무선 센서 네트워크에서 간섭에 강인한 비컨 신호 추적 기법

학위논문 (석사)-- 서울대학교 대학원 : 전기·정보공학부, 2017. 2. 이용환.It is of great concern for commercial deployment of wireless sensor networks (WSNs) to securely construct a network while preventing a network association failure. ZigBee has been considered as an attractive protocol for the construction of cluster-tree structured WSNs due to its low-power and low-complexity features. However, it may not provide desired network connectivity in practical operation environments. In this thesis, we consider the beacon-tracking for network association in a beacon-enabled cluster-tree structured WSN. For the network association, ZigBee devices need to track a beacon frame transmitted from a candidate parent device (e.g., the coordinator or a router). ZigBee devices can avoid the presence of severe co-channel interference by means of channel hopping. However, a network joining device may not reliably track the beacon frame when ZigBee devices are in a channel hopping process. To alleviate the beacon tracking problem, we consider the beacon tracking using the beacon sequence number (BSN). The network joining device keeps the BSN of the received beacon frame during channel scanning and increases the BSN by one at every beacon interval. Thus, it can estimate which channel is used by the parent candidate device. We verify the proposed scheme by computer simulation. The proposed scheme can significantly reduce the beacon tracking failure, improving the self-networking performance.1. Introduction 1 2. System model 4 3. Proposed beacon tracking 8 4. Performance evaluation 11 5. Conclusions 16 References 17 초 록 20Maste

무선 센서 네트워크에서 에너지 효율적인 자가 치료 연구

학위논문 (석사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 이용환.One of key issues in the construction of wireless sensor network (WSN) is how efficiently sensor nodes re-subscribe to the network after networking failure. ZigBee has been considered as an attractive solution for the construction of cluster-tree structured WSNs due to its low-power and low-complexity features. However, it may be able to re-subscribes to the network through network rejoining which may require for large signaling overhead and time delay. In this thesis, we consider the design of a cluster-wise self-healing (CS) in a beacon-enabled cluster-tree structured WSN. When a router experience networking failure from its parent node, the proposed CS makes it maintain synchronization with its child nodes, preventing from orphan propagation to its child nodes. Meanwhile, it makes only the orphaned router initiate the re-subscription to the network on behalf of its child nodes. Thus, the proposed CS allows the network re-subscription through one re-subscription process of the orphaned cluster head, significantly reducing the recovery time and energy consumption for the recovery as well. We also design a backup link-aided self-healing (BL) where nodes select a parent node for the network subscription and also a back-up parent node for network re-subscription. The proposed BL can reduce the recovery time since it can minimizes the process for the selection of a new parent node and associated message exchanges for network re-subscription. Computer simulation and experimental results show that the proposed schemes can significantly reduce the energy consumption, recovery time and signaling overhead for network re-subscription.Abstract Contents List of Figures List of Tables 1. Introduction 2. System model 3. Previous works 3.1. Self-healing in ZigBee 3.2. Efficient self-healing process (ESP) 4. Proposed self-healing 4.1. Energy-efficient neighbor scan 4.2. Cluster-wise self-healing (CS) 4.3. Backup link aided self-healing (BL) 4.4. Messages for the proposed self-healing 5. Performance evaluation 6. Conclusions References 초 록Maste

Adaptive Resource Allocation for Wireless Body Sensor Networks

The IEEE 802.15.4 standard is an interesting technology for use in Wireless Body Sensor Networks (WBSN), where entire networks of sensors are carried by humans. In many environments the sensor nodes experience external interference for example, when the WBSN is operated in the 2.4 GHz ISM band and the human moves in a densely populated city, it will likely experience WiFi interference, with a quickly changing ``interference landscape''. In this thesis we propose Adaptive Resource Allocation schemes, to be carried out by the WBSN, which provided noticeable performance gains in such environments. We investigate a range of adaptation schemes and assess their performance both through simulations and experimentally

Optimized Asynchronous Multi-channel Neighbor Discovery

Abstract—We consider the problem of neighbor discovery in wireless networks with nodes operating in multiple frequency bands and with asymmetric beacon intervals. This is a challenging task when considering such heterogenous operation conditions and when performed without any external assistance. We present linear programming (LP) optimization and two strategies, named OPT and SWOPT, allowing nodes performing fast, asynchronous, and passive discovery. Our optimization is slotted based and determines a listening schedule describing when to listen, for how long, and on which channel. We compare our strategies with the passive discovery of the IEEE 802.15.4 standard. The results confirm that our optimization improves the performance in terms of first, average, and last discovery time. I