The Application of Wireless Mesh Network Technology in the Community Security Intelligence

Intelligent security in residential communities is the current development trend. Because residential residential monitoring systems are very cost-sensitive, the use of wireless technology can save more than 90% of the cost compared to the use of wired solutions. This article will discuss the scheme and analysis of wireless Mesh technology used to build a residential district intelligent security.

Compared with traditional analog video surveillance networks, today's IP network video surveillance systems provide powerful solutions that provide greater flexibility, reliability, and further reduce deployment costs. In the past, wireless video surveillance was considered a point-to-point solution with poor reliability. As more and more users implement video surveillance on the Strix wireless Mesh network, the wireless Mesh network has changed this perception. The coverage distance and range considered impossible in the past few years are all achieved through the robust high performance, low latency and multi-hop scalability of the wireless Mesh network.

From a global perspective, the video surveillance market can reach more than 10 billion US dollars. According to the iSuppli CorporaTIon report, video surveillance equipment can reach 12 billion US dollars by 2011, which includes video surveillance cameras, DVRs and video servers. "It is expected that in 2015-2016, the network-based monitoring system will fully replace the analog monitoring system," IMS Research pointed out that by the end of 2009, "analog recording equipment will occupy only 5% of the market.

With the expansion of the existing network deployment and the development of a brand new network digital surveillance system, the development of the IP video surveillance market has also been successfully completed. With the transformation of DVR digital video recording to NVR (Network Video Recording) technology, the development of IP technology applications in the video surveillance market is also rapidly gaining popularity. In addition, IP video surveillance technology will also expand the video surveillance market and cover more new applications and new market segments. Wireless Mesh network technology has also become a new direction in the video surveillance market.

The Strix wireless Mesh network facilitates large-scale distributed video surveillance deployment, providing the industry's highest throughput, lowest latency, and unmatched flexibility and reliability for IP video surveillance systems. Strix wireless Mesh networks are widely deployed around the world, especially when users require wireless network performance comparable to wired networks, or to provide support for critical monitoring systems. Strix Access / One® is the industry's only wireless network architecture that has been tested by independent laboratories and verified by actual global deployment.

Traditional deployments use coaxial cables, expensive optical multiplexer distribution amplifiers, and even private twisted-pair solutions similar to Ethernet cables. The situation is changing rapidly. By eliminating the limitations of cables, many deployment obstacles and The additional cost is not possible in the past when the monitoring system could not be realized; as long as it is within the coverage of the wireless Mesh network architecture, the video monitoring head and video server can be placed arbitrarily, so more users find the advantages of the solution and gradually replace the traditional Analog video surveillance system.

Distributed Video Surveillance Network Helps the Construction of Intelligent Security System in the Community

Strix wireless Mesh network makes large-scale deployment and strategic IP video surveillance possible, especially for government, municipal, public safety or enterprise security, video surveillance is a key application system; it is also very suitable for price-sensitive residential communities Intelligent system.

Distributed video surveillance provides powerful capabilities for viewing, sharing, and distributing video. Together with statistics and integrated information like access control systems or intrusion monitoring systems, it eliminates the hidden dangers of centralized server farms and single points of failure. Strix provides a fully distributed wireless Mesh video surveillance system, including video cameras, video servers, storage clusters, customer application systems and remote viewing.

In addition, network video surveillance cooperates with applications such as remote alarm systems to further improve the efficiency of the security department and reduce the cost of responding to false alarms. According to statistics, for most government and enterprise units, this function reduces the error by 90% Alarm rate.

Construction of intelligent security system in residential area

Advantages of IP video surveillance

Scalable deployment based on user needs

Make full use of wireless and other architectures, can use existing IP network equipment

Cooperate with other security systems and have good interoperability with other network equipment

Optimize video stream to reduce storage space, traditional video compression technology needs more storage space

Use wireless technology to distribute video to multiple locations, reducing time and labor costs

Improve security coverage area and improve video transmission quality

Handheld terminal can view video surveillance information at any time at any place

Faster and easier installation, easy to upgrade and migrate

Solution evaluation

In order to make the most accurate network assessment, several factors are very critical, including the video compression algorithm, the number of cameras, the location of the video server, and the remote viewing location.

Not to be confused with NTSC and PAL in analog surveillance, the VGA standard defines the resolution of IP video surveillance. The video compression algorithm determines the video quality, image size, and frame number. Together with the image update technology, it determines the bandwidth requirements for video surveillance. The bandwidth of video surveillance can be from a few hundred K to several megabits per second, with a maximum of 30 frames per second.

