Distributed Antenna Systems Tame RF Deployment

As wireless technologies proliferate in the healthcare enterprise, many IT departments are looking for an enterprise solution that will better manage radio frequency (RF) technologies, improve performance, and lower operating costs. Distributed antenna systems (DAS) from MobileAccess and others, promise some degree of enterprise management for RF systems.

Northwestern Memorial Hospital (Chicago, Ill.) first deployed Wi-Fi in 2002 using Cisco Aironet access points. According to Chuck Colander, director of technology management, the hospital considered a distributed antenna system when they started looking at adopting new RF technologies with more challenging requirements. New applications included mobile devices for a physician’s order entry system and improved wireless coverage and reliability. In-building cellular phone coverage was problematic, and there were some areas where pagers did not work. The hospital also wanted to prepare for telemetry using WMTS and provide in-building cell phone coverage for staff, patients, and visitors. With current trends towards wireless adoption, Colander expects the proliferation of wireless devices to explode. Northwestern Memorial was in the process of designing a new women’s hospital and didn’t want to miss the opportunity of including a DAS infrastructure in the new building.

The team at Northwestern Memorial looked at five DAS vendors, narrowing the field to three finalists. They evaluated vendors with antenna domes dedicated by frequency and one that used radiating coax. “Do the homework to understand how the vendor’s solutions are different,” says Colander. “And be prepared to talk to engineers to really understand the differences between the technologies.”

The bulk of MobileAccess’ work was upfront design and engineering to determine antenna placement. They used computer-aided design tools to model expected RF performance and did a very comprehensive site survey to map actual RF performance. With these data, MobileAccess completed the design and bill of materials, laid out cable runs, and established antenna locations. Like many well-run hospitals, when they build a new building, Northwestern Memorial tests the new technology in an existing facility. For the DAS, the hospital chose to deploy a pilot system over a 20,000-square-foot ambulatory surgery center. Once this was complete, the system was expanded to four floors (at 45,000 square feet per floor) of the main inpatient facility. The actual installation was done by local contractors who were certified by MobileAccess. Once complete, MobileAccess came on site for a final certification.

With the project complete, the hospital now enjoys a level of coverage, for all their RF technologies. They have also added new wireless applications and services such as guest WLAN access. To date, T-Mobile, Cingular, and Sprint have contracted to install microcells in the hospital. The hospital provides room in the data center for the microcells and a fiber link to the head end; the carriers provide the microcell and T1 connection to their network. So far, T-Mobile is live, while the rest are still provisioning their systems.

Wireless networks at Northwestern Memorial are the responsibility of IT, who works closely with biomedical engineering. Along with implementing the DAS, IT also transformed desktop services to support all wireless technologies, including VoIP and in-building cell phone use. The IT department has also added wireless and mobile device architects.

Hospitals deploy two kinds of wireless systems, those with one central transmitter and those using multiple distributed transmitters. Pagers and cell phones fall into the first category. An 802.11a/b/g WLAN, RFID, and most contemporary WMTS-based telemetry systems use distributed transmitters. In-building coverage for individual centralized transmitters has always been problematic; that’s why newer technologies optimized for in-building use were designed with multiple transmitters. The real strength of distributed antenna systems is the ability to put central transmitters at a “head end” in the basement and distribute their signals together on one system to ensure optimum in-building coverage. When it comes to technologies that are already distributed, like Wi-Fi and RFID, it seems DAS vendors have yet to make a compelling case that they provide an “enterprise solution” that reduces costs.

The adoption of DAS has just begun in healthcare, and the experience at Northwestern Memorial Hospital appears to be a harbinger of things to come. Certainly, the use of wireless devices in hospitals will continue to grow, and the need for enterprise solutions will grow along with new wireless devices.

Connectologist Tim Gee has spent 20 years in healthcare automating workflow through the integration of medical devices and clinical information systems. You can read his health-tech blog or reach him by e-mail at tim@medicalconnectivity.com.