Mobile Wireless Networking The University of Kansas EECS 882 Wireless Sensor Networks

Mobile Wireless Networking The University of Kansas EECS 882 Wireless Sensor Networks James P.G. Sterbenz Department of Electrical Engineering & Computer Science Information Technology & Telecommunications Research Center The University of Kansas jpgs@eecs.ku.edu http://www.ittc.ku.edu/~jpgs/courses/mwnets 28 November 2011 rev. 11.0 2004 2011 James P.G. Sterbenz

Mobile Wireless Networking Wireless Sensor Networks SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.4 Sensor network routing 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-2

Mobile Wireless Networking Sensor Network Introduction Wireless Sensor Networks specialised subset of mobile wireless networks still a fairly hot topic of research very few standards other than 802.15.4 and ZigBee enough material for an entire course! e.g. [KW2005] This EECS 882 lecture brief overview to the discipline emphasise differences from other mobile wireless nets and their implications to architecture and design introduction to 802.15.4 and ZigBee standards 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-3

Wireless Sensor Networks SN.1 Sensor and Actuator Network Overview SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.4 Sensor network routing 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-4

Sensor and Actuator Networks Motivation: Control Systems The world is full of control systems sensors provide inputs on the state of the system control algorithm processes based on parameters actuators control the system parameters control algorithm (processing) sensor actuator 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-5

Sensor and Actuator Networks Motivation: Distributed Control Systems The world is full of control systems sensors provide inputs on the state of the system control algorithm processes based on parameters actuators control the system Distributed control systems? parameters control algorithm (processing) sensor actuator 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-6

Sensor and Actuator Networks Motivation: Distributed Control Systems Distributed control systems need networks connecting elements sensor and actuator networks these are frequently wireless generally called WSNs wireless sensor networks actuators left out for brevity but sometimes WSANs parameters sensors control algorithm (processing) actuator 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-7

WSN Architecture Components Sensor device that senses information from environment Actuator Sink device that controls environment destination of sensor data for processing or storage Gateway interworking between WSN and data network typically the Internet S note: no standard symbols for WSN components (IEC control systems symbols not really appropriate) 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-8

WSN Characteristics Introduction Defining characteristics of WSNs? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-9

WSN Characteristics Introduction Defining characteristics of WSNs wireless nodes energy efficiency critical difficult or impossible to replace battery large scale sensor fields may have thousand or millions of nodes ad hoc: manual configuration impractical frequently nodes have low duty cycle e.g. periodic temperature reports 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-10

WSN Characteristics Introduction Defining characteristics of WSNs wireless nodes energy efficiency critical large scale Important note: not all sensors/actuators are wireless nor energy constrained we will concentrate on those that are heterogeneous wired/wireless sensor networks have additional challenges SNs have additional interesting properties wired nodes can be exploited to assist wireless 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-11

WPAN: Sensor Network Characteristics Differences from WPANs and MANETs MANET: Differences? wireless personal network mobile ad hoc network 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-12

WPAN: Sensor Network Characteristics Differences from WPANs and MANETs MANET: Energy concerns? wireless personal network mobile ad hoc network 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-13

Sensor Network Characteristics Differences from WPANs and MANETs Energy concerns WPAN and MANET nodes batteries generally rechargeable or replaceable WSN energy management more critical batteries generally assumed not replicable low duty cycle of sensors helps Limited mobility many sensors are stationary initial self-organisation more important dynamic reöptimisation less critical network must react to failed nodes that have no energy left 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-15

Sensor Network Characteristics Differences from SCADA Networks SCADA: supervisory control and data acquisition SCADA networks control industrial processes and utilities e.g. power grid, nuclear power plant, chemical plants Differences? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-16

Sensor Network Characteristics Differences from SCADA Networks SCADA: supervisory control and data acquisition SCADA networks control industrial processes and utilities Links e.g. power grid, nuclear power plant, chemical plants SCADA nodes traditionally wired within plant area energy not a concern wireless remote sensors/actuators becoming more common Scale frequently for convenience rather than lack of power source SCADA network scale generally thought of as smaller 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-17

