Challenges for Routing Protocols in Wireless Sensor Networks: A Survey

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Challenges for Routing Protocols in Wireless
Sensor Networks: A Survey
Auwal Tijjani Amshi
Email: auwalamshi@gmail.com
School of Software Engineering, Nanchang Hang Kong University (南昌航空大學).
Abstract- Wireless Sensor Networks (WSNs) consist of small nodes with sensing,
computation, and wireless communications capabilities. Recent advances in wireless
sensor networks have led to many new protocols specifically designed for sensor
networks where they face great challenges. In this paper, we present a survey of the
challenges for Routing in WSNs. We first introduce Wireless Sensor Networks then
outline the challenges for routing in WSNs, in the end we briefly discuss on energy
consumption as it’s the focus of many researchers.
Keyword: Wireless Sensor Network,routing challenges, Energy consumption.
1. Introduction To Wsn
Wireless Sensor Networks WSNs is a popular research area that has taken on
considerable importance in recent years. Because of their convenience, low installation
costs, high mobility, simple deployment and no cabling, WSN has many benefits when
compared to wired networks. WSNs are the technology used in smart infrastructure; for
example, applications for automation systems, development and process control [1][2]. A
large number of these disposable sensors can be networked in many applications that
require unattended operations. A Wireless Sensor Network (WSN) contain hundreds or
thousands of these sensor nodes. These sensors have the ability to communicate either
among each other or directly to an external base-station (BS). [3] Figure 1 shows a
diagram of WSN.
Wireless Sensor Network (WSN) is the set of various sensor nodes deployed inanarea to
track parameters of environmental and physical conditions such as temperature, sound,
object movement, light etc. There is also sink node in a wireless sensor network which is
also known as base station. Military applications motivate the development of the
wireless sensor networks.

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Figure 1. wireless sensor networks
The Wireless Sensor Network sensor nodes capture information from the atmosphere
and then relay it to a base station. [4] Information sent to the base station by all the senor
nodes in the network is gathered and this collected information is sent to the user via the
internet. The base station is generally more resource-potential than the sensor nodes. The
sensor node is Low-Equipped. [5]
The area covered by Wireless sensor nodes is called region of interest (ROI) where in
figure 1 it was label as sensor field. There must be at least one base station for every
region of interest as in Figure 1. Sensor nodes communicate with each other to send data
to base station, this communication can be direct transmission or multi hop. [6]
2. Routing ChallengesInWsn
In this section we discussed on the challenges that influence routing in WSN. [7][8][9] Some
of these challenging issues in wireless sensor network are as follows:
a) Energy consumption
Sensor nodes have limited energy capacity in wireless sensor network. Energy
consumption in the wireless sensor network depends on various operations performed
by sensor nodes, such as data receiving and transmission. The development and design
of hardware and software, routing protocol, and architecture used in sensor networks
also affects energy constraint in the sensor network.[10] sensor nodes can use up their
limited supply of energy performing computations and transmitting information in a
wireless environment. As such, energy conserving forms of communication and
computationare essential. Sensor node lifetime shows a strongdependence onthe battery
lifetime [1] In a multi hop WSN, each node plays a dual role as data sender and data
router. The malfunctioning of some sensor nodes due to power failure can cause
significant topologicalchanges and might require reroutingofpackets and reorganization
of the network.

