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Designing Wireless Networks for Clinical Communications

by on ‎12-14-2015 11:23 AM - last edited on ‎12-16-2015 08:35 AM by Chief Airhead Chief Airhead

Healthcare presents one of the most challenging wireless environments in today's networking world. The unique blend of critical network applications and expectation of high speed ubiquitous wireless access for everyone is challenge enough and then numerous devices are layered on top. Clinical communications are critical to providing a high quality of care and has become an especially challenging environment to plan for. This post is intended to offer some guidance in designing these networks.

 

The Emergence of the Smartphone as a Clinical Communications Tool

Smartphones are joining the healthcare scene at increasing rates, companies such as Voalte, Mobile Heartbeat, PatientSafe and Vocera are bringing new features and functionality to market and are transforming communications at the point of care. These devices are typically either Apple iPhones or the Motorola MC40, however plenty of other variations exist. Each of these phones have numerous differences in how they behave.  This differences vary from when they roam to how they handle packet loss, etc.

 

Access Point Transmit Power

In preparing to design for a clinical communications network a desired endpoint should be known. In almost all cases, Smartphones tend to have lower transmit power than what most admins are used to. As a result, we are designing wireless networks with transmit power of 10-12dBm rather than 14-17dBm as many legacy networks were built. This reduction in access point transmit power drives up the number of access points required to cover a facility by 25-50% depending on construction.

 

Data Rates

Disable lower data rates to reduce network overhead and functional cell size.

 

Access Point Placement

Fast roaming is critical to the performance of Voice over WiFi and for Smartphones this typically means leveraging 802.11r and 802.11k. Understanding how these protocols work and their impact on roaming is essential for success of any network being designed to support clinical communications. As a wireless engineer tasked with this design, the goal is to create small, clearly delineated cells with enough overlap to facilitate the roaming behavior of these mobile devices. If designed poorly, 802.11k can be a detriment to device roaming. Some general guidelines to follow:

 

  • Access points should be mounted in patient rooms and out of hallways whenever possible
  • Leverage interior service rooms to cover longer hallways--clean storage, food prep, case management offices, etc.
  • If you must place an AP in a hallway
    • consider planning to use short cross unit hallways rather than the long hallways wherever possible
    • consider using alcoves to your advantage to reduce the spread of the RF signal
  • Leverage known RF obstructions to help create clean roaming conditions that favor 802.11k
  • Overlap may need to be as much as 20% due to roaming algorithms in the smartphones
  • Pay attention to the location of patient bathrooms, facilities where these rooms are in the front of the patient room (near hallway) offer far more challenges than those where it is in the back of the room
  • Stagger APs between floors such that they are not vertically stacked on each other

 

Voice SSID

Configure for a single band whenever possible - you'll find that some vendors are still only comfortable with 2.4GHz. From experience this can work, but is not without issues either. As a general rule, I recommend using AppRF to view the applications using the SSID and prioritize them properly. Smartphones are always talking via multiple apps on multiple ports and this should be accounted for.

 

All Apps Are Not Created Equal

Certain mobile communications apps are simply not ready for the demands of a healthcare environment. Take the time to understand exactly how these apps are being used, on multiple occasions I've seen perceived "dropped" calls as an app issue rather than anything to do with the wireless network itself.

 

Test, Test, Test

This is still a relatively new application for Voice over WiFi and it will require effort to get it right. Extensive testing is typically needed to get these deployments 100% dialed in. Tuning from AP placements to transmit power tweaks should be expected to some degree.

Comments
oliver711

Amazing! 

Great Article!!

 

I have been looking after one of the Private healthcare providers locally and have succesfully rolled out WiFi for patients and Critical Care across the entire country in all of the providers hospitals (50+).

I would like to concur with All that is said.

 

Here is some of my experience I have picked up with the rollouts and what to keep an eye out for in the Hospital environments.

 

  • I Agree with the Roaming points mentioned above and I would like to air another word of caution for 802.11K (other than the poorly designed AP placements mentioned)
    I have found that as soon as we enabled 802.11K in the environments there would ussually be a few Lenovo devices specifically that would refuse to connect - Some of these Laptops we have found use Legacy NICs and the Hospital Provider a while ago got a whole lot of these which was still in use - they are old and no new drivers are available for them.
  • Other than the obvious areas like Xrays and Radiology environments where Radio active signals are used it must be noted that these signals greatly degrade Electronics on the board level reducing the lifespan of alot of devices, hence the restrictions in these areas and try to avoid placing APs in side these areas or close to their entrances -- signals leak.
  • Bolting on to the above a general practice is to have the areas shielded so the rooms are built with lead lined walls and reflective paints (the reflective paints used I have found to be a BIG issue) - as mentioned generally signal shoud stay out of these rooms, but there are passageways, VOIP and doctors travelling through these areas so plan according to the requirements, if you have a Xray/Radiology room obscuring the signal path consider placing more APs and having them placed more dence in the hallway to have signals going around bends and corners to ensure VOIP calls for example does not break up and jitter.
  • Another environmental factor to whatch out for is where Firewalls are installed -- not the network access firewall used in our IT environments but an actual physical Brick-and-Mortar Firewall. These walls I have found run in most hospitals and asof late (with the newer built hospitals) an AP can be on the other side of the wall (1 meter away from you) and you will have absolutely 0 signal from the AP so be ware of these.
  • Another environment is the Pharmacy - consider the rack placements in pharmcies and most importantly consdier their contents - Wifi Signal does not work well with liquids. So placing an AP in the middle of racks where they would for instance store Saline would be a bad descision.
  • Taking arm and signal strength in consideration - give your APs breathing space to fluctuate signal as required with an aproximate 20-40% signal overlap at full power taking your regulatory domain in cosideration.
  • Just a point on  placements inside the patients rooms -- I agree that it does make for best areas cosidering coverage, However I have personally found from a maintenance and management perspective staying out of patient rooms makes things easier with respects to cabling/installation and future maintennace on the AP itself if it does go wrong (Water damage, cable fault, anything physical causing the AP not to function as expected).
    Working over or inside a room with a patient can become quite troublesome and if the hospital is busy it can happen that the room is never empty -- so pick your placemnets carefully and consider your operational options.

Great points for all VoIP/UCC deployments.

 

I have had a great deal of success by moving clients to the 5GHz band and managing the RF.   The client configuration on all client play an important part in discovering the network and sometimes the roaming trigger can be changed.

 

We also need to make sure that all endpoints are participating in end to end QoS and the network applies the correct CoS.

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