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Wireless Networks
Wireless Wide Area Networks - SMR
Here are some brief facts about SMR (Specialized
Mobile Radio 0r Private Mobile Radio in Europe) wireless networks:
SMR networks were among the earliest
implementations of wireless networks for a single or multiple group of customers in a
vertical industry - taxi, public safety, or utilities.
The customer or a consolidator, on behalf of a
group of customers, obtains a license from FCC or similar bodies in other countries for
the exclusive use of a frequency band (generally in 400, 800 or 900 MHz range) in a given
geographical area.
The end user organization asks one of the
several network infrastructure suppliers (Motorola, Ericsson, EF Johnson - see vendor list
for category one of product guide) to bid, supply and install base stations,
antennas,
and associated equipment for the network.
Network provides both mobile radio voice call
and data (in 4800 or 9600 bps range) services e.g. for law enforcement applications.
Generally SMRs are local, metropolitan
or
regional in coverage
Underlying principle of SMR is that a user
bids for and occupies for a specified time one of several channels allocated to the SMR.
After the use, the user releases the channel for other person's use.
Typical cost of an SMR network is between
$40,000 to $120,000 for a 5 channel 800 MHz system. Typical flat rate charge for dispatch
service is $25 per month per user.
With increasing use of other more-efficient
wireless WAN technologies, FCC is gradually phasing out SMR networks except for
traditional applications. Also, recent implementation of Nextel's nationwide ESMR network
is as a result of a consolidation of many regional SMR licenses into a single national
network.
The following table gives additional information
about SMRs:
Specialized Mobile Radio
(SMR) Summary |
| Brief Description |
- An SMR service provides two-way land mobile communications on a
commercial basis to businesses, government and individuals.
- A license is needed to operate the network and use mobile radios. An
SMR operator may obtain a license for the user for fee.
- SMR operators provide their service for a monthly fee.
- SMR services include both voice and voice/data information exchange.
- SMR systems feature both conventional (non-shared channels) and
trunked (shared channel).
- SMR services interconnected with PSTN systems are close to cellular
services in nature.
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| Components |
- Mobile radio with mouthpiece for voice, portable radio or mobile
terminal.
- Mobile radio modem.
- Base station with antenna.
- Base station repeaters.
- Channel assignment microprocessors assign channels to mobile user
groups.
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| Frequency Bands |
- 800 MHz (Since 1974) and 900 MHz (since 1990s).
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| Coverage |
- Licensed widely throughout urban and rural USA and other countries.
Over 7,000 licenses with over one million users in the USA.
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| Capacity and Speed |
- The average SMR system has 6-7 channels per system; 40-50 mobile
users per channel;
- Data speeds of 1200, 2400, 4800, 9600 and 19200 bps.
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| Most Suitable Applications |
- Dispatch of police, fire and ambulance personnel.
- Taxi dispatch.
- Truck dispatch.
- Service representative dispatch.
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| Typical Costs |
- 5 channel 800-MHz SMR system: $40,000-$120,000 (1-4 base stations).
- 5 channel 900-MHz SMR system: $100,000-$200,000 (1-4 base stations)
- Mobile Radio: $500-$2,000.
- $15-25 per month per mobile flat ( current tendency is to switch to
air-time usage basis).
- $ 35-45 per month per mobile for interconnection with
PSTN.
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| Availability |
- 800-MHz systems have been available for years.
- 900-MHz systems being set up now (see ESMR also).
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| Pros |
- Inexpensive service for specific applications – cheaper than
cellular.
- Performance controlled.
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| Cons |
- High capital costs.
- Data throughput speed limited.
- Voice-data priorities difficult to manage in older SMR systems.
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For more information on SMR, read chapter 8 of
the Mobile Computing Handbook or refer to other radio network books.
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