Integration of UMTS with WLAN Using Intermediate IMS Network A. Bagubali, V. Prithiviraj, P.S. Mallick and Kishore V. Krishnan
Abstract Integration of different networks in real-time scenario can provide more benefits related to speed, bandwidth, and connectivity. UMTS and WLAN are two different types of networks with varying specifications. Integrating both the networks will be helpful in making use of all the features simultaneously WLAN networks provide higher data rate but cover smaller areas, while UMTS offers better connectivity with low-speed data rates and also covers larger areas at a time. It means integration of these services can provide higher speed wireless data services with ubiquitous connectivity. This paper focuses on implementing integrated UMTS–WLAN architecture using IP multimedia subsystem (IMS) as an intermediate network. IMS enables the user to switch from one network to another without interrupting a call. The main purpose of using IMS is to minimize the delay incurred during the hand off process and also the authentication, authorization, and accounting (AAA) process servers are inbuilt in its architecture. In this paper, integrating architecture has been implemented by two methods named as loose coupling and tight coupling. To compare the effect of using IMS, different scenarios with and without IMS have been simulated in OPNET Modeler 14. Comparison has been made on the basis of response time and download time for web browsing and FTP applications. Keywords UMTS
WLAN AAA IMS SGSN GGSN
A. Bagubali (&) K.V. Krishnan SENSE, VIT University, Vellore 632014, Tamil Nadu, India e-mail:
[email protected] V. Prithiviraj Rajalakshmi Institute of Technology, Chennai, India P.S. Mallick SELECT, VIT University, Vellore 632014, Tamil Nadu, India © Springer India 2016 L.P. Suresh and B.K. Panigrahi (eds.), Proceedings of the International Conference on Soft Computing Systems, Advances in Intelligent Systems and Computing 398, DOI 10.1007/978-81-322-2674-1_14
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1 Introduction The trend of using wireless network is increasing day by day as it is more compatible compared to wired networks in terms of mobility and setup cost. Wherever we go, wireless networks provide its services seamlessly with higher speed. But the major drawback is, WLAN does not cover larger areas at a time that means it can provide its services only up to a particular range. This is the reason why integration of networks is more popular among the users. The normal trend today is to use WLANs in hot spot to avail the high bandwidth and data rate, and when the WLAN network coverage is not available or network condition is not sufficient, then switch to UMTS network. In order to achieve this, a handover mechanism should be there which switch over the on-going call to a new network without interfering or dropping the call. But this is not happening now, as the first network before switching, log off the user and the user should sign into the new network as a new user. The WLAN uses access point for the transmission of data packets. The maximum coverage area of WLAN is 820 m and the maximum data rate is about 150 Mbps. The UMTS has been developed in third generation with the improved coverage area of 20 km but data rate is limited to 42 Mbps. In UMTS, the data packets are transferred to the users with the help of gateway GPRS support node (GGSN), serving GPRS support node (SGSN), radio network controller (RNC), and node B [1]. This general procedure will definitely interrupt a call while transferring a call to another network. To overcome this, IP multimedia subsystem (IMS) has been evolved as an advanced methodology, which provides better mechanism to switch from one network to another network. Session initiation protocol (SIP) is used by the IMS networks for session establishment, management, and transformation, due to which different multimedia services can be easily transferred within a single communication with the ability to add and drop services whenever required [2]. The rest of this paper has been designed as follows: next subsections describe about the architecture and different processes involved related to IMS. Section 2 discusses the related work that has been done in past. The model that has been used in this paper is described in Sect. 3. Simulation results have been presented in Sect. 4 and finally the conclusions are made in Sect. 5.
