Body area networks: a way to improve remote patient monitoring.
Body Area Network Technology
Previously, patient monitoring typically consisted of various sensors connected to the body as well as a processing unit through unwieldy wires. With a multitude of wires, the patient activity and level of comfort (not to mention the measured results) are negatively impacted. The advancement of wireless technology enables an increase in BAN efficiency Figure 1 illustrates a typical wireless BAN. A network of sensors is placed close to the human body or implanted in some tissues to allow the collection of specific physiological data. This allows the medical specialist to continuously monitor physiological data of a patient's health, regardless of the geographical location.
The sensed signal can monitor several types of medical measurements such as electroencephalography (EEG), electrocardiography (ECG), electromyography (EMG), skin temperature, skin conductance, or electro oculography (EOG). Each of these sensors transmits the collected information wirelessly to an external processing unit, which instantly transmits all information in real time to the doctor's facility, or to a specific server. The sensors used in the BAN require accurate sensing, a certain level of signal processing, as well as some wireless features. These sensors can be transceivers or receivers only, which is a defining factor for this network's characteristics. Sensors used in BAN are classified by two main categories:
* A wearable BAN is located within the vicinity of the body. It consists of inexpensive, lightweight, and miniature sensors that allow long term ambulatory health monitoring, thus providing a periodic update of the patient's health status. Wearable BANs are mostly used for physiological monitoring.
* An implantable BAN is located within the tissues of the human body. Implantable BANs use biosensors and, unlike wearable BANS, are used for more than just monitoring. Implantable BANs represent a highly desirable proposition for health issues like diabetes management, which currently relies on data obtained by pricking the patient's finger. In addition to being a painful procedure, this method is incapable of reflecting the overall direction, trends, and patterns associated with the patient's daily habits. Implantable BANs are widely used in applications such as drug delivery through a micro-pump or micro-port, insulin, etc.
BAN Node Requirements
The challenges of designing BANs can be summarized as follow:
* Form factor: Size and weight are very pivotal for BAN sensors, as they directly impact the patient's level of comfort. The smaller and less visible a node is, the less likely it will introduce restrictions in the patient's activities. Considering the population types being targeted by BANs, user friendliness is a very important factor for BAN technology adoption.
* Current consumption: Current consumption represents a critical challenge when designing BAN nodes. The need to replace or recharge batteries is undesirable for wearable nodes, and is totally unacceptable for any implantable nodes.
* Reliability: When dealing with medical applications, it is imperative that a system provide great data accuracy and reliability in order not to endanger the patient. Therefore, accuracy and reliability are both addressed at the sensing and wireless transmission level.
* Security: To protect a patient's privacy and prevent hacking into the network, BAN nodes also need to be secured.
* Intelligence: The level of signal processing capability is determined by how much intelligence the node can display. Nodes are becoming more and more intelligent with the use of advanced processor and high integration.
Body Area Networks Nodes Standards
A BAN can be implemented using several existing wireless standards such as Bluetooth, ZigBee, Wi-Fi, ANT, or BLE. These existing standards, however, have not been optimized for BAN applications. They carry significant overhead, as they were designed with other applications in mind. Therefore, they generally don't meet the peak-power consumption requirements.
BAN systems also can be implemented using proprietary solutions from different vendors. However, different systems use different operating frequencies and may not be interoperable. While lacking interoperability, proprietary solutions do allow solutions tailored to one's needs.
To develop a communications standard that is optimized for low-power devices suitable for BAN applications and operations, IEEE has launched the IEEE 802.15 Task Group 6 (BAN), known as the IEEE 802.15.5 standard.
Texas Instruments, www.ti.com
To view the expanded version of article, visit http://www.ecnmag.com/Articles/2011/10/App-Solutions/Body-Area-Networks/
Media Access Control (MAC) and Security Narrowband Ultra-Wideband Human-Body PHY (UWB) PHY Communications (HBHC) PHY