Sensor Network Characteristics Differences from other Networks WSNs are generally data centric information important not necessarily related to particular nodes Examples average temperature of a region mapping of a storm or wildfire location of an animal Consequence? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-18

Sensor Network Characteristics In-Network Processing WSNs frequently manipulate data in the network sensor nodes not only relay multihop traffic but also process it on the way More energy efficient processing generally cheaper then transmission Lecture EM e.g. nodes compute average, max, or min value significantly reduces communication cost referred to as sensor fusion or data fusion 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-20

Sensor Network Characteristics In-Network Processing Types Aggregation compute statistical functions on the way to the sink average, min, max, etc. Edge detection compute and convey boundaries between values e.g isotherms, isobars, storm edges, wildfire boundaries Trajectory tracking e.g. animal movement Other variants possible 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-21

Wireless Sensor Networks Application Examples Environmental monitoring long term, e.g. climate change short term, e.g. wildfire mapping Medical and health vital signs and ongoing biochemical monitoring automated drug dosing Intelligent buildings fine-grained monitoring and control of temperature Military and homeland security situational awareness Many more! 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-22

Wireless Sensor Networks SN.2 Sensor Network Architecture & Topology SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.4 Sensor network routing 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-23

Single hop Wireless Sensor Networks Alternative Architectures advantages and disadvantages? S 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-24

Wireless Sensor Networks Alternative Architectures Single hop simple architecture only appropriate for small WSNs distance and scale S 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-25

Wireless Sensor Networks Alternative Architectures Single hop simple architecture only appropriate for small WSNs distance and scale Multihop advantages and disadvantages? S 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-26

Wireless Sensor Networks Alternative Architectures Single hop simple architecture only appropriate for small WSNs Multihop distance and scale communication with limited transmission power may conserve energy but may not: energy use for transit traffic S 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-27

Wireless Sensor Networks Performance Metrics Conventional network metrics bandwidth, delay, etc. Energy-related metrics? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-28

Wireless Sensor Networks Performance Metrics Conventional network metrics bandwidth, delay, etc. Energy-related metrics energy/received-bit energy/event network lifetime: duration for network to remain operational time to first node failure half-life: time to 50% node failure time to partition etc. 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-29

Wireless Sensor Networks SN.3 Sensor Network HBH Communication SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.3.1 Transceivers and physical communication SN.3.2 Medium access control SN.3.3 Inter-sensor link functions SN.3.4 802.15.4 low energy PAN and ZigBee SN.4 Sensor network routing 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-30

Wireless Sensor Networks Node Role Comparison network type node types IS role ES role transfer types traditional ES xor IS only transit no transit HBH vs. E2E MANET ES or IS (dual role) gateway transit HBH vs. E2E WSN ES (sensor) and sink sink data fusion HBH E2E 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-31

Wireless Sensor Networks Hop-by-Hop Communication Hop-by-hop communication in sensor networks physical layer communication links medium access control link layer functions Different from traditional network L1 L3 mechanisms optimised for? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-33

Wireless Sensor Networks Hop-by-Hop Communication Hop-by-hop communication in sensor networks physical layer communication links medium access control link layer functions Different from traditional network L1 L3 mechanisms optimised for: low energy lower data rates frequently acceptable not optimised for? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-34

Wireless Sensor Networks Hop-by-Hop Communication Hop-by-hop communication in sensor networks physical layer communication links medium access control link layer functions Different from traditional network L1 L3 mechanisms optimised for: low energy lower data rates frequently acceptable not optimised for: bandwidth mobility (lower rates frequently acceptable) (many sensors stationary once deployed) 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-35

Sensor Network HBH Communication SN.3.1 Transceivers & Physical Communication SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.3.1 Transceivers and physical communication SN.3.2 Medium access control SN.3.3 Inter-sensor link functions SN.3.4 802.15.4 low energy WPAN and ZigBee SN.4 Sensor network routing 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-36

WSN HBH Communication Physical Layer Overview WSN physical layer issues similar to MANETs WPANs Coding goal generally not expensive coding for high bit rate goal generally is for efficient low energy transmission negligible spreading and multipath due to short range 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-37

