1. Wireless Mesh Networks
Shyam Seshadri
Zaheer Ahmed
ECE 4605 Final Presentation

2. Context / Background EZ-Net DevKit Six wireless nodes
Dynamic configuration - different topologies (mesh, cluster tree, linear, hybrid)
Master node - network controller
End node - No routing functionality

3. RN+ vs. RN-
RN-
Uses far less resources at expense of routing capabilities
No routing table or route computation
Based on hierarchical routing
RN+
Capable of peer-to-peer on-demand routing
Asseses best routing option based on prior handshakes
Requests as well as responds to routing enquiries

4. Aims Configuring the network – static and dynamic
Establish PC-Node communication
Establish PC-PC communication
Range testing
Dynamic properties
Healing properties
RN+ vs. RN-

5. Initial Work: Network Setup
Initial configuration
Each node must be manually plugged into a PC through RS232
A specific topology and a specific node configuration is written
When the network is up, nodes can be dynamically configured to different topologies

6. PC – Node Communication
RSSI: Receiver Signal Strength Indicator

7. PC – PC Communication Connect a PC to each node using RS 232 cable
Use inbuilt “Transparency” feature
Like an Instant messenger
Allows the PCs to communicate as if directly connected through the RS 232
Hence “Transparency” – the intermediate wireless network is transparent to the PCs

8. PC – PC Communication

9. Range testing Linear topology Nodes used: A B Brought nodes very
close, then moved
apart
Fixed distance of
40m
60m

10. Dynamic Properties Linear topology with all six nodes
Removed and replaced
nodes one at a time
Observed time taken
for dataflow to begin
again

11. Dynamic Properties 1 byte/sec 100 byte/sec B 2.05s C 0.2s D 1.1s E
Constant queries are sent probing for the node to come back up

12. Hybrid 2 Network Diagram

13. Self-Healing Mechanism
Hybrid 2 network – Node A : Node F
Chooses route through node D to destination node F
Remove node D
15s – Re-routes through C
Remove node C
14s – Re-routes through B
Re-initialize D and C
Still uses route through B

14. Mesh Network Diagram

15. Self-Healing Mechanism II
Mesh Network (add diag) Node A : Node D
Remove B
15s – Re-route through C
Re-initialize B
No change in route taken
Route updating done only when current route is disturbed

16. Self-Healing Mechanism

17. Hybrid 3 Network Diagram

18. RN+ vs. RN- I Hybrid 3 network – Node A : Node E Remove C
15s: Error messages
Waiting for C to come back up
15s+: Time Out messages
Route update never received
C was the only RN+ node
RN- nodes incapable of providing route updates

19. Cluster tree 2 Network Diagram

20. RN+ vs. RN- II Cluster tree 2 – Node A : Node F With B as RN-
Route through C chosen
C is an RN+ with a routing table
With B as RN+
Few seconds taken initially to synchronize – errors seen on RSSI
Route through B chosen

21. Setbacks
Replacing the wireless antenna and re-configuring fixes problem of node not responding
Random losses during RSSI testing
Unable to run serial port scripts
Unstable application software
Fails to detect a connected node during some runs
Restart of application necessary

22. More research? Further investigation into RN+ and RN- nodes
Throughput tests
Tests with RF obstacles

23. Summary Different networks set up Range – up to 60m
Dynamic properties examined
Study of Self-healing properties
RN+ vs. RN-