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192 From smart grid to internet of energy

FIG. 5.8 MAC frame structure of IEEE 802.11 standard.

IEEE 802.11a works on 5 GHz frequency by employing OFDM method
with 52 subcarriers. Theoretically, the maximum data rate of this standard is
54 Mbps.
IEEE 802.11b works on 2.4 GHz frequency of the ISM band by using DSSS
method. Data rate of this standard can reach up to 1 Mbps for outdoor environ-
ments while reachable data rate is around 11 Mbps for indoor environments.
While the range for indoor is approximately 30–40 m, the range for outdoor
is nearly 90–100 m [39–41].
IEEE 802.11g works on 2.4 GHz frequency of the ISM band by using either
the DSSS or the OFDM method, and the standard is able to provide 54 Mbps
data rates. In addition, this standard is compatible with devices based on the
IEEE 802.11b standard [39–41].
IEEE 802.11n works on both 2.4 and 5 GHz frequency of the ISM band by
using OFDM method. In addition, this standard can reach 600 Mbps data rates
by supporting Multiple Input-Multiple Output (MIMO) scheme.
IEEE 802.11ad operates in millimeter wave band (60 GHz) since it intends
to support ultra-high-throughput short-range communication. Its reachable data
rate is around 6.76 Gbps.
IEEE 802.11af that re-characterizes PHY and MAC layers is also referred
as White-Fi or Super Wi-Fi, and it was approved in 2014. The main aim of this
standard is to enable WLAN in TV white spectrum (TVWS) between 54 and
790 MHz. This band was originally allocated for analog TV signals but it is
not currently employed for transmission of analog TV signals due to digital
transmission of TV signals.
IEEE 802.11ah that is an amendment of IEEE 802.11-2007 standard is pub-
lished in 2017, and it is also called as Wi-Fi HaLow. This recent standard
employs 900 MHz unlicensed bands in order to extend range of Wi-Fi networks
when compared with traditional Wi-Fi networks functioning in the ISM bands
with 2.4 and 5 GHz frequencies. The main advantages presented by the standard
are its lower power consumption and longer coverage features. These features
of the standard make it convenient for M2M, IoT and SG applications.
The PHY layer of this standard exploits OFDM method with 64 subcarriers
and beamforming is supported for both multi user MIMO and single user
systems. The developments on power saving mode are mainly realized in the
MAC layer. Therefore, devices may be operated through batteries. The standard