Distributed Beamforming Phase Synchronization Algorithms with multiple spatial constraints

In this thesis, we tested performance of two classes of distributed phase synchronization algorithms for distributed beamforming in the presence of multiple spatial constraints. The originality of the work consists in testing performance of the deterministic synchronization with multiple spatial constraints, and comparing it with the random in many different scenario conditions. Thanks to DBF, independent and randomly located sensor in a WSN are able to coordinate their antenna resources to form a virtual array that directs a beam in the desired direction of transmission, thus delivering a common message to a distant receiver. Directional beams facilitate separation of signals in the spatial domain enabling SDMA techniques and increasing throughput. Moreover, DBF allows for reduction of transmitted power of each sensor. At the beginning, we gave an introduction on the basic definitions and relationships that are used to analyze and synthesize arrays. Then, we have introduced the concept of DBF, and in particular we focused our attention on principal phase synchronization schemes proposed in literature. Among all the solutions, we recognized in the One-Bit Feedback algorithm the best solution in terms of semplicity and scalability. This is an iterative protocol: in each time slot, each node applies a phase adjustment to its signal and decides whether to keep or discard the phase shift on the basis of a one bit feedback from the receiver. We have distinguished two different approaches: the random and the deterministic one. The deterministic approach shows to have better performance with respect to the random in terms of convergence speed, both in a single spatial contraint case, and in a multiple spatial constraint case.