The new wireless Dash patient monitor from GE Healthcare is the first wireless medical device that I know of that supports both 802.11e Quality of Service (QoS) and 802.11i WPA/TSK encryption. They're using a Symbol CF (compact flash) 802.11b radio, with the antenna built into the monitor's handle. GE is using Symbol's driver which GE optimized somewhat. Symbol tends to write a pretty good radio driver, with good hand-offs between access points (APs), power management, etc. Symbol is about the only reasonable choice for an off-the-shelf radio for embedded applications.
The radio supports 802.11e QoS, including EDCF (which is what VoIP phones use) and HCF. Since 802.11a/b/g uses CDMA (collision detection multiple access), the QoS schemes game the timing where devices contend for the network to minimize packet collisions and improve throughput. The radio card also supports WPA/TSK encryption. They chose not to use 802.1x authentication because the time to authenticate to a server (which theoretically could be unavailable) took too long. Instead they use a pre-shared key for authentication, which can be set over the network.
The wireless Dash monitor connects to the same GE Unity network, which requires a single broadcast domain. This limitation necessitates that wireless Dash monitors operate on their very own network VLAN. The sooner GE overcomes this legacy shortcoming, the easier it will be to support broad enterprise-wide deployments of wireless patient monitors.
One of the cool features built into the monitor is a suite of network diagnostic service screens. Via the service screens, the Dash can display data about transmitted and received packets, CRC errors, dropped packets, the current RSSI value, current channel, and the current access point (AP) the monitor's associated with. With all this diagnostic data, you could a site survey with the Dash monitor.
UPDATE: A reader notes that its not 802.11a/b/g that uses CDMA – he's right, Ethernet is based on CDMA. Wireless LANs are based on Ethernet, in fact applications can't tell whether they're running on a wired Ethernet LAN or a wireless one. Sorry for the confusion.Read More