Zone-Based Service Architecture for Wireless Ad Hoc Networks

GESTS Int’l Trans. Computer Science and Engr., Vol.18, No.1 73

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Zone-Based Service Architecture for Wireless Ad Hoc Networks

Yeonkwon Jeong1, Insu Jeong1, Joongsoo Ma1, and Daeyoung Kim2

1School of Engineering, Information and Communications University, Daejeon, 305-714, KOREA

{ykwjeong, bijis, jsma}@icu.ac.kr 2 Dept. of InfoCom Engineering, Chungnam National University,

Daejeon, 305-764, KOREA [email protected]

Abstract. Rapid growth of the industry of mobile devices and mobile networks like IEEE802.11 and ad hoc networks will change the concept of the mobile service. Service providers may want to give their services whenever they want and wherever they are. If they do not want to provide their services any more, they may get out of the service networks at their likes. In addition, location-based service in wireless networks is indispensable. This must be served in both the indoor and outdoor environments. To meet these critical requirements in wireless networks, this paper proposes a new architecture of mobile wireless service networks, named ZBS(Zone-Based Service) Network, by way of using ad hoc protocols and location sensing systems in the hierarchical network structure. We also explain elementary techniques for ZBS architecture and show our implementation results.

1 Introduction

For the last few years, the use of mobile devices with IEEE802.11 WLAN [16] interface like PDAs, notebooks and so on has increased. We can see many people who use the mobile devices with IEEE802.11 in the campus, lounge of the airport, and even street. Since throughput of the IEEE802.11 WLAN is higher than that of the cellular network, we can enjoy various applications with a mobile device having the IEEE802.11 WLAN. The IEEE802.11 specification defines two modes. One is infrastructure mode and the other is ad hoc mode. In the infrastructure mode, network providers or administrators make a pre-planning for a network and install APs (Access Points) in the fixed locations. All hosts have to communicate each other via the APs in the infrastructure mode. Therefore, mobile hosts cannot move wander from place to place and are restricted within a coverage area where there must be at least one AP. On the contrary, in the ad hoc mode, a network is formed in cooperation with hosts and hosts can take services without additionally required equipments.

[19] [20] are applications for military. The ad hoc networks in the applications are used for surveillance and communications among soldiers, vehicles or combat aircrafts in the battlefields. The wireless ad hoc sensor networks are popular in both military and dangerous regions to provide crisis management services like area monitoring which is long lifetime static ad hoc network and communication between

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rescues which is the temporary and small area ad hoc network. [21] is public purpose and temporary constructed application for special meetings. The network is small and particular although the application is public. Existing ad hoc network applications are restricted to only special situations like military and disaster regions or are limited to a small area such as a conference room and an airport lounge. In addition, existing ad hoc networks cannot hold wide and public attributes in common.

Rapid spread of IEEE802.11 WLAN will result in occurrence of new services. And the diffusion of ad hoc networks will change the previous concepts of mobile services which may call for the installment of wide and public networks. Breaking from the convention in which service providers build all elementary components of a network and have the charge of operation and administration for the network, service providers just support minimal equipments. The formation of networks and offer of services are freely operated and maintained in cooperation with service users, not service providers.

For example, consider a man doing overseas travel. The man gets lost and does not know where he is. He is very hungry now. He wants to find a fast-food restaurant in the current area, know where it is and go there by help of his mobile device. In other case, a person enters a campus. He may want to know what departments are in the campus and where it is by way of his mobile device. And when he goes into a certain department building, he may want to know what professors are in the building and where the office of one of the professors is with the mobile device. He may move into another service area and want to get another service in new area. For example, he may want to know how many theaters are in the area, what movies are now on show at each theater, and where they are. And then he may want to buy a ticket for some film in advance. With a mobile device, he can enjoy the services provided in the area. Not to mention it, he can access Internet with his mobile device.

