ITTC Mobile Wireless Networking The University of Kansas EECS 882 Physical Layer & MW Environment

Transcription

1 Mobile Wireless Networking The University of Kansas EECS 882 Physical Layer & MW Environment James P.G. Sterbenz Department of Electrical Engineering & Computer Science Information Technology & Telecommunications Research Center The University of Kansas 22 August 2011 rev James P.G. Sterbenz

2 Mobile Wireless Networking Physical Layer and Mobile Wireless Environment PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.3 Modulation, coding, and error control PL.4 Mobile wireless environment 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-2

3 Physical Layer Physical Layer Communication CPU R = network CPU M app M app end system end system D = 0 Physical layer communicates digital information through a communication channel in a medium digital bits are coded as electronic or photonic signals digital or analog coding over a link between nodes (layer 2) 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-3

4 Mobile Wireless Networking Physical Layer and Mobile Wireless Environment EECS 882 is a networking course but the operation of the network depends on characteristics of the communication channels physical environment Therefore brief non-mathematical introduction to physical layer details in EECS 865 review for EE folk important for CS and IT folk to understand why discussion of impact of mobility and wireless on network 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-4

5 Mobile Wireless Networking PL.1 Physical Media and Spectrum PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.3 Modulation, coding, and error control PL.4 Mobile wireless environment 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-5

6 Guided media wire twisted pair coaxial cable power line fiber optic cable Physical Media Guided role in communication networks? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-6

7 Guided media wire twisted pair coaxial cable power line fiber optic cable Physical Media Guided traditional Internet & PSTN mostly guided media EECS 780 and August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-7

8 Guided media wire twisted pair coaxial cable power line fiber optic cable Unguided media free space radio frequency optical Physical Media Unguided 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-8

9 Guided media wire twisted pair coaxial cable power line fiber optic cable Unguided media wireless free space radio frequency optical Physical Media Unguided networks with unguided media subject for EECS August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-9

10 Spectrum Wireless Free Space Spectrum range of frequencies available for communication λf = c ; c = km/s only some spectrum usable for communication which parts? [ 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-10

11 Spectrum Wireless Free Space Spectrum range of frequencies available for communication λf = c ; c = km/s RF: radio frequency frequency determines propagation characteristics [ 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-11

12 Spectrum Wireless Free Space Spectrum range of frequencies available for communication λf = c ; c = km/s RF: radio frequency optical infrared nm = THz 41 THz spectrum why not higher frequencies? [ 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-12

13 Spectrum Wireless Free Space Spectrum range of frequencies available for communication λf = c ; c = km/s RF: radio frequency optical higher frequencies: UV, x-ray, γ-ray, health risks of radiation exposure frequency beyond current transceiver technology propagation problems [ 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-13

14 Wireless Free Space Spectrum Table Band Range Propagation Usage Examples Name Description Frequencies Wavelength Sight ELF VF VLF LF MF HF VHF UHF SHF EHF IR ext. low Hz 10 1Mm GW home automation voice Hz km GW voice tel., modem very low 3 30kHz km GW atmos. noise submarine low kHz 10 1km GW daytime maritime medium kHz m GW daytime maritime, AM radio high 3 30MHz m SW daytime transportation very high MHz 10 1 m LOS temp, cosmic television, FM radio ultra high MHz mm LOS cosmic noise television, cell tel. super high 3 30GHz mm LOS O 2, H 2 O wireless comm. ext. high GHz 10 1mm LOS O 2, H 2 O vapor wireless comm. infrared 300GHz 400THz nm LOS optical comm. visible visible THz nm 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-14 LOS Attenuation

15 Wireless Free Space Communication and Radar Bands Communication band designations UHF, VHF, and SHF bands subdivided ITU-T B.15 and ITU-R V IEEE Std August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-15

16 Wireless Free Space Communication and Radar Bands Band Range Usage Examples Name Partition Frequencies Wavelength VHF UHF 300MHz 1GHz mm television, p2p radio L UHF 1 2GHz mm cordless and mobile phones, satellite S C 4 8GHz 75 40mm PSTN relay, satellite, WLAN X 8 12GHz 40 25mm satellite links K u SHF 12 18GHz 25 17mm satellite links K 18 27GHz 17 10mm satellite, µwave links K a 27 40GHz mm satellite, WMAN V W VHF EHF MHz 2 4GHz 40 75GHz GHz mm GHz 27.77µm 10 1 m television, FM radio mm WLAN, WPAN, WMAN, satellite µm emerging WLAN, WMAN 40 27µm future future 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-16

17 Spectrum allocation what is it? Wireless Spectrum Allocation 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-17

18 Wireless Spectrum Allocation Spectrum allocation how to partition among: application broadcast radio, television, data communication, etc. 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-18

19 Wireless Spectrum Allocation Spectrum allocation how to partition among: application broadcast radio, television, data communication, etc. user sector consumer, business, government, military 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-19

20 Wireless Spectrum Allocation Spectrum allocation how to partition among: application broadcast radio, television, data communication, etc. user sector consumer, business, government, military assignees entity that is allowed to transmit into spectrum service providers and/or end users 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-20

21 Wireless Spectrum Allocation: Governance Governance of spectrum allocation International ITU-R: International Telecommunication Radio Sector R began as International Telegraph Union in 1865 now agency under UN mandate incentive for UN members to play nice 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-21

