Medical Electronics
Wireless technologies for a world full of sugar
As many as one in ten people in Germany and over three million people in the UK suffer from diabetes mellitus, with the number increasing all the time. The number of diabetics is also rising dramatically in countries with growing economic prosperity such as China. While smart devices can enhance the positive care provided to sufferers by their physicians, choosing the right wireless technology is not as easy as it sounds. Bernd Hantsche, marketing director Embedded and Wireless at Rutronik Elektronische Bauelemente GmbH, tells us more
A
pp stores are full of helpful applications for diabetics, but even the best app is useless without
correct readings from blood glucose meters, insulin pumps, blood pressure monitors or bathroom scales. In this situation, a radio link is recommendable for transferring data. It definitely has more advantages over USB even if a battery is required: Patients do not need to carry around a cable or struggle with ports. Seeing as it is only natural for patients to
replace measuring instruments from time to time, proprietary radio transmission techniques – even if they are just proprietary application profiles via wireless protocols – only provide a solution with a short-term perspective. Standardised profiles on the other hand ensure compatibility between various manufacturers, a future-proof solution and greater flexibility. Currently available smartphones offer users a wide range of interfaces.
Near Field Communication (NFC) Today, NFC technology is integrated in most smartphones. It stands out, in particular, due to its user friendliness and encrypted data communication over a very small range. The latter is, however, a disadvantage for medical measuring
instruments, as it means diabetics need to place their handsets right next to scales, for instance, if they wish to transfer data.
Mobile wireless communication Instruments can use mobile wireless communication to upload measured values to the internet automatically and without a local gateway. A further interesting feature is the transfer of a safety key via text message. SMS text messaging uses a line connection without internet connectivity. Subsequent data communication can then take place through an IP network. This method is considered particularly secure as the encryption key is routed via a different network path. However, the amount of effort involved needs to be weighed up against other priorities: A contract with a wireless network operator results in running costs and the required transceiver is much more expensive than with NFC solutions. And if the end devices are exported, certification management is more complex and, depending on the mobile wireless module, very expensive. From a long-term perspective, only LTE
(Long Term Evaluation) offers the chance of ensuring this additional effort is worthwhile. Switzerland has already announced plans to shut down its second generation wireless technology (GPRS/EDGE) in a few years, and a number of Scandinavian countries will soon discontinue using third generation technologies (UMTS/HSDPA). A further obstacle is regulatory compliance certification with country- specific limits for radiation exposure in terms of frequency allocation, transmitting power, and service life, as well as provider-dependent certification. Several mobile network operators and service providers per country and a free
24 December 2016/January 2017 Components in Electronics
choice of SIM card for end customers can quickly lead to eye-watering seven-figure costs. Established manufacturers such as Telit offer relevant certificates for almost all wireless modules and service providers worldwide. With lesser-known, usually Asian manufacturers, it is wise to find out as much as possible before investing precious time developing options. Despite the higher costs, wireless communication is still the best choice with regard to mobility and independence. The new, small LTE categories 1 or M are tailor made for IoT applications where only a small amount of data needs to be transferred every few hours. Ever cheaper hardware with lower energy consumption is now widely available.
Bluetooth
At first glance, Bluetooth appears ideal for connecting measuring instruments. However, the traditional Bluetooth protocol only provides the SPP (Serial Port Profile) for communication. Since there are no specific standards for the various types of data above the SPP stack and Bluetooth requires a high level of energy to function, a – technologically independent – low-power successor has already been developed: Bluetooth Low Energy (BLE).
While Bluetooth classic splits the 2.4GHz ISM band into 79 x 1MHz channels using a random hopping pattern, BLE utilises a double channel bandwidth of 2MHz and only changes the frequency when required to do so. Even the software layers have a different design: Bluetooth classic has very few strictly-defined application profiles above the host controller interface (HCI); in contrast, BLE offers numerous specified application profiles and services above the GAP/GATT layers, thus enabling customised profiles. The bit stream can therefore be adapted and optimised to the respective application.
In practice, instrument manufacturers would need to provide a corresponding app for the most common smartphone operating systems and run a BLE service in the background. Any changes to the operating system would result in the software having to be checked and eventually corrected. But even BLE is not a satisfactory answer in the long term, as interoperability with other medical gadgets is not usually possible.
ANT
Finding a do-it-all device for producing a blood glucose meter, insulin pump, blood pressure monitor or bathroom scales appears difficult – but it is available. In contrast to BLE, the ANT protocol offers: • Reduced power consumption thanks
to leaner software and a channel bandwidth of just 1MHz without unnecessary frequency changes • Similar low hardware costs • Much lower costs for membership and
product listing
• Significantly more flexible network topology which allows a total of 64,000 wireless subscribers to be integrated into one ANT network
ANT is supported by almost every smartphone and is highly individual in terms of its use. Standardised application profiles can be found above the protocol under “ANT+”. Numerous specified data packages are available for individual measured values, particularly across the fields of healthcare and sport. ANT therefore ensures a manufacturer- independent network of medical and sports devices that can communicate collectively via a central hub as well as individually. ANT is not generally integrated in iPhones, but this is only marginally relevant when developing measuring instruments thanks to clever multi-protocol solutions. An ANT plug-in module can be retrofitted to older generation iPhones. For iPhone 4S and above, the connection is achieved using BLE. Most ANT-based developments rely on a Nordic Semiconductor nRF51422 or nRF52832, for which free combination stacks are available for parallel use of ANT and BLE.
Perfect combinations
Quite often it is the combination of various wireless interfaces that allow ideal use of different product functions. A number of these are already available as a combined package: BLE with NFC, BT with BLE, WiFi with BT, BLE and ZigBee, BLE with ANT and NFC. Thanks to 35 wireless suppliers, Rutronik has the right solution for practically every application, and the experts at the Rutronik Wireless Competence Center offer expert advice and knowledge. This level of market transparency saves both time and money during the preselection stage, and we draw on the expertise gained from a wide range of projects to ensure common and serious mistakes are avoided.
www.rutronik.com www.cieonline.co.uk
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