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The IEEE 802.15.4 standard for wireless sensor networks (WSNs) can support energy efficient, reliable, and timely packet transmission by tuning the medium access control (MAC) parameters macMinBE, macMaxCSMABackoffs, and macMaxFrameRetries. Such a tuning is difficult, because simple and accurate models of the influence of these parameters on the probability of successful packet transmission, packet delay, and energy consumption are not available. Moreover, it is not clear how to adapt the parameters to the changes of the network and traffic regimes by algorithms that can run on resource-constrained nodes. In this chapter, a generalized Markov chain is proposed to model these relations by simple expressions without giving up the accuracy. In contrast to previous work, the presence of limited number of retransmissions, acknowledgments, unsaturated traffic, and packet size is accounted for. The model is then used to derive an adaptive algorithm for minimizing the power consumption while guaranteeing reliability and delay constraints in the packet transmission. The algorithm does not require any modification of the IEEE 802.15.4 standard and can be easily implemented on network nodes. Numerical results show that the analysis is accurate and that the proposed algorithm satisfies reliability and delay constraints, and ensures a longer lifetime of the network under both stationary and transient network conditions. [ABSTRACT FROM AUTHOR]

Control applications over wireless sensor networks (WSNs) require timely, reliable, and energy efficient communications. This is challenging because reliability and latency of delivered packets and energy are at odds, and resource constrained nodes support only simple algorithms. In this chapter, a new system-level design approach for protocols supporting control applications over WSNs is proposed. The approach suggests a joint optimization, or co-design, of the control specifications, networking layer, the medium access control layer, and physical layer. The protocol parameters are adapted by an optimization problem whose objective function is the network energy consumption, and the constraints are the reliability and latency of the packets as requested by the control application. The design method aims at the definition of simple algorithms that are easily implemented on resource constrained sensor nodes. These algorithms allow the network to meet the reliability and latency required by the control application while minimizing for energy consumption. The design method is illustrated by two protocols: Breath and TREnD, which are implemented on a test-bed and compared to some existing solutions. Experimental results show good performance of the protocols based on this design methodology in terms of reliability, latency, low duty cycle, and load balancing for both static and time-varying scenarios. It is concluded that a system-level design is the essential paradigm to exploit the complex interaction among the layers of the protocol stack and reach a maximum WSN efficiency. [ABSTRACT FROM AUTHOR]

The current specification for IEEE 802.15.4 beacon-enabled networks does not define how active and sleep schedules should be configured in order to achieve the optimal network performance in all traffic conditions. Several algorithms exist in the literature that dynamically vary these schedules based on traffic load estimations. But it is still uncertain how these adaptive schemes perform with regard to each other as their performance has only been compared with the standard beacon mode. In this paper, we compare the current state-of-the-art schemes, and with the objective of overcoming the performance deficiencies shown by previous approaches, we introduce DCLA, an adaptive duty-cycle scheme for IEEE 802.15.4 beacon-enabled Wireless Sensor Networks (WSN) that employs a reinforcement learning technique. Simulation results show that the proposed scheme achieves the best overall network performance for a wide range of traffic conditions and performance parameters when compared with existing IEEE 802.15.4 duty-cycle adaptation schemes. [ABSTRACT FROM AUTHOR]

Wireless Sensor Networks (WSN) are a very promising solution for industrial monitoring applications in terms of safety, costs, efficiency and productivity. However, in order to move from the adopted manual/wired designs to wireless designs, certain guarantees must be assured, especially in terms of reliability, bandwidth and message transmission delays. Although quality of service (QoS) requirements can be satisfied in star based topologies using the Guaranteed Time Slots (GTS) feature of the IEEE802.15.4 standard, GTS communications in multihop scenarios are currently limited by IEEE802.15.4 beacon scheduling designs and peer-to-peer GTS allocation methods. This restricts applications to run over sensors that are within radio range of the network coordinator. In this work, we propose a distributed IEEE802.15.4 MAC modification to improve GTS usability and scalability in mesh networks. Also, we propose a reactive multihop GTS allocation technique based on our MAC modification to ensure reliable and latency aware end-to-end communications. Results show that our techniques improve greatly the reliability of multihop GTS communications. [ABSTRACT FROM AUTHOR]

