1. Route Discovery Latency in On-demand Routing Protocol
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Route Discovery Latency in On-demand Routing Protocol
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Y. Jeong, and J Ma, ICU
John Doe, Some Company

2. Route Discovery Latency in On-demand Routing Protocol Yeonkwon Jeong Joongsoo Ma Mobile Multimedia Research Center Information and Communications University
Y. Jeong, and J Ma, ICU

3. Summary Mesh group is considering two kinds of routing protocol:
On-demand(reactive) routing protocol: AODV, DSR
Proactive routing protocol: OLSR, DSDV
One of well-known weaknesses in on-demand routing protocols is that they
Need extra route discovery latency.
Request more data buffer during route discovery.
This presentation will show
The measurement results of route discovery latency in on-demand routing protocol through several experiments on our test-bed.
Those results to know ‘what are the main factors increasing route discovery latency’.
Y. Jeong, and J Ma, ICU

4. Outline Mesh Networking Architecture Two Kinds of Routing Protocol
Experiment Environment
Experiment Results
Considering Factors
Conclusions
Backup Slides
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5. Mesh Networking Architecture
Mesh Portal
Mesh AP
Mesh Point
STA
Mesh
Portal MP
STA3 MP
MAP
MAP
STA1 MP
STA2
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6. Two kinds of Routing Protocol[1]
On-demand Routing
Discovers and maintains routes only when they are needed
Pro:
Route maintenance only when needed
Reduce the effects of stale routes and overhead due to topology changes (mobility, mesh point failures or power down, etc.)
No need to maintain unused routes
Con:
Extra route discovery latency and data buffer during route discovery
Proactive Routing
Each node maintains routes to all reachable destinations at all times, whether or not there is current need to deliver data to those destinations.
Pro:
Little delay
Con:
Routing overhead to keep network topology (frequent changes)
Y. Jeong, and J Ma, ICU

7. Experiment Environment
node1
node2
node3
node4
node5
Background Traffics: 2.5Mbps
Setup a route from source to destination node
Use PING message
MAC Parameters
Beacon Interval: 100ms
ATIM Window: 5ms
RDL(Route Discovery Latency) = Trx_rrep – Ttx_rreq
Send background traffics at 2.5Mbps rate from node5 to node2.
Equipment
Type
Laptop Computer
Samsung Sens 900
Wireless LAN card
Cisco Aironet 350 series OS
Linux Redhat 8.0
Kernel version
Routing Protocol
AODV[2]
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8. Experiment Results(1) Average Route Discovery Latency # of Hops
non-PSM
PSM
w/o BT
w/t BT 2
4.45ms
4.92ms
78.817ms
684ms 3
7.26ms
8.76ms
160.27ms
1,710.5ms 4
334.4ms
1,298.33ms
657.69ms
2,966.33ms
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9. Experiment Results(2) Average Route Discovery Latency
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10. Experiment Results(3) Average Re-Route Discovery Latency
node1
node2
node A
node4
node5
node B
Average Re-Route Discovery Latency
Processing Time: Ttx_rreq – Trx_rerr
Route discovery latency: Trx_rrep – Ttx_rreq
Processing Time: Avg ms
# of Hops
non-PSM
PSM 3
648.48ms
796.86ms 4
984.42ms ms
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11. Considering Factors(1): Expanding Ring Search
To prevent unnecessary network-wide dissemination of RREQ
Dissemination of RREQ use Expanding Ring Search technique
Adjust ‘TTL’ field in IP header
After sending RREQ, Nodeorig of sending RREQ must wait RREP for following time
Ring_Search_Time = 2*40ms*(TTL_Value + 2)
# of RREQ trial
TTL_Value
Waiting Time
1st 2
320ms
4th 8
800ms
2nd 4
480ms
5th 35
2800ms
3rd 6
640ms
6th
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12. Considering Factor(2): IEEE802.11 PSM Operation
Hop-by-Hop wakeup mechanism
When the number of hops is N, the possible transmission delays can be increased until
(BI-ATIM window) +BI*(N-1)
The transmission delays are dependent on the number of hops and node states such as awake or doze.
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13. Conclusions
As the number of hops increases, the route discovery latency is increased
Design considerations
How many MPs can be supported?
What is the average number of hops?
Do you have efficient ring search mechanism to disseminate RREQ?
How to reduce the transmission delay in PSM?
Broadcast
Multicast
How much buffer spaces is required?
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14. References
[1] W-Mesh Alliance, “Wi-Mesh Alliance Proposal for TGs”, IEEE /573r3, July, 2005
[2] C.perkins, E.Royer, S.Das, “Ad-hoc On-Demand Distance Vector (AODV) Routing”, IETF Internet draft, draft-ietf-manet-aodv-13.txt, Feb
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15. Backup Slides
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16. UDP Performances Scenario
Source
Node2
Node3
Node4
Node5
Various Traffic
Fixed Size Data
Scenario
Send traffics from node5 to source at from 0 ~ 5Mbps
Source also sends traffics to destination for 100 seconds
Use fixed size data at 0.6Mbps
MTU size: 1450byte + IP Header
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17. TCP Performances Scenario The received data rate (Kbyte/s)
Source sends a file to destination
Use FTP program
File size: 30MBytes
The received data rate (Kbyte/s)
# of Hops　
non-PSM
PSM 1
530.24
500.13 2
270.3
120.69 3
150.63
64.2 4
120.18
27.72
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