Medical Device Connectivity
Most medical device manufacturers are implementing 802.11x
wireless connectivity. This white paper will identify requirements
and provide information to help ensure a successful wireless
implementation.
White Paper by Silex Technology America, Inc.
August 10, 2009
MEDICAL DEVICE CONNECTIVITY
Executive Summary
Medical device connectivity has many unique requirements beyond what is demanded by the typical wireless customer. This white paper will identify these requirements and provide information to help ensure a successful wireless implementation.
Silex has been providing wireless connectivity solutions for medical device manufacturers for over five years. Over this time, we have evolved our product offerings to specifically address this vertical market application.
Why Wireless?
The healthcare industry has always been an early adopter of Wi-Fi. A new study from ABI Research forecasts that revenue from sales of Wi-Fi-enabled healthcare products worldwide (not even including Wi-Fi-equipped medical equipment) will total $4.9 billion in 2014. This represents an increase of nearly 70% over today’s figure.
With $20 billion allocated in the US Stimulus Bill for the digitizing of medical records, and committees of the US Congress starting to address proposals for comprehensive reform of a medical industry that accounts for about one sixth of the US economy, attention is focused as never before on the opportunities for wireless communications in healthcare.
“It’s a pretty big business,” notes ABI Research vice president Stan Schatt in a classic understatement. “The strong uptake of Wi-Fi in the health industry is underpinned by its need for improved asset management, staff mobility, transfer of digitized records, and standardized administration of medications. In addition, government security
requirements including HIPAA often mean replacing older wireless equipment with modern versions.”
Among the benefits of increased Wi-Fi penetration are reductions in operating costs, which is also a theme stressed by the Obama administration in its drive for healthcare reform.
Medical Device Connectivity Requirements
There are three basic alternatives to add wireless to a medical device:
• External serial server (external box that connects to the medical device through
a serial interface).
• Intelligent wireless module (internal board that has SoC/memory to support
basic networking protocols and wireless module).
• Wireless radio module (utilized device SoC/memory to support basic networking
protocols).
Each of the alternatives has advantages and disadvantages which will be reviewed in a separate white paper. Regardless of the implementation, the below features are important to medical device manufacturers.
• 802.11a Support
Most medical devices today are designed to support 802.11a.
IEEE 802.11a-1999 or 802.11a is an amendment to the IEEE 802.11 specification
that added a higher throughput of up to 54 Mbit/s and uses the 5 GHz band. It has seen widespread worldwide implementation, particularly within the
corporate workspace. The amendment has been incorporated into the published IEEE 802.11-2007 standard.
Using the 5 GHz band gives 802.11a a significant advantage, since the 2.4 GHz band is heavily used to the point of being crowded. Degradation caused by such conflicts can cause frequent dropped connections and degradation of service. However, this high carrier frequency also brings a slight disadvantage: The effective overall range of 802.11a is slightly less than that of 802.11b/g; 802.11a signals cannot penetrate as far as those for 802.11b because they are absorbed more readily by walls and other solid objects in their path. On the other hand, OFDM has fundamental propagation advantages when in a high multipath environment, such as an indoor office, and the higher frequencies enable the building of smaller antennas with higher RF system gain which counteract the disadvantage of a higher band of operation. The increased number of usable channels (4 to 8 times as many in FCC countries) and the near absence of other interfering systems (microwave ovens, cordless phones, baby monitors) give 802.11a significant aggregate bandwidth and reliability advantages over 802.11b/g.
802.11n is an even newer standard that can operate in either the 2.4 or 5GHz band but higher data rates. The increase in performance is primarily driven by
consumer applications like streaming video. While medical applications typically do not need this throughput, there may be some advantages to adopting this standard for product life-cycle reasons (see below).
• Diversity Antenna Support
Antenna diversity is one of several wireless diversity schemes that use two or more antennas to improve the quality and reliability of a wireless link. Often, there is not a clear line-of-sight (LOS) between transmitter and receiver. Instead the signal is reflected along multiple paths before finally being received.
Antenna diversity is especially effective at mitigating these multipath situations. This is because multiple antennas afford a receiver several observations of the same signal. Collectively, such a system can provide a robust link and is highly recommended in a hospital environment to decrease the number of drop-outs and lost connections.
• Access Point Roaming
Radio chipsets built-in roaming is very simplistic and designed primarily for high volume laptop and cell phone manufacturers. The typical usage scenario is as follows:
• User becomes stationary with device (i.e. conference room with laptop)
• User makes a wireless connection to access point #1
• User moves to another location and again becomes stationary with device (i.e. office with laptop)
• User makes a wireless connection to access point #2
In the above example, the laptop is not being used while it is in motion. On the other hand, medical devices are often transmitting critical data such as EKG waveforms while the patient is in transit (i.e. on a gurney). The medical device manufacturer needs a solution that handles access point roaming in a seamless manner without data loss due to wireless connectivity problems.
Providing “true” mobile connectivity requires a sophisticated management scheme including the following enhancements:
• User configurable handoff threshold
• User configurable multiple SSID list
• Low Power Consumption
Portable medical devices are battery powered. As a result, low power consumption is an important consideration. But what is the specific requirement?
