https://ir.nctu.edu.tw:443/bitstream/11536/15393/1/000299669400001.pdf

Review: From wireless sensor networks towards cyber physical systems

The present electric power system structure has lasted for decades; it is still partially proprietary, energy-inefficient, physically and virtually (or cyber) insecure, as well as prone to power transmission congestion and consequent failures. Recent efforts in building a smart grid system have focused on addressing the problems of global warming effects, rising energy-hungry demands, and risks of peak loads. One of the major goals of the new system is to effectively regulate energy usage by utilizing the backbone of the prospectively deployed Automatic Meter Reading (AMR), Advanced Meter Infrastructure (AMI), and Demand Response (DR) programs via the advanced distribution automation and dynamic pricing models. The function of the power grid is no longer a system that only supplies energy to end users, but also allows consumers to contribute their clean energy back to the grid in the future. In the meantime, communications networks in the electric power infrastructure enact critical roles. Intelligent automation proposed in smart grid projects include the Supervisory Control And Data Acquisition/Energy Management Systems (SCADA/EMS) and Phasor Management Units (PMU) in transmission networks, as well as the AMR/AMI associated with field/neighborhood area networks (FAN/NAN) and home area networks (HAN) at the distribution and end-use levels. This article provides an overview of the essentials of the progressive smart grid paradigm and integration of different communications technologies for the legacy power system. Additionally, foreseeable issues and challenges in designing communications networks for the smart grid system are also rigorously deliberated in this paper.

/pdf/the-progressive-smart-grid-system-from-both-power-and-7oc2736nf1.pdf

The Progressive Smart Grid System from Both Power and Communications Aspects

IEEE 802.15.4 is the de facto standard for Wireless Sensor Networks (WSNs) that outlines the specifications of the PHY layer and MAC sub-layer in these networks. The MAC protocol is needed to orchestrate sensor nodes access to the wireless communication medium. Although distinguished by a set of strengths that contributed to its popularity in various WSNs, IEEE 802.15.4 MAC suffers from several limitations that play a role in deteriorating its performance. Also, from a practical perspective, 80.15.4-based networks are usually deployed in the vicinity of other wireless networks that operate in the same ISM band. This means that 802.15.4 MAC should be ready to cope with interference from other networks. These facts have motivated efforts to devise improved IEEE 802.15.4 MAC protocols for WSNs. In this paper we provide a survey for these protocols and highlight the methodologies they follow to enhance the performance of the IEEE 802.15.4 MAC protocol.

A Survey of Beacon-Enabled IEEE 802.15.4 MAC Protocols in Wireless Sensor Networks

A Wireless Body Area Network (WBAN) is a collection of low-power and lightweight wireless sensor nodes that are used to monitor the human body functions and the surrounding environment. It supports a number of innovative and interesting applications, including ubiquitous healthcare and Consumer Electronics (CE) applications. Since WBAN nodes are used to collect sensitive (life-critical) information and may operate in hostile environments, they require strict security mechanisms to prevent malicious interaction with the system. In this paper, we first highlight major security requirements and Denial of Service (DoS) attacks in WBAN at Physical, Medium Access Control (MAC), Network, and Transport layers. Then we discuss the IEEE 802.15.4 security framework and identify the security vulnerabilities and major attacks in the context of WBAN. Different types of attacks on the Contention Access Period (CAP) and Contention Free Period (CFP) parts of the superframe are analyzed and discussed. It is observed that a smart attacker can successfully corrupt an increasing number of GTS slots in the CFP period and can considerably affect the Quality of Service (QoS) in WBAN (since most of the data is carried in CFP period). As we increase the number of smart attackers the corrupted GTS slots are eventually increased, which prevents the legitimate nodes to utilize the bandwidth efficiently. This means that the direct adaptation of IEEE 802.15.4 security framework for WBAN is not totally secure for certain WBAN applications. New solutions are required to integrate high level security in WBAN.

A Study of IEEE 802.15.4 Security Framework for Wireless Body Area Networks

This paper develops and compares different sensor network architecture designs that can be used for monitoring underwater pipeline infrastructures. These architectures are underwater wired sensor networks, underwater acoustic wireless sensor networks, RF (Radio Frequency) wireless sensor networks, integrated wired/acoustic wireless sensor networks, and integrated wired/RF wireless sensor networks. The paper also discusses the reliability challenges and enhancement approaches for these network architectures. The reliability evaluation, characteristics, advantages, and disadvantages among these architectures are discussed and compared. Three reliability factors are used for the discussion and comparison: the network connectivity, the continuity of power supply for the network, and the physical network security. In addition, the paper also develops and evaluates a hierarchical sensor network framework for underwater pipeline monitoring.

https://www.mdpi.com/1424-8220/11/11/10738/pdf

Sensor network architectures for monitoring underwater pipelines.

