Youngtae Kim

New M-Ary Sequence Families With Low Correlation From the Array Structure of Sidelnikov Sequences

In this paper, we extend the construction by Vu and Gong for families of M-ary sequences of period q - 1 from the array structure of an M-ary Sidelnikov sequence of period q2 - 1, where q is a prime power and M|q - 1. The construction now applies to the cases of using any period qd -1 for 3 ≤ d <; (1/2)(√q - (2/√q) + 1) and q > 27. The proposed construction results in a family of M-ary sequences of period q-1 with: 1) the correlation magnitudes, which are upper bounded by (2d -1)√q +1 and 2) the asymptotic size of (M -1)qd-1/d as q increases. We also characterize some subsets of the above of size ~(r - 1)qd-1/d but with a tighter upper bound (2d - 2)√q + 2 on its correlation magnitude. We discuss reducing both time and memory complexities for the practical implementation of such constructions in some special cases. We further give some approximate size of the newly constructed families in general and an exact count when d is a prime power or a product of two distinct primes. The main results of this paper now give more freedom of tradeoff in the design of M-ary sequence family between the family size and the correlation magnitude of the family.

Delaunay Triangulation Based Green Base Station Operation for Self Organizing Network

In order to reduce the energy consumption in the cellular network, green self-organizing network (SON) techniques gain the attention from economical and environmental perspective. We study the base station (BS) turning-off operation that can run without knowing the global knowledge of dynamic traffic distribution in time and space. We propose a green SON framework based on an overlay network using Delaunay triangulation (DT). Specifically, we propose a threshold-based BS off algorithm for reliable and operator-friendly operation. The proposed algorithm can be readily implemented and standard compliant, the existing architecture such as X2 interface can be used with minimal modification. We perform an extensive simulations using a realistic urban BS topology, and the results confirm that the proposed algorithm can significantly reduce the energy consumption, e.g., more than 60%, and the energy-delay trade-off curve is almost close to the optimal one, which can be found by the exhaustive search only.