8/11/2019 Concept of GSM
1/11
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 1
Zrcher
Hochschule
Winterthur
Kommunikationssysteme (KSy) - Block 12
Global System for
Mobile Communications
Global System for
Mobile Communications
Dr. Andreas Steffen
Hans Weibel
2000 Zrcher Hochschule Winterthur
R
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 2
Zrcher
Hochschule
WinterthurGSM Mobile Communications
Overview
Part I GSM Basics & GSM Circuit-Switched Voice/Data
Properties of Wireless Channels
GSM Network Elements and Topology
GSM Radio Interface
Physical and Logical Channels for Circuit-Switched Voice/Data
Full Rate and Half Rate Traffic Channels
Channel Coding of Voice Connections
Evolution of GSM (HSCSD / GPRS / EDGE)
Part II GSM Packet-Switched Data & UMTS
Physical and Logical Channels for Packet-Switched Data (GPRS)
GPRS Random Access Protocol (Uplink State Flag USF)
3rd Generation Partnership Project (3GPP / IMT-2000)
Universal Mobile Telecommunications System (UMTS)
Frequency Bands / Deployment Schedule
Technology
Services
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 3
Zrcher
Hochschule
WinterthurGSM Mobile Communications
Multipath Propagation / Fading
Wavelength @ 900 MHz: 30 cm
direct path
(line-of-sight)
reflections
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 4
Zrcher
Hochschule
WinterthurGSM Mobile Communications
Special Properties of Wireless Channels
Multipath propagation due to reflections
Desireable, if line-of-sight between transmitter and receiver is
not available (urban areas / buildings)
Annoying, since it causes fading (local signal cancellation).
Frequency hopping improves the situation for stationary MS
Large delay spreads cause inter-symbol interference (ISI)
Channel estimation by periodic transmissions of a training
sequence is the basis of optimum channel equalization
Bit Errors are not randomly distributed
Errors often occur in bursts of several consecutive bits
The raw uncorrected bit error ratio (BER) is around 10-2... 10-3
Channel coding based on forward error correction (FEC)
Achieves a satisfactory BER after correction in the range
of 10-5... 10-6
8/11/2019 Concept of GSM
2/11
8/11/2019 Concept of GSM
3/11
8/11/2019 Concept of GSM
4/11
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 13
Zrcher
Hochschule
Winterthur
B = 200 kHz
B
B
B
B
Guard Band
f
fN
fk
f2
f1
0
Radio
Frequency
Channels
Guard Band fL
fU
Frequency
Band
...
GSM Mobile Communications
Combined FDMA / CDMA Scheme
t
...0 1 2 ... 7 0 1
...0 1 2 ... 7 0 1
...0 1 2 ... 7 0 1
...0 1 2 ... 7 0 1
Time Slots
Frame
T
T 577 s
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 14
Zrcher
Hochschule
WinterthurGSM Mobile Communications
The GSM 900 MHz Frequency Band
860 870 880 890 900 910 920 930 940 950 960 970
25 MHz25 MHz
10 10
4 4
P-GSM
E-GSM
R-GSM
*)
*) several other Systems:- Cordless Telephone CT1, CT1+, CT2
- Telemetry / Telecommand
- Terrestrial Trunked Radio (TETRA)
- Digital Satellite System Receiver (DSSR)
Uplink Downlink
Duplex Distance 45 MHz
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 15
Zrcher
Hochschule
WinterthurGSM Mobile Communications
The GSM 1800, DECT and UMTS Bands
1700 1750 1800 1850 1900 1950 200 2050 2100 2150 2200 2250
75 MHz
UMTS
GSM 1800
DECT
1: Time Division Duplex (TDD)
2: Frequency Division Duplex (FDD)
3: Mobile Satellite System (MSS)
Uplink Downlink
Duplex Distance
95 MHz
75 MHz
1 2 3 1 2 3
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 16
Zrcher
Hochschule
Winterthur
f2
f1...0 1 2 ... 7 0 1
...0 1 2 ... 7 0 1
GSM Radio Interface UmBursts
156.25 Bits in 576.923 s(3.6923 s/Bit)
useful part
Power p(t)
t
8.25 Bits Guard Period
26 Training Bits
2 x 58 Encrypted Bits
3 Tail Bits 3 Tail Bits
8/11/2019 Concept of GSM
