WiMesh: Wireless Mesh/Sensor Network Testbed for

Research and Education

Abstract

This proposal proposes to build WiMesh, a wireless heterogeneous mesh/sensor network testbed consisting of over 70 IEEE 802.11-based wireless mesh nodes and 50 sensor nodes with varying capabilities in terms of processing, energy efficiency and radio transmission capacities. The IEEE 802.11-based wireless mesh nodes and sensor nodes will be placed in area between undergraduate dormitory and CHIPs building at KAIST (Korea Advanced Institute of Science and Technology) and inside CHIPs building respectively. These activities include developing protocols and systems for secure and resilient key management, intrusion detection, energy-efficient routing and MAC protocols, data aggregation, topology control, localization and target tracking. The proposed testbed provides realistic large-scale wireless mesh network and sensor network environments for evaluating and validating the ideas, protocols and systems conceived from these activities. The data and experience gained from operating and managing a real network environment will also provide practical insights for students and researchers on the operation of large-scale heterogeneous mesh/sensor networks that help identify new security and performance problems and develop their practical solutions.

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1.1 Overview of WiMesh

We propose to build WiMesh (Wireless Mesh/Sensor Network Testbed), a wireless heterogeneous sensor network testbed, in Department of Electrical Engineering Computer Science at Korea Advanced Institute of Science and Technology (KAIST). WiMesh will consist of over 70 wireless LAN nodes and 50 sensor nodes with varying capabilities in terms of processing, energy efficiency and radio transmission capacities. These wireless nodes will be placed area between undergraduate dormitory and CHIPs building located at northern part of KAIST. The sensor nodes will be placed in faculty offices and various research laboratory spaces in 3rd and 4th flooors a CHIPs building.

We propose to include both high-end and low-end mesh/sensor nodes in WiMesh. We plan to use Stargate as the high-end wireless IEEE 802.11 nodes. Stargate is a powerful single board computer with enhanced communications and processing capabilities. The Stargate uses Intel's latest generation 400MHz X-Scale® processor (PXA255), and runs Linux as the operating system. In addition to traditional single board computer applications, the Stargate directly supports applications designed around Intel's Open-Source Robotics initiative as well as TinyOS-based Wireless Sensor Networks. A stargate node comes with an IEEE 802.11 wireless interface card. We also propose to use MICAz Motes as the low-end sensor nodes in WiMesh. The MICAz is a 2.4GHz, IEEE 802.15.4 compliant Mote module used for enabling low-power, wireless, sensor networks. We plan to run TinyOS, an open source operating system for networked sensor nodes, on MICAz. An advantage with MicaZ is that we can modify the MAC functions as all the MAC functions are implemented in software (unlike IEEE 802.11 Wireless LAN card).

We propose to set up WiMesh with the availability of both an 802.11 and 802.15.4 wireless mesh network. While 802.11 is widely used for high-speed wireless network access nowadays, 802.15.4 is an

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IEEE standard targeted at networks of low-power, low data rate devices such as sensors, remote controls, and interactive toys. We plan to attach to each high-end Stargate node two 802.11 wireless card, so that these high-end nodes can form a high-speed ad-hoc MESH network and can perform as an access point from unanimous users accommodating in dormitories and research buildings located in area. Similarly, the low-end MICAz nodes can form a low-speed ad-hoc network through the on-board 802.15.4-compliant communication modules. We also propose to attach MICAz node to Stargate node. MICAz node gathers information from sensor mesh network and Stargate sends it to sink node through wireless mesh network. Moreover, we propose to deploy more low-end MICAz nodes to match real-world deployment of sensor networks. We propose to install each such node on an Ethernet programming board, which allows remote programming of these nodes. As a result, these nodes form a flexible, remotely configurable, heterogeneous wireless network.

We propose to set up sensor mesh nodes on the third floor and forth floor in the CHIPs building and wireless mesh nodes around undergraduate dormitory and CHIPs building. High-end wireless nodes will be installed on streetlamp because of electrical power supply and its coverage. Low-end sensor nodes will be installed in faculty offices and laboratory spaces. The distribution of the sensor nodes offers a three-dimensional network with sufficient space coverage, and thus offers a realistic environment for testing sensor network techniques.

