Chapter 8 2G

Channel Configuration
• The 25MHz bandwidth in each direction is divided into 200kHz frequency channels. So there are 124 channels available in each direction of transmission. • If channel number is n, the serial number of the carrier frequency which is n in both upper and lower bands can be used calculation : uplink: downlink: fh(n)=(935+0.2n) MHz n=1～124 fl(n)=(890+0.2n) MHz n=1～124
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Network structure and Network Interface
GSM Network structure and composition
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Network structure and Network Interface
• GSM cellular system network structure is mainly composed of the mobile station, base station subsystems and network subsystems. The network is interconnected by the MSC and the PSTN (PSTN), Integrated Services Digital Network (ISDN) and public data network (PDN).
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Physical channel
• Frequency Band
GSM operates in the 890-915MHz band uplink (MS to BS) and 935960MHz band downlink (BS to MS). The frequency interval between Receive and transmit is 45MHz .
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Internal interface in network subsystem
• B interface: the communication interface between VLR and MSC; • C interface: the communication interface between HLR and MSC; • D interface: the communication interface between HLR and VLR; • E interface: the communication interface between Adjacent regions of different mobile switching center • F interface: the communication interface between MSC and EIR; • G interface: the communication interface between two VLR.
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Simplified Introduction
• D-AMPS : TDMA-based system , North-American, the digital follow-on to the first-generation AMPS analog cellular system; GSM : TDMA-based system, pan-European , also deployed in the USA and in the word; IS-95 : CDMA-based system, North-American
The main interface
• The main interface of the GSM system is A interface, Abis Interface and the Um interface.
A interface: the communication interface between the network interface subsystem (NSS) and Base Station Subsystem (BSS), the physical link through the use of standard 2.048 Mb / s PCM digital transmission link to achieve; Abis interface: the communication interface between the two functional entities —BSC and BTS of the base station subsystem. the physical link through the use of standard 2.048 Mb/s or 64 kb/s PCM digital transmission link to achieve; Um interface: the communication interface between MS and BTS.
Second-generation digital wireless systems
Prof. Pingan Li
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OUTLINE
• • • • •
Network structure and Network Interface GSM system D-AMPS system IS-95 system System communication capacity
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U m BTS BSC A C MSC E F B EIR G VLR VLR MSC D
MS
Abis HLR
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Network structure and composition
Simplified ,Cellular system
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Network structure and Network Interface
MS: Mobile Station (the North-American standard calls CSS) BS: Base Station MSC: Multiple Switching Center (responsible for handling inter-cellular handoff, as well as mobile location, paging, and other mobile management and control functions ) HLR: Home Location Register, contains reference and profile information for all mobile subscribers registered with this MSC VLR: Visitors’ Location Register, stores visitors’ reference and profile information ISDN: Integrated Services digital network PSTN: Public Switched Digital Network
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Network structure and Network Interface
• MSC is the core of the network, which provides exchange functions and interface functions. It can manage up to a few dozen base stations controllers; • VLR is a service to its mobile users to control the region, stores the information of the registered mobile users who enter in the region under their control ; • HLR stores relevant data of all the existence mobile users in the control of the HLR ; • AUC provides security protection; • EIR storage of mobile devices Code International Mobile Equipment Identification, to ensure that the network used by mobile devices and the only security.
• Channel interval
Adjacent channel interval is 200kHz. Each frequency channel is divided into 8-slot by using TDMA .
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1.Mobile station Mobile station is a public mobile communications network equipment for users;
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Network structure and Network Interface
2.Base station subsystem BS contains the base transceiver station (BTS) and base station controller (BSC). It is connected directly with the mobile station through a wireless interface, in charge of the wireless sending close access and wireless resource management; On the other hand, it is connected with the mobile services switching center (MSC) in network subsystem (NSS). A base station controller can control up to 256 BTS; work subsystem NSS contains Mobile Switching Center (MSC), Operation and Maintenance Center (OMC), Home Location Register (HLR), Visitor Location Register (VLR), Authentication Center (AUC) and Mobile Device Identification Register (EIR) and so on.