Date of Award
Doctor of Philosophy
Electrical & Electronic Engineering
Dr. Dirk Pesch
Prof. Michael Kuhn
Search and Rescue (SAR) missions require robust ad-hoc networks especially in situations where existing wired or cellular networks have been damaged or are not available. Here, a promising SAR communications technology is a Mobile Ad-hoc Networks (MANETs). However, development of systems is challenging due to bandwidth constraints, various application services, high mobility and harsh environments leading to unstable wireless connections.
Throughout this thesis, a prototype of a physical- and link layer is developed which satisfies the criteria for communication services in SAR missions.
This work includes three major contributions:
The first contribution is a single-carrier narrowband physical layer. The transmission chain employs a robust mode for long range communication as well as a mode striving for high spectral efficiency. Channel coding and equalizer algorithms are selected considering both performance and complexity. The resulting frame synchronization algorithm ensures robust burst detection under frequency offset whereas the designed training sequence is also used for estimation of frequency offset, Channel Impulse Response (CIR) and noise variance. Additionally, a hardware implementation verifies the functionality of the transmission chain. Benchmarking the developed transmission chain against the most recent North Atlantic Treaty Organization (NATO) Narrowband Waveform (NBWF) shows that the proposed system reduces Bit Error Rate (BER) and delay of voice transmissions.
The second contribution is an approach which increases the spectral efficiency for multicast communication. It is based on a combination of link adaptation algorithms with an efficient feedback mechanism. This proposed mechanism increases the spectral efficiency by more than 14 times compared to the approach considered in the Narrowband Waveform (NBWF). The same feedback mechanisms can be also applied to provide resource efficient reliable multicast communication.
The third contribution further increases the spectral efficiency of the communication system beyond 14 times of the NBWF approach. At the expense of greater complexity, the physical layer design also supports hierarchical modulation. This approach increases the spectral efficiency not only in unicast communication, but spectral efficiency in multicast communication which incorporates an efficient link adaptation feedback mechanisms is increased by further 12.9%.
Dehm, Mathias, "An Adaptive Physical- and Link Layer for Narrowband Mobile Ad-hoc Networks" (2015). Theses [online].
Available at: https://sword.cit.ie/allthe/487