Fig. 9. Interception-based reconfiguration.
7 Gateway Placement
For data gathering in wireless sensor networks, one way is to place multiple gateways
in the network to reduce the traversing hops of data. Sensor nodes send data packets
to their nearest gateways, and the data are gathered from these gateways through
Chapter 13 Data Aggregation in Wireless Sensor Networks 345
wired lines to a data center. The issue involved in this data gathering model is how
to optimize the placement of gateways.
In [14], J. Wong et al. use integer linear programming (ILP) to calculate the
optimal gateway placement under the assumption of known node positions and communication
range.
First the possible positions to place the gateways are found by identifying competitive
regions (CRegions). A region here is defined as the overlapping communication
ranges of a set of nodes. Thus if a gateway is placed in this region, it can
communicate with these nodes in one hop.
Then breadth-first search is used to determine the number of communication hops
needed between each node and potential gateway position pair.
Next, the network size is examined to determine the algorithm used. If the network
is of a reasonable size, then ILP is used to find the optimal solution, else a
heuristic approach is used to determine the approximately best placement.
There are four common optimization scenarios:
1. For a given bound on the number of communication hops for each sensor node
to reach at least one gateway, minimize the number of gateways.
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