Wireless Communication And Mobile Network - ZigBee

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  • Wireless Communication And Mobile Network - ZigBee

    1. 1. ZIGBEE WIRELESS NETWORKS
    2. 2. • WSN • IEEE 802.15.4 • ZigBee
    3. 3. WSN What is WSN?
    4. 4. WSN • Wireless Sensor Network (WSN) is a network of small spatially distributed devices that can communicate with each other over the air
    5. 5. WSN • to monitor • to control • both to monitor and control
    6. 6. WSN • Application Areas • less expensive • more flexible
    7. 7. WSN Opportunities
    8. 8. WSN • Opportunities • Unattended areas • Large-scale networks with many nodes • Increase reliability by rerouting possibility • Mobility
    9. 9. Advanced Metering
    10. 10. Asset Tracking
    11. 11. Home Automation
    12. 12. Industrial Automation
    13. 13. WSN Technology Requirements
    14. 14. WSN • WSN Technology Requirements • Low cost and small size devices • Low power consumption • Unlicensed radio bands • Scalability: Support large number of nodes • Flexibility: Simple deployment and network extension
    15. 15. ZigBee Bluetooth WiFi Standard IEEE 802.15.4 IEEE 802.15.2 IEEE 802.11 Radio DSSS FHSS DSSS Frequency 2.4GHz 2.4GHz 2.4/5GHz Topology Star/Mesh/P2P Piconet Star/Mesh Max Nodes 255/65000+ 7 30 Range ~50m ~10m ~100m Duty Cycle Low Moderate Low to Moderate Bandwidth 250Kbps 1Mbps 108Mbps
    16. 16. IEEE 802.15.4
    17. 17. !quot;#$%&(PHY)'(%)*+,&(MAC)'-./0&(Data Link)1 8 ZigBee Alliance 9:,;<=>?'-.@ABCD,'EFGHIJ IEEE 802.15.4 STIJquot; • LowRate-Wireless Personal Area Network • Physical (PHY) and Medium Access Control (MAC)
    18. 18. IEEE 802.15.4 • Type of network device • Data transfer models • Protocol stack • Physical layer (PHY) • Medium Access Control sub-layer (MAC) • Functional overview
    19. 19. IEEE 802.15.4 Type of network devices
    20. 20. IEEE 802.15.4 • Types of network devices • RFD (Reduced Functionality Device) • FFD (Full Functionality Device)
    21. 21. IEEE 802.15.4 • RFD (Reduced Functionality Device) • cancommunicate only to a single FFD in the network and no RFDs • requires little memory, processing and power resource for operation • e.g., sensor nodes, actuator nodes
    22. 22. IEEE 802.15.4 • FFD (Full Functionality Device) • capable to act as network coordinator and as an end-device • can communicate both FFDs and RFDs • requires extra memory and processing power, consumes more energy compared to RFD
    23. 23. IEEE 802.15.4 Data transfer models
    24. 24. IEEE 802.15.4 • Data transfer models • Star • Peer-to-peer • *Mesh
    25. 25. IEEE 802.15.4 • Star • networkis simple in set up and deployment • dataforwarding is possible only by coordinator (two- hop only) • coveragearea is limited by one-hop transmission range
    26. 26. IEEE 802.15.4 • Peer-to-peer • data frames can be delivered via several intermediate node • largespatial areas can be covered by a single network • complex packet routing algorithm are required
