EVENT DRIVEN ROUTING PROTOCOLS FOR WIRELESS SENSOR NETWORK- A SURVEY

International Journal on Computational Sciences & Applications (IJCSA) Vol.3, No.2, April 2013
DOI:10.5121/ijcsa.2013.3201 1
EVENT DRIVEN ROUTING PROTOCOLS FOR
WIRELESS SENSOR NETWORK- A SURVEY
S Taruna1
, Megha R.Tiwari2
and Sakshi Shringi3
1
Computer Science Dept., Banasthali Vidyapith Jaipur, India
staruna71@yahoo.com
2
Information Technology Dept., Banasthali Vidyapith Jaipur, India
megha.ramendra@gmail.com
3
Information Technology Dept., Banasthali Vidyapith Jaipur, India
sakshi.shringi@gmail.com
Abstract
Advances in embedded systems have resulted in the development of wireless sensor networks, which not
only provide unique opportunities for monitoring but also controlling homes, cities and the environments.
Recent advancements in wireless sensor network have resulted into many new protocols some of them are
specifically designed for sensor network for detecting the event and routing the event related information to
the base station in efficient manner. This paper surveys recent event driven routing protocols for wireless
sensor network. We have compared various event driven routing protocols using different parameters like
Sink Centric, Node Centric, Reliability, Congestion control, Energy Efficiency, Loss reliability and loss
recovery. We have also described LEACH and MECN protocols but as they are not e
KEYWORDS
Embedded, wireless sensor network, routing, event, detection
1. INTRODUCTION
Wireless Sensor Network (WSN) is a network consisting of large numbers of wireless sensor
nodes which collect the information from their surrounding environment and send the sensed data
to Base Station (BS) or sink node. Routing is a process of finding a path or route between source
and destination for data transmission. The WSNs use the network layer to implement the routing
of the incoming data. Therefore, routing protocol is one of the important factors in designing the
communication stack. Routing protocols, designed for sensor networks, must have high
reliability. Sensor nodes have limited energy supply and recharging sensor nodes is nearly
impossible due to their nature of deployment. Therefore, saving energy is an important design
aspect in Wireless sensor networks. While, the objective of traditional networks is to have high
quality of service (QoS), sensor network protocols must also focus on power conservation in
order to maximize the network lifetime. There are many protocols for wireless sensor network,
many of them are Event driven routing protocols, i.e. in this transmission of data is triggered
when an event occur.
In this paper we will discuss about Event Driven Routing protocols for wireless sensor network.
The main objective of Event Driven Routing protocol is the event detection and event
transmission in a fast and accurate manner. In this, each of the sensor node are capable of
detecting different events such as fire detection, enemy detection in battle field, etc., and each
node sends the detected events to the sink or base station as shown in Figure.1. The most
important benefit of Event Driven Routing Protocol is to detect the events where the human

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beings cannot reach. The tasks of the sensors in the Event Driven Routing protocols are event
detection, event processing and event communication. To perform these three modules
efficiently, routing protocols should satisfy reliability, congestion control and energy efficiency
[1]. The reliability is concerned with how much information is necessary to ensure the occurrence
of event in Event Driven Routing Protocols. Congestion control deals with reducing traffic in the
network. The application of Event driven routing protocols are used in military applications,
environmental applications, Health application, home application etc [3, 4].
Figure 1. Event Driven Routing Scenario
The rest of this paper is organized as follows. In Section 2, we discuss routing challenges and
design issues in WSNs. In section 3 we discuss related work, in section 4 we describe event
driven routing protocols and conclusion is presented in section 5.
2. ROUTING CHALLENGES AND DESIGN ISSUES
There are innumerable applications of WSNs, along with these; networks have several
constraints, e.g., limited power supply, limited bandwidth and limited computing power of the
wireless links. One of the main design objectives of WSNs is to carry out data communication
efficiently while trying to enhance the lifetime of the network. In the following, we re presenting
some of the routing challenges and design issues that affects routing process in WSNs.
2.1. Node deployment
The deployment of nodes in WSNs is application dependent and it can affect the performance of
the routing protocol. The deployment can be either deterministic or randomized. If the
distribution of nodes is non-uniform, then optimal clustering becomes necessary to have
connectivity with energy efficient network operation. Inter-sensor communication is performed
normally within transmission ranges which are short due to energy and bandwidth constraints.
Therefore, the route will consist of multiple wireless hops.
2.2. Energy consumption without losing accuracy
Due to limited supply of energy, sensor network usually use all their energy in performing
computations and transmitting information in a wireless environment. Therefore, energy-
conservation is essential as the sensor nodes are battery driven.

