CS345/912 Sensor Networks and Mobile Data Communications Term 1, 2023-2024

_________________________________________________________________________________________

__________________________________________________________________________

Victor Sanchez

Department of Computer Science, University of Warwick 1

Coursework Specification

I. Introduction

Two villages 10 kilometres apart communicate through a Delay Tolerant Network (DTN).

Village 1, which has the transceiver Node 0, sends packets to transceiver Node 1. Node 1 is

located in a bus that travels to the vicinity of Village 2, where it will transfer the packets to

transceiver Node 2. The position of all nodes is depicted in Fig. 1, where d = 3 m.

Fig. 1. Initial position of nodes

Node operation

Village 1 - Node 0

Several readings are generated by Node 0 at a rate of 1 reading per second. These readings

are stamped with the order in which they are generated and stored in a buffer. The elements

in the buffer are represented in the simulation by two variables: head and tail. The buffer

in Node 0 can only accommodate three readings; when the buffer is full, the oldest reading

in the buffer is thrown away. Assuming no data is transmitted to Node 1, the contents of

Node 0’s buffer change as tabulated in Table 1.

d

10000 m

Node 0 Node 2

Node 1

x

y

CS345/912 Sensor Networks and Mobile Data Communications Term 1, 2023-2024

_________________________________________________________________________________________

__________________________________________________________________________

Victor Sanchez

Department of Computer Science, University of Warwick 2

Table 1. Contents of Node 0’s buffer assuming no data transmission.

No. of readings

generated

No. of readings

stored in buffer Stamps Simulation variables

Head Tail

0 0 0 0

1 1 [1] 1 1

2 2 [1,2] 2 1

3 3 [1,2,3] 3 1

4 3 [2,3,4] 4 2

5 3 [3,4,5] 5 3

… … … … …

As long as the buffer is not empty, Node 0 encapsulates the buffer’s contents into a packet

and transmits it to Node 1 at the rate of 4 packets per second. Upon receiving an

acknowledgement from Node 1, Node 0 clears the contents of its buffer.

The bus - Node 1

After receiving a data packet from Node 0, Node 1 stores the contents of the packet into its

buffer, and then acknowledges the reception of the packet. After acknowledging the packet,

Node 1 repeatedly transmits data packets to Node 2 at the rate of 4 packets per second. Node

1 also encapsulates its buffer into a packet. Node 1 only stops transmitting a data packet

upon receiving an acknowledgement from Node 2. Note, however, that Node 1’s buffer can

change before it can successfully send a packet to Node 2. This will happen for instance

when it receives a new packet from Node 0.

Village 2- Node 2

Upon receiving a data packet from Node 1, Node 2 sends an acknowledgement.

II. Methods

Use code CS345_BASE_2023.cc, which is available on the module webpage, to complete

this coursework. The bus as simulated in the code does not move. You can verify this by

running the code: it is only the bus and Village 1 that interact.

a. Introduce a mobility model such that Node 1 moves at a constant speed of 20m/s.

Make sure that the bus moves in a straight line up to the x-coordinate of Village 2

(Node 1 should stop once it reaches this destination). After implementing the

mobility of the bus, make sure that all nodes interact according to the behaviour

described before. [15 marks]

b. Determine the transmission range of Village 1 and Village 2 and the region where the

bus can receive/transmit to both villages (if any). When running your simulations,

make sure that the duration of the simulation is long enough for Node 1 to move to

the same x-coordinate as that of Node 2. [5 marks]

CS345/912 Sensor Networks and Mobile Data Communications Term 1, 2023-2024

_________________________________________________________________________________________

__________________________________________________________________________

Victor Sanchez

Department of Computer Science, University of Warwick 3

c. Modify the code so that every time Node 2 receives a unique packet, it also prints the

number of readings received so far. [5 marks]

d. Plot the relationship between the speed of Node 1, distance d, and the number of

readings received by Node 2. To this end, test a speed from 20m/s to 200m/s

(increments of 10m/s) and a distance d from 3m to 303m (increments of 6 m). Note

that this relationship can be plotted in different ways, e.g., line plots or 3D plots.