WSN HBH Communication Transceiver Overview Transceivers use significant power transmission power transmit circuit power receiver circuit power How to manage? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-38

WSN HBH Communication Transceiver Overview Transceivers use significant power transmission power transmit circuit power receiver circuit power Power management: adaptive transmit power sleep when not transmitting sleep when not receiving problem? Lecture EM 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-39

WSN HBH Communication Transceiver Overview Transceivers use significant power transmission power transmit circuit power receiver circuit power Power management: adaptive transmit power sleep when not transmitting sleep when not receiving need wakeup mechanism may be OK to miss reception of some items of similar data 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-40

Sensor Network HBH Communication SN.3.2 Medium Access Control SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.3.1 Transceivers and physical communication SN.3.2 Medium access control SN.3.3 Inter-sensor link functions SN.3.4 802.15.4 low energy WPAN and ZigBee SN.4 Sensor network routing 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-41

WSN Medium Access Control Medium Access Control Issues WSN MAC: issues common with other wireless nets hidden and exposed nodes collisions in shared medium overhead and resource awareness What is different? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-42

WSN Medium Access Control Medium Access Control Issues WSN MAC: issues different from other wireless nets low duty cycle extreme energy management Problems? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-43

WSN Medium Access Control Medium Access Control Problems Sleeping receivers can t sense transmission schedule wakeups TDMA with synchronised clocks clustered, e.g. LEACH with rotating clusterheads S-MAC and T-MAC learn schedules from neighbours periodic wakeup with long preambles, e.g. B-MAC out-of-band wakeup 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-44

WSN Medium Access Control Medium Access Control Problems Low duty cycle increased need for wakeup mechanisms reduces the probability of collisions RTS/CTS not needed 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-45

Sensor Network HBH Communication SN.3.3 Inter-Sensor Links SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.3.1 Transceivers and physical communication SN.3.2 Medium access control SN.3.3 Inter-sensor link functions SN.3.4 802.15.4 low energy WPAN and ZigBee SN.4 Sensor network routing 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-46

Link layer functions multiplexing framing error control flow control Concerns? WSN Link Protocols Link Layer Functions 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-47

Link layer functions multiplexing framing error control flow control WSN Link Protocols Link Layer Concerns Wireless sensor network concerns energy conservation data-driven application reliability requirements 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-48

Link layer functions multiplexing framing error control flow control WSN Link Protocols Multiplexing Wireless sensor network concerns energy conservation data-driven application reliability requirements 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-49

WSN multiplexing WSN Link Protocols Multiplexing shared medium: handled by MAC algorithm 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-50

Link layer functions multiplexing framing error control flow control WSN Link Protocols Framing Wireless sensor network concerns energy conservation data-driven application reliability requirements 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-51

Link layer framing WSN Link Protocols Framing header and trailer encapsulation for HBH transmission link and MAC control information Issue? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-52

Link layer framing WSN Link Protocols Framing header and trailer encapsulation for HBH transmission link and MAC control information Issue: overhead in-band: encapsulation overhead per frame out-of-band: MAC overhead per frame Choice: frame size 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-53

Small frames WSN Link Protocols Framing: Small Frames higher header overhead: more xmit energy consumed lower packet error rate / BER lower ARQ energy isolates effects of independent bit errors to smaller chunks 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-54

Small frames WSN Link Protocols Framing: Large Frames higher header overhead: more xmit energy consumed lower packet error rate / BER less ARQ energy consumed isolates effects of independent bit errors to smaller chunks Large frames lower header overhead less energy consumed higher packet error rate / BER more ARQ energy may be ameliorated by hybrid ARQ+FEC 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-55

WSN Link Protocols Framing: Frame Size Tradeoff Optimal frame size is f (E b, BER) bit energy = E b Cross-layer optimisation dynamically adjust frame size based on BER and E b 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-56

Link layer functions multiplexing framing error control flow control WSN Link Protocols Error Control Wireless sensor network concerns energy conservation data-driven application reliability requirements 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-57

Error control options ARQ FEC hybrid none Tradeoffs? WSN Link Protocols Error Control Options 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-58

WSN Link Protocols Error Control Options Error control options: ARQ when to use? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-59

