` Volume 4, Issue 2, March 2010
` © Diabetes Technology Society
`
`COMMENTARY
`
`Bluetooth Low Energy: Wireless Connectivity for Medical Monitoring
`Alf Helge Omre
`
`Abstract
`Electronic wireless sensors could cut medical costs by enabling physicians to remotely monitor vital signs such
`as blood pressure, blood glucose, and blood oxygenation while patients remain at home.
`According to the IDC report “Worldwide Bluetooth Semiconductor 2008-2012 Forecast,” published November
`2008, a forthcoming radio frequency communication (“wireless connectivity”) standard, Bluetooth low energy,
`will link wireless sensors via radio signals to the 70% of cell phones and computers likely to be fitted with the
`next generation of Bluetooth wireless technology, leveraging a ready-built infrastructure for data transmission.
`Analysis of trends indicated by this data can help physicians better manage diseases such as diabetes.
`The technology also addresses the concerns of cost, compatibility, and interoperability that have previously
`stalled widespread adoption of wireless technology in medical applications.
`J Diabetes Sci Technol 2010;4(2):457-463
`
`Introduction
`
`Health care reform is a hot topic; governments
`
`across the 30-member-nation Organization for Economic
`Co-operation and Development are looking for ways to cut
`costs without compromising patient care. The organization’s
`statistics reveal that, across a sample of 15 of its member
`nations, from a baseline of 100 in 1980, while gross
`domestic product had climbed to 205 in 2005, health care
`spending had skyrocketed to 280.1
`
`A commercial report2 concluded that the use of body-worn
`wireless electronics monitors could save the health care
`industry $25 billion by 2012. These wireless monitors that
`
`could link to existing cellular or Internet infrastructure—
`by radio communications in an unlicensed portion of
`the electromagnetic spectrum (2.4 GHz)—would allow
`patients to shorten or avoid hospital stays while still
`being in frequent electronic contact with their health
`care providers. Wireless monitoring could also replace
`expensive home visits from community nursing staff to
`take routine measurements, because medical data could
`be sent via cellular or Internet infrastructure.
`
`Moreover, savings are likely to become even greater if
`predictions come true that over 600 million people
`
`Author Affiliation: BTech–EEE, Nordic Semiconductor, Oslo, Norway
`Abbreviations: (BG) blood glucose, (CGM) continuous glucose monitoring, (EMI) electromagnetic interference, (FCC) Federal Communications
`Commission, (FDA) Food and Drug Administration, (HDP) Health Device Profile, (PC) personal computer, (SIG) special interest group,
`(SMS) short message service
`Keywords: Bluetooth low energy, diabetes, electronic sensors, low-power radio, medical monitoring, radio frequency
`Corresponding Author: Steven Keeping, B.Eng. (Hons), Nordic Semiconductor ASA, 1 Barrie Place, Davidson, NSW 2085, Australia; email address
`steven.keeping@nordicsemi.no
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`457
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`Petitioner Apple Inc. – Ex. 1024, p. 457
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`Bluetooth Low Energy: Wireless Connectivity for Medical Monitoring
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`Helge Omre
`
`worldwide will suffer from chronic diseases and that
`spending on such diseases will increase. For example, in
`the United States alone, without significant intervention,
`spending is expected to increase from the current
`$500 billion a year to $685 billion by 2020.3
`
`Until now, no wireless connectivity technology met
`all the requirements needed for widespread adoption.
`These requirements are summarized below:
`
`•
`
`Interoperability—ensuring that products from different
`manufacturers can communicate with each other;
`
`• Low-power operation—so medical monitors can run
`for months or even years on tiny coin-cell batteries,
`reducing maintenance and running costs;
`
`• Customized software optimized for medical applications
`and transmitting data in a format requested by medical
`authorities;
`
`• Compatibility—radio devices need to coexist with
`other radio transceivers and cause no electromagnetic
`interference (EMI) in other sensitive electronics devices;
`
`• Transmission of data must be secure to protect
`confidentiality; and
`
`• Sensors need to communicate with services such as the
`Internet and the cellular network so that information
`can be relayed to remote health practitioners.
`
`In this article, the author argues that Bluetooth low energy
`is the first wireless communication technology that
`meets these requirements.
`Interoperability
`The interoperability requirement discounts any of the
`commercially successful proprietary
`technologies
`from
`being adopted for wireless monitoring in health care
`applications, because there is little or no chance that
`products from different manufacturers will be able to
`communicate.
