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- Bilstrup, Urban, 1971-
(författare)
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Design Space Exploration of Wireless Multihop Networks
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores the feasible design space of wireless multihop networks and identifies fundamental design parameters. In the process of exploring it is important to ignore all details and instead take a holistic view. This means that all protocol details are overseen, all details of radio wave propagation models are overseen and the system is modelled strictly on an architectural level. From a theoretical information perspective, there is a limit to the capacity that a certain bandwidth and a certain signal-to-noise ratio at the receiver can provide. This limit is approximated as a volume in the time-frequency-space domain. A single transmission is represented as an occupied volume in this domain. A wireless multihop network covers a spatial area, and the question is how multiple numbers of transmission volumes can be fit into a given limited spatial area. This volume fitting should be done in order to maximize the overall performance or to trade available resources to favour a specific characteristic in the wireless multihop network. The volume model is used for the design space exploration of a wireless multihop network. It is argued that the fault tolerance and the energy gain achieved in a multihop topology are its strength as compared to a single-hop architecture. It is further shown that the energy gain is achieved at the expense of delay and a greater end-to-end error probability. This indicates that these parameters must be very carefully balanced in order to gain in the global overall performance perspective. It can further be concluded that the overall spatial capacity is increased as a result of the spatial channel reuse in a multihop topology. On the other hand, it is also shown that the multihop topology introduces a rather stringent geometrical capacity limitation when the number of nodes of a wireless multihop network is increased. The dynamics (e.g. node mobility, changing radio channels etc.) of a large scale wireless multihop network is also a limiting factor. The nodes’ mobility creates a knowledge horizon beyond which very little can be known about the present network topology.
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| 2. |
- Agelis, Sacki
(författare)
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Reconfigurable Optical Interconnection Networks for High-Performance Embedded
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In embedded computer and communication system the capacity demand for interconnection networks is increasing continuously in order to achieve high-performance systems. Recent breakthroughs show that by using reconfigurability inside a single chip substantial performance gains can be added. However, in this thesis the focus is on system level reconfigurability (between chips or modules) and the performance gains that potentially can be achieved by having support for runtime reconfigurability on the system level.This thesis addresses the field of runtime system level reconfigurability with the use of optics in switches and routers for data- and telecommunications, and in multi-processor systems used for embedded signal processing. Several reconfigurable systems for switching and routing with support to adapt for asymmetric traffic patterns are proposed and compared to identify how design choices affect flexibility, performance etc. The proposed solutions are characterized by their multistage optical interconnection networks with reconfigurable shuffle patterns, where the reconfigurability is provided by micro-optical-electrical mechanical systems. More specifically, application-specific bottlenecks can be resolved by reconfiguring the interconnection network according to the current application demands. The benefits of the architectural solutions are confirmed by simulations that clearly show that the architectures can achieve high performance for both symmetric application characteristics and for several classes of asymmetric application characteristics. The final architectural solution is characterized by electronic packet-switches interconnected through an optical backplane, which is reconfigurable. Moreover, the thesis presents how several signal processing applications can be mapped to run concurrently in a time-shared scheme on a single reconfigurable multi-processor system that has high flexibility to adapt for the application currently at hand. The interconnection network is then adapted (reconfigured) according to the demands of the currently executed application in each time instance. The analysis shows that it is feasible to build such a system with today’s components.
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