1.1
Integrating Architecture
The main issue involved in achieving the successful integrated network is to select the 3G and WLAN technology architecture. The quality of network integration points depends on the number of factors which includes mobility, handoff latency, security, cost performance, and accounting. The WLAN network can be connected to an UMTS network with various linking points namely SGSN and GGSN. When a WLAN mobile nodes (MNs) wants to exchange information to UMTS network user equipment, it organizes through GGSN Node. The UMTS network (UE) user
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Fig. 1 a Integrated UMTS–WLAN block diagram without IMS. b Integrated UMTS WLAN block diagram with IMS
equipment first initiates the packet data protocol (PDP). This introduce the operation of UE to its GGSN and also to the WLAN networks using the external data networks. The main entities of UMTS that play an important role in the integration are GGSN, SGSN, RNC, and node B. The security functions like handling encryption and authentication for the users are the responsibility of the SGSN. In addition, SGSN also have the responsibility of routing packets for the users. The routing function of SGSN is completed by the GGSN as it act as the gateway toward the external network [3]. In 3G network node B also called a base station that converts the radio interface of the signals into a data stream and forwards it to the RNC. In the reverse direction, it formulates incoming data from the RNC for transport over the radio interface. WLAN is integrated with UMTS using two different methods in this paper, i.e., loose coupling and tight coupling. Both the schemes are defined in later sections of this paper. The diagram given below shows the connection difference while implementing these two schemes. The hexagonal shape shown in Fig. 1 is called as cell which is the area covered by node B of UMTS network. One mobile node is moving in and out of the range of UMTS and switching to WLAN as it moves closer to the WLAN router.
1.2
Loose Coupling Scheme
In loose coupling scheme, the signals are transferred over WLAN to the UMTS network and the traffic flow takes place directly through internet (IP cloud). In this method, WLAN and UMTS are independently connected to each other [4]. In other words, both the networks are connected with each other using a third medium. It uses a common authentication mechanism which setups a link between AAA server of WLAN and home location register (HLR) of UMTS. This method is generally used when any private operator is operating WLAN, because the transmitted
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information does not pass through UMTS. The major drawback of using this scheme is poor handover from one network to another.
1.3
Tight Coupling Scheme
In tightly coupled scenario, WLAN network is directly connected to the core of UMTS. Therefore the traffic directly goes through UMTS network [5]. Opposite to the loose coupling method, all the systems in tight coupling are dependent on each other. In other words, this scheme does not use any third party medium for connectivity. The integrated networks are not independent. This dependency can be easily justified, because of the direct connection of one network to another. The handover mechanism in this scheme can be considered as cell to cell handover, as the node moves out from one network and directly enters to the range of other network. But the disadvantage of using tight coupling scheme is, due to the more traffic flow through WLAN, overflow situation may arise at the SGSN node of UMTS network [6].
1.4
Integrating Architecture with IMS
As mentioned in earlier sections, the main purpose behind using IMS is to reduce the hand over delay. And also the functioning of AAA server is already inbuilt in IMS, therefore the switching mechanism becomes much easier. The major entities of IMS architecture are proxy-CSCF, serving-CSCF, and interrogating-CSCF. These are the call session control functions (CSCF) having different role in registering and establishing the session between users. All the users need to register to the corresponding IMS terminal of their area. The registration process starts with sending a registration request to PCSCF, which then goes to ICSCF in order to search the location of particular user. Once the location is found, SCSCF carries out the authentication mechanism in order to complete the registration process. Now, if any user wants to make a contact with another user, it needs to send an invite request again through PCSCF. The location of called user will be verified by ICSCF, whether it is related to same network or different network [7]. After this verification SCSCF will be responsible for final establishment of session between calling and called user. This is the basic IMS registration and establishment process, using this IMS architecture, UMTS and WLAN can be integrated in a much easier way with proper hand off. When user moves from UMTS to WLAN, the IMS takes care of all the packet formats according to the switched network. IMS enables an user to continue its session in another network without any disturbance. Figure 1b shown below describes the integration while using IMS. The difference in architecture is only three additional proxy servers which are responsible for the successful session establishment.
