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Emerging wireless communication for smart grid applications Chapter 5 203

FIG. 5.14 GPCS based protocol structure of WiMAX technology.

or 28 MHz channel bandwidth is utilized in IEEE 802.16 standard where LOS is
needed because of short wavelength.
The protocol structure of IEEE 802.16 standard that is illustrated in Fig. 5.14
contains PHY layer, MAC layer and a Generic Packet Convergence Sublayer
(GPCS). The PHY layer of the technology is based on OFDMA technology.
Theoretically, the technology can reach up to 70 Mbps data rates, and the range
of WiMAX is approximately 50 km in non-mobile scenarios while it is about
5 km in mobile scenarios [44]. The improved versions of the technology can
also support MIMO technology and beamforming methods. In order to ensure
secure communication, WiMAX characterizes three steps that are authentica-
tion, key establishment, and data encryption. These steps are accomplished
at the MAC layer through AES algorithm, Privacy Key Management protocol
and EAP. In addition to the security transactions, the MAC layer of the technol-
ogy can enable the use of scheduling mechanisms and sleep control mechanisms
for energy saving processes. In addition, other important characteristics of the
WiMAX are related to low latency, low operating costs, availability and scal-
ability of traffic management systems.
Although this technology works like Wi-Fi technology for last mile access,
it provides higher data rates, wider coverage and capacity than that of the Wi-Fi
systems. In addition, WiMAX can present better connection quality when
compared with Wi-Fi technology. In Wi-Fi systems, if there exist multiple users
connected to an AP, the users have to compete with each other due to used
contention-based CSMA mechanism for channel access. Therefore, each user
may have different bandwidth in the Wi-Fi systems. On the other hand,
WiMAX technology exploits a grant-request mechanism in MAC layer to allow
data exchange. This characteristic of technology provides better use of radio
resources. Furthermore, this technology can be employed to establish wide area
wireless backhaul network that can function either in P2P or mesh modes. The
backhaul-based WiMAX systems implemented in mesh mode can improve
wireless coverage and they can ensure reduced deployment cost, re-
configurability and fast deployment.