Let’s think about the view of service providers. We are lords of fast-food restaurants. We want to advertise our restaurants to the public. One of us liquidates his restaurant and wants to open a bakery in another area. He surely will inform his bakery on the service network of the new area. Likewise a professor wants to use the service network for giving his history and course work for his students to some people. A service provider installs an infrastructure which has the minimum functionality to manage services. And a fast food store open and registers itself to the infrastructure to advertise itself. Many stores inform themselves to the infrastructure. That is all processes to set up a service network.

In this paper, we propose zone-based service architecture for ad hoc network to implement new services. We also explain elementary techniques and show our implementation results. Section 2 considers architecture for our services. Section 3 presents the important components for the service architecture. Section 4 describes the implementation issues and a test bed to verify the design. Finally, there are conclusions in the section 5.


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2 Zone-Based Service Network Architecture

ZBS is to provide services which are only served in a zone with mobile users staying in the zone. A zone means a service area covered by a service provider such as a fast-food restaurant, a bakery or a professor. Therefore, a zone may have one or more services simultaneously, and the right to choose wanted one of those services is given to a mobile user in his location. To do this, ZBS tracks the location of mobile users and the available services in each zone. It also has the capabilities to integrate existing services such as Internet service. ZBS network is configured with the minimum infrastructures, voluntary will of service providers and interaction with or among users. ZBS maintains a profile for each user device to identify each user as well as service providers’ profiles, defining services and locations of them in each zone.

Figure 1 shows a large application domain partitioned into multiple small zones such as public areas, public or private enterprise areas, and campus. Although each small zone may be indoor or outdoor, our technology can give same ability to users in any environments.

Ad HocNetwork

GPS Satellite

Internet

Zone Service Portal

Local Zone Database Infra-Zone

Service Station

Zone Service Station

End Users

Satellite link

Infrastructure Network

Ad HocNetwork

GPS Satellite

Internet

Zone Service Portal

Local Zone Database Infra-Zone

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Zone Service Station

End Users

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Figure 1 Zone-based service network Figure 2 Zone-based physical architecture

To support ZBS, we use the physical architecture consisting of ZSP(Zone Service

Portal), IZSS(Infra-Zone Service Station), ZSS(Zone Service Station), and end user in Figure 2. ZBS network has the minimum infrastructures for performing ZBS and voluntary service providers which serve their services. The ZSP and IZSS are the infrastructures which may be constructed by ZBS network agents. ZSP maintains LZD(Local Zone Database) for keeping the profiles for identifying each end user and service provider. IZSS makes the ZBS network robust and helps service providers and end users to locate them. Infrastructure nodes are robust, fault tolerant and static systems. Their power is supplied by wall power. Generally the deployment of the infrastructure devices which are high complex systems has to be pre-planned.

On the other hand, the ZSS is an object for serving its services, that is, the service provider. End users interact with the ZBS system through ZBS client devices which are typically wireless multimedia handheld units. The ZSS of users is mobile, battery power supply, and low computing device.

The maintenance of above architecture is very easy, the energy performance of the end users is excellent, and the system is very stable due to the hierarchical structure.


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In addition, the dynamic and distributed attributes among levels of the structure make ZBS system low complex and high stable although upper levels are changeable. We will present each type of nodes in the next section.

3 Functional Components for ZBS

In this section, we explain the important techniques for ZBS system. Almost protocols depend on the applications. The protocols change over the applications, and are modified according to their applications.

3.1 Network Self-configuration The wireless topology of the ZBS network changes unexpectedly due to mobility of end users, infrequent movement of ZSS, and reconfiguration of IZSS and ZSP.

ZBS network is self-configured and self-healed with interacting between infrastructures and infra-less-structures. Of course, the infrastructures such as ZSP and IZSS are pre-designed and pre-located.

3.1.1 Address Auto-configuration There are several address auto-configuration protocols in wireless network whose topology is changed randomly [1].