IP based Wireless Sensor Network (IP-WSN) is gaining tremendous importance because of its broad range of commercial applications in health care, building & home automation, asset management, environmental monitoring, security & safety and industrial automation. A network-based mobility management protocol called Proxy Mobile IPv6 has been standardized by the IETF NETLMM working group, and is starting to pay close attention among the telecommunication and Internet communities. Since host based IP mobility protocol is not feasible for the low power and low cost sensor node, network based mobility management protocol will be well suited for IP-WSN. In this paper we propose SPMIPv6 architecture, respective message formats and analyze the signaling cost and finally evaluate its performance. The result shows that the SPMIPv6 has lower signaling cost and packet delivery cost and it can improve the handover performance of UDP and TCP than the other mobility management protocol. [ABSTRACT FROM AUTHOR]

With the advent of the new very powerful sensors, the WSNs have extended their scope from simple isolated networks to multiple networks interconnected through Internet. To model these new complex networks, a level of abstraction higher with respect to the one adopted by the simulation models of the original sensor networks is required. In this paper we describe an alternative approach to the one used in the original simulation models of WSN which is based on Queueing Network (QN) technique. This technique is particularly oriented to the solution of capacity planning problems. We demonstrate through simulations that the results provided by the proposed QN model are reliable by comparing them to the ones obtained by a similar model implemented with the widely adopted network simulator ns-2. The results show a very good agreement between the values provided by the two modeling techniques. [ABSTRACT FROM AUTHOR]

Energy efficient Internet Protocol based smart Wireless Sensor Networks (IP-WSN) are gaining tremendous importance because of its broad range of commercial applications in health care, building & home automation, environmental monitoring, security & safety and industrial automation. In all of these applications mobility of sensor node with special attention to energy constraints is an indispensible part. Host based mobility management protocol is inherently unsuitable for energy inefficient IP-WSN. So network-based mobility management protocol can be an alternative to the mobility supported IP-WSN. In this regard, Proxy Mobile IPv6 has been standardized by the IETF NETLMM working group, and is starting to pay close attention among the telecommunication and Internet communities. In this paper we propose energy efficient Sensor Network based PMIPv6 protocol called Sensor Proxy Mobile IPv6 (SPMIPv6). We present SPMIPv6 architecture, respective message formats and analyze the energy dissipation and finally evaluate its performance. [ABSTRACT FROM AUTHOR]

6LoWPAN defines how to carry IPv6 packets over IEEE 802.15.4 low power wireless or sensor networks. Limited bandwidth, memory and energy resources require a careful application of IPv6 in a LoWPAN. The IEEE 802.15.4 standard defines a maximum frame size of 127 bytes that decreases to 102 bytes considering the header overhead. A further reduction is due to the security, network and transport protocols header overhead that, in case of IPv6 and UDP, leave only 33 bytes for application data. A compression algorithm is necessary in order to reduce the overhead and save space in data payload. This paper describes and compares the proposed IPv6 header compression mechanisms for 6LoWPAN environments. [ABSTRACT FROM AUTHOR]

As the number of wireless devices sharing the unlicensed 2.4 GHz ISM band increases, interference is becoming a problem of paramount importance. We experimentally investigate the effects of controlled 802.11b interference as well as realistic urban RF interference on packet delivery performance in IEEE 802.15.4 body area networks. Our multi-channel measurements, conducted with Tmote Sky sensor nodes, show that in the low-power regime external interference is typically the major cause for substantial packet loss. We report on the empirical correlation between 802.15.4 packet delivery performance and urban WLAN activity and explore 802.15.4 cross-channel quality correlation. Lastly, we examine trends in the noise floor as a potential trigger for channel hopping to detect and mitigate the effects of interference. [ABSTRACT FROM AUTHOR]

Among the latest events of the wireless revolution, the fast-growing of ZigBee as a standard for WSN (Wireless Sensors Networks) is certainly one of these. ZigBee and 802.15.4 had been proving in the last years that they can achieve the results that Wi-Fi had achieved for high bit-rate wireless LANs and some large reliable deployments are now in place implementing ad-hoc WSN in critical applications. Therefore this paper will emphasize on the past, present and future features for ZigBee, taking a look on the feedback from previous implementations to finally design the next generations of WSN based on ZigBee. [ABSTRACT FROM AUTHOR]

