Advantages of 5GHz Band and its broadband access scheme

Absrtact: This paper makes a systematic overview of the development trend of wireless broadband access, focuses on the analysis and description of the technical advantages of the 5GHz band, and introduces the technical index and key technology of a 5GHZ wireless broadband access scheme, and finally forecasts the application prospect of 5GHZ Wireless broadband Connection network.
The development trend of wireless access
Will compete with wired access to the market: where the cable is difficult to reach, it can be used as the extension and supplement of the cable, in the newly-built industrial park and residential district, it can be used as the emergency means and alternative means of the wired communication; the towns with difficult construction of underground cables become powerful rivals of wired access, The target of the competition will be the number of end users, currently less than 1:100 of wireless access users and wired access users. It is expected to reach 1:10 in two years, and may reach 1:3 in 5 years, that is, wireless access is entering a fast-growing phase.
High-frequency segment, wide bandwidth, high speed, high spectrum utilization: With the diversification of user business, especially broadband, the information rate of the past Kbps or more than 10 kbps is not enough, many users require dozens of Mbps information rate. To improve the information rate, in addition to the use of advanced duplex technology, coding technology and modulation technology, the most basic is the wider channel bandwidth, the corresponding need to occupy a higher frequency band. A typical example is the hundreds of MHz band. Channel bandwidth is only a few khz to dozens of khz, the information rate is below dozens of kbps, while at a few GHz band bandwidth can reach a few MHz to more than 10 MHz, the information rate can be up to several Mbps to dozens of Mbps, if you use the millimeter band dozens of GHz, Channel bandwidth is as high as 100 MHz to more than 200 MHz, and the information rate is up to 155Mbps base to hundreds of Mbps. Radio frequency spectrum is a very precious scarce resource, and increasing the utilization rate of spectrum is a resource saving.
Provide IP (Internet Protocol) transport services: IP Services for wireless access network requirements are real-time fast, broadband multimedia, up/down asymmetry, easy to expand, etc., the Internet Information transmission is grouped, The transmission mode is defined by TCP/IP (Transmission Control Protocol/internet) to stipulate how packets are layered and grouped, how to reassemble, and how to transmit on the channel. TCP/IP is divided into the link layer, the Internet layer (IP layer), the Transport Layer (TCP layer) and application layer, TCP for, send at both ends to provide a duplex transmission protocol, IP for different computer networks to provide interconnection protocol. Wireless access network should be in the transmission and interface to adapt to the needs of IP services.
Adapt to a variety of demanding needs of different users: can be summed up in the telephone, video, high-speed data integrated access; small risk investment, low start-up cost, adapt to the initial user less environment: easy expansion, expand coverage area, adapt to the rapid increase in user demand; simple, reliable, fool, reduce maintenance costs; loading, dismantling, It is simple and quick to guarantee the investment does not precipitate; Flexible interface capabilities such as V5, ATM, and Ethernet interfaces to connect to different networks; ability to resist harsh environments, such as outdoor work, not affected by rain and decay.
The technology of wireless access to integration, broad-band, intelligent Direction: Integration enables users to achieve two-way communications, broadband enables users to freely transmit dynamic video, high-speed surfing on the Internet, intelligent system can get more and better functions, software radio technology is a powerful tool for intelligent.
5GHz is the golden Band of broadband wireless technology
Fixed wireless access to a wide range of working frequencies. Currently used are: 450MHz Band of "Wireless Nonghua" : Point-to-Point microwave communication at 1.5GHz Band, wireless spread spectrum communication in 2.4GHz Band, digital bidirectional MMDS (multi-channel distribution system) in 2.5~2.7ghz Band, 3.5GHz frequency wll (wireless local loop), point-to-point wireless spread spectrum communication in 5.725~5.85ghz frequency band, etc. Possible development of the frequency bands are: 5Hz Band of broadband wireless access 10GHz, 21GHz, 24GHz, 26GHz, 28GHz, 31GHz, 38GHz frequency band of LMDS (local multi-point distribution business) and so on. In 2000 more manufacturers launched the 800nm-band Broadband Wireless Infrared optical access system, become a veritable "wireless fiber."
