2.?Methods and Material2.1. System ArchitectureThe aim of the IPANEMA BSN is to provide a wearable and flexible platform to enable mobile measurements in a wide range of medical and health-oriented application scenarios. So far, two applications have been explored: a cardiac monitoring system and a hydration status monitoring system [31,32]. The modular hardware and software concept facilitates adaptation and extension with new sensors and actuators. The design of the IPANEMA wireless sensor node generation 2 is based on the previous MEDIT BSN [31,32]. The focus of the redesign was a significant reduction in size (?33%) and weight (?69%). The use of lithium polymer battery technology instead of nickel metal hybrid batteries had a significant impact.
This allowed the use of a smaller housing and thus improved the user comfort during measurements. The main functional units are:Microcontroller (MSP430F1611, Texas Instruments Inc., Dallas, TX, USA)Power management (TPS61131, Texas Instruments Inc., Dallas, TX, USA)Wireless Transceiver (CC1101, Texas Instruments Inc., Dallas, TX, USA)Extension port (Microstac12, Erni Electronics GmbH, Adelberg, Germany)Figure 1 shows the arrangement of the functional units on the circuit board of an IPANEMA node generation 2. The components have sleep modes to increase the energy efficiency of the system and thus the run time. As mentioned before, the radio interface of the IPANEMA nodes is based on the highly flexible sub 2 GHz transceiver CC1101.
It was configured to work within the European ISM band at 433 MHz.
Furthermore, Drug_discovery the hardware is compatible to MICS band transceivers, which facilitates the integration of medical implants in future revisions. The channel spacing was set to 200 kHz with a data rate of 250 kbps with a minimum-shift-keying (MSK) modulation and 0 dBm output power. Similar BSN systems in the 433 MHz ISM band (Mica2 and BTnode) offered a significantly lower transmission rate of only 38.4 kbps and have been discontinued [26,33]. Adjacent channels were unused to accommodate the increased channel bandwidth due to the higher bit rate with respect to the channel spacing.
Batimastat All measurements were performed with a single system on a single channel. The settings were derived using the Smart RF studio software (Texas Instruments Inc.,Dallas, TX, USA). A multilayer chip antenna (AN1603-433, Rainsun Enterprise Co., Ltd., Taipei, Taiwan) was used on-board to further reduce the size of the IPANEMA node. The location and orientation of the antenna on the base node is shown in Figure 2. During preliminary test measurements, we noted a change in the transmission reliability, possibly due to a side-effect of size reduction.