Wireless Technology Was An Important Breakthrough Computer Science
There is no doubt that wireless technology was an important breakthrough in communications world. Wireless third generation network is coming with many benefits and features for network users. 3G network main advantages are it provides more connectivity and reachability. In the other side, IEEE 802.11 Wireless LAN has it own advantages which are Broadband service with low cost and widespread technology. Therefore, to get the best of both two words, the idea of integrating 3G wireless network with wireless local area network came into picture.
There are six integration solutions which differentiated by the level of integration. This paper focused on studying loose and open coupling solutions. Also, there are different mobility schemes which are used to provide seamless handover from both networks. This paper focused on studying mSCTP and Mobile IP as handover protocols. It was concluded that Mobile IP over loose is the optimum solution to integrate UMTS and WLAN. Loose coupling provide higher integration level then open coupling and it reduces operation cost to maintain two authentication systems.
Moreover, since mSCTP has higher impact on application during the handover and its handover delay is higher then Mobile IP, it is recommended to use Mobile IP as mobility schemes especially that if we consider the high mobility for airport users which will result on having more handover in mSCTP case. Also, optimized Mobile IP is recommended to be used which will reduce the application response time by eliminating the need for tunneling.
The focus of this paper is to analysis the behavior for two coupling scenarios "Loose Vs Open" Coupling. Also, studying the effects of adding mobility schemes "mSCTP and Mobile IP" over both integration scenarios. The other purpose of this paper is to evaluate different integration solutions and mobility schemes that provide best service and performance by using OPNET as simulation tool.CHAPTER2UMTS AND WLAN THEORY2.1 UMTS NETWORK
Universal mobile telecommunication system(UMTS) Which is also called as 3G was lunched at the end of 2001 which use a host of high tech infrastructure networks, handset , base stations ,switches and other equipment to allow mobiles to offer high speed internet access , data and video and CD quality services.3G is the term coined by the global cellular community to indicate the next generation of mobile service capabilities such as higher capacity and enhanced functionalities which allow advanced services and application including multimedia applications .UMTS is the broadband transmission of text, voice, video, and multimedia at data rates up to and possibly higher than 2 Mbps.2.2 UMTS Architecture
A UMTS network consist of three interacting domains;
1. Core Network (CN),
2. UMTS Terrestrial Radio Access Network (UTRAN) and
3. User Equipment (UE).
The main function of the core network is to provide switching, routing and transit for user traffic. Core network also contains the databases and network management functions.Figure 2.1: UMTS Architecture
The basic Core Network architecture for UMTS is based on GSM network with GPRS. All equipment has to be modified for UMTS operation and services. The UTRAN provides the air interface access method for User Equipment. Base Station is referred as Node-B and control equipment for Node-B's is called Radio Network Controller (RNC). UMTS system page has an example, how UMTS network could be build.2.3 Wireless LAN Network(WLAN)
Some years ago very few peoples were familiar to the technology wireless LAN (WLAN) but now days after very short period of time almost everyone is familiar to this technology. WLAN cause an unexpected growth in the mobile communication and internet because it's lot of benefits like easy deployment, low cost and flexibility. However, there are some issues while using WLAN for future data communication. The IEEE 802.11 standard for WLAN has emphasis on the physical layer and medium access control (MAC) layer for ad-hoc and access point (AP) based networks. Initially WLAN standards supported only three protocols for physical layer Infrared (IR), direct sequence spread spectrum, frequency hopping spread spectrum.
The IEEE 802.11b is the extension of original one having data rate 1, 2, 5.5 and 11 mbps and it uses direct sequence spectrum (DSSS) at the physical layer. Extension IEEE 802.11a and IEEE 802.11g provides data rate that has the range from 6 to 54 mbps in 5 GHz and 2.4 GHz band respectively, it uses orthogonal frequency division multiplexing (OFDM) at the physical layer. All the standards of WLAN has same protocols used at MAC layer which uses carrier sense multiple access/ collision avoidance (CSMA/CA) scheme at the MAC layer.
The WLAN networks support two modes of operation, namely
1. Ad-hoc mode
2. Infrastructure mode.
Of these modes, infrastructure mode architecture is of most interest to Wireless Internet Service Providers (WISPs).2.4 Operating modes of WLAN:Ad-hoc Mode
The ad-hoc mode (figure 2.2) is Also referred as the peer to peer mode or independent basic service set(IBSS).This ad-hoc mode enables mobile stations to interconnect with each other directly without the use of access point(AP).All stations are usually independent and equivalent in the ad-hoc network .station may broadcast and flood packets in the wireless coverage area without accessing internet.
