Philips Medical Systems wanted to launch a patient telemetry system to monitor ECG readings in hospital, without wires. The key requirements were for a high capacity system working in the Wireless Medical Telemetry System (WMTS) band, with high quality ECG readings and 2 day battery-life. Previous systems had relied upon established analog radio techniques but these restricted the systems to just a few beds and a small physical location. Philips recognised that modern cellular telephony offered potential for larger systems where the patient could move and be monitored wherever they were.
We created a system design which allowed for a modular approach to make use of a mixture of industry standard and proprietary systems such that we could minimise the cost of development and maintenance of the complete system. The radio section was defined as a standalone modem which could operate at any frequency and with a range of protocols whilst seamlessly fitting into the overall system.
We adapted our pre-existing DECT telephony IP to be suitable for use with 1000 users in the wireless medical telemetry frequency band. By using an established cell-based telephony system, we were able to make use of the 100s of man-years of design effort which had gone into making low cost high-volume integrated circuits.
However a simple DECT implementation did not meet the technical requirements for capacity within the very restricted bandwidth available and so we undertook customization to produce a specially tailored version for Philips.
- Modified frequency band to make use of newly allocated spectrum
- Modified spectral mask to meet demanding traffic density and spectral emissions requirements
- Modified frame structure to increase user density
- Created an ultra-low power consumption radio subsystem through advanced power management techniques
Philips was able to launch a state-of-the-art patient monitoring system in the newly available WMTS band in the USA. We produced a subsequent system variant which was launched in non-USA territories where the frequency band allocations are different. The modular approach to the system design and the overall radio system architecture means that the system can be easily reconfigured for different markets without costly revalidation of each system element.
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