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This section shows how our software tools can be applied to
the general field of Private Mobile Radio (PMR) and specifically
how our products can be used to design, optimise and roll out
conventional and trunked mobile radio networks including technologies
such as MPT1327 and TETRA. The methods and sub-tools developed
within tools such as ICS Telecom have come from our work with
various customers. These companies have either used our tools
or have contracted ATDI to carry out work on their behalf to
further their development of mobile radio systems.
General PMR Planning Methods
The following general modelling methods
have application in mobile radio and are included in ATDI planning
tools.
- The ability to compute the coverage
of ground area from a given transmitter type and specification
to a given receiver type and specification.
- The ability to compute the degree
of interference suffered by both mobiles (down link) and base
stations (up link) from all on the same or adjacent channels.
- The degree of resilience built into
a system allowing the network to be optimised for overlap,
traffic demand or critical coverage.
- The ability to link the planning tools
via a network to develop the system using a number of planners
each with privilege to change their own zone yet compute the
effects of those adjacent.
- The ability to link the planning tools
via an Open DataBase Connectivity protocol to external database
such as Oracle and MS Access allowing the sharing of engineering
data across a multi-discipline project team.
- The counting of mobile population
covered under a transmitter footprint with the addition of
an irregular polygon limit.
- The counting of area under a transmitter
footprint but showing the results over a variety of different
urbanisation categories including roads, urban and suburban
areas with the addition of an irregular polygon limit.
Specific PMR Planning Methods
The design and subsequently the roll
out of PMR networks to cover both data and voice is a well established
process. There is however very great scope for automation of
the methods used and for optimisation of the engineering design
to critically engineer the network to meet the customer requirement
with the minimum base station and antenna system resources.
The specific methods noted below are some of the tools employable
to ensure that the planning engineer produces the most cost
effective system.
The coverage calculated can be filtered
to only display on specific ground use types such as roads or
railways. This then allows the planner to focus on the desired
target user for the service. Similarly, interference calculations
over rural or open areas away from that target user can be ignored
or reduced in significance.
Several views are possible once a coverage
computation from a given site has been made. The best server
view shows where on the ground mobile would vote or register
on the basis of field strength. The simultaneous communications
view shows which areas on the ground benefit from signal from
several sites and where a radio despatcher might be used to
access several repeaters.
The computation of traffic capacity of
a network will of course be dependant on the number of subscribers
served by a given base station. Traffic analysis can be done
using methods such as Erlang B or C. The traffic demand is made
up in a demand file directly in the planning tool.
ICS Telecom contains a host of sub-tools
to be used in site finding. This includes the ability to place
a series of points and to reverse the planning process to request
the locus of points where a useable signal will be received
from those locations. Once established a site can be positioned
there and the coverage probed. ICS Telecom allows the investigation
of the lie of the land in three dimensions allowing the engineer
to see directly the effect of positioning a site at a given
location.
For quasi-synchronous systems including
DQS ICS Telecom allows the user to analyse in both amplitude
and phase the effects encountered by the mobile in overlap areas
within the system. Once computed the planning engineer can introduce
a launch delay at each transmitter and optimise the effects
of overlap.
Once coverage has been assessed the operating
frequency of each site can be assigned automatically from a
frequency list. This is done primarily in the talk out path
by selecting the best frequency to maximise the C/I ratio experienced
by the mobiles.
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