The recent financial and economic climate has prompted the search for low-cost solutions while still delivering the same quality. Compared to wired transmission, wireless transmission can save tens of thousands of dollars per project on trenching, cabling and building remodeling.
The greatest attribute of wireless transmission is its ability to negate wiring. “This means there is a lower cost of installation and easy maintenance,” said Parul Oswal, Industry Analyst, Frost & Sullivan. “It also gives users flexibility and ease in installing and moving cameras, remote accessibility to real-time video, and customization and integration with other features.”
SMALL-SCALE PROJECTS
A smaller installation usually consists of fewer than 10 network cameras, with additional signals from intrusion and access systems which do not generate much data to be transmitted. “Wireless is ideal for a home, SOHO or SMB, since wires cause clutter and cabling pains and are not aesthetically appealing,” Smith said. “Such installations do not require wide coverage and are simple. Wireless nodes are connected to the gateway, which in turn is connected to the computer and Internet. Connecting to the Internet allows for remote access, which is very appealing.”
Residential or SMB projects that require more bandwidth use access points. “Access points that look like smoke detectors are attached onto the ceiling, and they serve various Wi-Fi enabled clients such as laptops, smartphones and iPads,” said Walt Shaw, Senior Product Line Manager, Wireless Networking Business Unit, Cisco Systems. These are then connected to the LAN for integration.
In Europe, all security systems use 868 megahertz (MHz) for transmission . “ Priorto the development of the 868-MHz band 11 years ago, 433 MHz was used. Everything used to run on 433 MHz, such as remote-control toy cars and garage doors, which made the 433-MHz band a less secure frequency. The 868-MHz frequency is much narrower, which allows for less data but encounters less interference. In Greece, it is the frequency used for military purposes,” Bonafede said.
New frequencies are constantly being opened up for communications. “60 gigahertz (GHz) is now being used for a new standard for indoor connectivity called Wi-Gig, which will be used in residential installations for digital-video HDMI applications,” said Joe Schraml, VP of Marketing, BridgeWave Communications.
MEDIUM-SCALE PROJECTS
Medium-sized installations, such as a hotel or building complex, require larger bandwidth capabilities. “PtP and point-to-multipoint (PtMP) using Wi-Fi or other unlicensed transmission frequencies are probably the most appropriate for medium-sized projects — for both video surveillance only and integrated systems,” said Roy Cummings, Technical Support Manager, AMG Systems.
For outdoor deployments, using a private, dedicated, licensed frequency may seem appealing, but it is not often done due to cost considerations. “There are benefits to licensing a frequency because you own the whole spectrum, but it can cost up to thousands of dollars and will require numerous approvals,” Shaw said.
The double-frequency technique is also used for larger files requiring longertrans mission times. “Bandwidth limitations mean all data needs to be compacted, but even so, wireless still takes longer to transmit. To have a system that sends and responds quickly during an event, two different frequencies are used here in Europe. The 868-MHz frequency is used to transmit intrusion detection data first so that it may be immediately responded to, and video is sent on the 2.4-GHz frequency at a slower pace due to its file size,” Bonafede said. “Webcams can use the GSM network to transmit data in real time, but they are not usually used in mid-sized installations.”
LARGE-SCALE PROJECTS
A mesh network forms a data transmission grid over a large area, and is optimal for medium-sized integrations as well as large integrations. “Mesh networks automatically adjust to topology changes. Nodes can be added, removed, replaced or relocated without the need for traditional network administration. Mesh networks can optimize or increase the visibility of dynamic systems, such as the environmental conditions inside of a commercial building or the conditions of machinery in a manufacturing plant, without the cost and administration of a wired network,” said Benno Ritter, VP of Marketing and Business Development, ZigBee Alliance.
Being able to use many different frequencies opens up device selections, but it could also mean higher cost. “For some systems, it is possible to integrate several frequencies, but the cost becomes 50 to 70 percent higher,” said Patrick Lim, Sales and Marketing Director, Ademco Far East.
The most appealing aspect of the mesh topology is its ability to provide redundancy. “Some mesh options are intelligent enough to select up to eight different routes to send back a signal,” Lim said. He warns, however, that total redundancy for wireless video transmission is seldom considered, as it requires costly duplication of equipment and infrastructure.
Wireless video is very popular and can help reduce cabling cost in temporary large events, and it can also act as an extension to existing surveillance systems that have a direct LoS, Lim added.
MEGAPIXEL AND HD NEEDS
Megapixel and HD cameras are becoming more popular as users realize the need for usable images in the event of a crime. Different bandwidth capabilities and wireless applications have their own limitations, and not all are suitable for transmitting large image files from megapixel and HD cameras. “The volume of data produced by megapixel and HD cameras place more stress on the wireless network. This can be coped with by integrating more links, thus effectively increasing the size of the network. Potentially, this could mean using a separate
A single network video surveillance camera can transmit up to 5 Mbps, and 60- and 80-GHz frequencies have ample spectrum to allow the aggregation of multiple network video cameras f o r transmission to a central command center, Schraml said.
Naturally, implementing multiple network video cameras would require very large bandwidth, and one would consider using H.264 compression to decrease file size. This indicates that wireless transmission may not be the best approach for applications where image quality is of the utmost importance. “Compressed video signals always represent a trade-off between image quality and latency,” Cummings said. To set up a strong wireless system involving megapixel and HD cameras may cause much budget concern arising from the additional devices required to stabilize critical transmission.