Jim Morrison

An energy analysis of IEEE 802.15.6 scheduled access modes

Body Area Networks (BANs) are an emerging area of wireless personal communications. The IEEE 802.15.6 working group aims to develop a communications standard optimised for low power devices operating on, in or around the human body. IEEE 802.15.6 specifically targets low power medical application areas. The IEEE 802.15.6 draft defines two main channel access modes; contention based and contention free. This paper examines the energy lifetime performance of contention free access and in particular of periodic scheduled allocations. This paper presents an overview of the IEEE 802.15.6 and an analytical model for estimating the device lifetime. The analysis determines the maximum device lifetime for a range of scheduled allocations. It also shows that the higher the data rate of frame transfers the longer the device lifetime. Finally, the energy savings provided by block transfers are quantified and compared to immediately acknowledged alternatives.

Microstrip-Fed Pattern- and Polarization- Reconfigurable Compact Truncated Monopole Antenna

A microstrip-fed truncated monopole antenna with radiation pattern and polarization reconfigurability is presented. The antenna fabricated on a substrate of dielectric constant 4.4 and thickness 1.6 mm is highly compact with an overall dimension of only 0.25λs × 0.25λs. The pattern of the antenna is omnidirectional and is reconfigurable with the polarization in the orthogonal planes. The proposed antenna is suitable for 2.4-GHz wireless applications with a bandwidth of 95 MHz. The measured gain of the antenna is -1.1 dBi at the resonant frequency. The simulation (Ansoft HFSS) and measurement (R&S ZVB8 Vector Network Analyzer) results are also discussed.

An energy analysis of IEEE 802.15.6 scheduled access modes for medical applications

Body Area Networks (BANs) are an emerging area of wireless personal communications. The IEEE 802.15.6 working group aims to develop a communications standard optimised for low power devices operating on, in or around the human body. IEEE 802.15.6 specifically targets low power medical application areas. The IEEE 802.15.6 draft defines two main channel access modes; contention based and contention free. This paper examines the energy lifetime performance of contention free access and in particular of periodic scheduled allocations. This paper presents an overview of the IEEE 802.15.6 and an analytical model for estimating the device lifetime. The analysis determines the maximum device lifetime for a range of scheduled allocations. It also shows that the higher the data rate of frame transfers the longer the device lifetime. Finally, the energy savings provided by block transfers are quantified and compared to immediately acknowledged alternatives.

The effect of body shape and gender on wireless Body Area Network on-body channels

Technological advancements have made possible the emergence of Body Area Networks (BANs). There are numerous on-body channel characterizations in the literature performed on a phantom or a single human subject. In this paper, using multiple subjects, we consider the effect of body shape and gender on the on-body channel. A characterization of a narrowband on-body to on-body channel among different subjects is presented. The paper investigates the relationship between the propagation and the subjects physical characteristics. The investigation is performed at 2360 MHz; the new medical band undergoing FCC approval. Our results show that the path loss in women is less than that in men and the level of fade is usually higher in men than women. They also show that involuntary movements along with respiration cause small-scale fading that follows the Rice distribution.

Energy-Balanced Rate Assignment and Routing Protocol for Body Area Networks

In Body Area Networks (BANs), quality of service is needed to provide reliable data communication over prioritized data streams coming from energy constrained sensors attached to, or possibly implanted in, patients. In this work, we focus on BAN for real-time data streaming applications, where the real-time nature of data streams is of critical importance for providing a useful and efficient sensorial feedback for the user while system lifetime should be maximized. Thus, bandwidth, throughput and energy efficiency of the communication protocol must be carefully optimized. In this paper, we present an Energy-Balanced Rate Assignment and Routing Protocol (EBRAR). EBRAR selects routes based on the residual energy, thus, instead of continuously routing data through an optimized (energy efficient) fixed path, the data is transported more intelligently and the burden of forwarding the data is more equally spread among the nodes. Another unique property of EBRAR is its ability to provide adaptive resource allocation. Our experimental results show that the proposed protocol performs well in terms of balancing energy consumption across the BAN and thus guarantees longer network lifetime.

