Interference-Aware QoS OLSR for Mobile Ad-hoc Network Routing SAWN 2005, May 24 P. Minet & D-Q. Nguyen

SAWN 2005May 24, Outline 1. Introduction 2. QoS framework for ad-hoc networks 3. Interference-aware QoS OLSR 4. Performance evaluation 5. Conclusion

SAWN 2005May 24, Introduction Transmissions and receptions in ad-hoc networks are subject to radio interference. => Bandwidth resource is affected.

SAWN 2005May 24, Introduction Ad-hoc networks have scarce resources. => QoS management in ad-hoc networks is more difficult than in wired networks. Admission control is needed.

SAWN 2005May 24, QoS framework Class 2 Bandwidth Control and Reservation Application (Bandwidth) Path Computation MAC layer metrics QoS Advertisements

SAWN 2005May 24, QoS framework Application (Bandwidth) Routing on the Reserved Path Class 2 Marking

SAWN 2005May 24, Interference-aware QoS OLSR QoS signalisation Measure local available bandwidth (LAB) At each node. Based on values obtained from MAC layer. LAB dissemination Any node broadcasts in Hello message : its LAB and the LAB of each neighbor. Any MPR (multipoint relay) broadcasts in TC message the LAB of each MPR selector. MPR selection based on LAB Any node selects its MPRs so that it can reach any two-hop neighbor by a largest path; i.e. path with maximum bandwidth.

SAWN 2005May 24, Interference-aware QoS OLSR i mn xyz 5 1 N1(i) = {m, n} N2(i) = {x, y, z} OLSR native MPR selectionMPR selection with bandwidth MPR selection example :

SAWN 2005May 24, Interference-aware QoS OLSR Interference-aware admission control Accept a new flow iff: QoS required by this flow can be met. QoS of already accepted flows must not be altered. Perform in 2 steps: Step 1: Selection of an acceptable path Any node on the path must provide the amount of bandwidth required by the new flow. Can be checked locally by the source node. Step 2: Path feasibility with interferences Any node in the interference zone of a node on the path must have enough bandwidth to support this new flow. A message is sent from source to destination.

SAWN 2005May 24, Interference-aware QoS OLSR Admission control example : S D S D This path for the Yellow flow is not acceptable!

SAWN 2005May 24, Interference-aware QoS OLSR Interference-aware QoS routing algorithm The shortest routes tend to minimize network resources required for transmission of each packet from its source to destination in a wireless multihop environment. => Minimize the number of hops as first criterion. Some flows require bandwidth as QoS parameter. => Consider local available bandwidth at each node as second criterion. Route computation is called upon any topology change. => Complexity must be similar to Dijkstra algorithm. Network resources is scarce. => Algorithm is based on partial knowledge of topology.

SAWN 2005May 24, Interference-aware QoS OLSR Interference-aware QoS routing algorithm Algorithm 1: Default algorithm used to compute routing table. Unconstrained, widest-shortest path. Called upon any change in the one-hop neighborhood, two-hop neighborhood or topology table. Algorithm 2: Constrained by a bandwidth request. Used to compute a route offering the requested bandwidth from a source to a destination if the default route, from algorithm 1, cannot provide that bandwidth. Called by the admission control for a new flow with bandwidth demand.

SAWN 2005May 24, Interference-aware QoS OLSR Admission control example with routing algorithm 2 : S D S D Flow Yellow acceptable!

SAWN 2005May 24, Performance evaluation Simulation plan 250 static nodes uniformly located on a 2500x2500m 2 square. 7 CBR flows, each requires 175Kbps at application level. MAC b, no RTS/CTS. Native OLSR and Interference-aware QoS OLSR routing.

SAWN 2005May 24, Performance evaluation Results obtained with native OLSR

SAWN 2005May 24, Performance evaluation Results obtained with Inteference-aware QoS OLSR routing

SAWN 2005May 24, Performance evaluation Loss rate comparison

SAWN 2005May 24, Conclusion Interference-aware routing can accept more flows into the network. It offers better stability to the accepted flows, better bandwidth guarantee to the applications than native OLSR. If it cannot find a route meeting the bandwidth requested, then such a route does not exist. Main drawback: more MPRs selected => more control overhead, broadcasting using MPR becomes less efficient. Perspective: Reduce control overhead, improve broadcasting.