A candidate protocol must cope with following requirements: Plug and Play: All nodes configure their interface dynamically without manual

typing. Resource limitation: We assume that ZBS is IPv4 network. Because of the

scarcity of the address resource, the addresses have to be reused. Mobility: Due to mobility of the nodes, the duplicate addresses must be detected

and resolved. Moreover, the address leakage must be recovered. Network partitioning and mergers: A node may bridge two zones. An end user

M communicates with a ZSS in the zone A. If the end user moves to another zone slightly, there must be chance for the end user to get into both two zones simultaneously. Unfortunately if the address of a ZSS in a zone is same with the ZSS in another zone, the end user communicates with one of the two ZSSs which may be wrong destination of packets from the end user. So, our candidate protocol has to detect and resolve bridging zones. And zone partitioning must be detected and resolved.

3.1.2 Multi-Hop Routing Each node has to forward packets to a neighbor as an intermediate node like the router. To do so, each node runs on the ad hoc routing protocol such as AODV [5] or DSR [6]. These protocols can also cope with random changes of network topology dynamically.

Unfortunately, as Figure 3, DCDP has a serious problem. Although end user A knows that end user B is its neighbor by hello message of ad hoc routing protocols, end user A sends its packets through a ZSS and a IZSS because end user A and end user B are not in the same subnet. If destination is in the different subnet, the packets


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of source always pass through ZSP, ZSS or IZSS. This can result in longer path than physical path. So, all nodes need to have relay function which can relay packets to a node in the different subnet.

Figure 3 Long path problem in ZBS network Figure 4 Purpose of infrastructures

ZBS has the functionality of the positioning of end users and serving location

information of ZSS to the end users. It may be necessary for the ad-hoc routing protocols to support the functionality of the positioning.

3.2 Localization Wireless node positioning is a fundamental and crucial issue in many mobile applications. Recent mobile computing applications need to know the physical location of things so that they can record them and report them to us. ZBS also needs localization of all nodes. Even if a service we want to get is in the zone where we are, we want to know where the server which serves the service is.

If all nodes have GPS [7] receivers, they localize themselves and use the location information easily. But, GPS-free positioning is also desirable, when GPS signal is too weak like in indoor environment, when it is jammed, or when a GPS receiver has to be avoided for cost or integration reasons.

If all infrastructures and ZSS in the zone do not GPS receivers, the ZBS can support local location service by way of SPA [8] which is a distributed algorithm that enables the nodes to find their positions within the zone using only their local information. And there are some location systems for ad hoc networks [9].

If at least infrastructures such as ZSP and IZSS have GPS receivers, ZBS can support global location service to end users.

We use [10] for the positioning of a mobile node, and RSS (Received Signal Strength) for the range estimation.

3.3 Service Managements In this sub-section, we show how to manage services in our self-configured zone which enables the nodes to find their positions. ZBS includes the location service.

The entity of giving services is the ZSS in ZBS system. Although infrastructures such ZSP and IZSS can give services, the purpose of them is to configure a zone as server and helpers for the zone which enable a ZSS to join the zone or the zone to support global location service like Figure 4.


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IZSS A enables ZSS B to join the zone and to support global location service by receiving GPS signal.

3.3.1 Service Registration Initial ZSP sends periodic service advertisement messages. When IZSS or ZSS joins the zone, the node sends the service registration message. If the node receives service advertisement messages or service response message from ZSP, the node registers its services to ZSP with its service descriptions, location and addressing information (domain name and address). Simultaneously, the node stores its ZSP’s location and addressing information. The ZSP maintains a mapping table for relation between the services including location and address of each IZSS or ZSS.

If all ZSSs and IZSSs register their services to ZSP in a zone, the ZSP keeps the mapping table for all ZSSs and IZSSs’ services, and all ZSSs and IZSSs have the information of the ZSP. After configuring a zone and registering all services in the zone, the ZBS system is created.

3.3.2 Service Discovery and Delivery When an end user joins the ZBS zone, the end user sends service request messages to neighbors. If the end user receives service response message from a neighbor which is the address of ZSP or the service advertisement message from the ZSP, the end user can access to the ZSP with the address. Then, the end user can search a necessary service in the mapping table in the ZSP choose one service and access to the ZSS serving the service by way of location and address related to the service. At last, the end user enjoys the service from the ZSS and can know the location of the ZSS. At this moment, the ZSS has to know the location of it. If the ZSS does not have a GPS receiver, the ZSS finds its location through [10].

