2. Contents
7.1 AMPS
7.2 United State Digital Cellular(USDC)
7.3 Global System for Mobile Communication (GSM)
7.3.1 GSA System Architecture
7.3.2 GSM Radio Subsystem
7.3.3 GSM Channel Type
3. 7.1 AMPS
7.1 AMPS (Advanced mobile phone service)
first large cells and Omni-directional base station antennas used.
AMPS uses a 7-cell reuse pattern and 30 kHz channel used.
7.2 United State Digital Cellular(USDC)
AMPS system was not designed to support the current demand for
capacity in large cities.
Cellular systems which use digital modulation techniques offer large
improvements in capacity and system performance. USDC also offers
as much as six times the capacity of AMPS.
4. 7.3 Global System for Mobile Communication (GSM)
GSM is the world's first cellular system to specify digital modulation
and network level architectures and services.
GSM services follow ISDN guidelines and are classified as either
Tele-services or
data services
Teleservices include standard mobile telephony and mobile-originated
or base-originated traffic.
Data services include computer-to-computer communication and
packet-switched traffic.
5. 7.3.1 GSA System Architecture
Consists of three major interconnected subsystems:
1. Base Station Subsystem (BSS)
2. Network and Switching Subsystem (NSS) and
3. Operation Support Subsystem (OSS)
BSS
radio subsystem
Mobile Station (MS)
provides and manages radio transmission paths between the mobile
stations and the Mobile Switching Center (MSC)
one of the most remarkable features of GSM is the Subscriber
Identity Module (SIM).SIM is a memory device that stores
information:
6. Cont….
Three databases in the NSS are:-
1. Home Location Register (HLR)
2. Visitor Location Register (VLR) and
3. Authentication Center (AUC)
7.3.2 GSM Radio Subsystem
GSM utilizes two bands of 25 MHz which have been set aside for
system use in all member countries.
890-915 MHz band is used for reverse link.
935-960 MHz band is used for forward link.
GSM uses FDD and a combination of TDMA and FHMA scheme.
7.3.3 GSM Channel Type
Two types of GSM logical channels:
1. traffic channels (TCH)
2. control channels (CCH) or Signaling Channel
8. Cont…
A. Traffic Channels (TCH)
carry digitally encoded user speech or user data,and have identical functions
and formats on both forward and reverse link.
B. Control Channels (CCH)
Three main control channels are
I. Broadcast channel (BCH)
II. Common control channel (CCCH)
III. Dedicated control channel(DCCH)
Three types of BCH
a) Broadcast Control Channel (BCCH)
b) Frequency Correction Channel (FCCH)
c) Synchronization Channel (SCH)
three types of CCCH channels
a) paging channel (PCH) - is a forward link channel
b) random access channel (RACH) - is a reverse link channel
c) access grant channel (AGCH) - is a forward link channel
Three types of dedicated control channels
a) Stand-alone Dedicated Control Channels (SDCCH)
b) Slow Associated Control Channel (SACCH)
c) Fast Associated Control Channels (FACCH)
