Benoît Latré

A Comprehensive Survey of Wireless Body Area Networks

Recent advances in microelectronics and integrated circuits, system-on-chip design, wireless communication and intelligent low-power sensors have allowed the realization of a Wireless Body Area Network (WBAN). A WBAN is a collection of low-power, miniaturized, invasive/non-invasive lightweight wireless sensor nodes that monitor the human body functions and the surrounding environment. In addition, it supports a number of innovative and interesting applications such as ubiquitous healthcare, entertainment, interactive gaming, and military applications. In this paper, the fundamental mechanisms of WBAN including architecture and topology, wireless implant communication, low-power Medium Access Control (MAC) and routing protocols are reviewed. A comprehensive study of the proposed technologies for WBAN at Physical (PHY), MAC, and Network layers is presented and many useful solutions are discussed for each layer. Finally, numerous WBAN applications are highlighted.

Characterization of On-Body Communication Channel and Energy Efficient Topology Design for Wireless Body Area Networks

Wireless body area networks (WBANs) offer many promising new applications in the area of remote health monitoring. An important element in the development of a WBAN is the characterization of the physical layer of the network, including an estimation of the delay spread and the path loss between two nodes on the body. This paper discusses the propagation channel between two half-wavelength dipoles at 2.45 GHz, placed near a human body and presents an application for cross-layer design in order to optimize the energy consumption of different topologies. Propagation measurements are performed on real humans in a multipath environment, considering different parts of the body separately. In addition, path loss has been numerically investigated with an anatomically correct model of the human body in free space using a 3-D electromagnetic solver. Path loss parameters and time-domain channel characteristics are extracted from the measurement and simulation data. A semi-empirical path loss model is presented for an antenna height above the body of 5 mm and antenna separations from 5 cm up to 40 cm. A time-domain analysis is performed and models are presented for the mean excess delay and the delay spread. As a cross-layer application, the proposed path loss models are used to evaluate the energy efficiency of single-hop and multihop network topologies.

Throughput and Delay Analysis of Unslotted IEEE 802.15.4

The IEEE 802.15.4 standard is designed as a low power and low data rate protocol offering high reliability. It defines a beaconed and unbeaconed version. In this work, we analyze the maximum throughput and minimum delay of the unbeaconed or unslotted version of the protocol. First, the most important features are described. Then the exact formula for the throughput and delay of a direct transmission between one sender and one receiver is given. This is done for the different frequency ranges and address structures used in IEEE 802.15.4. The analysis is limited to the unslotted version as this one experiences the lowest overhead. It is shown that the maximum throughput depends on the packet size. In the 2.4 GHz band, a bandwidth efficiency of 64.9% is reached when the maximum packet size is used. Further we describe the influence of the back off interval. A significant gain is found when the backs off parameters are altered. We have measured the throughput experimentally in order to compare the theoretical analysis with real-life examples.

Improving Reliability in Multi-hop Body Sensor Networks

Body sensor networks are an interesting emerging application of wireless sensor networks to improve healthcare and the quality of life. Current research has mainly focused on single-hop networks, although some works clearly show advantages of multi-hop architectures. In this paper, we model probabilistic connectivity in such multi-hop body sensor networks. Instead of using a circular coverage area, a more accurate model is defined based on the path loss along the human body. Further, we propose improvements to CICADA, a cross-layer multi-hop protocol that handles both medium access and the routing of data in BSNs. CICDA is slot-based and uses schemes to allocate these slots. Preliminary results for two reliability improvements are given: randomization of the schemes and repeating the schemes received from a parent node. We show that these improvements positively affect the throughput of the network and lead to fewer retransmissions. In both cases, the energy consumption of the nodes is hardly influenced.