`
`There are four interoperable technologies: Wi-Fi, ZigBee,
`Bluetooth, and Bluetooth low energy. Medical equipment
`manufacturers adopting any of these wireless connectivity
`technologies must have their products approved by the
`custodians of the various standards. This approval
`guarantees that equipment from different manufacturers
`will communicate. For example, in the consumer sector,
`
`routinely expect a Bluetooth-branded wireless
`users
`headset from manufacturer A to successfully link with a
`Bluetooth-equipped cell phone from manufacturer B.
`
`Wi-Fi is a proven solution for connecting computers across
`wireless local area networks. It offers wide bandwidth
`(300 Mbps), operates in the license-free 2.4 GHz band
`(although other bands are used depending on the region),
`and has an indoor range of around 30 m.
`
`Wi-Fi’s main drawbacks are its relative expense and
`power consumption (demanding regularly recharged,
`bulky lithium-ion batteries) when used in continuous or
`frequent medical monitoring applications.
`
`ZigBee wireless technology is based on a standard
`maintained by an alliance of commercial companies called
`the ZigBee Alliance. ZigBee was designed as a low-power
`technology, and modern versions can run from coin-cell-
`type batteries (for example, CR2032, 3V cells). It operates
`in the 2.4 GHz band (although variants operate in
`other bands). Range extends up to hundreds of meters.
`
`ZigBee does have the potential for use in medical wireless
`monitoring (see section titled Wireless Technologies
`Adopted by Continua Health Alliance later); however, a
`disadvantage is that the modest bandwidth of 250 kbps
`increases the time it takes to send a set amount of data by
`up to four times compared to other low-power technologies
`such as Bluetooth low energy (see later discussion).
`Transmitting data uses battery power, demanding
`bulkier batteries or considerably shortening the life of
`small batteries. Moreover, ZigBee cannot communicate
`directly with existing cellular and Internet infrastructure.
`
`Bluetooth is based on a standard maintained by the
`Bluetooth Special Interest Group (SIG), a 14,000-member
`organization of commercial electronics companies.
`
`So-called “classic Bluetooth” technology (to differentiate
`it from Bluetooth low energy described later) also operates
`in the unlicensed 2.4 GHz band. The bandwidth (depending
`on the version) ranges from 1 to 24 Mbps. Range is up to
`30 m. Classic Bluetooth is already in use in some medical
`products, including blood glucose (BG) meters.
`
`Although classic Bluetooth can run from coin cells, its
`relatively high power consumption limits battery life to a
`few tens of hours. This makes the technology unsuitable
`for continuous medical monitoring applications. However,
`a lower power consumption form of Bluetooth technology,
`
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`Bluetooth Low Energy: Wireless Connectivity for Medical Monitoring
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`Helge Omre
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`Bluetooth low energy, overcomes this problem (see section
`An Example Application: Blood Glucose Monitoring on
`page 461).
`
`Bluetooth low energy also operates in the 2.4 GHz band.
`It features a bandwidth of 1 Mbps (four times that of
`ZigBee) with a range of 15 to 30 m.
`
`The main drawbacks of Bluetooth low energy are that it is
`an unproven technology and is unlikely to be widely
`available for medical product makers to incorporate into
`their products until the end of 2010. Medical products
`using Bluetooth low energy will probably not reach the
`market until 2011.
`
`implementations,
`low energy features two
`Bluetooth
`namely, “dual mode” and “single mode” (see Figure 1).
`Single mode devices are compact radio communication
`units suitable for incorporation into wireless medical
`monitors measuring
`just tens of millimeters
`in size.
`Power consumption is very low, allowing such medical
`monitors to run for many months or even years on
`standard coin-cell batteries. For example, in an application
`transmitting BG level measurements once every minute, on
`a continuous 24 h/365-day basis, a Bluetooth-low-energy-
`enabled wireless medical monitor powered by a CR2032
`coin cell will have a battery lifetime of at least 1.5 years.
`
`Dual mode devices are radio communication devices
`targeted at handsets and personal computers (PCs). It is
`proposed that cell phone makers will use these devices
`when they become available, because they cost only
`slightly more than the current type (classic Bluetooth)—
`
`used today in around 70 percent of handsets—but offer
`consumers much more functionality. The most important
`added functionality of a cell phone or PC equipped with
`a dual mode Bluetooth low energy device is that it will be
`able to communicate directly with single mode devices.
`Consequently, medical data can be sent from a wireless
`monitor to a cell phone or PC and from there to a remote
`physician (see Figure 2).
`Health Device Profile
`The Bluetooth SIG has developed “Health Device Profile”
`(HDP) software to optimize performance of classic Bluetooth
`for health applications and deliver data in a standard
`format requested by the medical authorities. Similarly,
`the SIG is developing HDP software for Bluetooth low
`energy.
