The World of Wireless
Video surveillance demonstrates value, benefits with real-time monitoring
- By Richard Ho
- Apr 01, 2009
As security risks increase, the need to visually monitor and record events in the most remote areas becomes even greater. Moreover, the value of video surveillance has grown significantly with the introduction of intelligent motion, temperature and sound sensors. Intelligent sensors, combined with video analytics, bring forth the newest generation of powerful digital security systems for the post-Sept. 11, 2001, era. Integrated video, analytics and sensors help authorities make better decisions and drastically improve response times.
As security equipment moves away from closed analog systems to open digital systems using IP, the network that connects all aspects of the system is critical. A networkbased security system is only as good as the network that connects it, to share and relay time-sensitive security information between each functional component.
As the IP standard develops, security professionals face many choices in cost-effective reliable transmission media. Fiber optics, Ethernet cabling and wireless methods are among the most widely used. Wireless networks, overlooked in the past because of a reputation for poor performance and reliability, have become accepted as an option. In many remote security applications, they are the only option.
The Economic Case
Using IP video, also known as networked video, over a wireless medium is not a new concept. With the industry boom in unlicensed Wi-Fi and fixed wireless broadband, economies of scale in IEEE 802.11-based hardware has led to less expensive, more rugged outdoor and long-range radios. Lowering project cost is perhaps the largest benefit of deploying a license-free wireless video network. Lower cost barriers allow security professionals to place cameras in areas that are difficult or impossible to hardwire.
Faster deployment is another benefit. Security professionals can tackle large outdoor video surveillance projects in shorter project life cycles, creating a faster return on investment and a more satisfied customer.
Wireless IP networks provide more flexibility and scale compared to other video surveillance network transport media. They make temporary surveillance applications possible because they can be easily uninstalled from one location and reinstalled at a new site. From construction sites to public safety at city events, wireless video surveillance networks have demonstrated value by lowering crime.
The flexibility of wireless networks for security applications allows for more remote security applications once too costly to even consider.
Wireless Reliability with OFDM
There remain a number of myths about wireless communication, fueled in part by users’ experiences with analog systems. The first myth is that wireless is unreliable and complicated. The truth is, digital wireless video links, when deployed correctly, can offer reliability equivalent to, or exceeding, wired installations. Wired installations are prone to cable or interface corrosion, and disturbances are costly to replace. Wireless video links have the added feature of link redundancy, and base station failover and testing, and experience has demonstrated a reliability of 99.9 percent.
Wireless has its challenges. What was considered long-range performance is now short range due to the increasing interference challenges of shared spectrum or license-free fair usage. Along with the general challenges of signal-to-noise ratio, the main problems are inferior RF hardware design causing self-interference and fading owing to multipath effects, which occur when the same signal arrives at a receiver via different paths. Orthogonal frequency division multiplexing meets these challenges by stablizing the unruly ways in which radio signals misbehave in the real world.
OFDM is a wireless signal modulation technique that uses multiple subcarrier waves. Compared to wider single carrier modulation to transport data information, smaller multiple carrier waves are divided to carry only a slice of the whole data information. When wireless transmission is interrupted or corrupted, only the slice of the transmission is affected compared to the whole, providing higher performance throughout the transmission process. When all the mathematical language and formulation is not considered, OFDM is a method for chopping a large frequency channel into a number of subchannels. The subchannels are then used in parallel for higher throughput.
The IEEE 802.11a and IEEE 802.11g standards are designed based on OFDM. OFDM is not a new technique. Most of the fundamental work was done in the late 1960s, and a U.S. patent was issued in January 1970. In IEEE 802.11a, OFDM provides raw data rates up to 54 MBps in a 20 MHz channel.
In addition to supporting high-data capacity and resisting degradation from various types of radio effects, OFDM makes highly efficient use of the available spectrum. The latter characteristic will become crucial in coming years as wireless networks are expanded.
OFDM’s simple architecture overcomes noise, signal-to-noise ratio challenges, multipath fading, adjacent channel interference and non-adjacent channel interference.
OFDM is used in digital cable, DSL, digital TV, European Telecommunications’ HiperLan and power-line networking products (see Table I). Cellular carriers also are considering migrating from CDMA or TDMA to OFDM for use in 4G cellular systems, which consist of video, voice and data. Currently, 3G networks cannot cost effectively provide the whole Internet experience to the mobile user. However, OFDM can overcome signaling transmission barriers and increase transmissions speeds, while dealing with unpredictable changes of the radio frequency environment.
