7 - Indira Gandhi Centre for Atomic Research

• 1 or 2 digit Final Assy Code (FAC). This identifies the place of manufacture of
assembly of the MS unit
• 11 digit MS unit serial number
• 1 spare digit reserved for future use.
The IMSI is also 15 digits and consists of:
• 3 digit Mobile Country Code (MCC). This identifies the country where the
GSM system operates.
• 2 digit Mobile Network Code (MNC). This uniquely each cellular provider.
• The Mobile Subscriber Identification Code (MSIC). This uniquely identifies
each customer of the provider.
5.1.2 Base Station Subsystem (BSS)
The BSS contains the necessary hardware and software to enable and control the radio
links with the mobile stations. It contains two parts, the base station (BS) and the base
station controller (BSC). These communicate across the standardized Abis interface,
allowing operation between components made by different suppliers. The BS contains the
radio transceivers that define a cell and handles the radio link protocols with the MS. BSs
are responsible for frequency administrations and handovers.
5.1.3 Network Subsystem
The central component of the network subsystem is the Mobile Switching Center (MSC).
The MSC performs switching of user calls and provides functionality for registration,
authentication, location updating, handovers and call routing to a roaming subscriber. The
MSC interfacing the GSM network to fixed networks (PSTN) is known as gateway MSC.
5.2 Speech Coding & Radio Transmission Characteristics
The speech coding algorithm used in GSM is called Regular Pulse Excited-Linear
Predictive Coder with a long term predictive loop. As with any other wireless networks,
GSM encodes data into waves in order to send it over the wireless medium. The actual
modulation scheme used is Gaussian Minimum Shift Keying (GMSK), which achieves
270.8 kbps over each of the 200-kHz wide GSM channels. The available bandwidth in
GSM is split into 124 carriers, each 200-kHz wide. GSM uses a combination of Time and
Frequency Division Multiple Access (TDMA/FDMA) for user separation. One or more
carrier frequencies are assigned to each BS of the GSM network and each of those carriers
is divided in the time domain. Each time period is a slot and lasts 0.577ms.
6 CDMA Technology (IS-95)
cdmaOne, a 2G system developed by Qualcomm also
known as IS-95, has been standardized in 1993 and the first
commercial systems were deployed in 1995. cdmaOne
utilizes Code Division Multiple Access (CDMA). In
cdmaOne, multiple mobiles in a cell, whose signals are
distinguished by spreading them with different codes,
simultaneously use a frequency channel. Thus, neighboring
cells can use the same frequencies, unlike all other
standards. cdmaOne operate in the same band with AMPS
and it is designed to support dual-mode terminals that can
operate either under an cdmaOne network or an AMPS
Packet Data
Applications
TCP/IP
Voice
Applications
Best effort delivery RLP
Multiplexing
Physical Layer
Circuit Data
Applications
OSI Layers 3-7
OSI Layer 2
OSI Layer 1
109
Figure 7: Protocol Architecture of CDMA