Challenge or Opportunity?
Wireless mesh is changing the name of the game
- By Ksenia Coffman
- Apr 01, 2010
Wireless has been in the physical security space for years, especially
with point-to-point bridges. But the newcomers—
especially in the field of wireless mesh—are changing the
game. Will wireless be as ubiquitous for outdoor deployments
as cable or fiber?
There is still skepticism in the physical security community regarding wireless
as a go-to solution for security and surveillance. Will the signal be jammed? Will
there be enough capacity? How difficult is it to design and install? Do you need to
have specialized expertise, or even a sub-contractor, to deploy it successfully? What
is hype and what is reality?
Wireless: Niche or Mainstream?
Wireless transmission is still considered “niche” by many industry watchers; however,
they believe that wireless is an excellent option that is gaining acceptance
among integrators and end users. The advent of multiple input/multiple output
wireless mesh technology will accelerate this trend, as it delivers a fiber-equivalent
throughput of up to 300 MBps with 0.9 ms latency.
The benefits of wireless are well documented. Wireless connections have a much
lower cost of installation compared to trenching and digging—as low as one-tenth
the cost of fixed infrastructure. End users will avoid lengthy architectural approvals
and many of the disruptions associated with closing streets, re-routing traffic and
unsightly construction. In indoor settings, wireless is often the solution for historic
buildings where drilling and running cable would create a business disruption.
Paradoxically, wireless can be more reliable than fiber, if a network specifies
redundant paths. Fiber can be cut either accidentally or maliciously.
But consider the downsides of wireless as well. Wired infrastructure has standard performance over a
specified distance. On the other
hand, wireless systems operate in
a dynamic, changing environment,
both physically—e.g., seasonal changes
due to foliage or new construction—
and regarding RF disruption.
Key Considerations
All wireless technologies are not the
same, and extensive due diligence
should be part of the technology selection
process. Wireless technology is
essential to a system's success, so make
sure to consider the following points:
Capacity. Without sufficient bandwidth,
cameras cannot deliver evidencegrade
video or support video analytics.
With the advent of megapixel, HD and
thermal imaging cameras—all of which
require up to 35 MBps per megapixel
camera—a wireless network must be
able to withstand increased traffic.
Multicasting. Multicasting enables
video feeds to be sent to multiple destinations
for simultaneous viewing and
recording. Multicasting is essential for
monitoring, but it can severely burden
a wireless network. Many of the
analog cameras, when attached to the
IP network via encoders, appear to be
sending multicast traffic. Even without
a formal multicasting requirement,
a system needs to be able to transport
multicast packets without killing
the throughput.
Security. Wireless technologies—
point-to-point, point-to-multipoint or
mesh—used for video surveillance are
not cellular, nor are they Wi-Fi accessbased,
so they do not expose the users
to the same vulnerabilities. The most
secure systems offer end-to-end encryption
supporting WPA2 and WEP. In
addition to encryption, encapsulation
schemes also can be used to add a layer
of security.
Flexibility. The technology should
make it easy to gradually grow the network,
as funds become available, new
departments come on board or there is
a need to cover new areas.
Ease of setup. This is especially critical
for temporary installations, where
the installer may have only a few hours
to get the system in place. Even in fixed
installs, the cameras often need to be
repositioned as conditions change.
Multi-hop capability. This is ideal
for navigating around obstructions,
resulting in less dependency on wired
or wireless backhaul of point-to-multipoint
systems. In a city, point-to-multipoint
systems may not be able to reach
into the urban canyons. Look for systems
that support five to 10 hops before
backhaul is needed. This will lower
your cost for backhaul links, fiber or
dedicated point-to-point wireless.
End-to-end quality of service and
traffic prioritization. This is crucial
for video that is extremely sensitive to
variations in latency. Excessive delay
will result in the system being unresponsive
to the PTZ commands, while
jitter—packets arriving out of order—
will cause the video to freeze or drop
out. Access-point-based systems, along
with mesh APs, are especially subject to
these limitations.
On the business side, check for verifiable successes in the field and look at
comparable deployments. Wireless often
has difficulty scaling; a technology that can handle a dozen cameras may
not scale up to 50. Beware of data rates
listed in vendors' marketing literature.
These are theoretical and, as a rule of
thumb, usually translate to 30 to 50
percent of real-world throughput.
Taking Connectivity to Moving Vehicles
Real-time visibility into trains, buses
and industrial machinery is a frequent
customer requirement. Recorded video
is fine for investigations after the fact,
but many transit agencies and industrial
companies are looking for real-time
surveillance of unfolding situations, or
the ability to know what's ahead.
One of the first large-scale wireless
video surveillance deployments is Seoul
Korea's subway system. After 198 people
perished in the Daegu subway fire
in 2003, the Seoul Metropolitan Rapid
Transit Corp. began investigating realtime
wireless video surveillance systems
to help protect subway riders and transit
workers against potential fires, accidents,
thefts and other incidents. SMRT
has a ridership of more than 2 million
daily and involves a total of 201 subway
trains at 148 stations.
The Daegu fire was caused by an
arsonist who set fire to a car train that
was stopped at the Jungangho station.
The fire then spread to a second train
that had entered the station from the
opposite direction. After the incident,
SMRT wanted a system that allowed
train operators to have access to video
of the station before entering.
The ability to stream video from
a station's cameras to a monitor in a
train moving at speeds of 50 mph was
critical. Wireless mesh technology was
the only option to transmit video to
and from subway cars, as it provided
seamless handoff and roaming along
the fixed wireless infrastructure. The
subway environment is particularly
harsh for RF communications because
of the refl ective metal surfaces,
noise, vibrations and high voltage
electric power.
A total of 1,000 mesh nodes will be
deployed for all four SMRT subway
lines, along with 350 cameras in the
stations and 300 in the trains. The wireless
infrastructure delivers 20 MBps of
capacity, enabling real-time streaming
video at 30 frames per second to and
from the trains moving at 50 mph. In
addition to providing video surveillance
from the station to train operators, the
network also provides video surveillance
from inside the passenger trains
to a monitoring center. When completed
this year, it will be the world's first
real-time, high-bandwidth mobile wireless
video surveillance subway system,
costing an estimated $60 million.
Mobile real-time video is the wave
of the future for city-wide public safety,
industrial sites, campus environments,
mining and transportation. To maintain
real-time connections between fixed and
mobile nodes moving at high speeds—
without dropping packets or introducing
latency or jitter—
only wireless mesh will
fit the bill.