    27. 27. IEEE 802.15.4 Protocol Stack
    28. 28. IEEE 802.15.4 • Physical layer (PHY) • Medium Access Control sub-layer (MAC)
    29. 29. IEEE 802.15.4 Physical layer
    30. 30. IEEE 802.15.4 • Physical layer • activation and deactivation of the radio transceiver • energy detection (ED) within the current channel • link quality indicator (LQI) for received packets
    31. 31. IEEE 802.15.4 • channel frequency selection • data transmission and reception • clear channel assessment (CCA) for carrier sense multiple access with collision avoidance (CSMA-CA)
    32. 32. IEEE 802.15.4 • Physical layer (PHY) • 802.15.4 PHY communication on 3 frequency bands: Frequency Channels Data rates Availability Sensitivity 2450 16 250 Worldwide >= -85dBm 915 10 40, 250 US, AUS >= -92dBm 868 1 20, 100 Europe >= -92dBm
    33. 33. IEEE 802.15.4 • Physical layer •a transmitter shall be capable of transmitting at least –3 dBm (0.5 mW), normally at 0 dBm (1 mW) •a receiver shall have a receiver maximum input level greater than or equal to –20 dBm (0.01 mW)
    34. 34. IEEE 802.15.4 • Physical layer • 2450MHz is the most commonly used band for WSNs because: • it’s available worldwide without need for licensing • it has highest data rate achieved with simplest modulation • Sub1-GHz bands (915/868 MHz) provide better signal range than 2.4 GHz band
    35. 35. IEEE 802.15.4 • Physical layer • when starting the network the coordinator scans pre- configured channels and choose one with least activity detected • when joining the WPAN, a device scans through the given set of channels and report discovered networks to higher layers to permit join
    36. 36. IEEE 802.15.4 MAC layer
    37. 37. IEEE 802.15.4 • Medium Access Control sub-layer • generating network beacons if the device is a coordinator • synchronizing to network beacons • supporting PAN association and disassociation
    38. 38. IEEE 802.15.4 • Medium Access Control sub-layer • supporting device security • employing the CSMA-CA mechanism for channel access • handling and maintaining the GTS mechanism • providing a reliable link between two peer MAC entities
    39. 39. IEEE 802.15.4 Functional Overview
    40. 40. IEEE 802.15.4 • Functional Overview • Superframe structure • Data transfer model • Frame structure • Improving probability of successful delivery • Power consumption considerations • Security
    41. 41. IEEE 802.15.4 Superframe structure
    42. 42. IEEE 802.15.4 • Superframe structure • thisstandard allows the optional use of a superframe structure. The format of the superframe is defined by the coordinator. The superframe is bounded by network beacons sent by the coordinator and is divided into 16 equally sized slots