22 Wireless Spectrum Allocation: Governance Governance of spectrum allocation International ITU-R: International Telecommunication Radio Sector R National: government agency or appointee US FCC Federal Communications Commission UK Ofcom Office of Communications India TRAI Telecom Regulatory Authority of India etc. 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-22

23 Wireless Spectrum Regulation Regulations for transmission within allocation determined and enforced by governing bodies Parameters for allowed communication, e.g. transmission power field strength interference parameters transmission energy permitted outside allocation geographic limits date and time restrictions e.g. AM radio clear channel interference 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-23

24 Wireless Spectrum Enforcement Enforcement of transmission regulations enforcement by national entity e.g. US FCC EB (enforcement bureau) Can cause international tension e.g. former border blasters e.g. XETRA-AM (Mighty 690) in Tijuana Mexico now US-Mexico treaty coordinates AM transmission 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-24

25 Licensed spectrum Wireless Spectrum Licensing most frequency bands require license to transmit generally issued by national authority (FCC, Ofcom, etc.) e.g. broadcast TV, radio, amateur radio, GMRS e.g. mobile telephony 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-25

26 Licensed spectrum Wireless Spectrum Licensing most frequency bands require license to transmit generally issued by national authority (FCC, Ofcom, etc.) e.g. broadcast TV, radio, amateur radio, GMRS e.g. mobile telephony some unlicensed bands do not require license to transmit e.g. US CB (citizen band), FRS (family radio system) e.g. ISM for cordless telephones and wireless LANS 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-26

27 Licensed spectrum Wireless Spectrum Licensing most frequency bands require license to transmit generally issued by national authority (FCC, Ofcom, etc.) e.g. broadcast TV, radio, amateur radio, GMRS e.g. mobile telephony some unlicensed bands do not require license to transmit e.g. US CB (citizen band), FRS (family radio system) e.g. ISM for cordless telephones and wireless LANS unlicensed unregulated! 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-27

28 Licensed Spectrum Broadcast Radio and Television Allocation Frequency Range AM long wave khz AM medium wave khz broadcast radio AM short wave MHz transcontinental broadcast radio VHF TV ch. 2 4 ch. 5 6 FM radio VHF TV ch ch UHF TV ch ch MHz MHz MHz MHz MHz MHz MHz MHz MHz broadcast radio broadcast television broadcast radio Typical Use broadcast television broadcast television US ch. Notes not US OIRT Japan International US ch. phasing out reclaimed 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-28

29 Licensed Spectrum Selected Telephony Bands Allocation Frequency Band AMPS, IS-95, GSM MHz cdma2000, UMTS cdma2000, UMTS, W-CDMA GSM MHz MHz MHz Europe IS-95, GSM MHz Americas PCS LTE-A MHz MHz Americas Notes 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-29

30 Unlicensed spectrum Wireless Free Space Unlicensed Spectrum regulations for use (FCC Title 47 Part 18 and ) max transmit power (e.g. 1W) field strength spread spectrum parameters ISM: industrial, scientific, and medical 900 MHz, 2.4 GHz, 5.8 GHz, 24GHz UNII: unlicensed national information infrastructure 5.8 GHz may be use by anyone for any purpose (subject to regulations) problem? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-30

31 Unlicensed spectrum Wireless Free Space Unlicensed Spectrum regulations for use (FCC ) e.g. max transmit power e.g. spread spectrum parameters ISM: industrial, scientific, and medical 900 MHz, 2.4 GHz, 5.8 GHz, 24GHz UNII: unlicensed national information infrastructure 5.8 GHz may be use by anyone for any purpose (subject to regulations) interference a significant problem e.g. 2.4 GHz FHSS cordless phones against b e.g. interference among hubs in dense environments 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-31

32 Unlicensed Spectrum ISM Bands Band Center & BW Freq Typical Use 7 MHz 6.78 ± 0.15 MHz 13 MHz ± MHz 27 MHz ± MHz 40 MHz ± MHz 433 MHz 900 MHz 2.4 GHz 5.8 GHz 24 GHz 61 GHz ± 0.87 MHz ± MHz ± GHz ± GHz ± GHz ± GHz cordless phones, WLANs (historic) cordless phones, WLANs, WPANs cordless phones, WLANs (limited use) Microwave mesh link ad, millimeter-wave links 122 GHz 245 GHz ± GHz ± GHz future future Europe Notes 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-32

33 Wireless Spectrum Allocation Process ITU allocates and regulates international spectrum problem? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-33

34 Wireless Spectrum Allocation Process ITU allocates and regulates international spectrum competing national interests agreement can be difficult compromises are frequently poor solutions 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-34

35 Wireless Spectrum Allocation Process ITU allocates and regulates international spectrum Government agencies allocate and regulate spectrum problem? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-35

36 Wireless Spectrum Allocation Process ITU allocates and regulates international spectrum Government agencies allocate and regulate spectrum competing business, consumer, and government interests agreement can be difficult compromises are frequently poor solutions 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-36

37 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges exclusive use : spectrum within defined area government, military, public safety, public interest 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-37

38 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges exclusive use government, military, public safety, public interest command-and-control : license assignment comparative bidding process: broadcasters and service providers submit proposals problem? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-38

39 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges exclusive use government, military, public safety, public interest command-and-control comparative bidding process: broadcasters and service providers submit proposals problem: fairness (real and perception) and appeals 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-39

40 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges exclusive use government, military, public safety, public interest command-and-control comparative bidding lottery process: assignees picked by lottery problem? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-40