5/11
8/11/2019 Concept of GSM
6/11
8/11/2019 Concept of GSM
7/11
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 25
Zrcher
Hochschule
WinterthurGSM Radio Interface UmMapping of Traffic Channels (TCH)
T T A IT T T T T T TT T T
TCH / F : one full rate traffic channel
20 ms 20 ms 20 ms 20 ms 20 ms 20 ms
T Traffic Channel (TCH)
A Slow Associated Control Channel (SACCH)
I Idle Frame
T T T T TT T T T T T T
T T A at T t T t T tt T t T T t T tt T t T t T t
t
a
TCH / H : two half rate traffic channels
TCH Multiframe = 26 TDMA frames in 120 ms
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 26
Zrcher
Hochschule
WinterthurGSM Radio Interface UmEnhanced Full Rate Voice Channel Coding
every
20 ms
78 182
78 182
3 bit CRC
4 tail bits
78 189 189
160 Samples
260 bits
267 bits
456 bits
4 blocks
@ 114 Bits
RPE-LPC
Codec
Block
Coding
Convolutional
Coding
Inter-
leaving
sensitive (class I)
insensitive (class II)
1 2 3 8
Encryption
456 bits spread
over 8 bursts
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 27
Zrcher
Hochschule
WinterthurGSM Radio Interface UmTraffic Channels (TCH)
Full Rate Traffic Channel (TCH / F) Speech Codec
Speech @ 13 kbps (TCH / FS) Full Rate Speech @ 12.2 kbps (TCH / EFS) Enhanced Full Rate
Data @ 14.4 kbps (TCH / F14.4)
Data @ 9.6 kbps (TCH / F9.6)
Data @ 4.8 kbps (TCH / F4.8)
Data @ 2.4 kbps (TCH / F2.4)
Half Rate Traffic Channel (TCH / H) Speech Codec
Speech @ 6.5 kbps (TCH / HS) Half Rate
Data @ 4.8 kbps (TCH / H4.8) Data @ 2.4 kbps (TCH / H2.4)
Traffic Channels are used for bidirectional transmission of
circuit switched voice or data.
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 28
Zrcher
Hochschule
WinterthurGSM Radio Interface UmAdaptive Multi Rate Speech Codec (AMR)
Adaptive Multi Rate Speech Channel (TCH / AFS)
Speech @ 12.2 kbps 244 bits (TCH / AFS 12.2)
Speech @ 10.2 kbps 204 bits (TCH / AFS 10.2)
Speech @ 7.95 kbps 159 bits (TCH / AFS 7.95)
Speech @ 7.40 kbps 148 bits (TCH / AFS 7.4)
Speech @ 6.70 kbps 134 bits (TCH / AFS 6.7)
Speech @ 5.90 kbps 118 bits (TCH / AFS 5.9)
Speech @ 5.15 kbps 103 bits (TCH / AFS 5.15)
Speech @ 4.75 kbps 95 bits (TCH / AFS 4.75)
Adaptive tradeoff between speech quality (compression ratio)
and strength of error protection/correction depending on the
current state of the radio channel. AMR offers a family of eight
codecs with speech rates in the range 4.75 .. 12.2 kbps.
8/11/2019 Concept of GSM
8/11
8/11/2019 Concept of GSM
9/11
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 33
Zrcher
Hochschule
Winterthur
1993 1996 1998 1999 2000 2002
Evolu
tiono
fmob
ileda
taservice
s
Fax/
Data /SMS 9.6 kbit/s
Fax/
Data /SMS 9.6 kbit/s
GSM Evolution
Data Services
Datacom-
pression(2.5
9.6 kbit/s
Datacom-
pression(2.5
9.6 kbit/s
Mobileinternetaccess
Mobileinternetaccess
HSCSD
28.8 kbit/s(+ data
compression)
GPRS pilot
system
HSCSD
28.8 kbit/s(+ data
compression)
GPRS pilotsystem
GPRS
(8 - 92 kbit/sper
subscriber+
datacompression)
GPRS
(8 - 92 kbit/sper
subscriber+
datacompression)
UMTS
(8 - 2000 kbit/sper
subscriber+
datacompression)
UMTS
(8 - 2000 kbit/sper
subscriber+
datacompression)
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 34
Zrcher
Hochschule
WinterthurGeneral Packet Radio Service (GPRS)
System Architecture and Interfaces
MS
GGSNGGSNBSCBSCBTSBTS
Um
SGSNSGSN
MS-SIM
HLRVLR
EIR
Internet
GiGnGb
SGSN Serving GPRS Support Node
GGSN Gateway GPRS Support Node
Gf Gs Gr
D
Gc
Traffic
Signalling
MSC
GGSNGGSN
GGSNGGSNGp
Other
GPRS
Network
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 35
Zrcher
Hochschule
WinterthurGeneral Packet Radio Service (GPRS)
Protocol Stack
IPv4 or IPv6
Um GbMSGn GiBSS SGSN GGSN
PHY
Data Link
Layer
IP
TCP/UDP
GTP
PPP
IP
PHY
Data Link
Layer
IP
TCP/UDP
PHY
Network
Service
