Search

The IEEE 802.15.4 is a popular standard used in wireless sensor networks (WSNs) and the Internet of Things (IoT) applications. In these networks, devices are organized into groups formally known as personal area networks (PAN) which require a bootstrap procedure to become operational. Bootstrap plays a key role in the initialization and maintenance of these networks. For this reason, this work presents our implementation and performance analysis for the ns-3 network simulator. Specifically, this bootstrap implementation includes the support of three types of scanning mechanisms (energy scan, passive scan, and active scan) and the complete classic association mechanism described by the standard. Both of these mechanisms can be used independently by higher layers protocols to support network initialization, network joining, and maintenance tasks. Performance evaluation is conducted in total network association time and packet overhead terms. Our source code is documented and publicly available in the latest ns-3 official release. [ABSTRACT FROM AUTHOR]

In this paper, wireless feedback control of multiple machines over a beacon-enabled IEEE 802.15.4 network is considered. In the beacon-enabled IEEE 802.15.4 network, beacons periodically structure superframes on the time axis, and each superframe consists of a contention access period (CAP) and a contention free period (CFP). In the CAP, a carrier sense multiple access/collision avoidance (CSMA/CA) is used; in the CFP, a guaranteed time slot (GTS)-based time division multiple access is used. Because of collision and backoff periods of packet transmission, the probability of communication failure in the CAP is greater than that in the CFP; however, the number of available GTSs is limited to seven by the standard. In order to improve the control performance of wireless feedback control, the controller must effectively allocate GTSs to transmit control input and state feedback of controlled machines. We provide a simple but efficient idea that takes both the feedback control mechanism and packet transmission mechanism of the CAP and CFP into consideration to better allocate GTSs. We propose a superior GTS allocation method that fully conforms to the IEEE 802.15.4 standard and show that the proposed method can further improve control performance.

For data frame transmissions in beacon‐enabled mode, an IEEE 802.15.4 node performs two consecutive clear channel assessments (CCAs) to sense the channel after back off. Here, the authors study what would happen if the medium access control (MAC) layer performs only one CCA instead. Although it is apparent that the frame transmission cycle would be shortened with single CCA, it is not straightforward to assess the effect of single CCA on the overall transmission energy. A Markov chain‐based MAC operation model is therefore constructed to analyse single‐CCA‐based MAC layer parameters. A combined physical (PHY) and MAC layer energy model is formulated next. It was found that the single CCA‐based MAC outperforms its standard double CCA‐based counterpart from the energy efficiency perspective. [ABSTRACT FROM AUTHOR]

This paper presents a wireless fault detection system for industrial motors that combines vibration, motor current and temperature analysis, thus improving the detection of mechanical faults. The design also considers the time of detection and further possible actions, which are also important for the early detection of possible malfunctions, and thus for avoiding irreversible damage to the motor. The remote motor condition monitoring is implemented through a wireless sensor network (WSN) based on the IEEE 802.15.4 standard. The deployed network uses the beacon-enabled mode to synchronize several sensor nodes with the coordinator node, and the guaranteed time slot mechanism provides data monitoring with a predetermined latency. A graphic user interface offers remote access to motor conditions and real-time monitoring of several parameters. The developed wireless sensor node exhibits very low power consumption since it has been optimized both in terms of hardware and software. The result is a low cost, highly reliable and compact design, achieving a high degree of autonomy of more than two years with just one 3.3 V/2600 mAh battery. Laboratory and field tests confirm the feasibility of the wireless system. [ABSTRACT FROM AUTHOR]

Modern manufacturing processes rely on industrial Wireless Sensor Networks (WSN) for the monitoring of parameters critical for a broad range of applications. One of the most important standards used for the implementation of industrial WSN is the IPv6 over Low power Wireless Personal Area Networks (6LoWPAN). This standard provides wireless internet connectivity, warranting interoperability with already existing infrastructures. Due to the increasing importance of the process monitoring in the manufacturing domain, it is required that the 6LoWPAN transmission control mechanisms are efficient, robust and that they guarantee real-time responses with low data losses. This paper presents a packet scheduler for real-time 6LoWPAN wireless networks in manufacturing systems that adapts wireless scheduling mechanisms and decision algorithms to the IEEE 802.15.4 beacon-enabled mode. In previous works, the scheduling algorithm does not change during the packet scheduling process. The work described in this paper proposes a new approach to the design of scheduling mechanisms by presenting a scheduling system that can adapt to the dynamic wireless traffic of industrial WSN. The system implemented manages the channel access by allocating Guaranteed Time Slots to sensor nodes according to the priority given by scheduling algorithms that are selected according to the traffic condition of the network. [ABSTRACT FROM AUTHOR]

