A NOVEL RADIO-DISJOINT MULTIPATH PROTOCOL FOR
RELIABLE DATA TRANSFER IN LOSSY WSNS
Jeongcheol Lee, Hosung Park, Seungmin Oh, Yongbin Yim and Sang-Ha Kim
Department of Computer Engineering, Chungnam National University, Daejeon, Republic of Korea
Keywords: Wireless Sensor Networks, Multipath Routing, Radio-disjoint Multipath, Geographic Multipath.
Abstract: Geographic multipath routing has been known as one of the most appropriate approaches that can improve
the end-to-end reliability via multiple redundant paths for the wireless sensor networks that have frequent
network dynamics such as both node and link failures. Studies in the literature have focused on how to make
a completely disjoint-multipath. They consider it as a node-disjoint multipath that an intermediate node
should be belonged by only a single path. However, if the paths are constructed too closely, there might
bring the interference problems such as transmission failure or corrupted packet reception even the node-
disjoint multipath schemes are used. Therefore, we propose a radio-disjoint geographic multipath protocol
which can avoids the interferences between adjacent paths by separating each path by an interference range.
To this end, we use a logical pipeline scheme for each path construction, which consists of entry and exit
location of the pipe. We demonstrate that the proposed protocol shows better performance than the previous
studies via extensive simulation in terms of end-to-end packet delivery ratio and the end-to-end delay.
1 INTRODUCTION
Multipath data delivery has known as one of the
most effective strategy to improve the end-to-end
reliability for the lossy wireless networks (Ganesan,
2001). It can provide useful opportunities for data
packets to be arrived at the network gateway such as
a sink by path redundancy. It also can reduce
frequent routing update and provide either high data
throughput or a distribution of traffic load over the
network (Jones, 2005). A variety of multipath
routing schemes (Wang, 2001 and Yang, 2010) are
studied in wireless mobile ad hoc networks
(MANETs), they however cannot be directly applied
to WSNs because of their stateful control and
deterministic construction of the paths. Namely, they
need too much control overhead or even the
deterministic paths are vulnerable to the network
dynamics.
Recently, geographic multipath routing schemes
(Oh, 2010) have been proposed for WSNs. Utilizing
characteristics of high node density and location
awareness, these schemes try to get geographical
positions which are used for both entry and exit
points of each multipath instead of maintaining node
and link states of constructed paths. After acquiring
such positions, source’s data is delivered through
these positions by using geographic routing when
only the data is generated by a source.
To improve end-to-end reliability, the primary
goal of the geographic multipath routing schemes is
to construct complete disjointed multiple paths
(Wang, 2001, Yang, 2010, and Oh, 2010). These
schemes consider the complete disjoint paths as a
node-disjoint multipath that an intermediate node in
a path is allowed to belong to only a single path, not
two or more. It is because that if multiple paths share
the one node, the node may be congested by
multiple traffics. The shared node has high
possibility to break down by depletion of energy
since the node suffers from the concentrated traffic
load.
However, even if such node-disjoint multipath
schemes are used in WSNs, there might be another
significant problem such as transmission failure or
corrupted packet reception. Since practical sensor
nodes can communicate with other nodes by
broadcast through omnidirectional antenna, there
always exist possibilities to bring collisions if
separate paths are too close to disrupt each other.
Namely, if the multipath schemes that do not take
the interference issues into account, their expensive
exertion for improving the packet reliability
411
Lee J., Park H., Oh S., Yim Y. and Kim S..
A NOVEL RADIO-DISJOINT MULTIPATH PROTOCOL FOR RELIABLE DATA TRANSFER IN LOSSY WSNS.
DOI: 10.5220/0003906104110414
In Proceedings of the 2nd International Conference on Pervasive Embedded Computing and Communication Systems (PECCS-2012), pages 411-414
ISBN: 978-989-8565-00-6
Copyright
c
2012 SCITEPRESS (Science and Technology Publications, Lda.)
Border line of
source side
X
o
Y
o
(0, 0)
Border line of
sink side
First line
θ
α
L
s
d
Figure 1: Calculating the entry positions in the proposed
protocol.
becomes useless or even cause injury to the
reliability.
Therefore, we propose a novel radio-disjoint
geographic multipath protocol. The design goal of
the proposed protocol is to construct completely
radio-disjoint multipath, which can avoid the
collisions due to interferences without any additional
interference metrics. The main idea of the proposed
protocol is to allow multiple paths to keep a certain
distance between each other.
