|
Wireless Networks
ESMR Wireless Networks
SMR networks are among the oldest implementations of radio
networks for voice and data dispatch applications. However, these networks use older
analog technology and consequently do not use the frequency
band as efficiently as they might.
The
specialized mobile radio (SMR) networks described on other pages of this site employ older
technology and consequently do not use the frequency band as efficiently as they might.
Though numerous in number, SMRs are very small in capacity, as measured by the number of
channels and mobile users supported. SMRs also concentrate on voice communications
primarily. Enhanced specialized mobile radio (ESMR) networks are essentially SMR networks
that operate in the same frequency band, but with enhanced capabilities which address the
shortcomings of SMRs. ESMRs, differ from SMRs in the following ways:
- ESMRs use more advanced digital technology.
- ESMRs use cellular techniques such as channel reuse.
- Wider in geographical coverage, ESMRs are regional and even national.
Enhanced SMRs are only now emerging in the U.S. as a result of a
recently adopted policy of the FCC to encourage consolidation and the establishment of
regional and even national SMRs that can use the scarce spectrums in the 800 MHz and 900
MHz bands more efficiently. (Most ESMRs use the new SMR spectrum allocation in the 900-MHz
band). The FCC calculates that more mobile users can be supported by larger networks with
a greater number of channels, a calculation based on the mathematics of queuing theory
familiar to telecommunications engineers. In simple terms, more than twice as many users
can be supported on a single 10-channel system than on two 5-channel systems.
As a result of the FCC’s new policy, a start-up company named FleetCall aggregated
the assets of several fleet dispatchers (taxi companies, construction companies and others
in similar businesses) and implemented a completely new digital wireless network called
Nextel. Nextel also has an equity share in Clearnet in Ontario, which has implemented a
similar network in Canada. Nextel and Clearnet combined provide a coast-to-coast
continental ESMR service now.
Application
Suitability
The Nextel ESMR network will offer the following services:
- Dispatching with two-way radio
- Two-way alphanumeric paging with acknowledgment and other data applications
- Cellular telephone capabilities
- Session or packet-data transmission without a separate modem.
In a sense, ESMR is a combination of cellular, paging, packet radio, and SMR in one
network. It follows that ESMR’s market emphasis is on combining services for
customers who use these features. Initially, FleetCall is starting off with analog
(eventually to be converted to digital) dispatching networks.
For more information on ESMR network, please refer to chapter
8 of the Mobile Computing Handbook or refer to other radio network books.
 For more info on
Nextel, go to the Nextel
Web Site by clicking here or on the image.
|
