17-02-2011, 12:13 PM
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4G Fourth-Generation Communication System
INTRODUCTION TO WIRELESS COMMUNICATION
Our ultimate goal is to communicate with any type of information with anyone, at anytime, from anywhere. This is possible with the aid of WIRELESS TECHNOLOGY
1G WIRELESS SYSTEM
Developed in 1980s and completed in early 1990’s
1G was old analog system and supported the 1st generation of analog cell phones speed up to 2.4kbps
Advance mobile phone system (AMPS) was first launched by the US and is a 1G mobile system
Allows users to make voice calls in 1 country
FDM was used in communication system
Disadvantages of 1 G
--Variations in the signal
--disrupts over long distances
2G
Digital data can be compressed and multiplexed much more effectively than analog voice encodings
--Fielded in the late 1980s and finished in the late 1990s
--Planned for voice transmission with digital signal and the speeds up to 64kbps
--TDM technique is used
Advantages of 2G–
--The digital voice encoding allows digital error checking
--increase sound quality•lowers the noise level
–Going all-digital allowed for the introduction of digital data transfer•SMS
–“short message service”•E-mail
Disadvantages
–Cell towers had a limited coverage area
–Abrupt dropped calls
–gradual sound reduction
--“Spotty” coverage
3G
--Developed in the late 1990s until present day
--Japan is the first country having introduced 3G nationally, and in Japan the transition to 3G is being largely completed during 2005/2006
Features
--Large capacity and broadband capabilities
--Allows the transmission of 384kbps for mobile systems and up to 2Mbps
–A greater number of users that can be simultaneously supported by a radio frequency bandwidth
–High data rates at lower incremental cost than 2G
–Global roaming
CDMA –Code Division Multiple Access is used
–Form of multiplexing
–Does not divide up the channel by time or frequency
–Encodes data with a special code associated with each channel
3G Applications
--Wireless Advertising
--Mobile Information
--Business Solutions
--Mobile Transactions
--Mobile Entertainment
--Person-to-Person Communications
--Bearer Entrance and Periodics
ISSUES ON 3G WIRELESS SYSTEM
--High input fees for the 3G service licenses
--Great differences in the licensing terms
--Current high debt of many telecommunication companies, making it more of a challenge to build the necessary infrastructure for 3G
--Health aspects of the effects of electromagnetic waves
--Expense and bulk of 3G phones
--Lack of 2G mobile user buy-in for 3G wireless service
--Lack of coverage because it is still new service
--High prices of 3G mobile services in some countries
4G
4G is a research item for next-generation wide-area cellular radio, where you have 1G, 2G, 3G and then 4G
4G Features
•Faster and more reliable
–Speed about 100 Mb/s
•Lower cost than previous generations
•Multi-standard wireless system
–Bluetooth, Wired, Wireless (802.11x)
•Ad Hoc Networking
•IPv6 Core
•OFDM used instead of CDMA
OFDM
•Orthogonal Frequency Division Multiplexing
•Allows for transfer of more data than other forms of multiplexing (time, frequency, code, etc)
•Simplifies the design of the transmitter & receiver
•Allows for use of almost the entire frequency band
–No gaps to prevent interference needed
•Currently used in WiMax(802.16) and Wi-Fi(802.11a/g)
--WALSH CODE is used in 4G
