Wireless wearable sensors have developed rapidly in recent years, primarily driven by e-health, fitness and wellness applications. The technological evolution of low power microprocessors is enabling to process data locally, saving energy and bandwidth and increasing the overall throughput of the wireless network.
MediCon developed a new general-purpose Inertial Measure Unit for the deployment of Body Sensor Networks (BSN), usable also as a technological platform for the creation of new market oriented products.
The unit exploits a dual-core architecture. A core offers processing capability, and the other one is a radio interface IEEE 802.15.4. The whole system features a protocol to maximize the throughput, reduce the packet loss and improve the robustness of wireless sensor nodes communication. Experimental results show that the developed solution offers better data throughput for configurations below 10 nodes compared to widely used commercial wireless sensor nodes.
Several Inertial Measure Unit (IMU) devices communicate the data acquired to the high-level application via the gateway (GW), a central node in a star network.
The developed solution, processing data directly in the local area, decreases the bandwidth required on the communication channel. These new nodes have the computational capacity to perform sensor-fusion algorithms locally for the sensor orientation calculation related to a fixed reference system in space. A flexible nodes number can be selected according to the application, up to 20 units. The proposed system is flexible in terms of the number of nodes and associated frequency respected other solutions.
The most popular application for BSN is mainly e-health to monitor and support patients with pathologies and for fitness/sports activities monitoring. Human motion capture is the method of recording human movement; this review concentrates on recording the global position of the body(segments) of an athlete. Video games often use motion capture to animate athletes, martial artists, and other in-game characters.
Wireless inertial unit: the dimensions are 40 mm x 30 mm, the weight is 20 g.
Monitoring of athletes for bilateral shoulder dislocation rehabilitation
Bilateral shoulder dislocation is usually caused by sports injuries, epileptic seizures, electric shocks. Recovery therapy involves monitoring movements to determine if the patient has returned to maximum mobility.
The patient is fitted with 3 sensors for shoulder monitoring, 5 if bilateral monitoring is performed (it is however possible to use up to 20 sensors, depending on the body segments and joints to be analyzed).
The performances that can be reached by the BSN developed by MediCon in these conditions of use, or with 5 units in operation, are:
• Sampling rate ranges 1 to 110Hz.
• Maximum throughput of 10.45 KB / s.
• Packet loss of less than 2% with common interference in the work area with different WiFi networks.
• Maximum sampling duration 3h (value in general suitable for most sports).
Depending on the number of units that the particular application needs, the user can configure the network to obtain the best tradeoff between sample rate, battery life, and other operating features concerning the calculations that the units can do locally.
The project was the subject of "Alto Apprendistato" PhD programme in collaboration with Alma Mater Studiorum - Università di Bologna.
The result of the research is proposed in the form of a customizable technological platform that can be adopted by MediCon Ingegneria customers for the creation of new products for the market.
Network scheduling with five nodes: the Tround is the reciprocal of the unit sampling rate.