tailieunhanh - GSM Networks : Protocols, Terminology, and Implementation - Chapter 3

Trạm cơ sở hệ thống con Thông qua giao diện-Air, BSS cung cấp một kết nối giữa MSS của một khu vực giới hạn và chuyển đổi mạng lưới các hệ thống con (NSS). BSS bao gồm các yếu tố sau: • Một hoặc nhiều BTSs (trạm cơ sở Tranceiver); • Một BSC (trạm điều khiển); • Một Trâu (chuyển mã thích ứng tốc độ và đơn vị). Các nhiệm vụ và cơ cấu của những yếu tố hoặc mô-đun được mô tả trong chương này | 3 The Base Station Subsystem Via the Air-interface the BSS provides a connection between the MSs of a limited area and the network switching subsystem NSS . The BSS consists of the following elements One or more BTSs base tranceiver station One BSC base station controller One TRAU transcoding rate and adaptation unit . The tasks and the structure of those elements or modules are described in this chapter. Base Transceiver Station The BTS provides the physical connection of an MS to the network in form of the Air-interface. On the other side toward the NSS the BTS is connected to the BSC via the Abis-interface. The manufacturers of BTS equipment have been able to reduce its size substantially. The typical size in 1991 was that of an armoire today the size is comparable to that of a mailbox. The basic structure of the BTS however has not changed. The block diagram and the signal flow of a BTS with one TRX are shown in Figure . The GSM Recommendations allow for one BTS to host up to 16 TRXs. In the field the majority of the BTSs host between one and four TRXs. 19 20 GSM Networks Protocols Terminology and Implementation Air-interface Abis-interface Figure Block diagram of a BTS with one TRX. Architecture and Functionality of a Base Transceiver Station Transmitter Receiver Module The TRX module is from the perspective of signal processing the most important part of a BTS. The TRX consists of a low-frequency part for digital signal processing and a high-frequency part for GMSK modulation and demodulation. Both parts are connected via a separate or an integrated frequency hopping unit. All other parts of the BTS are more or less associated with the TRXs and perform auxiliary or administrative tasks. A TRX with integrated frequency hopping serves the tasks listed in Table . Operations and Maintenance Module The operations and maintenance O M module consists of at least one central unit which administers all other parts of the BTS. For .