The ad-hoc configuration can be deployed easily and promptly when the users involved cannot access or do not need a network infrastructure. For instants, participants of a conference can configure their laptops as a wireless ad-hoc network and exchange data without much effort.Figure 2.2: Ad-hoc ModeInfrastructure Mode
In the Infrastructure mode (figure 2.3) there are AP's which bridge the mobile stations and the wired network. BSS's can be connected by a distributed system its normally is LAN. The coverage area of BSS's usually overlap. Handover occurs when a station moves from a coverage area of one to another AP.
To access the 802.11 WLAN, the mobile node first authenticates to the access point and then associates with it to obtain an association identifier. The basic authentication and encryption mechanisms in the 802.11 standard have been shown to be inadequate in meeting the design goals of confidentiality integrity and access control.Figure 2.3: Infrastructure ModeCHAPTER 3UMTS and WLAN Interworking3.1 Motivation
The main motivation for mobile operators to get involved in the WLAN business is the following:
â€¢ Public WLANs provide the opportunity to mobile operators to increase their revenues significantly from mobile data traffic
â€¢ WLANs can be considered as an environment for testing new applications at initial stage
â€¢ High-demand data traffic from hotspot areas can be diverted from 3G to WLAN relieving potential network congestion.
â€¢ Location-based services in hotspot areas could be based on WLAN technology rather than using more-complex GPS-like systems
On the other hand, a shift from WLAN to 3G could take place due to the following reasons:
â€¢ Poor coverage: users may be able to use WLAN services at the airport of departure, but not at the airport of arrival, or at the hotel
â€¢ Lack of brand recognition: the service operators are often new start-ups, which causes end-users to hesitate to use the service.
â€¢ Lack of roaming agreements: end-users are forced to locate different service providers at the places they roam to.
The service provider value proposition for utilizing integrated WLANs with cellular networks includes the following benefits for carrier as well as their subscribers:
1. Extension of current service offering by:
â€¢ Integrating cellular data and WLAN solutions.
â€¢ Positioning for voice phone service in hotspots.
â€¢ Engaging enterprises with in-building solutions.
2. Improve bottom line with new revenue and lower churn:
â€¢ The carrier provides improved in-building coverage by using intranet bandwidth instead of in-building cell sites to provide coverage.
â€¢ Cross system/service integration features become a competitive advantage for the carriers offering Seamless Mobility services.
â€¢ The cellular provider derives service revenue for authentication services, mobility services, and calls that do not use cellular bearer channels.
â€¢ The cellular handset becomes an indispensable element.
â€¢ The handset can operate with more functionality e.g. even as gateway.
â€¢ The subscriber increases his dependency on the handset.
3. Payload traffic trade-off:
â€¢ Some calls will hand over from cellular channels to WLAN connections when subscribers enter these coverage areas.
â€¢ Other calls will hand over to cellular bearer channels when people leave WLAN coverage areas.
â€¢ A more integrated approach to data traffic will probably increase the use of data transferred over cellular.
â€¢ As subscribers become more dependent on their much more useful handsets, they will hocall more and be called more, everywhere.3.2 Interworking Model and Requirements
We assumed a WLAN/3G interworking with each 3G public land mobile network (3G PLMN) based on UMTS technology and each WLAN is based on IEEE 802.11 technology. Through coupling, the main goal is to combine the wide area coverage of UMTS, with its associated roaming and mobility properties and, on the other hand, to gain additional throughput and capacity by using WLAN in hotspots. Also, different mobility schemas has been considered and compared in this reportCoupling Scenarios
Within the context of this paper, four scenarios have been considered regarding the 3G and WLAN interworking:1. Open Coupling:
In the open coupling interworking scenario, no specific WLAN access is required and a separate authentication procedure is used from the 3G and the WLAN network. Such a scenario is shown in the next Figure (3.1).2. Loose Coupling:
In this scenario (Figure 3.2), no specific WLAN access network is required. There is a common customer database and authentication procedure. This means that the 3G-HLR database is also used by WLAN for both access and authentication. This means that a gateway is placed between the HLR and the ISP AAA server, performing translation from MAP to RADIUS/DIAMETER and vice versa3. Tight Coupling:
The key characteristics of this scenario (Figure 4) include seamless handover between 3G and WLANs, as well as, WLAN access similar to UTRAN (3GPP radio protocols). This necessitates the definition of an interface interconnection the WLAN in SGSN node..4. Very Tight Coupling:
This interworking approach is similar to the previous case. However in this case, WLAN is considered as part of UTRAN and a new interface has been defined interconnecting the WLAN in the RNC of the UTRAN.Figure 3.1: Open Coupling ModelFigure 3.2: Loose Coupling ModelFigure 3.3: Tight Coupling ModelFigure 3.4: Very Tight Coupling Model
When integrating WLAN and GPRS networks the question is if it is suitable to use a standard AAA server that works for both systems, or if separate servers should be used. An AAA server for a GPRS network differs from a WLAN AAA. A combined server that is capable of handling different types of users would be a possible way of integration, so what is demanded of a shared AAA?