    43. 43. $* 123)* 4-#* +,* #$('5&6$* +0$* (+57'+75$* ,.* +0$* (78$5.549$(:* 2-/* #$% $*',-+$-+&,-*4''$((*8$5&,#*=>21?*6$+;$$-*+;,*6$4',-(*',98$+$(*;& C>2* 9$'04-&(9:* 2@@* +54-(4'+&,-(* 45$* ',98@$+$#* 6/* +0$* +&9$* ,.* +0 JAKLH&MHKN>OG 2>O$HO$B>O 3NNHGG&9HAB>% $BLH JAKLH&MHKN>OG Supreframe structure without GTSs
    44. 44. IEEE 802.15.4 superframe can have an active and an • Optionally, the inactive portion. During the inactive portion, the coordinator may enter a low-power mode. The beacon frame is transmitted in the first slot of each superframe. If a coordinator does not wish to use a superframe structure, it will turn off the beacon transmissions
    45. 45. 2>O$HO$B>O 3NNHGG&9HAB>% $BLH JAKLH&MHKN>OG 3N$BIH&9HAB>% !OKN$BIH&9HAB>% $BLH 1234(,$56748,(+(&-,$*'(49'4(,$:2';.4'$<=7* Superframe structure without GTSs 4+&,-(*,5*488@&'4+&,-(*5$G7&5&-<*(8$'&.&'*#4+4*64-#;&#+0)*+0$*123*',
    46. 46. IEEE 802.15.4 • For low-latency applications or applications requiring specific data bandwidth, the PAN coordinator may dedicate portions of the active superframe to that application. These portions are called guaranteed time slots (GTSs). The GTSs form the contention-free period (CFP), which always appears at the end of the active superframe starting at a slot boundary immediately following the CAP
    47. 47. <* +,* L,&-* +0$* -$+;,5E:* 2@@* ',-+$-+&,-C64($#* +54-(4'+&,-(* &(* ',98@$ $%&'$*+54-(9&++&-<*&-*4*IHA*$-(75$(*+04+*&+(*+54-(4'+&,-*&(*',98@$+$*6$ *,.*+0$*>F1:*B,5$*&-.,594+&,-*,-*+0$*(78$5.549$*(+57'+75$*'4-*6$*., JAKLH&MHKN>OG 2>O$HO$B>O 2>O$HO$B>O JAHH&9HAB>% 3NNHGG&9HAB>% $BLH 1234(,$!6748,(+(&-,$*'(49'4(,$:2';$<=7* Superframe structure with GTSs ,($-./,0
    48. 48. Superframe structure with GTSs
    49. 49. IEEE 802.15.4 Data transfer model
    50. 50. IEEE 802.15.4 • Data transfer models • type of data transfer transactions • device -> coordinator • coordinator -> device • device -> device
    51. 51. G$%*& )& 3%@+(%& 4+,$%,& 0.& 0/)*,-%/& 3)0)& 0.& )& (../3+*)0./& +*& )& 7%)(.*:%*)7;%3& < IEEE 802.15.4 *%04./5& 7%)(.*8& G$%*& 0$%& 7%)(.*& +,& -.6*3A& 0$%& 3%@+(%& ,1*($/.*+?%,& 0.& 0$%& ,6 )22/.2/+)0%& 0+'%A& 0$%& 3%@+(%& 0/)*,'+0,& +0,& 3)0)& -/)'%A& 6,+*H& ,;.00%3& BIJ9:B9 (../3+*)0./& ')1& )(5*.4;%3H%& 0$%& ,6((%,,-6;& /%(%20+.*& .-& 0$%& 3)0)& 71& )(5*.4;%3H'%*0&-/)'%8&#$+,&,%>6%*(%&+,&,6'')/+?%3&+*&K+H6/% L8 +H4L>AM' *>>A5BJK4>A ,HIBNH • device -> coordinator OHKN>J • beacon-enable PAN ,K4K • slotted CSMA-CA )NMJ>LFH5CPHJ4 MBQ'AHRSHG4H5N
    52. 52. 2134)-%567.884*1/'(1.*%(.%'%/..)01*'(.)%1*%'%9-'/.*:-* IEEE 802.15.4 G$%*&)&3%@+(%&4+,$%,&0.&0/)*,-%/&3)0)&+*&)&*.*7%)(.*:%*)7;%3&<9=A&+0&,+'2;1&0/)* 6*,;.00%3&BIJ9:B9A&0.&0$%&(../3+*)0./8&#$%&(../3+*)0./&)(5*.4;%3H%,&0$%&,6((% 71& 0/)*,'+00+*H& )*& .20+.*);& )(5*.4;%3H'%*0& -/)'%8& #$%& 0/)*,)(0+.*& +,& *.4& (. ,6'')/+?%3&+*&K+H6/% E8&& +H4L>AM' *>>A5BJK4>A ,HIBNH • device -> coordinator ,K4K • nonbeacon-enabled PAN )NMJ>LFH5CPHJ4 • unslotted CSMA-CA MBQ'AHRSHG4H5N 2134)-%?67.884*1/'(1.*%(.%'%/..)01*'(.)%1*%'%*.*9-'/.*:
