Hidden Differences in Cellular Downlink Scheduling Revealed Across Vendors and Networks

CNS researchers, together with collaborators from Princeton University, will present new work at the Passive and Active Measurement (PAM) Conference, held March 23–25, 2026, examining how cellular base stations make downlink scheduling decisions in practice. The paper, Different Policies for Different NodeBs: Comparing Downlink Schedulers in Cellular Base Stations, presents the first head-to-head comparison of proprietary downlink schedulers across four major base station vendors—Ericsson, Samsung, Nokia, and Huawei—operating on networks from AT&T, Verizon, T-Mobile, and Vodafone.

Based on 500 GB of downlink transfers collected across 20 base stations in five cities, the study reveals significant differences in how schedulers allocate radio resources, control transmission rates, and manage users with unequal channel quality. These findings demonstrate that downlink scheduling behavior is far from uniform, challenging common assumptions used in prior cellular performance measurement studies and offering new insights into how real-world cellular networks operate.