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

 2012 SCITEPRESS (Science and Technology Publications, Lda.)

Border line of

source side

(0, 0)

Border line of

sink side

First line

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

. 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

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

Therefore, we could get the distance of the first line

through L and

(, _ #1) ( 1) /cos .Dist S Entry pos k R

−⋅

(1)

We could know the coordinate variations

between the source and the first entry position

through

sin( ) ( 1) / cos ,xkR

θα

Δ= − ⋅ −⋅

(2)

cos( ) ( 1) / cos .ykR

θα

Δ= − ⋅ −⋅

(3)

Using the equation (2) and (3), we obtain the entry

position of the first pipeline.

#1 ( , ).

ntry pos x x y y=+Δ +Δ

(4)

where

(, )

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.

2sin,xR

Δ= ⋅

(5)

2cos,yR

Δ= ⋅

(6)

12 12

#2 ( , ).

ntry pos x x x y y y=+Δ−Δ +Δ−Δ

(7)

Consequently, the general expression for an

entry position is:

1212

( ( 1) , ( 1) ).

Entry pos k

xk xy yk y=+Δ−−⋅Δ +Δ−−⋅Δ

(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

Δ and

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

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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