Minkeun Ha

SNAIL: an IP-based wireless sensor network approach to the internet of things

Recent technological progress has been materializing the Internet of Things (IoT), which is breathing new computational and communicational capability into anything in everyday life. An important step toward the IoT would be to facilitate suitable wireless sensor network technologies based on a verified standard protocol, the Internet Protocol, to support the network of things. An increase in research efforts has led to maturity in this field, yet there seem to be gaps to be filled because of the focus on how to adapt the IP to the space of things. This article introduces the Sensor Networks for an All-IP World (SNAIL) approach to the IoT. The proposed architecture includes a complete IP adaptation method. It also includes four significant network protocols: mobility, web enablement, time synchronization, and security. The feasibility and interoperability of the proposed approach is confirmed by the implementation of SNAIL platforms and tests on a testbed built in the Korea Advanced Research Network.

SSL-Based Lightweight Security of IP-Based Wireless Sensor Networks

IP-based wireless sensor networks (IP-WSN) are popularly recognized as a global sensor networks infrastructure by combining IPv6 technology with wireless sensor networks (WSN). However, IP-WSN, currently, does not provide security because it is commonly recognized that it is a big burden for IP-WSN to adapt Internets dominant security protocol. We suggest a security protocol for IP-WSN based on Secure Sockets Layer (SSL). We have developed IP-WSN sensor node hardware with 16-bit MSP430 MCU including 116 KB Flash and 8 KB RAM, and implemented IP-WSN software stack and lightweight SSL components. The resource consumption is around 64 KB of Flash and 7 KB of RAM when it is used that ECC for key-exchange and authentication, RC4 for data encryption, and MD5 for hashing. And it takes total 2 s for a full SSL handshake and a 127 bytes packet transfer. It can make IP-WSN secure and be used for the public and private services such as military observation, healthcare, and home-network.

Inter-MARIO: A Fast and Seamless Mobility Protocol to Support Inter-Pan Handover in 6LoWPAN

Mobility management is one of the most important research issues in 6LoWPAN, which is a standardizing IP-based Wireless Sensor Networks(IP-WSN) protocol. Since the IP-WSN application domain is expanded to real-time applications such as healthcare and surveillance systems, a fast and seamless handover becomes an important criterion for mobility support in 6LoWPAN. Unfortunately, since existing mobility protocols for 6LoWPAN have not solved how to reduce handover delay, we propose a new fast and seamless mobility protocol to support inter-PAN handover in 6LoWPAN, named inter-MARIO. In our protocol, a partner node, which serves as an access point for a mobile node, preconfigures the future handover of the mobile node by sending mobile nodes information to candidate neighbor PANs and providing neighbor PAN information like channel information to the mobile node. Also, the preconfigured information enables the foreign agent to send a surrogate binding update message to a home agent instead of the mobile node. By the preconfiguration and surrogate binding update, inter-MARIO decreases channel scan delay and binding message exchange delay, which are elements of handover delay. Additionally, we define a compression method for binding messages, which achieves more compression than existing methods, by reducing redundant fields. We compare signaling cost and binding message exchange delay with existing mobility protocols analytically and we evaluate handover delay by simulation. Analysis and simulation results indicate that our approach has promising fast, seamless, and lightweight properties.

SNAIL gateway: Dual-mode wireless access points for WiFi and IP-based wireless sensor networks in the internet of things

One of the important challenges in the Internet of Things (IoT) is how to acquire the physical context of things. IP-based wireless sensor networks (IP-WSNs) could be a promising approach to collecting the physical context of things and to integrating WSNs to the Internet. However, realizing IP-WSNs in IoT exposes two major challenges. One is how to embed the Internet Protocol (IP) in resource-constrained sensor nodes. The other is how to achieve real-world deployment of WSNs and its integration with the Internet on the fly and on the cheap. In this paper, we present the SNAIL (Sensor Networks for All-IP World) project and introduce a new type of IP-WSN gateway, which supports dual wireless access points for WiFi and IP-WSN, enabling deployment of SNAIL nodes in an easy and rapid manner as for the solution. To show the proof-of-concept, we implement a new SNAIL platform from tiny sensor nodes to a gateway.

Dynamic and Distributed Load Balancing Scheme in Multi-gateway Based 6LoWPAN

In 6LoWPAN, all the nodes access the Internet through the gateways, which are on the border to legacy IP networks and handle ingress and egress data traffic. A gateway as the traffic center may easily become the congestion-concentrated point so that causes reliability problems and performance degradation. Gateway bottleneck is the dominant reason for network capacity and throughput constriction, since all traffic should pass through the GW. Even though we apply multiple gateways, the network capacity and network throughput cannot increase linearly with the number of gateways because of the imbalance of traffic load among gateways. The load balancing between gateways is a key technology to reduce the traffic congestion thereby enlarging the network capacity, satisfying the capacity fairness among nodes, and removing network reliability issue. In this paper, we propose a dynamic and distributed load balancing scheme to achieve a global load fairness, motivated by water flow behavior, named MLEq (Multi-gateway Load Balancing Scheme for Equilibrium). We implement our load balancing scheme in ns-2 simulator and it is verified by extensive simulations. As a result, we show that throughput can be improved by the proposed scheme and the load can be fairly distributed over LoWPAN. More importantly, the results show that network capacity and throughput can increase linearly with the number of gateways.

