Mitigating Cellular Interference in Hospitals
By John Spindler | TE Connectivity
If you’ve been inside a hospital or clinic within the past several years, chances are that you’ve seen a sign warning you not to use your cellphone. Why is this and what can be done about it?
Ironically, the reason hospital policies prohibit client use of cellphones is that of all vertical markets, hospitals and clinics are some of the heaviest users of wireless technology. Many hospitals use Wi-Fi, medical telemetry bands, and cellular phones and tablets for doctors and nurses, which makes for a crowded wireless environment. The concern is that patients or visitors using cell phones will interfere with one or more of the existing wireless systems, so they ask us not to use them.
But the reason cellphone interference is a concern is that when an outdoor macro tower supplies the cellular signal, the cell phone must power up to its maximum output (1W or more) to reach that tower. A hospital is a highly dense environment with thick walls, lots of shielding in places due to X-ray equipment, lots of small rooms, and lots of medical equipment. It all adds up to making it difficult to get a signal to and from an outdoor cell tower. What this means is that the cellular device will have to power up significantly to have a hot enough signal to reach the nearest macro cell tower. The concern is that this level of radiation will interfere with other hospital wireless systems or medical equipment.
In fact, wireless hospital equipment has a standard for exposure to external wireless signals. Industry standards require that all medical equipment must operate properly when exposed to 3V/m (volts per meter) of applied E-field. Typically, medical equipment will be designed to operate properly under the higher exposure level of 10V/m. This maximum exposure level is called the immunity level. The E-field strength caused by a cellular phone transmission is a function of the phone’s transmit power and of the distance between the cell phone and the medical equipment. The transmission power of a cell phone is typically stated in Watts (W) or milli-watts (mW).
Despite the requirement for E-field exposure limits, hospitals are using more and more wireless technology all the time. Many doctors, for example, work in multiple hospitals and they use smartphones to communicate with hospitals and the outside world. So it’s important for a hospital to support cellular service for its staff while avoiding interference with medical equipment and other wireless devices.
What’s a hospital to do? Since the big issue is with mobile devices powering up and radiating radio signals, it means reducing the strength of cellphone signals. You do that by deploying a cellular coverage solution in the building. If you put a distributed antenna system in a hospital, the mobile devices are no more than 50 feet from an antenna point, and antenna points emit extremely low emissions, so they’re not a concern. If a mobile device is within 50 feet of a distributed antenna, it won’t have to power up to maximum strength to communicate with that antenna – it can typically make the connection using only 5 mW of power, less than is leaked by the microwave in the break room.
So establishing a clear cellular signal within that facility can effectively mitigate the concern about interference by mobile devices with critical medical gear, ensuring that all devices have a clean signal. And that means that hospitals with cellular coverage solutions inside can take down those “no cellphones” signs.
About the AuthorJohn Spindler was named vice president of Product Management for TE Connectivity’s wireless business in December 2007 through the company’s acquisition of LGC Wireless where he served as Vice President of Marketing. In his current role, Spindler is responsible for developing and managing an innovative wireless product portfolio for the company’s Network Solutions Business Unit.
During his more than 20 years of industry experience, Spindler has held a variety of product management positions with companies such as Nortel Networks, GTE and InteCom. In these positions, he had responsibility for the areas of networking, network management, computer telephony integration and wireless technologies.
Spindler received a Bachelors of Arts Degree from the University of California, Los Angeles (UCLA) and an MBA from the University of Southern California, Los Angeles.
For more information visit www.te.com
No comments:
Post a Comment