3.3.3 Service Deregistration If a ZSS wants to leave from a zone, the ZSS sends the deregistration messages to the ZSP. Then ZSP removes the services of the leaving ZSS in the mapping table. Of course, ZSP removes the services from the information in network layer in Ⅲ-A. The gradual or abrupt departure of the ZSS from the zone is the same meaning with service deregistration. But the service deregistration does not mean the departure of the ZSS from the zone. This may result from service changes or temporal relaxation in the ZSS.

3.4 Accessing to Internet The IP (Internet Protocol) [11] is constantly acquiring a dominant position in networking. All-IP based networks are being designed from the standardized bodies. The desire for mobile access to information available on the Internet is stronger than ever. This is the reason ZBS is based on IP.

Connectivity to Internet is provided at the edge of the network infrastructure by ZSP in ZBS system. The ZSP can offer global addressability and bidirectional Internet connectivity to every node in the ZBS network.

All nodes in the ZBS are based on the private IPv4. Because ZSP has NAT function, all nodes in the ZBS can access to Internet and Internet hosts can


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communicate with a node in the ZBS. If ZBS is IPv6 [12]-based network, the ZSP just functions as default router in Figure 5.

Figure 5 Access to Internet Figure 6 IPv6 address structure in ZBS

And the ZUID of Section 3.1 is unnecessary in the IPv6 ZBS. The part of subnet,

which comes from the interface address of the ZSP, in IPv6 address structure plays ZUID roles in Figure 6. 3.5 Migration to Other Zones Mobile end users can migrate between zones. When end users leave from a zone and enter another zone without keeping any connections to the previous zone, the mechanism for migration of the end users is unnecessary because the end users assign their addresses from the ZSP in the new zone. In addition, when end users migrate to another zone, the end users can be isolated as Figure 7 over the address leasing time.

Figure 7 Isolated end user

At this time, the management for the migration is also unnecessary. We only consider the migration of end users with keeping connections to nodes or IP hosts in the previous zone. If an end user migrates to another zone with connection in the previous zone, two nodes are involved in an address conflict. The migrating node easily detects the migration to another zone with the service advertisement message, which has different ZUID from one of the node, from the ZSP in the new zone. At least one of them has to change its address to resolve the conflict. On an address change all active connections of one node may break. Our strategy is that new joining node of conflict nodes gives up its address and the connection does not break.

Mobile IP [13] can be employed to make such movement seamless whenever physically possible. The migrating node assigns a new address from the new zone.


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The node that changes its address notifies the corresponding node about the new address using a Binding Update message. The node uses its old address as home address. The corresponding node can then use an IP tunnel to send packets to the new address. These packets can then be de-capsulated and arrive at the upper layer with the old IP destination address. At this time, the node does not create a new communication session with the old address. If the communication session with the old address finishes, the old address is removed in the node.

4 Implementation

We have built ZBS prototype systems and tested them. We implemented the systems on only laptops running Red Hat Linux 8.0. However, the current implementation runs on not only laptops but also HP iPAQ model H5050 Pocket PCs. Each HP iPAQs and laptops include IEEE 802.11b WLAN-based CISCO AIRONET 350 series NICs that attach to the devices. We have experimented with a set of a ZSP, two ZSSs and an end user as one zone in the outdoor. Figure 8 shows our experiment topology.

Figure 8 Experiment topology

Figure 9 is the software architecture of our initial ZBS system. We introduce [10] for address auto-configuration of all nodes to our system. The address allocation module gives plug-and-play, dynamic address reuse, solutions of address conflicts and address leakage, and network partitioning and merging. We apply AODV-UU-0.7.2 [17] routing protocol which is modified for the mirror elimination algorithm [10] to our routing layer for multi-hop and dynamic link state. We constructed the system on the user space to minimize to modify the kernel space. We used HTTP [18] for the service registry and service delivery which are web-based. Only ZSP has a database for storing the profile about services which are served in the zone and only ZSS has service applications which are web-based in our ZSS system.


