A Grouping Harmony Search Algorithm for Assigning Resources to Users in WCDMA Mobile Networks A. Aybar-Ruiz 1 , L. Cuadra 1 , J. Del Ser 2, 3 , J.A. Portilla-Figueras 1 , and S. Salcedo-Sanz 1 1 Department of Signal Processing and Communications, Universidad de Alcal´ a 28805 Alcal´a de Henares, Madrid, Spain lucas.cuadra@uah.es, WWW home page: https://www.uah.es/es/ 2 University of the Basque Country EHU/UPV, 48013 Bilbao, Spain 3 OPTIMA Area, TECNALIA, 48160 Derio, Bizkaia, Spain. Abstract. This paper explores the feasibility of a particular implemen- tation of a Grouping Harmony Search (GHS) algorithm to assign re- sources (codes, aggregate capacity, power) to users in Wide-band Code Division Multiple Access (WCDMA) networks. We use a problem for- mulation that takes into account a detailed modeling of loads factors, including all the interference terms, which strongly depend on the as- signment to be done. The GHS algorithm aims at minimizing a weighted cost function, which is composed of not only the detailed load factors but also resource utilization ratios (for aggregate capacity, codes, power), and the fraction of users without service. The proposed GHS is based on a particular encoding scheme (suitable for the problem formulation) and tailored Harmony Memory Considering Rate and Pitch Adjusting Rate processes. The experimental work shows that the proposed GHS algorithm exhibits a superior performance than that of the conventional approach, which minimizes only the load factors. Keywords: Harmony Search, Grouping Harmony Search, Wide-band Code Division Multiple Access mobile networks 1 Introduction Currently about 80% of mobile operators worldwide are investing to upgrade their Wide-band Code Division Multiple Access (WCDMA) networks [1], which have 1.83 billion users. High Speed Packet Access (HSPA), based on WCDMA technology, is the most widely used mobile broadband technology deployed at present. This is because HSPA allows operators to cost-efficiently upgrade their already deployed WCDMA networks to provide both speech and broadband data services (high speed Internet access, music-on-demand, or TV and video streaming, to name just a few). WCDMA/HSPA technology is expected to serve 90% of the world’s population by 2020, with about 3.8 billion users [1].