外文翻译---理论研究通用分组无线业务

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1、 外文翻译材料 电子工程 系 自动化 学 生 姓 名： 学 号： 01207111 设 计 地 点： 东南大学成贤学院 指 导 教 师： Theoretical Study of the General Packet Radio Service Abstract: As communications technology continues to mature a -nd users quality have become increasingly demanding, new da -ta applications are emerging and are reaching the gene

2、ral public. Through the use of GPRS (General Packet Radio Service) techn -ology, the existing GSM networks can be easily achieved with simple high-speed data packet access, enabling mobile operators to respond rapidly to market demands and gain competitive adva -ntage. This paper aims to provide a c

3、omprehensive yet simple overview of the GPRS system from the users and from the arch -itectural perspectives. Keywords:GPRS networks；Voice/data integration； Multiple-channels； Packet radio； Telecommunications 1 Introduction In the late 1800s, Marconi did the pioneer work establishing the first succe

4、ssful radio link between a land-based station and a tugboat. Since then,wireless communication systems have been developing and evolving with a furious pace. The number of mobile subscribers has been growing tremendously in the past decades. In the early stages,wireless communication systems were do

5、minated by military usage and supported according to military needs and requirements. During the last half a century, with increasing civil applications of mobile services,commercial wireless communication systems have been taking the lead. The early wireless systems consisted of a base station with

6、 a high-power transmitter and served a large geographic area. Each base station could serve only a small number of users and was costly as well. The systems were isolated from each other and only a few of the communicated with the PSTNs (Public Switched Telephone Networks). Today, the cellular syste

7、ms consist of a cluster of ba -se station with lowpower radio transmitters. Each base station s -erves a small cell within a large geographic area. The total num -ber of users served is increased because of channel reuse and al -so larger frequency bandwidth. Global system for mobile communications

8、is the European standard for cellular communications developed by the ETSI (European Telecommunications Standards Institute).Throughout Europe and the rest of the world, GSM has been widely adopted.It has already been implemented in over 100 countries. The most important service in GSM isvoice telep

9、hony. Voice is digitally encoded and carried by the GSM network as a digital stream in a circuit-switched mode. Data services have been gaining popularity in cellular networks since they were first introduced through the circuit-switched connection. As cellular carriers, however, start deploying the

10、 packet data service such as GPRS (General Packet Radio Service), carriers can provide data services in a more bandwidth-efficient way over the cellular network, thereby increasing the radio resource utilization. 2 GPRS-related technologies GSM offers data services already but they have been constra

11、ined by the use of circuit-switched data channels over the air interface allowing a maximum bit rate of 14.4 kbit/s. For this reason, the GSM standard has continued its natural evolution to accommodate the requirement for higher bit rates.The HSCSD (High-speed Circuit-switched Data) are one solution

12、 that address this requirement by allocating more time slots per subscriber and thus better rates. It remains however insufficient for bursty data applications such as Web browsing.Moreover, HSCSD rely on circuit-switching techniques making it unattractive for subscribers who want to be charged base

13、d on the volume of the data traffic they actually use rather than on the duration of the connection. In turn, service providers need effective means to share the scarce radio resources between more subscribers. In a circuit-switched mode, a channel is allocated to a single user for the duration of t

14、he connection. This exclusive access to radio resources is not necessary for data applications with the use of packet switched techniques. GPRS stands out as one major development in the GSM standard that benefits from packet switched techniques to provide mobile subscribers with the much needed hig

15、h bit rates for bursty data transmissions. It is possible theoretically for GPRS subscribers to use several time slots (packet data channels) simultaneously reaching a bit rate of about 170 kbit/s. Volume-based charging is possible because channels are allocated to users only when packets are to be

16、sent or received. Bursty data applications make it possible to balance more efficiently the network resources between users because the provider can use transmission gaps for other subscriber activities. 2.1 Basic Principle In a cellular network, an entire geographic area is divided into cells, with

17、 each cell being served by a base station. Because of the low transmission power at the base station, the same channels can be reused again in another cell without causing too much interference. The configuration and planning of the cell is chosen to minimize the interference from another cell and t

18、hus maximum capacity can be achieved. The cell is usually depicted as a hexagon, but in reality the actual shape varies according to the geographic environment and radio propagation. Channel allocation is chosen based on the density of the users. If a cell has many users to serve, usually more chann

19、els are allocated. The channels are then reused in adjacent cells or cluster of cells. The spatial separation of the cells with the same radio channels, in conjunction with the low transmission power and antenna orientation, keeps the co-channel interference at an acceptable level. Mobility is one of the key features in wireless communication systems. There is a need to