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HTTP

M-AODV-UU-0.7.2Routing Table

TCP

IP Auto-configuration

Database

Service Registry

NIC

UDP

SOCKET

Web-based GUI

Service DeliveryService Discovery

Web-based Services

Neighbor Table

Ranging Table Management

Positioning

User space

Kernel space

HTTP

M-AODV-UU-0.7.2Routing Table

TCP

IP Auto-configuration

Database

Service Registry

NIC

UDP

SOCKET

Web-based GUI

Service DeliveryService Discovery

Web-based Services

Neighbor Table

Ranging Table Management

Positioning

User space

Kernel space

Figure 9: Software modules of ZBS system

In this implementation, we saw that the ZBS system has successfully been

operated. Figure 10 shows the end user’s mobile device. You can see the user interface of ZBS system and NIC on the top of the PDA. Figure 11 is the ZSS which is based on web application. The screen on the laptop is the web-based user interface for service registration.

Figure 10: End user interface Figure 11: ZSS interface

We utilized the range estimation technique of RSS and the positioning methods, tri-

lateration and mirror elimination algorithm.[10] We obtained the important parameters such as path loss exponent, effective communication range, and reference power loss for the ranging and positioning. Figure 12 shows the locations of an end user with varying position of the end user. End user can know the locations of all ZSSs with accessing to ZSP which has the table for the information of all ZSSs in the service network. If the end user knows its current location, it can get the distance between itself and a ZSS.


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Figure 12 Positioning of end user

We can know statistics of our location system from Figure 13. The positioning rate is over 90% at all the test points except for the point (40, 20) which is out of the communication range, about 40m. The average location error mean is about 25m and the average standard deviation is around 15m. This value is reasonable because it is in the short walk from the location of the end user.

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Figure 13 Positioning rate and location error

5 Conclusions Rapid growth of the industry of mobile devices and mobile networks like IEEE802.11 and ad hoc networks will change the concept of the mobile service. The service network can be formed by not service providers who are suppliers of infrastructures but service users who are suppliers of services and mobile users. And so far, almost all researches about the ad hoc networks have been separately performed without


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considering the relation among various techniques. And there are few researches about useful applications for ad hoc networks.

In this paper, we propose ZBS architecture for ad hoc networks. We also describe the implementation issues such as adaptations and modifications about existing elementary techniques to be used in our service architecture. And we implement ZBS architecture on the Linux platform, test its functional requirements, and show experimental results. We believe that the ZBS architecture with ad hoc networks will be very good framework for mobile users and future applications. In the future, we will study followed research topics to enhance and provide more functionalities for our ZBS architecture like location accuracy enhancement, security and authentication.

References

[1] Kilian Weniger and Martina Zitterbart, “Address Autoconfiguration in Mobile Ad Hoc

Networks: Current Approaches and Future Directions,” University of Karlsruhe, Germany, IEEE Network Magazine, July 2004

[2] R. Droms, “Dynamic Host Configuration Protocol,” RFC 2131, March 1997 [3] Archan Misra, Subir Das, Anthony McAuley, and Sajal K. Das, “Autoconfiguration,

Registration, and Mobility Management for Pervasive Computing,” IEEE Personal Communications, vol. 8, issue 4, pp. 24-31, August 2001

[4] A. J. McAuley and K. Manousakis, “Self-configuring Networks,” MILCOM 2000, Oct 2000

[5] C. Perkins, E. Belding-Royer, and S. Das, “Ad hoc On-demand Distance Vector (AODV) Routing,” RFC 3561, July 2003

[6] David B. Johnson, David B. Maltz, and Yih-Chun hu, “The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks,” draft-ietf-manet-dsr-10.txt, July 2004

