On Aug. 6, 2015, the Federal Communications Commission (FCC) approved the use of TV White Space (TVWS) devices in the 600 MHz band. As part of the order, TVWS devices are allowed to share Channel 37 with Wireless Medical Telemetry Service (WMTS) systems that operate there. Hospitals and healthcare organizations that operate WMTS systems on Channel 37 must evaluate the risk of interference from TVWS devices and address this change in their total risk management plan.
It will be three to five years before TVWS devices are in operation, offering a crucial opportunity to prepare WMTS systems for the new spectral environment. In the past, the main threat of interference to a WMTS system in this band was either a TV broadcast signal or another WMTS system. The introduction of TVWS devices, especially mobile TVWS devices, creates a new environment for WMTS systems that use Channel 37. Many WMTS systems only use the 1.4 GHz part of that band, and those systems are not affected.
In the FCC order, TVWS devices are required to check their location with a database and are not allowed to operate closer than 380 meters to a WMTS system. The FCC believes that is enough separation to protect a WMTS system.
But is the FCC’s required buffer of 380 meters enough to protect the WMTS system at your hospital? Finding the answer is perhaps one of the first tasks for a hospital. To do so, conduct a coexistence test run, following the guidance of the standard ANSI C63.27. This process will allow you to determine the exact sensitivity of your WMTS system to the transmission of TVWS devices. ANSI C63.27 is still in draft, but the committee is currently running comparative tests and can provide guidance on using the draft to run an initial evaluation. (For a copy of the current draft, contact Stephen Berger at firstname.lastname@example.org.)
While there is still time to prepare, organizations that use WMTS operating on Channel 37 need to answer the following questions associated with risk assessment:
- What can go wrong once TVWS devices are operating?
- How often is that likely to happen?
- How bad will the consequences be?
It is important to monitor the progress of this issue at the FCC. AAMI’s Wireless Strategy Task Force (WSTF) can be a source of significant help and has started looking into the implications of the recent ruling. A lot of the spectrum issues depend on the outcome of a planned 600 MHz incentive auction, which is scheduled for March 2016, but has already been pushed back back a couple of times. When the auction does occur, the results will determine if TVWS devices will be allowed into and around Channel 37, the 600 MHz part of WMTS. Hospitals will then want to review their initial risk assessment and plans.
Stephen Berger is president of TEM Consulting. He also serves on AAMI’s Wireless Strategy Task Force and is co-chair of the AAMI Wireless Coexistence Work Group.