A survey on energy aware routing issues and cross layering in mane ts

1. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30 – 31, December 2014, Ernakulam, India
47
A SURVEY ON ENERGY AWARE ROUTING ISSUES AND
CROSS LAYERING IN MANETs
Remya K1
, Sangeetha C P2
, C D Suriyakala3
1, 2
Dept of ECE, TIST, Cochin, India
3
Dept of ECE, SNGCE, Cochin, India
ABSTRACT
In the next generation of wireless communication systems, there will be a great need for the rapid deployment of
independent mobile users. Such network scenarios cannot depend on centralized and organized connectivity. In such
applications Mobile ad hoc networks (MANETs) play an important role. MANETs is a collection of wireless mobile nodes
that communicate with one another without any fixed networking infrastructure. Since the nodes in this network are highly
dynamic, energy conservation become very critical in mobile adhoc network. The nodes in this network are battery powered
and hence have limited computational power. So these nodes must conserve energy during routing to prolong their usefulness
and increase network lifetime. To account for this problem, many energy efficient protocols have been proposed. But these
energy efficient protocols do not consider the QoS parameters of the network such as throughput, end to end delay, packet
delivery ratio etc. Cross layer architecture will help to improve these performance metrics of the network by allowing
coordination and interaction among the layers. This paper surveys a comprehensive review of energy aware routing using
cross layer approach which can improve the energy efficiency of the network without the degradation of the QoS parameters
of the network.
Keywords: Cross Layer, Energy Aware Routing, Manets, Network Lifetime, Qos Parameters.
1. INTRODUCTION
A mobile ad hoc network (MANET) is a self-configuring infrastructure less network of mobile devices connected by
wireless links. The nodes themselves act as router and forward the information from one node to the other. One of the main
challenges with the ad hoc networks is to develop a routing protocol that can efficiently find routes between the
communicating nodes. Traditional routing protocols cannot be applied to ad hoc networks directly because ad hoc networks
inherently have some special characteristics such as dynamic topologies, bandwidth-constrained, variable capacity links,
and energy-constrained operations compared with traditional networks. The routing protocol must be able to keep up with
the high degree of node mobility even if the network topology changes unpredictably. Since the nodes of an ad hoc network
are usually small and battery powered, energy management is a critical issue during the deployment of these networks. Hence
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2. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
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48
applying power control techniques to these routing protocols have become one of the major research area in wireless
networking. This is because, by using the power control methods we can reduce the energy consumption of the nodes and
thereby the lifetime of the wireless networks can also be increased.
Popular existing routing protocols for MANETs are Dynamic Source Routing (DSR), Destination Sequenced
Distance Vector (DSDV) and Ad hoc On- Demand Distance Vector (AODV). These protocols mainly use the shortest path
method to forward the packet from source to the destination. But the problem with these routing protocols is that they do not
consider the energy consumption of the network. So to account for this problem, many energy efficient routing protocols
have been proposed. The problem of energy efficiency in MANETs can be addressed at different layers and can be reduced
by different methods. Some of the solutions tried to adjust the transmission power of wireless nodes; other proposals tend to
efficiently manage the sleep state for the nodes. There are many proposals which try to define an energy efficient routing
protocol, capable of routing data over the network and of saving the battery power of mobile nodes. However, there is a
tradeoff between energy conservation and perceived Quality of Service (QoS). The conventional method uses the layered
architecture. But this approach is not flexible enough to cope up with the dynamic nature of ad hoc networks. So we use the
cross layer approach to improve the performance characteristics of the network.
Traditional wired network uses protocol architectures that follow the principle of stack layering, implemented
by ISO/OSI model. ISO/OSI model was developed to support all the standardization of the network architecture using
layered model. Initially wireless network also adopts the traditional stack layered architecture from the wired networks. This
Layered architectures is not efficient to cope up with the dynamically changing environment in the wireless-dominated next-
generation communications, with a wide range of Quality of Service (QoS) requirements. To overcome such limitations,
cross layer design has been proposed. Its core idea is to maintain the functionalities associated to the original layers
but to allow coordination, interaction and joint optimization of protocols crossing different layers [1].
To minimize the energy consumption of ad hoc networks and to improve the network performance, there are many
factors that have to be considered. This survey paper mainly considers the methods used in the mac and the network layer.
Section II describes about the routing mechanism and the cross layer architecture. Energy related issues in MAC and network
layer is mentioned in section III and the possible solutions to this problem are described in section IV. Section V concludes
the paper.
