通信毕设中英文文献翻译.doc

1、英文文献The Application of one point Multiple Access Spread Spectrum Communication SystemLiu Jiangang, Nan yang City, Henan Province Electric Power Industry Bureau【ABSTRACT】Spread Spectrum Digital Microwave communication as a communication, because their excellent performance have been widely used. The

2、article in Nan yang City Power Industry Bureau one point Multiple Access Spread Spectrum Communication System as an example. briefed the spread spectrum communications, the basic concept and characteristics of the power system communication applications.KEYWORDS ：one point multiple access; Spread-sp

3、ectrum communication; Attenuation Nan yang City in the outskirts of Central cloth 35 to 11 kv substation farm terminals, their operation management rights belong to the Council East, Rural Power Company west (the eastern suburb of agricultural management companies - four, the western suburbs of Rura

4、l Power Company Management 7), Scheduling of the various stations of the means of communication to the original M-150 radio and telephone posts. 2002 With the transformation of rural network, the remote station equipment into operation and communication channels to put a higher demand .As PUC Dispat

5、ch Communication Building to the east and west of farmers - the difference between a company linked to fiber, Therefore, if 11 substations and the establishment of a transfer Link Building links Point may be the data and voice were sent to two rural power companies dispatch room, Rural Network sched

6、uling for the implementation of automation to create the necessary conditions.Given the status and power grid substation level, nature, taking into account the carrier and optical-fiber communications to conduct multiple forwarding, increasing the instability factor, considering the cost and conditi

7、ons of the urban construction, Finally decided to adopt wireless spread-spectrum technology to establish that 11 farm terminal substation communication system. This paper describes the spread spectrum technology and the current system of the building.1. The basic concept of spread-spectrum communica

8、tion.Spread Spectrum Communications basic characteristics, is used to transmit information to the signal bandwidth (W) is far greater than the practical information required minimum (effective) bandwidth ( F) , as the ratio of processing gain GP .GP = W/FAs we all know, the ordinary AM, FM, or pulse

9、 code modulation communications, GP values in the area more than 10 times, collectively, the narrow-band communication, and spread-spectrum communications GP values as high as hundreds or even thousands of times, can be called broadband communications. Due to the spread-spectrum signal, it is very l

10、ow power transmitters, transmission space mostly drowned in the noise, it is difficult to intercepted by the other receiver, only spreading codes with the same (or random PN code) receiver, Gain can be dealt with, and dispreading resume the original signal. 2. The technology superiority of spread-sp

11、ectrum communication.Strong anti-interference, bit error rate is low. As noted above, the spread spectrum communication system due to the expansion of the transmitter signal spectrum, the receiver dispreading reduction signal produced spreading gain, thereby greatly enhancing its interference tolera

12、nce. Under the spreading gain, or even negative in the signal-to-noise ratio conditions, can also signal from the noise drowned out Extraction, in the current business communications systems, spread spectrum communication is only able to work in a negative signal-to-noise ratio under the conditions

13、of communication. Anti-multi-path interference capability, increase the reliability of the system. Spread-spectrum systems as used in the PN has a good correlation, correlation is very weak. different paths to the transmission signal can easily be separated and may in time and re-alignment phase, fo

14、rmation of several superimposed signal power, thereby improving the systems performance to receive increased reliability of the system. Easy to use the same frequency, improving the wireless spectrum utilization. Wireless spectrum is very valuable, although long-wave microwave have to be exploited,

15、and still can not meet the needs of the community. To this end, countries around the world are designed spectrum management, users can only use the frequency applications, rely on the channel to prevent the division between the channel interference. Due to the use of spread-spectrum communication re

16、lated receive this high-tech, low signal output power ( a W, as a general-100 mW), and will work in the channel noise and thermal noise in the background, easy to duplicate in the same area using the same frequency, can now all share the same narrow-band frequency communications resources.Spread spe

17、ctrum communication is digital communications, particularly for digital voice and data transmission while, spread spectrum communication with their own encryption, only in the same PN code communication between users, is good for hiding and confidential in nature, facilitating communications busines