On-body to on-body channel characterization

Interest in on-body communication channels is growing as the use of wireless devices increases in medical, consumer and military sensor applications. This paper presents an experimental investigation and analysis of the narrowband on-body propagation channel. This analysis considers each of the factors affecting the channel during a range of stationary and motion activities in different environments with actual wireless mote devices on the body. Use of such motes allows greater freedom in the subjects movements and the inclusion of real-world indoor and outdoor environments in a test sequence. This paper identifies and analyses the effect of the different components of the signal propagation (mean propagation path gain, large-scale fading and small-scale fading) and the cause of the losses and variation due to activities, positions or environmental factors. Our results show the effect on the received signal and the impact of voluntary and involuntary movements, which cause shadowing effects. The analysis also allows us to identify sensor positions on the body that are more reliable and those positions that may require a relay or those that may be suitable for acting as a relay.

Current characterisation for ultra low power wireless body area networks

The emerging area of body area networks (BAN) imposes challenging requirements on hardware and software to achieve the desired lifetimes for certain devices such as long term medical implants. In this paper, we propose a novel approach to the measurement and characterisation of the energy consumption of BAN devices. The approach uses a low cost energy auditing circuit and addresses the problem of accurately measuring low-level current consumption. This new technique will allow precise and analytical measurements of systems and components in terms of energy. This will help circuit designers minimise power consumption in BAN devices. Software engineers might use this approach to validate and optimise embedded code. Network engineers can optimise network parameters to reduce the power consumption of a single node. Adoption of the proposed technique will aid the development of ultra-low power wireless BANs. Results are presented on current characterisation for two wireless motes.

Analysis of the Effect of Human Presence on a Wireless Sensor Network

Wireless Sensor Networks (WSNs) are gaining an increasing industry wide adoption. However, there remain major challenges such as network dimensioning and node placement especially in Built Environment Networks (BENs). Decisions on the node placement, orientation, and the number of nodes to cover the area of interest are usually ad-hoc. Ray tracing tools are traditionally employed to predict RF signal propagation; however, such tools are primarily intended for outdoor environments. RF signal propagation varies greatly indoors due to building materials and infrastructure, obstacles, node placement, antenna orientation and human presence. Because of the complexity of signal prediction, these factors are usually ignored or given little weight when such networks are analyzed. The papers results show the effects of the building size and layout, building materials, human presence and mobility on the signal propagation of a BEN. Additionally, they show that antenna radiation pattern is a key factor in the RF propagation performance, and appropriate device orientation and placement can improve the network reliability. Further, the RSS facility in RF transceivers can be exploited to detect the presence and motion of humans in the environment.

A schema for the selection of network topology for Wireless Body Area Networks

A topology governs the logical connectivity between the nodes in the network. Development of Wireless Body Area Networks (WBANs) requires applying tailored technologies to countermeasure the effects of wireless propagation while satisfying constrains imposed by hardware. Important part of this process is topology selection as it affects the development of the entire network protocol stack. For example, use of a star or point-to-point topology removes the need for using routing as required by other topologies such as mesh. Therefore in this paper we propose a novel method of topology selection for BANs that we refer to as a topology selection schema. The schema identifies and discusses a broad range of parameters that should be considered in topology selection and then proposes a topology selection schema. The schema determines the values of those parameters by comparing them against a given set of assumptions on the use of the network, e.g. use case scenario, environmental conditions, device and traffic related parameters. Then it reduces them into a set of concise parameters, which can be easily used to assess the suitability of given topologies.

Intelligent routing strategies in wireless sensor networks for smart cities applications

In the context of Smart City environments, wireless sensor networking is playing a major role when enabling the utilization of networked infrastructures to introduce or improve a wide variety of services to be available to the citizens. How nodes communicate with each other is a key issue in these types of networks. This work presents a simple but yet efficient network discovery and tree construction protocol as well as an intelligent metric for route selection in smart environments that combines several parameters through the use of fuzzy logic. We have carried out an extensive set of experiments using the I3ASensorBed testbed, that shows the efficiency of our proposal, when compared to other well known routing metrics by reducing the system load and increasing the network efficiency.