IP address assignment and mobility management
Level of Service
Hence the key element in the architecture is the 3G AAA Server .3.3 Mobility SchemesMobile Stream Control Transmission Protocol (mSCTP)
Transport layer mobility is proposed as an alternative to network layer mobility for seamless mobility management. Mobility management in the transport layer is solely accomplished by use of Stream Control Transmission Protocol (SCTP) and its currently proposed Dynamic Address Reconfiguration (DAR) extension. SCTP with its DAR extension is called Mobile SCTP (mSCTP).mSCTP is a transport layer protocol similar to Transmission Control Protocol (TCP) that operates on top of the unreliable connection-less packet network. It provides unicast end-to-end communication between two or more applications running in separate hosts and offers connection-oriented, reliable transportation of independently sequenced message streams.
The biggest difference between mSCTP and TCP is multi-homing i.e. the idea of having several streams within a connection (multi-streaming) and the transportation of sequence of messages instead of sequence of bytes. mSCTP is capable of handling several multiple IP addresses at both endpoints while keeping the end-to-end connection intact. These addresses are considered as logically different paths between the endpoints. During initiation of the connection lists of addresses are exchanged between the endpoints. Both endpoints must be able to receive messages from any of the IP addresses related to the endpoints. One address is chosen as the primary address and is used as the destination for normal transmission. The other addresses are used for retransmissions only. The SCTP DAR extension enables the endpoints to add, delete and change the primary address dynamically in an active connection without affecting the established connection.Mobile IP (MIP)
Mobile IP is most useful in environments where mobility is desired and the traditional land line dial-in model or DHCP do not provide adequate solutions for the needs of the users. If it is necessary or desirable for a user to maintain a single address while they transition between networks and network media, Mobile IP can provide them with this ability. Generally, Mobile IP is most useful in environments where a wireless technology is being utilized. This includes cellular environments as well as wireless LAN situations that may require roaming. Mobile IP can go hand in hand with many different cellular technologies like CDMA, TDMA, GSM, AMPS, NAMPS, as well as other proprietary solutions, to provide a mobile system which will scale for many users.
Each mobile node is always identified by its home address, no matter what its current point of attachment to the Internet, allowing for transparent mobility with respect to the network and all other devices. The only devices which need to be aware of the movement of this node are the mobile device and a router serving the user's topologically correct subnet.Methodology Overview & Challenges
The simulation model is designed in OPNETâ„¢ Modeler 14.5. The simulation parameters were selected to accurately model an interworked WLAN-UMTS system supporting a "hot spot." To compare the Loose and Open coupling, simulations were done in both architectures with the same simulation factors (number of nodes, traffic).
The primary design goal for this project was to interwork WLAN with UMTS so that it can be utilized as an alternate radio access network for hotspots such as Airports. The remaining design goals were intended to focus the design in order to create an open simulation framework with the capabilities to study the issues and trades-offs for interworking WLAN with UMTS. Our project focuses on evaluating the performance of these integration schemes through open and loose coupling and selects the best of this for using it while incorporating mobility schemas.
1. Focus the design on the 3GPP proposed Scenario 2 for supporting 3G authentication and access control.
2. Utilize IP cloud as the common service interface for applications in order to guarantee independence of applications from the underlying radio access network.
3. Minimize the number of changes to the existing UMTS protocols.
4. Minimize the number of changes to the existing WLAN protocols.Network Design
The primary design goal for this project was to interwork WLAN with UMTS so that it can be utilized as an alternate radio access network for hotspots such as Airports. The remaining design goals were intended to focus the design in order to create an open simulation framework with the capabilities to study the issues and trades-offs for interworking WLAN with UMTS
The simulation model is designed in OPNETâ„¢ Modeler 14.5. The simulation parameters were selected to accurately model an interworked WLAN-UMTS system supporting a "hot spot." The first phase of this project was studying two integration scenarios Loose and Open Coupling in terms of affecting the performance for the application. In the second phase, it was focused on comparing mSCTP and Mobile IP over different integration options using Loose and Open coupling, simulations were done in both architectures with the same simulation factors (number of nodes, traffic).The design is considering 7000 users with an average of 1 Mbps for every user. Also, different traffic assumptions have been considered during the simulation.Traffic Calculation
Traffic calculations are based on the following assumptions
1. Considering 7000 users with 1 Mbps for each user.
2. Implementing background traffic in all backbone links.
3. The number of foreground users is decreasing as the number in the backbone decrease to show the difference between open and loose coupling with different number of users.
