Analyzing link budget for a medical body area network#
You are working as an engineer in a large regional hospital. Some physicians expressed their interest in getting a new telemedicine system to monitor patients over a week or so. The device will be worn on a body and will both monitor, e.g., blood pressure and act on the body, e.g., electrical muscle stimulation. The system supports the incorporation of many sensors worn on many patients, which should have enough bandwidth for reliable operation, and you want to analyze whether the system is feasible in your work environment.
- medical body area network (MBAN)
a wireless network of medical wearable computing devices
The system creates an MBAN.
Technical details:
Based on Medical Device Radiocommunications Service and uses 2360-2400 MHz band.
data rate: 125 kb/s, bandwidth is limited to 2 MHz
similar to Bluetooth 6.0 Low Energy PHY spec (Excerpt: 125 kb/s ±1 ppm for the LE Coded PHY when using S=8 coding, The LE system uses 40 RF channels with center frequencies at a 2 MHz spacing from 2402 MHz to 2480 MHz.)
the sensors are configured to send a packet every 100 ms.
packet size: 32 bytes
contains complete physiological data
maximum \(P_\mathrm{tx} \approx 1 \mathrm{mW} = -30 \mathrm{dBW}\)
similar to sensors based on Bluetooth 6.0 Low Energy power class 3 (Excerpt: 1 mW (0 dBm) ≥ Pmax ≥ 0.01 mW (-20 dBm))
sensor has a patch antenna \(G_\mathrm{tx}\) about 2 dB
a central receiver antenna has \(G_\mathrm{rx}\) about 3 dB
placed in the middle of the hospital floor
the hospital floor spans an area of 100m x 30m
has many rooms
Questions about requirements:
Does the system have enough link budget for a reliable reception at the central receiver?
First assume an LOS transmission in a hospital room.
Then analyze the actual case
Is the data rate sufficient?
The device can house two rechargeable AA batteries. Is this sufficient to power one device for over a week?
If any requirement is not sufficient: do you have any suggestions for improvement?