Abstract
Nowadays, wireless Body Area Networks (wBAN) have gained more relevance, in particular in the areas of health care, emergencies, ranging, location, domotics and entertainment applications. Regulations and several wireless protocols and standards have appeared in recent years. Some of them, like Bluetooth, ZigBee, Ultra Wide Band (UWB), ECMA368, WiFi, GPRS and mobile applications offer different kinds of solutions for personal area communications. In this chapter, body area network channel modelling will be described; also, a brief description of the applications and state-of-the-art of regulation and standardization processes pertaining to these kinds of networks will be presented. For each topic, the chapter shows not only the main technical characteristics, but also the technical problems and challenges in recent and future research. Finally, the chapter provides an analysis of Body Area Networks, opinions about the future and possible scenarios in the short- and medium-term for the development of standards and applications and their impacts on our daily lives.
Top2. Channel Models
One of the main challenges for new radio technologies is the modelling of the radio channel according to physical parameters like propagation media, frequency, bandwidth, etc. The main challenge is to obtain the impulse response of the channel. Body Area Networks are not an exception to this challenge, especially if we deal with in body systems. However, we will see that on body systems also present interesting challenges for channel modelling, related to the behaviour of the human body and common functions such as breathing, that affect the behaviour of radio waves.
There are two types of models: large-scale and small-scale. Large-scale models estimate the power losses due to propagation in free space, absorption and penetration into the human body. The vast majority of large-scale models are developed using statistical approaches based on measurement campaigns.
In small-scale models, we determine the channel impulse response. With this, we can determine channel distortion, frequency-selective channel fading and stability parameters. This information allows the most appropriate modulation techniques to be designed, finding the optimal transmission rates and equalization schemes in broadband. It is common to find models based on statistical approaches, but deterministic models are also a good option for modelling the channel impulse response.
In this section, we explore models of large- and small-scale technologies used in communication networks for in body and on body applications.