The cost of adding Wi-Fi connectivity to a medical device is more than the cost of the Wi-Fi radio itself. To support the radio, the device may require more memory and processing power than a base device with no Wi-Fi support. In addition, the device will need connectivity software, such as a TCP/IP software stack.
The largest cost area, however, often is overlooked. It is the cost of making the Wi-Fi radio run well on the device, where running well means providing secure, reliable connectivity even when the device is in motion in an environment that provides challenges to Wi-Fi connectivity, i.e., your typical hospital. The burden of ensuring that a Wi-Fi radio supports all required features and runs well on the device falls squarely on the shoulders of a software program called the Wi-Fi device driver.
Device drivers for a broad range of Wi-Fi radios are readily available on Microsoft operating systems and Linux. For the embedded operating systems that run on most medical devices, however, Wi-Fi device drivers are scarce. Rather than writing their own — an expensive and time-consuming process — some medical device makers are selecting Windows Embedded CE instead of an embedded OS. For resource-constrained medical devices, however, CE is too “big”. For others, it’s simply too complex and inefficient.
A more attractive alternative from Microsoft may be the .NET Micro Framework, which Microsoft calls “an innovative development and execution environment for resource-constrained devices”. The .NET Micro Framework is a bootable runtime module that requires only 300 KB of memory but provides a full managed execution environment. The module can run on top of an underlying operating system or can run natively on a device.
According to Microsoft, a typical .NET Micro Framework device has a 32-bit processor with no external memory management unit and as little as 64K of random-access memory (RAM). Examples of .NET Micro Framework devices under development are consumer medical devices, industrial automation devices, consumer electronics, and devices that operate in your car.
One goal of the .NET Micro Framework is to bring the programming paradigm of Microsoft’s .NET environment to the embedded world. Thanks to a “fully integrated Visual Studio experience”, the .NET Micro Framework enables application developers to use familiar .NET tools on desktop systems and then deploy the applications on embedded systems. With Version 3.0 of the .NET Micro Framework, which was launched at the end of October, those applications can take advantage of a richer set of facilities for secure connectivity. In the middle of 2009, connectivity options will include Wi-Fi, specifically 802.11a/b/g.