An electron-emitting photocathode includes a base and a large number of projecting elements such as microscopic wires projecting from a surface of the base. Data from the first primary data cache is stored in a first secondary data cache, and data from the second primary data cache is stored in a second secondary data cache. The serving base station then provides a handover notification to a target base station, wherein the handover notification comprises a QoS parameter associated with the service.