    53. 53. )**+,-&.(*+'.):&*/5%,<%0'($%'0D))%001D5'+%)%=(-*&'*1'($%',.(.'+%CD%0('3@'(+.& 1+.;%>'?$%'=%&,-&<',.(.'1+.;%'-0'($%&'0%&('D0-&<'05*((%,'BEA74B7'*+9'-1'=* .):&*/5%,<;%&(' F0%%' G>H>I>JK>' ?$%' ,%2-)%' ;.@' .):&*/5%,<%' ($%' 0D))%001 IEEE 802.15.4 (+.&0;-((-&<' .&' *=(-*&.5' .):&*/5%,<;%&(' 1+.;%>' ?$%' (+.&0.)(-*&' -0' &*/' )*;=5%(-*&'*1'($%',.(.'(+.&0.)(-*&9'($%';%00.<%'-0'+%;*2%,'1+*;'($%'5-0('*1'=%& ?$-0'0%CD%&)%'-0'0D;;.+-M%,'-&'N-<D+% O> 4H$L>AM& 2>>A%BJK$>A 5HIBNH OHKN>J • coordinator -> device • beacon-enable PAN 5K$K&8HQRHG$ 3NMJ>LFH%CPHJ$ • slotted CSMA-CA 5K$K 3NMJ>LFH%CPHJ$
    54. 54. .==+*=+-.(%',%2-)%'(*';.:%')*&(.)('.&,'+%CD%0('($%',.(.>'7',%2-)%';.@';.:%') )*;;.&,'+%CD%0(-&<'($%',.(.9'D0-&<'D&05*((%,'BEA74B79'(*'-(0')**+,-&.(*+'. ?$%' )**+,-&.(*+' .):&*/5%,<%0' ($%' 0D))%001D5' +%)%=(-*&' *1' ($%' ,.(.' IEEE 802.15.4 .):&*/5%,<;%&('1+.;%>'P1'.',.(.'1+.;%'-0'=%&,-&<9'($%')**+,-&.(*+'(+.&0;-(0'( BEA74B79' (*' ($%' ,%2-)%>' P1' .' ,.(.' 1+.;%' -0' &*(' =%&,-&<9' ($%' )**+,-&.(*+' -& .):&*/5%,<;%&(' 1+.;%' 1*55*/-&<' ($%' ,.(.' +%CD%0(' *+' -&' .' ,.(.' 1+.;%' /-($ G>H>I>JK>'P1'+%CD%0(%,9'($%',%2-)%'.):&*/5%,<%0'($%'0D))%001D5'+%)%=(-*&'*1'($% .):&*/5%,<;%&('1+.;%>'?$-0'0%CD%&)%'-0'0D;;.+-M%,'-&'N-<D+% Q>'' 4H$L>AM& 2>>A%BJK$>A 5HIBNH • coordinator -> device 5K$K&8HQRHG$ 3NMJ>LFH%CPHJ$ • nonbeacon-enabled PAN 5K$K • unsloted CSMA-CA 3NMJ>LFH%CPHJ$ 2134(,$>67-..4)1/&'1-)$+(-.$&$/--(01)&'-($1)$&$)-)8,&/
    55. 55. IEEE 802.15.4 • device -> device (Peer-to-peer) • ina peer-to-peer PAN, every device may communicate with every other device in its radio sphere of influence. In order to do this effectively, the devices wishing to communicate will need to either receive constantly or synchronize with each other. In the former case, the device can simply transmit its data using unslotted CSMA-CA. In the latter case, other measures need to be taken in order to achieve synchronization. Such measures are beyond the scope of this standard
    56. 56. IEEE 802.15.4 Frame structure
    57. 57. IEEE 802.15.4 • Frame structure • Beacon frame • Data frame • Acknowledgement frame • MAC Command frame
    58. 58. IEEE 802.15.4 Beacon frame
    59. 59. ,,)34$&+,)% 5&$% +)&$:64+% $(+8,)D% C(&5,$:% 4$% &% C(&5,$*($&C<(3% -./=% E9(% B.@% '&2<,&3% 5,$+&4$:% +9 7'();)&6(%:'(54;45&+4,$0%OEA%;4(<3:0%'($34$>%&33)(::%;4(<3:0%&$3%C(&5,$%'&2<,&3%P:((%Q=!=!=quot;R=%E9(%B.@ &2<,&3% 4:% ')(;4F(3% 84+9% &% B.@% 9(&3()% PBSTR% &$3% &''($3(3% 84+9% &% B.@% ;,,+()% PBMTR=% E9(% BST ,$+&4$:%+9(%B.@%M)&6(%@,$+),<%;4(<30%C(&5,$%:(U7($5(%$76C()%PVA/R0%&33)(::4$>%;4(<3:0%&$3%,'+4,$&<< 9(%&7F4<4&)2%:(57)4+2%9(&3()=%E9(%BMT%5,$+&4$:%&%quot;W*C4+%;)&6(%59(5D%:(U7($5(%PM@AR=%E9(%BST0%B.@ &2<,&30%&$3%BMT%+,>(+9()%;,)6%+9(%B.@%C(&5,$%;)&6(%P4=(=0%B-XYR= 7';'=':7'>A 8' :' <'>A':7' 8' $quot; !quot; 8' 2L4H4GZ %quot; :<' )U[BFBKA@' -HM5BMC' FGH% 0AKSH' &HWUHMLH' )55AHGGBMC' Y1&' JHKL>M' &U?HAXAKSH' 0*&' &HLUAB4@' )55AHGG' 04@D.E'(' % *>M4A>F' +USVHA' 0BHF5G' 0BHF5G' -K@F>K5' &?HLBXBLK4B>M' .HK5HA' 0BHF5G' % (.