1.2 Requested Equipments and Budget Information

WiMesh will have 70 Stargate nodes as the high-end nodes and 20 ASUS Terminator T1-C3 boards as the stable control channel support. As Stargate is placed on the streetlamp which has only electrical power supply not an Ethernet connection, the stable control connection is strongly recommended. ASUS Terminator T1-C3 board acts as a wireless bridge for the control connection within line of sight from each Stargate node. Each Stargate node is also attached with two Compact Flash (CF) wireless cards so that these nodes can form a high-speed wireless ad-hoc network and act as an access point. There will be another 50 low-end MPR 2400 MICAz nodes, each of which is attached to an MIB600CA Ethernet programming board to facilitate remote configuration.

1 Stargate Advanced Kits, it includes one Stargate node (i.e., the processor board and the daughter card), one video sensor (Logitech QuickCam Pro 4000), one CF wireless card (Ambicom Wave2Net 802.11b CF card), and the software running on the node. This unit is used for the development kit for the software development.

70 Stargate processor boards.

20 ASUS Terminator A-1 C-3 main boards.

50 MIB600CA Ethernet programming boards.

50 MPR2400 MICAz nodes.

45 MTS300 basic sensor boards and 5 MTS420 advanced sensor boards.

We plan to purchase these equipments from Crossbow Technology, Inc. These equipments and the pricing information are listed on Crossbow’s website at http://www.xbow.com.

Table 1 summarizes the equipments and the price information.

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Table 1 WiMesh Equipments and Cost

Item Description Unit Price($) Quantity Total PriceSP-KIT420 Stargate Advanced Developer's Kit 895 1 895

SPB400 Stargate Processor Board 425 70 29,750 ASUS T1 Main board for Control Connection 300 20 6,000 MPR2400 IEEE802.15.4/ZigBee Compliant MICAz 125 50 6,250 MIB600CA Ethernet Gateway for MICAz mote 299 50 14,950 MTS300 Light, Temp.,Acoustic, Acoustic actuator 120 45 5,400 MTS420 Light, Temp., Barometer, GPS, Seismic 375 5 1,875

Total 　 　 　 65,120

Total amount shown in Table 1 already includes nodes for off-network experiment, instruction and backup purposes. There will be additional cost for the extra equipment regarding the outdoor installation, even further request $3,000 (estimated) for the shipping of these equipments, and installation cost.

70 Packages for Stargate processor boards that work outdoor environment

140 CF Wireless LAN cards. Each Stargate has two LAN cards, one of them is for the Ad-hoc mode and another one acts as access point.

70 Power Package that has a Li-ion battery pack and a charger.

Table 2 summarizes the installation cost and extra equipments cost

Table 2 WiMesh Installation, Extra Equipments and Cost

Item Description Unit Price Quantity Total PricePackage Stargate Case 100 70 7,000 LAN card CF Wireless LAN Card (802.11b/g) 70 140 9,800

Power Package Battery and Charger 100 70 7,000 Installation Stargate Installation 50 90 4,500 Shipping Shipping 3,000 1 3,000

Total 　 　 　 31,300

The estimated total cost WiMesh is $96,420 without considering of special offer due to in large quantities. Thus the total cost of WiMesh establishment is $99,450 including special discount $2,620 from Crossbow and VAT ($5,650) occurred from purchase of crossbow products.

1.3 Necessity of BK21Funding

The requested BK21funding is critical in acquiring the proposed testbed at KAIST. The funding for BK21funding has been invested primarily research activities in the field of science and technology, plus in the field of humanities and social science. This project mainly targeted to testbed establishment for the education and research purpose. Thus, the BK21 fundiing is cruial in acquiring large-scale wireless mesh/sensor network testbed for research and education and supporting KAIST wireless research activities to get brilliant results.

