Multi-hop wireless networks: Fact or fiction? Konstantinos Psounis EE and CS USC

2 Panel members  To make sure we represent both viewpoints, panel members have been asked to say if they are in favor or against multi-hop  Replies in the order they have arrived:  Anmol Sheth (Intel Research): against, with recommendations on how to make them real  Injong Rhee (NCSU): in favor, but not of the stand-alone island paradigm  Ramakrishna Gummadi (MIT): “Multihop is already there, but true multihop mesh may not be feasible”  Suresh Singh (Portland): “I guess I will go against”

3 A taxonomy of multi-hop networks  Path longevity  the average lifetime of a path in the network  Path availability  the average fraction of time that some path is available between two nodes in the network LowHighSensor networks Low Intermittently connected networks HighLow Mobile ad hoc networks High Mesh networks AvailabilityLongevity

4 Fact or fiction? Mesh networks  Fact: up to 3-hop long paths at the edges of the network for Internet access extension  caveat: not clear it is commercially viable due to bad performance  but: this may very well have to do with the protocols used, e.g. TCP over random access in multi-hop settings is a disaster and multiple directional antennas can improve performance at a small cost  Fiction: many nodes forming a cloud with long paths  note: decades-old point to point wireless multi-hop connections are not mesh networks  To be decided: other real world apps, e.g. home networking, medical apps  note: again, up to 3-hop long paths

5 Fact or fiction?  Mobile ad hoc networks (fully connected)  Fact: _  Fiction! tell me one real application that will operate over a network of mobile nodes that are so many and so dense to guarantee end-to-end connectivity  To be decided: the practical point of all the related research (next slide)

6 Fact or fiction?  Intermittently connected mobile ad hoc networks  mobility-assisted communication  Fact: military applications  To be decided: the future of vehicular, underwater, disaster recovery networks  Fiction: everything else extremely intermittently connected networks: every now and then, there will be contemporaneous end-to-end paths (use of traditional mobile ad hoc network protocols)

7 Fact or fiction?  Sensor networks  Fact: a very small number of industrial applications using wireless sensors  Fiction: large clouds of nodes with long paths taking physical or other type of measurements  To be decided: why all these special NSF calls for wireless sensor networks up to recently

8 Summary  Static multi-hop networks will have short paths  Mobile multi-hop networks will have  to account for intermittent connectivity  very specialized clients, e.g. military  The rest is (probably) fiction

9 The Brain-Brawn Chart Number of PhD degrees Size of Industry segment (e.g. revenue) Cellphones WiFi Sensors MANET Intermittently Conn. Mesh Networks Sensor Networks