参 考 文 献
[1] 樊昌信等. 通信原理(第四版). 北京：国防工业出版社，1995.10 [2] 沈振元等. 通信系统原理. 西安：西安电子科技大学出版社，1993.10
[3] John G.. Proakis. Digital Communications (Fourth Edition). 北京：电子工业出版社，2003.1 [4]A.M.Sayeed and B.Aazhang, “Joint multipath-doppler diversity in mobile wireless communications,”IEEE Trans.Commun.,vol47,pp23-123,Jan1999 [5] 李文海著 数字通信技术. 北京：人民邮电出版社，1991 [6] 吴伟陵等著. 移动通信原理. 北京：电子工业出版社，2005 [7] 吴玲达等著.计算机通信.长沙：国防工业出版社，2001
[8]张平 等编著．MATALAB基础与应用简明教程． 北京航空航天大学出版社2001年1月第一版 [9]吴大正，高西全，等编著 ．MATALAB及在电子信息课程中的应用．电子工业出版社． [10]彭林等编著．第三代移动通信技术．电子工业出版社．2003年2月第1版 [11]朱洪波、等.“微蜂窝多径散射环境中的电波传播特性分析” 电波科学学
报，1997,12(3)；321-32
[12]黄文梅，杨勇，熊桂林系统分析与仿真国，防科技大学出版社，1999
41
附 录
中英文翻译
1.英文原文
1）.Wireless channel characteristic
The different frequency band radio wave, its dissemination way and the characteristic are not same. Said to the work in VHF and the UHF frequency band mobile communication that, the radio wave propagation way mainly is the sky wave, namely direct wave, refracted wave, scattered wave as well as their bound wave. In the land migration system, the travelling carriage is in the city architectural complex or is in the terrain complex region, its antenna will receive the signal which will transmit from the multi- strip way, again will add travelling carriage itself the movement, will cause between the travelling carriage and the base depot wireless channel is changeable also controls with difficulty.
Compares with other communications channels, moves the channel is the most complex one kind. For example, in the simulation wired channel the typical signal to noise ratio is 46dB approximately, in other words, the signal level must noise level be higher than 40,000 times.Moreover said to the wired channel that, its transmission quality is may control. Through the choice appropriate material and the careful processing, may guarantee in the wired transmission system has a relatively stable electrical environment. In the wire command link,the signal to noise ratio undulation usually does not surpass l 2dB.Only then after some section of lines moved quite long period of time,because the line damage brings gradually the loss also permitted reaches 101 15dB, but in this kind of situation, needed to carry on to this section of line renews. With this , in the land migration wireless channel the signal strength reduces namely the so-called decline is suddenly occurs frequently, declines the depth to be possible to reach 30dB. In the urban environment, on a fast travel vehicles travelling carriage receive signal may reach dozens of in a second within remarkable decline. This kind of fading serious worsening receive signal quality, affects the correspondence reliability. In the honeycomb migration environment, the same frequency disturbance is a question which must consider. When has the decline, must receive perhaps the signal the unwanted signal which comes the same frequency plot base depot also must be weaker than, the receiver can lock on the rub-out signal. The simulation mobile communication uses the frequency modulation mark much, the frequency modulation way capture effect has the certain inhibitory action to the same frequency disturbance. But the fading can remarkably change the
42
frequency-modulated signal characteristic, slackens its capture effect. As for the digital transmission that, will decline causes a bit error rate (BER) the big increase. Moves the channel with must to move the point-to-point wireless sentiment road to compare, the signalling bit string former latter is by mistake higher than 106 times. With this compared, in the wired channel will be able the very good work pronunciation encoder, the modem and the synchronizer the operating performance can worsen greatly in the motion environment. Moves the channel the fading characteristic to be decided by the radio broadcast environment. The different environment, its dissemination characteristic also is different. For example, has many high-rise constructions the big cities and the smooth open countryside compares,its dissemination environment has is very greatly different, two motion channels characteristic also greatly has the difference. But disseminates environment itself is quite complex, this causes the motion channel characteristic also is extremely complex. Complex, the bad dissemination condition is moves the channel the characteristic,this is by carries on wireless correspondence this way itself in the movement to decide. As for the mobile communication that, the bad channel characteristic is a question which cannot be avoided. Must transmission quality which the maintenance may accept under such dissemination condition, must use the adverse effect which each kind of technical measure counterbalances declines. This is each kind of anti- decline technology, including the diversity, the wide frequency/frequency-hopping, equilibrium, interweaves with the error correction code and so on. Moreover, the signalling way, like the modulation way, also must have the certain adaptiveness to in the channel decline. Many anti- declines practical technologies successfully have applied in the simulation wireless system. In the numeral mobile communication, develops many new technologies in view of the digital transmission characteristic. Each kind of anti- decline technology and the digital transmission technology research to develops the numeral mobile communication system is extremely important. 2）.Wireless channel model
The research and the development migration center digital transmission technology first step of work is knows motion channel itself the characteristic. In fact, moves the channel to become many theoretical analyses and the scene actual topic, and has obtained many concerns its characteristic result. Some may produce the precise mathematics description, another some then produces the statistical model. However, because moves the channel the complexity, still some many treated the research topic. For example, is impossible with the sole mathematical model to describe all motion environment. Thus, in different local, different city motion channel characteristic actually how, only then determined in these environment with in the field intensity actual gain data. To moves the
43
channel to conduct the research the essential method to have three kinds:
(1) the theoretical analysis, namely uses electricity the magnetic field theory or the statistical theory analysis electric wave in the motion environment center dissemination characteristic, and describes the motion channel with each mathematical model. Often must propose some supposition conditions cause the channel mathematical model to simplify, therefore the mathematical model to the channel description all is approximate. Even if like this, the channel theoretical model to the people knew still might play the instruction role with the research migration channel.
