this presentation presents description of a paper "Enhancement and Performance Evaluation of a Multicast Routing Mechanism in ZigBee Cluster-tree Wireless Sensor Network".

1. Enhancement and Performance Evaluation of a
Multicast Routing Mechanism in ZigBee Cluster-tree
Wireless Sensor Network.
Presented By: Raja’ “Moh’d
Taisir” Masa’deh

2.  Introduction.
 Study Of Z-Cast And Enhancement.
 ZigBee Network Formation And Address Assignment.
 ZigBee Cluster-Tree Routing Protocol.
 Z-Cast ZigBee Multicast Routing Mechanism.
 Amelioration of the Multicast Routing Table.
Outlines…

3. What’s ZigBee?
 The IEEE 802.15.4/ZigBee standard protocol which is
used to provides the wireless personal area network
(WPAN).
 It is used in an applications that need low data rate,
long battery life (low energy needed) [1].
http://www.zigbee.org/what-is-zigbee/

4.  ZigBee appears after realizing that Bluetooth is
unsuitable for many applications.
 ZigBee can communicate at speed up to 250 kbps by
10 to 75 meters distance, rather than 10 meters in
Bluetooth.
 ZigBee node take about 15 msec to power on and
obtain a packet while in Bluetooth it take about 3 sec
to power on and respond

5.  The authors proposed Z-Cast: A multicast routing mechanism
for ZigBee cluster-tree wireless sensor network.
 They were interested in amelioration of ZigBee protocol so
that requires :
1- Less memory storage.
2- Low message overhead.

6. ZigBee Coordinator (ZC).
ZigBee Router (ZR)
ZigBee end-device (ZED).

7. The address assignment mechanism based on:
 The maximum number of children.
 Depth.
 The number of routers in the network.

8. Cm: the maximum number of children.
Rm: the maximum number of routers.
Lm: the maximum depth of the network.
Where 1< n < (Cm-Rm)
Should be:
Where 1> n > (Cm-Rm)

9.  A parent device that has a Cskip(d) value of zero means that
it’s not capable of accepting children and must be treated as
an end-device.
 A parent device that has a Cskip(d) value greater than zero
can accept devices and assign them address.
ZC has a depth d= 0
d increases by 1 after each level.

10. Cskip=21, Addr= 0ZC
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
Cm=5 Rm=5 Lm=3

11. ZC
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
Cm=5 Rm=5 Lm=3
d= 0
d= 1
d= 2
d= 2
d= 3
d= 1
d= 1d= 1
d= 2
d= 2
d= 2

12. Depth in the network, d Offset value, Cskip(d)
0 21
1 5
2 1
3 0
Apply first Formula to calculate the Cskip(d), where d=0
(1 + 4 -4 -4*4^(3-0-1)/1-4)=
1-4*(4^2)/-3=
1-64/-2=
-63/-2=
21

13. Cskip=21, Addr= 0ZC
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
Cm=5 Rm=5 Lm=3
Cskip=5
Cskip=5
Cskip=5
Cskip=5
Cskip=1
Cskip=1
Cskip=1
Cskip=1
Cskip=1
Cskip=0

14. Apply Second Formula to calculate the address of each node
An= Aparent + Rm * Cskip(d) + n.
AZR1 = 0 + 0 * 21 + 1
= 1
An= Aparent + Rm * Cskip(d) + n.
AZR2 = 0 + 1 * 21 + 1
= 22
Cskip=21, Addr= 0ZC
ZR3
ZR4ZR1
ZR2
Addr= 1
Addr= 22 Addr= 43
Addr= 64

15. Cskip=21, Addr= 0ZC
ZR3
ZR4ZR1
ZR2
Addr= 1
Addr= 22 Addr= 43
Addr= 64
ZR
ZR
ZR ZR
Addr= 2
Addr= 7
Addr= 12
Addr= 17
ZR
ZR ZR ZR
Addr= 13
Addr= 14
Addr= 15
Addr= 16
An= Aparent + Rm * Cskip(d) + n.
A7 = 1 + 1 * 5 + 1
= 1 + 5 + 1
= 7

16. The ZigBee Cluster-Tree routing protocol is a hierarchal routing protocol.
- If the D is a descendant of the device, this latter should route the
message to the appropriate child.
- If the D isn’t a descendant, the device shall route the message to its
parent.
- If the following expression is true, the D device is a descendant.
A < D < A + Cskip(d -1)
- The address N of the next hop device is :
if N=D , where D > A + Rm*Cskip(d)

17. Otherwise:

18. Cskip=21, Addr= 0ZC
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
ZR
S D
ZR 0x0002 transmits a message to ZR 0x0041
0x0002 0x0041
0x0001
0x0000
0x0040

19. ZR 0x0002 transmits a message to ZR 0x0041
The tree routing protocol behaves as follows:
: ZR 0x0002 builds the data frame and sends it to its parent 0x0001.
NW.L.R.S.A NW.LR.D.A MAC.S.A MAC.D.A
0x0002 0x0041 0x0002 0x0001
NW.L.R.D.A: Network layer Routing Destination Address.
NW.L.R.S.A: Network layer Routing Source Address.
MAC.S.A: MAC Source Address
MAC.D.A: MAC Destination Address.

