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Wireless Networks
Matching Application Profiles
to Wireless Network's Capabilities
We have a choice of the following network technologies for
our mobile computing needs:
- SMR Private Networks
- ESMR - Enhanced SMR for radio voice and data
- Packet Radio (e.g., Motient, Bell South Wireless
Data)
- Paging networks e.g. Skytel for two-way paging
- Cellular (circuit switched)
- CDPD
- PCS - Second generation TDMA, CDMA
networks now and 2.5 G & 3G in future
- GSM (SMS -Short Messaging Services)
- Satellite-based wireless networks
Wireless networks have different characteristics, so it is
important to select a network that matches application requirements. The following table
compares the capabilities of different networks from an application perspective:
CAPABILITIES
OF VARIOUS WIRELESS NETWORKS |
| Network Technology |
Description |
Best Applications |
Geographical Coverage |
Speed and Performance |
Pros |
Cons |
| SMR |
Specialized radio network for
dispatch |
Dispatch: voice and data |
Local or regional |
4800 BPS |
Voice and data |
Slow speed, regional coverage |
| ESMR |
Digital radio to base stations,
then public wired network |
Voice/data: paging and short
messages for dispatch |
Regional |
4800 BPS |
Integrated voice and data; digital
network |
Limited application support |
| Circuit Switched Cellular |
Data sent over circuit-switched
cellular network via special modems |
File Transfer, long textual
messages |
Nationwide |
4800-14400 |
Good coverage; economical for file
transfer |
Expensive for short messages |
| Packet Radio (Motient or RAM) |
Radio network designed for packet
data |
Short bursty (Point of sale,
database queries, fleet dispatch, telemetry) |
Nationwide |
4800-19200
(Motient) 8000 (RAM) |
National coverage, strong third-
party support |
Expensive for long files |
| Narrowband PCS |
New two-way PCS based network |
Short messages with brief
interaction |
Regional to national |
25.6 kbps on SkyTel |
Two-way messaging, cost attractive |
Emerging; limited messaging
protocol |
| Broadband PCS |
Initial focus on voice; data will
come later |
Not clear; potential for both
short messages and file transfer |
Currently available only as pilot
projects |
No reliable information available;
potential high |
Potentially could replace packet
radio, cellular, CDPD |
Pilot testing only; heavy
investment required |
| CDPD |
Packet-based digital data over
cellular infrastructure |
Short bursty (similar to
Motient and
RAM)
|
metropolitan areas now; national
eventually |
19200 BPS |
More ubiquitous coverage to come;
faster than RAM. |
coverage spotty; voice gets
higher priority |
| Satellite- Based Network |
Data sent over low earth-orbit
satellites |
High speed file transfer |
National and international |
9600 BPS |
Greatest coverage, except in
downtown core |
Limited availability |
Source: "Mobile Computing - A Systems Integrator's Handbook",
published by McGraw-Hill |
Although individual wireless networks are initially designed
for specific needs, over time, they tend to broaden their applicability, resulting in
overlap from one network to another. Thus, these days there is generally more than one
network appropriate for any given application, a fact that is highlighted in the following
table which lists application characteristics and corresponding network options:
Matching
Applications with Network Types |
| Application Type |
Network Choices |
Key Decision Factors |
| E-mail |
Motient or Ram
Mobile Data |
Economical for shorter, fewer
messages per user, per business session |
| |
Narrowband PCS |
Very economical |
| File Transfer and Fax |
Cellular Circuit Switched |
National coverage and cost are
the most important considerations |
| |
ESMR |
ESMR networks are being designed
for file transfer and fax services |
| Telemetry |
Motient, RAM, CDPD |
Short transactions in minimal
quantities at predictable intervals |
| Point of Sale/ Transaction
processing |
Packet Radio - Motient, RAM |
National coverage; more expensive
than CDPD |
| |
Circuit Switched Cellular |
National coverage; expensive
response time; takes 30 seconds to set up call |
| |
CDPD |
|
| Fleet Dispatch |
ESMR |
Voice and data integration on the
same device; one way messaging now, two-way to come; short messages |
| |
Private Packet Radio |
Coverage; two-way messaging |
| |
CDPD |
Limited coverage; speed; constant
connection; no set up time; cost |
| Couriers/Transportation |
Switched Circuit Cellular |
Nation-wide coverage, expensive
but large customers can get discounts |
| |
Private packet radio |
Nationwide coverage, cost, short
transaction |
| |
CDPD |
Limited coverage; less expensive
than circuit-switched cellular and private radio; speedy response time at 19200 bps |
| Public Safety (police, fire,
ambulance) |
Spread Spectrum |
Limited area in municipalities;
very low cost |
| |
CDPD |
Per user per month price model is
attractive; coverage may be acceptable |
| |
Private Radio Packet |
Cost for many applications and
agencies is attractive; consistent response time |
| Database Access |
Spread Spectrum |
Cheap in a campus environment |
| |
Private Packet Radio |
Acceptable only for mobile-ware
DBMS applications |
| |
CDPD |
Coverage; response time at 19200
could be less |
Source : Source: "Mobile Computing - A Systems Integrator's
Handbook", published by McGraw-Hill |
| Note: The table is
for illustrative purposes only. It does not imply that only the specified network types
can be used for a given application. |
Network Choice Dependent on Communications
Software & Application Support
We would like to caution readers that the choice of a network
should be based as much on its inherent transportability as on several other factors,
including the availability of compatible communications software and application
development tools. The final choice in selecting a network will inevitably be based on
more comprehensive criteria than the above suggestions. The second table merely attempts
to highlight the more obvious choices on the assumption that other fundamental needs such
as software compatibility, security, and network management have already been
considered.
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