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CPET 565 Mobile Computing Systems

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1 CPET 565 Mobile Computing Systems
Lecture 2 Introduction to Wireless Communication and Networking Hongli Luo Indiana University-Purdue University Fort Wayne

2 Wireless Networking WAN : Wide Area Network MAN: Metro Area Network
LAN: Local Area Network PAN: Personal Area Network

3 Wireless Networking Technologies
Satellite (WAN) Microwave (MAN) WiMax - Broadband Wireless (MAN) standard Cellular (WAN) Wireless LANs (WLAN) – Wi-Fi standards Bluetooth (Wireless PAN) IrDA (Infrared Data Association) Wireless point-to-point PAN RFID Sensor Network Standard ZigBee – a protocol for sensor network

4 Wireless Networks IEEE 802.11 or WiFi IEEE 802.15 IEEE 802.16 or WiMax
Wireless LANs – up to 100 meters IEEE Bluetooth technology over short distance IEEE or WiMax WiMax – World Interoperability for Microwave Access Provide wireless broadband service over longer distance Aimed at support mobility at speeds at miles per hour Wireless WANs Cellular telephone networks Satellite networks

5 Characteristics of selected wireless link standards
200 802.11n 54 802.11a,g 802.11a,g point-to-point data 5-11 802.11b (WiMAX) 4 3G cellular enhanced UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO Data rate (Mbps) 1 802.15 .384 UMTS/WCDMA, CDMA2000 3G .056 IS-95, CDMA, GSM 2G Indoor 10-30m Outdoor 50-200m Mid-range outdoor 200m – 4 Km Long-range outdoor 5Km – 20 Km

6 Electromagnetic spectrum for wireless communication
From Figure 7.17 of Data Communications and Networking by Forouzan, 4th

7 Figure 14.14 Industrial, scientific, and medical (ISM) band
From Figure of Data Communications and Networking by Forouzan, 4th

8 Wireless: Problems Typically much slower than wired networks
“State of the art” wireless LAN: 54Mb/sec Wired LAN: Mb/sec+ Higher transmission bit error rates (BER) Uncontrolled population Difficult to ensure Quality of Service (QoS) Asymmetric bandwidth Limited communication bandwidth aggravates the problem of limited battery life

9 Satellite Altitude of satellites is classified as
GEO, MEO, LEO Used for TV broadcasting, telephone, internet access GEO (Geosynchronous/Geostationary) Remains "stationary" relative to equator Deployed at around 36,000 km above the earth Need only 3 to cover earth High latency (1/4 sec or so round trip) Need high-power transmitter to reach satellite TV program

10 Satellite (2) LEO (Low Earth Orbit) MEO (Middle Earth Orbit)
Much lower orbits—less than 1000 km Must have handoff mechanism from one satellite to another don't appear stationary to earthbound base stations Lower power transmitter than GEO Lower latency, but needs handoff delay MEO (Middle Earth Orbit) ~10,000 km, between LEO and GEO Application: GPS (Global Positioning System)

11 Satellite: DirecPC/DirecWAY
Now as HughesNet, Provides satellite broadband Internet access ~400Kb/sec downlink from GEO Previously, only upload link with a dial-up modem connection, but now 2-way Dish must see the sky (typical of satellite) HUGE latency compared to DSL or cable modems

12 Microwave Common type of antenna – parabolic dish
Range: 20 miles or more, typically less To achieve long-distance transmission, a series of microwave relay towers is used. Line of sight only Rain causes problems, because rain absorbs microwave energy Bandwidth: 12 Mbps ~ 200 Mbps Used for voice and television transmission, or short point-to-point links

13 Cellular Phone Network
Mobile Cellular Phone Communication Infrastructures 1G 2G 2.5G 3G

14 Cellular Phone System List of Mobile Network Operators,

15 Mobile Network Operators
T-Mobile (Germany) GSM, GPRS, EDGE, UMTS, HSDPA (High Speed Downlink Packet Access) Cingular (U.S.) GSM, GPRS, EDGE, UMTS, HSDPA (TDMA) Verizon (U.S.) CDMA, CDMA2000 1x, EV-DO (Evolution-Data Optimized data standard) Sprint/Nextel (U.S.) CDMA, CDMA2000 1x, EV-DO, iDEN (Integrated Digital Enhanced Network)

