N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 9 - Wireless Systems and Technologies                                                                                 Slide 24 of 80                                                                                                    ________________

Second - Generation (2G) Systems Technologies

                                    Network Access 

                                    Channel Bandwidth

                                    Spectrum

                                    GSM, HSCSD, PHS/PDC and CDMA

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2G networks use TDMA and CDMA technology to allow mobiles to access the network.

Channel Access - TDMA allocates each mobile user a different time slot on a given frequency. GSM, D-AMPS and Personal Digital Cellular (PDC) use TDMA. PDC is a 2G network in Japan owned by NTT DoCoMo. Code Division Multiple Access is another technique used to access 2G systems. CDMA allows multiple frequencies to be used simultaneously. 

Channel Bandwidth  - D-AMPS and USDC use a 30 K Hz carrier while USN Spread Spectrum uses 1.25 M Hz, GSM uses 200 K Hz.

Spectrum - D-AMPS operates in the 800 - 1900 M Hz  frequency band. GSM is implemented on 900, 1800 and 1900 M Hz frequency bands.

High Speed Circuit Switched Data (HSCSD) - Used in GSM to increase data throughput to 14.4 K bps in a single channel.

PHY / PDC - Used in Japan in a Personal Digital Cellular system.