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This note describes how ATDI software can be used across current
Wireless Local Loop technologies including DECT and PMP to design,
optimise and roll out networks employing technologies such as TDMA,
CDMA, FDMA and mixed time and frequency domain transmission systems.
The methods and sub-tools within systems such as ICS telecom nG have
come from our work with various customers. The following general
modelling methods have application in fixed radio access/wireless
local loop and are included in ATDI planning tools.
General WLL Planning Methods
The following general modelling methods have
application in WLL networks and are included in ATDI planning tools.
Please refer to the technologies section on microwave links for
details of tools for transmission bearer planning.
- 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 subscribers (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 subscriber 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 urban and suburban areas with
the addition of an irregular polygon limit.
Specific WLL Planning Methods
The design and subsequently the roll out
of fixed radio access/wireless local loop networks are very unique.
Initially the design can progress as if the subscriber population
is mobile and using an omnidirectional antenna. At this point the
exact location of the subscriber is unknown. Very soon into the
project, the marketers in the team are able to input the likely
locations of subscribers from the voters roll or from chamber of
commerce data yet the base stations to which each would look for
service is still not set. Once the network commences deployment,
subscribers will be promoted from potential to actual with real
parent base stations and real antenna pointing. ICS telecom nG mirrors
this concept in allowing a three stage transition from a theoretical
to a practical network.
The coverage calculated can be filtered to
only display on specific ground use types such as suburban or urban
or industrial areas. This then allows the planner to focus on the
desired target market for the service. Similarly, interference calculations
over rural or open areas away from that target market can be ignored
or reduced in significance. This can be taken a stage further with
the introduction of a specific ground use layer representing the
service requirements. Instances where this has been used includes
the mapping of roof lines on a clutter file thereby allowing filtering
of all locations not at roof level.
can be set to calculate field strength or signal level
into a specific antenna only where there is a defined Fresnel Zone
clear of obstructions. This is particularly relevant for systems
in the region 3.5 GHz to 10 GHz and can be applied further in the
MVDS and bandwidth on demand services at 35-40 GHz. For such high
frequency systems no path between base station and subscriber is
of interest unless obstruction free.
Once subscriber locations are known, they
can be introduced into the planning tool via a subscriber database.
At this stage they are simply locations but once each subscriber
is parented to a base station this can be noted on the database
and the predicted signal level to each reported to installation
teams. Each subscriber is described by a directional antenna pointed
toward the parent. The objective in the intermediate stage in planning
is to parent the orphan subscribers whilst deploying a minimum of
base stations.
The computation of traffic capacity of a
network will of course be dependant on the number of subscribers
served by a given base station. In the early stages this might be
by best server. The planning task in hand requires that the engineer
parents the subscribers and he can do this in ICS telecom nG by directing
the traffic analysis sweeping certain subscribers up within a series
of irregular polygons. Once parented, the work proceeds using the
traffic demand noted in the subscriber database and directed into
base station parents.
The traffic generated per subscriber is variable
allowing for different subscriber terminal equipment serving differing
numbers of actual users. Subscribers and their callsign or telephone
number can be shown on screen at any time.
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