(2) scene radio wave propagation actual, namely in the different dissemination environment, performs the radio wave propagation actual experiment. Test parameter including receive signal scope, time delay as well as other reflection channel characteristics parameters. Carries on the statistical analysis to the measured data, may obtain some useful results. As a result of the motion environment multiplicity, the scene actual moves continuously as the research the channel the important method.
(3) moves the channel the computer simulation, was in recent years the research technique which appeared newly along with the computer technology development. As mentioned above, any theoretical analysis, all must suppose some simplification conditions, but actual moves the dissemination environment dryly changes Wan Hua, this has limited the theory result application scope. Scene actual, is time-consuming,takes the trouble, and also is aims at some specific environment to carry on. The computer under the hardware support, has the very strong computation ability, can nimbly fast simulate each kind of motion environment. Thus, the computer simulation more and more becomes a research migration sentiment important method.
It can be said that, the above three research technique is complements one another. In many actual research works, these methods use in studying the advancement the different stage. In the motion environment the radio wave propagation characteristic research result often uses the following two ways to produce: First, to moves in the environment the radio wave propagation characteristic to produce some kind of statistical description. For example, the theoretical analysis and the actual test result indicated that, receives the signal in the motion environment the scope to conform to Rayleigh in the majority situation (Rayleigh) to distribute. In some situations, then conforms to Lies (Rice) to distribute. The electric wave fading characteristic statistics rule, has provided the basic basis for the research migration channel anti- decline technology. Second, establishes the radio wave propagation model. The model may include the graph, the approximate calculation formula and so on. The modelling also more and more was in recent years popular on the computer. May
44
carries on the forecast using the radio wave propagation model to radio wave in spreading process each kind of disturbance and the loss, serves directly for the systems engineering design. Should note to, as a result of the motion environment complexity, is impossible to establish the sole model. The different model is induces from in the different dissemination environment measured data but obtains, all has the certain applicable scope. When carries on the systems engineering design, the model choice is very important, sometimes the different model can produce the different result. Therefore, the dissemination environment to moves the channel characteristic to play the key role.Moreover, moves the channel characteristic also to receive the system operating frequency and the travelling carriage movement condition influence. In the same area, the operating frequency is different,receives the signal fading condition to have the difference. But static the motion environment question and the high speed movement vehicles which faces with the low speed movement vehicles has the very big difference. Generally speaking, moves the communications system design question for the solution, must clarify three questions: The radio signal in moves the change which in the channel possibly occurs as well as has these changes reasons; Regarding the specific wireless transmission technology, these changes to transmits the quality and the system performance has any influence; Which methods has or the technology may supply to use for to overcome these is disadvantageous.
3）.Channel modelling simulation technology development survey
The mobile communication system performance mainly receives the wireless channel characteristic restriction. Between the transmitter private receiver path of propagation general distribution has the complex terrain features, its channel the right and wrong is often fixed and Has complex when changes radio wave propagation characteristic, thus has created the channel analysis and the dissemination forecast difficulty. Complicates day by day along with the communications system, the wireless channel modelling and the simulation have the more and more vital significance regarding the modern numeral mobile communication system research and development. Along with mobile communication user's increasing, divides to the mobile communication frequency band has not changed actually, in order to effectively uses the frequency band by to support more users, in the mobile communication the honeycomb cover radius was more and more small, has experienced from the big area system to the great plot, the micro plot as well as slightly the plot evolution. The future person-to-person communication system, the base depot antenna almost will be the street light altitude, the propagation distance in Ikm. According to the honeycomb cover radius size, the modern wireless mobile communication may divide into the great
45