Providing wireless connectivity to healthcare applications
11 December 2015
Of the 26 billion connected devices forecast to become part of the Internet of Things (IoT), one of the main sectors is believed to be in healthcare.
Already popular with consumers, sports fitness and training performance monitors have led the market with many manufacturers bringing products to market.
It’s not only the consumer market that will see the major growth in the coming years. According to analyst Gartner, of the forecast $1.9 trillion value add to businesses by using IoT-enabled devices, the healthcare services sector represents 15%, the same amount as manufacturing. One of the healthcare application areas that have been quick to adopt this is that of remotely monitoring patients with chronic illnesses. Figure 1 shows the current trends of the healthcare market and how miniaturisation and integration is driving the applications from the traditional bedside appliance through to wearable and implantable health care monitors.
Being able to bring compact “connected sensing” elements such as blood pressure, blood glucose and heart rate together forms the concept of a body area network (BAN) for a personal health care system. Figure 2 illustrates the concept of a BAN where the crucial attributes of the electronics design are low power, compact overall size, integration of sensing elements and wireless connectivity.
Needless to say that many of the engineering challenges above are difficult enough for wearable applications but the additional regulatory considerations for implantable devices, where its in-service life needs to be at least 7 – 15 years, add an extra complication.
One of the benefits that miniaturisation has brought is the ability to integrate multiple sensors, low power wireless connectivity and a cell battery into a wearable “patch” that constantly monitors a patient’s vital signs. Sensor technology is also advancing to enable measurement of, for example, heart and respiration rate without the need for electronics. An example of this is Murata’s MEMS-based ballistocardiogram (BCG) sensor. By using a highly accurate accelerometer heart rate can be measured without any direct connection to the patient. This approach is already finding a host of other related healthcare applications such as sleep quality monitoring and bed occupancy, the later being very important for care homes where patient’s might wake up and walk around during the night. Wireless charging is also another technology advance that is already starting to become more common for charging cell phones but can also be usefully employed for devices such as hearing aids.
Recognising the need for interoperability between sensors, gateways and other equipment, organisations like the Continua Alliance have formed in order to establish industry standards and design guidelines.
Making it all connected is down to the provision of wireless communication. Considered a specialist engineering task, wireless design requires an in-depth knowledge of transmission methods and protocols such as Bluetooth and Wi-Fi and well as the ability to prepare a discrete design for certification with a host of international regulatory bodies. Most engineers therefore opt to use a pre-certified module within their design, saving considerable design effort, specialist engineering resource and shortening time to market.
One of the first decisions when selecting a module will be the standard to be used, the popular ones being Wi-Fi, Bluetooth and ZigBee. The designer must start by investigating how much data will need to be transferred and over what range it would typically need to be sent. For most applications there are always trade-offs between range, data rate and use case to be considered. The use case might highlight a number of criteria such as the frequency with which data needs to be transferred and the supply power budget available; a key consideration when using a battery powered device. For example, for the control of a device or receiving some sensor data only a few times a day, Bluetooth Low Energy (BLE) can be quite appealing. Virtually any smartphone can support this method of communication and, therefore, the control or data storage processing device can readily be available. However, if a higher quantity of data, say a few Mbytes needs to be transmitted then the designer might best consider using Bluetooth Classic or Wi-Fi.
For healthcare, as highlighted in Figures 2 and 3, the sensor data will typically be sent to a smartphone or home gateway for sending on to the cloud-based monitoring applications. This means that the communication distances involved would be short and, given that most devices would be powered by small low-capacity batteries, BLE becomes the ideal candidate.
An example of a suitable wireless part is the Type ZF Bluetooth SMART module from Murata. This extremely small module, measuring just 5.4 x 4.4 x 1.0 mm features an ARM Cortex-M0 processor and a transmit power of -1 dBm. With what is believed to be one of the industry’s lowest power profile the consumption is as low as 0.6 uA in sleep and up to 4.8 mA during transmit. With built-in ibeacon support, SMP, ATT and GATT profiles the Type ZF module is ideal for providing low energy Bluetooth communication to a small constrained healthcare device or sensor. Based around Dialog’s DA14580 system on chip device (SoC), the module comprises a Bluetooth qualified baseband controller core compatible with the Bluetooth SMART specification, a 2.4 GHz wireless transceiver that provides a 93 dB link budget for reliable communication in addition to the ARM Cortex-M0 microprocessor. Aimed at making software development easier, the module includes Dialog’s SmartSnippets Bluetooth Software stack. Bluetooth Smart profiles such as those of sports fitness devices, security and consumer applications are included as standard. Apart from the Bluetooth protocol stack the platform supports a hardware abstraction layer (HAL) that provides developers with easy access to the modules peripheral features.
To further speed the integration of the wireless connectivity into the healthcare application engineers should select a wireless module that not only meets their technical specification but one that also has a reference design or evaluation kit available. For example, in the case of the Type ZF module from Murata a design kit is available that would facilitate the fast prototyping of a design using the ZF module. Comprising a motherboard and a daughter board on which the wireless module is mounted, the kit offers both a comprehensive hardware and software environment on which to develop and test your design. J-Link interface, software tools and sample applications are all included in the kit. A power consumption-profiling tool is also incorporated in order to accurately measure and predict the required power budget of the end-design across numerous use cases.
The benefits of IoT connected healthcare applications are very clear. Remote monitoring of a patient’s vital signs bring security and comfort to family and enable a more efficient provision of precious healthcare professional resources. Providing reliable and resilient wireless communication is an essential component in the flow of data from patient to cloud-based monitoring applications.
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