Synchronization in Distributed Wireless Networks

Wireless Relay Network
Wireless communication systems utilizing multiple antennas promise to allow for vastly increased data rates compared to SISO systems. In a rich scattering environment Multiple Input/Multiple Output (MIMO) systems already achieve an unprecedented spectral efficiency. In addition to conventional MIMO systems, Distributed Antenna Systems (DAS) employ multiple antennas, which are not colocated at one site.

In any practical wireless communication system a crucial issue largely affecting the performance is the synchronization of all active nodes. This becomes an increasingly difficult task the more independent nodes participate in the transmission scheme. Another item influencing the synchronization effort that has to be spent is the quality of the time and frequency reference in any node. Therefore, synchronization algorithms which have to find a tradeoff between complexity and accuracy are a crucial part of any wireless network.

We distinguish between time and frequency synchronization. Time synchronization has to be performed on a frame base as well as on chip level, depending on the application. It is crucial for any time based transmission scheme like Time Division Duplexing (TDD) or Time Division Multiple Access (TDMA). On the other hand, frequency synchronization is a critical factor for OFDM (Orthogonal Frequency Division Multiplexing) and multi-carrier CDMA (Code Division Multiple Access) systems. Coherent transmission schemes rely on an accurate phase synchronization. This is another important item within the scope of the thesis. Certainly, any real world communication system has to synchronize in both, time and frequency domain, to a certain extend.

The scope of this work is the analysis of different algorithms performing time, frequency, and phase synchronization in modern wireless communication systems. A comparison investigating the former mentioned tradeoff between complexity and accuracy will also be of great value. MATLAB simulations will finally evaluate the algorithms and form a basis for future work on this topic.

Subject area Wireless networks, synchronization algorithms and implementation
Type of work 50% Theory, and 50% Simulations
Supervisor Dr. Stefan Berger
Professor Prof. Dr. Armin Wittneben