WiMax Operator's Manual

CHAPTER 4 ■ SETTING UP PHYSICAL INFRASTRUCTURE 69
power at a fixed voltage and with low values of line harmonics, preferably less than 1 percent
under conditions of load. In this context, the low-cost UPSs utilized in business offices are
unacceptable. Medical-grade backup power should be the standard, with appropriate power
conditioning apparatus to maintain a clean, smooth 50- or 60-cycle sine wave, and the system
should be designed to provide ride through, that is, continued delivery of electrical power
while the backup power-generating system is coming up. The specifics of backup power facilities
design are quite involved and are beyond the scope of this book, but the objective is
simple—to ensure that the central office will continue to operate perfectly in the case of a
power blackout or brownout. My recommendation is that the network operator retain a consulting
engineer with demonstrated expertise in power quality.
The facility where the vital equipment resides should have personnel on the premises at all
times to control access and should be provided with ancillary surveillance and alarm systems
communicating back to a highly secure monitoring facility.
Equipment should be professionally mounted on steel or aluminum racks, and cable
management accessories should be employed so that reconfigurations and additions to the
network can be easily managed. All equipment should be easily accessible to technicians, and
racks should be situated with sufficient clearance to permit any connection to be manipulated
without the removal of a component from its rack. A centralized command console with a
high-definition monitor and comfortable seating for the network manager is advisable.
The equipment racks should rest on a raised floor as a safeguard against natural disasters.
The interior should be climate controlled and properly ventilated, and auxiliary independently
powered climate-control systems should be in place in the event of a power loss. The structure
enclosing the equipment should be highly fire resistant, and highly impact-resistant glazing
should be installed. Doors and locks must be completely resistant to being forced open with
hand tools.
All operating software and customer records must be backed up continually and mirrored
at a secure facility. Retaining a reputable disaster recovery firm to mirror the entire computing
operation at the central office is also recommended in the event of a large-scale catastrophe
that destroys all or part of the central office.
All these recommendations constitute best practices and are entirely typical of traditional
telecommunications incumbents, but they are not observed by all broadband access providers,
and the degree to which they are absolutely essential is debatable. If one is providing
nothing more than high-speed access to residential customers, then one may reasonably opt
for a lower degree of security and infrastructure integrity at the central office, though one
would certainly have strong reason to protect customer records. If, on the other hand, one is
providing essential telephone service, then one incurs a grave obligation to the subscriber and
to the larger community. Business users, particularly larger enterprises, will also expect that
the network will be well secured and equipped to survive disasters. The loss of a data link for
hours or days can be devastating to a business, especially one involved in conducting online
financial transactions and recording such transactions. The degree of legal liability facing a
carrier or service provider that fails to follow such best practices is uncertain, but no sane individual
would want to compromise the business of a major subscriber or jeopardize public
safety because the network failed to perform adequately.