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Without a bill a duck couldn’t eat, nor could the employees and shareholders of wireless service providers. The challenges of generating the information required to bill a subscriber in wireless are quite different than in landline systems. While some capabilities are not required – third party billing and collect calling for example – new capabilities are required that have no counterpart in older telecommunications systems – such as roaming and handoff.
There are two different forms of billing in telecommunications systems. While everyone understands the need for a carrier to bill a subscriber, it is also important for carriers to be able to bill other carriers when they provide resources to serve a call being billed by them. This process is known as Settlement, and both Billing and Settlement are supported in wireless systems by the same underlying infrastructure, based on the exchange of CIBER records, as well as various proprietary formats.
CIBER (Cellular Intercarrier Billing Exchange Record) is a collection of record formats that have been used for recording wireless inter-carrier billing or settlement information since 1988. Different formats are used for recording airtime for a local call, airtime and toll for a long distance call, for inter-carrier handoff of one party in a call, and for additional charges that may be incurred (such as the much hated daily roaming fees). The record format is maintained by CIBERNET Corporation, a subsidiary of CTIA. Its structure is primitive compared to more advanced protocols such as TIA/EIA-41 which is used for intersystem operations and TIA/EIA-124, a protocol that can also convey billing records. Yet, perhaps the simplicity of CIBER is one of its advantages and the secret of its longevity. Although it is not often modified, it certainly can be when necessary. The latest modifications came into effect in August, 1999 when support for local number portability, inter-technology roaming and improved support for international roaming were added. Furthermore, it is very important for a billing protocol to be precise, unambiguous and robust. It becomes difficult to have a precise definition of a very complex protocol, and ambiguity often results. TIA/EIA-41, for example, has suffered from this very problem. Robustness flows from the fact that each CIBER record represents a single item for billing or settlement (or both), with no necessity to perform buffering and merging of records. These positive characteristics are not present in the more advanced TIA/EIA-124 standard, and may account for its lack of acceptance.
When a mobile phone is used to place a call in its home system, the MSC (Mobile Switching Center) that is serving the call generates a CDR (Call Detail Record) in a format that is usually proprietary to the manufacturer of the MSC. Traditionally, these records were sent on magnetic tape to a billing system, but increasingly they are being sent over a network. The billing system then can generate a line item or perform other operations (such as decrementing a monthly counter of free minutes) for a subscriber’s next bill.
But life is rarely that simple. One complication could be that the home MSC starts to lose the signal from the mobile and needs to handoff the mobile to a neighboring MSC. In this case, the home MSC will still generate the bill, so billing is not affected. However, the neighbor MSC has provided facilities to serve the call following the handoff, and may expect to be reimbursed. If traffic between two MSCs is relatively symmetrical, it may be simpler and cheaper to use a “Bill and Keep” methodology requiring no settlement, but if traffic is asymmetrical, some form of Settlement will likely be used. In this case the system receiving the handoff generates a CDR, which is sent to its billing system. This generates a CIBER record that indicates the identity of the mobile, the duration of the call and other information, and forwards it to the home MSC’s billing system. Later, the amount of money owed between carriers is settled. Rather than the carriers exchanging large checks, the amounts owed are subtracted, and the company that owes the most reimburses the other for the difference, a process known as Net Settlement, which is also facilitated by CIBERNET Corporation. It is important to note that the process of Settlement is not directly tied to billing, as the amount billed is not changed by the occurrence of an inter-system handoff during the call, and billing may occur before or after settlement.
Another common complication occurs when a mobile roams into a foreign system and is used to make a call. In this case the home MSC is not involved in the call at all. At the end of the call, the visited MSC generates a CDR and sends it to its billing system. This billing system generates a CIBER record and forwards it to the home system. The home system will, as usual, generate the bill, but will now owe the visited system a portion of the revenue generated by the call.
The ability to transmit information is only one aspect of billing. It does not solve the problems of convergence nor bill presentation. It is, however, an essential component. Looking forward, it can be predicted that a technical billing problem that will have to be solved one day is the transfer of CIBER records into other domains, most notably landline telecommunications.
One of the areas where wireless systems are deficient is in the provision of traditional inter-carrier billing, providing services such as third party billing, billing to a calling card and collect calling. While wireline replacement has focused largely on the radio issues, it is necessary for the major landline billing services to be available on wireless systems before wireline replacement can be considered complete. When I recently dropped my two daughters off at the wrong location for a dance concert rehearsal, for example, they had the presence of mind to call home – collect. They would have been unable to call me if a mobile had been my only phone. Providing these services requires crossing the hurdle of wireless/landline billing record exchange. Predictably, wireless systems rely on CIBER records, and landline systems on EMI/EMR records. You have probably guessed that these two formats have very little in common, with many minor, and a few major incompatibilities. Providing transparent billing record exchange will therefore be a major advance for wireless consumers. I certainly look forward to a time when my kids are in college and have the ability to call me from anywhere, at no cost to themselves (not!).
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