A few powerful nodes enhance mobile network connectivity 3




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目 录

通讯与网络

A few powerful nodes enhance mobile network connectivity 3

Chirp signaling offers modulation scheme for underwater communications 5

Enabling smart service delivery in fiber-to-the-home networks 10

Virus boosts nanoparticle memory 12

更大更快更安全 我国下一代互联网达世界领先水平 14

A Bright Future for Spintronics 14

Bringing Light to Silicon 17

Nanowire Computing Made Practical 19

新设计将制造出3兆兆赫芯片 20

Hybrid nanomaterials improve solar cell efficiency 21

Imaging reveals working nanodevices' topology and electronic processes 25

Modeling photoexcited carrier interactions in semiconductor nanostructures 28

Solution processing simplifies the manufacturing of carbon-nanotube transistors 31

Detecting chemical, biological, and explosive agents 34

Formable compound micro-lens arrays 38

Optical microscopy on the Internet 41

Using fluids to manipulate nanoscale optics 45

A boost for solar cells with photon fusion 48

Quantum back-action has a cooling effect 49

Bubbles collapse without weight 51

Quantum encryption sets long-distance record 52

Laser controls chemical reaction rates 53

Physicists make atomic clock breakthrough 55

Conquering delivery-fiber noise in remote sensing 56

Finite-sized water vapor clouds affect interferometry phase corrections 60

Advanced Optimization Technology to Enhance Business Decision Making 64

Coating-Enabled Component Design: Technology Tools for Nanostructures Coatings 65

Security Framework to Exchange Data That Enhances Productivity 67

Extended portable power through innovative integration of energy technologies 68

主办单位:电子科技大学图书馆

编员会:张晓东 黄思芬 汪育健 侯壮 张毓晗 曹学艳

李世兰 刘静 张宇娥 黄崇成 陈茂兴

A few powerful nodes enhance mobile network connectivity 3

Chirp signaling offers modulation scheme for underwater communications 5

Enabling smart service delivery in fiber-to-the-home networks 10

Virus boosts nanoparticle memory 12

更大更快更安全 我国下一代互联网达世界领先水平 14

A Bright Future for Spintronics 14

Bringing Light to Silicon 17

Nanowire Computing Made Practical 19

新设计将制造出3兆兆赫芯片 20

Hybrid nanomaterials improve solar cell efficiency 21

Imaging reveals working nanodevices' topology and electronic processes 25

Modeling photoexcited carrier interactions in semiconductor nanostructures 28

Solution processing simplifies the manufacturing of carbon-nanotube transistors 31

Detecting chemical, biological, and explosive agents 34

Formable compound micro-lens arrays 38

Optical microscopy on the Internet 41

Using fluids to manipulate nanoscale optics 45

A boost for solar cells with photon fusion 48

Quantum back-action has a cooling effect 49

Bubbles collapse without weight 51

Quantum encryption sets long-distance record 52

Laser controls chemical reaction rates 53

Physicists make atomic clock breakthrough 55

Conquering delivery-fiber noise in remote sensing 56

Finite-sized water vapor clouds affect interferometry phase corrections 60

Advanced Optimization Technology to Enhance Business Decision Making 64

Coating-Enabled Component Design: Technology Tools for Nanostructures Coatings 65

Security Framework to Exchange Data That Enhances Productivity 67

Extended portable power through innovative integration of energy technologies 68

A few powerful nodes enhance mobile network connectivity


Xiyu Shi, Christopher Adams, Ahmet Kondoz

Strategically positioned nodes with extra transmission power can maintain system-wide connectivity in ad hoc networks.

A mobile ad hoc network (MANET) is a temporary collection of wireless nodes communicating without the benefit of infrastructure. A connection between two nodes may involve several others in what is known as multi-hop routing. MANET can be used in situations in which, for example, soldiers relay and share information on a battlefield or relief workers coordinate efforts during an emergency.

A basic requirement of a MANET is that it must maintain higher network connectivity, loss of which could entail severe consequences. Therefore, a principal task is to set up a route that connects source and destination nodes. Due to the dynamic shifts in network topology, multi-hop routing is neither stable nor pre-established.

Several different MANET routing protocols have been proposed in recent years,1–4 but research has shown that they are incapable of maintaining high connectivity in the face of diminished node density.5,6 Our simulation7 confirms this. Moreover, the protocols may require bidirectional links such that if node A can receive data from node B, then B can also receive data from A. However, this is not always the case. There might be numerous unidirectional links where node transmission power is affected by interference, building blockages, etc.