16 Mobile Communication Infrastructures
1G Analog FM 2G TDMA-FDMA/ CDMA (Code Division Multiple Access) 2.5 G – extend 2G system by adding packet-switched connection GPRS (General Packet Radio Service; for data packet service on GSM network) EDGE (Enhanced Data GSM Evolution, up to 384 Kbps) - a transition to 3G by Cingular that used TDMA for 2G Support WAP, search, directory services, etc 3G

17 The Mobile Telephone System
1 G Mobile Phone Analog voice 2 Generation Mobile Phone 2.5 G 3 G Reference: Wikepedia, the free encyclopedia,

18 1st Generation Cellular Phone System
Advanced Mobile Phone Service (AMPS) Invented by Bells Labs and first installed in the U.S. in 1982 Analog FDMA (Frequency Division Multiple Access) ISM 800-MHz band Base Station → Mobile Station: forward communication channels ( MHz: 25 MHz band) Base Station ← Mobile Station: reverse communication channels ( MHz: 25 MHz band) Voice channel – Frequency modulation (30 kHz) Control Channels - FSK (Frequency Shift Keying) – 10 kbps/30 kHz signal No of Channels 832 channels: 25 MHz / 30 kHz, can be shared by two providers Each provider: 416 channels in each cell , 21 channels for control, 395 channels for voice Frequency Reuse Factor Each cell uses some set of frequencies not used by any of its neighbors Reuse factor 7

19 Cellular bands for AMPS
From Figure 16.3 of Data Communications and Networking by Forouzan, 4th

20 AMPS reverse communication band
From Figure 16.4 of Data Communications and Networking by Forouzan, 4th

21 Frequency Reuse Factor 4

22 Frequency Reuse Factor 7

23 2nd Generation Cellular Telephone System
D-AMPS (Digital AMPS) IS-136 TDMA-FDMA GSM (Global System for Mobile Communication) IS-95 CDMA (Code Division Multiple Access) CDMA-FDMA

24 Digital Advanced Mobile Telephone System (D-AMPS)
D-AMPS (Digital AMPS) Backward compatible with AMPS: FDMA First defined by IS-54 (Interim standard 54) and later revised by IS-136 TDMA (Time Division Multiple Acceess)/IS-136 Added to each sub-band Triple the no. of channels ISM 800 MHz band MHz range: Base station → Cellular phone (forward channels) MHz range: Cellular phone →Base station (reverse channels)

25 Voice Signal Digitization
D-AMPS (continue) Voice Signal Digitization Digitizing: PCM (Pulse Code Modulation) and compression 3 kHz → PCM Digitized →7.95 kbps digital voice channel TDMA 1 slot – 7.95 kbps 3 slots: 48.6 kbps digital data: 3 x 7.95 kbps Combined using TDMA TDMA Frame [ ]

26 D-AMPS (continue) Digitized Voice Signal Transmission
25 frames per second 1944 bits per frame Each frame last 40 ms (1/25) and is divided into 6 slots shared by three digital channels: TDMA [ ] Each channel: 2 slots 324 bits per slot: 159 bits digitized voice, 64-bits control, 101-bits for error correction QPSK Modulation (Quadrature Phase-Shift Keying) 48.6 kbps → QPSK Modulation → 30 kHz analog signal FDMA 25 MHz band, 30 kHz analog signal Reuse Factor 7

27 D-AMPS From Figure 16.6 of Data Communications and Networking by Forouzan, 4th

28 GSM (Global System for Mobile Communication)
Digital mobile telephony system launched in Finland in 1991 Use time division multiplexing (TDMA), Digitize and compress data 900 MHz or 1800 MHz frequency band SIM cards (Subscriber Identity Module) Capture 82.4% of all global mobile connection Widely used in Europe and Asia

29 GSM (continue) Bands Transmission Reuse Factor 3
2 bands, each band 25 MHz 124 Channels of 200 kHz separated by guard bands Transmission Voice channel → Digitize + Compress → 13-kbps digital signal 1 slot = bit 1 Frame (TDMA) = 8 slots; frame duration 120 ms A Multi-frame = 26 frames (TDMA) = kbps 26 frames = 24 traffic frames + 2 control frames 270.8 kbps → GMSK → 200 kHz signal (FDMA) Reuse Factor 3