$' ()*'-K@F>K5' (0$ -./'5H?HM5HM4' :' O'P'Q<'4>'8<Rquot;#quot;$quot;#quot;%quot;#quot;!quot;' 2L4H4GZ QGHH'LFKUGH'=R' -AHKSVFH' &4KA4'>X'0AKSH' 0AKSH'%HMC4D'T' &AB% -&,N' &HWUHMLH' ,HFBSB4HA' $HGHAIH5' D.E'(% -./'-K@F>K5' &.$' -.$' QGHH'LFKUGH'=R'P'6'P'Q<'4>'8<R'P'$'P'S'P'!' 2894('%6:;<5='3.*85%>8'?%+1%*='%@'.5+/%1(.3'%./-%*='%&AB%,.5C'* Schematic view of the beacon frame and the PHY packet 9(%B.@%C(&5,$%;)&6(%4:%+9($%'&::(3%+,%+9(%-SZ%&:%+9(%-SZ%:()145(%3&+&%7$4+%P-AXYR0%89459%C(5,6(:%+9 SZ%'&2<,&3=%E9(%-SZ%'&2<,&3%4:%')(;4F(3%84+9%&%:2$59),$4?&+4,$%9(&3()%PASTR0%5,$+&4$4$>%+9(%-)(&6C< (U7($5(%&$3%A+&)+*,;*M)&6(%X(<464+()%PAMXR%;4(<3:0%&$3%&%-SZ%9(&3()%P-STR%5,$+&4$4$>%+9(%<($>+9%,;%+9 SZ%'&2<,&3%4$%,5+(+:=%E9(%AST0%-ST0%&$3%-SZ%'&2<,&3%+,>(+9()%;,)6%+9(%-SZ%'&5D(+%P4=(=0%--XYR=
    60. 60. IEEE 802.15.4 Data frame
    61. 61. quot;quot; $%&'()*+,*-.)((/ 01230&345&6quot;781910!734&38quot;3&4quot;7:18;#<9387&+,*- quot;!quot;#quot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quot; 6758*,%99:;.<,+'(7.%=7,2%1)%(<,%4'('%)*'+,%'04%(<,%>?@%A'./,( +')12.2)6287,21)#*)62**'1).,).+');<=)*%>728'&)251)#*)&'0'&&'1).,)2*).+');<=)*'&?#/')12.2)%5#.)@;ABC Schematic view of the data frame and the PHY packet +');<=)6287,21)#*)6&'0#E'1)-#.+)25);FG)251)266'51'1)-#.+)25);quot;G9):+');FG)/,5.2#5*).+')quot;&23 ,5.&,7)0#'714)12.2)*'H%'5/')5%3>'&)@BAID4)211&'**#5$)0#'71*4)251),6.#,52778).+')2%E#7#2&8)*'/%&#.8)+'21' +');quot;G)#*)/,36,*'1),0)2)(JK>#.)quot;=A9):+');FG4);<=)6287,214)251);quot;G).,$'.+'&)0,&3).+');<=)12 &23'4)@#9'94);LBCD9
    62. 62. IEEE 802.15.4 Acknowledgement frame
    63. 63. FG4) /,5.2#5#5$) .+') L&'23>7') A'H%'5/') 251) Aquot;B) 0#'71*4) 251) .+') LFG 287,21)#5),/.'.*9):+')AFG4)LFG4)251)LFM)6287,21).,$'.+'&)0,&3).+')L 1O$H$G= )& +& )& & C -D% & KAJPH& #HLMHNOH& K2#& 2>N$A>F& 4MPQHA& E8F3'B,*% 6R8& 6K8& 9RT&%H?HN%HN$& +& ,& 1O$H$G= VGHH&OFJMGH&/X #$JA$&>Z& KAJPH& >?@% 9AHJPQFH& KAJPH& 0HNC$D&Y& 9#5S& #HLMHNOH 5HFBPB$HA& 8HGHAIH%& 3'B,*% #R8& 9R8& 9RT&9J@F>J%& VGHH&OFJMGH&/X&U&/& Schematic view of the acknowledgment frame ;.<,+'(7.%=7,2%1)%(<,%'./0123,45+,0(%)*'+,%'04%(<,%>?@ and the PHY packet
    64. 64. IEEE 802.15.4 MAC Command frame
    65. 65. quot;!quot;#quot;$%&'(%)*++,-.%/0,+1 $%&'( )quot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quot; A56<01%=#B>)@1+,95)%451C%*/%9@1%&'(%)*++,-.%/0,+1%,-.%9@1%DEF%3,)G19 Schematic view of the MAC command frame ,(*2LGM*$+*/,(7*?6++(8*/-*/,(*LEN*6+*/,(*LHGM9*.,$0,*:(0-5(+*/,(*LEN*?6<;-68=*>,(*LEN*?6<;-68*$ and the PHY packet '(1$D(8*.$/,*67*HEF9*0-7/6$7$7%*/,(*L'(65:;(*H(O&(70(*678*H#G*1$(;8+9*678*6*LEF*0-7/6$7$7%*/,(*;(7%/, 1* /,(* LEN* ?6<;-68* $7* -0/(/+=* >,(* ?'(65:;(* +(O&(70(* (76:;(+* /,(* '(0($P('* /-* 60,$(P(* +<5:- <70,'-7$Q6/$-7=*>,(*HEF9*LEF9*678*LEN*?6<;-68*/-%(/,('*1-'5*/,(*LEN*?60R(/9*@$=(=9*LLGMC=
    66. 66. IEEE 802.15.4 Improving probability of successful delivery