`
`Classic Bluetooth’s HDP is a “one-size-fits-all” solution
`that caters to all types of medical products. Consequently,
`classic Bluetooth’s HDP is a large program requiring a lot
`of memory and battery power. Bluetooth low energy has
`a number of HDPs customized to a given application or
`applications. A medical product designer can select one or
`several profiles to suit their specific application, reducing
`the memory and power overheads. Consequently, a
`Bluetooth-low-energy-equipped end product will be simpler,
`cheaper, and more power efficient than would be possible
`with an equivalent classic-Bluetooth -equipped device.
`
`The first version of Bluetooth low energy will include
`HDPs for medical (and fitness) applications such as body
`temperature, blood pressure, weight scale, glucose, pulse
`
`Figure 1. Bluetooth low energy single mode devices will communicate directly with dual mode devices likely to be fitted to the next generation
`of cell phones and/or other single mode devices. RF, radio frequency; IF, intermediate frequency; MAC, media access control; BB, base band;
`ASIC, application specific integrated circuit.
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`Bluetooth Low Energy: Wireless Connectivity for Medical Monitoring
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`Helge Omre
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`oximetry, heart rate, pedometer, speed, distance, cycle
`cadence, simple remote control, and battery status.
`Electromagnetic Compatibility
`The U.S. Food and Drug Administration (FDA) and other
`medical bodies are concerned about the potential EMI
`generated by wireless connectivity devices.
`
`The FDA states, “Wireless coexistence and data latency
`remain concerns because the data transfer rate can slow
`slightly or even dramatically with an increase in the
`number of similar transmitters in a given location. In many
`cases it is essential that medical data, including real-time
`waveforms and critical control signals and alarms, be
`transmitted and received without error.” 4
`
`Worse, Bluetooth low energy radios broadcast in the
`notoriously crowded 2.4 GHz band. Licensing bodies such
`as
`the Federal Communications Commission
`(FCC)
`have attempted to mitigate the effects of EMI by restricting
`the power output of radio devices operating in the
`license-free parts of the radio spectrum to limit the
`possible EMI with sensitive electronics.5 Operating in the
`2.4 GHz band is a major challenge with consequences for
`product design.
`
`That said, Bluetooth low energy operates at 1 mW
`(0 dBm) output power—a modest output that falls well
`below the FCC’s guidelines of 125 mW (“maximum peak
`conducted output power of the intentional radiator”).
`In addition, the technology only transmits for 1% (or less)
`of the time and then only in short bursts lasting a few
`hundred microseconds. Most modern medical electronics
`have been designed with a high degree of EMI immunity
`and are very unlikely to malfunction in the presence of
`such a low power, short duration transmission.
`
`However, manufacturers would have to embark on a
`program of testing to ensure their products meet the
`electromagnetic compatibility requirements of the medical
`authorities. (Note that, because the Bluetooth SIG has
`newly adopted Bluetooth low energy, no test data are yet
`available for presentation in this article.)
`
`Perhaps more importantly, medical wireless monitors need
`a high degree of immunity from other radio sources to
`ensure communications are not interrupted. To do this,
`Bluetooth low energy employs a frequency-hopping spread
`spectrum interference avoidance scheme. When making
`an initial connection, the two transceivers transmit using
`one of three fixed channels (trying the other two in turn
`if no signal is received) in order to establish the link.
`
`Figure 2. Bluetooth low energy will extend interoperable wireless connectivity to coin-cell-powered wireless sensors in health care, fitness, and
`related sectors. WLAN, wireless local area network; GPRS, general packet radio service.
`
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`Bluetooth Low Energy: Wireless Connectivity for Medical Monitoring
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`Helge Omre
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`This is a faster and more power-efficient method of
`searching for a compatible radio source compared to
`scanning the whole band.
`
`Once communication has been established, the devices
`begin to rapidly hop between 37 dynamic data channels
`within the 2.4 GHz band hundreds of times per second
`in a synchronized pseudo-random pattern to minimize
`the likelihood of trying to communicate on the same
`frequency as another radio source. If a clash occurs,
`the Bluetooth low energy transceivers jump to another
`channel in a matter of milliseconds and “mark” the
`corrupted channel so it is not reused. Classic Bluetooth
`uses a similar scheme (albeit with 79 channels) and has
`been proven to work reliably in thousands of use cases.
`Data Security
`Medical data are highly confidential, and it is important that
`an unauthorized receiver does not intercept information
`transmitted from a wireless medical sensor.