Two mechanisms are proposed to enhance throughput and energy efficiency of IEEE 802.15.4 CSMA-CA. The first one is an enhanced collision resolution (ECR) mechanism that adjusts the backoff exponent (BE) based on both consecutive clear channel assessment (CCA) busy results and a packet transmission. The second one is an enhanced backoff (EB) mechanism that shifts the range of backoff counters by utilizing the CCA outcome. The simulation results demonstrate that the proposed mechanisms significantly enhance both throughput and energy efficiency of IEEE 802.15.4

An Enhanced CSMA-CA Algorithm for IEEE 802.15.4 LR-WPANs

This letter proposes the enhanced hierarchical routing protocol (EHRP) for ZigBee mesh networks. The EHRP finds the shortest hierarchical path based on the ZigBee hierarchical addressing scheme. The EHRP provides efficient and reliable routing paths. In addition, the EHRP is completely compatible with ZigBee v.1.0 standard. Simulation results demonstrate that the EHRP reduces routing overhead and route discovery delay of ZigBee mesh networks significantly compared with the hierarchical routing protocol (HRP) defined in ZigBee v1.0.

EHRP: Enhanced hierarchical routing protocol for zigbee mesh networks ee

In this paper, we propose a near-ultrasound chirp signal-based communication for the TV's 2nd screen services. While near-ultrasound (with under 20 kHz frequency) communication has been developed for various applications recently, none of the previous work provides a perfect solution for 2nd screen services between TVs and smart devices. This is due mainly to the following real world challenges. The embedded signal in TV contents should be successfully received in a typical TV-watching environment by (i) delivering information at least at 15 bps with significantly low volume to avoid human perception, (ii) despite the presence of ambient noise, e.g., a tick, a snap, or a knock. To fulfill (i), we design chirp quaternary orthogonal keying (QOK) symbols. Especially, we aim to minimize inter-symbol interference (ISI) effects by symbol design in order to completely eliminate guard intervals. To resolve (ii), we propose the novel J-shape detection algorithms for both frame synchronization and carrier sensing. The proposed modem achieves almost zero frame error rate on a smartphone 2.7 m away from the TV even with minimal receive sound pressure level of 35 dBSPL, i.e., the noise level in a very quiet room. Moreover, throughout experiments and log analysis of 2nd screen service deployed in a nation-wide TV broadcasting system, J-shape detection algorithms are proven to achieve highly resilient performance for both frame synchronization and carrier sensing compared to previous schemes.

Near-ultrasound communication for TV's 2nd screen services

The number of frequency channels specified for IEEE 802.15.4 low-rate wireless personal area networks (LR-WPANs) does not suffice to operate a variety of collocated WPAN applications that the standard is targeting. To overcome this limit, we introduce virtual channel, a novel concept to increase the number of available channels by efficiently managing given spectral and temporal resources. A virtual channel is created by scheduling a superframe and selecting a logical channel. This extends the notion of a channel from spectral domain to spectral and temporal domain. Specifically, we propose a superframe scheduler using throughput estimation (SUTE) of the IEEE 802.15.4 carrier sense multiple access with collision avoidance (CSMA/CA). In addition, nearest vacancy search (NEVS) is proposed, both of which are for temporal efficiency of the collocation. For both spectral and temporal efficiency, virtual channel selector (VCS) is proposed. The simulation results show that a remarkable improvement on the collocation efficiency of IEEE 802.15.4 can be achieved by our proposals. Moreover, this study also reveals the fundamental drawback of the current standard in terms of the collocation efficiency that the beacon interval and superframe duration are adjustable only by exponent parameters.

Improving Spectral and Temporal Efficiency of Collocated IEEE 802.15.4 LR-WPANs

The number of channels specified for IEEE 802.15.4 low-rate wireless personal area networks (LR-WPANs) is too few to operate many applications of WPANs in the same area. To overcome this limit, we introduce virtual channel, a novel concept to increase the number of available channels when various WPAN applications coexist. A virtual channel is basically created via superframe scheduling within the inactive periods in a logical channel preoccupied by other WPANs. To maximize the coexistence capability of WPANs using virtual channels, we propose (1) least collision superframe scheduler (LC-scheduler), (2) less complex heuristics, and (3) virtual channel selector (VCS) to efficiently manage multiple available logical channels. In addition, a simple but practical synchronization method is developed to compensate different time drifts among coexisting WPANs. The simulation results demonstrate that a remarkable improvement on the coexistence capability of the 802.15.4 can be achieved through the proposed schemes.

/pdf/virtual-channel-management-for-densely-deployed-ieee-802-15-4m9wghnr8r.pdf

Jae Yeol Ha

Papers

An Enhanced CSMA-CA Algorithm for IEEE 802.15.4 LR-WPANs

EHRP: Enhanced hierarchical routing protocol for zigbee mesh networks ee

Near-ultrasound communication for TV's 2nd screen services

Improving Spectral and Temporal Efficiency of Collocated IEEE 802.15.4 LR-WPANs

Virtual channel management for densely deployed IEEE 802.15.4 LR-WPANs