WSN Link Protocols Error Control Options: ARQ Error control options: ARQ required for reliable HBH transfer why? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-60

ARQ reliability issues WSN Link Protocols Error Control Options: ARQ required for reliable HBH transfer may be needed for in-network processing not needed for reliable E2E transfer may enhance performance ARQ energy issues may reduce energy relative to only E2E ARQ why? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-62

ARQ reliability issues WSN Link Protocols Error Control Options: ARQ required for reliable HBH transfer may be needed for in-network processing not needed for reliable E2E transfer may enhance performance ARQ energy issues may reduce energy relative to E2E-only ARQ cost of single HBH retransmission < cost of multiple hops cost only incurred on bit error implication? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-63

ARQ reliability issues WSN Link Protocols Error Control Options: ARQ required for reliable HBH transfer may be needed for in-network processing not needed for reliable E2E transfer may enhance performance ARQ energy issues may reduce energy relative to only E2E ARQ cost of single HBH retransmission < cost of multiple hops cost only incurred on bit error better when Pr[error] low 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-64

WSN Link Protocols Error Control Options: FEC Reliability FEC reliability issues sufficient for quasi-reliable HBH transfer may enhance E2E performance why? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-65

WSN Link Protocols Error Control Options: FEC Reliability FEC reliability issues sufficient for quasi-reliable HBH transfer may enhance E2E performance reduces the Pr[E2E retransmission] 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-66

WSN Link Protocols Error Control Options: FEC Energy FEC Energy issues may save energy vs. E2E only ARQ why? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-67

WSN Link Protocols Error Control Options: FEC Energy FEC Energy issues may save energy vs. E2E only ARQ reduces Pr[E2E retransmission] more flexible then E2E FEC why? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-68

WSN Link Protocols Error Control Options: FEC Energy FEC Energy issues may save energy vs. E2E only ARQ reduces Pr[E2E retransmission] more flexible then E2E FEC appropriate strength can be applied to each link energy costs of coding must be considered per node what BER range to use? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-69

WSN Link Protocols Error Control Options: FEC Energy FEC Energy issues may save energy vs. E2E only ARQ reduces Pr[E2E retransmission] more flexible then E2E FEC appropriate strength can be applied to each link energy costs of coding must be considered per node more attractive when Pr[error] high coding/decoding cost incurred whether or not bit error block code more energy efficient than convolutional codes 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-70

WSN Link Protocols Error Control Options: Hybrid Hybrid error control reliability issues combine FEC and ARQ to optimise HBH & E2E performance Hybrid error control energy issues globally optimise energy consumption 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-71

WSN Link Protocols Error Control Options: No Error Control Unreliable error control many sensor applications do not need reliable transfer e.g. periodic monitoring: average or interpolate missing points Unreliable error control energy issues don t use energy on unneeded error control 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-72

Error control options WSN Link Protocols Error Control Flexibility context dependent: channel characteristics network dependent: topology and network diameter application dependent: reliability model Cross-layer optimisations Lecture XL knobs: application to specify error requirements to link layer dials: channel characteristics instrumented to link layer proper mechanism and parameter choices can be made 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-73

Sensor Network HBH Communication SN.3.4 802.15.4 Low Energy WPAN SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.3.1 Transceivers and physical communication SN.3.2 Medium access control SN.3.3 Inter-sensor link functions SN.3.4 802.15.4 low energy WPAN and ZigBee SN.4 Sensor network routing SN.5 Sensor network end-to-end transport 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-74

IEEE 802 Networks 802.15.4 Relation to other 802 Protocols 802.16 WMAN 802.11 WLAN WPAN 802.15 IEEE 802.15.4 part of 2nd generation wireless protocols (802.15 & 802.16) no similarity to 802.11/Ethernet framing or operation no similarity to other 802.15 protocols 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-75

802.15.4 Low Energy WPAN WPAN Overview WPAN: Wireless Personal Area Networks IEEE 802.15 grouper.ieee.org/groups/802/15 802.15.4 short-reach wireless network shorter range than 802.11 WLANs and 802.16 WMANs lower energy than 802.15.1 (and 802.15.3) officially Low Rate WPANs Applications [www.ieee802.org/15/pub/tg4.html] sensors interactive toys smart badges remote controls home automation 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-76

