WiMax Operator's Manual

150 CHAPTER 6 ■ BEYOND ACCESS
use today consist of hundreds of strands of optical fiber, each capable of carrying more than
100 frequencies of light. Each frequency in turn can convey minimally 10Gbps or as much as
40Gbps. Thus, total capacity is in the terabits. Such lines are generally the province of long distance
or inter-LATA (which stands for Local Access Transport Area) carriers, as they’re known
in the business, which form the second or third rank in the greater telecommunications hierarchy
depending on whether one designates metro or regional rings as a separate stratum.
At the top of the hierarchy are companies such as Tyco Telecommunications and Global
Crossing, which command international and transoceanic fiber. These companies came to
prominence during the late 1980s and through the 1990s. The submarine cables they utilize are
typically of very large capacity, equivalent to that of the largest continental long lines, and are
designed to provide years of maintenance-free operation.
This neat and somewhat idealized hierarchy has been considerably confused by the emergence
of the Internet, however, as I will explain in the next section. But before that, I will cover
the role that this first hierarchy, the PSTN, will play in the business of the broadband wireless
service provider.
If one wants to provide voice telephony services, even IP voice services, then one must in
most cases either link up with a central office class 5 telephone switch via a device known as an
IP voice gateway or purchase a class 5 switch of one’s own. This is because ultimately the call is
going to a telephone number somewhere else, not to an IP address. This means that the broadband
wireless operator will have to form a relationship either with the incumbent telephone
carrier or with a facilities-based competitive local exchange (CLEC) such as a cable operator
that happens to own a class 5 switch.
In fact, a number of long-distance services use IP as a transport, but, ironically, most of
them also utilize gateways to translate the voice traffic back into circuit form. It is possible to
transmit a call end to end to an ordinary telephone deskset entirely over IP networks, but it is
not the norm today. One would have to establish a special relationship with a long-distance IP
voice service to do so.
Incumbent telcos have offered access to the larger PSTN at a price to other local service
providers for a long time; two-way radio dispatch services are a prime example. If the number
of voice customers in one’s network is small, simply leasing a single T1 back to the incumbent’s
central office may suffice.
In the case of voice telephony services, one always must be concerned with being
beholden to one’s competitor, and any arrangement with an incumbent local exchange (ILEC)
or even a CLEC tends to put one in that position. One possible solution, at least in the case
of facilities-based CLECs, is to attempt to make the relationship synergistic. Some cable operators,
for instance, are starting to view wireless broadband as a means of reaching certain
customers for data services who are not passed by cable currently and cannot be costeffectively
served by this means. Independent mobile operators are another possibility since
they invariably own class 5 switches. A relationship in which the broadband wireless operator
provides access to such customers under some revenue-sharing arrangement in return for a
connection to a class 5 switch at a reasonable rate could be advantageous to both parties.
The Public Internet: The Second Hierarchy
The Internet, as you have seen, is built largely on basic telecommunications infrastructure. All,
or almost all, signals pass over the same basic physical infrastructure of last-mile twisted-pair
copper and metro and long-haul fiber as do voice calls, but once onto long-haul fiber or, in