Advanced Metering Infrastructures (AMI) are going to represent the backbone of all the Smart City projects where metering and other public services are supposed to be smart. The scenario proposed by OPEN METER project is taking shape in some urban areas where smart meters, concentrators and central access systems have been experiencing. In this paper some topics concerning the use of DLMS-COSEM (Device Language Message specification-Companion Specification for Energy Metering) protocol on a 169 MHz gateway network based on WM-bus for collecting and manage data coming from smart meters and other electronic devices are discussed by the authors. In particular, an innovative solution for water metering and the architecture of a data Central Access System, are described in detail.