1. Dr. Shahriar Bijani Shahed University Spring 2016
Communication Security Lecture 3: Introduction to Cellular Mobile Networks
Dr. Shahriar Bijani
Shahed University
Spring 2016

2. Main References
A. S. Tanenbaum and D. J. Wetherall, Computer Networks (5th Edition), Pearson Education, the book slides, 2011.
Patrick Traynor, CS Cellular and Mobile Network Security, Georgia Tech Information Security Center, 2012.
General Packet Radio Service (GPRS) For Engineers, Aircom International.

3. Outline Circuit Switching vs. Packet Switching Multiplexing
Mobile Phone Standards
Figures

4. Circuit Switching CIRCUIT CIRCUIT SWITCH SWITCH CIRCUIT SWITCH CIRCUIT

5. Packet Switching 1 2 3 5 4 1 2 3 4 5 PACKET PACKET SWITCH ASSEMBLER/
DISASSEMBLER
PACKET
SWITCH

6. Packet Switching 1 2 3 5 4 1 2 3 4 5 PACKET PACKET SWITCH ASSEMBLER/
DISASSEMBLER
PACKET
SWITCH 1 2 3

7. Packet Switching 1 2 3 5 4 1 2 3 4 5 PACKET PACKET SWITCH ASSEMBLER/
DISASSEMBLER
PACKET
SWITCH 1 2 3

8. Packet Switching 1 2 3 5 4 1 2 3 4 5 PACKET PACKET SWITCH ASSEMBLER/
DISASSEMBLER
PACKET
SWITCH 1 2 3

9. Packet Switching 1 2 3 5 4 1 2 3 4 5 PACKET PACKET SWITCH ASSEMBLER/
DISASSEMBLER
PACKET
SWITCH 2 1 3

10. Packet Switching 1 2 3 5 4 1 2 3 4 5 PACKET PACKET SWITCH ASSEMBLER/
DISASSEMBLER
PACKET
SWITCH
PACKET
SWITCH 2 3 1
PACKET
SWITCH 2 3 1
PACKET
SWITCH
PACKET
SWITCH

11. Packet Switching 1 2 3 5 4 1 2 3 4 5 PACKET PACKET SWITCH ASSEMBLER/
DISASSEMBLER 1 2 3
PACKET
SWITCH
PACKET
SWITCH 1 2 3 2 1 3 2 3 1
PACKET
SWITCH 1 2 3 2 3 1
PACKET
SWITCH
PACKET
SWITCH

12. Advantages of Packet Switching
More efficient use of existing carriers
More suited to bursty-type traffic such as Internet access.
Compatibility with existing packet-switched networks (PSNs) such as the Internet

13. Advantages of Circuit Switching
More suited to time-sensitive applications
No contention for network resources
Less data overheads for routing requirements
Compatibility with existing circuit-switched networks (eg PSTN/ISDN)

14. Packet Routing Strategies
Connection-Orientated (CONS):
Packet route established prior to data transfer
Supports flow control
Supports QoS functions
Connectionless (CNLS)
No predefined route - packets routed individually
No guarantee of delivery
Difficult to implement QoS

15. Packet Data Delivery Acknowledged Mode: Unacknowledged Mode
Guarantees error-free delivery
Supports flow control
Requires additional overheads
Lower data throughput
Unacknowledged Mode
Packets are delivered to the network and forgotten
No indication of delivery or error correction
Generally relies on higher layer protocols for error detection and correction
More efficient in reliable networks

16. Packet Switching Technologies
X.25
Frame Relay
ATM

17. The Virtual Circuit (VC) Concept1 2 3
PACKET
SWITCH
PACKET
SWITCH 1 2 3 2 1 3 2 3 1
PACKET
SWITCH 1 2 3 2 3 1
PACKET
SWITCH
PACKET
SWITCH
Virtual Circuit

18. Virtual Circuit Connections
Permanent Virtual Circuit (PVC):
Established by NMC
Dedicated resource for specific user
Connectionless
Switched Virtual Circuit (SVC):
Setup on request
Temporary allocation of resources
Cleared on completion of session

19. Outline Circuit Switching vs. Packet Switching Multiplexing
Mobile Phone Standards
Figures

20. Modulation & Multiplexing
Modulation: To send digital information, we must change analog signals to represent bits.
includes:
sampling
quantizing
Encoding
Example: PCM (Pulse Code Modulation)
the simplest form of speech coding
2 standards: A-law in Europe (24-channels), and µ-law in the USA (30/32 channels).
Multiplexing: sharing one channel by multiple signals
Using a single channel (wire) to carry several signals is better than to allocate a channel (install a wire!) for every signal.
PCM Reference:

21. Multiplexing Different multiplexing methods:
Frequency Division Multiplexing (FDM)
Time Division Multiplexing (TDM)
Code Division Multiplexing (CDM)
Beam Division Multiplexing (BDM)

22. Frequency Division Multiplexing (FDM)
AKA: Frequency Division Multiple Access (FDMA)
FDM:
divides the spectrum into frequency bands
each user having exclusive ownership of some band to send their signal.
E.g.: AM radio.
The allocated spectrum is about 1 MHz (~ 500 to ~1500 kHz)
Different frequencies are allocated to different logical channels (stations)
AM radio uses amplitude modulation vs FM (frequency modulation) radio

23. Frequency Division Multiplexing (FDM)
(a) The original bandwidths. (b) The bandwidths raised in frequency. (c) The multiplexed channel.

