A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Open Research Areas <s> A Traffic-adaptive MAC protocol (TaMAC) for a Wireless Body Area Network (WBAN) is presented in this paper. The idle listening and overhearing problems are solved by exploiting the traffic information of the nodes. The protocol is supported by a traffic-based wakeup mechanism and a wakeup radio mechanism that are used to accommodate normal, emergency, and on-demand traffic in a reliable manner. Analytical expressions are derived to analyze and compare the performance of the TaMAC protocol with the WiseMAC, SMAC, and the beacon-enabled IEEE 802.15.4 MAC protocols. Results derived from the analytical expressions are validated by simulation results. It is shown that the TaMAC protocol outperforms all other protocols in terms of power consumption and delay. <s> BIB001 </s> A Review of Protocol Implementations and Energy Efficient Cross-Layer Design for Wireless Body Area Networks <s> Open Research Areas <s> In wireless body area network (WBAN), various data sources are generated by different type of sensors and transmitted to the master node, which may result in temporally different traffic loads. With time-varying channel caused by frequent body movement, transmitted data may also experience deep fading and packet loss. To meet the complex transmission requirements in WBAN, a traffic-aware and channel-aware MAC protocol is required. In this paper, we introduce CA-MAC, a context-aware MAC protocol using a hybrid of contention-based and TDMA-based approaches. A dynamic control mechanism is proposed to address fading channel by adaptively modifying MAC frame structure. Schedule-based and polling-based techniques are also used to manage periodic, bursty, and emergency traffic requirement. Simulation results confirm the advantage of CA-MAC on reliability over existing TDMA-based approach. <s> BIB002
Although WBAN specific research is an active area, only a limited number of commercial solutions have been made available outside the research community. The proliferation of WBAN technology in particular protocols specific to the monitoring of vital life signs is dependent on breakthroughs and advances in a number of key areas: Efficient Low Power Protocols: Protocols that deliver extremely high levels of energy efficiency are required for successful WBAN implementations. The focus on this main challenge is likely to remain a key area of ongoing research due to the limitations of energy supply and longevity requirements especially for embedded nodes. Context aware protocols that differentiate between steady state and emergency traffic provide an interesting insight but further research is needed to move this area forward form the modeling/simulation arena to real life practical applications BIB002 BIB001 . Extended Battery Lifetime: The potential of micro fuel cells and nanowire battery technology could result in significant breakthroughs for WBAN architectures. The resulting increase in density could significantly extend battery lifetimes over existing lithium based power supplies. The reduced size of these new battery technologies will result in a smaller sensor node footprint as the battery is currently a major contributor to node size. Security: It is vital that the key personal data that is communicated via WBANs is protected to ensure its integrity is maintained. However, complex communication protocols are expensive in terms of computational effort and, therefore, energy usage. Future research in this area needs to identify adequate levels of information security whilst not compromising on energy efficiency. Nanotechnology based Sensors: Recent innovations in nanotechnology show that the development of tiny fully integrated sensor devices that include densely packed batteries, bio-sensors and nano-scale RF transmitters is now a reality. The mechanisms for communicating with these devices may require new approaches requiring new protocols to facilitate communications at the nano-scale. Energy Harvesting: The limitations of battery life are a key consideration in the design of efficient WBAN protocols. Extending battery lifetime via the harvesting of available energy resources can be a valuable method in extending the operation of WBAN sensors. The human body emits heat and also vibration during movement. These sources of energy could be scavenged as part of an energy efficient protocol implementation to extend network life. User Experience and operational Issues: Much of the existing research has focused on the technical elements of sensing and efficiently communicating data within a WBAN. However, for systems to gain acceptance in the user community, designers will need to cater for the requirements of a wide range of real life scenarios that do not currently feature heavily in the available research. This will include the ability of systems to operate efficiently within extreme environments, in areas with high levels of interference, and that are able to adapt and perform in alignment with peoples lifestyles. Integration of WBAN architectures and the Internet: The integration of WBAN specific low power protocols and IPv6 is key to the seamless working of systems using these technologies. Future research will need to focus on tighter integration and interoperability between these two areas to ensure efficient communications from low power network to the Internet.