2. Contents
2
Type of wireless services.
Basics of wireless communication.
Cellular Concepts.
Generations of wireless communication.
Introduction to GSM.
GSM Radio Interface.
Introduction to GPRS.
GPRS Channel Structure
3. Contents cont..
3
Introduction to UMTS
UTRAN Channel structure.
Comparison between 2G,2G+ and 3G
4. Type of wireless services
4
Outdoor Mobile Communication.
– E.g. cellular telephony, WLL etc.
Outdoor Fixed Communication
– E.g. Television broadcast .
Indoor ( Wireless LAN)
– E.g. IEEE 802.11
Satellite Mobile
– E.g. Thuraya, Inmarset etc.
6. Some Basic Terminology
6
Bandwidth
A signal is normally compose of a
range of frequencies. This range of
frequency occupied by the signal is
termed as its BandWidth.
Channel
In communication, the term channel
refers to the communication path
between the two devices. It can refer
to a physical medium or to a set of
properties which distinguishes one
channel from other.
Protocol
A set of rules that govern the
operation of functional units to
achieve communication
7. Access Technologies
7
TDMA CDMA
Time Division Multiple Access Code Division Multiple Access
FDMA
Frequency Division Multiple
Access
F F F
r r r
e e e
q q q
u u u
e e e
n n n
c c c
y y y
Time Time Time
TDMA FDMA CDMA
8. Cellular Concepts
8
Why Cells?
What shape and why?
How to allocate
frequencies?
What is cell capacity?
How it is calculated?
9. Cellular Concepts Contd..
9
Why Cells ?
Each Call Require Pair of RF Channel.
Need to server big community networks.
Radio spectrum available is limited.
Reuse of frequencies required.
What shape and why?
Cells in cellular system is drawn as hexagons.
Actual cell takes different shapes.
Bigger cell for low subscriber density.
Smaller cell for high subscriber density.
On highways cells are optimized to cover length.
10. Cellular Concepts Contd..
10
How to allocate
frequencies?
Split number of channels into
groups
Assigns Frequency in each
group to a cell.
Group cells into cluster
containing all frequencies.
g2 Each cluster size N satisfy
g7 g3 g2
g1 g7 g3 N = I2 + ij + j2
g6 g4 g1 Repeat cluster across area to
g5 g6 g4 be covered.
g2 g5
g7 g3
http://www.dotindia.com/wpcc/
g1
NFAP/contents.htm
g6 g4
g5
11. Cellular Concepts Contd..
11
What is cell capacity?
The cell capacity: Equal to the number of available voice channels per
cell.
The cell Erlang capacity: Equal to the traffic carrying capacity of a cell
(in Erlangs) for a specified call blocking probability.
How it is calculated?
The Erlang capacity can be calculated using the famous Erlang-B
formula.
B( p , m) = pm / ( m! mk=0 ( pk / k! ) )
B( p , m) -> Call blocking probability.
m -> Total number of channels
p = µ -> is the call arrival rate and is the mean call duration.
13. Generations of wireless commn contd.
13
1st Generation
First Generation, analog cellular system were based on FDMA technology, to
provide basic mobile telephony. It used narrow band, 30KHz channels, each
carrying one telephone ckt. The number of calls in a sector were limited to the
amount of carriers that can be assigned to the given spectrum.
2nd Generation
Using digital techniques, Second Generation digital wireless systems offer
increased voice capacity, increased security, low bit rate data and regional
roaming.
2.5 Generation
Here air interface was like 2G only but the upper layer protocols were optimized
for packet switched service so that higher data rate can be achieved.
14. Generations of wireless commn contd.
14
Third Generation
Today’s 2G networks are primarily voice centric. By contrast, 3G systems will be
primarily data and applications centric, combining high-speed mobile access with
packet-based Internet Protocol (IP). Data rates as high as 2 Megabits per second
will be possible in 3G (indoors)2, enabling high-speed data and mobile
multimedia services that include voice, video, low and high-bit-rate data, internet
access, location-based services, and access to information and services,
anytime, anywhere.
15. Introduction to GSM
15
Architecture of GSM system.
BTS - Base Transreceiver Station
GMSC - Gateway MSC
HLR - Home Location Register
SMS
Gateway/IWF MS - Mobile Station
C MSC - Mobile Switching Center
E
SME SM-SC
OMC - Operation and Maintenance
HLR/GR Center
MSC/VLR PSTN -Public Switch Telephone N.