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2.4 Data Reporting Model
The sensing and reporting of event in WSNs is totally dependent on the application. Data
reporting can be time-driven (continuous), event-driven, query-driven or hybrid. The time-driven
delivery model is suitable for applications that work well for periodic data monitoring. In event-
driven and query-driven models, sensor nodes react immediately when there are sudden changes
in the value of a sensed attribute. These are well suited for time critical applications.
2.4. Node/Link Heterogeneity
In many studies, sensor nodes used are assumed to be homogeneous, i.e., having equal capacity
in terms of computation, power and communication etc. However, depending on the applications
a sensor node can have different roles. The heterogeneous set of sensors arises many technical
issues related to data routing. For example, some applications may require diverse sensors for
monitoring the temperature, pressure and humidity of the environment, motion detection via
acoustic signatures. These sensors can be either independently deployed or the different
functionalities can be embedded in the same sensor nodes.
2.5. Fault Tolerance
Sensor nodes may fail due to limited power supply, physical damage, or environmental
interference. The failure of sensor nodes should not hamper the task of the sensor network. If
large number of nodes fails, Media Access Control (MAC) and routing protocols must help in the
formation of new links and routes to the base stations. This may require adjustment in
transmitting powers and signalling rates on the existing links in order to reduce energy
consumption, or re-routing the data packets through regions of the network where availability of
energy is more. Therefore, the levels of redundancy is multiple in a fault-tolerant sensor network.
2.6. Scalability
Any number of sensor nodes can be deployed in the sensing area and they can be in the order of
hundreds or thousands, or more. The sensor network routing protocols should have scalability to
respond to events in the environment.
2.7. Network Dynamics
Mostly it is assumed by the network architectures that sensor nodes are stationary. In many
applications mobility of both BS’s and sensor nodes are required. The route stability becomes an
important issue, in order to route messages from or to moving nodes in addition to energy,
bandwidth etc. The sensed phenomenon can be either dynamic or static which totally depends on
the application, Dynamic events in many applications requires p reporting periodically and
consequently generate traffic to be routed to the BS.
2.8. Transmission Media
The network architectures assume that sensor nodes are stationary. The mobility of both base
stations and sensor nodes is necessary in many applications. The stability of the route becomes an
important issue, in order to route messages from or to moving nodes in addition to energy,
bandwidth etc. The sensed phenomenon can be either dynamic or static which totally depends on
the application, Dynamic events in many applications requires p reporting periodically and as a
result generate significant traffic to be routed to the BS.

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2.9. Connectivity
Sensor nodes are deployed in high density which prevents them from being completely isolated
from each other. The network topology of wireless sensor network can be variable and the
network size can shrink due to sensor node failures. The connectivity between the sensor nodes
depends on the, possibly random distribution of nodes.
2.10. Coverage
In WSNs, each sensor node has a certain view of the environment. A view of the environment by
the sensors are limited both in sensing range and in accuracy; due to the small sensing range it
can only cover a limited physical area of the environment. Hence, area coverage is an important
design aspect in WSNs.
2.11. Data Aggregation
The sensor nodes may generate redundant data. Data aggregation is the process of collection of
data from different sources according to a certain aggregation function. This technique has been
used to gain energy efficiency and optimization in data transfer. Signal processing can also be
used for data aggregation.
2.12. Quality of Service
In time critical applications, data should be delivered within a certain period of time; otherwise
the data will be useless. Therefore bounded latency for data delivery is an important condition for
time-constrained applications. In many applications, conservation of energy, which is directly
related to network lifetime, is considered more important than the quality of data sent. As the
energy gets depleted, the network may be required to reduce the quality of the results in order to
reduce the energy dissipation in the nodes and hence enhance the total network lifetime.
3. RELATED WORK
The growing interest in wireless sensor networks and the continuous growth of new techniques
inspired some previous effort for surveying the characteristics, applications and communication
protocols .In this subsection we highlight one of the basic protocol for the WSNs i.e. Low
Energy Adaptive Clustering Hierarchy (LEACH) which is a Time Division Multiple Access
(TDMA)-based protocol which is combined with clustering and a simple routing protocol
in wireless sensor networks (WSNs). The goal of LEACH is to lower down the energy
consumption required for the creation and maintenance of clusters in order to improve the life of
a wireless sensor network [3].
LEACH is a hierarchical protocol in which nodes mostly transmit their data to cluster heads, and
the cluster heads then collect and compress the data and send it to the base station. Every node
uses an algorithm at each round to select the cluster head each round. LEACH assumes that node
has energy powerful enough to reach the base station directly or the nearest cluster head, but that
using this transmission energy at full power all the time would waste energy.
Nodes that have already been cluster heads cannot become cluster heads again for P number of
rounds, where P is the percentage of cluster heads set by the user. After that, each node has a
1/P probability which is necessary for the node to become a cluster head in every round. At the
end of every round, nodes which are not a cluster heads then selects the cluster head which are
closest to them and joins that cluster itself. The cluster head then prepare a schedule for every
node that is in cluster to transmit its data.

