Page 224 - From Smart Grid to Internet of Energy

198 From smart grid to internet of energy

firmly related to coverage, spectral efficiency, data rate and mobility [51, 52].
The 1G cellular systems, which were designed on the basis of narrowband and
analogue systems, were introduced in the early years of the 1980s. Advanced
Mobile Phone System (AMPS), Total Access Communication System (TACS)
and Nordic Mobile Telephone (NMT) were the most popular standards utilized
in the 1G cellular systems. These standards exploited frequency-division mul-
tiple access (FDMA) technique, and typically provided 2.4 Kbps data rates.
Weak spectral efficiency and security issues were the major problems of the
1G systems. Later, second generation (2G) cellular systems were launched at
the beginning of 1990s. In order to provide enhanced capacity and wider cov-
erage areas, 2G cellular systems used digital systems different from the 1G sys-
tems that were based on the analogue systems. The 2G systems not only
advanced voice communication but also enabled text message opportunity
for the users. These systems employed TDMA or CDMA method to present
higher data rates than 1G systems, as much as 64 kbps data rates. Global System
for Mobile communication (GSM), digital AMPS (D-AMPS), Personal Digital
Cellular (PDC) and CDMA One (IS-95) were the most popular standards uti-
lized in the 2G cellular systems. Even though 2G systems have provided impor-
tant developments compared to 1G systems, reachable data rates of 2G systems
were still limited that could not present sufficient speeds for the users.
Third generation (3G) mobile communication system, which was the first
international standard introduced by International Telecommunication Union
(ITU), aimed to provide significant improvements than previous generations.
The major innovation of 3G cellular systems was their data based characteris-
tics. Therefore, 3G systems could reach to two Mbps data rates by employing IP.
In addition, new services such as multimedia messaging, online TV and video
calling have been enabled for the users. Wideband CDMA (W-CDMA) technol-
ogy could support frequency division duplex (FDD) and time division duplex
(TDD) modes in 3G networks. International Mobile Telecommunications-2000
(IMT-2000), Universal Mobile Telecommunications Systems (UMTS), and
CDMA 2000 were the most popular technologies utilized in the 3G cellular sys-
tems. After these standards, High Speed Uplink/Downlink Packet Access
(HSUPA/HSDPA) and Evolution-Data Optimized (EVDO) technologies were
introduced as 3.5G cellular technologies that could provide data rates as much
as 30 Mbps [52–54]. The evolution of the cellular communication systems is
illustrated in Fig. 5.11.
The ITU has defined main requirements and several specifications of the 4G
communication systems which aim to provide 100 Mbps data rates for high-
mobility users and 1 Gbps data speeds for low-mobility users. This generation
of cellular communication systems can present wireless communications with
high-speed by exploiting 20 MHz bandwidth when compared to former gener-
ations. There exist two popular technologies for 4G systems, which are Long-
Term Evolution (LTE) and Worldwide Interoperability for Microwave Access
(WiMAX). While the LTE is introduced by 3rd Generation Partnership Project