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2 Literature Survey Our goal was to implement the two networks as WLAN and 3G cellular network as the integration which will provide us the seamless mobility and best quality of service with authentication, authorization, and accounting (AAA). Many of the previous work related to integration of networks have been surveyed. In [8], Surender et al. have made a comparison between WLAN and UMTS network based on the different performance parameters. In this paper, authors have presented different architectures for the dynamic home agent placement, so that mobile IP can be supported for heterogenous roaming. Results obtained by them shows that UMTS gives poor performance while WLAN provides average outcome. Abu-Amara et al. [9] implemented two different integration schemes, i.e. loose coupling and tight coupling. Along with these integration methods, they have considered mobile IP and mSCTP as the mobility schemes. Observations have been made for the applications HTTP, FTP, and other multimedia. According to the results, it has been concluded that loose coupling method gives the best performance in terms of throughput and delay parameters. In [10], they have surveyed recent advancement in the integration of UMTS and WLAN networks and presented the challenges and issues related to it to achieve seamless integration. They have concluded that IP technologies play a wider role in the integration of different networks. Also, different solution for QoS and the authentication of user has been examined. In [11], Karthika et al., have implemented the integrated networks of WIMAX–WLAN and UMTS–WLAN, and performance have been observed by transmitting voice packets over the integrated networks. The parameters that have been taken into consideration were Jitter, Delay, and MOS value. Conclusions have been made such that the MOS value got increased by the integration of WIMAX– WLAN. In [12] authors have proposed an architecture for the integration LTE-WIMAX–WLAN. They have used IMS as an intermediate platform, which enables the user to use any network at any time. They have compared the tight-coupled integration of LTE-WIMAX, LTE-WLAN with tight-coupled integration consisting of UMTS–WLAN and UMTS–WIMAX. Results have shown that successful handoffs can be made between different networks using the proposed architecture with maintained QoS levels. In [6], they have used IMS platform for the integration of UMTS–WLAN networks. They have proposed different measures to avoid the duplication of data transferred. It has been concluded that packet loss can be easily avoided during the handoff while using IMS for the network coupling. Liu and Zhou [13] have proposed an interworking architecture for the integration of UMTS and WLAN, based on the tight coupling methodology. To achieve the goal of reduced handoff delay, they have adopted a fast handoff algorithm. Based on the results obtained, it has been concluded that tight coupling can bring down the traffic cost and also it provides less burden to the UMTS core network. In [14], Routh proposed an efficient solution for service continuity of mobile users. They have implemented integrated UMTS–WLAN architecture using loose coupling
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method. Generic routing encapsulation has been used as a intermediate protocol between UMTS and WLAN. In [15] [16], authors have presented a survey on different integrating schemes of various networks. They have defined the vertical handover approach used in heterogeneity of networks.
3 Model Description 3.1
Scenario 1-Loose Coupling Without IMS
The above scenario for integration of UMTS–WLAN has been created in OPNET Modeler. It consists of UMTS network at one side of IP cloud and WLAN network on the other side of it. Since it is a loose coupling scenario shown in Fig. 2a in which the WLAN router is directly connected to IP cloud. Two application servers named as FTP server and HTTP server have been configured to observe the response time. The users in the range of UMTS network has been given mobility from UMTS range to WLAN range. Users can shift to any network wherever the range is more for the particular network. Since the application servers are kept common for both UMTS and WLAN, users can easily handover the call from one network to another. Mobile nodes have been selected from the object pallette in OPNET, so that their trajectory can be provided from one area to another.
3.2
Scenario 2-Tight Coupling Without IMS
In the tight coupling scenario shown in Fig. 2b, all the configurations and attributes have been kept same as loose coupling. The only difference is that the WLAN router is connected directly to the UMTS network instead of connecting through IP cloud. In this model, router is connected directly to GGSN node, but it is not necessary to connect it to GGSN, it can be connected to any one of the node of UMTS network.
3.3
Scenario 3-Loose Coupling with IMS
The Fig. 3a shows the implementation of loose coupling scenario using IMS. It consists of three additional proxy servers which are the main entities of IMS architecture. Every user need to register to the corresponding IMS terminal according to the registration process that has been mentioned in earlier section. Main benefit of using IMS is the negligible delay incurred during handoff from one network to another. Here user is moving from UMTS to WLAN network, where IMS is serving as an intermediate. It makes the switching mechanism much easier
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Fig. 2 a Loose coupling without IMS scenario in OPNET. b Tight coupling without IMS scenario in OPNET
as the AAA process is already inbuilt. Moreover, the response time for any application will be very less as compared to the integration without IMS.