Our approach to enhance MANET network connectivity is to employ a few nodes with larger transmission power as strategic or backbone nodes (BN). These help to establish connections between remote nodes that are otherwise unable to connect. In Figure 1, BN1 and BN2 are the strategic nodes with the capacity for mesh connecting with each other. Nodes in the upper area (A, B, and G) are sufficiently far from nodes in the lower area (C, D, E, and F) that no node in the lower area could directly reach any node in the upper area, and vice versa. With the assistance of BN1 and BN2 however, such connections can be established.



Figure 1. In this model of backbone-node (BN)-supported wireless ad hoc networks, nodes A, B, and G connect to C, D, E, and F via BN1 and BN2.

 

Routes are set up as follows: mobile nodes near each other can have direct connections (e.g. C → D), and mobile nodes near BNs but without direct connections can be connected via BNs (e.g. E → BN2 → C → D). Mobile nodes between remote areas can also be connected via BNs (e.g. A → B → BN1 → BN2 → C → D). Thus, whenever a remote mobile node has a request to connect to another node, the BNs function both as normal mobile nodes and also forward connection requests to the desired remote destination node. This implies that the networks can establish more and better routes, and are able to deliver more packets without extra routing overhead.

The effectiveness of this approach in enhancing network connectivity can be proved by simulation in different network configurations, that is, with different node densities, velocities, and transmission power. We used the Java-based scalable wireless ad hoc network simulator (SWANS) to simulate a MANET with IEEE 802.11b medium access control protocol and transmission of UDP traffic. The BNs possess all the properties of normal mobile nodes, but they possess larger transmission power and remain stationary during the simulation. The ad hoc on-demand vector routing (AODV) protocol is used. Two criteria are used to assess network connectivity: the packet delivery ratio (the total number of data packets received over the total number of packets sent by all nodes) and the average path length (the average number of mobile hops a packet takes to reach its destination).

Results show that our approach performs better than the normal MANET in all simulated network scenarios. Performance is significantly improved (see Figure 2) when network node density is lower. In the case of 50 nodes, our approach can deliver more than 89% of packets, an increase of 28% compared with the normal MANET. This is because, without the assistance of BNs, many nodes are out of the reach of each other when the node density is lower. In comparison with the normal network, the average packet length is shorter, with our network consistently establishing routes about one hop less than the normal network in all scenarios.



Figure 2. In comparing packet delivery ratios as a function of node density when nodes are stationary, the network with BNs provides better performance, especially in lower node density situations.

 

High connectivity, extremely important for MANET to be feasible in critical situations, can be greatly enhanced by selecting a few nodes to serve as backbone nodes. This approach is relatively easy to deploy inasmuch as output power of many wireless devices can be custom-configured. It can also be used to improve user or node connectivity in other networks, such as sensor networks and mobile communication systems.



Authors

Xiyu Shi, Ahmet Kondoz

Centre for Communication Systems Research, University of Surrey,Guildford,UK

http://www.ee.surrey.ac.uk/CCSR/

Christopher Adams

Department of Information Systems, University of Buckingham,Buckingham,UK



References:

1. C. Perkins, E. Belding-Royer, S. Das, Ad hoc on-demand distance vector (AODV) routing, IETF RFC, Vol: 3561, 2003.

2. D. Johnson, D. Maltz, Y. Hu, The dynamic source routing protocol for mobile ad hoc networks (DSR), IETF Internet-drafts, 2004.

3. D. B. Johnson, D. A. Maltz, Dynamic source routing in ad hoc wireless networks, Mobile Computing, pp. 153-181, 1996.

4. Z. Haas, M. Pearlman, P. Samar, The zone routing protocol (ZRP) for ad hoc networks, IETF Internet-drafts, draft-ietf-manet-zone-zrp-04.txt, 2002.

5. J. Broch, D. A. Maltz, D. B. Johnson, Y. C. Hu, J. Jetcheva, A performance comparison of multi-hop wireless ad hoc network routing protocols, Proc. Fourth Annual ACM/IEEE Int. Conference on Mobile Computing and Networking (MobiCom'98), 1998.

6. B. Freisleben, R. Jansen, Analysis of routing protocols for ad hoc networks of mobile commuters, Proc. of the 15th IASTED International Conference on Applied Informatics, 1997.

7. X. Shi, F. Li, C. Adams, The impact of backbone nodes on MANET routing performance, Proc. of the Multi-Service Networks 2005 Conference, 2005.

DOI: 10.1117/2.1200608.0360

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