Construction of Hyperbolic Signal Sets from the Uniformization of Hyperelliptic Curves
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In this paper, we present a new approach to the problem of designing hyperbolic signal sets matched to groups by use of Whittaker's proposal in the uniformization of hyperelliptic curves via Fuchsian differential equations (FDEs). This systematic process consists of the steps: 1) Obtaining the genus, g, by embedding a discrete memoryless channel (DMC) on a Riemann surface; 2) Select a set of symmetric points in the Poincaré disk to establish the hyperelliptic curve; 3) The Fuchsian group uniformizing region comes by the use of the FDE; 4) Quotients of the FDE linearly independent solutions, give rise to the generators of the associated Fuchsian group. Equivalently, this implies the determination of the decision region (Voronoi region) of a digital signal. Hence, the following results are achieved: 1) from the solutions of the FDE, the Fuchsian group generators are established. Since the vertices of the fundamental polygon are at the boundary of unit disk, its area (largest possible) implies the least symbol error probability as a performance measure of a digital communication system; 2) a relation between the parameters of the tessellation p,q and the degree of the hyperelliptic curve is established. Knowing g, related to the hyperelliptic curve degree, and p, number of sides of the fundamental polygon derived from Whittaker's uniformizing procedure, the value of q is obtained from the Euler characteristic leading to one of the 4g,4g or 4g+2, 2g+1 or 12g-6,3 tessellation. These tessellations are important due to their rich geometric and algebraic structures, both required in classical and quantum coding theory applications.
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