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Ad hoc networks – design and performance issues

Ad hoc networks – design and performance issues. Juan Francisco Redondo Antón. Master’s Thesis: HUT, Networking Laboratory. Supervisor: Professor Jorma Virtamo. Espoo, May the 28 th 2002. Contents. Ad hoc networks: features and applications Capacity: bounds and parameters involved

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Ad hoc networks – design and performance issues

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  1. Ad hoc networks – design and performance issues Juan Francisco Redondo Antón Master’s Thesis: HUT, Networking Laboratory Supervisor: Professor Jorma Virtamo Espoo, May the 28th 2002

  2. Contents • Ad hoc networks: features and applications • Capacity: bounds and parameters involved • Medium Access Control • Routing • Simulations • Power control management • Quality of Service • Conclusions / Future work

  3. AHNs: features and applications Why Ad Hoc Networks (AHNs) ? What are they useful for ? • Conferences and meetings • Home environment communications • Emergency search and rescue • Battlefield • Sensors networkswith different purposes • (militar, environmental, traffic • sensor networks…) • Fast installation • Dynamic topology • Flexibility • Connectivity • Mobility • Cost • Spectrum reuse possibility

  4. Theoretical • Experimental • Bounds on capacity • Paramaters that can modify capacity: • Traffic pattern • Location and mobility of nodes • Range of transmission • Need of common range • Constraints on range: connectivity and throughput • Critical transmission range: • Theoretical values • Possible implementations • MAC protocols • Locality of traffic pattern • Effects of relaying • Multipacket reception Capacity of AHNs

  5. Capacity of AHNs Bounds on Capacity of Ad Hoc Networks: • Capacity of wireless networks • 2 models of interference • 2 hypotheses for the network: random and arbitrary networks • Physical model • Protocol model Random network Arbitrary network Reasons?? Protocol model of interference • An experimental scaling law for ad hoc networks

  6. Capacity of AHNs Parameters affecting capacity in AHNs Traffic Pattern • MAC protocols • Locality of traffic pattern: [52] uses a power law distribution of the distances to the destinations to show that - Random traffic pattern is the worst possible - if  < -2, Cn remains aprox. constant if large enough networks • Effects of relaying: m pure relaying nodes increase capacity like • Multipacket reception (MPR): - [60] indicates that the use of MPR improves the coefficient of the asymptotic scaling law of AHNs. - The contribution of MPR is better with high connectivity - Multipacket transmission (MPT) can also be used - Some MAC protocols uses MPR: RCT, MQSR…

  7. Capacity of AHNs Parameters affecting capacity in AHNs Location and mobility Grossglauser and Tse work [58] uses mobility to offer multiuser diversity for the relaying of packets in AHNs • It is an attempt to facilitate local transmissions • with high probability • Independent movements can attain average • long-term constant source-destination throughput • - Only useful for asynchronous applications

  8. Capacity of AHNs Parameters affecting capacity in AHNs Range of transmission • Need of a common range due to the necessity of bidirectional links for ACKs and handshake. • Connectivity and throughput tradeoffs: - Value of the area and the spatial reuse - Maximum number of simultaneous transmission-receptions

  9. Capacity of AHNs Parameters affecting capacity in AHNs Range of transmission • Theoretical critical power: • Practical implementations: • COMPOW: a modular solution • An algorithm based on graph calculation

  10. MAC in AHNs The Medium Access Control Layer in Ad Hoc Networks • Constraints of wireless medium • Transmission technologies: infrared, microwave, spread spectrum • Properties of MAC protocols for AHNs • Proposals: • General for Wireless Networks: • IEEE 802.11 • HiperLAN • Bluetooth • Specific for Ad Hoc Networks: • CSMA • MACA • … • SEEDEX

  11. Routing in AHNs • Expected properties: • Decentralized execution • Loop free • Adaptable to topology changes • Flexible with traffic patterns • Scalable • Bandwidth efficient • Power conservative • Network security • Quality of service support • Metrics: • End-to-end data throughput • Delay • Route acquisition time • Percentage out-of-order delivery • Efficiency • Other metrics • On-demand vs. Table-driven: AODV / DSR — DSDV • Hybrid schemes as ZRP seems to be the solution for scalability • Protocols designed for high mobility: DREAM, LAR, B-Protocol

  12. Simulations of connectivity Connectivity and range of transmission • Our goal is estimating the probability of having a fully connected network • as a function of the transmission range Probability of fully connected network Range of transmission

  13. Power control in AHNs A power-conservative design affects every network layer: • PHY: Quality of reception • Design of HW in wireless interfaces • Logical Link Control (LLC): accommodating error control schemes to • Application Layer: SW implementation • Traffic requirements • Channel conditions • MAC: • IEEE 802.11: allows nodes to sleep temporally through synchronization processes • DBTMA-Enhanced: uses a “busy tones” channel to manage power control • PCMA: extents the handshake procedure to incorporate power-control information • PAMAS: avoids overhearing of the channel to save power • Power-aware routing: • “Energy as a metric” is the crux of the matter • Solutions: • GAF: uses geographic information to make the nodes coordinate themselves to sleep in turns depending on design parameters • SPAN: creates a backbone of nodes that guarantees routing operation while other nodes sleep • LEAR: looks for balanced energy consumption among nodes • Energy/packet • Cost/packet • Time to network partition • Variance in node power levels • Cost/node

  14. Quality of Service in AHNs An ad hoc oriented view of QoS includes: • QoS models defines which are the goals: • IntServ / RSVP • DiffServ • FQMM, a QoS model for AHNs • QoS signaling reserves resources: • dRSVP: adaptive adjustment of the QoS level • INSIGNIA: in-band signaling for AHNs • QoS routing finds the QoS routes: • CEDAR • Ticket-based routing • QoS Medium Access Control must to complete this framework • Support reliable unicast communication • Provide resource reservation

  15. Conclusions / Future work • AHNs are the suitable solution for certain contexts • Capacity is the restraining factor, especially with high number of nodes • Separate analysis of factors impacting capacity provides ideas to increase it • The range of transmission is a critical parameter and has multi-layer influence • MAC problem is open • “Classic” routing protocols are mature • Power control is essential • QoS is an awkward challenge • Integration of network layers Other questions: • Security • Addressing • Commercially available? • Sharing resources

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