41 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges exclusive use government, military, public safety, public interest command-and-control comparative bidding lottery process: assignees picked by lottery problem: companies bid with intent to resell spectrum 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-41

42 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges exclusive use government, military, public safety, public interest command-and-control comparative bidding lottery auction process: competitive auction for spectrum problem? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-42

43 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges exclusive use government, military, public safety, public interest command-and-control comparative bidding lottery auction process: competitive auction for spectrum problem: complex process free market but antitrust issues 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-43

44 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges exclusive use government, military, public safety, public interest command-and-control comparative bidding lottery auction commons : unlicensed (including ISM) process: anyone can use subject to regulation problem? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-44

45 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges exclusive use government, military, public safety, public interest command-and-control comparative bidding lottery auction commons process: anyone can use subject to regulation problem: interference among applications (e.g. WLANs, cordless phones, µwave ovens among providers and users of given application (e.g. WLANs) 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-45

46 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges problem? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-46

47 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges problem: very inefficient use of spectrum why? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-47

48 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges problem: very inefficient use of spectrum spectrum reserved for future use difficult to reclaim unused spectrum example: UHF TV reclaimed for GSM in 850MHz inability to load balance among different allocations 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-48

49 Wireless Spectrum FCC/NTIA Spectrum Allocation FCC allocates and licenses spectrum in US [ static allocations lead to significant inefficiency in use 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-49

50 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges problem: very inefficient use of spectrum spectrum reserved for future use difficult to reclaim unused spectrum example: UHF TV reclaimed for GSM in 850MHz inability to load balance among different allocations alternative? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-50

51 Wireless Spectrum Allocation Process Spectrum allocated in fixed frequency ranges problem: very inefficient use of spectrum spectrum reserved for future use difficult to reclaim unused spectrum example: UHF TV reclaimed for GSM in 850MHz inability to load balance among different allocations alternative: dynamic spectrum allocation significant technical, political, and policy challenges fear of making things worse currently hot topic for research technical and policy 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-51

52 Wireless Spectrum Dynamic Allocation FCC Spectrum Policy Task Force recommendation command-and-control should only be used when needed: to accomplish important public interest objectives conform to treaty obligations significant expansion of commons allocation Dynamic spectrum management SDR (software defined radios) a key technology new algorithms and protocols significant policy change 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-52

53 Mobile Wireless Networking PL.2 Wireless Channels and Propagation PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.2.1 Digital and analog signals PL.2.2 Wireless propagation PL.2.3 Channel characteristics and challenges PL.3 Modulation, coding, and error control PL.4 Mobile wireless environment 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-53

54 Mobile Wireless Networking PL.2.1 Digital and Analog Signals PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.2.1 Digital and analog signals PL.2.2 Wireless propagation PL.2.3 Channel characteristics and challenges PL.3 Modulation, coding, and error control PL.4 Mobile wireless environment 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-54

55 Communication Signal Types Transmission of a signal through a medium 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-55

56 Communication Signal Types Transmission of a signal through a medium Analog signal: time-varying levels electromagnetic wave amplitude electrical: voltage levels photonic: light intensity 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-56

57 Communication Signal Types Transmission of a signal through a medium Analog signal: time-varying levels electrical: voltage levels photonic: light intensity Digital signal: sequence of bits represented as levels electrical: voltage pulses photonic: light pulses two levels for binary digital signal more levels in some coding schemes more later 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-57

58 Communication Digital vs. Analog Digital bits are reconstructed at the receiver 1 0 time 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-58 [Tannenbaum]

59 Communication Digital vs. Analog Digital bits are reconstructed at the receiver all transmission is actually analog! frequency response determines pulse rate that can be transmitted shape of pulse ability for receiver to recognise pulse 1 0 time 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-59 [Tannenbaum]

60 1 Communication Digital vs. Analog Digital bits are reconstructed at the receiver all transmission is actually analog! frequency response determines pulse rate that can be transmitted shape of pulse ability for receiver to recognise pulse high-frequency attenuation reduces quality of pulse adapted from [Tanenbaum 2003] 0 1 time harmonic attenuated frequencies 0 time harmonic 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-60 [Tannenbaum]

61 Communication Digital vs. Analog in Free Space Digital transmission is baseband frequency spectrum begins at 0Hz only practical for dedicated (guided media) wire and fiber optic cable Free space transmission generally broadband digital information modulated over a range of frequencies 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-61 [Tannenbaum]

62 Mobile Wireless Networking PL.2.1 Wireless Propagation PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.2.1 Digital and analog signals PL.2.2 Wireless propagation PL.2.3 Channel characteristics and challenges PL.3 Modulation, coding, and error control PL.4 Mobile wireless environment 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-62

63 Dedicated Wireless Free Space Medium Sharing single transmitter attached to medium signals may be multiplexed by a single transmitter link multiplexing 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-63

64 Dedicated Wireless Free Space Medium Sharing single transmitter attached to medium signals may be multiplexed by a single transmitter link multiplexing Shared: multiple access multiple transmitters transmit into a the same medium Lecture ML 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-64

65 Wireless Free Space Propagation Mechanisms WN Direct signal Reflection Diffraction Scattering 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-65

66 Wireless Free Space Propagation Mechanisms: Direct WN Direct signal direct transmission from transmitter to receiver Reflection Diffraction Scattering 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-66

67 Wireless Free Space Propagation Mechanisms: Reflection WN Direct signal Reflection reflected off object large relative to wavelength Diffraction Scattering 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-67