802.15.4 Low Energy WPAN Standards Overview Standard Year Freq Rates Note 802.15.4-2003 2003 868/915 MHz 2.4 GHz 20, 40 Kb/s 250 kb/s 802.15.4a 2007 802.15.4b original standard additional PHY enhancements 802.15.4-2006 2006 15.4-2003+15.4b 802.15.4c 2009 780 MHz 250 kb/s China 802.15.4d 2009 950 MHz 20, 100 kb/s Japan 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-77

802.15.4 LR-WPAN Physical Layer Characteristics 900 MHz and 2.4 GHz unlicensed ISM band implications? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-78

802.15.4 LR-WPAN Physical Layer Characteristics 2.4 GHz unlicensed ISM band most of world interference issues: 802.11b/g, 802.15, and cordless phones 250 kb/s in 16 channels DSSS 915 MHz unlicensed ISM band North America, Australia, New Zealand, some of S. America 40 250 kb/s in 10 channels DSSS or PSSS 868 MHz unlicensed band Europe 20 250 kb/s in 1 channel; plans to expand to 4 channels DSSS or PSSS (parallel sequence SS: ASK+FSK) 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-79

802.15.4 LR-WPAN Physical Layer Tradeoffs 900 MHz and 2.4 GHz unlicensed ISM band tradeoffs? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-80

802.15.4 LR-WPAN Physical Layer Tradeoffs 915 and 868 MHz unlicensed bands lower data rates (with simple coding) +lower power + longer range + fewer interference sources 2.4 GHz unlicensed ISM band + higher data rates higher power shorter range more interference sources 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-81

802.15.4 LR-WPAN Physical Layer Characteristics Spreading Parameters Data Parameters PHY Freq. Band [MHz] Chip Rate [kchip/s] Modulation Rate [kb/s] Rate [ksym/s] Symbols 868/915 868/915 optional 868/915 optional 868.0 868.6 300 BPSK 20 20 binary 902 928 600 BPSK 40 40 binary 868.0 868.6 400 ASK 250 12.5 20b PSSS 902 928 1600 ASK 250 50 5b PSSS 868.0 868.6 400 O-QPSK 100 25 16ary orth 902 928 1000 O-QPSK 250 62.5 16ary orth 2450 2044 2483.5 2000 O-QPSK 250 62.5 16ary orth 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-82

802.15.4 LR-WPAN Physical Layer Characteristics (15.4a UWB) Spreading Parameters Data Parameters PHY UWB sub-ghz UWB low UWB high 245 CSS Freq. Band [MHz] 250 750 3244 4742 5944 10234 2044 2483.5 Chip Rate [kchip/s] Modulation Rate [kb/s] 250 1000 Rate [ksym/s] 166.667 Symbols 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-83

802.15.4 LR-WPAN Physical Layer Characteristics (15.4c/d CJ) Spreading Parameters Data Parameters PHY Freq. Band [MHz] Chip Rate [kchip/s] Modulation Rate [kb/s] Rate [ksym/s] Symbols 780 China 950 Japan 779 787 1000 O-QPSK 250 62.5 16ary orth 779 787 1000 MPSK 250 62.5 16ary orth 950 956 300 BPSK 20 20 binary 950 956 GFSK 100 100 binary 2450 2044 2483.5 2000 O-QPSK 250 62.5 16ary orth 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-84

32 bit channel identifier 32 pages 802.15.4 LR-WPAN Channel Numbering 5-MSB binary encoding of pages pages 0, 1, 2 currently defined; 3 31 reserved for future 27 channels/page 27-LSB bit-vector of channels multiple channels may be used by node 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-85

802.15.4 LR-WPAN Channel Numbering Page Channel Description 0 1 2 0 826 MHz BPSK 1 10 915 MHz BPSK 11 26 2.4 GHz O-QPSK 0 868 MHz ASK 1 10 915 MHz ASK 11 26 reserved 0 868 MHz O-QPSK 1 10 915 MHZ O-QPSK 11 26 reserved 3 31 reserved reserved 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-86

