Through wireless transmission way, let the Internet, watching TV, or receive audio, data and other activities, no longer subject to the conditions of space, is the dream of modern people; And the sustainable development of short distance wireless transmission technology, let the dream gradually implemented.

In fact, the application of short distance wireless transmission technology has been very common, such as general common wireless telephone headset, wireless information home appliances, etc., even in the security industry, there are wireless application products; The CCTV industry for the development of increasingly diverse, with the evolve of the short distance wireless transmission technology, its function and characteristics of wireless products also renovates ceaselessly; Can be found, the short distance wireless transmission technology for the CCTV industry, has its importance can never be ignored.

Four short distance wireless transmission technology

The short distance wireless transmission can be simply classified as infrared, IEEE802.11, four technologies such as bluetooth and HomeRF:

Ir (Infrared)

Infrared can be divided into Direct type infrared (Direct) - Beam IR, scattering type infrared Diffuse (IR) and omni-directional infrared (Ominidirectional IR). Due to the infrared ray is a kind of light, and light cannot penetrate any opaque objects, so the direct type infrared connection mode to transmit data, two each point must be in line to see each other the same, that you can't have any barrier; Scattering type infrared connection modes do not need in the same line, but it must be in the same enclosed space; Omnidirectional infrared is using an infrared base stations, will be scattered around the base station transmitter by the ir together.

IEEE802.11

IEEE802.11 applicable under the regional environment, such as need freedom support office action, can use wireless transmission cost savings office; Only need to set up a base stations, and electronic products in this area are network card installed, using the IEEE802.11 wireless transmission technology, in the absence of any cable, data transmission distance up to 100 meters indoors (accessibility of up to 300 meters).

Bluetooth

Bluetooth is a short-range, low power, low cost wireless communication standard, to replace the infrared transmission distance is too short, do not have the problem such as penetrability. Bluetooth development plan, is to locate it for low power, small scope of frequency hopping RF system, its design is suitable for connecting computers and computer, computer and peripheral and computers and other mobile devices, data such as mobile phone, pager, PDA, etc. Due to the bluetooth module can easily into any electronic products, so the user through any bluetooth device can communicate with these products.

HomeRF

HomeRF construction in SWAP (Share Wireless Access protocol) technology, mainly used in the home network. Its not only for data transmission, more integrated voice transmission capacity, can combine computer network and telephone network, provide a more complete solution. At present in the wireless network environment, HomeRF a bluetooth transmission distance is long, transmission data quantity is more, so more suitable for the application of video transmission.

HomeRF wireless CCTV technology preferred

The above four short distance wireless transmission technology, in addition to the bluetooth because of my lack of bandwidth is less used in security industry, other such as infrared, IEEE802.11, HomeRF, are security industry wireless applications

The darling of the; Main transmission infrared data, however, is generally more common in wireless alarm equipment; But IEEE802.11 constructed with wider range of transmission, more applications in the area of the point-to-point transmission, such as wireless local area network, etc.; As for HomeRF, due to the transmission distance and transmission data amount in accordance with the demand of the China central television (CCTV), and the cost is low, so is the first selection of more wireless CCTV vendor technology.

HomeRF at present the biggest problem, however, lies in its frequency Shared too frequently, make the transmission of video data or vulnerable to interference; In addition the signal easy to intercept, also makes the confidentiality of the serious test.

Short-range wireless digital transmission technology into a trend

HomeRF signal to interference and confidentiality issues such as poor, now have a solution? HomeRF is more popular in the application of wireless CCTV field, mainly it has enough bandwidth and transmission rate, and low cost and other technology; If stubbornly HomeRF interference problems, the cost will be relatively improve and use end, however, can not accept the price; Also is to increase the cost, therefore, it is better to developing digital short distance wireless transmission technology.

So-called short-range wireless digital transmission technology, with the analogy technology's biggest difference, lies in the short distance wireless digital transmission using digital image compression technology, and analogy, no; Traditional analog technology if transmission data amount is too large, which accounts for the bandwidth is too large, and once the signal interception, steal can be read easily; However, if the digital image compression technology, the video and data can be compressed more small, not only in the same bandwidth to transmit more data, even if the data to be intercepted, unless the person steal compression techniques have the same solution or add the password, is still won't be able to read.

However, despite the short distance wireless digital transmission technology is quite promising, but it is understood that the price of the current digital short-range wireless products about analog products more than ten times, the price has not yet reached the end generally acceptable standard, short distance wireless digital products to achieve popularization stage, I'm afraid I still need a period of time.

Cable and auxiliary wireless

HomeRF wireless CCTV products at present stage can be divided into wireless camera, wireless image transmission box, and three categories: such as wireless video transmitter

(1) wireless camera

Inside the camera embedded wireless transmitter, is composed of a wireless camera, the video image can be transmitted through built-in transmitter to the wireless image transmission box; But the transmission power of the wireless camera is not high, so can generally be transmitted distance less than 100 meters.

(2) wireless image transmission box

Wireless image transmission box of the received signal can be transmitted to the display screen, general transmission distance less than 500 meters.

(3) wireless video transmitter

If you want to outside the remote manipulation of the camera or video equipment, only the wireless image transmission box is not enough; In order to transmit signals to the farther the distance (5 km), must be equipped with a wireless video transmitter, the transmitted power is stronger, transmission distance can be relatively long.

Short distance wireless transmission by the industry as "the last one inch (the last inch)" industry, means it was usually used in the end, as for the front part still use cable more architecture; In general, wireless transmission products less independent, how to match some cable system, to the overall operation of the function to the limit.