2 NETWORK MODEL
We consider a wireless sensor network (WSN) that
consists of randomly deployed N sensor nodes over
a finite, two-dimensional planar region. We assume
that each node knows its position and the positions
of its neighbors within its transmission range R.
These assumptions can be achieved by either an
internal GPS device of sensor node or other
localization protocols (Bulusu, 2000). When an
event occurs in the WSN, sensor nodes that perceive
the event locally elect one data source to prevent
massive data duplication and collision. Also, we
assume that every sensor nodes could know the
unique sink node’s position a priory. This
assumption is generally satisfied in a variety of
emergency applications. In other cases, the data
source can obtain the position of a destination
through location service protocols. The location of a
node acts as its ID and network address.
3 PROPOSED PROTOCOL
3.1 Constructing the Multiple Pipelines
We define the straight line between a source and a
sink as the reference line. We may also call the
border line of source side as the vertical line to the
reference line passing the source. Only the nodes at
front area from the border line could be selected as a
next hop node. On the other hand, the vertical line
passing the sink referred as the border line of sink
side. Suppose that the proposed protocol needs k
number of multiple paths in order to satisfy the
desired delivery ratio given by applications. Thus we
also need k number of entry and exit positions. To
establish fully distributed pipeline, we evenly divide
the border lines into k+1 number of angles. For
example, as shown in Fig. 1, when the protocol
requires two paths, the border lines are divided by
three angels of 60 degrees. In case of three paths are
required, border lines could be divided by four
angles of 45 degrees. We may call the first straight
line from a border line of a source in a clockwise
direction as a first line. We also define the angle
between the border line and the first line as
α
. The
y-axis distance between a source and an entry
position is referred to L.
3.1.1 Obtaining Entry Positions
We first calculate an entry position of the first
pipeline through the distance L and the angle
α
of
the pipeline. After that, we calculate other entry and
exit positions using the calculated entry position of
the first pipeline. Since we calculate the reference
points based on global coordinates, we should take a
grade into account between the reference line
(source to sink) and the absolute reference line
(absolute x-axis). As shown in Fig. 1, we refer this
angle as
θ
.
Therefore, we could get the distance of the first line
through L and
α
.
(, _ #1) ( 1) /cos .Dist S Entry pos k R
α
=
−⋅
(1)
We could know the coordinate variations
between the source and the first entry position
through
θ
.
1
sin( ) ( 1) / cos ,xkR
θα
Δ= − −⋅
(2)
1
cos( ) ( 1) / cos .ykR
α
θα
Δ=
(3)
Using the equation (2) and (3), we obtain the entry
position of the first pipeline.
11
_
#1 ( , ).
ss
E
ntry pos x x y y=+Δ +Δ
(4)
where
(, )
s
s
x
y
is the coordinate of the source.
PECCS 2012 - International Conference on Pervasive and Embedded Computing and Communication Systems
412
In accordance with the definition of the proposed
protocol, the second entry position is located far
away from the first entry position as much as 2R. So
we could get the second entry position through the
following expressions.
2
2sin,xR
θ
Δ=
(5)
2
2cos,yR
θ
Δ=
(6)
12 12
_
#2 ( , ).
ss
E
ntry pos x x x y y y=+ΔΔ +ΔΔ
(7)
Consequently, the general expression for an
entry position is:
1212
_#
( ( 1) , ( 1) ).
ss
Entry pos k
x
xk xy yk y=+ΔΔ +ΔΔ
(8)
3.1.2 Obtaining Exit Positions
In the proposed protocol, sensor nodes that can
directly receive the broadcast message of a sink
should become exit nodes of logical. We call these
nodes as candidate nodes. Among these nodes, the
closest node from a source has to be selected as an
exit node of a pipeline in order to reduce the
communication costs. It is because that the path
from the closest node to the sink is the shortest path.
However, since the source cannot know information
of the candidate nodes a priori, we exploit a heuristic
approach. We consider the worst case that exit
positions of each pipeline are on the border line of
sink side. Since a data packet is forwarded from an
entry position to an exit position by geographic
routing, if the packet meets a candidate node, the
node may be the closest node from a source node.
After that, the packet is stopped and the candidate
node becomes a practical exit node.
We define the coordinate variations between an
entry position to its exit position as
3
x
Δ and
3
y
Δ
.
3_#_#
{( )/2},
d Entry pos first Entry pos final
xxx xΔ= +
(9)
3_#_#
{( )/2}.
d Entry pos first Entry pos final
yyy yΔ= +
(10)
Using the equation (9) and (10), the general
expression for an exit position is:
_# 3 _# 3
_
#( , ).
