Annual Report 2010 - Fachgruppe Informatik an der RWTH Aachen ...

delegate certain tasks to other devices in the network. Firewalls or digital notary services are
examples for such delegatable tasks. Moreover, (5) service discovery is a crucial supplement
to these communication primitives. We use an indirection-based communication paradigm as
basis for these forms of communication. However, our approach requires a network-wide
lookup service as basis for the indirection functionality. In this project we create a flexible
and robust lookup service that is tailored for the challenging conditions in wireless mesh
networks. The service is distributed amongst all wireless routers and can operate without
centralized components. Therefore, it can be deployed easily without additional server
infrastructure. The ultimate goal of this project is to enable new and flexible ways of
communication in dynamic wireless scenarios without the performance, deployment, and
scalability issues of centralized components.
TinyOS Meets Wireless Mesh Networks
Muhammad Hamad Alizai, Klaus Wehrle
We introduce TinyWifi, a TinyOS platform supporting Linux driven devices. It allows direct
execution of protocol libraries originally developed for a different networking domain.
Applications from highly resource constrained sensornets can easily be compiled for resource
rich Wi-Fi based networks , thereby making the very rich and mature protocolrepository of
TinyOS available for broader wireless research. Using TinyWifi as a TinyOS platform, we
expand the applicability and means of evaluation of wireless protocols originally designed for
sensornets towards inherently similar Linux driven ad hoc and mesh networks.
Enhancing the Quality of VoIP with Cross-Layer-Iterated Soft Information
Florian Schmidt, Klaus Wehrle
Voice over IP (VoIP) has in recent years become a main contender for audio-visual
communications, and its widespread use is anticipated to supplant a sizable amount of
classical telecommunication via phone lines. Of special importance is the use in wireless
devices, and how to improve the quality of communication, from a user point of view in
respect to voice quality as well as from a provider point of view in respect to efficient
communication.
In current systems for wireless IP transmission of audio-visual signal, bit errors on a wireless
link are detected by CRC on the physical layer and erroneous packets are discarded. However,
many voice and video coding schemes make use of error concealment, and therefore prefer
the reception of partially corrupted data to no data at all. Being able to receive partially
corrupted data therefore is a vital point in enhancing the quality of VoIP communication,
especially over wireless links, where bit errors are much more common.
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