## 4 Wireless Body Area Networks (WBANs)
### Implantable Wireless Body Area Network (IWBAN)  
To measure heath parameters, biosensors must be in close contact with the skin, and sometimes even inside the human body. Implantable biosensors are an important class of biosensors based on their ability to continuously measure metabolite levels, without the need for patient intervention and regardless of the patient's physiological state (sleep, rest, _etc._) [64]. For example, implantable biosensors represent a highly desirable proposition for diabetes management which currently relies on data obtained by using test strips blood from finger picking, a procedure which is not only painful, but also is incapable of reflecting the overall direction, trends, and patterns associated with daily habits [65].  
This initiated a broad research effort aimed at developing implantable biosensors for continuous monitoring of multiple biologically relevant metabolites, but not wearable sensors. Other classes of implantable devices which have been intensively investigated include sensors for nerve stimulation can ease acute pain sensors to the detecting electric signals in brain and sensors to monitor biological analysis in brain with implanted drug delivery systems for controlled delivery at the site of pain and stress [66].  
During the end of the last decade, there has been a significant increase in the number of various wearable health monitoring devices, ranging from simple pulse monitors, activity monitors, and portable Holter monitors, to sophisticated and expensive implantable sensors. The range of implantable biomedical devices will increase substantially over the next decade, thanks to improved technology in MicroSytems technology achieved during the last decade. IWBANs are more desirable than WWBAN for many advantages. WWBANs have some disadvantages: they limit the mobility of the patients; in addition, they can cause skin infections, thus contributing poor health conditions. Despite the wireless connection is not an important requirement for monitoring physiological parameters from implanted sensors. This problem is considered as one of the main motivations for the trend in modern biomedical implanted systems to use wireless technology [66].  
[PERSON] _et al_. [67] explored a vision of the near future when one single device will be able to create a WSN with a large number of nodes, which are hosted within and outside the body may be either  
Figure 6: A biopotential readout circuit linked to the biopotential electrodes to extract the electroencephalogram signals.  
predetermined or randomly, in accordance with the application. This vision can only be achieved through a broad communication standard for wireless telemetry link. Standard hardware and software architecture can support compatible devices, which are expected to significantly affect next generation of healthcare systems. Some of these devices can then be integrated into the wireless body area network, providing new opportunities for technology to monitor the health status [68].  
There are a large number of researches which deal with implantable body sensor networks such as [69, 70]. One of the prominent applications of implantable sensor networks in healthcare is that IWBAN can help blind people [19] to improve their vision. Patients with no vision or visually impaired can see at a reasonable level by using retina prosthesis chips implanted within a human eye, as shown in Figure 7.