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Sunday, October 30, 2011

Cognitive Radio and Healthcare: Automating Healthcare with ubiquitous connectivity


Cognition is the scientific term for the process involved in knowing, which includes perception and judgement. Such process intelligently detects surrounding environment and makes decision based on what is learnt. Recent advancements in sensor technologies coupled with miniaturization and its huge potential to function without much human intervention makes the deployment of an automated health care monitoring system feasible. Body sensors (wearable, implantable, or portable) are fast emerging and are envisioned to be a promising approach to monitor the physiological conditions and disease progression. This enables monitoring physiologies without affecting users’ normal day-to-day life. Many such body sensors have recently been proposed and are already in the verge of commercial use. Wearable devices that measure the vital signs of patients have drawn much research attention.  


The end of the analog TV broadcasting opens a broad spectrum bands in the 400 MHz and 700 MHz range for wireless transmission for the public safety operations and other commercial services. A wide range of applications will be trialed and competing for this band. The excellent propagation characteristics of this band through buildings and other obstructions makes it an ideal band for Multimedia Home Networks.

It can be considered a good medium for at-home medical information collection and transmission. The transmission of medical information such as vital signs can be performed using any or a combination of the existing wireless technologies, e.g., cellular,WiFi, Zigbee, Bluetooth. Each of these technologies provides different advantages in terms of coverage (e.g., cellular) or bandwidth (e.g., WiFi). With the advent of heterogeneous wireless access networks, wireless service providers (WSPs) can combine the complementary advantages of different wireless access networks operating on both licensed and unlicensed bands to serve an increasing amount of automated health monitoring demands. This, however, poses a unique challenge of switching between different wireless networks to provide ubiquitous connectivity.

 Also, devices that are close to each other and transmitting using the same frequency band may cause interference to each other. This may result in faulty data or service interruption. It is thus essential to design a system that can switch between different access networks and different frequency bands effectively in an intelligent manner. Cognitive radio (CR) based on dynamic spectrum access (DSA) has the capability of dynamically accessing different frequency bands depending on the environment and location and thus is anticipated to enable dynamic switching between different wireless networks. How can the CR know when to switch frequency band and what frequency band to use? In a hospital or senior health care center, many medical devices are present and may be functioning at a certain frequency band. These devices may be physically placed in a room or moved around. The CR need to know the location of itself and the location of neighboring devices and their frequency bands.

When a CR senses the location of a device that is transmitting in a frequency band that may cause interference between them, it will switch its frequency band to avoid interference with that device. Here, location information can be used to predict and model interference among the functional medical devices and assist CR to make appropriate decision on frequency band selection upon sensing possible interference. This requires the CR to have location sensing capability of both itself and the other devices. Since the monitoring devices are usually attached to patients who may not show much mobility, the environment is rather static in a sense that the radio environment may not change much. Therefore, spectrum and interference measurement can be used to model spectrum availability and resource allocation.

An important criteria for the CR nodes to decide when to switch access networks or frequency channels is the location of the transmitting devices. In an automated health care monitoring system, it is crucial to provide accurate location information of either health care receivers or medical devices. This not only ensures timely response to emergent situations by providing accurate location but also avoids interference among the functioning medical devices by smartly sensing and switching transmission channels.

Paramedics require real-time accurate patient location information to provide immediate medical attention. E-911 service requires location information provided by service provider. Providing location information of mobile medical devices ensures the choice of the proper transmission frequency to avoid interference with other devices.

Also, devices that are close to each other and transmitting using the same frequency band may cause interference to each other. This may result in faulty data or service interruption. It is thus essential to design a system that can switch between different access networks and different frequency bands effectively in an intelligent manner. Cognitive radio (CR) based on dynamic spectrum access (DSA) has the capability of dynamically accessing different frequency bands depending on the environment and location and thus is anticipated to enable dynamic switching between different wireless networks.


How can the CR know when to switch frequency band and what frequency band to use? In a hospital or senior health care center, many medical devices are present and may be functioning at a certain frequency band. These devices may be physically placed in a room or moved around. The CR need to know the location of itself and the location of neighboring devices and their frequency bands. When a CR senses the location of a device that is transmitting in a frequency band that may cause interference between them, it will switch its frequency band to avoid interference with that device. Here, location information can be used to predict and model interference among the functional medical devices and assist CR to make appropriate decision on frequency band selection upon sensing possible interference. This requires the CR to have location sensing capability of both itself and the other devices. Since the monitoring devices are usually attached to patients who may not show much mobility, the environment is rather static in a sense that the radio environment may not change much. Therefore, spectrum and interference measurement can be used to model spectrum availability and resource allocation.


Global positioning system (GPS) provides outdoor location information; however, a major challenge in outdoor/wide area network (WAN) environments lies in that the existing wireless network protocols often do not support GPS. Moreover, for indoor locations, the situation is even worse as it is hard for the commercially deployed GPS to provide accurate location information  due to Non-Line-of- Sight (NLoS). In recent times, there have also been few research works focusing on IP geolocation using commercial databases. However, the record in the database is often not updated on time, therefore, makes it unreliable when the IP address of the network devices changes constantly.

Why is location information important to the system in an indoor environment? In a hospital or health care center, various medical devices are present which are sensitive to interference. To provide an untethered connection among different mobile health monitoring devices and to the medical data center, the devices need to be able to flexibly use a limited available wireless spectrum. It is mandatory that the devices do not cause interference to each other as well as to other high-priority equipments like MRI or surgical machines. Note that two devices cause interference to each other when they are present within a certain physical proximity and operate using the same frequency bands. The knowledge of the location of such devices helps prevent this interference while making mobile devices smart enough to avoid the interference. Intelligent mechanisms are therefore necessary to avoid interference and provide high throughput at the same time.

When transmitting large amounts of medical data over wireless channels using small CR devices, power consumption is of great concern. It is also crucial to adopt lossless compression methods to reduce storage space. Therefore, it is important to adopt an efficient data compression and channel coding scheme to losslessly compress the transmitted data on the monitoring devices.

In a CR health care automation network, users could have tiny body sensors attached to them as shown in the illustration below. 

The body sensors collect necessary vital signs information in a periodic or on-demand manner and transmit them to a nearby CR node, which can be connected to a bed in a hospital or home environment or even be worn to enable mobility. The CR node transfers the information to any base station or access point (the choice of which depends on several factors like location, wireless channel characteristics, wireless resource availability). The base stations/access points update the information at a health record database through a smart monitoring engine. The smart monitoring engine is capable of performing complex computations if necessary.




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