Modelling and Implementation of QoS in Wireless Sensor Networks: A Multi-constrained Traffic Engineering Model

This paper revisits the problem of Quality of Service (QoS) provisioning to assess the relevance of using multipath routing to improve the reliability and packet delivery in wireless sensor networks while maintaining lower power consumption levels. Building upon a previous benchmark, we propose a traffic engineering model that relies on delay, reliability, and energy-constrained paths to achieve faster, reliable, and energy-efficient transmission of the information routed by a wireless sensor network. As a step forward into the implementation of the proposed QoS model, we describe the initial steps of its packet forwarding protocol and highlight the tradeoff between the complexity of the model and the ease of implementation. Using simulation, we demonstrate the relative efficiency of our proposed model compared to single path routing, disjoint path routing, and the previously proposed benchmarks. The results reveal that by achieving a good tradeoff between delay minimization, reliability maximization, and path set selection, our model outperforms the other models in terms of energy consumption and quality of paths used to route the information

Design of a flexible and robust gateway to collect sensor data in intermittent power environments

The development of a Wireless Sensor Network (WSN) gateway is challenging for sites where limited infrastructures lead to frequent power shortages and network unreliability. In this paper, we present a low-power, low-cost 802.15.4 and 802.11 compatible solution which uses open source software to meet local conditions. Using the SunSPOT motes on a system which is mostly platform independent, our system is based on the Fox embedded Linux board and equipped with a USB flash drive and a USB WiFi adapter. The system can be solar powered, and the results of a solar system design are presented. All the hardware components are available off-the-shelf and are easy to assemble. We conclude that our system is preferred for applications in remote areas, where a stable power supply and a reliable network infrastructure are lacking. Furthermore, it can be used to extend the range of WSNs by layering a network of long-range motes above islands of low-range motes

Personalised Handoff Decision for Seamless Roaming in Next Generation of Wireless Networks

The past three decades have experienced a phenomenal emergence of several wireless networks and technologies. This next generation of wireless networks (4G) will be integrated into one IP-backbone to offer improved services to the user. The features of 4G include: wide coverage, high data rates, seamless roaming and personalisation. This paper presents a personalised handoff decision method to offer personalisation in seamless roaming for the next generation of wireless networks. This is done by assigning profiles to different users with different preferences and using these profiles to offer personalised handoff. The integration of these two important features of 4G networks will provide the end user the ability to choose their own preferred networks while they roam freely between heterogeneous networks

Experimental Evaluation of Interference Mitigation on The 2.4 GHz ISM band Using Channel Hopping

Both research and practice have revealed that sensor devices running the 802.15.4 on their MAC layer may be competing for wireless communication on the 2.4 GHz ISM band with Wi-Fi, Bluetooth and other proprietary devices. Building upon a SunSPOT development platform, we evaluate the impact of channel hopping on interference mitigation in the 2.4 GHz ISM band and propose a channel hopping model that may be used to mitigate interference under different indoor WSN deployment scenarios. The results obtained by using a wireless sensor network where the sensor nodes are placed at different distances from an interference source and using different power levels agree with previous experimental works on interference in the 2.4GHz band and reveal that (1) channel hopping can improve the performance of WSNs when deployed in Wi-Fi collocating environments and (2) among the different parameters, the received signal strength indication (RSSI) is the most relevant for WSN performance evaluation in collocating Wi-Fi environments

Supporting drivable region detection by minimising salient pixels generated through robot sensors

The role of robots, automatically guided machines able to perform tasks on their own cannot be over emphasized. In particular, if robotic vehicles are to work effectively, the way they are required to perform their jobs and their ability to reach the desired destination where the job is to be performed are of utmost importance. This necessitates the need to facilitate proper navigational aid for robotic vehicles. Various navigational approaches have been proposed in robotics literature, but this work serves to provide an assistive pre-processing strategy for the detection of drivable region through minimisation of salient pixels in a colour feature extraction. Salient pixels are pixels occupying the non-drivable region particularly those having same grayscale value as road images. Salient pixels provide difficulties during colour feature extraction on road images captured by a robot’s camera (sensor). In our method, a stream of road images is captured, pixels are extracted based on a RGB (red, green, blue) colour space, edges of objects are detected using Sobel operator. Salient pixels are minimised using some heuristic which is based on a threshold parameter. In a series of experiments using our method, a stream of real life road images is obtained and results show that good drivable regions, which facilitate proper robotic navigation, can be detected

