Page 309 - From Smart Grid to Internet of Energy

Internet of things for smart grid applications Chapter 7 275

The data transmission rates at PHY layer for each frequency channel are 20,
40, and 250 Kbps, respectively. MAC layer of beacon-enabled mode uses
Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA) access
protocol. The lately improved IEEE 802.15.4e has brought two operation modes
as Time Slotted Channel Hopping (TSCH) and Deterministic and Synchronous
Multi-Channel Extension (DSME) for automation processes. Both of these
operation modes enable the protocol to mitigate the fading problems and
increase the reliability, security, and integrity [32, 43].
IEEE 802.11: It is a set of MAC and PHY layer designation to implement
Wireless Local Area Network (WLAN) communication operating at several
frequency bands as 900 MHz, 2.4 GHz, 3.6 GHz, 5 GHz, and 60 GHz. WLAN
technologies play important role in IoT infrastructure. Wi-Fi is a featured tech-
nology that is implemented for WLAN devices based on IEEE 802.11. The leg-
acy IEEE 802.11a/b/g/n WLAN technologies increased the channel bandwidth
of 20/40 MHz to 80/160 MHz in IEEE 802.11ac standard that reaches up to
1 km transmission range in the outdoor. Orthogonal frequency-division multi-
plexing (OFDM) which is 10 times slower has also been adopted by PHY to the
IEEE 802.11ac to extend the range. On the other hand, headers in MAC layer
have been decreased and the energy efficiency has been increased by this
improvement.
A specified version of IEEE 802.11b is known as IEEE 802.11 power save
mode (PSM) that is designed to operate in power-saving mode to increase
energy efficiency by idle and sleep mode support for devices. The IEEE
802.11b determines the data bandwidth at 11 Mbps, which is built by 8 bps seg-
mented Complementary Code Keying (CCK) infrastructure. While the IEEE
802.11a/b/g/n/ac versions have a generic usage for smart and IT devices,
recently improved IEEE 802.11af/ah/ac protocols are used to extend transmis-
sion range and for specialized applications of WSNs, AMI devices, IoT appli-
cations, and M2M communication purposes. Although IEEE 802.11ac is older
than IEEE 802.11af/ah protocols, there a PSM mode optimization enabled it to
be used PHY layer sub-GHz IoT applications. IEEE 802.11af/ah provides
higher energy efficiency in sub-GHz applications. IEEE 802.11af uses many
of the recent operational enhancement techniques adopted by the most recent
IEEE 802.11 standards, such as multiple-input multiple-output (MIMO),
OFDM, and channel bonding. By the improvement of IEEE 802.11af-2013
standard in 2014, the protocol has been adopted to cognitive radio (CR) appli-
cations in addition to legacy analog or digital television usages. The frequency
of IEEE 802.11af ranges from 54 to 790 MHz where the maximum bandwidth is
35.6 Mbps for 8-MHz channels where 16 channels can be spared.
IEEE 802.11ah which is in sub-GHz band as IEEE 802.11af operates at
900 MHz band. It provides different channels at lower bandwidths as 1, 2, 4,
and 8 MHz. Hence, IEEE 802.11ah provides longer range, better transmission
sensitivity, and lower energy consumption than other WLAN standards. More-
over, IEEE 802.11ah utilizes Distributed Coordination Function (DCF) as in
IEEE 802.11 PSM [44, 45].