Five kinds of broadband wireless access Competitions

With the development of wireless networks, people have higher and higher requirements on networks. Broadband wireless access technology emerged. As the name suggests, the broadband wireless access technology improves the speed and capacity of the wireless network. The following describes the comparison of the Five broadband wireless access technologies.

Broadband wireless access technology represents a new trend that cannot be ignored in the broadband access technology. It not only provides fast network connection, simple maintenance, and low cost when users are relatively confidential, in addition, it has changed the traditional concept of local telecom business and is most suitable for new telecom competitors to carry out effective competition. It can also be an important supplement for cable access of telecom companies. There are currently several popular Broadband Wireless Access Technologies.

It is used for MMDS systems at 2.5 GHz/GHz. It uses advanced voofdm technology to achieve broadband wireless access communication, and uses "multi-path" in buildings to achieve data access at a transmission rate of up to 22 Mbit/s with a single-carrier bandwidth of 6 MHz, the spectrum efficiency is high. The communication probability in the 90% GHz band can reach 80%, and the communication probability in the GHz band can reach more.

A high-frequency microwave SDHIP ring system. In the past, many microwave SDH devices were used in point-to-point microwave transmission circuits. Now with the advancement of technology, some companies have launched microwave SDH Bidirectional Ring Network, with self-healing function, consistent with the self-healing characteristics of the Optical Fiber Ring, integrated ADM, using a series of Modem, to achieve QPSK-256QAM programmable, there are a variety of interfaces (G.703, STM-1, E3/T3, E1, Ethernet 10Base-T/100Base-T ). At the same time, the engineering installation of miniaturized structural equipment is more convenient than that of microwave equipment in the past, and in the case of frequency shortage, this equipment can work at 13 GHz, 15 GHz, 18 GHz, and 23 GHz frequencies. in the construction of a man, it can avoid fierce competition for 3.5 GHz/26 GHz wireless access frequencies, supports 8 * 155M bandwidth.

Local multi-point distribution service LMDS. It operates at 20 GHz ~ In the 40 GHz band, the transmission capacity can be compared with the optical fiber, and it also has the advantages of broadband wireless access communication, such as economic and easy to implement. Based on MPEG technology, LMDS is developed from the microwave video distribution system (MVDS. A complete LMDS system consists of four parts: local optical fiber backbone network, network operation center (NOC), base station system, and user terminal equipment (CPE ). LMDS features that the bandwidth can be compared with the optical fiber to achieve broadband wireless access to the "Optical Fiber" building. The available frequency band is at least 1 GHz. Compared with other access technologies, LMDS is a flexible Replacement Technology for the last kilometer of optical fiber. The optical fiber transmission rate is as high as Gb, while the LMDS transmission rate can reach 155 Mbit/s, ranking second in stability; LMDS supports all major audio and data transmission standards. LMDS work in millimeter bands, 20 GHz ~ For 40 GHz frequencies, the licensed frequencies are 24 GHz, 28 GHz, 31 GHz, and 38 GHz. Among them, 28 GHz has more licenses, and the frequency band has a relatively loose spectrum range, it has the potential to provide multiple services.

Currently, the fixed broadband wireless access system uses three types of air interfaces: IP address-based, ATM cell-based, and TDMA-based time slot allocation. It has a theoretical value and engineering implementation value for modulation and demodulation, error correction, receiving sensitivity, spectrum efficiency, and other indicators. Different modulation methods generally correspond to different error correction methods. The error correction performance in the broadband wireless access communication system directly affects the overall system performance, this is especially important when there are multiple organizational units. However, it is undeniable that the correspondence between the modulation method and the Error Correction Method in the actual construction of the network is greatly different from the theoretical value. Why is there a big difference between theory and engineering? The main reason is that it is impossible for any device to achieve the ideal spectrum efficiency when the out-of-band radiation is restricted, this is because you must add a vro to prevent the system from interfering with the neighboring system. At present, there is a general problem of exaggerating the spread of spectrum utilization, and there is a problem of inconsistent definitions. The values obtained from different definitions sometimes vary greatly, pay attention to this when selecting network devices, so that the selected devices cannot meet the requirements.

In terms of service bearer, the business of the 3.5g system can basically be divided into two categories: the basic services of TDM circuit based on transparent transmission (base station transmission link and leased line services) and IP services, broadband Wireless Access devices generally support both services, so that operators can provide differentiated services for users.

For network management, authentication, and billing, most network management systems of broadband wireless access devices use the SNMP protocol platform, and user authentication and billing are basically completed by third-party devices, broadband Wireless Access devices can provide as many parameters as possible for devices to access and use.

Due to resource restrictions, transmission characteristics of the GHz equipment, and antenna technology, it is difficult for a carrier to organize multi-zone systems in the same city in the GHz band, unless the base station has a greater degree of freedom of choice, therefore, you must carefully consider the network planning, especially the selected devices must have high performance indicators.