2. BACKGROUND INFORMATION
In ad hoc networks, there are different types of routing protocols available. MANET routing protocols could be
generally classified into two main categories based on the routing information update method- proactive and reactive routing
protocols. Proactive protocols constantly study the topology of the network by exchanging topological information
among the network nodes. Therefore, when there is requirement for a path to a destination, such route information is
available instantly. But as the network topology changes too regularly, the cost of maintaining the network might be very
high.eg: DSDV. Reactive protocols continue for establishing route to the destination only when the need arises. They do not
require cyclic transmission of topological information of the network e.g. DSR, AODV. Many of the existing energy aware
protocols have been developed by modifying AODV protocol [7].
The AODV routing protocol provides a dynamic and multi-hop routing topology among the mobile nodes.
Whenever a node needs to send data to another node for which it has no routing information, AODV is used for route
discovery process of that particular destination node. AODV uses three types of messages to discover and maintain route:
Route Requests (RREQs) and Route Replies (RREPs) messages are used for route discovery. Route Errors (RERRs)
messages are used for route maintenance. When a source node needs to communicate with a destination node for which it
does not have a route, it broadcasts an RREQ packet across the network. When an intermediate node receives this packet
which it does not have seen before, it creates a reverse route to the source. Then, it checks the destination address, if the
intermediate node does not have a fresher route to the destination, it increments the hop-count and re-broadcasts the RREQ
packet. Otherwise, it generates a RREP packet and sends it to the source node. When the source receives the RREP packet, it
saves the route and begins data transmission (Fig. 1). When a node detects a link break in an active route, it sends a RERR
packet to notify the other nodes about this problem. An active route is used to forward data packets[3].

3. Proceedings of the International
In the conventional AODV routing mechanism, a node broadcasts or floods RREQ message to its neighbors when
it needs to communicate with a destination node [4]. If
expires after some time. Therefore, it could not be able to forward the RREP message on the reverse path. Hence,
the source node would have to rebroadcast the Route Request (RREQ) message in order to find an optimal path
communicating to the destination node. This may possibly cause congestion in the network, reduce the packet delivery
ratio; raise the end to end delay and needless rebroadcasting of RREQ packets. Hence to provide a solution to this problem,
many energy aware routings were proposed.
Another important factor that is to be considered in ad hoc networks is to improve the QoS parameters of the
network. Even though there are many routing protocols proposed, care should be given so that these network parameters a
not degraded. One of the effective ways to improve the
design, introduces stack wide layer interdependencies to optimize overall network performance. In cross layering, protocols
use the state information flowing throughout the stack to adapt their behavior accordingly [2]. Information can
shared between layers which are nonadjacent unlike in traditional layered architecture.
gains and QoS improvements.
There are different ways in which cross layering can be done [5]. One of the most common architecture used is the
Mobile Man architecture [2]. This reference architecture exploits the advantages of a full cross
satisfying the layer-separation principle.
Fig. 2 shows that some network functions such as energy management, security, and cooperation, are cross
nature. The architecture presents the core component, Network Status, which
network protocols throughout the stack collect. Each protocol can access the Network Status to share its data with other
protocols. This avoids duplicating efforts to collect internal state information and leads to a mor
Hence the QoS parameters can be improved using cross layer approach. Hence we can conclude that cross
been proposed to maintain the functionalities associated to the original layers but to allow coordination,
joint optimization of protocols crossing different layers.
eliminated and the performance is improved by adopting cross layer design in wireless mobile adhoc netw
Conference on Emerging Trends in Engineering and Management (ICETEM14)
30 – 31, December 2014, Ernakulam, India
49
Figure 1: AODV RREQ/RREP Process [3]
In the conventional AODV routing mechanism, a node broadcasts or floods RREQ message to its neighbors when
it needs to communicate with a destination node [4]. If intermediate nodes does not have sufficient battery life, that node
some time. Therefore, it could not be able to forward the RREP message on the reverse path. Hence,
the source node would have to rebroadcast the Route Request (RREQ) message in order to find an optimal path
g to the destination node. This may possibly cause congestion in the network, reduce the packet delivery
ratio; raise the end to end delay and needless rebroadcasting of RREQ packets. Hence to provide a solution to this problem,
re routings were proposed.