3.4
Scenario 4-Tight Coupling with IMS
Similar to the loose coupling scenario, the Fig. 3b shows the tight coupling scenario with IMS as an intermediate. The functioning of both the networks is completely same, instead of the path used for traffic flow. Here, in tight coupling the traffic flows directly to the UMTS network instead of flowing through the internet. Rest all the process of registration and session establishment is same as the loose coupling scenario.
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Fig. 3 a Loose coupling with IMS scenario in OPNET. b Tight coupling with IMS scenario in OPNET
4 Results and Discussions 4.1
Without IMS
This subsection shows the results obtained when IMS is not used for the integration of UMTS and WLAN networks. The simulation results for integrated network without IMS consists of analysis for the following parameters: (i) FTP download response time: Figure 4 shows the download response time for FTP application in loose coupling and tight coupling scenario. As indicated in the scenario, the users are moving from UMTS to WLAN range via the trajectory path that has been given. Since WLAN provides higher data rate than UMTS, therefore as the user moves to WLAN the response time gets
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Fig. 4 FTP download response time. a Loose coupling. b Tight coupling
Fig. 5 HTTP page response time. a Loose coupling. b Tight coupling
decreased. Initially the response time is more as observed from the graph, but as the time increases, the response time gets decreased due to the mobility of nodes. By comparing both the scenarios, it can also be observed that loose coupling method takes less download response time as compared to tight coupling method. It indicates that loose coupling method is better for FTP application. (ii) HTTP page response time: Figure 5 shows the page response time for HTTP application in loose coupling and tight coupling scenario. It indicates the time taken to load a page during the web browsing. Again it is observed that initially the page response time is more, as the time increases it gets decreased due to the shifting of nodes from UMTS to WLAN. But by comparison of both the scenario, it can be seen that tight coupling method takes less page
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response as compared to loose coupling. It indicates that tight coupling method is better for HTTP application.
4.2
With IMS
This subsection shows the results obtained when IMS is used as an intermediate network for the integration of UMTS and WLAN networks. All the registration and session establishment process take place through the proxy server nodes of IMS architecture. The simulation results consists of analysis for the following parameter. (i) FTP download response time: Figure 6 shows the download response time for FTP application, when IMS is used as an intermediate network for the integration of UMTS–WLAN. As compared to the previous results without IMS, this response time is very less in both loose coupling as well as tight coupling scenario. But as the time increases, the response time still gets decreased, this is again due to the mobility given to the nodes. (ii) HTTP page response time: Figure 7 shows the page response time for HTTP application, when IMS is used as an intermediate network. After comparing this result with the results obtained without IMS, it can be easily observed that using IMS has come out as an efficient method when users move from one network to another.
Fig. 6 FTP download response time. a Loose coupling. b Tight coupling
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Fig. 7 HTTP page response time. a Loose coupling. b Tight coupling
5 Conclusions To achieve the goal of this project, the IMS network has been used in the integration of UMTS and WLAN networks. Results have been taken for two different applications, i.e., FTP and HTTP. The integration scenario has been implemented using two methods which are loose coupling and tight coupling. WLAN has been integrated with UMTS using GGSN node in the UMTS core network. By observing all the graphs obtained after simulating in OPNET modeler, it can be concluded that the response time for any application continuously decreases as the user nodes move from network with low data rate to the network providing higher data rate. In this project, nodes are given mobility from UMTS to WLAN. Another thing that can be concluded is while using IMS in the integration of two networks, the response time is very less as compared to the integration without IMS. It shows the easiness and benefits of using IMS architecture. Therefore, IMS is the best platform to be used in wireless generation, which makes the user the integration has come out as a solution to overcome the situation when any network is having low data rate, lower bandwidth, or less connectivity. The integrated network enables the user to use the features of both the networks according to the requirements. This is the best way to eliminate any drawbacks of the network, because the same drawback can be overcome by other network which has been integrated. In future, this project can be extended to integrate more than two networks which may include other advanced networks like WIMAX, LTE etc. Integrating more advanced networks with the existing one may provide feasibility to the users in terms of speed, connectivity, and bandwidth availability. The same IMS platform can be used for the integration, as it is able to handle interworking of different networks in a much easier way.
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