The primary method of wireless transmission is microwave transmission. When it comes to monitoring image transmission, the two main categories are analog microwave transmission and digital microwave transmission. Now, let's take a closer look at these methods.
Analog microwave transmission operates within different frequency bands, such as L-band, S-band, and Ku-band. In locations with minimal interference, L-band and S-band are suitable, offering cost-effective solutions. However, areas with more complex environments or significant interference require transmission in the Ku-band, ensuring reliable video and audio transmission between two points. It's important to note that analog microwave transmission operates on a line-of-sight basis and cannot function when obstructed. In case of blockage, ultrashort wave technology must be utilized, although its transmission range is limited, and it comes with a higher cost. Analog microwave utilizes analog frequency modulation, which is influenced by the surrounding environment and weather conditions. To exert control and command over the system, a wireless command control system needs to be incorporated, resulting in two separate systems for video and command functions. When there are fewer monitoring points and longer transmission distances, analog microwave can be considered, as long as the appropriate frequency band is chosen based on the on-site environment to ensure stable image transmission. It is crucial to implement lightning protection and waterproof measures for the analog microwave system to maintain its stability. Advantages of analog microwave include ease of construction, simple installation, and long-distance transmission. However, it has some drawbacks such as complex debugging, susceptibility to environmental and climatic factors, inability to transmit multiple signals simultaneously, and a higher vulnerability to lightning strikes.
The primary components of a digital microwave system include a wireless network bridge and a codec (video server), which work together to enable long-distance transmission of images. Typically, a point-to-point network is established using the network bridge, where the analog video image is converted into a network signal by an encoder. Subsequently, the wireless network bridge transmits the network signal, and at the receiving end, the network signal is restored to its original analog video format through a decoder (either hardware or software decoding). This system allows for simultaneous transmission of video, audio, data, and images, with the number of channels and image quality dependent on the network bandwidth available. Digital microwave offers several advantages such as its resilience to environmental conditions, support for relay transmission, and long-distance capabilities. However, it may require meticulous debugging and can be affected by limitations in network bandwidth.
The analog microwave surveillance camera may offer superior image quality compared to its digital counterpart, but it is more susceptible to environmental and weather conditions. On the other hand, the digital microwave camera has a smaller environmental impact, but it faces challenges in wireless transmission bandwidth, which makes it difficult to transmit a large number of images. Ultimately, the choice between the two systems depends on the specific engineering environment and the unique needs of the user. Both systems have their pros and cons, and it is essential to consider these factors carefully before deciding which one to use.
CDMA network transmission in domestic networks is relatively slow, with a maximum speed of only 2.5G. This makes it challenging to transmit real-time continuous images through the current CDMA network in China, and the network can only be used to transfer pictures. If real-time video images are to be transmitted, then one has to either shrink the size of the video or increase the network bandwidth. However, in the future, network transmission will definitely be the norm, as it covers a wider area and isn't limited by distance.
Satellite transmission, also referred to as GPRS system, is primarily used for satellite positioning. The bandwidth plays a significant role in this type of transmission. Nowadays, many businesses use satellite positioning systems to track their assets' specific geographical locations. It includes tracking the locations of cash transport vehicles, mobile phones, and more. However, with advancements in technology, if the bandwidth can be increased, live images can also be transmitted in real-time, opening the doors for numerous applications.