Int. J. Communications, Network and System Sciences, 2010, 3, 608-611
doi:10.4236/ijcns.2010.37081 Published Online July 2010 (http://www.SciRP.org/journal/ijcns/).
Routing Strategy Selection for Zigbee Mesh Networks
Ramanathan Karthikeyan
Department of Electronics & Communication Engineering, Kumaraguru College of Technology,
Coimbatore, India
Received April 29, 2010; revised May 31, 2010; accepted July 3, 2010
Abstract
Based on IEEE 802.15.4 Low Rate-Wireless Personal Area Network (LR-WPAN) standard, the Zigbee
standard has been proposed to interconnect simple, low rate and battery powered wireless devices. The de-
ployment of Zigbee networks is expected to facilitate numerous applications such as Home-appliance net-
works, home healthcare, medical monitoring and environmental sensors. An effective routing scheme is
more important for Zigbee mesh networks. In order to achieve effective routing in Zigbee Mesh networks, a
Zigbee protocol module is realized using NS-2. The suitable routing for different data services in the Zigbee
application layer and a best routing strategy for Zigbee mesh network are proposed. The simulation shows
the selection of suitable routing for continuous data services and for bursting data services in the Zigbee ap-
plication layer and the comparison of three routing strategies namely ERD (All packets Enable Route Dis-
covery), SRD (All packets Suppress Route Discovery) and BOS (routing Based on Data Services) with re-
spect to efficiency and overhead.
Keywords: LR-WPAN, NS-2, ERD, SRD, BOS
1. Introduction
Zigbee is an emerging worldwide standard for Wireless
Personal Area Networks (WPAN). Under the main goal
to provide low-power, cost effective, flexible, reliable
and scalable wireless products Zigbee Alliance has been
developing and standardizing the Zigbee network. Based
on IEEE 802.15.4 [1], Zigbee defines three types of de-
vices. They are Zigbee Coordinator, Zigbee Router and
Zigbee End device. Zigbee networks support star, tree
and mesh topologies, self-forming and self-healing as
well as more than 65000 address spaces; thus the net-
work can be easily extended in terms of size and cover-
age area. The star topology of Zigbee is mainly designed
for the simple communication from one node to several
nodes. The tree network uses a hierarchical tree routing
mechanism. The mesh network uses the mixed routing
method combined with Z-AODV and hierarchical tree
routing.
2. Zigbee Routing Algorithms
There are two routing algorithms in Zigbee network layer.
They are modified Ad Hoc on Demand Distance Vector
(Z-AODV) and Hierarchical Routing algorithms [2].
2.1. Z-AODV
Currently AODV [3] is the easiest and most widely im-
plemented MANET protocol. Z-AODV is one of the
earliest AODV simplified versions. Z-AODV removes
the following items from the AODV specification such
as Sequence number, gratuitous RREP, hop count, Hello
message, precursor limits. In Z-AODV if the communi-
cations are unidirectional, the destination sends connect
message to the source. If data traffic is bidirectional, no
additional messages are used. In any case, a source de-
tects a link break in a route when it doesn’t receive mes-
sages from the destination.
2.2. Hierarchical Routing Algorithm
The hierarchical routing algorithm depends on the to-
pology and a distributed addressing scheme of Zigbee
networks. There are three types of devices in Zigbee
networks. They are Coordinator, Router and End device.
A Zigbee coordinator is responsible for initializing,
maintaining and controlling the network. A star network
has a coordinator with end devices directly connecting to
the coordinator. For tree and mesh networks, Zigbee de-
vices can communicate with each other in multihop

R. KARTHIKEYAN609
fashion. The network is formed by one Zigbee coordina-
tor and multiple Zigbee routers. A device can join a net-
work as an end device by associating with a coordinator
or a router [4].
Before forming a network, the coordinator determines
the maximum number of children of a router (Cm), the
maximum number of child routers of a router (Rm), and
the depth of the network (Lm) [5]. A child of a router can
be a router or an end device, so (Cm ≥ Rm). Zigbee speci-
fies a distributed address assignment using parameters
Cm, Rm and Lm to calculate the nodes network addresses.
In Zigbee if a device joins a network successfully, it can
obtain a network address from the coordinator or a router.
The basic idea of the assignment is that for the coordina-
tor and the routers in every layer, the whole address
space is logically partitioned into Rm + 1 block. The first
Rm blocks are to be assigned to the router child devices
and the last block is reserved for the (Cm – Rm) child end
devices. In order to make the assignment easily, a func-
tion Cskip can be computed by Cm, Rm and Lm. The value
of this function is the size of address sub-block being
distributed by each parent at the depth of its router child
devices for a given network depth d.
1
1( 1),
() 1,
1

 






m
mm m
Ld
mmmm
m
CL difR
Cskip dCRCR otherwise
R
1

(1)
An is computed by the following formula.
(1) 
n parentm
A
ACskipdRn (2)
Here Aparent denotes the address of the parents, n de-
notes the nth end device, and 1 ≤ n ≤ (Cm – Rm). When
Zigbee adopted the hierarchical routing algorithm and a
device called X with address A and depth d received a
packet, the device extracted the destination address
called D.
,()
(1)
1(),
()
 



  



m
DifDA RCskipd
NDA
A
Cskip dOtherwise
Cskip d
(3)
If D > A+ Rm × Cskip(d), the destination is the direct
descendent of X, and X forward the packet to this direct
descendent. If not, the destination is the indirect descen-
dents of X, so X forward the packet to one of its child
with address computed by
(1)
1(
()
DA )
A
Cskip d
Cskip d
 