20. - ZR 0x0001 receives the data frame , realizes that the
message isn’t for him and has to be relayed.
- The device checks its neighbor table for the routing
destination address, and trying to find if the D is one of
its child devices.
- The device checks if the routing destination address is a
descendant that result in:
0x0001 < 0x0041 < 0x0001 +21

21. - After verifying that the destination is not a descendant, ZR
0x0001 routes the data frame to its parent, 0x0000.
NW.L.R.S.A NW.LR.D.A MAC.S.A MAC.D.A
0x0002 0x0041 0x0001 0x0000

22. - ZC receives the data frame and verifies if the routing
destination address exists in its neighbor table.
- After realizing that the D isn’t its neighbor, ZC can’t route up
because it’s the root of the tree.
- The next hop address is calculated as follows:
N= 0x0000 + 1 + [(0x0041 – (0x0000 +1))/21] * 21.
N= 0x0040 ( 64 in decimal)
NW.L.R.S.A NW.LR.D.A MAC.S.A MAC.D.A
0x0002 0x0041 0x0000 0x0040

23. - ZR 0x0040 receives the data frame and checks its neighbor
table for routing destination address.
- After verifying that the address is its neighbor, the message is
routed to it.
NW.L.R.S.A NW.LR.D.A MAC.S.A MAC.D.A
0x0002 0x0041 0x0040 0x0041

24.  Z-Cast represents a solution to support multicast in ZigBee-
based WSN.
 The objective of Z-Cast is to provide an efficient data routing
among all group members.
 Z-Cast mechanism rely on a multicast routing table in the
ZigBee coordinator and in each ZigBee router to store and
know about membership information of all groups.

25.  Multicast Routing Table (MRT):
16 bits short address that
identifies a certain group.
Contains the list of the network
short addresses of nodes being
members of the group along the
cluster tree network

26.  Multicast Routing Update:
 The MRT table entries must be updated for every join and
leave operations in the network.
 ZR must knows :
o The membership information of its directly associated nodes
o All the membership information of the child routers of its
tree.

27.  Routing in ZC:
ZR can only check its child routers by checking its MRT table,
and it can’t check the other ZR in the network.
The researchers proposed to add a flag to the multicast
message to indicate that the multicast message has
already been treated by the ZC.

28.  When a frame is received by the ZigBee Coordinator, it
analyzes the frame and checks if the destination address is a
multicast or a unicast address.
 If it is a multicast address, the ZC will add a flag to
the frame and sends it to all its directly connected child
Routers. The flag is necessary to indicate that the frame
is treated by the ZigBee Coordinator.

29.  If a multicast frame comes to the ZigBee Router without
the flag, the packet must be sent to the parent device
until reaching the ZigBee Coordinator.
 If the destination address of the frame contains a unicast
address, the default cluster-tree routing will be applied.

31.  Routing in ZR:
 When a multicast packet reaches a ZigBee Router, there are
different possibilities:
 If the multicast group address is not found in the (MRT), then
the multicast packet will be discarded.
 If the multicast group address is found in the MRT, two
different cases may occur :

32.  If the GMs address field contains only one member address of
the corresponding group, the packet will be transmitted by
unicast to the group member.
 If the GMs address field contains two or more than two addresses
of the corresponding group members, the packet will be
transmitted to all its direct child nodes.

34.  Problem in the MRT of Z-cast:
The number of update messages increases significantly especially
when dealing with long depths which can lead to network
congestion.
For this reason, we can assume that the proposed Multicast
routing table did not scale to large network size and low memory
requirements of sensor nodes that have limited memory resources.

35. E N
H I
L K
M
G_add.=0xf801
F
J
D
G_add.=0xf802

37. MRT Construction Amelioration
 When a node joins a multicast group, its parent updates its
Multicast routing table.
 The parent node verifies if the node that it added to his
multicast routing table is the first one in this group.
 If it is the case, this parent node will inform his parent node
that it has in his descendants members of a group.

38.  the parent nodes will only store the group address and not
the group member address which can reduce the memory
storage in sensor nodes.

39. MRT Update Amelioration
 If the router have already members that belong to the same
group, it will not inform the parent nodes of this
information because it will be a redundancy.

43. E N
H I
L K
M
G_add.=0xf801
F
J
D
G_add.=0xf802

45. References
[1]: Hichem Boujelben, Olfa Gaddour, Mohamed Abid. “Enhancement and
Performance Evaluation of a Multicast Routing mechanism in ZigBee Cluster-Tree
Wireless Sensor Network”, in the 10th international Multi-Conference on Systems,
Signals & Devices Hammamet, Tunisia ,March 18-21,2013.
[2]:Olfa Gaddour , Anis Koubaa, Omar Cheikhrouhou, Mohamed Abid. “Z-Cast:
A Multicast Routing Mechanism in ZigBee Cluster-Tree Wireless Sensor
Networks”, in the Third International Workshop on Sensor Networks (SN 2010),
in conjunction with ICDCS 2010, Genoa, Italy, June 21-25, 2010.

46. [3]:Olfa Gaddour, Anis koubaa, and Mohamed Abid, ”SeGCom: A secure group
communication in cluster-tree wireless sensor networks,” IEEE First International
Conference on Conference on Communications, and Networking, COMNET,pp.
1-7, November 2009.
[4]: Zigbee 2006 specification, ”ZigBee document 064112,
http://www.zigbee.org/”, 2006.
References