Cellular Data Networking

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Cellular data networking means connecting to the Internet via the device’s cellular radio and the handset’s network provider.

•  data rate depends on the technology supported by both the phone and the cell tower
  • E.g., 3G or 4G
• likely to be charges based on the amount of data transferred
  • can be high when the phone is used abroad
    • referred to as international roaming
  • useful to be able to disable mobile data access

Global System for Mobile Communications vs. Code-Division Multiple Access

• two competing 2G and 3G cellular network types, established in different markets:
  • Global System for Mobile Communication (GSM)
    • allows subscribers to use a removable subscriber identity module (SIM) card to use an unlocked handset with their chosen network provider
    • adopted internationally and by AT&T and T-Mobile in the United States
  • Code Division Multiple Access (CDMA)
    • the handset is directly managed by the provider and there is no removable SIM card
    • adoption is largely restricted to the telecom providers Sprint and Verizon
    • information that the cellular radio needs to connect to the network is provided as a preferred roaming list (PRL) update
      • an be triggered from the device’s Settings menu or by dialing a special code, such as 228
• Long Term Evolution (LTE) 4G and 5G standards have removed this distinction
  • All 4G and 5G cellular data connections require a SIM card
  • Devices with SIM cards do not require the PRL to be updated manually

Cellular Networking Data Indicators

• When the cellular radio is enabled, the icon on the status bar shows which generation of data connection has been established:
  • G/E or 1X
    • G or E for GSM
    • 1X for CDMA
    • represent minimal 2G service levels
    • connection speeds of 50–400 Kb/s only
  • 3G
    • Universal Mobile Telecommunications Service (UMTS) on a GSM handset
    • Evolution-Data Optimized (EV-DO) on CDMA networks
    • 3 Mb/s
  • H/H+
    • High Speed Packet Access (HSPA) provides improved “3.75G” data rates on GSM networks
    • HSPA+ can work at up to 42 Mb/s
      • real-world performance is likely to be lower
  • 4G/4G+
    • LTE-Advanced
    • maximum downlink of 300 Mb/s in theory
      • no provider networks can deliver that sort of speed
    • 20–90 Mb/s typical of real-world performance
  • 5G
    • 50 Mb/s to 300 Mb/s real-world speeds

Enabling and Disabling Cellular Data

• cellular data connection can usually be enabled or disabled via the notification shade
• can usually
  • set usage warnings and caps
  • prevent selected apps from using cellular data connections
• Some handsets support the use of two SIMs
  • can choose which one to use for data networking