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b) Nodes Deployment
Wireless sensor network consists of several nodes deployed either randomly or
manually inside an area. Deployment of sensor nodes requires a handling of topology
very carefully. This deployment of nodes is either deterministic or self-organizing.
Sensor network topology is prone to frequent changes after deployment. In dynamic
wireless sensor network some additional sensor nodes can be added to the network at
any time to replace the faulted node or due to any change in the task dynamic. Addition
of new nodes needs reorganization of the network very carefully.[11]
Node deployment in WSNs is application dependent and affects the performance of the
routing protocol. The deployment can be either deterministic or randomized. In
deterministic deployment, the sensors are manually placed and data is routed through
pre-determined paths. However, in random node deployment, the sensor nodes are
scattered randomly creating an infrastructure in an ad hoc manner. If the resultant
distribution of nodes is not uniform, optimal clustering becomes necessary to allow
connectivity and enable energy efficient network operation. Inter-sensor communication
is normally within short transmission ranges due to energy and bandwidth limitations.
Therefore, it is most likely that a route will consist of multiple wireless hops. [6]
c) Production Cost:
Since the sensor networks consist of large number of nodes and the cost ofa single node
is very important to justify the cost of overall network. Sensor nodes with advanced
features are very costly. As a result, cost of each sensor node has kept being low.
Wireless sensor network also consists of some additional components so keeping the
cost low is a challenging task.
d) Failure Tolerance
Sensor nodes fail due to some hardware problems or physical damage and energy
depletion. Nodes failure in wireless sensor network is higher as compare to wired
network. Protocol used in wireless sensor network should be able to detect the node
failure as soon as possible and should be robust to handle the failure with maintaining
the working of network.
Some sensor nodes may fail or be blocked due to lack of power, physical damage, or
environmental interference. [13] The failure of sensor nodes should not affect the overall
task of the sensor network. If many nodes fail, MAC and routing protocols must
accommodate formation of new links and routes to the data collection base stations. This

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may require actively adjusting transmit powers and signalingrates onthe existing links to
reduce energy consumption, or rerouting packets through regions of the network where
more energy is available. Therefore, multiple levels of redundancy may be needed in a
fault-tolerant sensor network.
e) Scalability
The number of sensor nodes deployed inthe sensingarea may be in the order of hundreds
or thousands, or more. Any routing scheme must be able to work with this huge number
of sensor nodes. In addition, sensor network routing protocols should be scalable enough
to respond to events in the environment. Until an event occurs, most of the sensors can
remain in the sleep state, with data from the few remaining sensors providing a coarse
quality.
The deployment of sensor nodes is dependent on the nature of the application. Sensor
node consumption varies with respect to the demand of the application; therefore, the
number of sensor nodes can be hundreds, thousand or still more. To handle network
scalability, routing algorithm should have the capability to cope with scalable network.
[12]
f) Hardware Constraints
Generally, a sensor node has sensing unit, power unit, processing unit and transmission
unit. In some application for extra functionality there is requirement of some extra
hardware components which may increase the cost ofdeployment, energyconsumption
and size of sensor node.
g) Security
Security is one of the important issues in WSNs [14]. WSNs operate on remote location
and remains unattended which increase their chances of being exposed to malicious
intrusion and attacks. All WSNs must be protected from unauthorized access to data.
There are some fundamental security requirements to be meet by WSNs like: Data
Authentication, Data confidentiality, Data integrity, Availability and Redundancy. [15]
Maintaining the security ofdata sensed by sensor nodes is another challenge in wireless
sensor network. Data maybe captured during the transmission from sensor node to base
station.
3. Summary

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Out of all the routing challenges listed and discuss in the above section, much
researchers such as [16] [17] [18.][19] [20] focuses on energy consumption. Energy must be
conserved to increase the lifespan of the sensor nodes. Energy is required by the sensor
node to sense, collect, communicate and process data. Batteries when depleted can be
replaced or recharged. The most important task in WSNs is to design and implement
various energy efficient hardware and software protocols to manage limited battery life
efficiently.
Since In a wireless sensor network, sensor nodes are energy constrained, so if all the
sensors nodes transmit their sensed data directly to the base station then it consumes a
lot of energy of sensor nodes and decreases the network lifetime. In order to maximize
the lifetime of wireless sensor networks different architectures are used. These
architectures of WSN or types of wireless sensor networks help in maximizing the
lifetime of WSN.
4. Conclusion
Routing in sensor networks is not a new area of research, but with rapidly growing set of
research results. In this paper, we give a survey of challenges for routing WSNs. Those
challenges affect the lifetime of the sensor network, and can also compromise security
and data delivery. We highlighted those challenges in this paper because by identifying
and resolving those challenges quickly we can be able to have an effective routing and
data delivery in WSNs.
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