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					   P ARADIGM           CHANGE




Use of mapping for
WiFi connectivity
                                 Prologue                                            One solution to this problem could be a
    In rural India,              Maps form an integral part of planning.             hybrid network architecture, which
                                                                                     combines physical and wireless data transfer
    there is a need of           There are different techniques by which,
                                 maps are prepared, depending upon the pur-          to enable high-bandwidth intranet and
                                                                                     Internet connectivity among kiosks (public
    cost-effective               pose and accuracy required. The different
                                 techniques, range from simple chain and             computers) and between kiosks and hubs
                                                                                     (places with a reliable Internet connection).
    network for data             tape measurements to optical methods and
                                 further to satellite based technologies.            Data is transported by means of the mobile
                                                                                     vechile (MV), which automatically and
    connectivity                     All the techniques have their own ad-
                                 vantages and disadvantages. Some gives              wirelessly collects and delivers data from/ to
                                                                                     each kiosk on the network.
    where                        good accuracy at the expense of time and
                                 energy while some gives quicker results at             Before the implementation of such a
                                                                                     concept, a detail map of the area under study
    communication                the expense of accuracy. However, GPS
                                 (Global Positioning System) is a world wide         need to be generated. Also required is the
                                                                                     route on which the MV would travel for
    infrastructure is            navigation and timing system, which is wide-
                                 ly being used for mapping, worldwide. This          covering the least distance, and the region
                                                                                     of maximum value of SNR (Signal to Noise
    lacking.                     article describes the use of mapping in plan-
                                 ning WiFi connectivity in rural India.              Ratio).
                                                                                        This required calculating the distance of
                                 Introduction                                        MV from the hub with corresponding
                                 Few villages of Dodaballabpur taluka in             values of SNR. To visualize the route of MV
                                 Rural Bangalore district, were thought of to        and the location of the hub, the value of
                                 be connected through WiFi to the nearest            SNR need to be plotted on the generated
                                 administrative centers, in order to facilitate      map so that the variation in the SNR values
                                 information exchange between the villages           are known, when the MV is moving and
                                 and the taluka headquarters.                        when the data transfer can start.
                                     But before the actual deployment of the         Developed solution
                                 technology took place, it was realized that
                                 there was a need of maps of the villages.           One requirement was to record the SNR
                                     These maps would help in finding out            values at specified interval with the GPS
                                 suitable location for the hub, where the            location of the MV. The other was to pre-
                                 antenna could be placed and also in decid-          pare the map of the villages, under study.
                                 ing the most suitable route for the moving          Finally, the collected values of SNR with
                                 vechile (MV) through which the data                 the distance from the hub need to be plot-
                                 exchange would take place.                          ted on the map of the village so that correct
                                     This planning would ensure that the             path of the MV could be decided. This
                                 information exchange between the MV and             would also result in deciding the location
                                 the hub could be done with maximum                  from which the data transfer should start so
                                 efficiency.                                         that there is no loss during the data transfer.
    Satyaprakash
    Project Manager
                                 Need analysis                                       Software development
    CSDMS, India
                                 In rural India, there is a need of cost-effective   For the first requirement, a MS windows
    satya@csdms.org
                                 network for data connectivity where                 based software was developed which had
                                 communication infrastructure is lacking.            the following features:

April 2004 | www.i4donline.net                                                                                                  31
Figure 1(a): GPS communication port setting (b): Adding stations to the tracks

                                                                                    Figure 2: Map of Arudhi village   Figure 3: SNR map for Arudhi village



                                                                                    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:
                                                                                    • The tracks were taken in the first pass by traversing on all the
Figure 1(c): Initial screen for data collection, which stores the location of the      possible route of MV. This was done by running the GPS in
points and calculate distance from the last point                                      continuous mode and GPS location data was captured at
                                                                                       every 1sec
                                                                                    • These tracks were then populated with the features present on
• Storing of fixed points from which to calculate distance                             the ground and were transferred to the collected track
• Real time monitoring of distance from all stored fixed points                     • The houses were drawn as polygon by taking two corners of the
• Drag-n-drop facility to choose the points that need to be                            houses by GPS and extending manually it, in depth
   observed                                                                         • The point features were marked simultaneously as pin-up
• Logging facility to store the points of the GPS                                   • Final map was created on the desktop, after making necessary
• Flexibility to choose the communication port on which GPS is                         corrections based on the observations from the field and appro-
   attached                                                                            priate colour and symbol was given to specific features
   The software records the GPS locations of the MV and calcu-                         Fig 2 shows the map created using the GramChitra software.
lates the distance of the point from the hub. Trimble
pathfinder pocket GPS with external antenna, was used in the                        Results achieved
study and the data was collected on a laptop installed in the MV.                   After the maps have been prepared and SNR has been collected,
Fig 1(a-c) show some of the screen shots of the software used for                   the SNR values were plotted on the map with respect to the dis-
data collection.                                                                    tance form the central hub. Figure 3 shows the SNR map for one of
                                                                                    the villages.
 Glossary                                                                               The solid colour shows the range of SNR values when the MV
                                                                                    is approaching the central hub from South-West direction along
 GPS: Global Positioning System: Global navigation                                  the road. The best SNR is for the region near to the central hub and
 and timing system which uses satellite to give loca-                               is almost same for both the directions. However, the shaded region
                                                                                    shows the values of SNR when the MV is approaching the central
 tion of the points
                                                                                    hub from North direction. Since the MV will not follow any other
 MV: Mobile Vechile: The moving vechile to/ from                                    route (there is only one main road) the SNR has been calculated for
 which the data will be transferred from/ to the hub                                the main road only.
 SNR: Signal to Noise Ratio: A measure of the strength                              Conclusion
 of the signal over which the data will be transferred                              The mapping of villages helped in finalizing the location of the
 PDA: Personal Digital Assistant, a handheld                                        hub and deciding the route of the MV for WiFi connectivity. This
 computer                                                                           facility at two locations of Rural Bangalore district viz., Arudhi and
                                                                                    Sasslu village, has helped the villagers in getting their land record
 GramChitra: Linux based GIS software for hand-                                     details under Bhoomi project of Karnatka state, without visiting
 held computer                                                                      the taluka headquarters. The GramChitra software, can help the
                                                                                    community in preparing map of the villages, as has been done in
 CF Card GPS: Compact Flash card GPS
                                                                                    the above application.

32                                                                                                                                           i4d | April 2004

				
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