Possibility And Application Design For Jilin Mobile Communication System With LMDS Technology

The introduction of new system and technique brings up a new subject in netdesign and technical adaptive responses to environment. The LMDS (LocalMultipoint Distribution System) technique has some special characteristics, e.g.high bandwidth, high speed, fast network construction, low input cost, permits thecapacity expansion and migration convenience etc. Because the system of LMDS isused primarily in frequency rang of 26GHz and 38 GHz which belongs to the Kafrequency range, the signal ability to penetrate tree, building...etc. obstacles isweaker, and be influenced by environment, especially rain attenuation effect moreseriously. The local FDD frequency boundary planning about 26GHz frequencyrange which has been put into practice on a trial basis is: central station downlink24.507—25.515 GHz , remote station uplink 25.757 —26.765 GHz.The purpose of this discourse is providing theories and practice basis for Jilinto decide whether introduce the LMDS system as the" the last one kilometer"access transmission way. So it certainly has some realistic meaning and practicalvalue.This subject is a business experiment ,aiming to test possibility of LMDSusage in the Jilin weather environment and actual effect on supporting Jilinrelated business .There are four problems should be resolved through the businessexperiment ,e.g. evaluate the rain attenuation influence on LMDS under the Jilinweather condition ,attain the conclusion whether the LMDS system is adapted forJilin ;Explore business mode how to make use of the LMDS technique andtechnique business model, in order to provide basis for Jilin judgment whetherregard LMDS as the means in next business development; Research and putsforward LMDS service quantity request and test method for accumulatingmaintenance and developments experience in the days to come.Through analyzing the LMDS access method, experiment equipment function,experiment net design and design project ,we will set up a reasonable net, andbasing on the experiment net , study the rain attenuation influence on the system.In this experiment, according to the china mobile enterprise standard《26G Local Multipoint Distribution System ( LMDS) equipments testnorm 》,we test the ability of LMDS, the function of port to swallow and vomit,IP pack deliver postpone, the lose ratio of IP pack frame etc ,every index is up tostandard.There are mostly two factors that result in wireless path decline, i.e. multipathdecline and the rain attenuation .For the path that work below 10GHz range, Themultipath decline occupies the predominant position. The path working in 10GHz—17GHz, need to be considered the multipath decline and the rain attenuation ; thepath working above 17GHz then should primarily considers the fading that beresulted from rainfall; LMDS work in 26 GHz, so in program design process, itmust be considered the influence that the rain attenuation results in.When design the LMDS system, we sufficiency considered the influence ofrain attenuation, and adopted the valid anti-rain attenuation measure. The functionof the A7390 receives—transmitter is very excellent, its receives electrical levelcan attain-83 dBm and -81 dBm at the BER=10-6 up—downlink threshold, betterthan profession standard.(-82 dBm and -76 dBm).If adopt the standard antenna, thesystem gain can attain 148 dB; If adopt high gain antenna, the system gain canattain 160 dB. For the decline that resulted by the rain attenuation, in order to satisfy thetransmitting power request corresponding with the different communicationdistance and the different region rain fading, the system need to provide enoughpower to compensate .The system of A7390 LMDS can provide automatic gaincontrol scope over 40dB, well higher than the 35dB that information industrydepartment made, and fully be approved in the test.. In order to satisfy the transmitting power request corresponding with thedifferent communication distance and the different region rain fading, the A7390LMDS system support the function of automatic transmitter power control( ATPC).The system of A7390 LMDS execute the ATPC in uplink path .Becausethe lower C/ N can't guarantee the BER requests, the higher C/ N lead-in signalinterference to neighbor sectors, the ATPC can guarantee the system work in theideal C/N index .The ATPC of A7390 can support the slow loop adjustment andthe fast loop adjustment. The function of slow loop adjustment acts on the whole cell .In order toguarantee the power that different terminal requires to arrive the base stationconsistent , the base station measures the receiver power coming from everyterminal , and request each terminal to adjust itself output power .Namely ,the basestation control each terminal ATPC ,and guarantee the receiver lever consistentthrough adjusting the terminal C/N index .The function of fast loop adjustmentworks in open mode .In 26GHz ,the attenuation caused by the rainfall acts on theuplink and downlink at the same time .In each frame (6.375 ms), the NT measuresitself receive electric lever , calculate the difference from the last measuredvalue ,and increase the output power to compensate the rain attenuation accordingto the difference at the same time .The output power of NT can change 8 dB mostlyin each frame , namely the speed of power adjustment is higher than 1000 dB/ s. According to the statistical rainfall over a long period of time, the ITU-Rdivides the world different rain area in terms to the different strength ofrainfall .The ITU-R recommended the detailed predicted model of rainfallattenuation, making the path deviser estimate the possible attenuation depth forsome usability and particular path, thereby leave enough stores of attenuation whencalculate the path . Seen from the usability of path, the influence to the path of heavy rain that lessappears is larger than the continual light rain. At the same time, the natural lightrain distributes more widely and the volume of each path is almost same .However,the heavy rain( the influence is larger) regionalism is very strong .Therefore, incalculating the rain attenuation ,taking into account of the difference of rainfall inwireless path ,the ITU-R recommend that the total path length should be revisedfor" valid path length" .Valid path length is a path whose length is imaginable ,eachpoint on this path is considered to have a certain same rain strength . The difference between the normal receiver electric lever and exasperatereceive threshold electric lever , we call it as smooth attenuation stores .For thesystem of LMDS working in 26 GHz, the value is remained in advance in order toresist the rain attenuation. Higher store value should be needed by the higherusability. When the usability of the wireless path is 99.99%, BER=10-6, end station isplaced in coverage scope , closer the distance between the end station and the basestation is ,the wireless path usability between them is more higher than99.99% ;Whereas, when the end station is placed beyond coverage scope, farer thedistance between the end station and the base station is ,the wireless path usabilitybetween them will be lower than 99.99%, and also is to say, while meeting strongrainfall, the ratio of the path breaks off will increase correspondingly .TheChangChun belongs the K area , its strength of rainfall is 42 mms/ hr in annual0.01% time. In actual engineering application , when the annual rainfall strengthcan be acquired from the statistic of the native weather section, regard it as toallow .When plan the network ,we should consider the rain quantity and the pathusability etc. every kind of factors, and confirm the distance upper limit toovercome the influence of rain attenuation ,then guaranteed the system of LMDScan provide reliable, fast telecommunication class broadband business for thecustomer .The transport distance of LMDS in ChangChun shouldn't over 5-6kilometers , under such distance ,the LMDS system can guarantee the businessusability . Because the final purpose of this subject is to use LMDS system as the methodof supporting business development, this discourse also exploratory design the netmode to support all classes of business. As the means of access , LMDS can provide differ interference manner andtransport speed that required by the native ATM business, VoD, VoIP, MeetingTelevision business, Audio of Order business, Super-speed Internet business,VLAN, VPN, Long —distance medical treatment, Long —distance education,Frame relay business ,Circuit simulate business etc. every business .In lessonprocess ,we analyze the interference of the LMDS terminal and design the networkstructure . For example ,if the base station need higher capacity to connect with eachother , the ATM mode should be adopt .The solution project of LMDS accesscompletely satisfy the requirement of the current base station to connect with eachother ,and can provide vivid, dependable starriness structure for the GSM basestation . In IP rent business application, the LMDS NT provides 10M BaseT(2...