Image Processing Reference
In-Depth Information
A
B
A
B
C
D
C
D
(a)
(b)
FIGURE .
(a) Physically arranged sensor nodes (solid circles). All nodes are in transmission range (dotted
line) of each other. (b) Virtually arranged nodes with appropriated transmission ranges. Nodes are not longer able to
communicate without routing.
of software regarding communication effort, self-organization of the network, routing, and data
aggregation is most important.
Figure . illustrates the difference between laboratory and real world. The left side represents
laboratory conditions where all nodes are in transmission range of each other. he right side sketches
the flood prevention scenario under real conditions. On the left side, the nodes A-D are in transmis-
sion range of each other. herefore in contrast to the real-world scenario, no routing is required. Next,
data aggregation yields wrong results, because nodes are not grouped as they would in reality. hus,
if physically arranged nodes in test environment do not meet the requirements of the real world, the
results are questionable.
Assume, node A sends a message to node D, then all nodes receive the message due to the physical
vicinity in the test environment (Figure .a). Nodes C and D receive the message, but they are not
in the virtual transmission range of node A. hus, the environment emulation module rejects these
messages. As a result, SeNeTs prevents a direct transmission from node A to node D. Messages can
be transmitted only by using routing nodes B and C (Figure .b). In short, the emulation of the
sensor network software becomes more realistic.
12.4.4 J-Sim
J-Sim is primarily designed to simulate any network composed of nodes []. [].The simulator is based
on autonomous component architecture (ACA). On top of the ACA, a packet switched internetwork-
ing framework (INET) is deined. he component design in J-Sim is very similar to an integrated chip
(IC) design architecture where each chip is defined as stand-alone module communicating with other
chips via wires. Due to their simple interface (port), components can be designed, developed, and
tested individually. Each port contains a contract which describes the type of information exchanged
with other components to ensure the statical-type safety.
The simulator is written in Java which is also used to compile components. Supplementary, Tcl
is applied to control the simulation process via scripts. Therefore, it is platform-independent and
extensible. At runtime, all required components are instantiated and their ports are connected via
Tcl scripts. he runtime environment of the simulator and each instance of components are inserted
in a virtual directory tree which can be accessed by any simulation element or other scripts.
To simulate sensor networks, J-Sim provides a specialized add-on called Sensorsim framework []
using ACA and INET. It requires only a fractional amount of memory to simulate correctly compared