[7] B. Hofman-Wellenhof, H. Lichtenegger, and J. Collins, “Global Positioning System,” Theory and Practice, Fourth Edition, Springer-Verlag, 1997

[8] Srdjan Capkun, Maher Hamdi, and Jean-Pierre Hubaux, “GPS-free positioning in mobile ad hoc networks,” Hawaii International Conference on Systems Sciences, 2001

[9] Jeffrey Hightower and Gaetano Borriello, “Location Systems for Ubiquitous Computing,” IEEE Computer, August 2001

[10] Insu Jeong, Namshik Kim, Yeonkwon Jeong, and Joongsoo Ma, “A Positioning Probability Enhancement Algorithm using Ad Hoc Routing Protocol,” Proc. of CIC 2004, Oct. 2004

[11] Jon Postel, “Internet Protocol,” RFC 791, September 1981 [12] S. Deering and R. Hinden, “Internet Protocol, Version 6 (IPv6) Specification,” RFC 2460,

December 1998 [13] C. Perkins, “IP Mobility Support,” RFC 2002, October 1996 [14] Yonggil Jeong, “Performance Evaluation of Indoor Location Finding System with US

Reflections Removal Algorithm,” A Thesis for the Degree for Master, Information and Communications University, Korea, Jul 2004

[15] Na Young Kim, “An Improved Indoor Location Finding System,” A Thesis for the Degree of Master, Information and Communications University, Korea, Jan 2004

[16] Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, ANSI/IEEE Std 802.11 1999 Edition

[17] Uppsala University, http://user.it.uu.se/~henriki/adov/ [18] Andrew S. Tanenbaum, “HTTP – The HyperText Transfer Protocol,” Computer Networks,

Fourth Edition, Prentice Hall PTR, pp. 651-656 [19] Kenneth C. Young, et al, “Ad Hoc Mobility Protocol Suite for The MOSAIC ATD,”


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MILCOM 2003, Oct 2003 [20] Wayne W. Brown, et al, “Future Combat System – Scalable Mobile Network

Demonstration Performance and Validation Results,” MILCOM 2003, Oct 2003 [21] Laura Marie Feeney, et al, “Spontnet: Experiences in Configuring and Securing Small Ad

Hoc Networks,” 5th IEEE International Workshop on Networked Appliances, Oct 2002 Biography

Yeonkwon Jeong received the B.S and M.S degrees in computer engineering from Chungnam National University, Daejeon, Korea, in 1990 and 1992, respectively. He is currently a Ph.D. candidate from the same university and working for the MMRC(Mobile Multimedia Research Center) of Information and Communications University as a research staff member. His current research interests include mobile ad hoc networks and high performance network protocols.

Insu Jeong received the B.S degree in computer engineering from Kwangwoon University, Seoul, Korea, in 2003. He received the M.S. degree in School of Engineering from Information and Communications University in 2005. He is working for Samsung Electronics as a research engineer. His current research interests include mobile ad hoc networks and IP auto-configuration.

Joongsoo Ma received the M.S. and Ph.D. degrees in Electrical and Computer Engineering from University of Massachusetts, Amherst in 1977 and 1978, respectively. From 1978 to 1991 he was a research staff member at the IBM T. J. Watson research center, working on protocol analysis and design. From 1991 to 1998 he was a managing director at the SK Telecom research center, Seoul, Korea, working on mobile network design and management. Since 1999 he is a professor at Information and Communications University, Daejeon, Korea. His research interests include information theory, mobile ad hoc network and wireless personal area network.

Daeyoung Kim received the B.S. degree in Electronics Engineering from Seoul National University, Seoul, Korea, in 1975. He received the M.S. and Ph.D. degrees in Electrical and Electronics Engineering from KAIST, in 1977 and 1983, respectively. Since joining Chungnam National University, Daejeon, Korea, in 1983, he is currently a professor. His current research interests include high speed network, wireless network, and next generation Internet protocols. He is a senior member of IEEE, ACM, and Internet Society.

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Zone-Based Service Architecture for Wireless Ad Hoc Networks