BSSGP
LLC
GTPSNDCP
PHY
Network
Service
BSSGP
PLL
RFL
MAC
RLC
PLL
RFL
MAC
RLC
LLC
SNDCP
PPP
IP
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 36
Zrcher
Hochschule
WinterthurGeneral Packet Radio Service (GPRS)
Protocol Stack
GPRS Tunneling Protocol (GTP)
zur Vernetzung von GSNs (auch zwischen verschiedenen
PLMNs) auf einem herkmmlichen IP-Netz
Subnetwork Dependent Convergence Protocol (SNDCP)
Multiplex of several layer 3 connections onto a LLC link
Compression of header information and payload data
Logical Link Control (LLC)
Highly reliable HDLC-type connection between MS and BSS
Radio Link Control (RLC)
Wireless transmission of data blocks, repetition of faulty blocks
Medium Access Control (MAC)
Slotted Aloha random access to the radio channel Physical Link Layer (PLL) und Physical RF Layer (RFL)
Channel coding (FEC), Interleaving, Modulation
8/11/2019 Concept of GSM
10/11
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 37
Zrcher
Hochschule
WinterthurGeneral Packet Radio Service (GPRS)
Logical Channels
Packet
Control
Channels
Packet Data
Traffic Channels
(PDTCH)
Packet
Dedicated
Control
Channels
Packet Timing Advance Control Channel (PTCCH)Packet Associated Control Channel (PACCH)
Packet
Common
Control
Channels
Packet Paging Channel (PPCH)
Packet Random Access Channel (PRACH)
Packet Access Grant Channel (PAGCH)
Packet Notification Channel (PNCH)
Packet Broadcast Control Channels (PBCCH)
Downlink (DL)
Uplink (UL)
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 38
Zrcher
Hochschule
WinterthurGeneral Packet Radio Service (GPRS)
Mapping of Packet Data Channels (PDCH)
B0
60 ms 60 ms 60 ms 60 ms
Radio Block
T Packet Timing Advance Control Channel (PTCCH)
I Idle Frame
T
PDCH Multiframe = 52 TDMA frames in 240 ms
B1 B2 B3 IB4 B5 B6 TB7 B8 B9 IB10 B11
Bx
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 39
Zrcher
Hochschule
WinterthurGeneral Packet Radio Service (GPRS)
Radio BlockCoding Schemes
GPRS Coding Schemes
CS-1 9.05 kbps
CS-2 13.4 kbps
CS-3 15.6 kbps
CS-4 21.4 kbps
EGPRS Coding Schemes (EDGE)
MCS-1 8.8 kbps
MCS-2 11.2 kbps
MCS-3 14.8 kbps
MCS-4 17.6 kbps
The multislot capability of GPRS allows the bundling of 2-3
slots fr simple MS and up to 8 slots for special GPRS MS.
MCS-5 22.4 kbps
MCS-6 29.6 kbps
MCS-7 44.8 kbps
MCS-8 54.4 kbps
MCS-9 59.2 kbps
GMSK 8-PSK
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 40
Zrcher
Hochschule
WinterthurGeneral Packet Radio Service (GPRS)
Quality of Service (QoS)
Reliability Classes
Class
1
2
3
Probability
of lost packet
10-9
10-4
10-2
8/11/2019 Concept of GSM
11/11
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 41
Zrcher
Hochschule
WinterthurGeneral Packet Radio Service (GPRS)
Quality of Service (QoS)
Delay Classes
Class
1
2
3
128 Byte Packet
Mean 95%
< 0.5 s
4
10-9< 1.5 s
1024 Byte Packet
Mean 95%
< 2 s 10-9< 7 s
< 5 s 10-9< 25 s < 15 s 10-9< 75 s
< 50 s 10-9< 250 s < 75 s 10-9< 375 s
best
effort
best
effort
best
effort
best
effort
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 42
Zrcher
Hochschule
Winterthur
GPRS Attach
GPRS Detach
General Packet Radio Service (GPRS)
State Diagram of a GPRS Mobile Station
IDLEIDLE
READY timer expiry
or force to STANDBY
PDU transmission
READYREADY STANDBYSTANDBY
PagingRouting Area (RA)
Update Request
A. Steffen / H. Weibel, 30.6.2000, KSy_GSM.ppt 43
Zrcher
Hochschule
WinterthurGeneral Packet Radio Service (GPRS)
Mobile Originated Packet Transfer
MS Network
Packet Channel RequestPRACH
Packet Uplink AssignmentPAGCH (assignment of TFI)
Packet Resource RequestPACCH (optional)
Packet Uplink AssignmentPACCH (optional)
USF with correct TFIPDTCH (downlink radio block)
Send Data Block
PDTCH (uplink radio block)
USF Uplink State Flag (3 bits)
TFI Temporary Flow Identifier