Information Technology Reference

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and comply with the specification of IRIS motes [
16
], as detailed earlier. Another

assumption is that the wireless network is in an isolated remote environment with

either slow moving or no mobility events. When a sending node tries to measure or

estimate channel parameters, it is assumed these channel parameters remain

unchanged for time periods longer than the typical packet transmission time as

discussed in [
17
]. The remaining parameters are summarized in Table
7.1
.

Before running the UDG model and the proposed correlated shadow fading

coverage model, Dijkstra's shortest path scheme was used to test the network

connectivity and only connected graphs were used in the simulations [
13
].

Furthermore, we discard network topologies that cause the simple UDG forwarding

model to fail to deliver data packets successfully. The proposed circular grid model

shown in Fig.
7.3
which contains an instance of the correlated shadow fading model

is produced for every transmitting node in the simulation area separately. Each node

is placed in the center of the circular field and the correlated shadow fading can be

produced as described in earlier.

Prior to discussing the results of simulations, we illustrate the path choice results

of each algorithm outlined in § 7.6, by describing the outcome of the operation of

all the algorithms described above in an example 50-node network over a 200 × 200

m
2
geographical region (Fig.
7.5
).

The simulation environment is programmed in Matlab, where the first step is to

generate uniformly distributed random node positions with the help of the built-in

function “
rand.
”
Rand
command generates values, which lie in the range of “0” and

“1” and is initialized with a different seed in each subsequent simulation.

After the generation of the node positions, the transmission radius of UDG,

which is found on the basis of receiver sensitivity (−101 dBm), was calculated to be

approximately 61 m. All nodes are assigned Cartesian coordinates to represent their

locations and the distances to all other nodes are calculated by Euclidean equation.

All nodes that lie within the distance of 61 m, i.e., transmission radius, are one-hop

neighbors. All one-hop neighbors will have the “
ppr
” (probability of packet reception)

as “1” while outside the transmission radius the “
ppr
” for UDG is taken as “0.” In the

case of UDG and Dijkstra the one-hop neighbors are exactly the same.

Table 7.1
Chosen simulation parameters

Parameters Used in Simulations

Height of transmitter antenna

1.5 m

Gain of transmitter antenna

2.16 dBi

Height of receiver antenna

1.5 m

Gain of receiver antenna

2.16 dBi

Power transmitted from transmitter

−27 dBW

Receiver sensitivity

−131 dBW

Transmitter/receiver frequency

2.1 GHz

Packet length

128 bits

BER model

Coherent QPSK

Neighbor selection threshold for probabilistic greedy algorithm

0.5

Degree of Reed-Muller forward error correction coding

3

Path-loss model

[
4
]

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