Setting Up Wi-Fi in a Medical Center: Positioning APs

In healthcare environments it is incredibly important that wireless devices never lose connectivity. Setting up a reliable Wi-Fi network in healthcare facilities can be a challenge which is why it is necessary for IT managers to follow certain steps when setting up a Wi-Fi infrastructure. In a previous blog post we discussed step 1 of the process, performing a site survey. This week we'll be focusing on step 2, positioning APs.

2.4 GHz versus 5 GHz

Most APs with the ability to broadcast at 5 GHz can also broadcast at 2.4 GHz. The difficult part of having both options from the same AP is the inherent differences between 2.4 GHz and 5 GHz. There is much more congestion on the 2.4 GHz band because of the volume of devices that use that frequency, but the cell size for the 5 GHz band is smaller than that of the 2.4 GHz band due to the inherent qualities of shorter bandwidths in high-frequency signals. However, a site survey allows for customization to negate the differences between the two.

In order to minimize congestion on the 5 GHz band, any traffic that is not life-critical or from a clinical device should be pushed to the 2.4 GHz spectrum. All life-critical devices or devices that transfer important information should be held on the 5 GHz spectrum to enable the traffic to transfer at a higher data rate and with less congestion.

Range Throughput Test

Laird's WB45NBT is a wireless bridge communications subsystem that provides enterprise-class Wi-Fi connectivity. Because it was designed to be implemented in an enterprise environment, the WB45 must be able to maintain acceptable data rates in high-stress situations.

The purpose of this test is to observe the potential range and throughput of the WB45NBT in an environment of higher RF traffic and noise than most enterprise environments.

Test Hardware

• 20 total devices: 19 to generate RF traffic and noise and one device under test (DUT)
• WB45NBT (DUT)

  • Connected to a Cisco 1262 AP
  • Channel 48
  • WPA2-AES-PSK
  • Default global settings (Roam trigger = -70 dBm, Roam delta = 5 dBm, Roam period = 10 seconds)

Test Procedure

• The AP is directly connected to the Iperf server.
• 20 devices are placed on a mobile cart approximately 70 ft (21 m) from the AP.
• All devices are associated to the same AP with a clear line-of-sight.
• 19 devices ping the AP simultaneously at one 64-byte ping every 10 ms per device.

  • 1900 pings per second
  • 118.75 kbps

• The cart is moved away from the AP in increments of 10 feet (3 m) down to a RSSI of -85 dBm.
• Throughput tests are run on the DUT and results checked via Iperf at each incremental distance.

  • Iperf –c [IP Address] –t 60

Test Results

The RSSI is approximately -85 dBm at 150 feet (46 m) away from the AP. The WB45NBT achieved an average throughput of approximately 4.7 mbps with data rates between 48-54 mbps.

Conclusion

While the majority of standard enterprise environments do not face such challenging conditions (for an extreme range, another AP would have been available), it is important that the WB45NBT performed well in this test. The results of this test demonstrate that, even with large amounts of RF traffic and noise, the WB45NBT remains connected to an AP with acceptable throughput at ranges of 150 feet (46 m).

Enterprise Solutions: Select a Controller

When creating a wireless network in a hospital where sensitive data is frequently transmitted, the IT manager must use enterprise-grade infrastructure. Aside from being more easily scalable than consumer-grade Small Office/Home Office (SOHO) APs, enterprise APs offer better security, centralized control, and a larger feature set. A SOHO AP should never, under any circumstances, be used in a hospital environment.

In searching for an infrastructure vendor, the most important qualification is Wi-Fi certification. The AP infrastructure must be controller-based and centralized for easier management of such a large amount of APs. On top of those base requirements, when dealing with life-critical medical devices, redundancy and self-healing capabilities are important. Redundancy includes back-up controllers, back-up servers, and back-up APs; and self-healing capabilities detect coverage holes and change power as necessary to fill them.

For more information, download our Setting Up Wi-Fi Infrastructure in a Medical Center white paper.

Keep an eye out for the next post in this series, Positioning APs, and don’t forget to subscribe!