1. A Survey of Routing Protocols that Support Qos in Mobile Ad Hoc Networks
Lei Chen and Wendi B. Heinzelman , University of Rochester
IEEE Network. November/December 2007.
Presented by Pei-Wei Li

2. Authors
Wendi B. Heinzelman received Ph.D. degree in electrical engineering and computer science from MIT in 2000.
She is an associate professor in the Department of Electrical and Computer Engineering at the University of Rochester, New York.
Lei Chen received Ph.D. degree in electrical and computer engineering from the University of Rochester in 2006.
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3. Introduction
The explosive growth in the use of mobile devices and users’ desires for real-time application has provided new challenges in the design of protocols.
A routing protocol incorporating Qos is required.
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4. Outline Characteristics of MANET
Basic design considerations for a Qos-aware routing Protocol
Qos-aware Routing Protocols
Routing Protocol Performance Comparison
Open Issues in Qos-aware Routing
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5. Characteristics of MANET
Physical characteristics: wireless channels cause unpredictable bandwidth and delay.
Organizational format: the distributed nature means that resource cannot be allocated in a pre-determined way.
Dynamic topology: hosts are mobile, links are created and destroyed in an unpredictable way.
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6. Basic design considerations for a Qos-aware Routing Protocol
Resource estimation
Route discovery : Reactive/Proactive
Resource reservation
Route maintenance
Route selection
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7. Qos-aware Routing Protocol- Core-Extraction Distributed Ad Hoc Routing (CEDAR)
CEDAR establishes a core set for route set up.
Core nodes exchanges bandwidth information by disseminating increase waves and decrease waves.
Resource estimation: MAC/link layer can estimate available link bandwidth.
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8. Qos-aware Routing Protocol- Core-Extraction Distributed Ad Hoc Routing (CEDAR)
Core Broadcast (based on RTS-CTS)
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9. Qos-aware Routing Protocol- Core-Extraction Distributed Ad Hoc Routing (CEDAR)
Route discovery:
(1)Establishment of Core Path
--The dominator of the source initiates a core broadcast.
--The core hosts who relay this broadcast attach
their IDs in the packet.
--The dominator of the destination sends a ack to
the dominator of the source.
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10. Qos-aware Routing Protocol- Core-Extraction Distributed Ad Hoc Routing (CEDAR)
(2)Qos Route Computation: The source dominator tries to find a route that guarantees the required bandwidth according the core path.
Route maintenance: source or intermediate core node can initiate a route re-computation.
Source
destination T
dom(s)
dom(T)
dom(d)
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11. Qos-aware Routing Protocol- Ticket-based Qos Routing
Resource estimation: Bandwidth/delay information can be obtained from lower layers.
Route discovery:
Tickets are used to find bandwidth/delay constrained routes.
Route selection: The route with the lowest cost will be selected as primary route.
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12. Qos-aware Routing Protocol- Ticket-based Qos Routing
Resource reservation: The nodes will lock the corresponding resources when they receive a reply from destination.
Route maintenance: The host that discovers a route break searches for a local repair.
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13. Qos-aware Routing Protocol- Ad Hoc Qos On-demand Routing (AQOR)
Resource estimation:
--Available bandwidth estimation is according to the sum of the neighbors’ traffic information.
--One way end-to-end delay estimation is round trip delay.
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14. Qos-aware Routing Protocol- Ad Hoc Qos On-demand Routing (AQOR)
Route discovery
--The source broadcasts a route request.
--The intermediate hosts check their available bandwidth.
--Upon receiving each request packet, the destination will send back a reply packet.
Route selection: Source chooses the first in-time reply as route.
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15. Qos-aware Routing Protocol- Ad Hoc Qos On-demand Routing (AQOR)
Resource reservation: It is activated while the data flow passes the node along the selected route. The node only reserve resource for a certain time interval.
Route maintenance:
--neighbor lost detection: source initiate rerouting.
--Qos violation and reservation timeout: destination triggers route recovery.
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16. Qos-aware Routing Protocol-Trigger-based Distributed-Qos Routing (TDR)
A location-based routing protocol using -local neighbor database
-activity-based database
Resource estimation: Bandwidth information can be obtained from lower layers.
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17. Qos-aware Routing Protocol-Trigger-based Distributed-Qos Routing (TDR)
Route discovery:
-selective forwarding: only neighbors who receive the route discovery packet with power greater than a certain threshold are considered as possible links in the route.
-intermediate hosts check whether their residual bandwidth is sufficient to meet the request.
-loop-free routing: intermediate nodes accept the route discovery packet only once for a particular session.
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18. Qos-aware Routing Protocol-Trigger-based Distributed-Qos Routing (TDR)
Resource reservation: The nodes reserve resource for a certain time interval when receiving request and update available resource when receiving a ack message.
Route maintenance: using three different receive-power levels(Pth1>Pth2>Pcr) to predict route breaks.
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19. Qos-aware Routing Protocol-Adaptive Qos Routing Algorithm (ADQR)
Using three different received signal strength to predict route breaks and define nodes , links , routes.
Resource estimation: Bandwidth information can be obtained from lower layers.
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20. Qos-aware Routing Protocol-Adaptive Qos Routing Algorithm (ADQR)
Route discovery:
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21. Qos-aware Routing Protocol-Adaptive Qos Routing Algorithm (ADQR)
Route selection: routes with strong signal strength links have the highest selection priority.
Resource reservation: Source sends Qos_Reserve packet to perform bandwidth reservation.
Route maintenance: two-phase monitored rerouting composed of Pre_Rerouting and Rerouting.
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22. Qos-aware Routing Protocol-Qos-aware Routing Based on Bandwidth Estimation (BEQR)
Resource estimation:
--Listen bandwidth estimation
--Hello bandwidth estimation
Route maintenance: The host who cannot receive a Hello message from a downlink neighbor will send a error message to source.
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23. Qos-aware Routing Protocol-Qos-aware Routing Based on Bandwidth Estimation (BEQR)
Route discovery:
--call admission:
flow contention (i.e., inter-flow interference) is considered.
--adaptive feedback: flow self-contention (i.e., intra-flow interference) is considered.
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24. Routing Protocol Performance Comparison
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25. Routing Protocol Performance Comparison
Scalability
--when node mobility is high: ticket-based
Qos-aware routing will scale well.
--when traffic density is high: ticket-based
Qos-aware routing and CEDAR will scale well.
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26. Open Issues in Qos-aware Routing
Bandwidth/delay estimation:
What is the best way to estimate available bandwidth and/or delay to maximize accuracy and minimize overhead for resource estimation?
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27. Open Issues in Qos-aware Routing
Route Discovery:
Which class of routing protocols, reactive or proactive, is better for supporting Qos routing to balance overhead and delay?
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28. Open Issues in Qos-aware Routing
Resource Reservation:
How should in-band signaling be coupled with the routing protocol for resource reservation?
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29. Open Issues in Qos-aware Routing
Route maintenance:
How should the prediction of route breaks, route redundancy, and rerouting optimization be incorporated into a rerouting scheme to balance overhead with Qos performance?
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30. Open Issues in Qos-aware Routing
Cross-layer design:
What types of information should be shared among the layers to best support Qos-aware routing in MANET?
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31. Thanks for your listening!
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