C OMMUNICATION S ECURITY L ECTURE 3: I NTRODUCTION TO C ELLULAR M OBILE N ETWORKS Dr. Shahriar Bijani Shahed University Spring 2016

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

O UTLINE Circuit Switching vs. Packet Switching Multiplexing Mobile Phone Standards Figures 3

C IRCUIT S WITCHING CIRCUITSWITCH CIRCUITSWITCH CIRCUITSWITCH CIRCUITSWITCH CIRCUITSWITCH

P ACKET S WITCHING PACKETASSEMBLER/DISASSEMBLER PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH

P ACKET S WITCHING PACKETASSEMBLER/DISASSEMBLER PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH

P ACKET S WITCHING PACKETASSEMBLER/DISASSEMBLER PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH

P ACKET S WITCHING PACKETASSEMBLER/DISASSEMBLER PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH

P ACKET S WITCHING PACKETASSEMBLER/DISASSEMBLER PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH

P ACKET S WITCHING PACKETASSEMBLER/DISASSEMBLER PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH

P ACKET S WITCHING PACKETASSEMBLER/DISASSEMBLER PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH

A DVANTAGES OF P ACKET S WITCHING 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

A DVANTAGES OF C IRCUIT S WITCHING 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)

P ACKET R OUTING S TRATEGIES 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

P ACKET D ATA D ELIVERY Acknowledged 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

P ACKET S WITCHING T ECHNOLOGIES X.25 Frame Relay ATM

T HE V IRTUAL C IRCUIT (VC) C ONCEPT PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH PACKET SWITCH Virtual Circuit

V IRTUAL C IRCUIT C ONNECTIONS 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

O UTLINE Circuit Switching vs. Packet SwitchingMultiplexing Mobile Phone Standards Figures 19

M ULTIPLEXING 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. Different methods: Frequency Division Multiplexing (FDM) Time Division Multiplexing (TDM) Code Division Multiplexing (CDM) Beam Division Multiplexing (BDM) 20

F REQUENCY D IVISION M ULTIPLEXING (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) 21

F REQUENCY D IVISION M ULTIPLEXING (FDM) (a) The original bandwidths. (b) The bandwidths raised in frequency. (c) The multiplexed channel. 22

F REQUENCY D IVISION M ULTIPLEXING Orthogonal frequency division multiplexing (OFDM). 23

T IME D IVISION M ULTIPLEXING (TDM) 24 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.

C ODE D IVISION M ULTIPLE A CCESS (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. 25

B EAM D IVISION M ULTIPLE A CCESS (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. 26

M ULTIPLE -A CCESS R ADIO T ECHNIQUES Courtesy of Petri Possi, UMTS World

Courtesy of Suresh Goyal & Rich Howard CDMA

Courtesy of Suresh Goyal & Rich Howard CDMA

Courtesy of Suresh Goyal & Rich Howard CDMA

Courtesy of Suresh Goyal & Rich Howard CDMA

C ODE D IVISION M ULTIPLEXING (1) (a) Chip sequences for four stations. (b) Signals the sequences represent 32

C ODE D IVISION M ULTIPLEXING (2) (a) Six examples of transmissions. (b) Recovery of station C’s 33

A NALOG VS. D IGITAL T ELEPHONE S YSTEMS 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) 34

W IRELESS I NTERNET VS. C ELLULAR N ET The Internet - Wireless Networks Classic Cellular Telecommunications Networks Designed for voice, not for Internet access 35

O UTLINE Circuit Switching vs. Packet Switching Multiplexing Mobile Phone Standards Figures 36

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

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M OBILE P HONE S TANDARDS 40

A C OMPARISON OF A LL M OBILE G ENERATIONS Technology Features 1G2G3G4G5G Start/ Deployment 1970 / / / / Data Bandwidth 2kbps64kbps2Mbps200Mbs/ 1 Gbps1 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 FDMATDMA, CDMACDMA CDMA, BDMA Switching CircuitCircuit, Packet(Circuit,) PacketAll Packet Core Network PSTN Packet NetworkInternet Handoff Horizontal Horizontal and Vertical

M OBILE N ETWORKS ’ F IGURES 42 Compound Annual Growth Rate

Mobile Usage 43 Source: Ericsson, Nov Compound Annual Growth Rate

Total number of mobile subscribers in Q3 2015: ~7.3 billion 87 million new subscribers 44 Source: Ericsson, Nov. 2015

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47 average 1.7% of Android smartphone users upgraded to a new Android smartphone

Wi-Fi traffic is not included. Average data consumption increases between 20% and 45% per subscription after smartphone model upgrades 48

I RAN ’ S F IGURES Source: GSMA Intelligence 2016 Q Connections: 113.9M 4.90% (annual growth) Prepaid71% -1.07% mobile broadband (includes 3g & 4G)14% 2,125% Population79.6M 1.21% SIM penetration143% 3.66% 49