No Strings Attached
Benefits outweigh risks in choosing wireless access control solutions
- By Ray Shilling
- Jun 30, 2008
Much attention has been given
to the development and
deployment of IP-based
video surveillance systems. However, the
adoption rate of these new technologies
has been slowed, in part, by the heavy
bandwidth consumption of video streams
and their adverse impact on the network.
Meanwhile, unhindered by these
restraints, manufacturers of relatively low
data-rate access control systems gradually
have been introducing network-based
offerings of their own. The idea is to take
advantage of the powerful and ubiquitous
TCP/IP communication platform without
the drawback of convincing the IT
department to permit consumption of
large quantities of their most precious
Furthermore, the IP network is reasonable
to deploy and universally understood.
IT professionals from any nation
work within the same framework and rule
set, therefore installation and configuration
challenges associated with proprietary
technologies are all but eliminated.
However, in many cases, a wire-line
network connection is not readily available
at all locations where access control points
may be required. Few buildings—even
those that are relatively new—include network
connections (RJ-45 ports) at their
doors and gates. As a result, wireless technologies
are being considered to deploy
these Ethernet-based edge devices. End
users should explore many factors when
designing and deploying a wireless
Ethernet-based access control system.
With its introduction several decades ago,
electronic access control has solved many
of the limitations of mechanical locks and
keys. A wide range of credentials can be
used to replace mechanical keys; the
electronic access control system grants
access based on the credential presented.
When access is granted, the door is
unlocked for a predetermined time, and
the transaction is recorded. When access
is refused, the door remains locked, and
the attempted access is recorded. The system
also will monitor the door and alarm
if the door is forced open or held open too
long after being unlocked.
In most access control solutions, the
system uses a simple challenge-response
system to allow access to a door or gate.
When a credential is presented to a reader,
it sends the credential’s information, in
the form of an encrypted bit string, to a
control panel. The control panel compares
the credential’s number to an access
control list, grants or denies the request
and sends a transaction log to a database.
When access is denied based on the list,
the door remains locked. If there is a
match between the credential and the
access control list, the control panel operates
a relay that, in turn, unlocks the door.
Therefore, communication typically is
taking place between the access control
hardware at the door and a panel containing
the system intelligence and database
of authorized personnel. This communication
traditionally has taken place along
standard low-voltage cabling, creating a
dedicated loop between the two devices.
The advantage of this dedicated design is
that it allows the system designer complete
end-to-end control of the system’s
cabling, without concern for impact from
other devices running on the same wire.
The principal disadvantage is that the
reader devices must be hard-wired to the
central panel to facilitate communication,
and therefore costly cable runs to every
access-enabled door are required. The
system cannot be easily accessed from
other geographical locations.
Why Use Ethernet?
Before examining the case for wireless
technology, first understand that an
Ethernet-based IP solution is preferred
over a traditional closed-loop proprietary
protocol. Here are the most compelling
Ubiquitous existing infrastructure.
Billions of linear feet of Cat-3, Cat-5(e)
and Cat-6 copper cabling and optical
glass fiber are already installed worldwide.
TCP/IP networks are everywhere
and are being used to support data transmission in almost every vertical market.
Ethernet (IP) technologies also are
widely understood by many IT and business
process professionals; therefore, it is
easier to conduct discussions among disparate
groups within a company to reach
consensus and share network resources
Finally, since TCP/IP networks are
standards-based, manufacturers can
develop and bring to market products that
are cost-effective and readily upgraded.
Thus, with this infrastructure in place,
access control companies are providing
customers with the ability to leverage the
existing network and not requiring them
to run new dedicated low-voltage cabling
from every door controller and/or card
reader to a centralized database server.
Cost. Since so much of the TCP/IP
network infrastructure already exists—
and in many cases is underused and contains
extra capacity—the system designer
ought to consider using existing network
cabling prior to specifying a solution that
requires new low-voltage cabling installation.
Fortunately, data rates required for
access control are low, therefore the system
designer can obtain permission from
the IT department to allow the system to
use the current TCP/IP network.
Scalability. Access control systems
are by their very nature spread out across
large areas. This is usually because the
points of access or egress are at the edge
or perimeter of a building or facility. It
makes perfect sense that the ideal technology
to communicate between these
devices is one tuned to fit large areas.
As a result, when discussing which
platform to standardize upon—whether
concerning a few doors on one floor of a
small office building or gates spread
across a 15-square-mile major international
airport—integrators need a solution
that will readily scale up.
It is generally accepted that Ethernet
communication technologies provide the
most robust, cost-effective and easy-toinstall
solutions to deploy edge devices
across a wide variety of geographic conditions.
Ethernet networks are, by design,
modular and highly scalable. Adding network
subnets can be as simple as installing
a managed switch or network bridge and
laying additional cable. Using internal IP
addressing, the number of network-based
devices that can be installed to communicate
with each other is numerous.
Accessibility. Finally, and perhaps
most importantly, the power of an IPaddressable
system is most evident
when examining its accessibility or visibility
from other geographical locations.
Inside the router—on the same
subnet or the LAN—simply calling the
internal IP address will provide instant
access to the device. This is useful;
however, even more valuable is the ability
to use network address translation
and port forwarding. This way, any IP
device can be configured for easy
access for external communication
requirements from outside the router
serving the LAN. This means, unlike
closed-loop dedicated point-to-point
low-voltage cabling, the IP-based system is accessible from an Internet connection
anywhere in the world.
Why Go Wireless?
A wireless transmission solution is not
always preferred. When transmission distances
increase, and the bidding on the
project becomes more competitive, it
makes sense for the system integrator to
consider going wireless. Here are a few of
the principal factors:
Cost. Price is always an important
consideration for any job and is the most
significant factor in the case of government
projects. Therefore, when designing
a new network-based access control system,
the choice must be made between
the price of the materials and labor associated
with dedicated cabling runs and
conduit versus the cost of the Ethernetbased
radio transceiver and power supply.
Since long-range wireless Ethernet radio
transceivers are now below $300, while
the price of copper and conduit is rapidly
increasing, it often makes sense to examine
the wireless option for any distance
greater than 50 feet in a building.
In an outdoor installation, connecting
a main building to a perimeter gate access
system is even more compelling. The cost
of trenching conduit in place can be more
than $35 per foot. A radio transmission
system is almost always more cost-effective
in these situations.
Due in part to rising insurance and
healthcare costs, labor rates have
climbed briskly over the past two
decades, making labor a significant
component in the overall cost of the
project. The cost of labor to pull cable
can be difficult to estimate—especially
in older buildings—but it is likely to be
greater than the few hundred dollars the
wireless radio equipment costs.
Interruption in service. On the job
site, the use of wireless radio transmission
means that the system can be
installed during regular business hours
without as much concern for the interruption
in service associated with pulling
cable. This should be taken into account
when estimating the actual total cost of
the cabled solution versus that of a wireless-
Appearance. Trenching cable outdoors
will often leave a scar on the landscape.
In many cases, this is hard to quantify
from a cost standpoint, but certainly
most professional facility managers
would prefer to not have their parking lot
cut through unless absolutely necessary.
Unforeseen incidents. Negotiating
in-ceiling cable runs under difficult
conditions—in an older building that
might be contaminated with asbestos,
for example—is a nightmare for all parties
involved with the project.
Furthermore, digging trenches on a job
site to lay conduit for the network cable
can be risky if the underground utilities
in the area are poorly