Tsung-Han Lee

Energy-Efficient Oriented Routing Algorithm in Wireless Sensor Networks

The design and implementation of healthcare system using sensor network technology has been one of the most active research topics currently. The research on wireless sensor network mostly focuses on energy saving, such as duty cycle scheduling, and path routing, such as routing protocol for low power and lossy networks (RPL) which however only takes into account a single metric, reliability or energy, as routing decision. If RPL only considers the reliability metric, nodes will suffer from uneven energy. If it only considers the energy metric, nodes will suffer from the rise of packet loss ratio. In this paper, we propose an energy-oriented routing mechanism to improve RPL routing protocol by combining the expected transmission count (ETX) and remaining energy metrics. The simulation will be conducted to analyze the performance of the proposed mechanism.

QoS-aware path switching for VoIP traffic using SCTP

Voice over Internet protocol (VoIP) has been a prevalent multimedia service nowadays. It allows us to transmit voice data over IP networks. However, quality of service (QoS) is a major challenge to VoIP services. It must provide similar quality to traditional public switched telephone network or cellular phone services. Therefore, QoS related protocols have become important for real-time applications. Multi-protocol label switch (MPLS) is one of the important techniques to improve the network performance from QoS point of view. It employs label swapping to speed up packet forwarding. However, when a large number of users utilize VoIP services, the network congestion issue still exists. It causes delay, jitter and packet loss that affect VoIP QoS. In this paper, we propose a QoS-aware path switching strategy by using stream control transmission protocol (SCTP) in MPLS network to improve the VoIP traffic. This was done by employing SCTP selective acknowledgment mechanism to report the transmission parameters of primary path and to determine the criteria to switch to backup path. Simulation results show significant improvement in VoIP QoS.

A Handover Mechanism Using IEEE 802.21 in Heterogeneous Wireless Networks

The IEEE 802.21 framework is a novel standard and the scope of this standard is to optimize and facilitate handover in heterogeneous networks. In this paper, we propose a handover mobility management by using the IEEE 802.21 to solve some handover issues, such as handover delay and packet loss, in homogeneous and heterogeneous networks. By setting certain signal thresholds and probability confidence to trigger the Link Going Down event, the proposed handover mechanism is capable of providing better handover efficiency and reducing the handover delay and possible packet loss during handover. The NS-2 simulation is conducted to verify the performance of our handover mobility management across WLAN and WiMAX heterogeneous networks.

RSSI-based IPv6 routing metrics for RPL in low-power and lossy networks

Wireless sensor network (WSN) have been the subject of significant research over the recent years. IPv6 over low-power wireless personal area network (6LoWPAN) has been proposing the use of IPv6 solutions in WSN to communicate using Internet protocol (IP). The 6LoWPAN is proposed by IETF which provides IPv6 header compression, fragmentation and reassembly of IPv6 packets over IEEE 802.15.4 networks. In this paper, we present an experimental study on the impact between the packet length of IPv6 in network layer and number of fragments in MAC layer. We conducted our experiments in Contiki test-bed to analysis 6LoWPAN performance with different RSSI and payload size. Experiment results highlight the trade-off between the length of IPv6 UDP frame sand link quality for 6LoWPAN performance. Finally, a RSSI-based IPv6 routing metrics for RPL has been proposed based-on our experiment results to enhance the transmission performance in 6LoWPAN.

A Lightweight Intrusion Detection Scheme Based on Energy Consumption Analysis in 6LowPAN

6LoWPAN is one of Internet of Things standard, which allows IPv6 over the low-rate wireless personal area networks. All sensor nodes have their own IPv6 address to connect to Internet. Therefore, the challenge of implementing secure communication in the Internet of Things must be addressed. There are various attack in 6LoWPAN, such as Denial-of-service, wormhole and selective forwarding attack methods. And the Dos attack method is one of the major attacks in WSN and 6LoWPAN. The sensor node’s energy will be exhausted by these attacks due to the battery power limitation. For this reason, security has become more important in 6LoWPAN. In this paper, we proposed a lightweight intrusion detection model based on analysis of node’s consumed in 6LowPAN. The 6LoWPAN energy consumption models for mesh-under and route-over routing schemes are also concerned in this paper. The sensor nodes with irregular energy consumptions are identified as malicious attackers. Our simulation results show the proposed intrusion detection system provides the method to accurately and effectively recognize malicious attacks.

