ing applications help to track and manage all vital infor- mation about partners of the service provider, partner agreements, products, services, and marketing strategies. This helps to accurately track and timely bill the customer. Interconnect billing also performs cost management and can be used to easily identify rampant costs and route overflows in billing systems. 11. Invoicing: The invoice management solution speeds processing time by auto- mating the bill payment process from receipt to accounts payable. Telecom bills are mostly complex and error prone. This leads to high invoice process- ing costs. Use of an invoice management solution reduces cost per invoicing. Other advantages include a faster invoice approval and collection process. This leads to an increase in efficiency caused by improved financial reporting. Fundamentals of EMS, NMS and OSS/BSS Some of the key features of an invoice management solution are invoice consolidation, invoice auditing, invoice content validation, tracking of invoice, getting approvals, generating intuitive reports, and smooth integra- tion with accounting system. 12. Billing mediation: A billing mediation application collects billing data from multiple sources, filters them, and does formatting and normalization before sending it as a single feed to the billing system. Converged billing mediation solution can collect billing data from IP, fixed, and mobile networks. The activities performed by billing mediation application can be summarized as gather, process, and distribute of usage data. The tasks start with collection and validation of usage records. This is followed by filtering out irrelevant records that are not relevant for billing. Records are then aggregated and correlated to obtain useful information. Finally the usage data is formatted and normalized. Then it is distributed to northbound OSS applications. It should be noted that all data mediated by the billing mediation system is not used by the billing system. For example, some traffic information can also 