68 Wireless Free Space Propagation Mechanisms: Diffraction WN Direct signal Reflection Diffraction bending by object comparable to wavelength Scattering 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-68

69 Wireless Free Space Propagation Mechanisms: Scattering WN Direct signal Reflection Diffraction Scattering by many objects smaller than wavelength multiple weaker signals 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-69

70 Wireless Free Space Propagation Mechanisms: Multipath WN Multipath multiple signals using different propagation mechanisms problem? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-70

71 Wireless Free Space Propagation Mechanisms: Multipath Multipath interference or distortion multiple signals using different propagation mechanisms time-shifted versions of signal interfere with one another WN 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-71

72 Wireless Free Space Antennæ and Transmission Pattern Omnidirectional antennæ RF radiated in all directions advantages and disadvantages? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-72

73 Wireless Free Space Antennæ and Transmission Pattern Omnidirectional antennæ RF radiated in all directions advantage: simple cheap design 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-73

74 Wireless Free Space Antennæ and Transmission Pattern Omnidirectional antennæ RF radiated in all directions advantage: simple cheap design disadvantage: no spatial reuse 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-74

75 Wireless Free Space Antennæ and Transmission Pattern Omnidirectional antennæ Directional antennæ focused beam of radiation advantages and disadvantages? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-75

76 Wireless Free Space Antennæ and Transmission Pattern Omnidirectional antennæ Directional antennæ focused beam of radiation advantage reduces contention with spatial reuse 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-76

77 Wireless Free Space Antennæ and Transmission Pattern Omnidirectional antennæ Directional antennæ focused beam of radiation advantage reduces contention with spatial reuse disadvantages more complex antenna design significantly complicates network design: beam steering MAC Lecture ML 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-77

78 Wireless Free Space Propagation Modes ionosphere Ground-wave propagation Sky wave propagation Line-of-sight propagation < 2 MHz 2 30 MHz > 30 MHz 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-78

79 Wireless Free Space Propagation Modes: Ground Wave ionosphere Ground-wave propagation signals follow curvature of earth scattered in upper atmosphere Sky wave propagation Line-of-sight propagation < 2 MHz 2 30 MHz > 30 MHz 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-79

80 Wireless Free Space Propagation Modes: Sky Wave ionosphere Ground-wave propagation < 2 MHz Sky wave propagation 2 30 MHz signals refracted off ionosphere communication possible over thousands of kilometers Line-of-sight propagation > 30 MHz 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-80

81 Wireless Free Space Propagation Modes: Line of Sight ionosphere Ground-wave propagation < 2 MHz Sky wave propagation 2 30 MHz Line-of-sight propagation > 30 MHz antennæ must be in view of one-another terrain and earth curvature block signature 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-81

82 Wireless Free Space Spectrum Table Band Range Propagation Usage Examples Name Description Frequencies Wavelength Sight ELF VF VLF LF MF HF VHF UHF SHF EHF IR ext. low Hz 10 1Mm GW home automation voice Hz km GW voice tel., modem very low 3 30kHz km GW atmos. noise submarine low kHz 10 1km GW daytime maritime medium kHz m GW daytime maritime, AM radio high 3 30MHz m SW daytime transportation very high MHz 10 1 m LOS temp, cosmic television, FM radio ultra high MHz mm LOS cosmic noise television, cell tel. super high 3 30GHz mm LOS O 2, H 2 O wireless comm. ext. high GHz 10 1mm LOS O 2, H 2 O vapor wireless comm. infrared 300GHz 400THz nm LOS optical comm. visible visible THz nm 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-82 LOS Attenuation

83 Velocity v = c /n [m/s] Wireless Free Space Velocity speed of light c = km/s index of refraction n Consequences? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-83

84 Velocity v = c /n [m/s] Wireless Free Space Velocity and Delay speed of light c = km/s index of refraction n this is why velocity slower than c in fiber and wire Delay d = 1/v [s/m] generally we will express delay in [s] given a path length 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-84

85 Mobile Wireless Networking PL.2.3 Channel Characteristics and Challenges PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.2.1 Digital and analog signals PL.2.2 Wireless propagation PL.2.3 Channel characteristics and challenges PL.3 Modulation, coding, and error control PL.4 Mobile wireless environment 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-85

86 Wireless Channel Characteristics and Challenges Goal for communications link receiver reconstructs signal transmitter sent propagation (PL.2.2) Challenges to meeting this goal path loss and attenuation fading noise and interference Doppler Shift transmission rate constraints 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-86

87 Wireless Channel Challenges Path Loss and Attenuation Path loss and attenuation Fading Noise and interference Doppler Shift Transmission rate constraints 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-87

88 Link Length Path Loss and Attenuation Transmission Length distance over which signals propagate constrained by physical properties of medium Consequences? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-88

89 Path Loss and Attenuation Transmission Length Attenuation: decrease in signal intensity over distance expressed as [db/m] at a particular signal frequency how to compute? db db m m 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-89

90 Attenuation Path Loss and Attenuation Transmission Length signal strength decreases as 1/r 2 in perfect medium why? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-90

91 Attenuation Path Loss and Attenuation Transmission Length signal strength decreases as 1/r 2 in perfect medium signal may decrease as 1/r x with multipath interference rural environments: x > 2 urban environments: x 4 more later 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-91