IEEE 802.15.4 targets low data rate communication with limited power devices and cheap wireless networking solutions. In recent years both industry and academia are attracted to IEEE 802.15.4 because of its applicability in wireless sensor networks and wireless body area networks. An important feature of IEEE 802.15.4 is its very low duty cycle operation for conserving energy consumption of sensor device. Super-frame structure of IEEE 802.15.4 defines the duty cycle of nodes. The super-frame structure is based on two parameters: beacon order (BO) and super-frame order (SO). The performance of an IEEE 802.15.4 network depends on the values of BO and SO. These values depict the energy consumption, throughput, node discovery and latency of communication. IEEE 802.15.4 uses fixed BO and SO values which can be carefully chosen to meet the network requirements. In this paper, an extensive survey of dynamic super-frame adjustment algorithms is presented. The survey focuses on beacon-enabled star topology of IEEE 802.15.4 and studies the impact of aforementioned algorithms for various applications. Also, the survey categorizes common IEEE 802.15.4 applications based on their requirements for super-frame adjustment. A brief simulation analysis is included in this survey to highlight the impact of BO and SO on the network performance. [ABSTRACT FROM AUTHOR]

This paper presents a wireless fault detection system for industrial motors that combines vibration, motor current and temperature analysis, thus improving the detection of mechanical faults. The design also considers the time of detection and further possible actions, which are also important for the early detection of possible malfunctions, and thus for avoiding irreversible damage to the motor. The remote motor condition monitoring is implemented through a wireless sensor network (WSN) based on the IEEE 802.15.4 standard. The deployed network uses the beacon-enabled mode to synchronize several sensor nodes with the coordinator node, and the guaranteed time slot mechanism provides data monitoring with a predetermined latency. A graphic user interface offers remote access to motor conditions and real-time monitoring of several parameters. The developed wireless sensor node exhibits very low power consumption since it has been optimized both in terms of hardware and software. The result is a low cost, highly reliable and compact design, achieving a high degree of autonomy of more than two years with just one 3.3 V/2600 mAh battery. Laboratory and field tests confirm the feasibility of the wireless system.

One of the major concerns in wireless sensor networks is energy saving due to lack of power sources. IEEE 802.15.4 provides CSMA/CA to reduce the possibility of a collision by checking whether the medium is in use. This checking operation is CCA (Clear Channel Assessment). Currently, IEEE 802.15.4 defines CCA as two consecutive channel assessment for slotted CSMA/CA. Obviously, always performing the channel assessment twice is wasteful and inefficient, since it requires more delay and energy consumption than when the channel assessment is performed once. In this paper, we propose a SCCA (Short Clear Channel Assessment) scheme which performs the channel assessment once, not twice, with minimal effort. Simulation results show that the SCCA operation provides reduced CCA processing time and energy consumption than when IEEE 802.15.4 CCA is used. [ABSTRACT FROM AUTHOR]

This paper proposes enhancements to IEEE 802.15.4 Beacon-Enabled Mode that provide improved network performance and lower power consumption for low data rate applications. The proposed mode utilizes a Synchronous Low Power Listening technique that allows nodes to sleep for multiple Beacon Intervals and subsequently recover Beacon synchronization in a power efficient manner. The proposed mode also incorporates a Periodic Wakeup scheme that allows nodes to transmit at scheduled times during the inactive period. The proposed Enhanced Mode is backward compatible and inter-operable with the original standard. Simulation results show that the proposed Enhanced Mode reduces the power consumption overhead of synchronization by more than 50% for applications with low data rates compared with standard Beacon-Enabled mode. End-to-end delay and packet loss rate are reduced by more than 90% compared with standard Beacon-Enabled mode. The proposal can adapt to the change of traffic load, and prolong the lifetime of the PAN Coordinator by 1-5 times compared to standard Beacon Enabled mode. [ABSTRACT FROM AUTHOR]