North American Numbering Plan - Cellular Services and The NANP Numbering Scheme

Cellular Services and The NANP Numbering Scheme

A difference between the NANP system and other plans is that, apart from an obscure, rarely-used area code 600 in Canada, no separate, non-geographical area codes have been created for cellular phones, as is the case in most European and Asian countries, where mobile services are assigned their own prefixes. This means that most North American mobile phones are assigned the same locality-specific codes as landlines, and calls to them are billed at the same rate. Consequently, the "caller pays" pricing model adopted in other countries, in which calls to cellular phones are charged at a higher nationwide rate but incoming mobile calls are not charged to the mobile user, could not be used. Instead, North American cellular telephone users are also generally charged to receive calls as well ("subscriber pays"). In the past, this discouraged mobile users from using the phones or giving out the number. However, robust price competition among carriers has led to dramatic cuts in the average price per minute for contract customers (for both inbound and outbound calls), which can compare favorably to those in caller-pays countries. Most users select bundle pricing plans that include all the minutes they expect to use in a month. Of the four major national carriers in the U.S., three (AT&T, Sprint, and T-Mobile) offer free calling between mobile phones on the carrier's network, and Sprint also offers its customers free calling to mobile phones on other networks.

Some industry observers have blamed "subscriber pays" as one of the main factors in the relatively low mobile phone penetration rate in the United States compared to that of Europe. In this model the convenience of the mobility is charged to the subscriber. Callers from outside the local-calling region of the assigned number, however, pay for a long-distance call, although domestic long distance rates are generally lower than the rates in caller-pays systems. Conversely, an advantage of caller-pays is the relative absence of telemarketing and nuisance calls to mobile numbers. The integrated numbering plan also enables local number portability between fixed and wireless services within a region, allowing users to switch to mobile service while keeping their phone number.

The initial plan for overlays did allow for providing separate area codes for use by mobile phones, faxes, pagers, etc., although these were still assigned to a specific geographical area, rather than the nationwide mobile area codes common to most other countries, and were charged at the same rate as other area codes. Initially, the new area code 917 for New York City was specifically assigned for this purpose within the 5 boroughs; however, a Federal court struck this down and banned the use of an area code for a specific telephony purpose. Since mobile telephony is expanding faster than landline, new area codes typically have a disproportionately large fraction of mobile numbers, although landline and other services rapidly follow and local network portability can blur these distinctions.

The experience of Hurricane Katrina and similar events revealed a possible disadvantage of the methods employed in the geographic assignment of cellular numbers. Many mobile phone users could not be reached, their phones rendered inoperable, even when they were far from the stricken areas, because the routing of calls to their phones depended on equipment in the affected area.

Another related issue for services like mobile telephony is the scarcity of telephone numbers. In contrast to other countries, where mobile and other special-number operators enjoy wide leeway to generate large quantities of telephone numbers, this is not an option in the NANP, with its geographical area codes with a fixed number of digits.