Nodes Move Randomly

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4.2.3 Nodes Move Randomly  

With all nodes move randomly, this is an extreme case for our design. The M1 method is almost failed to work here. A leader node is difficult to meet another one with the way which is long enough to satisfy the conditions of M1 group forming. Nodes can only work with M2 method all the time.

Figure 17：Number of dead nodes in scenario 3 (Nodes move randomly).

Figure 17 shows the number of dead nodes in scenario 3 (Nodes move randomly). With the M2 method, a group is rapidly changing so that the effect of energy saving is limited.

Before 52 nodes have been dead, our design is more efficient for energy saving than Epidemic with high message duplication and PROPHET with high information computing. After that,

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nodes are too sparely distributed to reduce the opportunist of a contact. It mitigates energy consumption for message relay especially in Epidemic.

Figure 18：Delivery ratio in scenario 3 (Nodes move randomly).

Figure 18 shows the delivery ratio in scenario 3 (Nodes move randomly). Although this extreme scenario attacks the weakness in energy saving of our design, we can still make good delivery ratio in the relatively high level. Because of lower M1 groups, there are less

dangerous situations of destroying M1 groups in scenario 2 and also make the curve much better than it in scenario 2.

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Table 5：Summary of the end in Scenario 3 (Nodes move randomly).

The summary of the end in scenario 3 shows in table 5.Our design still has good performance of delivery ratio and overhead ratio. Although we are using GPS information which cost much energy for simple computing to make decisions, the table shows the benefit of lower computing to node’s lifetime. Nodes with high computing to maintain delivery ratio such as PROPHET routing protocol, makes nodes die quickly and then affect its delivery ratio.

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Conclusions and Future Work

5.1 Conclusion  

We propose two designs M1, M2 with lower redundancy copies and lower information computing but good delivery ratio in energy limitation environment. The M1 design works well in “no depart” environment. The M2 design is more suitable for rapidly changing environment even if there is no group。

Considering the moving pattern of people, our designs are more suitable for real-life implementation. Our designs make number of nodes alive 3 times more than others in the environment with groups.

5.2 Future Work  

In this thesis, our main idea is left only one node alive for a group. There are many of energy saving designs for one single node in DTNs. We will try to combine two or more energy saving design to enhance our design to make it be more suitable for randomly moving scenario or other complex, unpredictable scenarios in DTNs.

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