Data Rate Wireless Sensor Networks Research Articles

Design of a novel compact modified‐circular printed antenna for high data rate wireless sensor networks

This paper presents a novel compact circular patch Ultrawideband (UWB) antenna for sensor node applications. The microstrip-fed low-profile antenna comprises an elliptical ring slot, two crescent-shaped slots and two dumbbell-shaped slots in feedline. The antenna miniaturization is achieved by a novel combination of an elliptical ring slot, two crescent-shaped slots in circular patch. The proposed prototype has been fabricated on inexpensive FR4 substrate and the relative permittivity is (εr = 4.3) with 1.6 mm thickness. The overall size of the proposed miniaturized antenna is about (0.1 λr × 0.15 λr), where λr is the resonating wavelength of the lowest UWB frequency (ie, 3.1 GHz). The measured radiation performances of the proposed antenna are nearly an omnidirectional pattern in H-plane and bidirectional pattern in E-plane for all the frequencies in the whole UWB band. The development process of the antenna, radiation properties and group delay is completely analyzed and discussed.

Cross-layer energy model for beacon-enabled 802.15.4 networks

A transmitted frame in a wireless sensor network (WSN) may get corrupted due to erroneous bits in the frame, an event characterized at the physical (PHY) layer. The frame may also get dropped at medium access control (MAC) layer due to collision with other frames. As energy is wasted due to both, a combined cross-layer (PHY + MAC) model is needed for evaluating the energy for every successful transmission at frame/bit level. The model would also help in assessing how green a technique is, which might be proposed for PHY/ MAC layer of any WSN, by computing the improvement in energy efficiency. In this paper, we present a cross-layer energy model for communication in beacon-enabled 802.15.4 networks operating in star topology. IEEE 802.15.4 is the worldwide accepted WSN standard. Further, for status monitoring and event detection, which are the most common low data rate WSN applications, sensor nodes form a star topology where a central node sends periodic beacons to access data from all other nodes. Our model includes energy consumption for both source and destination node during the actual frame transmission as well as during the operations that precede frame transmission such as backoff and clear channel assessment (CCA). A two dimensional Markov model has been adopted for the purpose and parameters like average number of backoffs and average number of CCAs have been computed. Finally, the energy consumption per successful bit transmission is found by combining the collision probability in MAC layer and error probability in PHY layer. The results revealed that while the number of nodes in a WSN does not affect the energy consumption much, the frame length has a huge influence. Also, energy consumption rises considerably when acknowledgement is opted for.

Supervisory routing control for dynamic load balancing in low data rate wireless sensor networks

Routing protocols for Wireless Sensor Networks (WSN) are designed to select parent nodes so that data packets can reach their destination in a timely and efficient manner. Typically neighboring nodes with strongest connectivity are more selected as parents. This Greedy Routing approach can lead to unbalanced routing loads in the network. Consequently, the network experiences the early death of overloaded nodes causing permanent network partition. Herein, we propose a framework for load balancing of routing in WSN. In-network path tagging is used to monitor network traffic load of nodes. Based on this, nodes are identified as being relatively overloaded, balanced or underloaded. A mitigation algorithm finds suitable new parents for switching from overloaded nodes. The routing engine of the child of the overloaded node is then instructed to switch parent. A key future of the proposed framework is that it is primarily implemented at the Sink and so requires few changes to existing routing protocols. The framework was implemented in TinyOS on TelosB motes and its performance was assessed in a testbed network and in TOSSIM simulation. The algorithm increased the lifetime of the network by 41 % as recorded in the testbed experiment. The Packet Delivery Ratio was also improved from 85.97 to 99.47 %. Finally a comparative study was performed using the proposed framework with various existing routing protocols.

HMC-MAC Protocol for High Data Rate Wireless Sensor Networks

Using multiple channels in wireless sensor networks helps increase the overall throughput and avoid interferences. In addition, introducing multi-interface nodes further helps in increasing the packet delivery rate for those specific nodes. In this paper, we evaluate a channel allocation method based on neighborhood discovery up to 3 hops and a hybrid MAC protocol designed for high data rate wireless sensor networks. We propose a network segmentation that takes into consideration the existence of multi-interface sink in order to further increase to packet delivery ratio. Our protocol, called HMC-MAC, uses Time Devision Multiple Access (TDMA) for sequencing nodes activity, and Carrier Sense Multiple Access (CSMA)/CA with Frequency Devision Multiple Access (FDMA) for simultaneous data exchange. We evaluated our method using NS2 simulator and results show that HMC-MAC protocol improves the overall network performance compared to other protocols especially with high data rate and burst traffic.