    67. 67. IEEE 802.15.4 • Improving probability of successful delivery • CSMA-CA mechanism • Frame acknowledgement • Data verification
    68. 68. IEEE 802.15.4 CSMA-CA Mechanism
    69. 69. IEEE 802.15.4 • CSMA-CA mechanism • Beacon-enabled PAN • slotted CSMA-CA • Nonbeacon-enabled PAN • Unslotted CSMA-CA
    70. 70. IEEE 802.15.4 Frame acknowledgement
    71. 71. IEEE 802.15.4 • Frame acknowledgement •a successful reception and validation of a data or MAC command frame can be optionally confirmed with an acknowledgment. If the receiving device is unable to handle the received data frame for any reason, the message is not acknowledged
    72. 72. IEEE 802.15.4 • Frame acknowledgement • ifthe originator does not receive an acknowledgment after some period, it assumes that the transmission was unsuccessful and retries the frame transmission. If an acknowledgment is still not received after several retries, the originator can choose either to terminate the transaction or to try again. When the acknowledgment is not required, the originator assumes the transmission was successful
    73. 73. IEEE 802.15.4 Data verification
    74. 74. IEEE 802.15.4 • Data verification • inorder to detect bit errors, an FCS mechanism employing a 16-bit International Telecommunication Union— Telecommunication Standardization Sector (ITU-T) cyclic redundancy check (CRC) is used to detect errors in every frame
    75. 75. IEEE 802.15.4 Power consumption considerations
    76. 76. IEEE 802.15.4 • Power consumption considerations devices will require duty-cycling to • Battery-powered reduce power consumption. These devices will spend most of their operational life in a sleep state; however, each device periodically listens to the RF channel in order to determine whether a message is pending. This mechanism allows the application designer to decide on the balance between battery consumption and
    77. 77. IEEE 802.15.4 Security
    78. 78. IEEE 802.15.4 • Security • The cryptographic mechanism in this standard is based on symmetric-key cryptography and uses keys that are provided by higher layer processes. The establishment and maintenance of these keys are outside the scope of this standard. The mechanism assumes a secure implementation of cryptographic operations and secure and authentic storage of keying material
    79. 79. ZIGBEE
    80. 80. ZIGBEE • Protocol Stack • Node Types • Network Establishment • Network Topologies
    81. 81. ZIGBEE Protocol Stack
    82. 82. ZIGBEE • Inorder to adopt WSN technology for use in real-life applications an association of industry companies: ZigBee Alliance has specified a full protocol suite that provide efficient high level communication in WSNs
    83. 83. ZIGBEE • ZigBee Alliance • http://www.zigbee.org • ZigBee Standard • PHY & MAC = IEEE 802.15.4 • APS & NWK & APL
    84. 84. ZIGBEE Node Types
