aspects (the AAAC system), and at least one entity handling the network resource management aspects at the access level (the QoS Broker). The AAAC system is the central point for Authentication, Authorization and Accounting. When a mobile user enters the network, the AAAC is supposed to authenticate him. Upon successful authentication, the AAAC sends to the QoS Broker the relevant QoS policy information based on the SLA of the user, derived from his profile. From then, it is assumed that the AAAC has delegated
Implicit "Session" Signalling
In this architecture, each network service being offered in the network is associated to a different DSCP code. This way, every packet has the information needed to the network entities to correctly forward, account, and differentiate service delivered to different packets. After registering (with the AAAC system) a user application can “signal” the intention of using a service by sending packets marked with appropriate DSCP. These packets are sent in a regular way in wired access networks, or over a shared uplink channel used for signalling in W-CDMA. This way of requesting services corresponds to implicit signalling, user-dependent, as the QoS Broker will be aware of the semantics of each DSCP code per each user (although typically there will be no variation on the meaning of DSCP codes between users). Thus QoS Broker has the relevant information for mapping user-service requests into network resources requirements and based on this information configures an access router.A novel concept of “session” is implemented: the concept of a “session” is here associated with the usage
3 Network services offer
Services will be ofered a the network operator independently on the user applications, but will be flexible enough to support user applications Each offered network service will be implemented with one of the three basic DiffServ per-hop behaviours (EF, AF, or BE), with associated bandwidth characteristics. Table 1 lists the network services used in the tests. The network services include support for voice communications (e.g. via S1) and data transfer services. Delay, delay jitter and packet loss rate are among the possible parameters to include in the future, but no specific control mechanisms for these parameters are currently used. The services may also be unidirectional or bi-directional. In fact, the QoS architecture can support any type of network service, where the only limit is the level of management complexity expressed in terms of complexity of interaction between the QoS Brokers, the AAAC systems and the
Registration and Authorisation
The Registration process (Figure 2) is initiated after a Care of Address (CoA) is acquired by the MT via stateless auto-configuration, avoiding Duplicate Address Detection (DAD) by using unique layer-2 identifiers [7] to create the Interface Identifier part of the IPv6 address. However, getting a CoA does not entitle the user to use resources, besides registration messages and emergency calls. The MT has to start the authentication process by exchanging the authentication information with the AAAC through the AR. Upon a successful authentication, the AAAC System will push the NVUP (network view of the User Profile) to both the QoS Broker and the MT, via the AR. Messages 1 to 4 on Figure 2 detail this process. The same picture shows how each network service is authorized (messages 5 to 8). The packets sent from the MT with a specific DSCP implicit signal the request of a particular service, such as a voice call (supported by network service S1, as in Table 1). If the requested service does not match any policy already set in the AR (that is, the user has not established a voice call before, e.g.), the QoS attendant/manager at the AR interacts with the QoS Broker that analyses the request and authorises the service or not, based on the User NVUP (Network View of the User Profile) and on the availability of resources. This authorisation corresponds to a
Handover with QoS guarantees
One of the difficult problems of IP mobility is assuring a constant level of QoS. User mobility is assured in our network by means of fast handover techniques in conjunction with context transfer between network elements (ARs - old and new – and QoS Brokers).
When the quality of the radio signal in the MT to the current AR (called “old AR”, AR1) drops, the terminal will start a handover procedure to a neighbouring AR (called “new AR”, AR2) with better signal and from which it has received a beacon signal with the network prefix advertisement. This handover has to be completed without user perception, when making a voice call, e.g.. For achieving this, the MT will build its new care-of-address and will start the handover negotiation through the current AR, while still maintaining its current traffic. This AR will forward the handover request to
CONCLUSION
We presented an architecture for supporting end-to-end QoS. This QoS architecture is able to support multi-service, multi-operator environments, handling complex multimedia services, with per user and per service differentiation, and integrating mobility and AAAC aspects. The main elements in our architecture are the MT, the AR and the QoS Brokers. We discussed the simple interoperation between these elements and depicted the overall QoS concept. With our approach, very little restrictions are imposed on the service offering. This architecture is currently being evolved for large testing in field trials across Madrid and Stuttgart. Being an architecture specially targeted to support real time communications over packet networks, the network elements configuration must be well dissected. The simulation study summarized in the paper was a valuable input to the QoS Broker implementation and policies design, providing simple heuristics to properly configure the access routers to achieve the best possible performance. The schedulers configuration on the core routers was also determined through the results of this simulation study. This architecture still has some shortcomings, though, mostly due to its diffserv orientation. Each domain has to implement its own plan for mapping between network service and a DSCP, and thus, for inter domain service provision, it is essential a service/DSCP mapping between neighbouring domains. Furthermore, an adequate middleware function is required in the MT, to optimally mark the packets generated by the applications and issue the proper service requests, which requires extensions in current protocol stacks