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Ad hoc networks – design and performance issues

This Master's thesis by Juan Francisco Redondo Antón explores the complexities of Ad Hoc Networks (AHNs), detailing their features, applications, and performance challenges. It examines capacity bounds, medium access control, routing strategies, and power control management. The work includes simulations to assess quality of service, highlighting the importance of traffic patterns, node mobility, and transmission range on network performance. Future research directions are also suggested, aiming to optimize the efficiency of AHNs in various scenarios.

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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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