1、【附录】 英文文献 The Application of one point Multiple Access Spread Spectrum Communication System Liu Jiangang, Nanyang City, HenanProvince Electric Power Industry Bureau 【 ABSTRACT 】 Spread Spectrum Digital Microwave communication as a communication, because their excellent performance have been widely u
2、sed. The article in Nanyang 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；
3、Spread-spectrum communication； Attenuation Nanyang 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
4、 of Rural 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 PU
5、C Dispatch 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 Netwo
6、rk scheduling 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 an
7、d conditions 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
8、 communication. 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/ F As we all know, the ordinary AM
9、, FM, or pulse 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
10、, it is very low 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 despreading resume the original signal. 2. The technology superiorit
11、y of spread-spectrum 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 despreading reduction signal produced spreading gain, thereby greatly enhancing its inte
12、rference tolerance .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
13、the conditions 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-alig
14、nment phase, formation 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
15、be exploited, 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 co
16、mmunication related 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 resour
17、ces. Spread spectrum 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 communi
18、cations business .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 install
19、ation, easy maintenance, 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-o
20、f-sight transmission 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 top
21、ographical map, 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, Initia
22、lly, we selected a series of Spread Spectrum Comlink third generation products. Because most of the point-to-point mode, Merit function of the spread-spectrum equipment in a point-to-multipoint application environments encountered many problems : First is the issue of frequency resources. Even a min
23、imum of 64 kbit / 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 frequency, frequency greater waste of r
24、esources. Comlink 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 en
25、gineering companies 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 flap and the mutual interference, Although the project can be set up to take stratified, or through cooperation and on the