    85. 85. ZIGBEE • Node Types • Coordinator • Router • End device
    86. 86. ZIGBEE • Coordinator • • configuring key network parameters • network start • admission of other nodes • network address assignment
    87. 87. ZIGBEE • Router • •a node has IEEE 802.15.4 FFD capability but not act as network coordinator is called a router • to extend network coverage area beyond transmission range of a single device • to increase network reliability by creating data routing paths
    88. 88. ZIGBEE • End device • • nodes of this type can directly communication only with a single router or coordinator. Among other node types end devices consume least processing, memory and power resources and usually deployed on batteries in power saving mode. Therefore ZigBee end devices correspond to reduced functionality devices (RFD) in IEEE 802.15.4 standard
    89. 89. ZIGBEE Network Establishment
    90. 90. ZIGBEE • ZigBee network establishment • Network layer (NWK) in ZigBee protocol stack extends 802.15.4 functionality in terms of possible node interconnections, data transmission and network management and provide mechanisms for exchange on the level of entire network
    91. 91. ZIGBEE Parent-child relationship
    92. 92. ZIGBEE • Parent-child relationship • child - the node that has entered the network • parent- the node that has provided network access
    93. 93. ZIGBEE • Parent-child relationship • only coordinator and routers can act as parent nodes •a child node can have only one parent at a time •a child node is able to change parent • ZigBeenetwork hierarchy can be visualized as a tree with coordinator being on top and end devices being tree leaves
    94. 94. ZIGBEE • Parent-child relationship • Basedon such hierarchical following parameters should be specified by user to configure the network: • Maximum number of direct children • Maximum network depth
    95. 95. ZIGBEE • Node addressing • Each node that joins ZigBee network receives temporary 16-bit long network address (e.g., 3CB8). Communication on network level is performed based on this address while direct transmission between two neighboring devices is done based on MAC address
    96. 96. ZIGBEE Network Topologies
    97. 97. ZIGBEE • Network Topologies • Star • Tree • Mesh
    98. 98. ZIGBEE • Star • onlycoordinator can have child nodes • network coverage area is limited by coordinator transmission range • networkis simple in setup and deployment • coordinatoris the only node that can route data packets
    99. 99. ZIGBEE • Tree • routers are able to have child nodes • directcommunication is possible only in terms of parent-child relation • hierarchicalrouting without alternative paths
    100. 100. ZIGBEE • Mesh • routers are able have child nodes • directcommunication is possible between any FFD devices within transmission range of each other • optimum and dynamic routing with alt paths

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