`
`To ensure data remain confidential, Bluetooth low energy
`inherits the encryption, authentication, and authorization
`security from classic Bluetooth. The encryption technique
`uses the advanced encryption standard-128 algorithm.6
`(Advanced encryption standard is an encryption technique
`adopted as a standard by the U.S. government.)
`
`In addition to security protection, Bluetooth low energy
`also employs privacy protection in order to stop “tracking”
`by unauthorized receivers. This is done by limiting the
`ability to track a transmitting device through the use of a
`random device address that is changed frequently.
`Wireless Technologies Adopted by
`Continua Health Alliance
`In June 2009, Continua Health Alliance—an open industry
`coalition of 190 companies collaborating to improve the
`quality of personal health care—selected two wireless
`technology standards for inclusion in the next version
`of its interoperability design guidelines.7 (The design
`guidelines provide information for electronics product
`manufacturers on how to design their products to meet
`Continua’s agreed interoperability standards and receive
`the alliance’s certification logo.)
`
`levels, cell
`After consideration of required power
`phone ubiquity, required range, and anticipated market
`penetration, the alliance chose Bluetooth low energy
`(pending finalization of the specification) for medical
`
`wireless monitoring of a user’s health and fitness levels.
`Additionally, Continua chose ZigBee Health Care technology
`for low-power sensors for local area networks of devices
`such as motion detectors and bed-pressure sensors.
`An Example Application: Blood Glucose
`Monitoring
`Type 1 diabetes is caused by the patient’s inability to
`produce any insulin. The more common type 2 diabetes
`is caused by the patient’s immunity to insulin, preventing
`its uptake by the body’s cells. Rates of type 2 diabetes
`are increasing in developed countries due to an aging
`and increasingly overweight population. In the United
`States, for example, according to the Centers for Disease
`Control, approximately 23.6 million people, or 8% of
`the population, have diabetes, of which 95% suffer from
`type 2 diabetes. The total prevalence of diabetes increased
`by 13.5% from 2005 to 2007.8
`
`Uncontrolled diabetes can cause severe long-term health
`problems such as renal failure, blindness, and arterial
`disease. These problems are expensive to treat, and as
`the number of sufferers climbs, the medical authorities
`are finding it increasingly difficult to pay the bill.
`
`Good management of diabetes is one way to mitigate the
`cost of treatment, because it delays or even prevents the
`onset of related health complications. Management depends
`on frequent and accurate measurement of BG to maintain
`normal levels (a fasting range of 4 to 6 mmol/liter).
`
`A BG meter measures BG levels from a sample deposited
`on a test strip. Modern units hold information in a
`memory base for later recall at regular health checks.
`Patients are advised to record BG levels several times
`a day—more frequent measurements result in better
`control, as diet, exercise, or
`insulin
`injections can
`be adjusted quickly to stabilize high or low levels
`(see Figure 3).
`
`Bluetooth low energy built into a BG meter offers
`several advantages
`in the management of diabetes.
`Data from the BG meter could be uploaded frequently to
`the patient’s cell phone and from there to the physician’s
`computer for review. An analysis of BG measurement
`trends would allow the physician to spot persistent
`out-of-normal-range episodes much earlier than the
`typically quarterly reviews allow and to advise on
`modifications to the diet either via phone call or short
`message service (SMS; also known as “texting”) to a cell
`phone, for example, on a weekly basis.
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`Bluetooth Low Energy: Wireless Connectivity for Medical Monitoring
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`Helge Omre
`
`In addition, the computing power of the cell phone allied
`to an Internet-downloadable application could highlight
`trends and advise the patient to modify their exercise
`regime, for example, to take a 20 min walk just after
`lunch. As a complement to regular medical consultation,
`such feedback would help the patient to better manage
`the condition, and management of diabetes is the critical
`step in preventing complications and drastically cutting
`long-term health care costs.
`
`Bluetooth low energy is capable of communicating with
`a Web-based application without using either a cell
`phone or PC by using a Bluetooth router (a device that
`acts as a “gateway” between the Bluetooth low energy
`device and the Internet). The Web-based application can
`send messages back to the Bluetooth low energy device.
`This functionality would be useful if, for example, the
`diabetes patient has left their cell phone in the car.
`
`Better diabetic control can be achieved by continuous
`glucose monitoring (CGM). Continuous glucose monitoring
`relies on very frequent measurement (for example,
`288 glucose measurements every 24 h) of BG. One FDA-
`approved CGM device9 uses a tiny glucose-sensing device
`inserted under the skin of the abdomen. The system
`automatically records an average glucose value every
`5 min for up to 72 h.
