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A Practical Approach to QoS Routing for Wireless Networks Teresa Tung, Zhanfeng Jia, Jean Walrand WiOpt 2005—Riva Del Garda Outline • • • • Problem: clustering Assumptions: routing algorithm Analysis: simple models Analysis: simulations Scenario Routing over ad-hoc wireless networks Goal: Discover the diverse paths • Small area, use shortest path • Uniform demand, shortest path admits most flows • Demand between few s-d pairs, use diverse paths to increase capacity Observation on Interference • Interference – Area effect – Not a link effect • Routing choices – Over areas – Not over links Tx Intfx Related Work Theoretical Approach • Gupta Kumar • Thiran Practical • Fixed transmission radius • Routing algorithms Clustering: Motivation Clustering makes sense for dense networks Each node sees roughly the same info Clustering: Motivation Clustering makes sense for dense networks Each node sees roughly the same info Clustering: Motivation Clustering makes sense for dense networks Each node sees roughly the same info Clustering: Motivation Clustering makes sense for dense networks Each node sees roughly the same info Costs • Cost of flat routing – No point in all nodes reporting – Reduction in control messages – Limited loss of information • Cost of clustering – Restrict possible paths – Use more network resources Outline • • • • Problem: clustering Assumptions: routing algorithm Analysis: simple models Analysis: simulations Routing granularity • Comparison of routing strategies over a flat network shows little improvement • Scheme – – – – Shortest path within clusters OSPF at the cluster level Measurement Admission Control Routing Source Dest Routing Routing: Measurement Measure the available resources in a cluster • Use a representative node per cluster • Given the link speed • Measure the fraction of time that the channel is busy – Transmitting/Receiving – Channel busy • The fraction of idle time x link speed gives an upper bound on residual capacity Routing: Admission Control For inelastic flows require a rate F • Trial flow of same rate F for period t • Trial packets served with lower priority • Admit if all trial packets received • Otherwise busy Admitted Trial high 802.11e Routing Assumptions • • • • Shortest path within clusters Resource estimates via measurements OSPF based scheme at the cluster level Admission control Outline • • • • Problem: clustering Assumptions: routing algorithm Analysis: simple models Analysis: simulations Clustering: Analysis Model • • • • Continuous plane (dense network) Compare routes over an idle network Grid clustered Compare – Length – Self interference – Diversity Clustering: Length Compare # hops Path length: grid size Path length: grid = 2r Clustering: Self-Interference • Unit disk model, interference radius • Self-interference for shortest path Clustering: Self-Interference Midpoint on II – From II – From I and III each Decreasing in grid size Clustering: path diversity Cost of Flat Routing • • • • N nodes over area A=ar x ar where r tx radius C=(a/g)^2 clusters of size gr x gr Average hops between nodes L Average hops across cluster < gsqrt2 • Flat routing LN2 • Clustered routing (gc1+c2L)C2 Outline • • • • Problem: clustering Assumptions: routing algorithm Analysis: simple models Analysis: simulations Outline • • • • Problem Argument for clustering Routing scheme Simulation results Simulations • Matlab Algorithms • Global OSPF • Event driven OSPF • Event+clustered OSPF 100 nodes, vary density • Mesh topology (5x5) • Random topology (3x3,4x4) Clustering: Shortest Path Simulations: Admission Ratio Mesh over a 5x5 Grid Random over a 3x3 Grid Simulations: Max capacity s-d Mesh over a 5x5 Grid Random over a 3x3 Grid Simulations: Average path length Mesh over a 5x5 Grid Random over a 3x3 Grid Simulations: Path length for fixed s-d pair Simulations: Path Diversity Simulations: ave # routes s-d Mesh over a 5x5 Grid Random over a 3x3 Grid Conclusion Cost of clustering: 20% loss in admit ratio • Path length • Self-interference • Path diversity www-inst.eecs.berkeley.edu/~teresat [email protected]
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