4. Assuming there are other networks that link to the same backbone. Therefore, we have mapped every number of simulation users to link user where it can handle 1000 users at a time with 1 Mbps for each. This will result on filling 1G link in the backbone. Figure 6, shows the traffic distribution on every link for Traffic distribution 1 (FTP:20,HTTP:40,MM:40) with 7000 users. Table 2, shows the packet size details for control traffic.
5. The foreground user is varies under different load (i.e. from 7000 to 1000) to show the difference between loose and open coupling with different number of users.Assumptions
We have made the following assumptions to keep the simulation complexity manageable, while still meeting the research goals. This section describes assumptions made in modeling both the UMTS and WLAN data networks, as well as the interworking of these two technologies.
Traffic assumption as stated above.
For Mobility purpose, the users will start moving from the home network (i.e. UMTS) to foreign network (i.e. WLAN) after five minute from starting the simulation.
All UMTS users will move to WLAN network.
Multimedia traffic is simulated as Video Conferencing.
The foreground user is varies under different load (i.e. from 7000 to 1000) to show the difference between loose and open coupling with different number of users.
The authentication process has been simulated using custom application:
UMTS authentication was implemented using customer application and it is communicating with VLR and HLR during this process.
WLAN is using user id & password authentication.
The main system components of the UMTS packet domain architecture, are modeled as the following OPNETâ„¢ nodes: the user equipment (UE), the Node-B, the Radio Network Controller (RNC) and the core network (CN).CHAPTER 4INTEGRATION SOLUTIONS
In this phase both scenarios for open and loose coupling has been compared in term of network performance. Both open and Loose coupling are sharing the same billing system which is under STC supervision. However, in open coupling, every system has its own authentication system where in loose coupling both networks sharing same authentication system.4.1 Open CouplingFigure 4.1: Open coupling authentication
As shown in figure, the authentication process in open coupling for both UMTS and WLAN is totally independent. Also, as stated previously, the authentication process in UMTS is by AKA. The authentication transactions for UMTS are shown in figure11, where the VLR is act as the middle node in AKA authentication (VLR/SGSN).4.2 Loose Coupling
As shown in figure loose coupling, there is extra authentication traffic which goes between WLAN and UMTS. For UMTS authenticating, it is the same as open coupling which is shown in figure. However, for WLAN authentication, we can see extra transactions which have been added to perform the communication between AAA server and HLR.Figure 4.2: Loose Coupling authentication
Loose couplingFigure 4.3: WLAN users AuthenticationFigure 4.4: UMTS users AuthenticationsMobility Schemas Design
The effects of mobility schemas on network performance are considered by using different integration methodology which are open and loose coupling. As stated, this project will focus on two mobility schemas and they are mSCTP and Mobile IP.mSCTP Design over open coupling/ loose couplingFigure 4.5: mSCTP traffic (MM as an example)Figure 4.6: mSCTP handover tasksFigure 4.7: Handover TrafficMobile IP Design over open coupling/ loose couplingFigure 4.8: Mobile IP handoverCHAPTER 5SIMULATION MODELFigure 5.1: Simulation Model
As shown in figure, the simulation model consists of four main parts:
1. WLAN Network:
Access Point (WLAN Router)
AAA Server for authentication
2. UMTS Network
Node B Access Point
HLR for authentication
VLR for authentication
3. Internet Provider (in this project STC) consist of
MMS (Multimedia Server)
Switch5.1 Simulation Parameter tools
1. Task Node to define custom applications
2. WLAN authentication which is the different between loose and open coupling where in loose coupling, WLAN authentication will communicate with HLR (five phase's task). However in open coupling its is normal user ID and password between WLAN user and AAA (three phases task).
3. UMTS authentication which occurs between UE and HLR and it consist of eleven phases.
4. Application Node to define exist applications
Billing application as DB traffic
Custom Task 1: WLAN authentication.
Custom Task 2: UMTS authentication.
Profile Node to group the applications and assigned them to specific node or user
UMTS user applications
UMTS user mobile applications
WLAN user mobile applications
Mobile IP (Mobile IP scenario)
mSCTP (Initial/handover/delete) for mSCTP
The model entities have been configured accordingly to generated stated traffic.CHAPTER 6OPNET MODELEROverview
Third Millennium Technologies OPNET (Optimised Network Engineering Tool) is a network technology development environment that allows you to design and study communication networks, devices, protocols and applications. In simple terms it allows you to simulate elements of a computer network in order to investigate how they will react to different circumstances without the need to physically construct them.