VLR - Visitor Location Register
R
Um BSS
EIR
16. Introduction to GSM Contd..
16
Mobile Station consist of
Mobile Equipment
Identified with International Mobile Equipment Identifier-IMEI
Subscriber Identity Module -SIM
Identified with International Mobile Subscriber Identifier –IMSI
Authentication and Ciphering Key generation algorithm.
Subscriber information
Access control class
Additional GSM services
Forbidden PLMN
17. Introduction to GSM Contd..
17
Base Station Subsystem consist of
BTS
The Base Transceiver Station houses the radio tranceivers that define a cell
and handles the radio-link protocols with the Mobile Station. The base station
is under direction of a base station controller.
BSC
BSC does the Radio Resource Management.
BSC is responsible for Speech coding and rate adaptation.
BSC handles radio-channel setup, frequency hopping, and handovers
BSC can manage tens of BTSs.
18. Introduction to GSM Contd..
18
Network Sub System consist of
MSC Mobile Switching Center:
the main function is to setting-up of calls
MSC controls a few BSCs
HLR:
stores subscribers’ info e.g. IMSI and current location etc.
AuC:
does the mgmt. of security data for the authentication of subscriber
VLR: (Visitor’s Location Register)
is in charge of temporarily storing subscription
GMSC:
the MT call is first routed to a Gateway MSC. The GMSC are in charge of
fetching the location information and of routing the call towards the MSC.
19. GSM Security
19
RAND + Subscriber Key (Ki) + A3 = SRES
RAND + Subscriber Key (Ki) + A8 = Ciphering Key
(Kc)
Kc + Frame Number + A5 = 114 bits to be XOR
with 114 of the burst.
A3 and A8 are implemented in SIM and HLR/AuC
20. GSM Identities
20
MSISDN RAI
Mobile Subscriber International Routing Area Identity
ISDN Number (20 digits Max)
IMSI PLMN
International Mobile Subscriber Public Land Mobile Network
Identity (15 digits)
MCC
IMEI
Mobile Country Code
International Mobile Equipment
Identity (15 digits) MNC
TMSI/PTMSI Mobile Network Code
Temporary Mobile Subscriber ARFCN
Identity (4 octets)
Packet Temporary Mobile Absolute Radio Frequency
Subscriber Identity Number
LAI
Location Area Identity
21. GSM Bands
21
P-GSM - Primary GSM GSM1800/DCS1800
Frequency 890-915MHz(Uplink) Frequency 1710-1785MHz(Uplink)
935-960MHz(Downlink) 1805-1880MHz(Downlink)
ARFCN 1-124 ARFCN 512-885
E-GSM - Extended GSM GSM1900/PCS1900
Frequency 880-915MHz(Uplink) Frequency 1850-1910MHz(Uplink)
925-960MHz(Downlink) 1930-1990MHz(Downlink)
ARFCN 975-1023 ARFCN 512-810
23. GSM Radio Interface
23
Logical Channels
Broadcast Channels Traffic Channels Control Channels
BCCH/EBCCH Common Control Dedicated Control
FCCH
RACH SDCCH
SCH
AGCH SACCH
NCH
PCH FACCH
24. GSM Radio Interface.
24
+4 dB
- 6 dB
+1.0 dB
-1.0 dB - 6 dB
Channel structure.
Broadcast Control Channel (BCCH)
147 “Useful” bits
- 30 dB 542.8 µ secs - 30 dB Stand-alone Dedicated Control
Channel (SDCCH)
- 70 dB - 70 dB
10 µs 8 µs 10 µs
3 57 bits 1 26 bits 1 57 bits 3 10 µs 8 µs 10 µs Common Control Channel (CCCH)
148 “Active” Bits 546.42 µsec Random Access Channel (RACH)
Paging Channel (PCH)
Access Grant Channel (AGCH)
F F Down Link Traffic Channel (TCH)
0 1
Slow Associated Channel
(SACCH)
Fast Associated Channel
(FACCH)
25. GSM Radio Interface cont..
25
Speech Coding
20 msec sample
260 bits per sample
Channel coding and modulation
Class Ia 50 bits - most sensitive to bit errors.
Class Ib 132 bits - moderately sensitive to bit errors.
