Towards proliferation of ad hoc wireless networks

1. Towards proliferation of ad hoc wireless networks P. R. Kumar (with V. Borkar, G. Baliga, S. Graham, P. Gupta, K. Huang, V. Kawadia, S. Narayanaswamy, V. Raghunathan, R. Rozovsky, L-L. Xie) Dept. of Electrical and Computer Engineering, and Coordinated Science Lab University of Illinois, Urbana-Champaign

2. One modest effort-in-the-making towards proliferation How to proliferate ad hoc networks? We don�t know what the �killer� applications are Much genius in society Applications will emerge Great hunger for communication Instant Messenger Our attempt in the making: Idea Develop a product Give it away free See what happens Have developed software which will self-install Addresses, routing, anonymity Linux and Windows Have not yet developed a distributed chat application How to spark adoption? A �business model� for giving it away free

3. Another vision: Interaction with world What are the right abstractions? What should be the architecture of the system? Application independent, Context independent architecture Same architecture for Building-wide temperaturecontrol system?

4. The importance of architecture Success of Internet is due to its architecture Notion of peer-to-peer protocols Hierarchy of layers Allows plug-and-play Proliferation of technology

5. Middleware: EtherArch Software Time translation Knowledge of per-packet delay important for control Location independence Car can request for a camera covering coordinates(50,50) - Infrastructure finds the corresponding camera Car need not know the IP address or port System startup and evolution during execution Installing application code components at start-up/run-time Automatic migration of components to reduce communication or computation burden

6. Information TechnologyConvergence Lab:The Systems

7. IT Convergence Lab Movie

8. Ad Hoc Wireless Networks Ad Hoc Networks Current proposal for operation: Multi-hop transport Nodes relay packets until they reach their destinations Fully decode packets at each stage treating allinterference as noise

9. However wireless networks are not wired networks � Wireless networks are formed by nodes with radios There is no a priori notion of �links� Nodes simply radiate energy

10. Nevertheless the good news is � Multi-hop is nearly optimal Transport packets over manyhops of distance Nearly optimal multi-hop architecture

11. The Power Control problem How do we choose power levels of transmissions in wireless networks? Power level influences range Power levels determine interference Power levels affect routes Conceptualization problem for Power Control Which Layer? Physical layer Quality of reception Network layer Impact on routing Transport layer Higher power impacts congestion How to fit Power Control in the hierarchical OSI framework?

12. Our own suggestion: Network Layer solution for Power Control Power Control has global impact Connectivity is a global property Clustering is regional Routing is over network Interdependence of Power Control and Routing  So joint solution for Power Control and Routing situated at the Network Layer

13. Can we develop a better second generation higher performance MAC? IEEE 802.11 MAC Silences two neighborhoods Real as well as virtual carrier sensing Backoff counters PLCP header at low rate  Our own attempt: SEEDEX Based on exchanging pseudo-randomnumber seeds to coordinate schedules Reservations without making reservations Silences only one neighborhood No backoff counters But is a slotted protocol Slot synchronization needed

14. Additional functionalities of routing Forwarding Delivering packets to the right destination Load adaptation Can we design an adaptive distributed asynchronousrouting algorithm that adapts routes To the topology of the network To the prevailing traffic conditions, e.g., is delay adaptive? Load balancing How to distribute the loading on different areas of the network Our own attempt: Wardrop algorithm All used paths have same delay All unused paths have larger delay

15. Last but not least Hardware That we can develop on That gives enough interfaces that we can write software That we can experiment with That will spark proliferation A la IEEE 802.11

16. To obtain papers Papers can be downloaded from http://black.csl.uiuc.edu/~prkumar For hard copies send email to prkumar@uiuc.edu

17. Some thoughts on Mesh Networks

18. Some preliminaries on accessing a base-station Multiple-access channel  Capacity region is completely characterized All rate vectors satisfying for some distribution are feasible

19. Optimal strategy vs. TDMA Optimal strategy Successive subtraction and decoding strategy Decode one user Subtract that user�s signal if channel known Decode next user � Requires multi-user decoding Optimal capacity per user is On the other hand simple TDMA can yield Every user simply transmits directly to base-station

20. So what are the issues in multi-hopping to a base-station? Protocol issues Power control can be used to Save energy at mobile nodes Trade-off between energy and delay Medium access issues may get complicates If power control gets sophisticated Routing may be simplified if there is only one sink Transport level may need design due to need for interfacing multi-hop wireless with wired Internet Interesting cross-layer design issues Power control, medium access, routing, transport Further interesting issues when allowing operation in ad hoc as well as just reaching base-station