802.15.4 LR-WPAN Physical Layer Responsibilities 802.15.4 physical layer [802.15.4-2006 6.1] transceiver activation and deactivations ED: energy detection within current channel LQI: link quality indicator for received packets CCA: clear channel assessment for CSMA/CA channel frequency selections data transmission and reception 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-87

802.15.4 LR-WPAN Channel Modulation: O-QPSK O-QPSK: quasi-orthogonal QPSK each data octet split into two 4-bit symbols symbols mapped to 16 nearly-orthogonal 32-b chip values symbols alt. modulated to in-phase and quadrature carriers BPSK ASK I-phase: even-indexed symbols Q-phase: odd-indexed symbols time-shifted by ½ symbol time 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-88

O-QPSK 802.15.4 LR-WPAN Channel Modulation: B-PSK BPSK: binary phase-shift keying ASK differential encoding (xor with previous bit) DSSS with 15-bit chip value 1 = 111101011001000 0 = 000010100110111 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-89

O-QPSK BPSK 802.15.4 LR-WPAN Channel Modulation: ASK PSSS ASK: amplitude shift keying PSSS: parallel-sequence spread spectrum type of OCDM: orthogonal code division multiplexing each bit multiplied by 32 +/ 1 chip sequence bits grouped into to symbols 5 b/sym for 915 MHz, 20 b/sym for 868 MHz bit group added chip-wise to get 32-chip multilevel symbol result ASK enocded 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-90

Device 802.15.4 LR-WPAN Medium Access Control: Devices node in an 802.15.4 network identified by 64-bit IEEE EUI-64 address may be assigned 16-bit short address Device types FFD: full-function device can serve as coördiantor or device RFD: reduced-function devices can only communicate FFDs 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-91

802.15.4 LR-WPAN Medium Access Control: Coördinator Coördinator may be powered; sink in generic terminology manages devices in 802.15.4 PAN assigns 16-bit short addresses for use in network beacons 16-bit PAN identifier beacons list of outstanding frames for devices exchanges data with devices in network exchanges data with peer coordinators cluster-tree topology 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-92

802.15.4 LR-WPAN Medium Access Control: PAN Topologies star topology peer-to-peer topology RFD FFD RFD FFD C RFD FFD C RFD FFD RFD FFD based on [802.15.4-2006] 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-93

802.15.4 LR-WPAN Medium Access Control: Star Topology RFD star topology RFD FFD Star topology formation FFD decides to be controller chooses unique PAN ID within radio range other FFDs and RFDs join PAN C RFD FFD RFD 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-94

802.15.4 LR-WPAN Medium Access Control: P2P Topologies P2P topology formation FFD controller election e.g. first active other nodes associate peer-to-peer topology FFD FFD C RFD FFD based on [802.15.4-2006] 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-95

802.15.4 LR-WPAN Medium Access Control: Cluster Tree Network RFD PAN ID 0 RFD FFD FFD RFD C PAN ID 1 FFD FFD RFD PAN ID 2 C FFD RFD RFD RFD RFD C RFD RFD C RFD RFD RFD RFD PAN ID 0 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-96

802.15.4 LR-WPAN Medium Access Control Superframe 802.15.4 superframe active period (16 slots) beacon (1 slot) CAP: contention access period for CSMA GTS: guaranteed time slots (GTS) for TDMA devices request and are allocated GTSs from coördinator permits QoS 802.15.4 superframe inactive period variable length time during which nodes sleep active period inactive period beacon CAP GTS 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-97

802.15.4 LR-WPAN PHY Protocol Data Unit (PPDU) Format SHR (sync hdr) [4.375 7.5B] preamble = 0 [3.75 5B] SFD [5b 2.5B] start frame delimiter = 11100101 (O-QPSK and BPSK) = inverted 0 symbol (ASK) PHR (PHY header) [1B] frame length [7b] reserved [1b] PSDU (PHY SDU) PHY payload includes MAC hdr includes FCS [0 127B] [3 23B] [2B] note: length ranges depend on PHY 00000000 00000000 preamble + SFD 00000000 11100101 length PHR MHR MAC header PSDU 0 127 B 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-98 FCS PHY 5.375 8.5B PSDU MAC frame 0 127B