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Minimum Energy Communication Network (MECN) [3] is a location based protocol, which
maintains a minimum energy network for wireless sensor networks by using low power Global
Positioning System (GPS). Although, the protocol is proposed for a mobile network, but it is best
applicable to immobile sensor networks. In MECN, master-site is assumed as the information
sink, which is always the case for sensor networks. MECN is self-reconfiguring in nature and thus
can adapt dynamically to node’s failure or the deployment of new sensors. Between two
successive wake-ups of the nodes, each node can execute the first phase of the algorithm and the
minimum cost links are updated by considering leaving or newly joining nodes. These protocols
are not event driven, therefore we are not including them for the comparison but these protocols
provide the base for event driven routing protocols.
Our work is a dedicated to the study of the Event Driven Routing Protocols, categorizing the
different approaches for data routing. In addition, we are comparing them on different parameters.
4. EVENT DRIVEN ROUTING PROTOCOLS
4.1 Event-to-Sink Reliable Transport (ESRT) Protocol
In [5] sink makes the decision based on information collected from a number of source nodes in
the region where actually the event occurred rather than individual sensor nodes in the network.
ESRT performs the event detection reliably based on reporting frequency f adjusting it under four
network states and conditions. Network States and the actions performed by ESRT are:
• No Congestion, low reliability (NC, LR) - increase f multiplicatively,
• No Congestion, High Reliability (NC, HR) - decrease f conservatively,
• Congestion, High Reliability (C, HR) - decrease f carefully
• Congestion, Low Reliability (C, LR) - decrease f exponentially and
• Optimal Operating Region (OOR) - stay.
Advantages of ESRT: Sink only collects information i.e. Number of source nodes in the event
coverage area and provide various levels of reliability based on network conditions information to
the sink.
The disadvantages of ESRT includes
• ESRT follows central control method which is not an energy efficient method
• The sensor field with multiple event occurring at the same time the adjustment of f for all
the sensor nodes will not results in better performance as the events are independent to
each other and also the event occurring area may not be same [8].
4.2 Loss Tolerant Reliable Event Sensing (LTRES) Protocol
In LTRES, the congestion control based on the node-end source rate adaptation mechanism is
performed. In Node-end Distributed Source Rate Adaptation, the base station calculates the
Event-sensing Fidelity level (ESFE) and reports the event sensing reliability measure to the
Enodes. Based on the information, Enodes then update their source rate to have the congestion
control.
It mainly consists of three stages:
• Stage one: In this stage before any congestion detection each node in Enodes perform
multiplicative increase (MI) operation on source rate adaptation to approach
ESFE=1[5, 6].

