There is a bit of confusion in the marketplace over spectrum utilization. Regarding WMTS (Wireless Medical Telemetry Service) it seems to be fading into the horizon for a whole host of reasons to include cost, expansion, and risk management.
802.11 has proven itself out in the marketplace for medical devices and pretty much everything else in not only healthcare but all the other vertical markets. Now it seems there are competitive debates in patient monitoring as well. Should we use 802.11a because it is at 5.0GHz and 802.11g is at 2.4GHz and the spectrum area of 2.4GHz is crowded with device use? Well it really just is not only about this, i.e. spectrum…but the actual design, site design, and deployment of a mission critical wireless medical device enterprise network. All of this is an evolving and changing environment that is dictated by www.ieee.org and international standards that are moving ahead monthly.
Some clarification here is due….and also what is really going to happen to the 802.11 space in the months ahead.
Channel Availability
Since the 2.4GHz band has only three non-overlapping channels (1, 6, 11) and 83.5MHz in the entire band, it clearly cannot support the two highest bandwidth modes in 802.11ac. The 5 GHz band however has 24 non-overlapping 20Mhz wide channels in North America (19 outside of NA). However due to possible interference with radar… Dynamic Frequency Selection is used which reduces the number of channels from 24 to 9.
Wireless Site Design
A site design for 5.0GHz has to be totally different than for 2.4GHz propagation of the signal is not the same….and a re-design will have to occur for 802.11ac. The vast majority of healthcare WLAN networks were site designed for 802.11b/g, not for the frequency propagation of 5.0GHz.
802.11ac High Level Description
802.11ac is the fifth generation of WiFi standards building on the IEEE 802.11n in 5.0GHz spectrum.
It’s purpose is to improve data rates into the Gigabit speeds, increase RF bandwidth utilization efficiency, and support denser AP deployments. To make things interesting for those looking forward to the expected bandwidth benefits of 802.11ac, the standard is being released in two waves.
Wave 1 – Single User – Multiple Input Multiple Output (SU-MIMO): An AP will have the ability to use multiple antennas to send data to a single client. The benefit is more bandwidth than what was available in 802.11n; the downside is that Wave 1 hardware is not software upgradeable to Wave 2. Wave 1 is what we have available today in consumer products and some enterprise gear.
Wave 2 – Multi User – Multiple Input Multiple Output (MU-MIMO): An AP will now have the ability to use multiple antennas to send data to a multiple clients. This will be the closest Wi-Fi has ever gotten to replicating a wired Ethernets full duplex capabilities. In order to maximize the investment our opinion is that healthcare organizations should really hold off on 802.11ac until the Wave 2 infrastructure is available. This brings us to client devices, their support of 802.11ac and performance. When 802.11n first came to market, it took a number of years before supporting clients began to overtake legacy devices. It has taken even longer for tablets; and now smartphones to support 5GHz 802.11a/n. So the theoretical maximum performance gains of 802.11n took longer to realize than many had at first expected. What’s more, consumers soon learned that the bandwidth capabilities of 802.11n were limited to how many antennas a client radio contained multiple input multiple output or MIMO. The smaller the device the fewer the antennas is also a good rule of thumb.
As 802.11ac client devices begin to permeate the market, healthcare organizations that have an 802.11 a/b/g/n network should be able to begin to fully leverage the 5GHz spectrum. This trend alone should result in improved performance in the congested 2.4 GHz space while giving the IT organization time to design for the pending 802.11ac Wave 2 infrastructure and more importantly address how best to maximize the impact of this new technology within the healthcare environment.
Patient Monitoring Requirements….”The Bandwidth.”
Even though patient monitoring is life critical…the amount of bandwidth requirement is relatively low. The data packet size per monitor is around 512 bytes to 1480 bytes with the average network traffic generated per device of 45 kbits/second.
2.4GHz and Roaming for WLAN enabled Patient Monitoring
Scanning and using only three non-overlapping channels actually improves roaming.
2.4GHz versus 5.0GHz.
As seen from the aforementioned; the adoption of 802.11ac at the end of 2013 and into 2014 will have to use the 5.0GHz spectrum. High bandwidth applications such as streaming video and the support of GB (wireless Ethernet), will become a reality. 5.0GHz will become what we see as the “crowded” area because of high bandwidth application requirements, shifting off load from 2.4GHz. Patient monitoring because of its low bandwidth requirements will perform very well in 2.4GHz. The majority of healthcare networks and site design has been optimized for 2.4GHz, not 5.0GHz. The adoption of 802.11ac and to be soon realized the intended capabilities will require the total re-design of current WLAN infrastructures to support 5.0GHz and the requirements of 802.11ac, (back haul, etc. fiber infrastructure versus wired GigaEthernet). International IEEE standards will continue to support all standards for interoperability from 802.11a/b/g/n/ac.
