Bandwidth Basics for IP CCTV Design
When using IP cameras, Megapixel
cameras, NVRs or even DVRs, understanding the basics about how much bandwidth
is available and how much is needed is critical in planning, designing and
deploying IP video surveillance systems. Copper Ethernet
wiring (typically Cat-5, Cat-5e, Cat-6 or Cat-7) have a practical length
limitation of 100 meters (or about 300 feet) between devices. To accommodate longer-length
wired network connections, fiber can be used.
This article is focused for a non-IT audience such as security managers,
electronic technicians, sales and marketing folks.
How Much Bandwidth is Available?
To figure out how much bandwidth is available, you first need to determine
what locations you are communicating between. Much like driving, you will have
a starting point and destination. For example, from your branch office to your
headquarters. However, unlike driving, the amount of bandwidth available can
range dramatically depending on where you are going.
The most important factor in determining how much bandwidth is available is
whether or not you need connectivity between two different buildings.
For instance:
In the Same Building: 70Mb/s to 700 Mb/s of bandwidth is generally available
In Different Buildings: .5 Mb/s to 5 Mb/s of bandwidth is generally available
The amount of bandwidth available going from your office to a co-worker's
office in the same building can be 200 times more than the bandwidth from your
office to a branch office down the block.
This is true in 90% or more cases. Note the following exceptions:
If these are different buildings but on the same campus, more bandwidth may be
available.
If you are in a central business district of a major city, more bandwidth may
be available.
If you are a telecommunications or research company, more bandwidth may be
available.
Different Buildings
The key driver in bandwidth availability is the cost increase of deploying
networks between buildings. Generally referred to as the Wide Area Network or
WAN, this type of bandwidth is usually provided by telecommunications
companies. One common example is cable modem or DSL, which can provide anywhere
from 0.5 Mb/s to 5 Mb/s at Rs. 3000 to Rs. 5000 per month. Another example is a
T1, which provides 1.5Mb/s for about Rs. 8000 to Rs. 16000 per month. Above
this level, bandwidth generally becomes very expensive.
Many talk about fiber but fiber to
the building is not and will not be widely available for years. Fiber to the
home or to the business promises to reduce the cost of bandwidth significantly.
It is very expensive to deploy and despite excited discussions for the last
decade or more, progress remains slow.
Same Buildings
By contrast, bandwidth inside of buildings (or campuses) is quite high
because the costs of deploying it are quite low. Non technical users can easily
set up a 1000Mb/s networks inside a building (aka Local Area Networks or LANs)
for low installation cost with no monthly costs. The cost of deploying networks
in buildings are low because there are minimal to no construction expenses.
When you are building a network across a city, you need to get rights of ways,
trench, install on telephone poles, etc. These are massive projects that can
easily demand millions or billions of dollars in up front expenses. By
contrast, inside a building, the cables can often by quickly and simply fished
through ceilings (not the professional way to do it but the way many people do
it in deployments).
A lot of discussion about wireless (WiMax, WiFi, 3G, 4G etc) exists but
wireless will not provide significantly greater bandwidth nor significantly
better costs than DSL or cable modem. As such, wireless will not solve the expense
and limitations of bandwidth between buildings. That being said, wireless
absolutely has benefits for mobility purposes and connecting to remote
locations that DSL or cable modem cannot cost effectively serve. The point here
is simply that it will not solve the problem of bandwidth between buildings
being much more expensive than bandwidth inside of buildings.
How Much Bandwidth Do IP Cameras
Consume?
For the bandwidth consumption of an IP camera, use 1 Mb/s as a rough rule
of thumb. Now, there are many factors that affect total bandwidth consumption.
You can certainly stream an IP camera as low as 0.2 Mb/s (or 200 Kb/s) and
others as high as 6 Mb/s. The more resolution and greater frame rate you want,
the more bandwidth will be used. The more efficient the CODEC you use, the less
bandwidth will be used.
For the bandwidth consumption of a Megapixel camera, use 5 Mb/s to 10 Mb/s as a
rough rule of thumb. Again, there are a number of factors that affect total
bandwidth consumption. A 1.3MP camera at 1FPS can consume as little as 0.8 Mb/s
(or 800 Kb/s) yet a 5 megapixel camera can consume as much as 45 Mb/s.
What Does this Mean for my IP Video
System?
Just like dealing with personal finance, we can now figure out what we can
'afford':
Between Buildings: We have 0.5 Mb/s to 5 Mb/s to 'spend'
Inside Buildings: We have 70 Mb/s to 700 Mb/s to 'spend'
IP cameras: Cost us 1 Mb/s each
Megapixel cameras: Cost us 5 Mb/s to 10 Mb/s each
Using these points, we can quickly see what combination of IP and megapixel
cameras we can use between buildings or inside of buildings.
Inside of buildings, it is easy to stream numerous IP and megapixel cameras.
Between buildings, it is almost impossible to stream numerous IP and megapixel
cameras.
Because of this situation, the standard configuration one sees in IP Video
systems is:
A local recorder at each building/remote site. The local recorder receives the
streams from the building and stores them.
The local recorder only forwards the streams (live or recorded) off-site when a
user specifically wants to view video. Rather than overloading the WAN network
with unrealistic bandwidth demands all day long, bandwidth is only consumed
when a user wants to watch. Generally, remote viewing is sporadic and IP video
coexists nicely with the expensive Wide Area Network.
The local recorder has built-in features to reduce the bandwidth needed to
stream video to remote clients. Most systems have the ability to reduce the
frame rate of the live video stream or to dynamically reduce the video quality
to ensure that the video system does not overload the network and that remote
viewers can actually see what is going on the other side. Generally, the live
video stream is sufficient to identify the basic threat. In any event,
bandwidth is generally so costly, especially the upstream bandwidth needed to
send to a remote viewer, that this is the best financial decision.
