  This paper studies angle-based sensor network localization (ASNL) in a plane,
which is to determine locations of all sensors in a sensor network, given
locations of partial sensors (called anchors) and angle measurements obtained
in the local coordinate frame of each sensor. Firstly it is shown that a
framework with a non-degenerate bilateration ordering must be angle fixable,
implying that it can be uniquely determined by angles between edges up to
translations, rotations, reflections and uniform scaling. Then ASNL is proved
to have a unique solution if and only if the grounded framework is angle
fixable and anchors are not all collinear. Subsequently, ASNL is solved in
centralized and distributed settings, respectively. The centralized ASNL is
formulated as a rank-constrained semi-definite program (SDP) in either a
noise-free or a noisy scenario, with a decomposition approach proposed to deal
with large-scale ASNL. The distributed protocol for ASNL is designed based on
inter-sensor communications. Graphical conditions for equivalence of the
formulated rank-constrained SDP and a linear SDP, decomposition of the SDP, as
well as the effectiveness of the distributed protocol, are proposed,
respectively. Finally, simulation examples demonstrate our theoretical results.
