PPT Slide

Cellular generations

(from the point of view of using multiplexing and spread spectrum)

• First generation: FDMA (FDM Access), where each cell supports a number of channels of equal bandwidth, and each cellphone uses two channels (one up and another down).
• Second generation in two groups:
  • TDMA (TDM Access): GSM (Global System for Mobile) and D-AMPS (IS-136). GSM is basically circuit-switching based, but GPRS (general packet radio service) was added to support data: SGSN (serving GPRS support node) and GSSN (gateway GPRS support node).
  • CDMA (CDM Access): CDMA comply with IS-95 (also known as cdmaOne). Uses DSSS combined with CDM. Designed by Qualcomm Inc, which holds IP over CDMA.

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