18、s . Easy to use spread-spectrum CDMA communications, voice compression and many other new technologies, more applicable to computer networks and digitization of voice, image information transmission. Communication is the most digital circuits, equipment, highly integrated, easy installation, easy ma

19、intenance, but also very compact and reliable. The average failure rate no time was very long. We have decided to adopt the spread-spectrum communication technology construction of 11 farm terminal substation communications system, Due to the spread-spectrum communication by the line-of-sight transm

20、ission distance restrictions, has become unstoppable system design premise. If the PUC scheduling Building and 11 substations have stopped, and the problem becomes more complicated, use spread spectrum system on the feasibility greatly reduced. Therefore, we look at the city Aerial topographical map

21、, initially identified has not stopped to consider systems design, and requests the companies used this equipment Spread Spectrum 11 points transmission routing of the measured and the results have been satisfactory.Then spread spectrum wireless equipment market supply of cash, initially, we selecte

22、d a series of Spread Spectrum Comlink third generation products. Because most of the point-to-point mode, Merit functions of the spread-spectrum equipment in a point-to-multipoint application environments encountered many problems: First is the issue of frequency resources. Even a minimum of 64 kbit

23、 / s data rate radio, space also occupied bandwidth 5 MHz, Because 32 of the PN code isolation is only about 15 dBm, the project had to use frequency division multiple access 35 db to get around the theoretical isolation. 11 stations will use 11 frequencies, frequency greater waste of resources. Com

24、link and Spread Spectrum products in the same frequency to achieve a point-to-multipoint communications. Second antenna erection problems, point-to-point equipment for the main radio station, the main station need to set up a number of terminal antennas, the vast majority of domestic engineering com

25、panies used by the U.S. Conifer 24 dBi parabolic semi-cast magnesium grid directional antenna. vertical polarization - 1 m wide, it is difficult to top the layout and avoid flap and the mutual interference, Although the project can be set up to take stratified, or through cooperation and on the road

26、 to one or more Omni directional antenna launch, However, as construction of a road and the signal attenuation, transmission result is not satisfactory. In addition, the RF cable lying, The application of network management software such factors we have also decided to adopt the final 1:00 Comlink M

27、ultiple Access Spread Spectrum products. Its system configuration, as shown in Figure 2:3. Routing AnalysisCombining visual distance access and use the radio and antenna gain, cable attenuation and environmental factors, and testing the design is reasonable, determine the attenuation affluent channe

28、l capacity. Spread spectrum microwave link attenuation depends on the reliability margin.Attenuation margin calculation formula : FG= GSG + GANT - LGL - LPL FGAttenuation margin ； GSGSystem Gain (dB）； GANTAntenna Gain (dBi）； LGLConnectors and cables attenuation (dB)； LpL Channel attenuation (dB）。 Ga

29、in spread spectrum radio system : GSG = +27 - (-97) = 124 (dBm)； Antenna Gain: master-use 2.4 GHz, 12 dBi Omni-Directional Antenna, stop-use 2.4 GHz, 24 dBi parabolic directional antennas; Connector and cable attenuation: cable attenuation of about 3 dB, as a joint dB attenuation, LGL = 3 + 1 = 4 (d

30、B); Channel attenuation to the farthest distance from the building scheduling substation (27 km) as an example: LPL = 92.4 + + 20lg27 20lg2.4 = 128 (dB); Therefore attenuation cushion: FG = 124 + 12 + 24-2 4-128 = 24 (dB). Calculated from the amount of affluent link can be seen, the program has larg

31、er reserves and thus the rational design of the program, According to the measured and the results showed the channel can ensure quality and reliability. 4. Operation of the system.System since May 2003 has been put into operation more than two years, each station to transmit information; there are

32、two phones, 600 or 1200 Porter remote information operations, clear voice station, Channel stability, without error, System not had any serious interruptions and failures, equipment operating normally. Thus, the spread spectrum link to the design and equipment selection has been very good to meet the voice and remote automated information transmission, Network for the safe and stable operation to provide a reliable guarantee.5. Concluding remarks.Spread-spectrum technology in the initial stages of development, it has become a theory and a major