If funded, the requested BK21 fund will create a synergy with the other research activities ongoing projects on wireless mesh/sensor networks at KAIST, including

Speed/Channel/Media Adaptive Multi-hop FDD/TDD MIMO Cellular System (Funded by Samsung)

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Development of interoperable wearable ubiquitous computer terminal device technology (Funded by IITA)

The proposed testbed will greatly impact the current projects on wireless sensor networks by providing a realistic network environment to validate the assumptions, evaluate the proposed techniques, and inspire researchers about new techniques and tools. The supports provided by the ongoing projects will provide manpower to manage and support the WiMesh testbed.

2 Research Interest in Areas

2.1 Network Protocols for Wireless Mesh Networks

MAC Protocols for WMNs: Wireless mesh networks usually adopt MAC protocols for wireless ad-hoc networks. However, its relatively stationary characteristic gives another opportunity to optimize inefficient MAC protocols in ad-hoc networks. Hence developing an optimized MAC protocol for wireless mesh networks is challenging and essential.

Topology-aware Routing Protocols for WMNs: In wireless mesh networks, most of routings happen on stationary wireless mesh routers. If the stationary characteristic is exploited, it is possible to develop a routing protocol which has far less overheads compared to routing protocols for wireless ad-hoc networks. In example, geographic routing would incur few overhead and might perform very well on wireless mesh network.

Compatible Transport Protocols for WMNs: Even in wireless ad-hoc networks, there are only few transport protocols which performs well in wireless environments. It is very challenging to develop a transport protocol compatible with TCP and which outperforms TCP in wireless environments.

2.2 Security of Wireless Sensor Networks

Secure and Resilient Localization: The objective of this research is to develop a comprehensive suite of techniques to prevent, detect, or survive malicious attacks against location discovery in wireless sensor networks.

Secure and Resilient Clock Synchronization: An accurate and synchronized clock time is crucial in many sensor network applications, particularly due to the collaborative nature of sensor networks. However, all of the clock synchronization protocols proposed for sensor networks are vulnerable to malicious attacks, while traditional fault tolerant clock synchronization protocols are not practical in sensor networks due to the resource constraints as well as their assumptions that are not realistic in sensor networks.

Broadcast Authentication: Broadcast authentication is a fundamental security service to enable authentication of broadcast queries, commands, and data. However, existing broadcast authentication techniques either have scalability problem, or require substantial bandwidth or resources at the broadcast nodes.

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Intrusion Detection in Wireless Sensor Networks: Intrusion detection is complementary to prevention-based techniques in protecting information systems. Intrusion detection in wireless sensor networks is particularly important due to the fact that unattended sensor nodes may be easily captured and compromised.

2.3 Network Protocols for Wireless Sensor Networks

MAC and routing cross-layer optimization: When a node is not on a routing path, it does not require maintaining a regular radio duty cycle and can safely turn off its radio as it does not have to forward any packets. This is possible because typical sensor networks create routing paths on demand as tracking events occur. By coordinating MAC operations and routing control information exchanges, a node can allow MAC to learn about whether it is currently on a routing path or not, thus causing MAC to adjust its sleep and wake schedules accordingly. The net result is an energy-efficient MAC and routing protocol that exploits the tradeoffs among delays, energy and network throughput.

Scalable, robust, energy-efficient MAC protocols: CSMA and TDMA are highly complementary to each other. CSMA lacks scalability with respect to contention as its throughput and energy efficiency dramatically drop under high contention. However, CSMA is highly robust to network failures, timing failures, topology changes and time-varying channel conditions. TDMA is completely opposite: it handles contention at low cost achieving high throughput and energy efficiency under high contention. But under low contention, it does not allow full utilization of the channel capacity. Moreover, its susceptibility to network failures and changes and reliance on clock synchronization make it impractical to use in large-scale wireless sensor networks. Developing a hybrid protocol that can combine the strengths of CSMA and TDMA is required while offsetting their weaknesses.

