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MOBITEX and Mobile Data Standards

Mobeen Kahn and John Kilpatrick, RAM Mobile Data

One-line summary: Overview of existing standards (there are so many!) for transmitting packetized data over unreliable RF links, with emphasis on MOBITEX, deployed by Ericsson and used by RAM mobile data.

Overview/Main Points

Existing wireline protocols (e.g. TCP) unsuited for wireless use:
Std Air IF NW layer transport comments
MOBITEX (Ericsson) ROSI (GMSK), 12.5 KHz chs, CRC/Hamming, selective ARQ MPAK (512 bytes, 24 bit addr); proprietary MTP/1, proprietary MASC interface: reliable data transfer (in-order?); most widely deployed today
ARDIS Single freq reuse; 4.8 Kb/s (MDC-4800) or 19.2Kb/s (RD-LAP) in 25 KHz ch ? ? RD-LAP deployment limited. ARDIS is one of only two nationwide providers. Single freq reuse is economical (single switching gateway, many BS's) but limits capacity.
CDPD (Baby Bells, McCaw) 19.2 Kb/s, FEC Drafted as proprietary; changed to IP/OSI after pressure from software industry TCP/OSI pkt-switching overlay for analog cel voice network. Since must operate within regulatory framework of phone companies, CDPD's must be modular, independent, interoperating networks.
AMPS (cel modem) Modulate data as voice at ~9600 baud; MNP-10, ETC, V.42bis for EC None None Must be able to stop/restart transmission after handoff or fade
Metricom FHSS, 902-928MHz (ISM) band, routing within radio mesh proprietary TCP/IP, AppleTalk via Hayes AT Up to 100 Kb/s--NOT
Destineer (MTel): 2-way paging over narrowband PCS; 2 separate networks TDD'd onto a single 50 KHz channel. Great use of a narrow slice of the spectrum, at the expense of response time.

Migration Paths/Future:


Overview of various packet-data standards, plea for standardization, overview of migration issues (primarily at the device driver level).


Shameless commercial plug for RAM Mobile Data.
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