General Description - Samsung SGH-600 Service Manual

1. General Description

1-1 GSM System
1-1-1 Calls
GSM ¨ is an acronym for Global System for Mobile communications
operation. The GSM system consists of the sub-systems shown;
The Mobile Station (MS) talks to the Base Station System (BSS) via an RF air interface. The Base Station System
(BSS) consists of Base Transceiver Station (BTS) and a Base Station Controller (BSC). The microwave link
between BTS and BSC is called an Abis interface. Generally one BSC controls 20 to 30 BTSs, and a Mobile
Switching Center (MSC) controlling the traffic among different cells would be reported back from a number of
BSSs. A Visitor Location Register (VLR) will be allocated to one MSC to find the mobiles out of their home cell
by listing them to VLR. The MSC would also be connected to the Home Location Register (HLR), the
Authentication Center (AC) and the Equipment Identity Register (EIR) So the system verify that the users and
equipment are legal subscriber.
1-1-2 Channels
Channels used in the GSM system can be divided into two classes - Logical and Physical channel. Physical
channels can be described in terms of their frequency and time domain characteristics. They are the actual
frequencies and timeslots the MS and BS transmits or receives on. The logical channels are mapped onto these
physical channels logically. Any particular and instant, physical channels may be control or traffic channels,
which determines the function of a physical channel at a particular point in time.
1-1-3 Airinterface of ARFCN (Absolute Radio Frequency Channel Number)
1 2
890.2 MHz
1 2
935.2 MHz
Samsung Electronics
3 ... ...
3 ... ...
P-GSM: TX: Fl(n) = 890 + 0.2*n (1≤n≤124)
RX: Fu(n) = Fl(n) + 45
< Fig. 1 ARFCN Diagram >
© , using TDMA for wide-area cellular
... ... ... 123
... ... ... 123
124
914.8 MHz
124
959.8 MHz
1-1