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• Stage two: If any local congestion is detected by the sink due to MI operation before
the end of the first stage Enodes enter into stage two. And the congested Enodes
perform available bandwidth detection and provide upstream congestion avoidance
[6].
• Stage three: In Event Driven Routing protocols, if there are no active Enodes, then
stop the node-end source rate adaptation and the Enodes provide best effort service
without any congestion.
Advantages of LTRES include:
• Performs network traffic control which is based on distributed source rate adaptation
and
• Fast and reliable event sensing is performed by the LTRES in comparison of LSR
protocols.
The disadvantage of LTRES is that it is less energy efficient due to source rate adaptation
mechanism.
4.3 Reliable Robust and Real-Time (RRRT) Protocol
In RRRT protocol [7], there are two concepts proposed:
• event-to-action delay bound to meet the application specific deadlines and
• A combined congestion control mechanism which provide the dual purpose of
achieving reliability and conserving energy.
The event-to-action delay bound is based on assumptions such as
• Observed delay-constrained event reliability (DRo): It is the number of packets that is
received by the sink within a certain delay bound in an interval for decision,
• Desired delay-constrained event reliability (DRd): It is the minimum number of
packets which are required for reliable event detection within a certain delay bound and
• Delay-constrained reliability indicator (α): i.e., α= DRo/ DRd. If the observed delay
constrained event reliability is higher than the reliability bound i.e., DRo>DRd then the
event is reliably detected within a specific delay bound [7].
Advantages of RRRT are:
• Reliable event detection based on event-to-action delay bound and
• Improved energy conserving based on reporting frequency adjustments.
Disadvantage of RRRT is Congestion detection and control mechanisms lead to extra overhead.
4.4 Simultaneous Multiple Event-to-Sink Reliable Transport (SMESRT) Protocol
SMESRT [8] is a protocol designed to achieve simultaneous multiple reliable event detection
information with a payload control component that works as a dual purpose of less traffic at the
sink and conserving energy. In a WSN, the sensor nodes that detect the event generate an event
ID, form a cluster and then the event ID can be distributed using in-network data aggregation or
cluster based event identification method or dynamically random event ID assignment method
can be used. To balance the energy in the network the CH role can be rotated among all the
sensor nodes [9]. With SMESRT the sensor nodes detects the event sends the event packets to CH
at a particular reporting frequency for that particular period or duration. The CH then informs the
base station about the network condition. The SMESRT performs the payload control at the
cluster heads (CHs). Advantages of SMESRT include:

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• payload control at the CHs provide less traffic and
• SMESRT can assign different reporting frequency for different events.
Disadvantage of SMESRT is that the assignment of different reporting frequency results into the
extra overhead.
4.5 Congestion and Delay Aware Routing (CODAR) Protocol
The main goal of CODAR is to improve the reliability and the timeliness of the data transmission
by critical nodes by using congestion avoidance and mitigation [10, 11]. The CODAR protocol
classifies the sensor nodes into two categories:
• critical nodes: The nodes closer to the event
• Regular nodes: When there is no event sensing occurs the critical nodes become regular
nodes.
The CODAR performs two mechanisms which are congestion avoidance and end-to-end delivery
delay management.
• Congestion avoidance: Each node in the region where event occurred broadcasts its
location and Relative Success Rate (RSR) value using control packets over a fixed
interval [10]. The RSR helps to avoid congestion by selecting lightly congested nodes.
• End-to-end delivery data management: In the CODAR, each critical node transmits
their critical data packet with the deadline to the sink with a header. All the node in-
between check this header field before transmitting the packet and if the intermediate
node has end-to-end delay that cannot meet the deadline of the then the intermediate node
drops the packets.
Advantages of CODAR are:
• CODAR delivers high amount critical data within specified amount of delays
• CODAR has a potential to reduce the congestion by avoiding congested nodes during
selection of route and also by dropping packets [10].
Disadvantages of CODAR include:
• not suitable for large number of critical nodes and
• Less energy efficient.
4.6 Delay Sensitive Transport (DST) Protocol
The main goal of the DST protocol is to timely and reliably transport event related information
from the sensor field to the sink with minimum energy loss and no congestion [12]. The DST uses
a Time Critical Event First (TCEF) scheduling at the base station to achieve the application
specific delay bounds. The DST mainly involves two methods:
• Congestion control Detection mechanism: In this for any sensor node whose buffer
overflows due to congestion, informs the sink of the congestion condition by a
Congestion Notification (CN) bit in the event packet header [12]
• Real-time event transport mechanism: Real-time event detection is performed under
event-to-sink delay bound by the DST. The main components of event -to-sink delay
bound are event transport delay and event processing delay [7, 12].