In general, the lower the power the better! That being said, the minimum expectation is that the device can be used for a complete 12 hour shift. The specific wireless power requirement depends on the battery and the power requirements of the medical device itself.
An intelligent module will always need more power than a wireless radio module since it adds an extra CPU and memory to support the basic networking
protocols. Low power wireless chipsets today have the following power characteristics:
• Continuous transmit <=200mA
• Continuous receive <=100mA
• Sleep <=1mA
• Long Product Life Cycle
Radio chipsets are designed for high volume consumer applications which often have a product life cycle of one year or less to take advantage of the newest technology. “Moore’s law” which states that computing power doubles every two years is the driving force for rapid product obsolescence.
On the other hand, medical device manufacturers have long design cycles as patient safety can be at stake. As a result, the typical medical device
manufacturer prefers to source technology that can be available from five to ten years.
What can the medical device manufacturer do to solve this problem?
• Radio chipset introduction date. While radio chipsets are generally discontinued based on lack of demand, you can assume that a newer chipset will be around longer than one introduced several years earlier.
• Radio chipset technology. While this is related to the chipset
introduction date, you may want to consider whether the chipset that you are considering is based on “current” technology. Two main features to consider are the processor interface and wireless standard support. For example, a Cardbus 802.11b solution is likely to have a limited
product life while a SDIO 802.11n solution should be around for some time.
• Supply chain management. In most cases, your supplier will not have control over the chipset availability. But that doesn’t mean that they can’t offer programs to extend the availability of the product. Find out what your supplier has done in the past and will do for you in the future.
• Flexible design for obsolescence. Depending on the importance of product life cycle for your organization, you may want to consider an implementation that allows for easier transition to new technology. For example, while a SIP (system in package) or SMM (surface mount
module) implemented on the device PCBA may be most cost effective, any obsolescence will result in a PCBA redesign. Alternatively, a option card solution (i.e. SDIO card form factor) or intelligent module allows you to move to a next generation wireless solution without impacting your device PCBA.
• Security
There are a number of different security standards that should be considered by medical device manufacturers. Security is an important component of any medical device connectivity solution in order to ensure compliance with HIPAA patient confidentiality requirements. Equally important is the need for
compatibility with existing hospital wireless networks. If the medical device does not support the same encryption/authentication used by a specific medical facility, the device will not be deployed.
o Wireless Security
The two key components of wireless security are encryption and authentication. Encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those
possessing special knowledge. Authentication is a process which involves communications between a supplicant, authenticator, and authentication server (generally a RADIUS database). The supplicant (i.e., client device) is not allowed access through the authenticator to the protected side of the network until the supplicant’s identity is authorized.
Encryption Protocols: • WEP
• WPA-TKIP • WPA2-CCMP
Authentication Methods: • WEP shared key
• EAP-TLS (802.1x) • EAP-TTLS (802.1x) • EAP-PEAP (802.1x) • EAP-FAST (802.1x) • Cisco LEAP
• WPA/WPA2 Pre-Shared Key (PSK) • Open System (no authentication)
o FIPS Certification
The Federal Information Processing Standard (FIPS) Publication 140-2, FIPS PUB 140-2, is a U.S. government computer security standard used to accredit cryptographic modules. The title is Security Requirements for Cryptographic Modules. Initial publication was on May 25, 2001 and was last updated December 3, 2002.
FIPS certification is a requirement for installations in US government facilities, including the VA hospital. Since there are 163 VA hospitals, FIPS certification represents a major business opportunity for medical device manufacturers.
• Interoperabiity
Cisco is the dominant supplier of Enterprise Wireless LAN solutions with a market share of around 60%. As a result, Cisco compatibility is an important consideration.
Cisco has a partner program know as Cisco Compatibility Extensions (CCX) program for WLAN client devices. The objective of the program is to ensure the widespread availability of client devices that are interoperable with a Cisco WLAN infrastructure and to take advantage of Cisco innovations for enhanced security, mobility, quality of service, and network management.
• Agency Certifications
For connectivity solutions that are external to the medical device, the IEC 60601-1 standard, Medical Electrical Equipment—Part 60601-1: General Requirements for Safety, is the cornerstone document that addresses many of the risks associated with electrical medical equipment.
What products fall under this standard? Electromedical products are defined in IEC 60601-1 Subclause 2.2.15 as “equipment, provided with not more than one
connection to a particular supply mains and intended to diagnose, treat, or monitor the patient under medical supervision and which makes physical or electrical contact with the patient and/or transfers energy to or from the patient and/or detects such energy transfer to or from the patient.” Accessories used with the such equipment can also fall under this standard.
Technical Committee (TC) 62 of the International Electrotechnical Commission (IEC) publishes the international IEC 60601-1 standard. The facilitator in the United States for IEC 60601-1 is the American National Standards Institute (ANSI;
www.ansi.org).
Wireless products (both internal and external) require a different set of
certifications. Wireless certification is a relatively complex topic. Please contact your Silex OEM Territory Manager for access to the white paper titled,
