CDPD Network Summary
- CDPD is a wireless mobile packet
data network, created as an overlay on the existing cellular
network. It uses same frequency as cellular and utilizes
"holes" in channels not being used for voice
transmission at any given time.
- Mobile End Station (M-ES),
Mobile Data Base Station (MDBS), Mobile Data Intermediate
System (MD-IS) and Fixed-End System (F-ES)
- Same frequency as cellular
- Currently in metropolitan areas,
expected to match cellular coverage by 1996 year end
- Presently enough for the current
set of users; carriers will upgrade based on demand. 19200 bps
for data. However, because of voice priority and packetization,
it is difficult to assume that you can effectively achieve
19200 as speed from user perspective.
- TCP/IP. Other protocols
supported through third-party gateways.
- Short OLTP transaction-based and
messaging, such as telemetry, credit authorization, e-mail
based messaging, public safety, transportation, etc.
- Long file transfer is NOT
suitable for CDPD.
- Prices under constant change at
present time; expect them to be slightly below Motient and RAM
initially for competitive reasons.
- It is available now but in large
metropolitan areas only.
- Higher than cellular but some
applications may need end-to-end encryption.
- Potential of full nationwide
coverage in future (1997)with seamless roaming within
- Link speed of 19,200 bps can
give good response times for OLTP-type short-message-length
applications, if carriers have enough channel capacity.
- Direct TCP/IP support means
fewer application changes.
- Support from RNA industry is
- Voice priority means
applications that are not "mobile-aware" could
suffer from poor response time and disconnection.
- Current level of coverage is not
adequate for national applications. Limited coverage in rural
- Inter-operability between
regional CDPD carriers has not been proven in production
- Cannot transmit facsimiles
directly to fax machines.
- Emerging network - end-to-end
systems-integration expertise is scarce