Wireless access Network

Wireless access network According to the advent of the 70 generation of the first generation of systems, that is, a point to the multi-point microwave system, the second generation of the 80 system, that is based on the simulation of cellular systems, with the third generation of the 90 system, that is, based on the digital cellular system. It should be noted that these three-generation systems belong to narrowband wireless access. Therefore, the broadband wireless access network can be used as the fourth generation. Admittedly, the wireless access network can also be classified according to the frequency band and the multiple address mode. And people often only mention by user terminal classification, and the most concern is fixed wireless access network.
Wireless technology for wireless access network
In principle, it can be said that all kinds of existing wireless communication such as single channel system, spread spectrum wireless communication system, microwave system, satellite communication system, mobile communication (including honeycomb and cluster, cordless telephone), etc., can be used as wireless access technology, but they do not have V5 interface, high cost, and can not provide high-quality voice, so , often cannot be used directly for wireless access, but must be modified or specially designed. Therefore, the wireless access network system can be divided into two categories, the first category is a specialized design and manufacture of the system, known as the dedicated wireless local loop, the user is fixed, this type of access network is also known as fixed access networks, Lucent's WSS system, Alcatel A9500 system, Datang's wl-30 system, DSC Company adopts CDMA technology Airspan system is this kind of; the second category, is modified by the original system (simplified), but with the original system is different, for example, wireless access network is all or part of the cable local loop, should have high quality of call, high reliability, confidentiality and strong, and the cost of low , maintenance convenience, and mobile communication quality, reliability, confidentiality and other requirements lower, on the contrary, the system cost high. Admittedly, with the development of mobile phone calls, the quality of the call will also improve, reliability and confidentiality will also be improved.
Whether it is specially designed or modified the original system, the wireless technology used mainly in the following categories:
1, the use of frequency hopping wireless system
The wireless local loop system introduced by Israel Tadira Tele Communications LTD Multi Gain Wireless is the use of FH wireless systems. In early 1996, Guangzhou conducted a demonstration of the Multigain weiewless system.
2, the use of microwave technology
Microwave technology is the first access network technology, the 70 's first generation of wireless access network is the use of microwave technology, first with analog, quickly developed into digital. Commonly used microwave one point multiple access technology. And the form of access network belongs to fixed access networks, the system is connected to the local switch Central station (also called Base station), peripheral station (user station) and relay stations. The Canadian SRT Company's SR500 is the most known of the typical system. Many of these products, such as the Alcatel Company's A9800 system, NEC's Dmmass, Datang's PMP1560, and IRC's June, have been operating at a 15ghz,19ghz,24hgz and higher frequency. System coverage can be 5-60 km (without relay station), can also be 500--600 km (plus relay station). Rural areas, deserts, mountains and islands are useful for such products.
3, the use of satellite communications technology
As we all know, satellite communications are divided into geostationary satellite (GEO) communications, medium-orbit Satellite (MEO) Communications and Leo Communications, while the earth station antenna diameter is divided into a station, B station, C station, E Station and VSAT (Very Small Aperture Termimal), the frequency of satellite communications is C-band (4/6ghz) Ku-band (emphasis is 11/14ghz), Ka-Band (20/30ghz). Satellite communication is used as a relay station, therefore, the use of satellite communications can also constitute a wireless access network, and is a fixed access network, characterized by a large coverage, the distance and climate conditions are not sensitive to the VSAT system for the formation of access network is the most typical, vast main station for the base station, vast remote station role of the user station, There are VSAT systems for public networks in China and special networks. The proximity S1000, launched by the Northern Network, is one of the company's series of access products, which "combines satellite and terrestrial communications systems to provide voice, data and fax services to global users." ”
4, the use of large area system technology
Large-area system technology has the characteristics of large power, large coverage, low system investment and so on, the use of large-area technology wireless access network can be used for population dispersed areas, and the working frequency can be 450MHz, can also be 800MHz, AT&T launched the WSS system using the standard Amps frequency band (824-- 849mhz/869--894mhz) and its extended band, is a wireless access network using large area technology, WSS supports fixed users, but can support mobile users according to user needs.
