Effectiveness of the 2-hop Routing Strategy in MANETS Michele Garetto – Università di Torino, Italy Paolo Giaccone - Politecnico di Torino, Italy Emilio Leonardi – Politecnico di Torino, Italy Tuesday, 15 January 2019

Outline Introduction and motivation Experimental traces Analysis of the Two-Hops forwarding scheme

Introduction The sad Gupta-Kumar result: In static ad hoc wireless networks with n nodes, the per-node throughput behaves as P. Gupta, P.R. Kumar, The capacity of wireless networks, IEEE Trans. on Information Theory, March 2000   

Introduction The happy Grossglauser-Tse result: In mobile ad hoc wireless networks with n nodes, the per-node throughput remains constant M. Grossglauser and D. Tse, Mobility Increases the Capacity of Ad Hoc Wireless Networks, IEEE/ACM Trans. on Networking, August 2002

Introduction Node mobility can be exploited to carry data across the network Store-carry-forward communication scheme S R D Drawback: large delays (minutes/hours) Delay-tolerant networking

Mobile Ad Hoc (Delay Tolerant) Networks Have recently attracted a lot of attention Examples pocket switched networks (e.g., iMotes) vehicular networks (e.g., buses, taxi) sensor networks (e.g., disaster-relief networks, wildlife tracking) Internet access to remote villages (e.g., IP over usb over motorbike)

The impact of mobility In their original paper, Grossglauser and Tse assume that the mobility pattern of each node produces a uniform distribution of node presence over the network area results have later been extended to a restricted mobility model in which each node moves over a random great circle on the sphere Per-node throughput is still ! S. Diggavi, M. Grossglauser, and D. Tse, Even One-Dimensional Mobility Increases Ad Hoc Wireless Capacity, IEEE Trans. on Information Theory, November 2005

Outline Introduction and motivation Experimental traces Analysis of the Two-Hops forwarding scheme

DieselNet-Umass experiment 30 buses running the campus transport service in Spring 2005 (60 days) traces provide the amount of data transferred through TCP connections using WLAN 802.11 MAC access mij measured in bytes

Infocom2005-iMotes experiment iMotes carried by 41 volunteers attending the conference (5 days) traces provide the radio contact duration between any two iMotes using Bluetooth MAC 802.15 access mij measured in seconds

Experimental traces Virtual capacities are directly measured for each pair of nodes (i,j) contact graph: a capacitated graph in which each vertex corresponds to a mobile node edge (i,j) is weighted by The maximum throughput is computed by solving a standard multi-commodity flow problem (for a given flow assignment)

Experimental contact graphs “minDC” flow assignment “MaxDC” flow assignment class 1 class 2 class 3 class 4 capacity x 10x 100x significant asymmetries and inhomogeneous capacities few edges contribute most of the capacity: class 3-4 contribute for 80% (Umass) and 60% (iMotes) of the overall transport capacity

Theoretical performance of experimental networks Traffic scenario Maximum aggregate capacity Average number of hops Umass mDC 21.131 Gbytes 2.31 Umass MDC 28.578 Gbytes 1.85 iMotes mDC 1.756 Msec 2.60 iMotes MDC 3.008 Msec 1.69 Probability Number of hops

Outline Introduction and motivation Experimental traces Analysis of the Two-Hops forwarding scheme

Analysis in Heterogeneous Nets. Consider a MANET whose contact graph is a full mesh topology with capacities inhomogeneous capacity Capacity of the archs are i.i.d random variables μij with distribiution g(x)

Maximum Throughput Consider a source destination pair (s,d) The maximum throughput can be easily evaluated appling the famous max-flow min-cut theorem Being μ= (n-1)E[μij]

2 Hops throughput The througput provided by 2-hops forwarding strategy: Being μmin=(n-1)E[min(μsi μid)}]

Comparison g(x) ≈exp (1) the efficiency of two-hops forwarding scheme is ½ g(x) ≈pareto(a,b) the efficiency of two-hops forwarding scheme is 2(b-1)(2b-1) Going to 0 for b →1.

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