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According to DSRT, for having reliable and time bound event detection the event-to-sink delay
bound should be greater than or equal to the sum of both event processing and event transport
delay. To meet this objective the sink node performs TCEF scheduling policy at the base station.
The TCEF uses the earliest deadline first service and on each sensor node, which is an optimal
scheduling policy when the real-time deadlines of the system is considered [13]. Advantage of
DST is congestion detection and control. The disadvantage of DST is that there is overhead in
reporting frequency rate adjustment mechanism.
4.7 Optimized Energy-Delay Sub-network Routing (OEDSR) Protocol
In OEDSR, the nodes are either in idle or sleep state, but once an event is detected, the nodes
which are near the event become active and start forming a sub-networks and this inactive
network into a sub-network saves energy because only some of the nodes in the network are
active in response to an event [14]. The active nodes itself forms a cluster and choose Cluster
Heads (CHs) among themselves. The packets from CHs are sent to the base station through relay
nodes. The active nodes sends the HELLO message to other neighbor nodes which consists of
attributes such as the active node ID, energy availability of the node, and the sensed attribute.
Based on this information the active nodes in the network forms cluster in order to have efficient
data aggregation are which helps to reduce the energy loss [15]. In the start a Temporary Head
(TH) is selected based on maximum energy and then TH chooses the CHs based on CH selection
criterion. After the selection of CHs the TH sends a CH SELECT packet to all active nodes in the
network and TH becomes a regular node. When nodes receives a beacon frame from the CHs,
then nodes measures the Received Signal Strength Indicator (RSSI) for that particular beacon
frame and also strength of each signal, based on these values the node joins into a particular
cluster.
Advantages of OEDSR are:
• cluster formation leads to less energy loss in terms of consumption
• Sub-networks helps in saving energy because only a portion of the network is active.
The disadvantage of OEDSR is that, when the number of packets is transmitted between the
sensor nodes, THs and CHs this may leads to delay.
4.8 Real-Time and Reliable Transport (RT) 2 Protocol
The main goal of the (RT)2 protocol is to have reliable and collaborative transportation of event
features from the sensor region to the sink or base station with minimum energy loss and to have
timeliness in the reaction to sensor information with the right action [16]. The (RT)2 protocol
simultaneously provides real-time communication and various reliability requirements which
helps in less energy consumption. There are two nodes are used by this protocol, the sensor nodes
and actor nodes.
When the sensor nodes detect an event they transmit the sensed information to the actor nodes in
the network. The actor nodes then communicate with each other to reach to a decision and then
send the event packet to the base station by other actor nodes. The (RT)2 protocol uses the event-
to-action delay bound which is equal to the sum of the event transport delay, event processing
delay, and action delay [7, 16]. The (RT) 2 protocol working is based on two states which are:
• Start-Up state: In this state the sender node transport a probe packet to the receiver in
order to have available transmission rates.
• Steady State: It has four sub states namely increase, decrease, probe and hold. In the
increase state the sender node increases the transmission rate according to the feedback

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received from the sink. In the decrease state the sender node decreases its transmission
rate according to the feedback from the sink. The hold state is reached when the required
transmission rate is achieved. In probe state the sender node sends a probe packet to the
base station in to monitor the current transmission rate in the network.
Advantages of (RT)2 are:
• the (RT)2 protocol make changes in the configurations to adapt to the heterogeneous
nature of wireless sensor networks and
• Have timeliness.
The Disadvantage of (RT)2 is that the configuration adjustment nature of (RT)2 results into extra
delay.
4.9 Event Reliability Protocol (ERP)
The ERP perform reliable transmission of packets containing event related information while
minimizing redundant packets [17]. The ERP protocol makes use of an implicit acknowledgement
(iACK) mechanism in order to achieve the reliability. The ERP operation is based on a
mechanism called Region-based selective retransmission mechanism in which when the sensor
node sense an event it will then send the detected event information to the next hop node and then
this next hop node store that event packet in its buffer and the packet at the head of its buffer is
transmitted to the next hop. When the node hears that the next hop node is transmitting the packet
that was sent by it, then it is known as implicit acknowledgement for notifying that the packet is
forwarded successfully [17]. And the node then erases the entry of the packet from the queue end
and the next packet in the queue is processed. The region-based selective retransmission makes
use of the source ID, source location and event’s time at a source of a particular packet which is
to be retransmitted. The distance between the nodes is calculated to check whether they are in the
range of one another. If there is another packet for the same event region sends, then that packet
is sent to the sink else s the first packet is sent again until a packet from the same event region is
reached to the node’s queue.
Advantages of ERP are:
• Reliable event transmission and
• ERP minimize redundant transmission of data packets.
The main disadvantage of ERP is that it is less energy efficient.
4.10 COLLaborative Event deteCtion and Tracking (COLLECT) protocol
The COLLECT includes three procedures:
• In vicinity triangulation procedure, the same kind of sensor constructs the respective
attribute region, named logical triangle in order to accurately identify the event region
[18].
• In event determination procedure, a sensor node finds the existence of the event locally
according to its available sensor data and received messages from the different kinds of
sensors which are under its logical triangles.
• In border selection procedure, selection the border sensors for the event boundary are
performed [18].
The COLLECT understand the work of sensors by determining the status of the sensor which
includes ordinary, alert, and urgent. A sensor is called ordinary node when it does not sense any

