unlikely that circuit-switched billing systems will be able to process a large number of new variables created by GPRS. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Function of GPRS Elements Function of GPRS Elements GPRS call records are generated in the GPRS service nodes. The GGSN and SGSN may not be able to store charging information, but this charging information needs to be processed. The incumbent billing systems are often not able to handle real-time Call Detail Record flows. As such, an interme- diary charging platform is a good idea to perform billing mediation by col- lecting the charging information from the GPRS nodes and preparing it for submission to the billing system. Packet counts are passed to a Charging Gateway Function that generates Call Detail Records that are sent to the billing system. The crucial challenge of billing for GPRS and earning a return on investment (ROI) on GPRS is simplified by the fact that the major GPRS infrastructure vendors all support charging functions as part of their GPRS solutions. Additionally, a wide range of other existing non-GSM packet data networks such as X.25 and Cellular Digital Packet Data (CDPD) are in place along with associated billing systems. It may well be that the cost of measuring packets is greater than their value. The implication is that a per-packet charge will not occur because too many packets are present to count and charge. For example, a single e-mail application can generate tens of thousands of packets regularly. Therefore, the Charging Gateway Function becomes more of a policing function than a charging function. This lends credence to the idea that the network oper- ators may tariff certain amounts of GPRS traffic at a flat rate and then only monitor whether these allocations are exceeded. If excess packets are used, then a value-added charge may occur. This d