Mobile WellBeing

Hospitals with a few hundred patient monitors and a thousand wireless infusion pumps use client radio/access point (AP) communications protocols to maximize capacity in a Wi-Fi, DECT or WMTS surrounding. Can we limitlessly build on, just connecting a new device? The ether in which wireless signals move is like gases in the atmosphere or chemicals in water. There are hardly no ways to segregate Radio frequency (RF) signals to specific areas.

The list of devices using the 2.4GHz portion of the ISM band (where Wi-Fi is located) seems endless. But because applications of the ISM band are relatively short range, it is only the specific devices using 2.4GHz within a location that have to share the spectrum. In a hospital you might have computers on wheels (COWs), wireless VoIP handsets, smart pumps, patient monitors, maybe PDAs. Each of these devices associates with just one out of hundreds of APs in a medical center.

Intentional interference is where two or more users of a portion of wireless spectrum get in each others way, disrupting or degrading the communications of one or both parties. Unintentional interference comes from electromechanical devices that accidentally spew RF signals as a consequence of some degradation or failure. Common sources of unintentional interference are florescent light balasts, blow dryers, paper shredders, elevator motors, or faulty microwaves. See some RF interference examples here.

Wireless capacity is measured by the number of transmitters and receivers that can use a given amount of bandwidth or spectrum, and the amount of data that can be reliably moved through an allocated frequency range. Capacity is determined by the amount of bandwidth and technical tricks used to increase the efficiency of moving information.

Analog is the least efficient means to move information wirelessly. Digitizing the information is a more efficient technique, moving it more quickly (higher data rates), and using schemes to share bandwidth among users more efficiently (things like FHSS, ODFM and MIMO).

Wireless applications in health care are divided into short range cable replacement and  enterprise network “last 100 feet” cable replacement. Choices for connecting to the enterprise network are limited, and include DECT, WMTS and the ISM band. Short range cable replacement applies to wireless sensors in body area networks (BANs) and are limited to ISM.

For the enterprise network using the ISM band the options are 802.15.4/ZigBee, the high powered Class I version of Bluetooth,  and components based on the old standard HomeRF. Both ZigBee and Bluetooth have specific strengths and weaknesses that must be carefully matched to effective requirements. Most wireless medical devices are deployed enterprise wide, so your Wi-Fi alternative must be cost competitive with the added burden of a duplicate enterprise-wide wireless network.

Presently, investments in improving the performance of the enterprise Wi-Fi network (whether driven by wireless medical device adoption, wireless VoIP phones, or COWs) is justified across multiple uses. A dedicated wireless medical device infrastructure — that’s not dedicated to all of a hospital’s medical devices, just one device type from one vendor — has to be cost justified based on that one medical device application.

Wireless sensors are really a short range cable replacement application. Wi-Fi is not an option here. Many of the issues discussed above are applicable to wireless sensors. Unlike wireless enterprise networking applications, wireless sensor implementations vary considerably. More on these options in an upcoming blogpost.

If you’re looking for something more, check out this.