24. Frequency Division Multiplexing
Orthogonal frequency division multiplexing (OFDM).

25. Time Division Multiplexing (TDM)
AKA: Time Division Multiple Access (TDMA)
TDM is used widely as part of the telephone and cellular networks.
TDM is different from STDM.
STDM (Statistical Time Division Multiplexing):
Channel is allocated according to the statistics of each stream’s demand
STDM is packet switching.

26. Code Division Multiple Access (CDM)
AKA: Code Division Multiple Access (CDMA)
Narrowband signal is spread over a wider frequency band.
Advantages:
More tolerant of interference,
Allowing multiple signals from different users to share the same frequency band.

27. Beam Division Multiple Access (BDM)
AKA: Beam Division Multiple Access (BDMA)
New access technique for 5th generation of mobile wireless communication.
The base station allocates separate antenna beams to each of the mobile devices.
Based on position and moving speed, base station will calculate both width and direction of the beam for all the mobile stations.
BDMA helps in achieving higher system capacity.

28. Multiple-Access Radio Techniques
Courtesy of Petri Possi, UMTS World

29. CDMA
Courtesy of Suresh Goyal & Rich Howard

30. CDMA
Courtesy of Suresh Goyal & Rich Howard

31. CDMA
Courtesy of Suresh Goyal & Rich Howard

32. CDMA
Courtesy of Suresh Goyal & Rich Howard

33. Code Division Multiplexing (1)
Chip sequences for four stations.
Signals the sequences represent

34. Code Division Multiplexing (2)
Six examples of transmissions.
Recovery of station C’s

35. Analog vs. Digital Telephone Systems
Analog/ Digital telephone systems:
Analog is the translation of voice into electrical impulses (pure waveform).
Cheap
Low bandwidth (limited data communication).
Noise
Digital is an approximation of the waveform, represented in 0s and 1s
Expensive
High bandwidth
Better voice (less noise)

36. Wireless Internet vs. Cellular Net
The Internet - Wireless Networks
Classic Cellular Telecommunications Networks
Designed for voice, not for Internet access

37. Outline Circuit Switching vs. Packet Switching Multiplexing
Mobile Phone Standards
Figures

39. Upgrade paths from 2G Technologies to 3G
IS-95
IS-136 & PDC
GSM-
EDGE
GPRS
HSCSD
IS-95B
Cdma2000-1xRTT
Cdma2000-1xEV,DV,DO
Cdma2000-3xRTT
W-CDMA
TD-SCDMA 2G 3G
2.5G
3GPP
3GPP2
Source: ICIL

41. Mobile Phone Standards

42. A Comparison of All Mobile Generations
Technology
Features 1G 2G 3G 4G 5G
Start/ Deployment
1970 / 1984
1980 / 1999
1990 / 2002
2000/ 2010
2020
Data Bandwidth
2kbps
64kbps
2Mbps
200Mbs/ 1 Gbps
1 Gbps +
Standard
TACS, AMPS
(Analog Cellular Technology)
TDMA, CDMA, GSM, GPRS, EDGE
(Digital)
WCDMA,
CDMA-2000, HSPA
WiMax , LTE,
Wi-Fi
Unified IP & seamless combination of broadband , LAN, WAN, PAN,WLAN & www
Service
Mobile Telephony (Voice)
Digital voice, SMS, Higher capacity packetized data
Integrated high quality audio, video and data
Dynamic Information access, Wearable devices
Dynamic Information access, Wearable devices with AI capabilities
Multiplexing
FDMA
TDMA, CDMA
CDMA
CDMA, BDMA
Switching
Circuit
Circuit, Packet
(Circuit,) Packet
All Packet
Core Network
PSTN
Packet Network
Internet
Handoff
Horizontal
Horizontal and Vertical
BDMA: Beam-Division Multiple Access

43. GSM / 3GPP Releases GSM Phases 3GPP Releases GSM Phase 1 1992
3GPP Releases
GSM Release
Start Date
GSM Phase 1
 1992
GSM Phase 2
 1994
GSM Phase 2+
 1997
GSM Phase 2+ Release 97
 1998
GSM Phase 2+ Release 98
 1999
GSM Phase 2+ Release 99
(3GPP UMTS Release 99)
2000
Release
Start Date
Release 4 (all IP)
2001 …
Release 7
2007-8
Release 8 (LTE)
 2008-9
Release 8 (LTE Advanced)
Release 13
2016
Release 14
2017

44. Mobile Networks’ Figures
Compound Annual
Growth Rate

45. Compound Annual
Growth Rate
Mobile Usage
Source: Ericsson, Nov. 2015

46. Total number of mobile subscribers in Q3 2015: ~7.3 billion
87 million new subscribers
Source: Ericsson, Nov. 2015

49. average 1.7% of Android smartphone users upgraded to a new Android smartphone

50. Wi-Fi traffic is not included.
Average data consumption increases between 20% and 45% per subscription after smartphone model upgrades

51. Iran’s Figures Q4 2015 Connections: 113.9M 4.90% (annual growth)
Source: GSMA Intelligence 2016
Q4 2015
Connections: M  % (annual growth)
Prepaid 71%  %
mobile broadband (includes 3g & 4G) 14%  2,125%
Population 79.6M 1.21%
SIM penetration 143%  3.66%