A 2.4 GHz Hybrid Polyphase Filter Based BFSK Receiver With High Frequency Offset Tolerance for Wireless Sensor Networks

A low power 2.4 GHz hybrid polyphase filter (PPF) based BFSK receiver with high frequency offset tolerance (FOT) at small modulation indexes (MIs) is presented for medium data rate wireless sensor network applications. A high FOT at low MI is achieved by a frequency-to-energy conversion architecture using PPFs without any frequency correction circuits. Channel selection and interference rejection are performed simultaneously by the PPFs without any extra hardware and power consumption. Furthermore, the proposed hybrid topology of the PPFs provides an improved adjacent channel rejection (ACR) at reduced power. The prototype receiver fabricated in a 0.13-µm CMOS process, including the RF and analog front-ends, consumes 1.97 mW from a 1 V supply. With a data rate of 1 Mb/s, a sensitivity of –84 dBm, a FOT of ${\pm} $ 450 kHz ( ${\pm} $ 180 ppm), and an ACR of 40 dB are achieved for a MI of 2.

Low Overhead MAC Protocol for Low Data Rate Wireless Sensor Networks

We propose the low overhead media access control protocol (LO-MAC), a new low latency, energy efficient MAC protocol for low data rate wireless sensor networks. LO-MAC uses both duty cycling and multihop forwarding from the routing-enhanced MAC protocol (RMAC) to reduce idle listening and sleep latency, respectively. Besides that, LO-MAC introduces a traffic-adaptive mechanism, which is based on the fact that a node can sense a busy channel within its carrier sensing range. This mechanism uses carrier sensing as a binary signal, and effectively notifies nodes of the existence of a data packet. The nodes then either keep their radios on to take part in multihop data forwarding or turn them off to save energy. Moreover, LO-MAC takes full advantage of the broadcast nature of wireless communication and lets a packet have different meanings when it is in transmission range of different nodes. In LO-MAC, not only is a request-to-send/clear-to-send pair replaced with a Pioneer (PION) packet, as in RMAC, but also a data packet can play both data and acknowledgement functions. Therefore, control overhead and overhearing energy are significantly reduced. Our simulation results show that LO-MAC outperforms RMAC in terms of energy efficiency while achieving comparable end-to-end latency.

Proposed Technique for Transport Protocol in Wireless Sensor Network (WSN) for Multimedia Application

Recently, reliable data transport in wireless sensor network becomes very crucial for real-time application with different application requirements. Real time multimedia application requires large bandwidth and big memory in the network in order to send video data and needs to arrive at destination in time. Data that arrives at the receiver not in time will be discarded and cannot be played because loss recovery through retransmission of data loss may introduce long delays. Therefore, an implementation of transport protocol in wireless sensor network for multimedia application is a challenging task. Traditional protocol likes TCP and UDP cannot directly applied for real-time communication over wireless sensor network because the lack of functions of real-time services and the unique characteristics of sensor node itself. However there is another transport protocol which is the Stream Control Transmission Protocol (SCTP) that provides multi-stream service for single connection. This feature can be applied for video transmission according to the type of frame to be transmitted. Thus, to achieve the high reliability video data delivery, the advantages of multi-streaming features in SCTP with the combination of low data rate wireless sensor networks will be applied for the new proposed transport protocol. Besides that, transport protocol algorithm also allows maximum network lifetime due to the limited operating lifetime of sensor node and multimedia also is a highly power consuming task. Thus, to prolong the lifetime of wireless sensor network, an efficient transport protocol need to support reliable message delivery and provide congestion control in the most energy efficient. This paper focuses on the existing transport protocols for real-time application and the future protocol that provides the entire requirement of transport protocol.

Improving the ultra-low-power performance of IEEE 802.15.6 by adaptive synchronisation

In ultra-low data rate wireless sensor networks (WSNs) waking up just to listen to a beacon every superframe can be a major waste of energy. This study introduces MedMAC, a medium access protocol for ultra-low data rate WSNs that achieves significant energy efficiency through a novel synchronisation mechanism. The new draft IEEE 802.15.6 standard for body area networks includes a sub-class of applications such as medical implantable devices and long-term micro miniature sensors with ultra-low power requirements. It will be desirable for these devices to have 10 years or more of operation between battery changes, or to have average current requirements matched to energy harvesting technology. Simulation results are presented to show that the MedMAC allows nodes to maintain synchronisation to the network while sleeping through many beacons with a significant increase in energy efficiency during periods of particularly low data transfer. Results from a comparative analysis of MedMAC and IEEE 802.15.6 MAC show that MedMAC has superior efficiency with energy savings of between 25 and 87% for the presented scenarios.

A stochastic model for beaconless IEEE 802.15.4 MAC operation

IEEE 802.15.4 is a popular choice for MAC/PHY protocols in low power and low data rate wireless sensor networks. In this paper, we develop a stochastic model for the beaconless operation of IEEE 802.15.4 MAC protocol. Given the number of nodes competing for channel access and their packet generation rates, the model predicts the packet loss probability and the packet latency. The model can also account for the impact of hidden nodes in certain situations. We compared the model predictions with NS2 simulation results and found an excellent match between the two for a wide range of the packet generation rates and the number of competing nodes in the network.