D-AMPS (Digital Advanced Mobile Phone System) and GSM (Global System for Mobile Communications) are both second-generation (2G) mobile communication technologies, but they are not the same. While they share some similarities, they have distinct technical specifications and were developed by different standards organizations.
D-AMPS (IS-136):
- Development and Standards:
- D-AMPS, also known as IS-136, was developed in North America and is part of the IS-136 standard developed by the Telecommunications Industry Association (TIA) and the Electronics Industries Association (EIA).
- Multiple Access Scheme:
- D-AMPS uses Time Division Multiple Access (TDMA) for channel access, similar to GSM.
- Frequency Bands:
- D-AMPS operates in the 800 MHz frequency band, specifically in the Cellular (824–849 MHz) and PCS (1850–1910 MHz) bands.
- Speech Coding:
- D-AMPS uses a specific speech coding algorithm called VSELP (Vector Sum Excited Linear Prediction).
- Data Services:
- D-AMPS was primarily designed for voice communication, and its data services are limited compared to later technologies.
GSM (Global System for Mobile Communications):
- Development and Standards:
- GSM was developed in Europe and is part of the GSM standard developed by the European Telecommunications Standards Institute (ETSI).
- Multiple Access Scheme:
- GSM also uses Time Division Multiple Access (TDMA) for channel access.
- Frequency Bands:
- GSM operates in multiple frequency bands globally, including 900 MHz (GSM 900) and 1800 MHz (GSM 1800/DCS). The specific bands may vary depending on regional deployments.
- Speech Coding:
- GSM uses a speech coding algorithm called GSM Full Rate (GSM FR) for voice compression.
- Data Services:
- GSM introduced data services beyond basic voice communication, including Short Message Service (SMS) and later General Packet Radio Service (GPRS) for packet-switched data.
Key Differences:
- Geographical Deployment:
- D-AMPS was primarily deployed in North America, while GSM gained widespread global adoption.
- Frequency Bands:
- D-AMPS primarily operates in the 800 MHz band, while GSM has deployments in various frequency bands globally.
- Speech Coding and Standards Organizations:
- D-AMPS and GSM use different speech coding algorithms and were developed by different standards organizations.
While both D-AMPS and GSM belong to the same era of 2G technologies, they represent regional variations with some differences in standards, deployment, and features.