Modeling and Performance Analysis of Route-Over and Mesh-Under Routing Schemes in 6LoWPAN

6L0WPAN is an IPv6 adaptation layer that defines Internet Protocols over low power, low data rate devices such as IEEE 802.15.4. It is difficult to implement because the size of IPv6 packet is much larger than the packet size of IEEE 802.15.4 data link layer. In order to solve this problem, the IETF 6LoWPAN working group introduces the adaptation layer between network and data link layers. It provides header compression to reduce transmission overhead, fragmentation and reassembly of IPv6 packet. In addition, the routing schemes in 6LoWPAN can be divided into two categories: mesh-under and route-over. The main difference between these two schemes depends on how the packets or fragments are processed before being forwarded. In this paper, we present an analysis between these two routing schemes and comparing their IP packet successful transmission probabilities. Moreover, while the number of competing nodes increases, the probability of successful transmission will decrease due to the CSMA/CA mechanism.

Modeling of Location Estimation for Object Tracking in WSN

Location estimation for object tracking is one of the important topics in the research of wireless sensor networks (WSNs). Recently, many location estimation or position schemes in WSN have been proposed. In this paper, we will propose the procedure and modeling of location estimation for object tracking in WSN. The designed modeling is a simple scheme without complex processing. We will use Matlab to conduct the simulation and numerical analyses to find the optimal modeling variables. The analyses with different variables will include object moving model, sensing radius, model weighting value α, and power-level increasing ratio k of neighboring sensor nodes. For practical consideration, we will also carry out the shadowing model for analysis.

Avoiding Collisions Between IEEE 802.11 and IEEE 802.15.4 Using Coexistence Inter-Frame Space

Recently, more and more wireless networks have been deployed and start provide varies services to customers. Such as smart-phones integrate heterogeneous wireless devices, it may cause unintended interactions between multiple radios using difference radio access technologies. Thus, heterogeneous wireless network will be the trend of future network. The Co-channel interference problem in heterogeneous wireless networks is more and more important. This paper focus on the coexistence problem between IEEE 802.11b/g/n and IEEE 802.15.4 protocols in the ISM 2.4 GHz band. The performance impact on IEEE 802.15.4 network under IEEE 802.11 wireless network has been analysis, and results show that IEEE 802.15.4 has serious collision problem if there has no appropriate scheduling mechanisms among two wireless protocols. A CIFS (Coexistence Inter-Frame Space) has been proposed in this paper to effectively enhance the IEEE 802.15.4 transmission probability which is implemented in IEEE 802.11 nodes to observe the transmission opportunity for IEEE 802.15.4 under wireless coexistence environment.

A QoS Channel Allocation Scheme for Enhancing the Reliability in 6TiSCH Networks

The recent IEEE 802.15.4-2015 standard proposes a number of Medium Access Control (MAC) layer protocols for low-power and lossy networks. The Timeslotted Channel Hopping (TSCH) is one of the proposed MAC operation modes, which take the advantage of channel hopping to make the transmissions more reliable and deterministic. In TSCH, slotframe is sliced into a timeslots and random channel hopping is used to mitigate the effects of co-channel interference and multipath fading. In this paper, we focus on the issue of random channel hopping in the error-prone wireless channel condition. In this research, a QoS Channel Allocation Scheme (QCAS) is proposed to enhance the reliability of emergency packet transmission in 6TiSCH networks. Based on our simulation results, we have observed that the proposed QCAS can achieve higher reliability of transmission over selected channel to provide higher throughput and higher delivery ratio than the original TSCH.

Priority-based scheduling using best channel in 6TiSCH networks

Many industrial wireless sensor networks deploy the IEEE 802.15.4-2015 standard with low power consumption and the Internet networking capabilities. The time-slotted channel hopping (TSCH) is an amendment to the medium access control protocol defined by the IEEE 802.15.4 standard. Furthermore, the Internet engineering task force (IETF) defines an architecture for IPv6 over the TSCH mode of IEEE 802.15.4 (6TiSCH) to provide deterministic properties on wireless sensor networks. The TSCH leverages the scheduled time slot to achieve low power operation and frequency hopping to combat external interference and multi-path fading. Although TSCH provides the channel hopping mechanism to increase transmission reliability, it is still susceptible to periodic interference for the specific frequency. In this research, we focus on the issue of random channel hopping in the error-prone wireless channel condition and the scheduling for different service requirements. We propose a priority-based scheduling using best channel (P-SBC) mechanism for periodic sensing data and emergency packets transmission in 6TiSCH networks. The simulation results show that the proposed P-SBC achieves higher reliability with significantly lower end-to-end latency for emergency packets transmission as compared to TSCH standard.