Comprehensive analysis of the application and development of wireless access technology

Wireless access technology is currently one of the most popular access technologies, and its share in the market is also very large. At the same time, many cities have applied wireless networks, it brings users a good network environment.

1. What is MMDS?

Now the wireless access technology has sprung up as a wide variety, what GPRS technology, CDMA technology, DS-CDMA technology, EDGE technology, LMDS Technology, etc, these technologies can provide users with high-speed wireless communication services. In addition to the communication technologies described above, the MMDS technology introduced to you is actually a wireless communication technology. The full name of this technology is Microwave Multipoint Distribution Systems, the Chinese meaning is the wireless microwave multi-point distributed system technology. This technology is a new transmission technology developed recently to transmit cable TV signals through wireless microwave. This technology not only facilitates installation and debugging, moreover, the system composed of this technology is light in weight, small in size, and has a small footprint. It is suitable for areas not covered by cable TV in small and medium-sized cities or suburbs. This technology is an image distribution Transmission Technology Based on line of sight transmission. its normal operating frequency is generally 2.5 GHz-3.5 GHz, this technology can cover a large area without installing too many roof devices, therefore, using this technology, people can transmit more than 100 digital TV signals to users within 50 kilometers of the reflected antenna. The service area of a tower can cover a medium-sized city and control upstream and downstream data streams. Now MMDS uses traditional modulation technology, but the future technology will be based on VOFDMVector Orthogonal Frequency Division Multiplexing). The receiving end is combined with the reflected signal to generate a stronger signal. This low-cost technology is often used for wireless access technology for small enterprises away from service centers. It is sometimes called WDSL or broadband wireless technology.

MMDS is a new wireless broadband data access technology. It provides a connection between mobile users and data networks to provide mobile users with high-speed wireless access technical services. In terms of system upgrading, MMDS technology will be easier to upgrade than other communication technologies. The most notable feature of MMDS is that the Local Vibration points of each frequency drop can be different, and the user can choose the frequency point, that is, the multi-point Local Vibration. Therefore, the signal after the frequency change of each frequency drop, it can be in the VHFI and Ⅲ frequencies of standard TV channels, supplemented A and B frequencies, and 13 ~ 45CH frequency band), which is of great benefit for users to avoid the channels occupied by local open-circuit wireless TVs or CATV. Early MMDS was mainly a unidirectional non-Distributed Image Service transmission system. Now you can send and receive data signals at a faster rate than T-1. MMDS does not need to deal with local telephone and cable telecom service companies too much. These companies are generally reluctant to cooperate and do not want to open their own networks. In MMDS systems, Ethernet is usually used to connect to a wireless Modem.

MMDS technology can provide users with a variety of business functions, including point-to-point connection-oriented data services, point-to-point multi-point services, and point-to-point non-connection network services, point-to-point connection-oriented data services send multi-group services between two or more users. This service requires working programs such as establishing connections, data transmission, and connection release; point-to-Point businesses can transmit a single message to multiple users according to the requirements of a service requestor. This business can also be divided into point-to-point multi-channel broadcast businesses and point-to-point group calling businesses; data groups in point-to-point and connectionless network services are independent of each other. Information Transmission between users does not require end-to-end calling to establish a program, and group transmission does not have a logical connection, the delivery of the group is not guaranteed. In addition to point-to-point and point-to-point data services, MMDS also supports user terminal services, supplementary services, GSM short message services, and various GPRS telecom services.

Of course, MMDS is also inadequate. This technology is congested during communication, and the signal quality is easily affected by weather changes. The available frequency band is also not wide enough and cannot exceed 200 MHz at most. MMDS is still available in the market because DSL and Cable Modem cannot provide services to all users. However, it is not easy to buy the MMDS service because the service supplier is waiting for a new generation of devices to be put on the market, many manufacturers, including ADCs, Cisco, and Vyyo, that produce the next-generation MMDS device are working to eliminate the current MMDS line-based restrictions. By then, MMDS technology will become more mature. Although many cities have already used optical fiber/cable hybrid networks to cover large and medium-scale cities, for the vast majority of villages, towns, and villages, especially mountainous areas with complex terrain and remote and poor areas, it is unrealistic to adopt a cable/cable hybrid network, and the MMDS system can easily achieve the connection of cable TV. Therefore, the emergence of MMDS technology is imperative.

Ii. What are MMDS features?

With the increasing number of communications and the increasing requirements of people's communication capabilities, the demand for communications around the world is increasing at a rate of nearly 20%-30% every year, and there are no signs of slowing down so far, user-side terminals are also growing rapidly, and wireless access technologies for individual users and unit users are rapidly converging on broadband. Obviously, broadband access networks will become the main technology trend of wireless access technology development in the future. As a new broadband technology, MMDS is becoming a practical broadband choice with its own characteristics:

1. MMDS uses the latest source code and channel coding technology for digital signal transmission. At the same time, the latest modulation technology is introduced in the MMDS system, this will compress the spectrum of digital signals, greatly improve the channel utilization, and ultimately improve the comprehensive utilization of Communication Power and spectrum;

2. Compared with the traditional AML and FM microwave transmission modes, the MMDS working frequency band is slightly lower than that of the ground television broadcasting, MMDS has a weak diffraction capability. Buildings on various floors absorb large amounts of data and reflect weak data. In addition, MMDS technical systems require low equipment costs, in particular, MMDS downstream inverters are more miniaturized, integrated, and in mass production, displaying their unique charm of superior performance/price ratio. Therefore, MMDS technology is suitable for receiving large, medium, and individual users, no need to lay optical cables, which consumes a lot of financial resources and is easy to operate;

3. The MMDS wireless transmission network is the same as the cable TV optical fiber network. The technology of adding/unscrambling can be used to realize the addressable Charging System and the computer user management system. Like optical fiber networks, the MMDS wireless transmission network can transmit traffic and data information in two directions, such as on-demand videos and video conferences. Digital Compression Technology eventually solves the defect of low MMDS channel capacity. You can set ~ 10 channels of TV programs are compressed and transmitted in a simulated 8 MHz channel.

4. Because MMDS communication technology uses digital filtering and digital storage, a simple method can be used to eliminate noise accompanied by Image Transmission and improve the signal-to-noise ratio of image transmission. In addition, the digital filtering and digital storage methods used by MMDS can also easily achieve adaptive two-dimensional and three-dimensional brightness separation to completely eliminate brightness interference, and other measures to improve image quality, in this way, the image quality for transmitting digital TV signals through the MMDS system is much higher than that for transmitting signals through normal means.