Year   Activity
1980 Motorola develops MDC-4800 protocol
1983 Motorola develops a wireless network for IBM's National Service Division to allow field service personnel to receive assignments and order parts from customer locations
1990 In January the ARDIS network goes live
1995 Motorola acquires 100% ownership of ARDIS
1996 At the end of the year ARDIS has more than 65,000 subscribers
1998 ARDIS is acquired by American Mobile Satellite Corporation (AMSC)
2000 In April Research In Motion (RIM) announces they will use Motient's DataTAC network to provide Internet access on the RIM 850 and 857 devices.

AMSC changes name to Motient.

2005 In March Motient announces a strategic change to their DataTAC network, focusing on the top 40 markets and "discontinuing service in in most of its outlying coverage areas."
2006 Motient Communications announces in February that coverage of its DataTAC network "will be focused toward on-street mobile coverage" and will reduce in-building coverage.

DataTAC network includes more than 2,200 base stations, providing coverage in more than 400 U.S. cities and 90% of the nation's population.

ARDIS came from Motorola's Data Radio Network (DRN) department and IBM.

ARDIS provided good in-building coverage by using overlapping coverage areas. Adjacent sites alternated transmission to avoid interfering with each other.

Motient DataTAC (Data Total Access Communications) [DataTAC 4000 in North America.]

Base stations transmit at 46 dBm, giving a cell radius of about 20 km.
Mobiles transmit at 36 dBm.

Channel access via slotted Digital Sense Multiple Access (DSMA).

Maximum message size is 2,048 bytes. Max OTA size is 256.

GFSK, 4.8 kbps

Convolutionally coded, rate 1/2, constraint length 7, of a 112-bit block. This block is put into a 7x16 matrix in column order and read out in row order.

Interleaving protects 3.3 ms (~16 bits) burst errors 90% of the time.

Packet length is 256 bytes; longer messages are subdivided into 240 byte packets and reassembled at the receiving end.

May also be known as Motorola Mobile Data Communications System (MODACOM).

Maximum message size is 2,048 bytes. Max OTA size is 512.

4FSK with SRRC filtering rO = 0.2.
9.6 kbps in 12.5 kHz channels; 19.2 kbps in 25 kHz channels

Trellis coded modulation, r = 3/4.

32-bit interleaving protects 1.7 ms
Cascaded CRCs with a final 32-bit CRC.

Comments, updates and corrections to Dan

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Last updated June 20, 2009