Evolution of Cellular Systems 9
implemented GSM and this standard gained acceptance outside of Europe. The standard
was eventually renamed as the Global System for Mobile Communications.
The TDMA scheme is used in GSM air interface with a capability of multiplexing eight
users in a single 200 KHz channel bandwidth, where the users were separated by different time slots. Gaussian minimum shift keying (GMSK) was introduced as a modulation
technique of GSM. Because of the constant envelope property and significant power and
spectral efficiency, the GMSK was convenient [1].
A circuit switched data of 9.6 kbps rate was also supported by GSM, along with the
voice and SMS service. GSM packet radio systems (GPRS) were introduced by ETSI
in the mid‐1990s. It was an evolutionary step of GSM systems towards higher data
rates. The GPRS and GSM systems both share the same frequency bands, signaling
link and time slots. There were four different channel coding schemes to support the
data, at the rates of 8 kbps to 20 kbps per slot. Theoretically, the GPRS was able to
provide 160 kbps rate, where the 20–40 kbps rate was found in practice.
1.4.2 GSM Network Architecture
The GSM Network architecture is comprised of two major sub‐components. This
architecture forms the basis of the next generation (3G) systems and LTE. In Figure 1.2,
the base station subsystem is comprised of the base‐station transceiver (BTS) unit, with
which the mobile stations (MS) and the base station controller (BSC) are connected
over the air interface. BSC manages the traffic from several BTSs to the switching core.
It also manages Mobility across BTSs. Another sub‐component is Network Switching
Base Station Subsystem (BSS)
Radio Access Network (RAN)
HLR
MSC
BSC
(RNC)
PCU
EIR
AuC
PSTN
SS7
Network
GPRS Core Network
GPRS
IP backbone
Internet/
PDN
SGSN
GGSN
MS
MS: Mobile Station
BTS: Base Station Transceiver System
BSC: Base Station Controller
PCU: Packet Controller Unit
MSC: Mobile Switching Center
VLR: Visitor Location Register
PSTN: Public Switched Telephone Network
HLR: Home Location Register
AuC: Authentication Center
SGSN: Serving GPRS Support Node
GGSN: Gateway GPRS Support Node
PDN: Packer Data Network
EIR: Equipment Identity Register
BTS
BTS
VLR
Network Switching Subsystem (NSS)
Figure 1.2 GSM network architecture.
implemented GSM and this standard gained acceptance outside of Europe. The standard
was eventually renamed as the Global System for Mobile Communications.
The TDMA scheme is used in GSM air interface with a capability of multiplexing eight
users in a single 200 KHz channel bandwidth, where the users were separated by different time slots. Gaussian minimum shift keying (GMSK) was introduced as a modulation
technique of GSM. Because of the constant envelope property and significant power and
spectral efficiency, the GMSK was convenient [1].
A circuit switched data of 9.6 kbps rate was also supported by GSM, along with the
voice and SMS service. GSM packet radio systems (GPRS) were introduced by ETSI
in the mid‐1990s. It was an evolutionary step of GSM systems towards higher data
rates. The GPRS and GSM systems both share the same frequency bands, signaling
link and time slots. There were four different channel coding schemes to support the
data, at the rates of 8 kbps to 20 kbps per slot. Theoretically, the GPRS was able to
provide 160 kbps rate, where the 20–40 kbps rate was found in practice.
1.4.2 GSM Network Architecture
The GSM Network architecture is comprised of two major sub‐components. This
architecture forms the basis of the next generation (3G) systems and LTE. In Figure 1.2,
the base station subsystem is comprised of the base‐station transceiver (BTS) unit, with
which the mobile stations (MS) and the base station controller (BSC) are connected
over the air interface. BSC manages the traffic from several BTSs to the switching core.
It also manages Mobility across BTSs. Another sub‐component is Network Switching
Base Station Subsystem (BSS)
Radio Access Network (RAN)
HLR
MSC
BSC
(RNC)
PCU
EIR
AuC
PSTN
SS7
Network
GPRS Core Network
GPRS
IP backbone
Internet/
PDN
SGSN
GGSN
MS
MS: Mobile Station
BTS: Base Station Transceiver System
BSC: Base Station Controller
PCU: Packet Controller Unit
MSC: Mobile Switching Center
VLR: Visitor Location Register
PSTN: Public Switched Telephone Network
HLR: Home Location Register
AuC: Authentication Center
SGSN: Serving GPRS Support Node
GGSN: Gateway GPRS Support Node
PDN: Packer Data Network
EIR: Equipment Identity Register
BTS
BTS
VLR
Network Switching Subsystem (NSS)
Figure 1.2 GSM network architecture.