Leading wireless security equipment manufacturers use OFDM as their primary modulation technique, each with its own proprietary range extension algorithm to achieve wireless link distances of 30 kilometers or more. IEEE 802.11 a/g-standards-based devices—compared to similar technology items using OFDM—have economy of scale and one of the largest install bases in the world. IEEE 802.11 a/g standards are well proven and are one of the most successful industry standards in history. IEEE 802.11 a/g is experiencing rapid advancement with newer extensions released to enhance wireless performance.
Serious wireless players are considering the use of OFDM modulation technique for 4G mobile networks to enhance voice, data and video. OFDM is reliable and robust, offers highly efficient use of available frequency and is available today with standards-based wireless equipment.
Wireless Capacity and Flexibility
Radio transceivers operate in point-to-multipoint mode, allowing a single base station to communicate with multiple wireless transceivers. That makes adding new camera nodes to a wireless surveillance network as simple as adding a new wireless transceiver and video camera system. With access to more than 20 MB of bandwidth on an 802.11g wireless transmission link and 50 MB on an 802.11a link, a wireless video network can scale to accommodate large outdoor camera systems reliably. With the onset of the IEEE 802.11n draft standard, wireless medium capacity may reach 150 MB or more and is a cost-effective alternative to hardware wiring. (See Table II.)
Another myth is that wireless is unsecure. True, the wireless encryption protocol used on the first-generation digital wireless LAN networks was easily defeated, but that was more than 10 years ago. The latest software tools and wireless sniffers are able to derive the network key within minutes of sampling a communication link.
Newer outdoor wireless video transceivers use chipset technology with strengthened security. Advance encryption is a standard feature on all IEEE 802.11a and 802.11g digital transceivers from Inscape Data. AES is a standard recognized by the government for transmittal of classified information.
AES is the highest level of wireless encryption available to the public. The most significant advantage of AES is that every time data is sent, it is encrypted with a unique key. Breaking AES encryption is almost impossible, but according to industry experts, the time required to break WEP is less than 10 minutes. (See Table III.)
Wireless encryption based on AES is secure for video applications and for corporate and government use. AES accommodates 128-, 192- or 256-bit keys.
To obtain the most benefit out of wireless video deployment, end users must understand the challenges that come with a successful deployment. Equipped with wireless fundamentals, overcoming wireless obstacles and maximizing available bandwidth are key. Wireless signals are invisible, and making them visible enough to manipulate requires learning and practice.
Wireless signals spread out and get weaker as they leave an antenna. They lose significant strength when they encounter an obstacle or reflect off the ground, bodies of water or a building. A wireless signal operates optimally line of sight on the same channel between two base stations. This configuration, however, lowers overall wireless network capacity, which means it accommodates fewer cameras.
One of the common mistakes of outdoor wireless video network deployment is the default use of omnidirectional antennas, which radiate wireless signals in all directions and are ideal for maximizing a coverage area. However, since the antennas also function as receivers, they also pick up noise and potential interference from all directions. Care should be taken when selecting the type of antenna. Many systems are designed with a mix of directional and omnidirectional antennas; each affects the signal. Radio engineers work with “link budgets,” which measure both the capacity and strength of a radio link and the amount of degradation it can sustain before complete loss of signal.
Remote wireless video surveillance for distances beyond a few miles also is possible with unlicensed wireless devices. Long-range remote wireless video surveillance makes it possible to centralize video surveillance from several remote areas. In certain parts of the world, base stations can use solar power. This allows deployment of video surveillance cameras almost anywhere.
Armed with fundamental wireless knowledge and deployment confidence, numerous application possibilities are brought forth by long-range digital wireless transceivers. For example, the commercial parking lot video surveillance project once thought too costly may be revisited, and border and port protection projects become more manageable.
Many More Applications
Wireless networking for the security sector is not limited to video surveillance. Wireless access control also is gaining popularity. Increasing use of wireless for access control has been driven by the same factors as video. Users want access control systems to transmit video, voice, relays and sensors from remote stations to a master station economically and reliably. Unlicensed wireless systems allow access control applications to manage hundreds of entrances or gates across several campuses from a single location without dedicated hardwiring.
IP-based video surveillance will continue to evolve. Wireless remote surveillance applications will become more integral to an organization’s video surveillance roadmap. As digital IP-based security technology advances, the use of reliable IP wireless products will continue to increase, shifting from a functional role of branch network for a few remote video surveillance cameras to providing the video surveillance wireless backhaul between campuses or remote locations.
This article originally appeared in the April 2009 issue of Security Today.