Framework for link reliability in inter-working multi-hop wireless networks

With the increase in deployment of multi-hop wireless networks and the desire for seamless internet access through ubiquitous connectivity, the inter-working of heterogeneous multi-hop wireless networks will become prominent in the near future. To complement the quest for ubiquitous service access, multi-mode mobile terminals are now in existence. Inter-working heterogeneous multi-hop wireless networks can provide seamless connectivity for such multi-mode nodes but introduces a number of challenges due to its dynamic network topology. One of the challenges in ensuring seamless access to service through these terminals in an inter-working environment is the selection of reliable wireless point-to-point links by the multi-hop nodes. A wireless link is said to be reliable if its radio attribute satisfies the minimum requirements for successful communication. Successful communication is specified by metrics such as signal to interference and noise ratio (SINR), probability of bit error etc. However, the multi-hop wireless networks being inter-worked may operate with different link layer protocols. Therefore, how can the reliability of a wireless link be estimated irrespective of the link level technologies implemented in the networks being inter-worked so that optimal paths can be used for multi-hopping between nodes? In this paper, a generic framework which can estimate the reliability of a link in inter-working multi-hop wireless network is presented. The framework uses the relationship between inter-node interference, SINR and the probability of bit error to determine the reliability of a wireless link between two nodes. There is a threshold for the probability of bit error on a link for the link to be termed reliable. Using parameters such as the SINR threshold, nodes’ transmission power, link distance and interfering node density, the framework can evaluate the reliability of a link in an interworking multi-hop network

Evaluation of Interference in Interworking Multi-hop Wireless Network

The consequence of simultaneous transmissions by nodes in inter-working multi-hop wireless networks is inter-node interference. Inter-node interference is a metric that is important for the performance evaluation of inter-working wireless networks. Several interference models exist in literature, however, these models are for specific wireless networks and MAC protocols. Due to the heterogeneity of link-level technologies in inter-working multi-hop wireless networks, it is desirable to have generic models for the evaluation of interference on links in such networks. A generic model can provide information about the interference level on a link irrespective of the MAC protocol in use. This paper presents a generic interference model. The model evaluates the probability of interference and uses the negative second moment of the distance between a receiver-node and interfering-nodes to evaluate the interference power on a link in an inter-working multi-hop wireless network. Numerical results of the performance of the model are presented

A Model for Interference on Links in Inter-working Multi-hop Wireless Networks

Inter-node interference is an important performance metric in interworking multi-hop wireless networks. Such interference results from simultaneous transmissions by the nodes in these networks. Although several interference models exist in literature, these models are for specific wireless networks and MAC protocols. Due to the heterogeneity of link-level technologies in interworking multi-hop wireless networks, it is desirable to have generic models to evaluate interference on links in inter-working multi-hop wireless networks. This paper presents a generic model to provide information about the interference level on a link irrespective of the MAC protocol in use. The model determines the probability of interference and uses the negative second moment of the distance between a receiver-node and interfering-nodes to estimate the interference power on a link. Numerical results of the performance of the model are presented

Long Distance Wireless Sensor Networks: simulation vs reality

Wireless sensor networks allow unprecedented abilities to observe and understand large-scale, real-world phenomena at a fine spatial-temporal resolution. Their application in Developing Countries is even more interesting: they can help solve problems that affect communities. One of the limitations of current wireless sensors is the communication range, with most devices having 100 meters as maximum limit. In contrast, many applications require long-range wireless sensor network where nodes are separated by large distances, giving the advantage of being able to monitor a vast geographic area. In this paper we will present the results of simulations and of experiments carried out using off-the-shelf equipment over distances ranging from 300m to 12km. The results show that long distance wireless sensor networks (LDWSN) are possible and that the quality of these links is high

A framework for Connectivity in Inter-working Multi-hop Wireless Networks

Establishing connectivity between node pairs in inter-working multihop wireless networks is a challenge. Although connectivity in multi-hop wireless networks has been studied yet these analyses focused mainly on ad-hoc networks. Since the next generation of wireless networks will be inter-working, an understanding of connectivity as it applies to such networks is needed. Specifically, this research emphasizes that the connectivity between any node pair in an inter-working multi-hop wireless network should be estimated with the availability of links and the level of interference on the available links that form the communication route between the nodes. Interference is a major factor that inhibits connectivity as it can cause wasteful transmissions over low quality links. Therefore this paper presents a framework for connectivity in interworking multi-hop wireless networks. In addition a connectivity aware routing technique is proposed. Simulation results of the performance of the proposed routing technique in comparison with other routing scheme are presented