Class II 78 bits - least sensitive to bit errors
1/2 rate convolution coding gives 456 bits
456 bits are divided into 8 blocks of 57 bits.
Blocks from two 20 msec sample are interleaved.
26. GSM Protocol Architecture
26
MS BSS MSC
CM Radio Interface A - Interface CM
MM MM
BSSAP
RR BSSAP
RR SCCP SCCP
LAPDm LAPDm
MTP MTP
TDMA/FDMA TDMA/FDMA
29. Introduction to GPRS
29
Architecture of GPRS system.
SM E SM -S C TE
SM S Pac k et
Gatew ay/IW F
D ata
E C N etw ork
HLR/ GR
M SC/ VLR D
Gd
Gi
TE Gs Gr Gc
A EI R
Gf
PCU
BSS Gb SGSN Gn GGSN
m
U
Gn
Other PLMN
S GS N
GGS N Ot her SGSN - Serving GPRS Support Node
SGS N
B order GGSN - Gateway GPRS Support Node
Gatew ay
BG Ga
Gp
TE - Terminal Equipment.
R Inter-P LMN Charging
N etw ork
Gateway
Ac c ounting
C enter
30. GPRS Channel Structure
30
Multi slot operation.
Asymmetric channel allocation.
Need based (dynamic) allocation.
Group Channel Function Direction
Packet data traffic channel PDTCH Data traffic MS BSS
Packet broadcast control channel control PBCCH Broadcast MS BSS
Packet common control channel (PCCCH) PRACH Random access MS BSS
PAGCH Access grant MS BSS
PPCH Paging MS BSS
PNCH Notification MS BSS
Packet dedicated control channels PACCH Associated control MS BSS
PTCCH Timing advance control MS BSS
31. GPRS Transmission Plane
31
Application
IP / X.25 IP / X.25
Relay
SNDCP SNDCP GTP-U GTP-U
LLC LLC UDP / UDP /
Relay TCP TCP
RLC RLC BSSGP BSSGP
IP IP
MAC MAC Network Network L2 L2
Service Service
GSM RF GSM RF L1bis L1bis L1 L1
Um Gb Gn Gi
MS BSS SGSN GGSN
32. GPRS Signaling Plane
32
GMM/SM GMM/SM
LLC LLC
Relay
RLC RLC BSSGP BSSGP
MAC MAC Network Network
Service Service
GSM RF GSM RF L1bis L1bis
Um Gb
MS BSS 2G-SGS
N
40. Comparison between 2G, 2G+ and
3G
40
Feature 2G 2G+ 3G
Core Network MSC/VLR, GMSC, MSC/VLR, GMSC, 3G MSC/VLR (with added
HLR/AuC/EIR SGSN,GGSN, HLR/AuC/EIR, interworking and transcoding),
CGF GMSC, HLR/AuC/EIR, 3G-
MM, CM, BSSAP, SCCP, SGSN, GGSN, CGF
ISUP,TCAP, MAP, MTP 3, GMM/SM/SMS, MM, CM,
MTP 2, MTP 1 GTP, SNDCP,NS, FR, GMM/SM,MM,CM,BSSAP,
LLC,BSSGP, BSSAP, RANAP,GTP,SCCP, MTP3B,
TDM transport BSSAP+,SCCP, TCAP, MAP, M3UA, SCTP, Q.2630.1
ISUP,MTP 3, MTP 2, MTP 1 (NNI), TCAP, MAP, ISUP,
MTP 3, MTP 2, MTP 1,
TDM, Frame Relay transport Q.2140, SSCOP
ATM, IP transport
Radio Access BTS, BSC, MS BTS, BSC, MS Node B, RNC, MS
FDMA, TDMA, CDMA TDMA, CDMA, EDGE W-CDMA, CDMA2000, IWC-
136
MM, CM, RR, LAPDm, MAC, RLC,
LAPD, BSSAP, SCCP, GMM/SM/SMS,LLC, SNDCP, GMM/SM, MAC, RLC,
MTP 3, MTP 2, MTP 1 BSSGP, NS,FR,RR,BSSAP, PDCP,RRC,Q.2630.1(UNI+N
SCCP, MTP 3,MTP 2, MTP 1 NI),NBAP, RNSAP,RANAP,
SCCP, MTP3B, M3UA,
SCTP, GTP-U, Q.2140,
Q.2130, SSCOP,CIP
Handsets Voice only terminals New type of terminal New type of terminal
Multiple modes
Dual mode TDMA and CDMA Voice, data and video
terminals
Voice and data terminals WAP, multimedia mgmt
WAP, no multimedia support
41. Comparison between 2G, 2G+ and 3G
cont...
