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Glossary : G

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collapse/expand Gateway
  • A network component that connects networks with different signaling and protocols. Gateway is a protocol translator. Gateway is often mentioned as a Layer 7 device. But in fact, the translation process involves all layers in the OSI model.
    Also see OSI model.

collapse/expand Gigabit Ethernet
  • Refers to Ethernet versions that provide 1000 Mbps data rate. The most popular is 1000BaseT that runs over twisted pair cable.
    Also see Ethernet.

collapse/expand GHz
  • Gigahertz. A frequency unit which is equivalent with a billion (109) Hertz's. Also see Hertz.

collapse/expand GPON
  • Gigabit PON. The latest PON (Passive Optical Network) specification that was defined by the ITU-T in G.984 series of standards. GPON offers advantages over other PON architectures (i.e. APON, BPON, and EPON). It provides downstream capacity of 2.5 Gbps and upstream of 1.25 Gbps and has longer fiber reach of up to 60 km from the CO. It supports RF video overlay, security with AES, and higher split ratio of 1:64. GPON was designed to provide triple play services (video, voice, data). GPON uses Ethernet encapsulation for carrying traffic.
    Also see PON.

collapse/expand GPRS
  • General Packet Radio Service. A packet-switching technology that runs over GSM/TDMA network. GPRS is often mentioned as 2.5G technology (between 2G and 3G).
    Internet connection using GPRS network gives true mobility. You can browse the Internet on your notebook using your mobile phone as the modem. Or you can also surf the Internet using your mobile phone's WAP browser. GPRS promises faster connection up to 115 kbps. Nonetheless, the Internet experience is like using a dial-up modem. Real world performance (data rate) depends on GPRS and GSM traffic condition and the connection pipe to the Internet.
    GPRS allocates unused GSM cell to carry data packets. Based on its data carrying capacity, GPRS device (e.g. mobile phone) is often classified into multi-slot classes as follows:

    Class Downlink Slots Uplink Slots Active Slots
    1 1 1 2
    2 2 1 3
    3 2 2 3
    4 3 1 4
    5 2 2 4
    6 3 2 4
    7 3 3 4
    8 4 1 5
    9 3 2 5
    10 4 2 5
    11 4 3 5
    12 4 4 5

    The sum of downlink slots and uplink slots that is used by a GPRS device in a GPRS session can not exceed the allowed active slots. Each time slot has a maximum capacity of 14.4 kbps.

collapse/expand GPS
  • A navigation system in which position or coordinate calculation is based on data coming from 3 or 4 geostationary satellites that circle the earth at an equatorial orbit at an altitude of 35,786 km. Besides standalone GPS receiver, GPS cards are available in the market for providing GPS basic positioning service to mobile devices. However, enhanced positioning service usually requires a subscription to a service provider.

collapse/expand GSM
  • Global System for Mobile Communications. The established standard for mobile communications using TDMA technology. Mostly adopted by mobile networks outside USA and Japan.