.NET Micro Framework: Good Choice for Medical Devices?
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.
Medical Devices: To CE, or not to CE?
In my last blog post, I explained that:
- Mobile medical devices must establish and maintain secure Wi-Fi connections in environments that present challenges to wireless connectivity
- Most of the Wi-Fi functionality of a mobile medical device is supplied by the Wi-Fi radio device driver
- Reference drivers from Wi-Fi silicon providers are designed for mainstream devices such as laptops, not for medical devices
- Customizing a Wi-Fi device driver for a medical device requires the skills of an experienced Wi-Fi driver developer who has source code for the driver
- Obtaining driver source code can be difficult, and experienced Wi-Fi driver developers are in short supply
The primary options for a medical device maker are:
- Find a Wi-Fi client radio with a driver that works (well enough) on the medical device
- Hire an employee or contractor, or work with a contract development shop, to customize a driver for the device
The decision on which option to pursue often depends on the operating system that runs on the device.
Wi-Fi Device Drivers for Medical Devices
When you buy a Wi-Fi infrastructure device such as an access point or router, you do not pay extra for the software; it is included with the purchase price of the product. The same is true when a device maker buys a Wi-Fi radio module or card that is embedded or used in the device. Even though there is no extra charge for Wi-Fi software, that software provides most of a Wi-Fi product’s functionality in areas such as connectivity, roaming, security, quality of service, and management. Software also enables a Wi-Fi vendor to differentiate its offering by implementing features that address specific market and device requirements better than competitive products do.
Reference Driver: Not Enough
The core software component of a Wi-Fi product is the device driver for the Wi-Fi radio that operates in the device. That driver provides the interface between the device’s operating system and the radio. Intel, Atheros, Broadcom, Marvell, and other silicon providers may be known for making Wi-Fi chips out of silicon, but they employ teams of software engineers that develop device drivers for APs, routers, laptops, and other devices that use the radios with those chips inside.
While drivers from silicon providers (often called reference drivers) are sufficient for mainstream client devices such as laptops, they are not designed for mobile medical devices. For starters, a driver may not run on a medical device because the driver was written for a different operating system than the one that runs on the device. Even when it runs on a mobile medical device, a driver may not address the requirements of that device, especially requirements for reliable connectivity when the device is in motion.
Do Medical Devices Need 802.11n?
Because it promises throughput as much as 10 times greater than that available with current Wi-Fi® standards, the forthcoming IEEE 802.11n standard is generating tremendous interest among users of wireless LAN (WLAN) products. 802.11n throughput rivals that of Ethernet, and so availability of 802.11n may cause some organizations to use WLANs as the primary means of network access for typical computer users.
Although the 802.11n standard will not be finalized and ratified until 2009, it is easy to find laptops, home routers, and other products with radios that are based on a draft of the standard. The Wi-Fi Alliance, an industry association, is performing product interoperability testing and certification based on the draft standard. Should makers of medical devices be racing to add 802.11n to their devices?
Cisco CCX and Medical Devices
When it connects to a wireless LAN, a medical device uses the Wi-Fi® radio to send data to and from network infrastructure such as access points. If the medical device’s Wi-Fi connection is unreliable, then the device’s operation will become unreliable, and users will be reluctant to use the device. In some hospitals, network-ready medical devices sit unused in closets because users could not rely on the devices to maintain consistent network connections, especially when the devices were mobile.
Wi-Fi radios adhere to a set of IEEE and industry standards that define how the radio interoperates with a wireless LAN infrastructure. Devices that bear the Wi-Fi CERTIFIED™ seal have passed a set of interoperability tests defined by an industry association called the Wi-Fi Alliance®. A medical device that is Wi-Fi CERTIFIED should interoperate with any wireless LAN infrastructure, but there are no guarantees that operation will be flawless or that connections will be reliable. That’s because Wi-Fi interoperability testing uses access points (APs) from only a few vendors and doesn’t include such things as roaming from one AP to another.
What Is CCX?
