41
communication network while the Zigbee Router ZR transfers information between the gadgets
2.2.5 Cellular Networks
Mobile phone system is usually identified as cellular networks since the coverage region is made out of radio cells whereby
every single one is served by a Base Transceiver Station BTS. The BTS functions as directed by the service operator and as
supported by the cellular technology. Coverage area can be up- graded by creating additional cells. The use of cellular compo-
sition extends the capacity and lowers the usage of power during transmission besides enhancing the coverage area. One
of the key features of cellular networking is the ability of the users to move across cells without breaking connections which
is achieved by handover algorithms.
There are arrays of diverse technologies which are currently be- ing used around the globe. We shall discuss briefly the technol-
ogies that are in use today, while omitting outdated frameworks for example Time Division Multiple Access TDMA and Ad-
vanced Mobile Phone System AMPS cellular technologies. CDMA1900 1.9 Ghz represents Code Division Multiple Ac-
cess 1.9 Ghz. At the moment, USA still make use of an old digi- tal cellular communication system as there are only a few
operators who are authorized to operate at 800 Mhz before the FCC approval for 1.9 Ghz. CDMA can support multiple concur-
rent base stations which are on the same frequency channel.
2.5 G 900 Mhz: GSM Phase 2 + Global System for Mobile communication which is verified by the European Telecom-
munications Standards Institute ETSI is a system generally used all over the world as it offers easy roaming across the na-
tions with one single cellular phone. General Packet Radio Ser- vice GPRS is an extension of 2.5 G which supports an
42
extensive variety of multimedia services at a slow speed up to 114 Kbps. The type of services is legislated by an Access Point
Name APN which de fine services for example Wireless Ap-
plication Protocol WAP access, Multimedia Messaging Ser- vice MMS, Short Message Service SMS, Point-to-focus
PTP and Internet access.
3 G 1.8 Ghz: Third Generation technology that is an im- provement on the earlier 2.5 G version and has a maximum
speed of 14.4 Mbps. The main characteristics of 3G are mobile TV broad casting and video calling. There are diverse interface
networking systems that are accepted by the ITU International Telecommunications Union IMT-2000 as 3 G networks. The
prominent ones are Mobile WiMAX and UMTS Universal Mobile Telecommunications System that is otherwise called
W-CDMA where W signifies Wideband. The Mobile WiMAX is named under Worldwide Interoperability for Microwave Ac-
cess and is developed from the IEEE 802.16 Broadband Wire- less Access BWA standard. UMTS is a substantially more
developed and generally used technology and is an immediate upgrading of 2.5 G that basically developed from previous ac-
cessible mobile technologies. An enhanced adaptation generally denoted as 3.5 G was introduced in 2006 as High Speed Down-
link Packet Access HSDPA which can support over 20 Mbps. In the year 2012, this is expected to be upgraded to 4 G with
100 Mbps and upgraded security features. In between the 2.5 G and 3 G version there is a technology frequently known as 2.75
G. Although, this version is not regularly used but most people are familiar with CDMA2000 and EDGE Enhanced Data rates
for GSM Evolution. These are developed from CDMA1900 and GSM Phase 2+. However, these versions are often wrongly
categories as 3 G because their expanded information capaci- ties supports 2.5 G systems.
Kategori