5 Based on cellular technology
Analog Honeycomb (AMPS, NMT, TACs, etc.) and digital cellular (gsm900,dcs1800, DAMPS, PDC and CDMA one) technology in any of the standards modified and simplified can constitute a wireless access network, can be a direct access to the switching network (PSTN/ISDN) The fixed net, (such as Nokia's GSM WLL system) The user terminal is fixed, the network structure is simple. It can also be connected to a switched network via a mobile switch. The user is a mobile phone or car platform, the network structure is complex, can also be a mixed access network, the user terminal is fixed terminal, can also be mobile phone or car platform. Motorola's CDMA will system, friends of the company's CSW series, is a hybrid access network, the original mobile communication network using fixed wireless terminal fwt (fixed Wireless Terminal) constitute a wireless access network is also a hybrid network, Telular Company in Hunan Hengyang Tel etacs online Open fixed access business is an example.
The wireless access network based on cellular technology has 450nhz,800mhz,900mhz,1800mhz and 1900MHz working frequency. Based on analog network has Ericsson RAS1000 and Motorola's teledensity system, and based on the digital network GSM and CDMA standards are many, especially based on CDMA standard access network especially, such as, DSC Company's Airspan system Litespan system, Multisρan,motorola Company's CDMA would system, Lucent's CDMA Airloop system, QUALCOMM (Qualcomm) Company's Qctel system, China Datang's φdma-wll system and so on. The article says, "Qualcomm Company has Qctel (CDMA) wireless local loop provides high quality level of voice, data and facsimile communication, is the most cost-effective in the same kind of wireless local circuit system." "I believe that Datang's SCDMA-WLL system" is a combination of CDMA technology and modern High-tech integration of the new technology, it has the current international highest frequency spectrum utilization, the lowest emission power characteristics, the system "using smart antenna, (Smarl antenna), synchronous CDMA ( Synchronous CDMA), soft Radio (Software Radio) and other international forefront of communication technology. "SCDMA-WLL system working frequency band for 1785--1805mhz, duplex mode for TDD, multiple access mode for CDMA+SDMA, modulation mode for DQPSK, this system should be the attention of the people in the domestic industry." (☆ Introduction to Programming Network ☆)
6, based on cordless telephone technology
Based on cordless telephone technology, the wireless access network consists of DECT and CT2 in Europe, PACs in the United States and PHS in Japan. As we all know, cordless telephone technology is originally designed for home and office, low emission power, small coverage, the formation of the Wireless access network is a fixed access net. Among them, the use of DECT standards, the 1998 reported that "the current total public wll 31% using DECT". Typical products are teledensity systems developed by Motorola and Bellcore, Ericsson's DRA-1900 system, ADL Cordect system, Siemens Dectlink system, China Huawei ETS1900 System, Alcatel's A9500 system, utstarcom Airstar system, etc., also adopt the CT2 standard, such as the LINKTELCT2 system of rail mobile communication company and the proximity 1800 system of North Network, and adopt PHS standard, Panasonic's AIRSTAR_WLL system, Fujitsu's fwl-p300 type WLL system, Hitachi's PN1000-type WLL system is the PHS standard, our country uses the DECT and the PHS standard to form the access network, because of their large capacity, the DECT can be compatible with the cellular system, But the PHS has the characteristic such as intelligence function. Also, "They can use a wireless band together in one location." However, with the development of wireless access network, the use of GSM and CDMA standards is more and more. And the relative proportion of wireless access network using radiotelephone Technology (Special DECT standard) is reduced.
7, based on cluster technology
The cluster communication system is named Trunking commuication Sgstem by CCIR. China has been translated into a relay system, from 1987 to the conversion of trunking communication system. The main features of the cluster system are: common frequency, common equipment, shared coverage area, shared communication service, cost sharing, interconnection with landline telephone network, data, voice, facsimile and other services, dispatching command and mobile communication, exchange, relay functions and so on. Cluster system launch power, coverage is also large, based on cluster technology, can constitute a fixed wireless access network, can also constitute a mobile wireless networks and hybrid wireless network, Nokia's newly developed 800MHZ actionet simulation cluster system plus the Nokia R72 terminal, can provide voice and data to remote areas, The system becomes a wireless access network. Act10net is Europe's most typical analog cluster system, and Europe's digital trunking system tetra is more global attention, can be sure, based on the TETRA standard wireless access network is more optimistic. The working frequency of the access network based on cluster technology is 8000MHZ, 900MHZ, VHF, UHF and so on.
8, broadband Wireless access network
Wireless access Network is the product of the development of wireless communication technology and exchange technology, as well as the development of communication business. Now, wired ATM technology has developed rapidly into the core technology of broadband switching network, and wireless ATM technology is developing rapidly. While the telecommunications business has been developed from a single voice to voice, data, image and multimedia, the developed countries have not satisfied the narrowband access network, so, broadband wireless access network has become the development direction of wireless access network.