 

 . (4)
In this way the network address is assigned to the net-
work elements in the Zigbee network using hierarchical
routing.
3. Simulated Results
3.1. Performance of Tree Routing and
Z-Aodvrouting over Zigbee Networks
A Zigbee protocol module is developed using NS-2 with
the following specifications. The simulation area is 50 ×
50 m2, the number of nodes is 21, Transmission range is
12 m, Packet error ratio is 0.2%, Data rate is 250 Kbps,
Packet size is 70 bytes and Simulation time is 150 sec.
From Figure 1 we observe that, the tree routing has
faster response in forwarding the data packets since it
doesn’t need to initiate the routing tables. The flow starts
at 25th second. At 27th second, 7 tree routed data packets
are arrived at the destination node. The Z-Aodv routed
data packets arrived at 27th second only because Z-Aodv
must initiate the routing discovery. Z-Aodv after estab-
lishing its routing table the number of data packets in
two routing methods will tend to be the same. Z-Aodv
always chooses the route with less number of hops and
the tree routing usually won’t obtain shorter route. So the
data frames transmitted in tree routing network are al-
ways 1.2 to1.4 times more than the data frames transmit-
ted in Z-Aodv network. So the tree routing of Zigbee is
suitable for bursting data transmissions and Z-Aodv is
suitable for continuous data transmissions.
3.2. Comparison of Three Routing Strategies for
Zigbee Mesh Network
A data flow consists of mixture of continuous data and
bursting data is used in this simulation. The Zigbee mesh
network uses a mixed routing mechanism combined with
tree routing and Z-Aodv routing [6].
Figure 1. Performance comparison of tree routing and
Z-AODV routing.

R. KARTHIKEYAN 610
The Discover Route Field in the header of the data
frames decides the routing approach for the data frames.
If it has the value of Suppress Route Discovery, it uses
the routing tables that exist already. When there is no
corresponding address of the destination node the net-
work will use tree routing.
If the Discover Route Field has the value of Enable
Route Discovery and when the routing address is there in
the routing table, the routing will follow this routing ta-
ble. Otherwise the router will initiate the routing discov-
ery. When the node has no ability to initiate the routing
discovery, it will use tree routing. Based on the previous
section simulation results, we can choose the binding
data services in the Zigbee application layer will always
use Enable Route Discovery routing method and the
bursting data services in the Zigbee application layer will
always use the Suppress Route Discovery routing method.
This kind of routing method is called as routing based on
data services. Efficiency is defined as the ratio between
the transmitted data bytes and the total transmitted bytes.
Figure 2 shows the comparison of three routing strate-
gies with respect to efficiency.
The efficiency of SRD routing method is the highest.
The efficiency of ERD routing method is the lowest.
BOS has to initiate the routing discovery for continuous
data flow alone. ERD has to initiate the routing discov-
ery for both continuous and bursting data flow. The in-
crease of control overhead makes the efficiency of ERD
low.
Figure 3 shows the average number of frames re-
quired to transmit a single data packet in all the three
routing strategies for different bursting data conditions.
SRD requires more frames to transmit a single data
packet, since it uses the defined tree path. But ERD
elects the shortest path and in turn it requires fewer
Figure 2. Comparison of ERD, SRD & BOS in the aspect of
Efficiency.
Figure 3. Average number of frames required to transmit a
data packet in ERD, SRD & BOS.
frames. The BOS routing method cuts down the con-
sumption of routing discovery for bursting data since it
uses tree routing. So it has the least overhead. Compara-
tively BOS has the least overhead than ERD and SRD,
which accordingly reduce the power consumption.
Thus in turn it is more suitable and much beneficial
for Low Power IEEE 802.15.4 & Zigbee.
4. Conclusions
In this paper, the selection of suitable routing for con-
tinuous data services and for bursting data services in the
Zigbee application layer is proposed. The three routing
strategies namely Enable Route Discovery(ERD), Sup-
press Route Discovery(SRD), and routing Based On data
Services(BOS) are compared in the aspects of Efficiency,
overhead and BOS is proposed as the suitable routing
strategy for Zigbee mesh networks.
5. References
[1] IEEE. Std. 802.15.4, “Wireless Medium Access Control
(MAC) and Physical Layer (PHY) Specifications for Low
Rate Wireless Personal Area Networks,” 2003.
%
)
(
[2] J. Sun, Z. X. Wang and H. Wang, “Research on Routing
Protocols Based on Zigbee Network,” Proceedings of the
Third International Conference on Intelligent Information
Hiding and Multimedia Signal Processing, Kaohsiung,
Taiwan, November 26-28, 2007, pp. 639-642.
[3] C. Perkins and E. B. Royer, “Ad Hoc On-demand Dis-
tance Vector(AODV) Routing,” RFC 3561, July 2003.
[4] T. Kim, D. Kim and S. Yoo, “Shortcut Tree Routing in
Zigbee Networks,” In 2nd International Symposium on
Wireless Pervasive Computing, San Juan, Puerto Rico,
February 5-7, 2007, pp. 42-47.

R. KARTHIKEYAN 611
[5] Zigbee Alliance, “Zigbee Specification Version 1.0,” De-
cember 14th, 2004. http://www.zigbee.org
[6] X. H. Li and K. L. Fang, “An Improved Zigbee Routing
Strategy for Monitoring Systems,” IEEE Proceedings of
First International Conference on Intelligent Networks
and Intelligent Systems, Wuhan, 2008, pp. 255-258.