25-08-2017, 09:32 PM
Wide Area Mobile Data Services
MobileData.pdf (Size: 281.76 KB / Downloads: 45)
ARDIS
• IBM, Motorola
• Originally designed for service dispatch
• 400 Metro Areas, 90% business coverage
• High transmit power for building penetration
• Multiple transmitters per region
• 4.8 Kbps, upgrading to 19.2 Kbps
• Two-way capability
• Nationwide roaming recently introduced
EMBARC
• Motorola
• 931 MHz paging frequency
• Email broadcasting, one-way
• Used for news feeds
• Satellite transmission to groundstations for
local/regional retransmission
• 300 bps
• Different priority levels: standby (as
available), express (1 hour), priority (15
minutes)
MobileComm
• BellSouth Enterprises
• Text messaging, one-way paging
• Up to 500 characters in length
• Single large regional transmitter
• Nationwide coverage
• ASAP, standard, overnight priorities
• PCMCIA cards for popular PDAs
RAM Mobile Data
• RAM Broadcasting Corp., New York
• 2-way data communications services
• 90% urban business area coverage
• Based on Ericsson Mobitex technology
• Packet-switched data, 8 kbps
• Hierarchical architecture of intelligent base
stations and switches
• Supports roaming, store-and-forward
messaging, TCP/IP interfaces
SkyTel
• SkyTel Corp., Washington, DC
• First satellite-based paging service
• Alphanumeric paging
• 4.8 Kbps, 240 character messages max
• 2-way paging systems being deployed
Metricom
• Microcellular “packet relay” network
• 1-5 mile cell diameter
• Poletap radios: 100 kbps, geographic routing
• Wired access points: every 2-3 hops to keep
latencies low (approx. 100 ms)
• User modems: 20-30 kbps effective data rate
• Uses 902-928 MHz ISM band and 1W
transmitters
• Available in SF Bay Area and Redmond, WA