Adaptive and robust network transport: Previous work finds that the channel conditions are highly dependent on the network load: under high load, the channel conditions deteriorate sharply. Under this environment, a layered network approach where different layers make independent decisions for adaptation according to the varying conditions can lead to substantial network under-performance. For instance, bad channel conditions due to high network load can make the routing layers falsely assume that the current next-hops are bad connections and cause to change the next-hops. However, since the bad conditions are caused by high contention, changing the routing paths does not improve the situations but only deteriorates the network performance as this might cause the routing layer to choose inferior routing paths to the current one – it could lead to a vicious cycle where the worsen routing paths cause another routing flap. Changing routing paths can also severely affect the transport performance since some protocols like TCP rely on the end-to-end characteristics of the network paths. We believe that network adaptation such as congestion control, routing adjustment and contention resolution must coordinate together to avoid any undesirable interactions and feedback effects. This research requires extensive network experiments to measure and understand the network phenomena involving the interaction between network load and congestion and to evaluate developed techniques

2.4 System-Wide Resource Managements of Mesh

Resource management algorithm to provide fairness: The wireless backbone provides a backhaul communication service that is transparently routed to and from the wired Internet access point and end users. It is an essential requirement

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for the backhaul network system to ensure that all users in the network achieve a fair share of overall system resources. But current working protocols do not provide a fair resource sharing, scarce performance to users located far from the available Internet egress points. Hence a coordinated multi-hop resource management algorithm must be developed to achieve high performance while preserving a system-wide notion of fairness

The above research activities are highly experiment-oriented requiring extensive network testing and evaluation. Since much work revolves around improving network scalability, testing under a large-scale testbed such as WiMesh is essential

3 Logistics

Installation: The sensor nodes in WiMesh will be installed in over faculty offices and laboratories in the CHIPs building located northern KAIST, where the network communication group of Department of Electrical Engineering Computer Science of KAIST is relocated. Figure 1 and Figure 2 show the floor plan of the inside building of sensor nodes. The WiMesh testbed will be using the third floor and forth floor. There are 4 faculty offices, two laboratories divided by cubical space, lounge, and bedrooms.

Figure 1 Floor Plan of the 3rd Floor in CHIPs Building

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Figure 2 Floor Plan of the 4th Floor in CHIPs Building

We will place one or more sensor nodes in each office space. Each node will be connected to the department Ethernet and the power line. Figure 3 shows an installation of a MICAz node with an Ethernet programming board. We propose to connect all the sensors to the department local area network through the Ethernet interface. The wired network will be used for the management and remote reprogramming of the sensor network. Since the new computer science building will support a high-speed (Gigabit) Ethernet throughout the building, we can easily access the testbed. The radio mounted on each node will be used to form a wireless network of sensors and will be used for actual experiments.

Figure 3 An Example Installation of Sensor Node with an Ethernet Programming Board

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Green zone

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High-end wireless nodes will be installed in over wide area between undergraduate dormitory and CHIPs building. High-end wireless nodes are built up with 3tier mesh topology and cover wide area square kilometer using 50 wireless routers and 20 wireless access points. The wireless access points give the connection to the wired backhaul network and the wireless routers form a wireless backbone, which provides multihop connectivity between nomadic users and wire gateways. Most of wireless routers will be installed on streetlamp because of electrical power supply and its coverage. Figure 1 shows the floor plan of the wireless routers on streetlamps and wireless access points inside building. This area includes 8 dormitory building, cafeteria, library and 6 engineering builds.

Figure 4 Floor Plan of the wireless nodes in a wide area northern KAIST

The installation of WiMesh requires a substantial amount of manpower since it involves manual installations of over 50 sensor nodes and 70 wireless nodes. The campus authorities will also provide technical support for securing the IP addresses and coordinating with the campus network administration to sort out any signal interference issues with Stargate, MICAz and department wireless LAN, especially KT IPv6 Wireless Network. The technical staff of this project will be responsible for the day-to-day operation of the testbed including software and hardware upgrade and maintenance, and interface to the campus network technical support group.

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