1. A charging system for a communication system, the charging system comprising: a plurality of network elements of a fixed network of the communication system; a plurality of user equipments of the communication system, at least some of the plurality of network elements and the plurality of user equipments comprising a charging proxy; and a charging server comprising: a topic controller for initializing charging topics, each charging topic being associable with charging data, a publication controller for, for each of the charging topics, registering proxies of the charging proxies as publishing proxies, a subscription controller for, for each of the charging topics, registering proxies of the charging proxies as subscribing proxies, a receiver for receiving charging data messages from proxies, a charging data receiver for validating a first set of charging data belonging to a first charging topic in response to a first set of charging proxies registered as publishing proxies for the first charging topic, and a transmitter for transmitting the first set of charging data to a second set of charging proxies registered as subscribing proxies for the first charging topic.