`
`Continuous glucose monitoring using wireless monitoring
`has major benefits to type 1 diabetes sufferers, because
`they are more prone to short-term complications, such as
`very low BG (hypoglycemia), that can occur between
`routine periodic measurements from finger pricks, leading
`to coma if not treated rapidly. It would be relatively
`simple to set thresholds (for example, at a BG level of
`4 mmol/liter) to warn the user of danger.
`
`Wireless medical monitoring could be used in conjunction
`with CGM as an emergency communication system for
`episodes of hypoglycemia. Provided the user cancelled the
`alarm—and ate some food—the wireless monitoring system
`would take no action. But if for some reason the alarm was
`not cancelled (for example, because the diabetes patient
`has collapsed), the wireless monitor could automatically
`communicate with the diabetes patient’s cell phone to send
`a SMS to a nominated contact or even emergency services.
`Summary
`Wireless technology promises benefits for medical
`monitoring applications by
`freeing patients
`from
`inconvenient and restrictive wires. Further, wireless
`
`Figure 3. A BG meter measures BG levels from a sample deposited on
`a test strip. Modern units store information in a memory base for later
`recall at regular health checks.
`
`monitoring that can communicate with remote physicians
`via existing infrastructure could allow patients (especially
`the elderly) to remain in their homes while still under
`medical supervision. This promises to reign in escalating
`health care costs.
`
`Of all the commercially available wireless technologies,
`only Bluetooth low energy is capable of meeting all the
`requirements for medical applications, specifically, inter-
`operability, low-power operation, electronic compatibility,
`secure data transmission, and direct communication with
`cellular and Internet infrastructure.
`
`Nonetheless, significant testing will be required to
`ensure EMI between Bluetooth low energy products and
`other electronic devices causes no problems. That said,
`Bluetooth low energy is a very low-power transmission
`technology and uses sophisticated frequency-hopping
`algorithms that minimize the likelihood of interference.
`
`Wireless medical monitoring with Bluetooth low energy
`will
`initially be targeted at BG measurement, but
`applications such as body temperature, blood pressure,
`pulse oximetry, and heart rate will follow shortly after.
`However, Bluetooth low energy is a new technology,
`and medical products equipped with it are unlikely to
`appear before 2011.
`
`Funding:
`Funding was received from Nordic Semiconductor ASA, a commercial
`semiconductor vendor.
`
`J Diabetes Sci Technol Vol 4, Issue 2, March 2010
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`462
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`www.journalofdst.org
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`Petitioner Apple Inc. – Ex. 1024, p. 462
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`
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`Bluetooth Low Energy: Wireless Connectivity for Medical Monitoring
`
`Helge Omre
`
`Disclosure:
`The author is employed by Nordic Semiconductor, a manufacturer
`of one of the technologies mentioned in the article (specifically,
`Bluetooth low energy).
`
`References:
`1. Developing new drugs: reds under our meds. The Economist.
`August 27, 2009. http://www.economist.com/business-finance/displaystory.
`cfm?story_id=E1_TQPNSPPV.
`2. Hatler M, Gurganious D, Chi C. Wireless sensor networks for
`healthcare. ON World Inc. August 2008.
`3. Scaling mount proteome to bring down chronic disease. The Pfizer
`Journal. 2001;1I(2):4–9.
`4. U.S. Food and Drug Administration. Draft guidance for industry and
`FDA staff: radio-frequency wireless technology in medical devices.
`http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/
`GuidanceDocuments/ucm077210.htm#4. Accessed February 10, 2010.
`5. Title 47. Telecommunication. Chapter I: Federal Communications
`Commission. Part 15: radio frequency devices. Subpart C: intentional
`radiators. Section 15.247: operation within the bands 902–928
`MHz, 240. http://edocket.access.gpo.gov/cfr_2007/octqtr/47cfr15.247.htm.
`Accessed October 7, 2009.
`6. Wikipedia. Advanced encryption standard. http://en.wikipedia.org
`/wiki/Advanced_Encryption_Standard. Accessed October 7, 2009.
`7. Continua Health Alliance. Continua Health Alliance looks to the
`future with the selection of two new low power radio standards,
`enabling expanded use cases. Press release. June 8, 2009.
`8. Wikipedia. Diabetes mellitus type 2. http://en.wikipedia.org/wiki
`/Diabetes_mellitus_type_2. Accessed October 7, 2009.
`9. WebMD. Diabetes and continuous glucose monitoring. http://diabetes.
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`
`J Diabetes Sci Technol Vol 4, Issue 2, March 2010
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`463
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`www.journalofdst.org
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`Petitioner Apple Inc. – Ex. 1024, p. 463
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