In order to reduce bandwidth consumption, smart cameras and bandwidth optimization features can reduce the size and speed of image transmission, while also considering the bandwidth and delay of remote viewing and PTZ functions. Depending on the camera used, the PTZ control delay is generally less than 250ms, and in the analog configuration, the encoding / decoding process will be 150-200ms. Because it is connected to the video server for monitoring, the remote viewing application also consumes a portion of the video transmission bandwidth; although managers can directly access the camera. Each manufacturer's remote viewing technology allows users to choose to view the number of video surveillance cameras, camera grouping, resolution, frame number, and PZT control.

In order to fully solve the bandwidth problem, it is necessary to further discuss video compression, IP cameras and network video servers.

Video compression method

A normal analog video stream without compression can consume up to 165Mb / s bandwidth, while a megapixel IP camera can consume several G of bandwidth. Therefore, video compression hormones must be used in order to reduce the image size and reserve more bandwidth.

The degree of compression will affect the quality of radio frequency monitoring, resulting in video not being cleaned or distorted, so a balance must be made between compressing the video image size and keeping the video clear. Generally, the solutions of IP video surveillance heads and video server manufacturers have reached this balance, and the standards that manufacturers can adopt have already been established.

There are currently a variety of compression methods, mainly including H.264, MPEG4 and MJPEG; can be divided into two categories, namely, each frame compression coding method and dynamic coding method.

When considering video compression methods, MJPEG is the most widely used compression technique per frame, and it is completely compressed for each video frame. This technique allows predictable video requirements to be determined, but at the same time, MJPEG is not bandwidth efficient, especially in situations like moving leaves.

H.263, H.264 and MPEG4 technologies have been continuously popularized and widely used in video deployments with slightly lower bandwidth and lower image quality. Dynamically compress all the key frames, not all of them for the back pillow, and frames with changes will be compressed and transmitted. Therefore, the advantage of this technology is to send only the parts that have changed outside the critical frame, which can save 50-80% of the bandwidth. Strix Access / One adds performance advantages and increases network scalability.

IP video surveillance camera

The current IP camera not only improves the traditional technology and increases the network interface, but also makes great progress in adopting the new analog conversion technology. In the past few years, CMOS technology has promoted the digital-to-analog conversion of low-cost IP video transmission. Progressive scanning better shows moving objects, and the analog camera will have interlaced scanning problems at 4CIF high resolution, resulting in blurred moving objects. The analog video image is composed of lines, and each image is formed by progressive scanning. When the image contains many moving objects, the image will become blurred at the progressive scanning.

The advanced technology of IP video surveillance digital pixel image sampling surpasses the traditional analog CCD technology. Through the use of digital pixel image technology, one image can be acquired at a time, even in the case of height movement, it can still provide a clear image. The latest pixel image sampling technology supports low brightness and special lighting conditions, fully implementing all the functions of CCD technology. The embedded intelligent algorithm includes built-in dynamic discovery, automatic compression selection, bandwidth and network optimization control, and video transmission decision-making process. The new generation of video cameras includes a programmable API interface and a DSP. The DSP can be accessed directly or through the NVR's programming interface.

In this way, the PTZ camera can be programmed to recognize the object, zoom in to obtain a high-resolution image and then trigger an alarm, telephone or email to the security personnel. In addition, by entering the megapixel imaging technology, the IP camera can surpass the industry's traditional high-resolution scheme of NTSC / PAL. Compared with today's digital / analog cameras (the more pixels are 400,000), megapixel cameras can provide 1 million to 5 million pixel images, and higher pixel levels can be achieved in the future.

New bandwidth optimization technologies, such as frame rate control technology, have become built-in functions, while traditional analog cameras always send all video. The frame rate control technology of network video monitoring means that the IP camera / video server only sends video with a specific frame number, and no unnecessary video is transmitted on the network. The IP video camera / video server can be configured to increase the frame number after discovering a moving target , Or send different frames for different receivers, etc., these characteristics are very suitable for the situation where the bandwidth of the remote location is not high.

Another important development work is the VMD (Variable Motion Discovery) technology. VMD is an integrated function of IP camera and NVR, which provides many advantages over DVR. As a built-in function of IP camera or video server, VMD reduces the load of recording equipment and makes event-based video surveillance possible. When no motion occurs in the field of view, no video will be sent to the operator or video recording equipment. VMD data about activity information can be included in the video stream to simplify finding activities in storage. The VMD can also be located in the video management software to provide this function for IP cameras that do not have the VMD function.

The advantages of the IP camera and the local VMD function of the video server include: saving bandwidth, reducing the CPU load of the recording device, saving storage space, and the camera can cooperate with other systems through input / output ports (such as triggering alarms).

Based on the above dynamic characteristics, it is very difficult to estimate the required bandwidth of the monitoring system, so the general reference basis for calculating the bandwidth according to the resolution is listed in the following table. In this way, the bandwidth requirement can be determined by simply calculating the size of the image and multiplying by the number of frames per second.

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