Use of mapping for WiFi connectivity
Prologue
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Satyaprakash
Project Manager
CSDMS, India
satya@csdms.org |
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In
rural India, there is a need of cost-effective network for data
connectivity where communication infrastructure is lacking.
Maps form an integral part of planning. There are different techniques by
which, maps are prepared, depending upon the purpose and accuracy required.
The different techniques, range from simple chain and tape measurements to
optical methods and further to satellite based technologies.
All the techniques have
their own advantages and disadvantages. Some gives good accuracy at the
expense of time and energy while some gives quicker results at the expense
of accuracy. However, GPS (Global Positioning System) is a world wide
navigation and timing system, which is widely being used for mapping,
worldwide. This article describes the use of mapping in planning WiFi
connectivity in rural India.
Introduction
Few villages of
Dodaballabpur taluka in Rural Bangalore district, were thought of to be
connected through WiFi to the nearest administrative centers, in order to
facilitate information exchange between the villages and the taluka
headquarters.
But before the actual
deployment of the technology took place, it was realized that there was a
need of maps of the villages.
These maps would help in
finding out suitable location for the hub, where the antenna could be placed
and also in deciding the most suitable route for the moving vechile (MV)
through which the data
exchange would take place.
This planning would ensure
that the information exchange between the MV and the hub could be done with
maximum efficiency.
Need analysis
In rural India, there is a
need of cost-effective network for data connectivity where communication
infrastructure is lacking. One solution to this problem could be a hybrid
network architecture, which combines physical and wireless data transfer to
enable high-bandwidth intranet and Internet connectivity among kiosks (public
computers) and between kiosks and hubs (places with a reliable Internet
connection). Data is transported by means of the mobile vechile (MV), which
automatically and wirelessly collects and delivers data from/ to each kiosk on
the network.
Before the implementation of
such a concept, a detail map of the area under study need to be generated.
Also required is the route on which the MV would travel for covering the least
distance, and the region of maximum value of SNR (Signal to Noise Ratio).
This required calculating the
distance of MV from the hub with corresponding values of SNR. To visualize the
route of MV and the location of the hub, the value of SNR need to be plotted
on the generated map so that the variation in the SNR values are known, when
the MV is moving and when the data transfer can start.
Developed solution
One requirement was to record
the SNR values at specified interval with the GPS location of the MV. The
other was to prepare the map of the villages, under study. Finally, the
collected values of SNR with the distance from the hub need to be plotted on
the map of the village so that correct path of the MV could be decided. This
would also result in deciding the location from which the data transfer should
start so that there is no loss during the data transfer.
Software development
For the first requirement, a
MS windows based software was developed which had the following features:
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Storing of fixed points from which to calculate distance
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Real time monitoring of distance from all stored fixed points
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Drag-n-drop facility to choose the points that need to be
observed
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Logging facility to store the points of the GPS
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Flexibility to choose the communication port on which GPS is attached
Figure 1(a) GPS communication port
setting (b): Adding stations to the tracks
Figure 1(c) Initial
screen for data collection, which stores the location of the points and
calculate distance from the last point
Figure 2: Map of Arudhi village
Figure 3: SNR map for
Arundhi village
The software records the GPS
locations of the MV and calculates the distance of the point from the hub.
Trimble
pathfinder pocket GPS with external antenna, was used in the study and the
data was collected on a laptop installed in the MV. Fig 1(a-c) show some of
the screen shots of the software used for data collection.
Mapping
To prepare the map of the
area under study, GramChitra, the Linux based GPS data collection and GIS
software for handhelds, was used. The software runs on PDA, coupled with CF
card GPS, PDA used was 3800 series of iPAQ and the CF card GPS was of Pretec.
For mapping, the following
procedure was followed:
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The tracks were taken in the first pass by traversing on all the
possible route of MV. This was done by running the GPS in continuous mode and
GPS location data was captured at
every 1sec
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These tracks were then populated with the features present on the
ground and were transferred to the collected track
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The houses were drawn as polygon by taking two corners of the houses by
GPS and extending manually it, in depth
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The point features were marked simultaneously as pin-up
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Final map was created on the desktop, after making necessary
corrections based on the observations from the field and appropriate colour
and symbol was given to specific features
Fig 2 shows the map created
using the GramChitra software.
Results achieved
After the maps have been
prepared and SNR has been collected, the SNR values were plotted on the map
with respect to the distance form the central hub. Figure 3 shows the SNR map
for one of the villages.
The solid colour shows the
range of SNR values when the MV is approaching the central hub from South-West
direction along the road. The best SNR is for the region near to the central
hub and is almost same for both the directions. However, the shaded region
shows the values of SNR when the MV is approaching the central hub from North
direction. Since the MV will not follow any other route (there is only one
main road) the SNR has been calculated for the main road only.
Conclusion
The mapping of villages
helped in finalizing the location of the hub and deciding the route of the MV
for WiFi connectivity. This facility at two locations of Rural Bangalore
district viz., Arudhi and Sasslu village, has helped the villagers in getting
their land record details under Bhoomi project of Karnatka state, without
visiting the taluka headquarters. The GramChitra software, can help the
community in preparing map of the villages, as has been done in the above
application.
Glossary
GPS: Global Positioning System: Global navigation and timing system which
uses satellite to give location of the points
MV:
Mobile Vechile: The moving vechile to/ from which the data will be
transferred from/ to the hub
SNR:
Signal to Noise Ratio: A measure of the strength of the signal over
which the data will be transferred
PDA:
Personal Digital Assistant, a handheld
computer
GramChitra:
Linux based GIS software
for handheld computer
CF Card GPS: Compact
Flash card GPS
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