92 Path Loss and Attenuation Frequency Response Attenuation: decrease in signal intensity over distance expressed as [db/m] at a particular signal frequency Frequency response of media wire: generally falls off above a certain f max fiber optic cable & free space transparent to certain ranges analogy: UV blocking sunglasses (high attenuation ) vs. standard glass (moderate attenuation ) vs. UV transparent black light glass (low attenuation ) 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-92

93 Path Loss and Attenuation Spectrum Table: Frequency Response Band Range Propagation Usage Examples Name Description Frequencies Wavelength Sight ELF VF VLF LF MF HF VHF UHF SHF EHF IR ext. low Hz 10 1Mm GW home automation voice Hz km GW voice tel., modem very low 3 30kHz km GW atmos. noise submarine low kHz 10 1km GW daytime maritime medium kHz m GW daytime maritime, AM radio high 3 30MHz m SW daytime transportation very high MHz 10 1 m LOS temp, cosmic television, FM radio ultra high MHz mm LOS cosmic noise television, cell tel. super high 3 30GHz mm LOS O 2, H 2 O wireless comm. ext. high GHz 10 1mm LOS O 2, H 2 O vapor wireless comm. infrared 300GHz 400THz nm LOS optical comm. visible visible THz nm 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-93 LOS Attenuation

94 Path Loss and Attenuation Frequency Response Atmospheric transparency bands RF: 10MHz 10GHz VHF meter band, UHF millimeter band Atmospheric Opacity Infrared: N-band adapted from [coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/irwindows.html] IR microwave 0.1nm 1nm 10nm 100nm 1µm 10µm 100µm 1mm 1cm 10cm 1m 10m 100m 1km 1EHz 100PHz 10Pz 1PHz 100THz 10THz 1THz 100GHz 10GHz 1GHz 100MHz 10MHz 1MHz 100KHz Wavelength [m] Frequency [Hz] 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-94 RF shortwave UHF VHF

95 Wireless Channel Challenges Fading Path loss and attenuation Fading Noise and interference Doppler Shift Transmission rate constraints 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-95

96 Channel fading Wireless Channel Fading Definition changes of signal intensity over time 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-96

97 Channel fading Wireless Channel Fading Types and Cause changes of signal intensity over time Fast fading rapid fluctuations in intensity mobility on the order of 1/2 wavelength 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-97

98 Channel fading Wireless Channel Fading Types and Cause changes of signal intensity over time Fast fading rapid fluctuations in intensity mobility on the order of 1/2 wavelength Slow fading long-term fluctuations in intensity (seconds to minutes) causes? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-98

99 Channel fading Wireless Channel Fading Types and Cause changes of signal intensity over time Fast fading rapid fluctuations in intensity mobility on the order of 1/2 wavelength Slow fading long-term fluctuations in intensity (seconds to minutes) causes obstructions such as rain (rain fade ) micro-mobility among buildings in urban areas macro-mobility between base stations 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-99

100 Channel fading Wireless Channel Fading Types and Cause changes of signal intensity over time Flat fading (nonselective) uniform fade across frequency range Selective fading different frequency components suffer different attenuation 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-100

101 Wireless Channel Challenges Interference Path loss and attenuation Fading Noise and interference Doppler Shift Transmission rate constraints 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-101

102 Noise and Interference Definition Superposition interaction of waves is interference Causes? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-102

103 Noise and Interference Causes Superposition interaction of waves is interference Causes noise co-channel interference adjacent channel interference 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-103

104 Noise Causes Noise interferes with signals Thermal noise [W/Hz] caused by agitation of electrons: function of temperature t independent of frequency: white noise N = ktb ; k = [J/K] (Boltzmann constant) B = bandwidth [Hz] 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-104

105 Noise Cause and Effect: SNR Noise interferes with signals Thermal noise [W/Hz] = [(J/s)/s 1 ] = [J] caused by agitation of electrons: function of temperature t independent of frequency: white noise N = ktb ; k = [J/K] (Boltzmann constant) B = bandwidth [Hz] Background noise N o thermal noise + other sources (e.g. cosmic radiation) N o interferes with the signal bit energy E b SNR: signal to noise ratio = 10 log 10 (E b /N o ) [db] (decibels) 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-105

106 Interference Co-Channel Interference Co-channel interference within given frequency band Causes and solutions? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-106

107 Interference Co-Channel Interference Co-channel interference within given frequency band Multiple users sharing channel motivates medium access control (MAC) Lecture ML 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-107

108 Interference Co-Channel Interference Co-channel interference within given frequency band Multiple users sharing channel motivates medium access control (MAC) Lecture ML Malicious attack: jamming of channel faraday cage to repel spread spectrum techniques Lecture ML resilience techniques EECS August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-108

109 Interference Co-Channel Interference Co-channel interference within given frequency band Multiple users sharing channel motivates medium access control (MAC) Lecture ML Malicious attack: jamming of channel Faraday cage to isolate when possible spread spectrum techniques Lecture ML resilience techniques EECS 983 Natural phenomena e.g. sunspots 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-109

110 Interference Adjacent Channel Interference Adjacent channel interference between freq. bands Solutions? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-110

111 Interference Co-Channel Interference Adjacent channel interference between freq. bands Guard bands reserved bandwidth between frequency bands 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-111

112 Interference Adjacent Channel Interference Adjacent channel interference between freq. bands Spatial partitioning adjacent channels not used in same geographic area e.g. TV broadcast channels (2,4,5,7,9,11,13 vs. 3,6,8,10,12) e.g. FM broadcast stations e.g. cellular frequency plan for mobile telephony 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-112