How does the speed of Node 1 and distance d affect the number of readings received

by Node 2? Explain. [10 marks]

e. Modify the behaviour of Node 1 so that it keeps all received readings in its buffer.

For example:

Node 1’s current buffer: [1, 2, 3]

EVENT: data packet is received by Node 1 with readings [4, 5, 6]

Node 1’s new buffer: [1, 2, 3, 4, 5, 6]

[10 marks]

f. Repeat the experiment in II.d, but this time using the modified code from II.e. Plot

the relationship between the speed of Node 1, distance d, and the number of readings

received by Node 2. Explain any differences with the plot obtained in II.d.

[5 marks]

g. Add a mobile node (Node 3) to the DTN. This additional node must be initially

located to the left of Node 1 at a distance d2 = 250 m (see Fig. 3). Node 3 must have

the same y-coordinate and speed as those of Node 1. Node 3 must have the same

behaviour as that of Node 1 (after all previous modifications introduced); i.e., it

should be able to receive packets from Node 0 and transmit packets to Node 2.

Fig. 3. Initial position of nodes with additional node.

d

10000 m

Node 0 Node 2

Node 1

x

y

Node 3 d2 = 250 m

CS345/912 Sensor Networks and Mobile Data Communications Term 1, 2023-2024

_________________________________________________________________________________________

__________________________________________________________________________

Victor Sanchez

Department of Computer Science, University of Warwick 4

Note that by adding Node 3 to the DTN, the following aspects should be considered:

• Node 0 is originally hard-coded to transmit exclusively to Node 1. You should

modify Node 0’s behaviour so that it can transmit (broadcast) to both Node 1 and

Node 3. Hint: you may use the method SetAllowBroadcast.

• Node 2 should be able to receive data packets from Node 1 and Node 3. Node 2

must be able to properly count the number of readings received. It is possible for

the readings transmitted by Node 1 and Node 3 to overlap. For example, Node 1

may transmit readings 1-6, while Node 3 may transmit readings 4-7. The total

number of received readings, in this case, is 7; i.e., [1, 2, 3, 4, 5, 6,

7]. It is also possible for Node 1 and Node 3 to transmit different readings. For

example, Node 1 may transmit readings 1-6, while Node 3 may transmit readings

10-12. The total number of received readings in this case is 9; i.e., [1, 2, 3,

4, 5, 6, 10, 11, 12]. Node 2 must be able to deal with both cases

properly. [30 marks]

h. Plot the relationship between distance d2, as depicted in Fig. 3, distance d, and the

total number of readings received by Node 2. Set the speed of Node 1 and Node 3 to

20m/s. Test distance d from 3m to 303m (increments of 6 m). Test distance d2 from

50m to 1000m (increments of 50 m). When running your simulations, make sure that

the duration of the simulation is long enough for Node 3 to move to the same xcoordinate as that of Node 2. Explain and discuss any differences in the plot

compared to the one obtained in II.f for a speed of 20m/s. [10 marks]

III. Deliverables

Submit the following via Tabula:

1. A report with a description of how the DTN was modified according to each subsection

of Section II, as well as the requested explanations, discussions, and plots. Make sure to

include snippets of code showing your modifications to the code. Cleary explain these

modifications.

2. Your final solution for II.g as a cc file. Please make sure that the submitted code

compiles and works correctly before submitting.

A total of 10 marks are available for the quality and presentation of reports, as well as the

organization and explanation of your code (comment your code appropriately to indicate the

changes made). Documents should be clearly and logically structured, well-written, and

adequately proof-read before submission. The suggested length is between 1600-1800

words. The standard department late penalties and plagiarism policies are in effect.

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