41
Databases HLR, VLR, EIR, AuC HLR, VLR, EIR, AuC Enhanced HLR, VLR,
EIR,AuC
Data Rates Up to 9.6 Kbps Up to 57.6 Kbps (HSCSD) Up to 2Mbps
Up to 115Kbps (GPRS)
Up to 384 Kbps (EDGE)
Applications Advanced voice, Short SMS, Internet Internet, multimedia
Message Service (SMS)
Roaming Restricted, not global Restricted, not global global
Compatibility Not compatible to 3G Not compatible to 3G Compatible to 2G, 2G+ and
Bluetooth
43. Co-Channel Reuse Factor
43
For hexagonal Cells the
reuse Factor is
D/R = (3N) ^ 0.5
N can be 3,4 or 7
44. Worst Case Co-Channel interference
44
C/I = 6.3 db With N=3
C/I = 9.2 db With N=4
D
C/I = 14.3 db With
D+R D-R N=7
Desired is 12db in fwd
D+R D-R ch and 9 db rev ch
D
45. Worst Case Co-Channel interference
45
C/I = 15 db With N=3
C/I = 17.1 db With
D+0.7R
N=4
D+0.7R D
C/I = 21.1 db With
N=7
D D-0.7R
D-0.7R
46. Different Picture
46
SGSN HLR
BTS
MAP-C
Gs MAP-D
BTS BSC MSC/VLR GMSC
MAP-E
BTS
MSC/VLR
Um Abis A-Int.
47. What is PLMN Selection?
47
The Mobile Station upon Switch-On will attempt to find its Home PLMN. The Mobile Station will scan
through frequencies looking for Home PLMN. Scanning frequencies will be based on list’s
available in the SIM.
BCCH List
Preferred PLMN List
Forbidden PLMN List
BA Range
Modes of PLMN Selection:
Manual Mode
All PLMN’s found by the Mobile Station after switching on are presented to the Subscriber. The
subscriber can select the PLMN and the Mobile station will attempt to access that PLMN.
Automatic Mode
A search is conducted for the Preferred PLMN (generally is the home PLMN network) and the Mobile
station automatically accesses the home PLMN.
48. What is Cell Selection?
48
Cell Selection is the process used by the Mobile Station to ‘Camp On’ to the
best cell available when a MS is Switched ON.
Steps Involved:
• The Mobile Station reads the SI on the cell of the chosen PLMN,
measures RLA ,reads the Neighbor cell list(BA List) and C1 criteria.
• The Mobile Station reads the SI on the cells of the BA List, measures
RLA and C1 criteria for each cell.
• The Mobile Station compares the calculated the C1 of all the cells and
‘Camps On’ to the cell with largest C1 value.
Note:
C1 = RLA – RXLEV_ACCESS_MIN – max(MS_TXPWR_MAX_CCH – MSPC, 0)
49. What is Cell Re-Selection?
49
When camped on a cell, the mobile shall regularly search for a better cell
according to the cell reselection criteria. If a better cell is found, that cell is
selected. This process is identified as the 'C2’ or ‘C32’ in the GSM system.
C2 Cell Criteria is a Phase 2 refinement to the C1 criterion. It adds an offset
margin in db to C1 which can make a Particular cell appear more attractive
or less attractive as a selection candidate.
Note:
C2 =( C1 + CELL_RESELECT_OFFSET) - (TEMP_OFFSET for PENALTY_TIME)
50. What is Location Update?
50
Location Update is the process of informing the Network about the Location of
the MS (Mobile Subscriber)
Types of Location Updates:
IMSI Attach
Normal Location Update
Periodic Location Update
51. What is Handover?
51
Definition:
• The Handover process allows to change the serving cell without loosing
the call in progress.
The reasons for performing handover :
• Distance (or propagation delay)between MS and BTS is
too big
• Receive signal quality (RXQUAL)becomes too bad
• Receive signal level (RXLEV)becomes too bad
• Path loss for the MS to other cell is better
• Duration that MS stays in a cell
Types of Handover:
• Intra Cell Handover
• Inter Cell Handover
• Intra BSC Handover
• Inter BSC Handover