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event. An alert sensor is one which is able to sense any kind of event attribute. A sensor is urgent
node if the event occurs in its sensing area. An ordinary node when detects an event it becomes an
alert node and send it then sends an ATR packet to its neighboring nodes, the packet consists of
the ID of the sensor node, its location, the attribute it detected, and the timestamp when it first
detected the event. Advantages of COLLECT are:
• COLLECT is a fully distributed scheme protocol
• In COLLECT, sensor promptly detects and tracks the event.
The disadvantage of COLLECT, that it is not cost-effective.
4.11 Reliable Energy Aware Routing (REAR) Protocol
In REAR protocol [19] enables each sensor node to confirm success of data transmission to other
sensor nodes by using the DATA-ACK oriented packet transmission. The base station sends the
ACK packet to other sensor nodes which indicates that the event packet is successfully received.
If the sensor node receives the ACK packet within the timeout, it then transmit new sensing event
packet. If ACK does not receive within the time bound then it considers it as error in the
transmission and it assumes that the event packet is lost. If data transmission to the next hop fails
the node sends an error packet to the source node. The source node receiving the error message
retransmits the event packet with a second path in order to have the reliability of data
transmission [19]. The REAR includes the components such as sender, receiver, receiver event
handler, queue manager, routing manager, and REAR checker and delay estimator. Advantage of
REAR is that it provides efficient routing. The Disadvantage with REAR is the overhead due to
the use of queues and estimators.
4.12 Efficient Event Detection Protocol (EEDP)
The goal of EEDP is to have fast transmission of the event packet from the node which make the
decision to the base station or sink node with reduced traffic. In this protocol the sensor nodes
near to the event region senses the event and makes their own decision based on Simple Decision
Rule (SDR) that is whether the event has occurred or not and makes further accurate decision
based on Composite Decision Rule (CDR) [20]. The reliability of the event is achieved by using a
method called dynamic multi-copy scheme.
EEDP is based on two procedures:
• Primary Detection Procedure (PDP): In PDP the event decision is made accurately
which is based on SDR and CDR.
• Emergency Routing Procedure (ERP): In ERP the event packet is transmitted to the
sink by using greedy approach and for achieving reliability simple dynamic multi-copy
scheme is used.
Advantages of EEDP are:
• Accurate event detection
• No significant amount of data is send to the sink or base station.
The disadvantage with EEDP is that it is less reliable because only one decision node sends the
event information to the sink.

