Application note for Megapixel Imaging Infrastructure

Application note for Megapixel Imaging Infrastructure
Application note for
Megapixel Imaging
Infrastructure
Part B. Wireless Solutions
There are many cases where cost or local environment makes it difficult or too costly to trench and run
hard wire connections, either from edge devices or to connect network segments. This is where wireless
data transmission becomes a solution. In some urban environments, wireless mesh networks provide
cost effective ways for municipalities to monitor transportation corridors and high crime areas. The
typical wireless solution uses radio waves to make a connection from a wireless network client adapter
to an access point or router that is attached to the hard wired network. There are also systems that
provide point to point data connections using microwaves. Wireless solutions solve the need to run
physical connections between network devices but still require power to work from the location in
which they are installed. All wireless systems, radio based or otherwise, are essentially line of sight
meaning that anything between the transmitter and receiver has potential to impede or even block the
signal making them generally less reliable than hard wire connections. Most business class devices are
subject to radio interference and transmission quality can also be affected by local weather. This
document will examine the types of wireless medium available, advantages, limitations, potential
problems and best practices.
The Pipeline:
The amount of data bandwidth most wireless data transmission systems can carry is usually, but not
always less than that offered by wired systems. This is important to consider when looking at wireless
solutions for megapixel video transmission where bandwidth is taxed more than with other applications.
Factors such as signal strength, distance, radio interference, weather and trees can affect data
bandwidth. Wireless data bandwidth for radio devices ranges from 11Mbps for 802.11b radio devices to
10 Gbps with cost of ownership ramping up sharply. The highest bandwidth wireless systems are point
to point systems designed to connect private WANs across large campus or urban landscapes.
Radio/ Wi-Fi:
Most commonly encountered consumer and industrial-class wireless radio network equipment is based
around the IEEE 802.11 standards (http://www.ieee802.org/11/).
Type
802.11b
802.11g
Frequency
2.4GHz
2.5GHz
Speed
11Mbps
54Mbps
Cost
Low
Moderate
802.11n
2.4 & 5GHz
100Mbps +
Moderate to High
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802.11b is one of the oldest wireless network standards. It is very low cost, but slow speed and
there is the possibility of interference from 2.4GHz consumer devices (i.e. wireless home
phones).
802.11g is the most common wireless standard in use at this time. Cost of ownership is
reasonable, bandwidth is sufficient to support the largest data stream from 3 megapixel and
lower resolution IP cameras. Cost is reasonable, higher bandwidth, and backwards compatible
to 802.11b, but still the possibility of interference from 2.4GHz devices.
Quickly gaining ground, 802.11n supports higher bandwidth and improved transmission range.
Using 5GHz, it is less susceptible to interference from other devices and is compatible with both
b and g class devices. At 100Mbps rates and higher, the n standard provides enough bandwidth
to support full stream transmission rates from 5, 8, and 10 Megapixel cameras.
Wireless Topologies
802.11 Network Equipment
Wireless Network Adapters:, these devices provide connectivity to PCs, game consoles and streaming
media devices. They generally require a web browser to set up. Wireless network adapters are not
suitable for direct connection of Megapixel Cameras to a wireless network. There are exceptions to this
for some devices designed to automatically bridge game consoles to a wireless network. These usually
require a wireless router of the same make and series as the adapter, and do not support any manual
configuration.
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Wireless Bridges: These devices are the most suitable for direct connection of Megapixel cameras to a
wireless network. These devices can typically be set up via web browser and support a wireless link
transparent to the hardwired network interface on a Megapixel IP camera. Wireless bridges are fully
user configurable and support most common wireless encryption and security schemes. This type of
wireless device is available in both consumer-class devices and outdoor-rated enterprise-class devices.
There are high-end wireless bridges available that support point-to-point configuration, allowing two
bridges to act as a short distance wireless segment between two parts of a network. A wireless bridge
will provide a hard wired network port to a device, often can be powered by PoE, provide a singular
wireless connection and do not contain advanced routing functions.
Wireless Access Points: These devices provide a wireless gateway to a hard wired network. They are
typically used to provide wireless coverage into a hard wired network, without the expense, and
complexity of using multiple wireless routers for the same function. Wireless access points are designed
to provide multiple wireless connections into a network and often set up in overlapping array to provide
wireless coverage in a campus environment.
Wireless Routers: These are fully-fledged network routers that
also contain a wireless access point as well as hard wired LAN
and WAN ports. A wireless router can support gateways to other
networks and can support advanced routing functions. More
expensive and complex than a simple access point, wireless
routers are typically used in small office and consumer
environments as do-it-all networking devices. Most enterpriseclass networks utilize high-speed hard wired routers as network
controllers with wireless access points providing the coverage
An example of a MESH Network
and access for wireless clients. The exception to this would be a MESH
network. This is a specialized wireless networking scheme where multiple wireless routers are
configured to provide overlapping coverage across a wide area. MESH devices use the inter-connections
and multiple routing options created to provide a failsafe network which can automatically route data
streams across the shortest number of network hops to a hard wired connection. This type of scheme is
often implemented in urban municipalities providing secure broadband access to government networks
for public safety personnel. MESH networks of this type commonly include IP video systems with
authorized access to live and recorded video.
802.11 Wireless Distances Covered
The distance a wireless signal can cover depends on the signal strength, frequency, and line of site
between the transmitting and receiving device. Antennas in most consumer 802.11 class devices cover
distances between 50 to 100 meters assuming an unobstructed line of site with no interference. Higher
powered antennas are available that can boost coverage out to between 500 and 100 meters, again
assuming an unobstructed line of site with no interference. The reality is performance of wireless
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transmission will vary depending on the environment it is installed. Physical obstacles, rain, heavy fog
and radio interference from other devices can all affect the distance a radio signal is able to broadcast.
Other Transmission Systems Point-to-Point:
While not appropriate in scale and cost for implementing a single megapixel IP camera onto a network,
point-to-point transmission systems can provide high bandwidth long distance bridging of private
networks carrying megapixel video streams.
Microwave
Distances covered from 1 mile for unlicensed systems to distances in excess of 6 miles for licensed
systems, with bandwidth from 100 to 1000Mbps up to 10Gbps. typically, these systems require line-ofsite rooftop installation or erection of broadcast towers.
Best Practices
Choose a transmission system appropriate to the project scale and budget. Consider the required total
bandwidth for all data streams and plan accordingly to prevent data bottlenecks. When estimating
coverage, plan ½ the maximum transmission distance the equipment is supposed to cover and use a
wireless network sniffer to confirm that best transmission quality possible is achieved. Be aware of
obstacles such as walls and landscaping. Try to mount equipment as high as possible and with a clear
line-of-sight between transmitting and receiving devices.
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