113 Interference Adjacent Channel Partitioning: Broadcast TV GOTHAM Ch. 2,4,5,7,9,11,13 Elk s Breath Ch. 6 Mayberry Ch. 3,8 Smallville Ch. 10, 12 METROPOLIS Ch. 2,4,5,11 Spatial partitioning example: broadcast television large cities get channels 2,4,5,7,9,11,13 recall guard band between 4/5 and 6/7 small towns in-between get channels 3,6,8,10,12 Spatial partitioning example: broadcast FM radio adjacent frequencies not used in same city 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-113

114 Interference Adjacent Channel Partitioning: Cellular cell Spatial partitioning example: cellular telephony most efficient circular packing is hexagonal frequency channels mapped to hexagonal tiling adjacent cells assigned different frequencies Lecture MT 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-114

115 Wireless Channel Challenges Doppler Shift Path loss and attenuation Fading Noise and interference Doppler Shift Transmission rate constraints 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-115

116 Doppler shift Doppler Shift Definition explained by Austrian scientist Christian Doppler in 1800s what is it? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-116

117 Doppler shift Doppler Shift Definition explained by Austrian scientist Christian Doppler in 1800s wavelength changes with relative velocity recall decreasing pitch of horn as train passes Doppler effect f d = v/λ Consequences? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-117

118 Doppler shift Doppler Shift Consequences explained by Austrian scientist Christian Doppler in 1800s wavelength changes with relative velocity recall decreasing pitch of horn as train passes Doppler effect f d = v/λ Consequences frequency perceived by receiver different from expected concern networks with high node mobility 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-118

119 Wireless Channel Challenges Transmission Rate Constraints Path loss and attenuation Fading Propagation modes and interference Doppler Shift Transmission rate constraints 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-119

120 Transmission Rate Constraints Overview Transmission rate constraints transceiver switching frequency Nyquist rate Shannon rate 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-120

121 Transmission Rate Constraints Switching Frequency Rate constrained by switching frequency transmitter and receiver [b/s] dictated by electronic circuits switching time of transistors propagation delay through circuits 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-121

122 Transmission Rate Constraints Nyquist Rate Channel capacity C [b/s] Harry Nyquist: Swedish physicist at Bell Labs in early 1900s determined by bandwidth (max CS bandwidth determined by EE bandwidth) constrained by number of quantization levels per bit C = 2B log 2 L B = channel bandwidth [Hz] = [1/s] L = number of quantization levels 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-122

123 Transmission Rate Constraints Shannon Theorem Maximum data rate for noisy channel Claude Shannon: American at Bell Labs in mid-1900s father of information theory and pioneer in digital logic noise reduces data rate C = B log 2 (1+ S/N )) C = channel capacity [b/s] B = channel bandwidth [Hz] = [1/s] S = signal power [db] N = noise power [db] 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-123

124 Mobile Wireless Networking PL.3 Modulation, Coding, and Error Control PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.3 Modulation, coding, and error control PL.3.1 Modulation and coding PL.3.2 Error control PL.4 Mobile wireless environment 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-124

125 Mobile Wireless Networking PL.3.1 Modulation and Coding PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.3 Modulation, coding, and error control PL.3.1 Modulation and coding PL.3.2 Error control PL.4 Mobile wireless environment 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-125

126 Modulation and Coding Digital Communication Digital Communication we consider only digital communication for networking transmission of binary data (bits) through a channel recall: in free space digital signal is analog modulated broadband, not baseband 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-126

127 Line coding Modulation and Coding Line Coding way in which bits are encoded for transmission digital codes (binary, trinary, ) analog modulation 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-127

128 Line coding Modulation and Coding Line Coding and Symbol Rate way in which bits are encoded for transmission digital codes (binary, trinary, ) EECS 780 analog modulation Symbol rate baud rate [symbols/s] baud = b/s only if one symbol/bit clever encodings (e.g. QAM) allow high baud rates 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-128

129 Analog Line Coding Analog Modulation Analog line coding modulate an analog carrier with a digital signal August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-129

130 Analog line coding Analog Line Coding Amplitude Modulation modulate an analog carrier Amplitude modulation each symbol a different level of carrier one may be zero voltage compare to AM radio modulate an analog carrier with an analog signal August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-130

131 Analog Line Coding Frequency Modulation Analog line coding modulate a carrier Amplitude modulation each symbol a different level Frequency modulation each symbol a different frequency FSK (frequency shift keying) compare to FM radio modulate an analog carrier with an analog signal August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-131

132 Analog Line Coding Phase Modulation Analog line coding modulate a carrier Amplitude modulation each symbol a different level Frequency modulation each symbol a different frequency Phase modulation each symbol a different phase e.g. 0, August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-132

133 Analog Line Coding Combination Codes Analog line coding: modulate a carrier Amplitude modulation each symbol a different level Frequency modulation each symbol a different frequency Phase modulation each symbol a different phase Combinations possible why? August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-133

134 Analog Line Coding Combination Codes Analog line coding: modulate a carrier Amplitude modulation each symbol a different level Frequency modulation each symbol a different frequency Phase modulation each symbol a different phase Combinations possible e.g. amplitude and phase August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-134

135 Analog Line Coding QPSK and QAM Combination of amplitude- and phase-modulation allows more bits per symbol QAM: quadrature amplitude modulation quadrature = 4 phases carried on two sine waves PAM is case for only one phase QPSK is case for only one amplitude Name Amplitudes Phases Bits/Symbol QPSK QAM QAM QAM August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-135

