Distributed Graph Coloring for Self‐Organization in LTE Networks

Abstract

Primary Component Carrier Selection and Physical Cell ID Assignment are two important self‐configuration problems pertinent to LTE‐Advanced. In this work, we investigate the possibility to solve these problems in a distributive manner using a graph coloring approach. Algorithms based on real‐valued interference pricing of conflicts converge rapidly to a local optimum, whereas algorithms with binary interference pricing have a chance to find a global optimum. We apply both local search algorithms and complete algorithms such as Asynchronous Weak‐Commitment Search. For system level performance evaluation, a picocellular scenario is considered, with indoor base stations in office houses placed in a Manhattan grid. We investigate a growing network, where neighbor cell lists are generated using practical measurement and reporting models. Distributed selection of conflict‐free primary component carriers is shown to converge with 5 or more component carriers, while distributed assignment of confusion‐free physical cell IDs is shown to converge with less than 15 IDs. The results reveal that the use of binary pricing of interference with an attempt to find a global optimum outperforms real‐valued pricing.