Synchronization of Cooperative Base Stations
Source: Nokia Siemens Networks
The authors consider synchronization techniques required to enhance the cellular network capacity using base station cooperation. In the physical layer, local oscillators are disciplined by the Global Positioning System (GPS) and over the backbone network for outdoor and indoor base stations, respectively. In the Medium Access Control (MAC) layer, the data flow can be synchronized by two approaches. The first approach uses so-called time stamps. The data flow through the user plane and through copies of it in each cooperative base station is synchronized using a timing protocol on the interconnects between the base stations. The second approach adds mapping information to the data after the user plane processing is almost finalized.