1、 山 东 科 技 大 学 外 文 翻 译 学 院 名 称 电气信息系 专 业 班 级 电气工程 及其自动化 10-4 班 学 生 姓 名 梅玉金 学 号 201003201414 指 导 教 师 姚 福 强 翟 绪 梅 Theoretical Study of the General Packet Radio Service Abstract: As communications technology continues to mature and users quality have become increasingly demanding, new data applications a
2、re emerging and are reaching the general public. Through the use of GPRS (General Packet Radio Service) technology, 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 advantag
3、e. This paper aims to provide a comprehensive yet simple overview of the GPRS system from the users and from the architectural perspectives. Keywords: GPRS networks； Voice/data integration； Multiple-channels； Packet radio； Telecommunications 1 Introduction In the late 1800s, Marconi did the pioneer
4、work establishing the first successful 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, wir
5、eless communication systems were dominated 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 syst
6、ems consisted of a base station with 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 PSTN (Public Switched Telephone N
7、etworks). Today, the cellular systems consist of a cluster of ba -se station with low power radio transmitters. Each base station serves a small cell within a large geographic area. The total number of users served is increased because of channel reuse and al -so larger frequency bandwidth. Global s
8、ystem for mobile communications 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 impor
9、tant service in GSM is voice telephony. 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 carr
10、iers, however, start deploying the 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
11、already but they have been constrained by the use of circuit-switched data channels over the air interface allowing a maximum bit rate of 14.4 kb/s. For this reason, the GSM standard has continued its natural evolution to accommodate the requirement for higher bitrates. The HSCSD (High-speed Circuit
12、-switched Data) are one solution 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 subscr
13、ibers who want to be charged based 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
14、single user for the duration of the 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 sub
15、scribers with the much needed high 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 kb/s. Volume-based charging is possible because channels are allocated to use
16、rs only when packets are to be 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 a
17、rea is divided into cells, with 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 inter
18、ference from another cell and thus 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 use
19、rs to serve, usually more channels 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 acce
20、ptable level. Mobility is one of the key features in wireless communication systems. There is a need to track the users moving into different cells and changing radio channels. A mobile switched to another channel in a different cell is called handoff. A signaling and call processing procedure is needed to support user mobility and handoff such that a mobile phone can be completed successfully. Paging is