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4.13 Stop-and Wait-Implicit Acknowledgement (SWIA) Protocol
The SWIA protocol restricts the sensor node to transmit the next packet before it received an
ACK packet for the previous packet sent. The SWIA protocol uses the implicit acknowledgement
[21]. The iACK mechanism uses the broadcast nature of wireless sensor network. In iACK
mechanism, the sensor node after transmitting the packet listens to the channel and thus reduces
network traffic.
Advantages of SWIA are:
• no additional packet overhead
• Reduced traffic by avoiding those event packet transmissions which are unnecessary.
Disadvantage of SWIA is the use of iACK mechanism results into some delay in the network
performance.
4.14 Energy Efficient-Low Latency Express Routing Protocol (EELLER)
The EELLER protocol falls under the category of hierarchical routing protocol which is based on
clustering in order to minimize the number of hops required for data reporting as well as
achieving high energy efficiency [22]. When the event is detected then detected data is forwarded
hop-by-hop via cluster heads. The EELLER makes use of hierarchical routing to have energy-
efficient routing in an event driven wireless sensor networks. In hierarchical routing, the nodes
having high energy are used to send the information and the low energy nodes are used only to
sense the event.
The EELLER consists of two phases:
• Constructing expressways: In the first phase, the first hop and the second hop are
selected based on the link factor, where link factor is equal to the ratio of the energy of
the node to the distance to the sink or base station.
• Cluster formation and data communication: In the second phase of EELLER, it results
into a better data transmission after data aggregation and removing data redundancy by
the cluster heads.
Advantages of EELLER are:
• EELLER is an energy efficient event driven routing protocol
• Data aggregation results into more event accuracy.
Disadvantage of EELLER is that it is less reliable.
4.15 Information Quality Aware Routing (IQAR) Protocol
IQAR consider the information content of event during data aggregation and forwarding [23]
unlike other data aggregation schemes. The IQAR protocol has adopted tree based approach and
its aim is to detect event in a sensor network. The quality of the information is concerned with the
accuracy of the event information. In this protocol, each sensor nodes detects and collects data
about an event independently and makes a per-sample binary decision, which is used to check if
the event has happened or not. If an event happened the result of per-sample binary decision will
be 1 else it is 0.

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4.16 TEEN and APTEEN
Threshold sensitive Energy Efficient sensor Network protocol (TEEN) [24] is one of the
hierarchical protocols. It is designed to show reaction for changes in the sensed attributes which
are sudden such as temperature. TEEN pursue a hierarchical approach along with the use of data-
centric mechanism. The sensor network architecture is based on a hierarchical grouping in which
nodes which are closer leads to the formation of clusters and this process continues to the second
level until it reaches the base station (sink). The model is shown in Fig. 8, which is redrawn from
[24].
Figure 2. Hierarchical clustering in TEEN and APTEEN
When the formation of clusters is complete, the selected cluster head broadcasts two threshold
values to other nodes of the cluster. These two thresholds are hard and soft thresholds for sensed
attributes.
Hard threshold is the minimum value of an event to notify a sensor node so as to turn on its
transmitter and transmit the event data to the cluster head. Thus, we can say that the hard
threshold allows the sensor nodes to transmit the event data only when the sensed value is inside
the range of interest, as a result, number of transmissions significantly reduced. When a sensor
node senses a value which is at or beyond the hard threshold value, it starts transmitting data only
when there is a change in the value of that attributes and also the change is to be equal to or
greater than the soft threshold. Thus, soft threshold, reduce the number of transmissions further if
there is small or no change in the sensed attribute value. We can make changes to both threshold
values in order to control the number of transmissions of the packets. However, TEEN is not
good for those applications that requires periodic reports because the user may not get any data l
if the thresholds are cannot be reached.
The Adaptive Threshold sensitive Energy Efficient sensor Network protocol (APTEEN) [26] is
continuation of TEEN protocol. Its objective is the capturing of the periodic data and
responsiveness to time critical events. Its architecture is same as of TEEN protocol. When the
sink node creates clusters, the selected cluster heads broadcast the event value, the threshold
values, along with the transmission schedule to all the sensor nodes in the network. Data
aggregation is performed by the cluster head in order to save energy. APTEEN uses three query
types:
• Historical: which analyse past event values;
• One-time: which takes snapshot view of the network into consideration
• Persistent: which monitors an event for a particular period of time