30 GSM From Figure 16.8 of Data Communications and Networking by Forouzan, 4th

31 IS-95 CDMA Based on CDMA (Code Division Multiple Access) and DSSS (Direct Sequence Spread Spectrum) Wireless Communications, Chapter Network Concepts and Standards, IS95 CDMA Cellular Telephony, Springer, Bands and Channels Duplex using two bands ISM 800-MHz or ISM 900-MHz 20 Channels of MHz, guard bands 10 channels for each provider Can be used in parallel with AMPS 1 IS-95 Channel = 41 AMPS channels (41 x 30 kHz = 1.23 MHz)

32 IS-95 CDMA (cont.) Base Channel Synchronization
Base stations use GPS (Global Positioning System) Forward Transmission (base to mobile) 64 Digital Channels (3 kHz each) Voice 3 kHz → 9.6 kbps → Error-correcting & repeating bits → 19.2 kbps Scrambling signal: ESN (Electronic Serial No of mobile station) pseudo random chip → Decimator (1 out of 64 bits) 64 channels x 64 Walsh code → CDMA 1.228 Mcps (Megachips per second) = 19.2 kbps * 64 cps QPSK → MHz 25MHz Band: 20 Channels FDMA Channel 0: Pilot Channel, sends [1, 1, 1, 1, …] for bit sync Ch 1 – 7: paging, send messages to one or more mobile devices Ch 8–31 and 33-63: voice traffic channels Ch 32: give info about the system

33 IS-95 CDMA (cont.) Reverse Transmission (Mobile to Base)
3 kHz Voice → Digitizer → 9.6 kbps → Error correcting & repetition → 28.8 kbps → 6-symbol chuck, 0-64, Symbol Modification → kbps = (28.8/6) x 64 ESN → Long Code Generator 42-bit → Mcps DSSS (Direct Sequence Spread Spectrum) 94 Channels 62 Traffic channels 32 Base station access control channels 1.28 Mcps → QPSK → MHz FDMA 20 channel x MHz = 25 MHz

34 IS-95 CDMA (cont.) Soft Handoff
A mobile station can communicate with two base stations at the same time A call is rarely dropped during the handoff

35 IS-95 forward transmission
From Figure of Data Communications and Networking by Forouzan, 4th

36 IS-95 reverse transmission
From Figure of Data Communications and Networking by Forouzan, 4th

37 3rd Generation Technologies
A Combination of Technologies Audio and Video VoIP Still & Moving Images Digital Data UTMS (Unified Mobile Telephone Service) Enhanced multimedia: movie, images, music Internet Surfing Video telephony, Video conferencing Always connected infrastructure

38 3rd Generation Technologies
IMT-2000 (Internet Mobile Communication 2000) Voice quality (public telephone network) Data rate 144 kbps for access in a moving vehicle 384 kbps for access as the user walks 2 Mbps for stationary user (office or home) Support packet-switched and circuit-switched data services 2 GHz band 2 MHz Bandwidth Interface to Internet

39 3rd Generation Technologies
WCDMA (wideband CDMA) Used by most GSM cellular providers CDMA2000 Code Division Multiple Access Pioneered by Qualcomm Used by most CDMA providers Used by Verizon Wireless and Sprint

40 Wireless LANs One example: IEEE 802.11 standard
CSMA/CA instead of CSMA/CD, as in Ethernet Ethernet: detect collision during transmission Wireless: impossible: can only hear own signal during transmission Current speeds 1Mb/sec – 54Mb/sec Access point / NIC prices have recently dropped substantially 802.11b: 2-11Mb/sec (we have this) in 2GHz range 802.11a: 54Mb/sec in 5GHz range (incompatible with b, very dependent on line of sight) 802.11g: ~20Mb/sec, compatible with b

41 802.11 Details Medium-range wireless local area network technology
2.45GHz Industrial, Scientific, Medical (ISM) Band Old: 1Mb/sec , now: Mb/sec transmission speeds Older 1Mb/sec spec used Frequency Hopping Spread Spectrum (FHSS) Units change frequency rapidly according to an agreed channel hopping sequence Helps to reduce interference Higher data rates use Direct Sequence Spread Spectrum (DSSS) Radio Units broadcast a broad, redundant signal that is resistant to interference US: 11 distinct channels (partially overlapping) Three channels (1, 6, 11) do not overlap at all

42 802.11: Future Revisions to standards for security
802.1X / i (later) 802.11a: 54Mb/sec, 5GHz 802.11g: ~20Mb/sec, compatible w/ b 802.11a has more non-overlapping channels than b 802.11b 3 non-overlapping channels 802.11a channels do not overlap


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