MAC Header 802.15.4 LR-WPAN Frame Format (PSDU) [3 23B] frame control [2B] sequence no. [1B] dest. PAN ID [0 2B] dest. address [0 2 8B] source PAN ID [0 2B] source address [0 2 8B] aux sec hdr [0 5 6 10 14B] Frame body [0 2312B] MFR (MAC footer) Trailer: FCS [2B] control frame seq# dest. PAN ID dest. address soruce PAN ID source address aux. security hdr frame body 0 127 B MAC header 3 23B FCS 2B 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-99

MAC Header 802.15.4 LR-WPAN Frame Format: Frame Control [3 23B] frame control [2B] frame type [3b] sec. enabled [1b] frame pending [1b] ack request [1b] PANID compress [1b] reserved [3b] dest addr mode [2b] frame version [2b] src addr mode [2b] sequence no. [1B] control frame seq# dest. PAN ID dest. address soruce PAN ID source address aux. security hdr frame body 0 127 B MAC header 3 23B FCS 2B 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-100

MAC Header 802.15.4 LR-WPAN Frame Format: Addressing Fields [3 23B] dest. PAN ID [0 2B] dest. address [0 2 8B] source PAN ID [0 2B] source address [0 2 8B] Address consists of tuple PAN ID, node address src PANID,addr present if FC samode 00 control frame seq# dest. PAN ID dest. address soruce PAN ID source address aux. security hdr MAC header 3 23B frame body 0 127 B FCS 2B 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-101

Address 802.15.4 LR-WPAN Frame Format: Addresses 64-bit IEEE EUI-64 for scalability or 16-bit short address for efficiency 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-102

Frame types 000 beacon frame 001 data frame 802.15.4 LR-WPAN Frame Types 010 acknowledgement frame 011 MAC command frame 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-103

Command frame types 802.15.4 LR-WPAN Command Frame Types 0001 association request 0010 association response 0011 disassociation notification 0100 data request 0101 PAN ID conflict notification 0110 orphan notification 0111 beacon request 1000 coördinator realignment 1001 GTS (guaranteed time slot) request 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-104

Data exchange 802.15.4 LR-WPAN Medium Access Control beacon REQ ACK data ACK 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-105 7

ZigBee Overview ZigBee protocol specification upper level protocols for WSNs uses 802.15.4 MAC and PHY ZigBee Alliance industry consortium that maintains standard similar to Bluetooth, but not a L1 7 stovepipe 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-106

ZigBee Protocol Architecture ZigBee IEEE 802.15.4 [ZigBee spec] 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-107

Routing management AODV and neurfon ZigBee Protocols 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-108

Sensor Network HBH Communication SN.4 Sensor Network Routing SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.4 Sensor network routing SN.4.1 Sensor identifiers and addressing SN.4.2 Sensor network routing algorithms 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-109

Sensor Network HBH Communication SN.4.1 Sensor Identifiers and Addressing SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.4 Sensor network routing SN.4.1 Sensor identifiers and addressing SN.4.2 Sensor network routing algorithms 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-110

Identifiers and Addressing Introduction and Terminology Identifier : string used to identify an object e.g. sensor network node 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-111

Identifiers and Addressing Introduction and Terminology Identifier : string used to identify an object e.g. sensor network node Name : globally-unique persistent identifier [RFC 1737] e.g. James Philip Guenther Sterbenz note a DNS identifier is not really a name neither unique nor persistent for a given entity 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-112

Identifiers and Addressing Introduction and Terminology Identifier : string used to identify an object e.g. sensor network node Name : globally-unique persistent identifier [RFC 1737] e.g. James Philip Guenther Sterbenz note a DNS identifier is not really a name neither unique nor persistent for a given entity Address : location of a object within a topology may be topological physical, e.g. A.3.14 logical, e.g. 129.237.125.27 may be geographic, e.g. 38.957 N 95.254 W 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-113

Identifiers and Addressing Introduction and Terminology Identifier : string used to identify an object Name : globally-unique persistent identifier [RFC 1737] Address : location of a object within a topology Problem: the networking community is very sloppy in this terminology e.g. DNS name e.g. IEEE MAC address but arguably a random address in a flat topology 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-114