13
Simulation result of TEEN and APTEEN has shown these protocols are better than Low Energy
Adaptive Clustering Hierarchy (LEACH) protocol [25].TEEN provides the best performance by
the decrement in the number of transmissions. The main drawbacks are overhead and complexity
in formation of the clusters in multiple levels, implementation of threshold-based functions and
handling attribute-based naming of queries.
4.17 Rumor routing
Rumor routing [28] is a variation of Directed Diffusion. It is mainly used for the contexts in
which geographic routing criteria cannot be used. Directed Diffusion method flood the query in
whole network when there is no geographic criterion to diffusing the tasks. Another approach is
to flood the network if number of events is small and number of queries is large. Rumor routing
appears in between event flooding and query flooding. The objective is to route the queries to
those nodes that have detected a particular event in place of flooding the entire network to collect
information about the occurring events. To flood the network throughout with the events, the
rumor routing algorithm employs agents which are long-lived packets. When any sensor node
detects an event, it adds that event information into its local table and creates an agent. Agents
travel the whole network in order to transmit information about local events to nodes which are
far away. When a node generates a query for a particular event, the nodes that have the awareness
of the route, can respond to the query immediately by referring to its event table. Hence, the cost
of flooding the whole network is minimized. In Rumor routing only one path is maintained
between source and destination.
Simulation result shows that in rumor routing, energy saving capacity over event flooding and
handling of node’s failure is significant. However, rumor routing is efficient in performance only
when the numbers of events are less. For large number of events, the cost of maintenance of
agents and event tables for each node may not be reduced if there is less interest from the sink.
Another problem is to handle tuning of the overhead using adjusting parameters which is used in
the algorithm.
4.18 Sensor protocols for information via negotiation (SPIN) protocol
SPIN [27] is a protocol which categorised under data-centric routing mechanism. The aim of
SPIN is to name the data by the use of high-level descriptors or by meta-data. The metadata are
exchanged between sensors before transmission through data advertisement mechanism, which is
an important feature of SPIN. Each node when receives new data, advertises it to its neighbors
along with neighbors which are interested, i.e. nodes that do not have the data can retrieve the
data by sending a request message. The meta-data negotiation of SPIN solves the problems of
flooding which includes redundant information, sensing areas overlapping and resource blindness
thus results into a lot of energy efficiency.
SPIN does not contain standard meta-data format and it is assumed to be dependent on
application, e.g. using an application level framing. There are three messages which are defined
in SPIN for the exchange of data between nodes. These are: ADV message which makes a sensor
node to advertise particular meta-data information, REQ message which request for the event data
and DATA message carry the actual event information.
The important advantage of SPIN is that it has localized topological changes since each node only
knows about its single-hop neighbors. The data advertisement mechanism in SPIN does not allow
the delivery of data. Suppose, if the nodes which are interested in the event data are not near
source sensor node and the nodes between source and destination are not at all interested in that
information, then destination will not receive that data at all. Therefore, SPIN is not a good

14
protocol for applications such as intrusion detection, which requires reliable delivery of data
packets periodically.
5. CONCLUSION
Routing in wireless sensor networks has gained a lot of attention in the recent years and results
into many challenges compared to traditional data routing in wired networks. In this paper, we
have summarized recent researches on event driven routing in sensor networks.Each of these
protocols performs the event detection and transmission based on various approaches in wireless
sensor network. In Table 1, we are summarizing the event driven routing protocols covered in this
survey.
Table 1. Comparative table of Event Driven Routing Protocols
ACKNOWLEDGEMENT
We take the opportunity to express our gratitude and thanks toward all the people who have been
a source of guidance and inspiration to us during the course of this paper.
Last but not the least we would like to thank all our friends, for giving useful suggestion and ideas
for improving our performance.
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Authors
S.Taruna is an active researcher in the field of communication and mobile network,
currently working as Assistant Professor in Department of Computer Science at
Banasthali University (Rajasthan), India. She has done M.Sc from Rajasthan Uni. and
PhD in Computer Science from Banasthali University (Rajasthan), India. She has
presented many papers in National and International Conferences, published 7 papers in
various Journals and reviewer of various journals and conferences.
Megha R.Tiwari received her B.Tech degree in Information Technology from Integral
University, Lucknow, Uttar Pradesh in 2011. Currently she is pursuing her M.Tech
degree in Information Technology from Banasthali University, Rajasthan. Her research
interests include computer networks, wireless sensor and ad hoc networks,
virtualization.
Sakshi Shringi received B.TECH degree in Information Technology from Rajasthan
Technical University, Kota in 2011. She is pursuing her M.TECH degree in Information
Technology from Banasthali University (Rajasthan). She has presented many papers in
National and International Conferences, published 3 papers in various Journals. Her
research interest includes computer networks, wireless sensor and ad-hoc networks and
virtualization.

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