The IEEE 802.15.4 standard defines a MAC association procedure that allows devices of a Wireless Personal Area Network (WPAN) to associate one each other in accordance to parent-child relationships. This standard can be adopted in Wireless Sensor Networks (WSNs) used to monitor environmental phenomena and to collect data in specific nodes named sinks. The ZigBee Alliance, with the Zig-Bee Specification, defines upper layers of a WSN architecture based on the IEEE 802.15.4. Tree shaped multi-sink networks can be formed by adopting in conjunction these two standards. A key aspect to be evaluated for these kind of networks is how their performance are affected by constraining some topological characteristics. In this paper, in accordance to the ZigBee Specification, we constraint the tree depth of a WSN and evaluate some performance metrics that have a remarkable relevance for WSNs. Moreover, we propose a new strategy to join an existing WPAN that allows a node to select a suitable coordinator to connect with. Performance results show the trade-off in the selection of the maximum tree depth. While benefits of having reduced tree depths can be measured during traffic delivery, due to a reduction of the energy consumption, a counter-party is the energy spent in the network formation that deeply depends on this topological parameter. Moreover, the maximum tree depth has also a great impact on the percentage of nodes that are able to join a network. [ABSTRACT FROM AUTHOR]

Industrials have been increasingly interested in sensor and actuator networks to monitor and control their installations. The recent IEEE 802.15.4 standard has been developed to address vital issues of these networks, such as limited battery power and low processing ca- pabilities. However, the standard does not meet all the requirements of industrial networks. For example, only some of the IEEE 802.15.4 nodes save energy, and the delay for a sensor to activate an actuator is not bounded. Our research on energy-efficient MAC protocol is divided into two parts: Part A consists in introducing a flexible, synchronized tree based MAC protocol called MaCARI and Part B deals with optimizations that can be performed within each star. This paper focuses on Part B, that is, on the intra-star MaCARI protocol. Our proposal is an incremental protocol with different options which increase respectively the previous one in terms of bandwidth and energy saving. A hardware prototyping of the last option has been done in order to validate our proposal. [ABSTRACT FROM AUTHOR]

Industrials have been increasingly interested in sensor and actuator networks to monitor and control installations. The recent IEEE 802.15.4 standard has been developed to address vital issues of these networks, such as limited battery power and low processing capabilities. However, the standard does not meet all the requirements of industrial networks. For example, only some of the IEEE 802.15.4 nodes save en-ergy, and the delay for the computer running the monitoring application to retrieve the sensor data or to activate an actuator is not bounded. Our research on energy-efficient MAC protocol is divided into two parts: Part A is the proposal of a flexible, synchronized tree-based MAC pro-tocol called MaCARI and Part B deals with optimizations that can be performed within each cell. This paper focuses on Part A, that is, on the description of the MaCARI protocol. MaCARI is designed to tolerate scheduled activities such as sensor data retrieval and unscheduled activities such as complex rout-ing. MaCARI achieves this flexibility by using a tree-based centralized mechanism. We show the benefits of MaCARI by ensuring all nodes sleep regularly and by proving that the maximum end-to-end delay is bounded. [ABSTRACT FROM AUTHOR]

In wireless personal area network, a channel is shared by a number of nodes. Therefore packet collision may take place and it degrades the throughput performance. To improve the throughput of slotted CSMA/CA in IEEE 802.15.4, we propose knowledge-based exponential backoff (KEB) scheme for enhancing channel utilization solely based on the locally available channel state information. In addition, we propose an analytical model of slotted channel access mechanism with finite retry and derive the theoretical throughput limit. In simulation experiments, we show that the existing MAC scheme, binary exponential backoff (BEB) scheme, operates very far from the theoretical limits due to increased time for negotiating channel access. Also performance results indicate that KEB shows significant improvement in throughput performance over BEB with the knowledge of the network status. [ABSTRACT FROM AUTHOR]

Among the latest events of the wireless revolution, the fast-growing of ZigBee as a standard for WSN (Wireless Sensors Networks) is certainly one of these. ZigBee and 802.15.4 had been proving in the last years that they can achieve the results that Wi-Fi had achieved for high bit-rate wireless LANs and some large reliable deployments are now in place implementing ad-hoc WSN in critical applications. Therefore this paper will emphasize on the past, present and future features for ZigBee, taking a look on the feedback from previous implementations to finally design the next generations of WSN based on ZigBee. [ABSTRACT FROM AUTHOR]