Identifiers and Addressing Issues and Concerns for WSNs Issues and concerns for WSNs? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-115

Sensor Network HBH Communication SN.4.2 Sensor Network Routing SN.1 Sensor and actuator network overview SN.2 Sensor network architecture and topology SN.3 Sensor network hop-by-hop communication SN.4 Sensor network routing SN.4.1 Sensor identifiers and addressing SN.4.2 Sensor network routing algorithms 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-116

Sensor Network Routing Challenges Challenges [KK2004] node deployment: random, multihop relaying needed 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-117

Sensor Network Routing Overview and Issues Classification [ASSC 2002], [KK2004] data-centric flat data-centric hierarchical location-based 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-118

Sensor Network Routing Data-Centric Routing Flat data-centric routing (selected variants) flooding gossiping directed diffusion SPIN rumour-based 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-119

Flooding Sensor Network Routing Flooding analogy: shouting to everyone advantages and disadvantages? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-120

Sensor Network Routing Flooding: Advantages Flooding advantages + simple: less processing energy savings 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-121

Sensor Network Routing Flooding: Disadvantages Flooding advantages + simple: less processing energy savings Flooding disadvantages implosion: overhead of duplicate messages overlap: multiple nodes report identical information resource blindness: no consideration for energy constraints energy waste generally energy (CPU) < energy (transmission) So what? any differences from problems in MANETs? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-122

Sensor Network Routing Flooding Tradeoffs Flooding advantages + simple: less processing energy savings Flooding disadvantages implosion, overlap, resource blindness energy waste Tradeoffs energy use even more of a concern than MANET Alternative to flooding that exploits both advantages? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-123

Sensor Network Routing Gossiping Gossiping : restricted form of flooding send only to fraction of neighbours analogy: whispering to a friend, who does the same, advantages and disadvantages? 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-124

Sensor Network Routing Gossiping: Advantages Gossiping : restricted form of flooding sent only to fraction of neighbours Gossiping advantages + still relatively simple + energy savings fraction of neighbors 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-125

Sensor Network Routing Gossiping: Advantages Gossiping : restricted form of flooding sent only to fraction of neighbours Gossiping advantages + still relatively simple + energy savings fraction of neighbors Gossiping disadvantages probability of delivery related to fraction of neighbours 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-126

SPIN Sensor Network Routing SPIN sensor protocols for information via negotiation data-centric routing based on metadata Source of data advertises data ADV message is broadcast to neighbours Interested neighbours request data typically neighbours that do not already have data REQ message returned Source of data replies DATA message contains data 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-127

Sensor Network Routing Directed Diffusion Directed diffusion data-centric routing based on attribute-value pairs Sink of data expresses interest in type of data interest is propagated (flooded) through the network node cache interests Nodes establish gradients for data gradient = (direction, strength) to neighbours optimises path of data delivery Events are delivered along gradients to sink node perform data fusion 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-128

Wireless Sensor Networks Further Reading Holger Karl and Andreas Willig, Protocols and Architectures for Wireless Sensor Networks, Wiley, 2005 I.F. Akyildiz, W. Su, Y Sankarasubramaniam, and E. Cayirci Wireless Sensor Networks: A Survey Computer Networks, vol.38 iss. 4, Mar. 2002, pp. 393 422 Kemal Akkaya and Mohamed Younis, A Survey on Routing Protocols for Wireless Sensor Networks Ad Hoc Networks, vol.3 iss. 3, May 2005, pp. 325 349 Jamal N. Al-Karaki and Ahmed E. Kamal, Routing Techniques in Wireless Sensor Networks: A Survey IEEE Wireless Communications, Dec. 2004, pp. 6 28 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-129

Wireless Sensor Networks Acknowledgements Some material in these foils is based on the textbook Murthy and Manoj, Ad Hoc Wireless Networks: Architectures and Protocols Some material in these foils enhanced from EECS 780 foils 28 November 2011 KU EECS 882 Mobile Wireless Nets Sensor Nets MWN-SN-130