Biomedical Engineering Reference
In-Depth Information
is limited to -16 dBm by the FCC regulations. The use of low transmission
frequency in MICS band results in low propagation loss within an implant com-
munication environment. The regulations require MICS transceivers to use inter-
ference mitigation techniques in order to prevent interference with other radio
services operating within the same frequency band. MICS devices use Listen-
Before-Talk (LBT) technique in order to listen to the wireless channel before
starting communication. If the channel is busy, an MICS transceiver uses Adaptive
Frequency Agile (AFA) technique in order to switch into another channel. How-
ever, use of MICS band is limited to low data rate applications and it cannot be
used for WBAN applications that require high data rates due to its bandwidth
limitations.
1.2.4 Bluetooth
Bluetooth operates in the 2.4 GHz ISM band and uses Frequency Hopping Spread
Spectrum (FHSS) in order to access the physical medium [
17
]. Bluetooth band-
width spans from 2402 to 2480 MHz over 79 channels with 1 MHz channel
bandwidth. It communicates based on piconet network topology, where each device
in a piconet has the ability to communicate with seven other devices in the same
piconet. Low energy Bluetooth technology [
18
] was introduced in 2009 with the
intention of reducing the power consumption in Bluetooth devices. Like the Zigbee
technology, Bluetooth also suffers from the interference in the 2.4 GHz band. It also
lacks the scalability in terms of data rate and number of supported devices.
1.2.5 Ultra-Wideband
History of UWB communication goes back to the Hertizian spark gap experiments
conducted in 1880. Shannon's experiments in 1948 highlighted the advantages of
spread spectrum communication systems. In 1960s UWB attracted attention within
the scientific community for radar applications. Early UWB devices consumed
large amount of power; hence UWB technology was not considered for data
communication applications. Emergence of semiconductor devices in the latter half
of the twentieth century created the possibility of low power UWB signal gener-
ation techniques. In 2002, Federal Communications Commission (FCC) created the
first report that approved UWB communication for commercial use [
19
]. Under this
report UWB is defined as signals having a fractional bandwidth (-10 dB
bandwidth) of more than 20 %, or a bandwidth of at least 500 MHz. FCC has
applied stringent power requirements on UWB transmission. It allows peak power
limit of 0 dBm and average power limit of -41.3 dBm/MHz. UWB is allowed to
operate in both 0-960 MHz and 3.1-10.6 GHz bands. In 2005 FCC updated its