Analysis and simulation, both are studying methodology for networking. There are many network scenarios which is difficult to model them in analyzing methodology. The solution for those cases is to use simulation tools. Any programmer can build his own simulation using one of the programming languages. However, there are many simulation tools which have built-in models and provide different statistics and results close to real network. OPNET and NS2 are examples of simulation tools.
Optimum Network Performance (OPNET) simulation tool is very powerful simulation tool since it has standard model libraries which consist of many network standards and they are used in "Plug and Play" fashion . This has its benefits of removing coding overhead from the analyst and let him focus more in network analysis. Also, many network scenarios can be simulated by modifying elements parameters. The model libraries are grouped by devices, links, LANs & Clouds and Utility objects. Also, many standard and vendor specific protocols are available and the devices can be easily configured to work for specific protocol . In addition, OPNET's user can build his own model using available model tools and OPNET has the ability to validate generated model. Randomness is key factor in
OPNET simulation since many parameters are configured by probability functions. Therefore, single simulation scenario isn't enough to give accurate projection for real network behavior. As a result, there may be some discrepancy between the analytical study and simulation results and it should be within acceptable range as long as the difference is justifiable. Finally, OPNET is very powerful in terms of collecting simulation statistics where the user can select as many statistics he needs and the results can be calculated in any form (i.e. average, PDF, CDF and â€¦etc).OPNET Vs NS-2
Ns-2 provides very similar results compared to OPNET Modeler, but the "freeware" version of Ns-2 makes it more attractive to a researcher. However, the complete set of OPNET Modeler modules provides more features than Ns-2, and it therefore will be more attractive to network operators. One specific observation can be made about these network simulators as a result of some experiments. For a simple CBR data traffic, it appears that the simulators had no significant problem in terms of accurately modeling the test bed behavior. However, in the case of an FTP session, the simulators using default simulation settings did not adequately model the dynamic behavior of FTP when is used in its basic standard form.FTP(through TCP flow control) adapts its output to prevailing network conditions, whereas the response of Ns-2 and OPNET Modeler did not always mimic this performance. However, when "fine tuning" of parameters was performed, it is found that Modeler was a more accurate simulator for this particular case.It Uses Flat earth surface model which is biggest disadvantage of Ns-2.CHAPTER 7SIMULATION AND RESULTS7.1 WLAN Simulation:Figure 7.1: WLAN Simulation modelResult:Figure 7.2: Load and Throughput for WLAN7.2 UMTS SimulationFigure 7.3: UMTS Simulation ModelResult:Figure 7.4: Load and throughput for UMTS7.3 UMTS-WLAN SimulationFigure 7.5: Integrated WLAN-UMTS ScenarioResults:Throughput: Open Coupling Vs Loose CouplingFigure 7.6: ThroughputDelay: Open Coupling Vs Loose CouplingFigure 7.7: DelayPerformance:Figure 7.8: FTP trafficFigure 7.9: FTP response timeUMTS-WLAN Integration: Real-time ModelFigure 7.10: UMTS-WLAN Integration: Real-time ModelCHAPTER 8CONCLUSION
While generic integration solutions for 3G/WLAN networks are abundant in the literature, very few, if any, studies present performance evaluation for Internet applications for such heterogeneous networks. This paper attempts to bridge the gap and present a summary of performance figures obtained for four integration solutions. Using simulations the paper evaluates the performance of integrating a WLAN into a UMTS network in a hot-spot location such as an airport. The paper considers two integration schemes, open coupling and loose coupling, and two mobility management schemes, Mobile IP and mSCTP. Furthermore, the paper took into account varying both the traffic load and the application mix when conducting the simulations. The performance metrics considered in the paper include WLAN delay, WLAN throughput, each application response time, each application throughput, and the handover delay. The results show that the loose coupling integration scheme together with Mobile IP provides the best performance.
To sum up, after analyzing all collected results, it is recommended to use loose coupling since it will provide better integration then open coupling and reduce the cost of maintain two authentication systems when using open coupling. Moreover, the option of using mobility schemes is dependent of the mobility behavior, so if the people has high mobility , this will result on having more handover which means more impact on application and network during handover when using mSCTP. However, if the mobility is low, then mSCTP will provide better response time for the user equipment than Mobile IP because mobile IP need to route the traffic to home network every time. Therefore, Mobile IP over loose coupling is the optimum solution to integrate UMTS and WLAN.
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