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?
Nearly two-thirds of the wireless LAN infrastructure systems in businesses, including hospitals, use products from Cisco Systems, Inc. As a result, most hospitals want assurance that their medical devices and other mobile devices will run well with a Cisco wireless LAN infrastructure. In addition, hospitals may want those devices to exploit Cisco Wi-Fi innovations if the result will be stronger security, application reliability when devices are moving, and other benefits that may not be available with every Wi-Fi device.
While every Wi-Fi CERTIFIED medical device should interoperate with a Cisco Wi-Fi infrastructure, the Cisco Compatible seal gives hospitals an extra measure of confidence about a device's Cisco "compatibility". A client device earns the Cisco Compatible seal through a program called Cisco Compatible Extensions, or CCX. Like the Wi-Fi certification program, CCX:
- Includes a specification that defines a set of features that must be implemented in the hardware and software for a Wi-Fi radio or a device that uses a Wi-Fi radio
- Requires compliance testing conducted by an independent lab that is approved by the organization that manages the program
- Requires that a submitted radio or device pass all tests to be approved
The CCX specification is a superset of that used for Wi-Fi certification. Cisco has published five versions of its CCX specification, with each version building on the last. Today, a product can be certified only at one of the two most recent versions: V4 or V5. Each version includes a specification for laptops and another for what Cisco calls application-specific devices, or ASDs. The specification for ASDs is a subset of the specification for laptops and would apply to medical devices.
What Are the Key Features of CCX?
Many CCX features are IEEE or industry standards, such as these:
- Wi-Fi certification for the device or the radio in the device
- Wi-Fi Protected Access (WPA) and WPA2
- Wi-Fi Multimedia (WMM): A standard for quality of service (QoS)
- Call Admission Control (CAC): The ability to reserve and control bandwidth for voice, improving the quality of voice calls
- Unscheduled Automatic Power Save Delivery (U-APSD), also called reverse polling: Allows synchronization of send/receive in one atomic operation to improve battery life, increase capacity per AP, and reduce congestion
Some CCX features are Cisco-proprietary. Here are Cisco innovations that are required for CCX V4 for ASDs:
- LEAP, a Cisco-defined EAP type used with WPA and WPA2 – EAP-FAST or EAP-TLS can be supported instead of LEAP
- AP-assisted roaming
- Fast 802.1X re-authentication via the Cisco Centralized Key Management (CCKM) protocol, which is an alternative to an optional element of the IEEE 802.11i standard
- AP-specified client transmit power
- Client-based RF scanning and reporting to provide information to a Cisco management platform
- Voice metrics, which provide information to predict and tune networks for optimum voice over wireless LAN performance
Why Are So Few Medical Devices Certified for CCX?
CCX has been an overwhelming success in the laptop world, where a few silicon providers – such as Intel, Atheros, and Broadcom – do all of the work in their reference designs for radios. The medical device market is a challenging one for silicon providers, however, and no silicon provider offers a CCX-ready radio reference design for medical devices. To ensure that a wireless LAN radio supports CCX features, a medical device vendor must enhance the software for that radio. Modifying wireless LAN radio software is a daunting task for most medical device vendors.
When a medical device runs Windows CE or Windows Mobile, the medical device vendor has another option: use a Wi-Fi radio that already is certified for CCX. Two companies offer radios that are certified for CCX on Windows CE and Windows Mobile:
- Socket Mobile, with its P700 802.11b/g radio module
- Summit Data Communications, which offers several 802.11b/g radio modules and cards and, soon, 802.11a/b/g radio modules and cards
For more information on CCX and medical devices, visit the Summit Web site and look for a white paper entitled "The Value of CCX for Medical Devices". The paper will be posted in mid-March.