Another important factor that is to be considered in ad hoc networks is to improve the QoS parameters of the
network. Even though there are many routing protocols proposed, care should be given so that these network parameters a
not degraded. One of the effective ways to improve these parameters is by using the cross layer approach. A
layer interdependencies to optimize overall network performance. In cross layering, protocols
se the state information flowing throughout the stack to adapt their behavior accordingly [2]. Information can
shared between layers which are nonadjacent unlike in traditional layered architecture. This leads to faster performa
There are different ways in which cross layering can be done [5]. One of the most common architecture used is the
Mobile Man architecture [2]. This reference architecture exploits the advantages of a full cross
2 shows that some network functions such as energy management, security, and cooperation, are cross
core component, Network Status, which functions as a repository for information that
network protocols throughout the stack collect. Each protocol can access the Network Status to share its data with other
protocols. This avoids duplicating efforts to collect internal state information and leads to a mor
Hence the QoS parameters can be improved using cross layer approach. Hence we can conclude that cross
been proposed to maintain the functionalities associated to the original layers but to allow coordination,
joint optimization of protocols crossing different layers. Also the limitations in ISO/OSI, TCP/IP layered protocols are
eliminated and the performance is improved by adopting cross layer design in wireless mobile adhoc netw
Figure 2: Mobile Man architecture [2]
Conference on Emerging Trends in Engineering and Management (ICETEM14)
31, December 2014, Ernakulam, India
In the conventional AODV routing mechanism, a node broadcasts or floods RREQ message to its neighbors when
does not have sufficient battery life, that node
some time. Therefore, it could not be able to forward the RREP message on the reverse path. Hence,
the source node would have to rebroadcast the Route Request (RREQ) message in order to find an optimal path for
g to the destination node. This may possibly cause congestion in the network, reduce the packet delivery
ratio; raise the end to end delay and needless rebroadcasting of RREQ packets. Hence to provide a solution to this problem,
Another important factor that is to be considered in ad hoc networks is to improve the QoS parameters of the
network. Even though there are many routing protocols proposed, care should be given so that these network parameters are
parameters is by using the cross layer approach. A full cross layer
layer interdependencies to optimize overall network performance. In cross layering, protocols
se the state information flowing throughout the stack to adapt their behavior accordingly [2]. Information can be
This leads to faster performance
There are different ways in which cross layering can be done [5]. One of the most common architecture used is the
Mobile Man architecture [2]. This reference architecture exploits the advantages of a full cross-layer design while still
2 shows that some network functions such as energy management, security, and cooperation, are cross-layer by
s a repository for information that
network protocols throughout the stack collect. Each protocol can access the Network Status to share its data with other
protocols. This avoids duplicating efforts to collect internal state information and leads to a more efficient system design.
Hence the QoS parameters can be improved using cross layer approach. Hence we can conclude that cross-layer design has
been proposed to maintain the functionalities associated to the original layers but to allow coordination, interaction and
Also the limitations in ISO/OSI, TCP/IP layered protocols are
eliminated and the performance is improved by adopting cross layer design in wireless mobile adhoc networks [1].

4. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30 – 31, December 2014, Ernakulam, India
50
3. ENERGY RELATED ISSUES IN NETWORK AND MAC LAYERS
Energy management in wireless networks is of paramount importance due to the limited energy availability
in the wireless devices. Since wireless communication consumes a significant amount of energy, it is important to
minimize the energy costs for communication as much as possible by practicing energy aware routing strategies.
Such routing strategies can increase the network lifetime. The problem of energy efficiency in MANETs can be addressed at
different layers and can be reduced by different methods. There are many proposals which try to define an energy efficient
routing protocol, capable of routing data over the network and of saving the battery power of mobile nodes. This paper
mainly focuses the issues in the network layer and the mac layers.
3.1 Issues in network layer
Network layer is mainly involved in packet forwarding which includes routing of information from one node to the
other. There are many existing protocols for ad hoc networks. But the problem with these routing protocols is that they do not
consider the energy of the nodes while routing the packet from source to destination. In the conventional AODV routing
mechanism, a node broadcasts or floods RREQ message to its neighbors when it needs to communicate with a destination
node. If intermediate node does not have sufficient energy, then the node will expire after some time. Therefore, it could
not be able to forward the RREP message on the reverse path. Hence, the source node would have to rebroadcast the
Route Request (RREQ) message in order to find an optimal path for communicating to the destination node. This may
possibly cause congestion in the network which is the major issue we have to consider in the network layer. To address the
above problems, different energy aware routing mechanisms can be used by considering the residual energy of each node.