Generally speaking, the lower the frequency band, the lower the transmission rate of information. Take 3.5GHz frequency band as an example, according to the national communication Industry standard "access network technology requirements -3.5ghz Fixed wireless access" Regulation, the uplink band for the 3400~3430mhz, downlink frequency for the 3500~3530mhz band interval of 175, 3.5, 7 and 14MHz four kinds: frequency Division Duplex When the multiplex/Multiple access method adopts TDM/TDMA, Compared to the rate at which the channel interval is 3.5MHz, if the use of QPSK or its equivalent modulation of the lowest 4Mbps, 16QAM or its equivalent modulation mode of the lowest can be transmitted 8Mbps, the use of 64QAM or its equivalent modulation mode when the lowest can be transmitted 12Mbps; But the more complex the modulation, the more expensive the cost The lower the sensitivity of the receiver, the higher the BER and the lower the anti-interference ability, the higher transmitting power is needed to maintain the transmission distance. At present, in the 3.5GHz band, according to the performance price ratio arrangement, most users choose 3.5MHz bandwidth transmission 4Mbps rate, more suitable for a small number of users narrow-band low speed wireless access to use.
In the high-frequency segment, the country has not yet developed relevant spectrum specifications, to 26GHz band as an example, Uplink frequency is 25.557~26.061ghz, downlink frequency is 24.549~25.053ghz, uplink channel interval is 10MHz, downlink channel interval is 56MHz, frequency division duplex is used, and the transmission capacity of uplink per channel is qpsk13.3mbps according to different modulation modes respectively. 16QAM 26.7Mbps, 64QAM 40Mbps, downlink per channel transmission capacity of qpsk66.5mbps, 16QAM 133.5Mbps, 64qam200.0mbps, the more complex the modulation, the lower the receiving sensitivity, the larger the required transmitting power, and the communication distance is generally not more than 3 km. In the band above 20GHz, rain decline and multipath impact are more serious, the rain in the south is almost inevitable rain failure of the calculation of complex and inaccurate, and even the loss of leaves can not be ignored, coupled with technical difficulties, high equipment costs, large range, large-scale investment in the wireless access market is still difficult. As for the Wireless optical communication system, it is not suitable for use in rain, snow, dense fog and dust weather, it is obvious that the wireless access area will not share much.
If you choose between transmission bandwidth, transmission rate, transmission distance, transmission quality, construction scale, investment cost and operating profit, the 5GHz band is the most expensive gold band for fixed wireless access in today's technical conditions.
In January 1997, the Federal Communications Commission (FCC) announced the distribution of three 100MHz bands in the 5GHz band, used as a u-nii (national information infrastructure without a license) to provide fast-opening high-speed wireless data communications. Three 100MHz Band is: 5.15~5.25ghz, stipulates that its EIRP is not suitable for indoor wireless communication, 5.25~5.35ghz, the EIRP is not more than 30dBm, suitable for medium distance communication. Usually people choose 5.725~5.825ghz for broadband wireless access in the community to get a better performance-price ratio. The FCC sets a channel interval of 15MHz, with few other restrictions, to encourage manufacturers and operators to innovate and make limited spectrum resources more efficient to use. 5GHz Band for users in the range of 5-10 km to establish broadband wireless access to provide convenient, generally do not need to consider the impact of rain, dust and leaves, it is generally believed that 5GHz in the Access field will create huge social and economic benefits.
China has not introduced the frequency of the 5GHz band plan, but the Ministry of Information Industry Radio Bureau is very concerned about the development and utilization of this band, in order to promote the fixed wireless access business competition and development, it is proposed to improve the basic research work, as soon as possible to develop 5.725~5.825ghz broadband wireless access system technology test. It can be affirmed that the trial trial of 5.725~5.825ghz band will open up a new world for our country's broadband wireless access.
5GHz Broadband Wireless Access scheme
Because the FCC to the 5GHz band of specific provisions and restrictions are relatively small, this gives the development of a more free creative space, you can choose a variety of network structure and technical system. But smart makers use their own fantastic ideas to create some unique principles, technology and technology, break through some contradictions of focus, at a higher level of integration, balance and compromise, rather than the pursuit of high, fine, sharp, new, so as to achieve higher performance price ratio and customer satisfaction.