Symbiotic Networks: Towards a New Level of Cooperation Between Wireless Networks

In the future, many wireless networks, serving diverse applications, will co-exist in the same environment. Today, wireless networks are mostly optimized in a rather opportunistic and/or selfish way: optimizations methods only use a local view of the network and environment, as they try to achieve the best performance within its own network. The optimizations are very often limited to a single layer and cooperation between networks is only happening through the use of gateways. In this paper, we suggest an alternative paradigm for supporting cooperation between otherwise independent networks, called ‘symbiotic networking’. This new paradigm can take many forms, such as sharing of network resources, sharing of nodes for communal routing purposes and sharing of (networking) services. Instead of optimizing network parameters within the individual networks, symbiotic networking solutions operate across network boundaries. Parameters are optimized between the networks and communal protocols are developed, leading to a more global optimization of the scarce network resources. In this paper, we describe several scenarios which can profit from symbiotic networking and illustrate a strategy for supporting networking protocols which can operate across network boundaries. Ultimately, through the disappearance of network boundaries and the introduction of cross-layer/cross-node/cross-network cooperation, symbiotic networks takes the notion of cooperation to a new level, paving the way for a true network symbiosis.

Path loss models for wireless communication channel along arm and torso: measurements and simulations

In this paper, measurements are performed on a real human using two half-wavelength dipoles, considering different parts of the human body separately. Path loss models are developed for the on- body channels along the arm and torso. The measurement results are verified with FDTD (Finite-Difference Time-Domain) simulations, using an anatomically correct configuration of the arms.

A Secure Cross-Layer Protocol for Multi-hop Wireless Body Area Networks

The development of Wireless Body Area Networks (WBANs) for wireless sensing and monitoring of a persons vital functions, is an enabler in providing better personal health care whilst enhancing the quality of life. A critical factor in the acceptance of WBANs is providing appropriate security and privacy protection of the wireless communication. This paper first describes a general health care platform and pinpoints the security challenges and requirements. Further it proposes and analyzes the CICADA-S protocol, a secure cross-layer protocol for WBANs. It is an extension of CICADA, which is a cross-layer protocol that handles both medium access and the routing of data in WBANs. The CICADA-S protocol is the first integrated solution that copes with threats that occur in this mobile medical monitoring scenario. It is shown that the integration of key management and secure, privacy preserving communication techniques within the CICADA-S protocol has low impact on the power consumption and throughput.

Maximum throughput and minimum delay in IEEE 802.15.4

This paper investigates the maximum throughput and minimum delay of the new IEEE 802.15.4-standard. This standard was designed as a highly reliable and low-power protocol working at a low data rate and offers a beaconed and unbeaconed version. We will give the exact formulae for a transmission between one sender and one receiver for the unbeaconed version as this one has the least overhead. Further, the influence of the different address schemes, i.e. no addresses or the use of long and short addresses, is investigated. It is shown that the maximum throughput is not higher than 163 kbps when no addresses are used and that the maximum throughput drops when the other address schemes are used. Finally, we will measure the throughput experimentally in order to validate our theoretical analysis.

Strategies and Challenges for Interconnecting Wireless Mesh and Wireless Sensor Networks

Wireless sensor networks and wireless mesh networks are popular research subjects. The interconnection of both network types enables next-generation applications and creates new optimization opportunities. However, current single-gateway solutions are suboptimal, as they do not allow advanced interactions between sensor networks (WSNs) and mesh networks (WMNs). Therefore, in this article, challenges and opportunities for optimizing the WSN-WMN interconnection are determined. In addition, several alternative existing and new interconnection approaches are presented and compared. Furthermore, the interconnection of WSNs and WMNs is used to study challenges and solutions for future heterogeneous network environments. Finally, it is argued that the use of convergence layers and the development of adaptive network protocols is a promising approach to enable low end devices to participate in heterogeneous network architectures.

MOFBAN: a lightweight modular framework for body area networks

The increasing use of wireless networks, the constant miniaturization of electrical devices and the growing interest for remote health monitoring has led to the development of wireless on-body networks or WBANs. The research on communication in this type of network is still at its infancy. The first communication protocols are being proposed, but a general architecture that can be used to integrate the protocols easily is still lacking. However, such an architecture could trigger the development of new protocols and ease the use of WBANs. In this paper, we present a lightweight modular framework for body area networks (MOFBAN). A modular structure is used which allows for a higher flexibility and improved energy efficiency. The paper first investigates the challenges and requirements needed for sending messages in a WBAN. Further, we discuss how this framework can be used when designing new protocols by defining the different components of the framework.