The stateless point to point routing protocol based on shortcut tree routing algorithm for IP-WSN

IP-based Wireless Sensor Network (IP-WSN) is one of the essential elements enabling Internet of Things (IoT). However, IP-WSN imposes great challenges due to low processing resources and strict energy constraints of sensors. Various routing protocols for IP-WSN have been proposed considering low-cost communication with resource-constraint and typical traffic patterns like multipoint-to-point, but most of routing protocols causes problems incurring inefficient route or/and consuming many processing resources. Especially, as far as point-to-point (P2P) traffic is concerned, those routing protocols incur triangular detour routes and require many processing resources at intermediate nodes where P2P traffic is an important traffic pattern. To address these challenges, we propose the Stateless P2P Routing protocol (SPR) based on shortcut tree routing algorithm which is our previous study. SPR can deliver a packet to the node having the smallest remaining hop count among neighbors without additional control overhead, instead of always delivering a packet to a parent or children along tree routes. SPR also provides a nearly stateless routing in that SPR determines a route through hierarchical address structure and one hop neighbor information without having to store global routing state. We implement SPR in our IP-WSN platform named SNAIL and conduct a simulation and a measurement to verify the performance of SPR. The simulation results show SPR provides improved hop count compared to HiLow and RPL. It also provides reduced memory usage and the number of control packets compared to RPL. Additionally, the measurement results show SPR provides decreased round trip time and increased packet delivery ratio compared to HiLow and RPL.

The patient-centric mobile healthcare system enhancing sensor connectivity and data interoperability

The revolutionary improvements in low power devices and lightweight network protocols are making the mobile healthcare engage attentions. However there are some obstacles to realize mobile healthcare. Connectivity of miniaturized wearable sensors of the body area network (BAN) to the Internet is one of the most important issues in realizing mobile healthcare system. Interoperability is also important in order for sensor data not to be isolated in a local system. In this paper, we designed our mobile healthcare system resolving connectivity and interoperability issues. In our mobile healthcare system, body sensors are integrated by leveraging RESTful web service via CoAP over IPv6, enabling web-based access from browsers. Extended EPCglobal architecture was used for our system to enable sharing of sensor data among applications with different domain through the standardized protocol. We developed two applications, patient browser and EagleEye, to prove its feasibility.

TAMR: Traffic-aware multipath routing for fault tolerance in 6LoWPAN

Tree based hierarchical routing is widely used in 6LoWPAN due to advantages of low control overhead and low memory resources. However, it generates a triangular detour path considering point-to-point (P2P) traffic. Reactive routing provides a reasonable P2P path by conducting flooding-based route discovery, but the flooding increases packet interference due to huge control overhead. Multipath routing can improve the reliability by preparing for the alternative path. Nevertheless, it needs an extra table for storing the alternative path and it is not appropriate to diverse traffic patterns. In this paper, we propose a traffic-aware multipath routing (TAMR). By managing an overlaid topology comprised of two different topologies without additional overhead, TAMR can dynamically choose a proper routing protocol according to traffic patterns and it can improve network reliability. Besides, TAMR is suitable for 6LoWPAN, because it does not need to store global routing state and generates low control overhead. In order to evaluate the performance, we have conducted the simulation by comparing with representative routing protocols in 6LoWPAN. The results show the overall performance of TAMR surpasses others in terms of hop count, packet delivery ratio, number of control packets, and memory usage.

Traffic-aware stateless multipath routing for fault-tolerance in IEEE 802.15.4 wireless mesh networks

Single-path routing is widely used in wireless networks due to low resource consumption. However, it is vulnerable to link failure because such a failure may adversely affect an entire path. To overcome this, multipath routing has been proposed providing fault-tolerance. In this paper, we propose a novel multipath routing protocol called traffic-aware stateless multipath routing (TSMR) based on an overlaid tree topology comprising two topologies, namely, bounded degree tree (BDT) and root-oriented directional tree (RODT). BDT is strong on reducing routing overhead, and RODT is resilient against lossy links. By synergistically overlaying them, TSMR dynamically selects the local optimal path according to the given traffic flow and the failure on the primary path. In particular, TSMR enables stateless and low overhead routing despite multipath routing by keeping only one-hop neighbors to maintain multiple paths. To evaluate TSMR, we conducted simulations with a shadowing model reflecting lossy links, and compared with single and multipath routing protocols, such as ZTR, STR, AODV, and RPL. The simulation results show that the overall performance of TSMR surpasses that of others for packet delivery ratio, end-to-end delay, control overhead, memory consumption, and power consumption regardless of network size, number of sessions, and traffic flow.

Cross domain communication in the web of things: a new context for the old problem

Cross domain communication has been a long-discussed subject in the field of web-based application, especially for any sort of mashups where a single web app combines resources from different locations. This issue becomes more important in the Web of Things context, where every physical resources are exposed to the Web and mashed up by other web applications. In this paper we demonstrate a use case in which cross domain communication is applied in the Web of Things using the HTML5 Cross Document Messaging API (HTML5CDM). In addition, we contribute an advanced implementation of HTML5CDM that brings RESTful communication model to HTML5CDM and supports better concurrent message exchange, which we believe will be of much benefit to web developers. In addition, a time/space evaluation that measures CPU and Memory usage for the developed HTML5CDM library is carried out and the results has proved our implementations practicability.