Biomedical Engineering Reference
In-Depth Information
Fig. 2.1 The IEEE 802.15.6
standard physical layer
protocol data unit (PPDU) for
IR-UWB PHY specifications
SHR
PHR
PSDU
MAC
header
Parity
bits
Default
mode
MAC frame body
FCS
High QoS
mode
MAC
header
MAC frame body
FCS
SHR: Synchronization Header
PHR: Physical Header
PSDU: Physical layer Service Data Unit
FCS: Frame Check Sequence
QoS: Quality of Service
length, pulse type (chirp pulse, chaotic pulse and short pulse) and modulation
mode. The IEEE 802.15.6 standard supports also bit interleaving using a modulus
interleaver in order to provide robust data transmission by avoiding large
sequences of consecutive ones and zeros. Because of the difficulty in CCA for
UWB, a random access mechanism based on the slotted ALOHA or a polling
based medium access mechanism is recommended for UWB based WBANS in the
IEEE 802.15.6 standard.
Drawbacks: although the IEEE 802.15.6 standard defines a robust standard for
WBAN applications, it has several drawbacks when it comes to using UWB for
WBAN applications. It ignores several key limitations in the implementation of
the UWB transceivers. The MAC protocol defined by the IEEE 802.15.6 standard
utilises a UWB receiver at the sensor node end. Although the UWB transmitters
are relatively less complex, the implementation of the UWB receiver requires
power hungry complex circuit design. In addition, the MAC protocol defined in the
standard ignores the optimisation of the UWB transmit power control through duty
cycling and gated pulse transmission techniques [
5
,
6
], which can be used to
optimise the power consumption of the transmitter node while controlling the
transmit power of the sensor nodes according to the FCC regulations for UWB
transmission [
7
].
2.3 The IEEE 802.15.4a Standard
The IEEE 802.15.4a standard [
8
] is currently the most discussed and adopted
standard for UWB applications in the literature. The IEEE 802.15.4a standard has
been the inspiration for many UWB based MAC implementations found in the
literature.
The main application of IEEE 802.15.4a is for low data rate UWB applications
and ranging applications.
Similar
to the IEEE
802.15.6 standard, the IEEE
