Wireless Pers Commun (2013) 71:589–610 DOI 10.1007/s11277-012-0832-y Ergodic Sum Rate Maximization for Underlay Spectrum Sharing with Heterogeneous Traffic Mina Dashti · Paeiz Azmi · Keivan Navaie · S. Mohammad Razavizadeh Published online: 19 September 2012 © Springer Science+Business Media, LLC. 2012 Abstract A radio resource allocation framework is proposed for underlay spectrum shar- ing. The ergodic capacity maximization problem in orthogonal frequency division multiple access-based network on point to multi point transmission is formulated and solved. Hetero- geneous traffic is also considered in which two types of traffic is assumed: streaming traffic which has strict delay requirements, and elastic traffic with flexible delay requirements. Considering the effect of channel state information (CSI) imperfection in the evaluation of the secondary users’ expected rate, we further assume that the estimated CSI between the secondary users and secondary base station (secondary channel) is not perfect. Moreover three different cases are considered depending on the availability of the CSI between the secondary base station and the primary receivers (interference channel). Using simulations, we evaluate the impact of streaming traffic and imperfect CSI on the sum capacity of the secondary elastic users for different values of parameter systems. Keywords Elastic traffic · Streaming traffic · Resource allocation · Underlay spectrum sharing · Cognitive radio 1 Introduction Spectrum sharing with cognitive radio (CR) technology aims to combat scarcity in radio spec- trum that has emerged as a result of increased demand for anytime anywhere connectivity M. Dashti (B ) Department of Electrical Engineering, East Tehran Branch, Islamic Azad University, Tehran, Iran e-mail: dashtimina@ieee.org P. Azmi Electrical and Computer Engineering Department, Tarbiat Modares University, Tehran, Iran K. Navaie School of Electronic and Electrical Engineering, University of Leeds, Leeds, UK S. M. Razavizadeh Department of Electrical Engineering, Iran University of Science and Technology, Tehran, Iran 123