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services are provided almost solely by operators themselves.It is expected in 46 that different operators cooperate to offerservices and applications over heterogeneous accessnetworks.3. System Concept:The scope of 46 systems will range from wirelesstransmission mechanisms up to the services visible to the enduser [1][2]. Abstraction layers consists of transmissionplatform, networking platform, middleware platform (withservice support) along with application and services. Eachlayer can be configured separately and independently viaconfiguration interfaces. These interfaces are used to eitherparameterize existing elements of each layer or to add,exchange or remove elements, possible due to well-definedinterfaces supported by each element. Figure 2 shows 46-sytem architecture with different interfacing layers.

Fig. 2. 46 System ArchitectureAn abstraction layer is a conceptual home for several openplatforms providing actual computational behavior. With thisconcept one can achieve adaptability can in the systemarchitecture of 46 systems. In mobile networking there isneed of specific and possibly medium dependent interfacesbetween the layers. Cross-layer interfaces define API'Sbetween different layers, which exchange the informationbeyond the standard interfaces between the layers. Design ofmiddleware layer plays crucial role to provide effortlessdevelopment and provisioning of new and changed services.From the point of view of the system operator, the

middleware platform must support high flexibility to achievean unproblematic maintenance and evolution.3.1. Network Resident Middleware:Middleware abstraction layer is represented by threeplatforms-Local execution platform, Distributed processingplatform and Service support platform. Figure 2 showsgeneral dependencies between the platforms and theircomponents. The local platform is used to add or removecomponents according to the application. The distributedprocessing platform provides an abstraction for interactionbetween different system ports residing either on differentdevice or the same device. The service support platformoffers session semantics to any service requesting.3.2. Middle Resident Middleware:Mobile resident middleware must be reconfigurable. It mustbe adaptable with respect to extension elements of particularplatforms or the addition or removal of entire platforms,depending on device characteristics, user profiles and patternsand also the software requirements of the client resident partof services.3.3. Adaptable networking platform:In order to enhance existing network nodes and terminals newtechnologies like software radio will be introduced. Softwaredefined radio technologies in reconfigurable terminals willadd unprecedented flexibility to add new functionality.4. Challenges:Although 4G offers revolution in existing mobilecommunication system, still the implementation of it hasraised few challenges among the designers [1][2].4.1. Multimode user terminals:To design a single user terminal that can operate in differentwireless networks and to overcome the design problems suchas limitations in device size, cost, and power consumption,Software radio is one of the best solutions offered so far. Thecurrent software radio technology is not completely feasiblefor all the existing wireless networks. We require multipleanalog sections, which increases complexity and also size ofthe system [2].4.2. Wireless system discovery:Heterogeneous wireless systems across protocols areincompatible with each other. In order to overcome thischallenge Open To Air (OTA) downloading approach isproposed [2]. In this system multitude user terminalsconstantly monitor a predefined broadcasting channel tocheck for available networks. Once they detect a newavailable network, system will download that module. Westill need to solve problems such as long downloading timeand also the slow speed.