136 Analog Line Coding QPSK and QAM QAM: amplitude- and phase modulation Represented by constellation diagram amplitude is distance from origin phase is angle QPSK 90 QAM QAM August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-136

137 Mobile Wireless Networking PL.3.2 Error Control PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.3 Modulation, coding, and error control PL.3.1 Modulation and coding PL.3.2 Error control PL.4 Mobile wireless environment 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-137

138 Error Control Introduction and Motivation Motivation for error control? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-138

139 Error Control Introduction and Motivation Motivation for error control channels are imperfect cause: noise and interference result: bit errors components can fail packets my be dropped due to congestion EECS 780 Therefore need error control where to perform? physical layer? link layer? transport layer? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-139

140 Error Control Hop-by-Hop vs. End-to-End Per-hop error control for frame transfers Why? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-140

141 Error Control Hop-by-Hop vs. End-to-End Per-hop error control for frame transfers Recall end-to-end arguments: if error checking and correction needed E2E it must be done end-to-end by transport (or application) Hop-by-hop control to improve overall performance physical layer for bit errors in noisy channel link layer at frame granularity Lecture ML 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-141

142 Error Control Detection Techniques Byte, word, or (small) block: done at physical layer parity 2-dimensional parity Hamming codes Frame: done at link layer Lecture ML checksum CRC 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-142

143 Block Error Detection Parity Parity: detect single errors no ability to correct errors only an odd number of bit errors detected only useful if bit error probability very low 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-143

144 Block Error Detection Parity Parity: detect single errors no ability to correct errors only an odd number of bit errors detected only useful if bit error probability very low Parity bit covers n bit block Even parity: even number of 1s (including parity) example: ? Odd parity odd number of 1s (including parity) example: ? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-144

145 Block Error Detection Parity Parity: detect single errors no ability to correct errors only an odd number of bit errors detected only useful if bit error probability very low Parity bit covers n bit block Even parity: even number of 1s (including parity) example: Odd parity odd number of 1s (including parity) example: August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-145

146 Block Error Detection & Correction 2-Dimensional Parity 2-dimensional parity: correct single bit errors detects which bit flipped and can therefore correct 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-146

147 Block Error Detection & Correction 2-Dimensional Parity 2-dimensional parity: correct single bit errors detects which bit flipped and can therefore correct n + m parity bits covers n m bit block n row parity bits cover m data bits each m column parity bits cover n data bits each 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-147

148 Block Error Detection & Correction 2-Dimensional Parity 2-dimensional parity: correct single bit errors detects which bit flipped and can therefore correct n + m parity bits covers n m bit block n row parity bits cover m data bits each m column parity bits cover n data bits each Example (odd parity) August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-148

149 Block Error Detection & Correction 2-Dimensional Parity 2-dimensional parity: correct single bit errors detects which bit flipped and can therefore correct n + m parity bits covers n m bit block n row parity bits cover m data bits each m column parity bits cover n data bits each Example (odd parity) detects and can correct flip August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-149

150 Block Error Detection & Correction Hamming Codes Hamming codes: correct single bit errors detects which bit flipped and can therefore correct k parity bits per block cover different sets of n data bits 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-150

151 Block Error Detection & Correction Hamming Codes Hamming codes: correct single bit errors detects which bit flipped and can therefore correct k parity bits per block cover different sets of n data bits SECDED: single error correct double error detect 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-151

152 Block Error Detection & Correction Hamming Codes Hamming codes: correct single bit errors detects which bit flipped and can therefore correct k parity bits per block cover different sets of n data bits SECDED: single error correct double error detect Example 4 data bits covered by 3 parity bits parity bits p 2 p 1 p 0 interleaved with data bits d 3 d 2 d 1 d d 3 d 2 d 1 p 2 d 0 p 1 p d 3 d 1 d 0 covered by p d 3 d 2 d 0 covered by p d 3 d 2 d 1 covered by p 2 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-152

153 Block Error Detection & Correction Hamming Codes Hamming codes: correct single bit errors detects which bit flipped and can therefore correct k parity bits per block cover different sets of n data bits SECDED: single error correct double error detect Example 4 data bits covered by 3 parity bits parity bits p 2 p 1 p 0 interleaved with data bits d 3 d 2 d 1 d d 3 d 2 d 1 p 2 d 0 p 1 p d 3 d 1 d 0 covered by p d 3 d 2 d 0 covered by p p 1 detects error 1011 d 3 d 2 d 1 covered by p p 2 detects error 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-153

154 Error Detection & Correction Forward Error Correction Forward error correction (FEC) redundant information added to data allows detection of errors also allows correction of errors 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-154

155 Error Detection & Correction Forward Error Correction Forward error correction (FEC) redundant information added to data allows detection of errors also allows correction of errors Types of FEC codes block codes: FEC header over link layer frame Lecture ML convolutional code: redundant bits interspersed in stream turbo codes: iterative convolutional coder performs closer to theoretical Shannon limit EECS August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-155

156 Forward Error Correction Convolutional Coder Convolutional code redundant bits interspersed in stream 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-156

157 Mobile Wireless Networking PL.4 Mobile Wireless Environment PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.3 Modulation, coding, and error control PL.4 Mobile wireless environment PL.4.1 Network impact of wireless channel PL.4.2 Network impact of mobility 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-157

158 Mobile Wireless Environment Impact on the Network Recap: brief introduction to physical layer Why does this matter to the network? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-158