3.2 Issues in MAC layer
Medium access control (MAC) layer is mainly responsible for scheduling and allocating the wireless channel. MAC
protocols provide a means for the nodes to access the wireless medium efficiently and collision free to the best of their
ability. Major issues in the MAC layer regarding the energy wastage are collision, idle-listening, over-hearing and control
packet overhead. Collision occurs when the transmission packets are corrupted partially or fully. Collision causes
retransmission thus increases the latency and power consumption [9]. Listening to an idle channel for possible traffic is called
idle-listening. In order to conserve energy, most of the energy efficient protocols put their network interface in sleep state
rather than in idle state. Receiving packets which are meant for other nodes is called over-hearing[10-12]. Control packet
overhead occurs when more number of control packets are used. Use of more numbers of control packets not only increase,
the energy consumption but also decrease, the utilization of limited bandwidth. Carrier sensing[13] is another major cause of
energy wastage.
4. SOLUTIONS FOR ENERGY RELATED ISSUES
In order to mitigate the problems regarding the energy awareness of ad hoc networks number of solutions has been
proposed in the literature survey. It has been shown that by the proper selection of nodes by considering the residual energy
of the nodes this problem can be minimized. Survey report of [9-13] gives different methods used in the MAC layer.
References [14-18] consider the different energy efficient routing and [19-22] considers the cross layer approach to improve
the energy efficiency and the QoS parameters of the ad hoc networks.
4.1 MAC layer solutions
The major causes of energy wastage at MAC layer are collision, idle-listening, over-hearing and control packet
overhead. Channel efficiency and channel throughput in any network are affected by packet collisions. Reduction of packet
collisions plays a greater role in Mobile Ad hoc Networks (MANETs).These collision issues introduce a key problem in
MANET networks where researches proposed back-off mechanism to overcome packet collisions. Back-off algorithm is
proposed to reduce collisions that happen when more than one node tries sending data on the channel simultaneously. Paper
[9] has presented different back off algorithms that are used to avoid collisions. The Binary Exponential Back-off (BEB), the
first Back-off algorithm that is deployed in Medium Access Control layer, is used by IEEE 802.11 to avoid collision in
MANETs. BEB algorithm uses a uniform random distribution Back-off values to solve the collision problem. In this paper
authors have proposed Fibonacci Liner Increment Back-Off (FLB) algorithm to achieve an effective value for the
Back-off timer of the nodes before accessing the channel to avoid collision. When a node wants to send a data, it first
senses the medium. If it is busy, the node will wait for a certain period of time (back off time). In this algorithm, Fibonacci
selection of back off value is done. In this paper the author have compared the different existing back off algorithms like

5. Proceedings of the International
Binary Exponential Back-off (BEB), Pessimistic Linear
(PDR), average End-End delay and normalized routing load.
Another major energy wastage in MAC protocols is due to overhearing.
presented an algorithm called Random Cast to minimize the problems caused due to over hearing by the nodes. They have
proposed a new communication mechanism, in which a sender can specify the desired level of overhearing, making a balance
between energy and routing performance. The transmitter is able to specify the desired level of overhearing in its ATIM
hoc Traffic Indication Message) frame and is available to its neighboring nodes during the ATIM
detailed explanation to this method was given. In their protocol, the sender may choose no or unconditional or probability
overhearing which was specified in ATIM frame control. Each node maintains overhearing probability
probability (Pr). ATIM frame consists of frame control, destination address, source address, sequence control
added the subtype field in frame control which helps to
overhearing; 1101 for probability based overhe
overhearing, unconditional overhearing or probability based overhearing for its neighbors and is specified in the ATIM
frame’s sub type field.
In paper [12] they have addressed
protocol named residual energy based rebroadcast and overhearing reduction (RE
control packets and data packets over low energy availability
energy availability of the link. The indication whether to overhear or not has been specified in the subtype field of ad
traffic indication message (ATIM) frame. Probability of overhearing and
determined for setting this field. They have focused to reduce the amount of overhearing and rebroadcast for a
energy consumption in route discovery.
One of the most common methods to save the ener
activity taking place in the network. But most of the protocols rely on periodically switching the wireless interfaces off to
save power. However, there is a tradeoff between energy conservation
for this problem, an algorithm called Slow
This is a novel battery saving mechanism which can saves up to 70% energy compared
IEEE 802.11. This algorithm consists of three sleeping window adaptation phases, each phase employing a different duty
cycle management function. It consists of three phases: slow start, exponential and linear increase of s
(Fig. 3). In each phase, the beacon window is adjusted which eliminates the periodic switching between sleep/wake cycles.