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4.3. Wireless system selection:Every wireless system has its unique characteristics and aparticular role[1][2]. The proliferation of wirelesstechnologies complicates the selection of the most suitabletechnology for a particular service at a particular time andplace.The best possible solution for this type of challenge is toselect the wireless system according to the best possible fit ofuser QOS requirements, available in the network resources.4.4. Terminal mobility:To locate and update the locations of the terminals in varioussystems is one of the challenges faced by designer, along withthis performing horizontal and vertical handoff withminimum handover latency and packet loss is the crucial partin the design [2]. To overcome this problem some fasthandoff mechanisms are used.4.5. Network infrastructureand QOS support:To integrate the existing non-IP based systems, and to provideQOS guarantee for end-to-end services that involves differentsystems is another problem. In order to solve his problem aclear and comprehensive QOS scheme for UMTS system hasbeen proposed. This scheme also supports interworking withother common QOS technologies [2].4.6. Security:For any system, security plays very important role. Theheterogeneity of wireless networks complicates the securityissue [2]. Dynamic reconfigurable, adaptive and lightweightsecurity mechanisms should be developed.4.7. Fault tolerance and survivability:In order to minimize the failures and their impacts in anylevel of tree-like topology generally used in wireless networksforms a big challenge among the designers [2]. Failure of anyof the nodes due to some reasons all the services of theremaining dependent nodes get blocked.4.8. Multi operators and billing system:4G architecture is a collection of heterogeneous networksthose are previously working independently to each other's.Billing scheme offered by them was also different. So tocollect, manage and store the customers accountinginformation from multiple service providers will be the mainchallenge.4.9. Personal mobility:It is a really tough challenge to design new platform toprovide seamless personal mobility to users withoutmodifying the existing servers in heterogeneous systems.5.Research:Presently lots of universities are working to develop anintegrated network of all heterogeneous networks connected

with IPV6 network platform [1]. Automatic systems formobility are being developed along with concepts likesoftware defined radio being enhanced. Leading SoftwareCompany Math works recently developed transceiver tosupport high-speed data mobility using Matlab and simulinkwith FPGA Device [3].5.1. Software Implementation of WLAN (892.1113):Software-Defined Radio refers to the use of software-programmable hardware to provide flexible radio solutions.Th e concept behind the technology is that it will providesoftware control of radio functionality. It facilitatesimplementation of some of the functional modules in a radiosystem such as modulation/demodulation, coding signalgeneration and link layer protocols in software. It can be usedto implement a wide range of radio applications like WLAN,Bluetooth and cellular wireless standards.5.2. Software Implementation of 802.11b on DSPProcessor:This case study provides the implementation of WLANstandard on Texas TMS320C6416 DSP based hardwareplatform [5]. The problem associated with 802.11 b standard isthat it requires very high computationial power. One way toachieve this efficiency is by implementing the physical layercompletely in the hardware. The 802.11lb medium AccessControl (MAC) layer software runs on the ARM Core. Thissoftware implementation approach provides ease of designmodifications at any stage of the product cycle also in thefield even after deploying the solution. It also facilitatesaddition of new features into the software architecture. Mostimportantly it gives great deal of flexibility to make customchanges at both physical and MAC layers for security relatedapplications in military, civilian and commercial areas.5.3 802.11b implementation Details:Figure 3 shows the design block diagram of implementation.Th e lP rich PHY algorithms and optimized implementationon TM S 320C6416 has made it possible to run the entireIEEE 802.1 lB PHY on a single DSP chip running at 600MHz. The 802.11lb MAC runs on the ARM core that ispresent inside the Excalibur. Communication between theMAC and PH-Y as well as the communication between the RFfront end and PHY is aided by the logic implemented on theExcalibur FPGA.

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References:I Robert Hirschfeld, Wolfgang Kellerer," An integratedconcept for fourth generation mobile computing", EurescomnProceeding 2002.2. Suk Yu, Kai Yeung," Challenge in the migration to 4Gmobile systems", IEEE Communications Magazine,

Alul December 2003.PCI 3. www~.niathxworks.corn

BRIDGE4.Jawad lbrahim,"4G Features", Bechtel TelecommunicationsRT technical Journal, December 2002.5. Suyog Deshpande, 'Software Implementation of 802.11LbINTERF~ACE Wireless WLAN Standard", Sr.MTS: HelloSoft, Inc, SanJose, CA, USA

Fig. 3: 802.1 lb ImplementationThe complete code is written with a mix of ANSI C andassembly coding. Real time modules are hand-coded inassembly and the non-real time modules are in 16-bit fixedpoint ANSI C.6. Conclusion:NGN provides revolution in the mobile networks butimplementation of this concept will have some questions tosolve. The speed at which this research is being carried outno doubt within this decade NGN is going to capture thewhole market of mobile.

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