159 Mobile Wireless Environment Impact on the Network Recap: brief introduction to physical layer Network consists of nodes interconnected by links characteristics of links and nodes impact network 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-159

160 Mobile Wireless Environment Impact on the Network Recap: brief introduction to physical layer Network consists of nodes interconnected by links characteristics of links and nodes impact network Traditional PSTN and Internet static (non-mobile) nodes reliable wired links many design decisions based on these assumptions What is different and why does it matter? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-160

161 Mobile Wireless Environment PL.4.1 Network Impact of Wireless Channel PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.3 Modulation, coding, and error control PL.4 Mobile wireless environment PL.4.1 Network impact of wireless channel PL.4.2 Network impact of mobility 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-161

162 Impact of Wireless Channel Channel Connectivity Impact of wireless channel on connectivity? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-162

163 Wireless Channel Channel Connectivity Weak time-varying connectivity limited bandwidth of shared medium time-varying channel capacity noise interference fading 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-163

164 Wireless Channel Channel Connectivity Weak time-varying connectivity Intermittent and episodic connectivity long fades (e.g. rain fades) interference and jamming 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-164

165 Wireless Channel Channel Connectivity Weak time-varying connectivity Intermittent and episodic connectivity Asymmetric connectivity due to heterogeneous nodes unequal transmitter power design available power over battery life different up/downlink characteristics mobile phones satellite links 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-165

166 Wireless Channel Impact of Weak Connectivity Traditional networks strong symmetric connectivity assumed weak connectivity treated as failure 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-166

167 Wireless Channel Impact of Weak Connectivity Traditional networks strong symmetric connectivity assumed weak connectivity treated as failure Impact of weak connectivity? 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-167

168 Wireless Channel Impact of Weak Connectivity Traditional networks strong symmetric connectivity assumed weak connectivity treated as failure Impact of weak connectivity bit errors packet loss performance impact link failures routing reconvergence loss discrimination important Lecture WI 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-168

169 Wireless Channel Impact of Weak Connectivity Traditional networks strong symmetric connectivity assumed weak connectivity treated as failure Impact of weak connectivity bit errors packet loss performance impact link failures routing reconvergence loss discrimination important Lecture WI Mobile wireless networks weak, asymmetric, intermittent, episodic connectivity routine network architecture and protocol design for this 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-169

170 Example Weak Connectivity Scenario WDTN Millimeter-Wave Mesh Network Millimeter-wave links GHz, 1 10 Gb/s severe rain attenuation Mesh architecture high degree of connectivity alternate diverse paths WDTN solution reroute before failures occur avoid high error links P-WARP, XL-OSPF CO/POP [Jabbar Rohrer Oberthaler Çetinkaya Frost Sterbenz 2009] G 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-170

171 Open channel problems? Wireless Channel Open Channel 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-171

172 Wireless Channel Open Channel Open channel subject to attack eavesdropping network and traffic analysis interference jamming and denial of service injection of bogus signalling and control messages 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-172

173 Wireless Channel Impact of Open Channel Open channel subject to attack eavesdropping network and traffic analysis interference jamming and denial of service injection of bogus signalling and control messages Security and resilience more important Lecture RS ECS August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-173

174 Mobile Wireless Environment PL.4.2 Network Impact of Mobility PL.1 Physical media and spectrum PL.2 Wireless channels and propagation PL.3 Modulation, coding, and error control PL.4 Mobile wireless environment PL.4.1 Network impact of wireless channel PL.4.2 Network impact of mobility 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-174

175 Impact of mobility? Impact of Mobility Overview 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-175

176 Impact of mobility connectivity dynamic topologies QoS Impact of Mobility Overview 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-176

177 Impact of Mobility Connectivity Mobility impacts connectivity nodes move in and out of range of one another long fades episodic and intermittent connectivity Design for weak connectivity as for wireless channel impacts 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-177

178 Impact of Mobility Dynamic Topologies Mobility means nodes and subnets move result: dynamic topology changing links, clustering, and federation topology difficult to achieve routing convergence mobility may exceed ability of control loops to react 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-178

179 Impact of Mobility Dynamic Topologies Mobility means nodes and subnets move result: dynamic topology changing links, clustering, and federation topology difficult to achieve routing convergence mobility may exceed ability of control loops to react Design for mobility addressing mechanisms must not assume static location routing algorithms must assume dynamic topologies predictive reactive 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-179

180 Impact of Mobility Quality of Service Mobility impacts QoS (quality of service) 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-180 1

181 Impact of Mobility Quality of Service Mobility impacts QoS (quality of service) changes in inter-node distance requires power adaptation changes node density and impacts degree of connectivity latency issues (routing optimisations temporary) 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-181 2

182 Impact of Mobility Quality of Service Mobility impacts QoS (quality of service) changes in inter-node distance requires power adaptation changes node density and impacts degree of connectivity latency issues (routing optimisations temporary) 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-182 3

183 Example High-Mobility Scenario Airborne Ad Hoc Networking Very high relative velocity Mach 7 10 s contact dynamic topology Communication channel limited spectrum asymmetric links data down omni C&C up directional Multihop among TAs, through RNs [Rohrer Jabbar Perrins Sterbenz 2008] 22 August 2011 KU EECS 882 Mobile Wireless Nets Phy. Layer & Env. MWN-MW-183 GS GW TA RN TAs TA test article relay node Internet TA RN GS GW GS ground station GW gateway