04-06-2012, 10:42 AM
Cellular Networks:Architectural and Functional Overview, Evolving Trends, and Clean Slate Design Paradigms
Cellular NetworksArchitectural and Functional Overview.ppt (Size: 336 KB / Downloads: 34)
Some More Basics
Uplink & Downlink separated in
Time: Time Division Duplex (TDD), or
Frequency: Frequency Division Duplex (FDD)
Information (voice, data) is digitized and bit streams modulated onto carrier
Modulation, data redundancy (coding), transmission power, data retransmissions (ARQ) adapted to varying wireless channel quality
Spatial attenuation of signal
Frequency or codes can be reused (frequency reuse)
Global System for Mobile communications (GSM)
900/1800 MHz band (US: 850/1900 MHz)
For 900 MHz band
Uplink: 890-915
Downlink: 935-960
25 MHz bandwidth - 124 carrier frequency channels, spaced 200KHz apart
Time Division Multiplexing for 8 full rate speech channels per frequency channel.
Circuit Switched Data with data rate of 9.6 kbps
Handset transmission power limited to 2 W in GSM850/900 and 1 W in GSM1800/1900.
The Base Station Subsystem (BSS)
Base Transceiver Station BTS - transceivers serve different frequencies.
Frequency hopping by handsets and transceivers
Sectorization using directional antennas
Base Station Controller (BSC) controls several (tens to hundreds) of BTSs
allocation of radio channels
handovers between BTSs
concentrator of traffic
databases with information such as carrier frequencies, frequency hopping lists, power reduction levels, etc. for each cell site.