Entry pos k Entry pos k
Exit pos k x x y y=+Δ +Δ
(11)
3.2 Data Transmission
Above mentioned, the area between a source and a
sink is divided into three parts: a source side area, a
collision-free pipeline area, and a sink side area. In
other words, we use three phase geographic routing
according to these areas: the source to an entry
position, the entry position to an exit position, and
finally the exit position to the sink. We set the height
of a pipeline to R, and each pipeline is set to stay
away from each other by R. In the pipeline area, the
data packet includes the height of a pipeline and the
position of its own entry and exit points. Since the
entry and exit positions are located in the middle of
height of the pipeline, each forwarding node could
know the region of its own pipeline when it receives
the packet. Namely, only the nodes within its own
pipeline could be selected as a next hop node for
data forwarding. However, it is unreal to assume that
a next hop node is correctly located at the entry or
exit position. So the proposed protocol selects the
nearest sensor node from the position as the entry
node or exit node of a pipeline.
4 PERFORMANCE EVALUATION
We evaluate the performance of the proposed
protocol in terms of the packet delivery ratio, the
average hop counts, the average energy consumption,
and the end-to-end delay with EDM (Oh, 2010), a
representative node-disjoint geographic multipath
routing protocol in wireless sensor networks.
We implement the proposed protocol in the
Qualnet 4.0 network simulator. The model of sensor
nodes are followed by the specification of MICA2
(Polastre, 2005). The transmission range of sensor
nodes and sink are 40 m and 120 m, respectively.
700 sensor nodes are randomly and uniformly
distributed in a 500 m × 500 m sensor field. The size
of a data packet is 256 bytes. A source generates the
data packet every two seconds. The number of paths
is three. Each simulation lasts for 600 seconds.
4.1 Impact of the Number of Sensor
Nodes
Fig. 2(a) indicates the packet delivery ratio for
increasing the number of sensor nodes. As we can
see, with the increase of sensor nodes, the packet
delivery ratio also increases. Because the number of
nodes is associated with the node density, so a node
could has the more neighbor in its forwarding area
as the number of nodes increases. We observe that
the packet delivery ratio of the proposed protocol is
lower than EDM when the few number of nodes are
deployed in sensor fields. It is because that a node in
a pipeline of the proposed protocol may not find a
next hop node if the number of sensor nodes is small.
However, the graph rapidly increases in the
proposed protocol as the number of sensor nodes
increases. Because if the network could guarantee a
certain degree of node density, a transmission fail is
only occurred by interferences between paths. As
A NOVEL RADIO-DISJOINT MULTIPATH PROTOCOL FOR RELIABLE DATA TRANSFER IN LOSSY WSNS
413
100 200 300 400 500 600 700 800 900 1000
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
The packet delivery ratio (%)
The numbers of sensor nodes
EDM
Proposed Protocol
100 200 300 400 500 600 700 800 900 1000
0
200
400
600
800
1000
1200
1400
1600
1800
2000
The average energy consumption (mW)
The numbers of sensor nodes
EDM
Proposed Protocol
2345678
0.01
0.02
0.03
0.04
0.05
0.06
0.07
The end-to-end delay (s)
The numbers of multipath
EDM
Proposed Protocol
(a) (b) (c)
Figure 2: Simulation results in terms of data delivery ratio, average energy consumption, end-to-end delay.
shown in Fig. 2(b), we observe that the proposed
protocol consumes less energy than EDM when the
number of nodes is large although the proposed
protocol has more hop counts. It is because that the
receiving cost for redundant message at an
interference area significantly be increased as the
node density increases.
4.2 Impact of the Number of Multipath
In Fig. 2(c), we can observe that the end-to-end
delay of EDM rapidly increases as the number of
path increases. It means the case that many
individual paths are constructed within the narrow
area. Thus in the case, the queuing delay of each
node in this area may be significantly increased.
However, since the proposed protocol constructs
geographically separated paths, each node has low
queuing delay than EDM. Also, we observe that the
proposed protocol has more delay than EDM only
when there exist little number of multipath. It is
because that if the queuing delays of both EDM and
the proposed protocol is similar to each other, the
proposed protocol that has the more average hop
counts may take more delay times.
5 CONCLUSIONS
In this paper, we introduce a radio-disjoint
geographic multipath scheme to effectively avoid
the interferences between each path via multiple
logical pipelines between a source and a sink pair.
By separating each pipeline, geographically
collision-free paths could be constructed. We have
studied the performance of the proposed protocol
relative to EDM, a representative node-disjoint
geographic multipath protocol. We observe the
proposed protocol shows better performance in the
packet delivery ratio and the end-to-end delay.
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