The IEEE 802.16 standards represent the institutionalization of several of the best-performing
technologies in wireless communications and the aggregation of a number of advances made
by various manufacturers that are unavailable in a single platform up to this time. As such, the
new standards-based equipment enables broadband wireless networks to perform at a level
that was unattainable previously and extends the capabilities of wireless access technologies to
permit the penetration of markets where previously wireless broadband was marginal or
simply ineffective.
Broadband wireless is still not the best access technology for all geographical markets or
all market segments within a given geography, but many more customers are potentially
accessible than in the past. It is scarcely an exaggeration to say that the new standards provide
an effective solution to the most severe geographical limitations of traditional broadband wireless
products, though the reach of any given wireless network is still constrained by its location,
and its attractiveness is affected by the presence or absence of competing broadband
technologies.
The most difficult geographical markets for wireless broadband remain large cities, especially
where high-rises predominate in the downtown business district. In the developed world
the largest cities are already fairly well served by fiber for the most part, and fiber, where it is
present, is a formidable competitor. The largest business buildings housing the most desirable
customers will usually have fiber drops of high-speed fiber rings encircling the city core, and
individual subscribers can purchase OC-3 (144Mbps), OC-12 (622Mbps), or, in some cases,
wavelength services (variously 1Gbps or 10Gbps). Generally, such customers are lost to wireless
service providers because the availability (the percentage of time that a link is available to
the user) of the radio airlink will always be less than for fiber, and availability is critically important
to most purchasers of high-bandwidth data services.
Also, you cannot discount the generally unfavorable topography represented by most
large modern metropolises. Millimeter microwave transmissions demand a clear path to the
subscriber terminal, and unless the base station resides on a tower that is considerably higher
than any other structure in the vicinity, many promising buildings are apt to remain out of
reach within the cell radius swept by the base station. Lower-frequency microwave base
stations using non-line-of-sight (NLOS) technology can reach subscribers blocked by a single
structure, but there are clear limits in the ability of even the most intelligent adaptive antenna
array to lock on a reflected signal that has described several reflections off intervening masonry
walls. Whatever part of the spectrum one chooses to inhabit, wireless broadband is hard to
employ in large cities with a lot of tall buildings. (Sometimes a wireless link makes sense,
however, which is covered in later chapters.)
Wireless broadband has been deployed with greater success in smaller cities and suburbs,
both because the markets are less competitive and because the geography is generally more
favorable. The first point is fairly obvious; secondary and tertiary markets are far less likely to
obtain comprehensive fiber builds or even massive DSL deployments because the potential
customer base is relatively small and the cost of installing infrastructure is not commensurately
cheaper. I will qualify the second point, however.
Suburban settings with lower population densities and fewer tall buildings tend to be
friendlier to wireless deployments than dense urban cores simply because there are fewer
obstructions and also because a single base station will often suffice for the whole market’s
footprint. Nevertheless, such environments still present challenges, particularly when millimeter
microwave equipment is used. Indeed, I know of no instance where millimeter wave
equipment has been successfully deployed to serve a residential market in a suburban setting.
Lower-microwave equipment is much better suited to low-density urban and suburban
settings, and thus it will receive more attention in the chapters that follow; however, where
equipment is restricted to line-of-sight connections, a substantial percentage of potential
subscribers will remain inaccessible in a macrocellular (large-cell) network architecture—as
many as 40 percent by some estimates. Advanced NLOS equipment will allow almost any given
customer to be reached, but, depending on the spectrum utilized by the network operator and
the area served by a base station, coverage may still be inadequate because of range and
capacity limitations rather than obstructions. Unquestionably, the new NLOS equipment will
permit the network operator to exploit the available spectrum far more effectively than has
been possible with first-generation equipment with its more or less stringent line-of-sight limitation.
But as the operator strives to enlist ever-greater numbers of subscribers, the other,
harder limitations of distance and sheer user density will manifest themselves. Both range and
the reuse of limited spectrum can be greatly enhanced by using adaptive-array smart antennas
array to lock on a reflected signal that has described several reflections off intervening masonry
walls. Whatever part of the spectrum one chooses to inhabit, wireless broadband is hard to
employ in large cities with a lot of tall buildings. (Sometimes a wireless link makes sense,
however, which is covered in later chapters.)
Wireless broadband has been deployed with greater success in smaller cities and suburbs,
both because the markets are less competitive and because the geography is generally more
favorable. The first point is fairly obvious; secondary and tertiary markets are far less likely to
obtain comprehensive fiber builds or even massive DSL deployments because the potential
customer base is relatively small and the cost of installing infrastructure is not commensurately
cheaper. I will qualify the second point, however.
Suburban settings with lower population densities and fewer tall buildings tend to be
friendlier to wireless deployments than dense urban cores simply because there are fewer
obstructions and also because a single base station will often suffice for the whole market’s
footprint. Nevertheless, such environments still present challenges, particularly when millimeter
microwave equipment is used. Indeed, I know of no instance where millimeter wave
equipment has been successfully deployed to serve a residential market in a suburban setting.
Lower-microwave equipment is much better suited to low-density urban and suburban
settings, and thus it will receive more attention in the chapters that follow; however, where
equipment is restricted to line-of-sight connections, a substantial percentage of potential
subscribers will remain inaccessible in a macrocellular (large-cell) network architecture—as
many as 40 percent by some estimates. Advanced NLOS equipment will allow almost any given
customer to be reached, but, depending on the spectrum utilized by the network operator and
the area served by a base station, coverage may still be inadequate because of range and
capacity limitations rather than obstructions. Unquestionably, the new NLOS equipment will
permit the network operator to exploit the available spectrum far more effectively than has
been possible with first-generation equipment with its more or less stringent line-of-sight limitation.
But as the operator strives to enlist ever-greater numbers of subscribers, the other,
harder limitations of distance and sheer user density will manifest themselves. Both range and
the reuse of limited spectrum can be greatly enhanced by using adaptive-array smart antennas
(covered in Chapter 4), but such technology comes at a cost premium. Figure 1-1 shows a
typical example of an urban deployment.
Rural areas with low population densities have proven most susceptible to successful
wireless broadband deployments both by virtue of the generally open terrain and, perhaps
more significantly, the relative absence of wireline competition. But because of the extreme
distances that often must be traversed, rural settings can present their own kind of challenges
and can require the network operator to invest in multiple, long-range “wireless bridge” transceivers,
each with its own high-gain antenna.
Whatever the site chosen for the wireless deployment, mapping the potential universe
of users, designing the deployment around them, and considering the local topography are
crucially important to wireless service providers in a way that they are not to service providers
opting for DSL, hybrid fiber coax, or even fiber. However, in the case of fiber, right-of-way
issues considerably complicate installation. In general, a wireless operator must know who
and where their customers are before they plan the network and certainly before they make
any investment in the network beyond research. Failure to observe this rule will almost
certainly result in the inappropriate allocation of valuable resources and will likely constrain
service levels to the point where the network is noncompetitive.
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