During the first stage, the sleeping window was kept at one beacon period. The next phase is exponential in
window, which doubled the sleeping window every time the wireless interface wakes up unless the wireless node receives
packets and goes back to slow start phase. During this phase of the algorithm, sleeping window grows fast until it re
predetermined threshold value. Finally the linear mode was introduced after the threshold value is surpassed. Hence, by
linearly and exponentially increasing the sleeping window, the energy consumption of the nodes was reduced
Figure 3
4.2 Network layer solutions
To account for energy efficiency of the ad hoc networks, many energy efficient protocols have been proposed.
[14] describes a protocol named Signal strength and Energy
strength and residual battery capacity of nodes into route selection through cross layer approach. This protocol tried to
improve the reliability of route discovery in MANET by using sig
information sharing. They considered the residual energy level of the intermediate routes which helped to protect agains
Conference on Emerging Trends in Engineering and Management (ICETEM14)
30 – 31, December 2014, Ernakulam, India
51
ff (BEB), Pessimistic Linear-Exponential Back-off (PLEB) in terms of packet delivery ratio
End delay and normalized routing load.
major energy wastage in MAC protocols is due to overhearing. Sunho Lim et al.
presented an algorithm called Random Cast to minimize the problems caused due to over hearing by the nodes. They have
proposed a new communication mechanism, in which a sender can specify the desired level of overhearing, making a balance
nd routing performance. The transmitter is able to specify the desired level of overhearing in its ATIM
frame and is available to its neighboring nodes during the ATIM
s method was given. In their protocol, the sender may choose no or unconditional or probability
in ATIM frame control. Each node maintains overhearing probability
onsists of frame control, destination address, source address, sequence control
field in frame control which helps to set the overhearing level. Subtype: 1001 for unconditional
overhearing; 1101 for probability based overhearing; 1110 for no overhearing. This algorithm enabled
overhearing, unconditional overhearing or probability based overhearing for its neighbors and is specified in the ATIM
] they have addressed the problem of unnecessary overhearing and rebroadcast, and have proposed a
protocol named residual energy based rebroadcast and overhearing reduction (RE-ROR). They
control packets and data packets over low energy availability links and have selected the forwarding nodes based on the
energy availability of the link. The indication whether to overhear or not has been specified in the subtype field of ad
traffic indication message (ATIM) frame. Probability of overhearing and rebroadcast based on residual energy (RE) has been
determined for setting this field. They have focused to reduce the amount of overhearing and rebroadcast for a
One of the most common methods to save the energy of nodes is to put them into sleep state when there is no
But most of the protocols rely on periodically switching the wireless interfaces off to
save power. However, there is a tradeoff between energy conservation and perceived Quality of Service (QoS).
for this problem, an algorithm called Slow-sTart Exponential and Linear Algorithm (STELA)
a novel battery saving mechanism which can saves up to 70% energy compared with the algorithms employed by
IEEE 802.11. This algorithm consists of three sleeping window adaptation phases, each phase employing a different duty
cycle management function. It consists of three phases: slow start, exponential and linear increase of s
. In each phase, the beacon window is adjusted which eliminates the periodic switching between sleep/wake cycles.
During the first stage, the sleeping window was kept at one beacon period. The next phase is exponential in
window, which doubled the sleeping window every time the wireless interface wakes up unless the wireless node receives
packets and goes back to slow start phase. During this phase of the algorithm, sleeping window grows fast until it re
predetermined threshold value. Finally the linear mode was introduced after the threshold value is surpassed. Hence, by
linearly and exponentially increasing the sleeping window, the energy consumption of the nodes was reduced
Figure 3: Illustration of STELAs principle [13]
To account for energy efficiency of the ad hoc networks, many energy efficient protocols have been proposed.
Signal strength and Energy Aware routing protocol (SEA-DSR), which considered the signal
strength and residual battery capacity of nodes into route selection through cross layer approach. This protocol tried to
improve the reliability of route discovery in MANET by using signal strength and energy metrics through cross layer
information sharing. They considered the residual energy level of the intermediate routes which helped to protect agains
Conference on Emerging Trends in Engineering and Management (ICETEM14)
31, December 2014, Ernakulam, India
off (PLEB) in terms of packet delivery ratio
Sunho Lim et al. in their paper [10] have
presented an algorithm called Random Cast to minimize the problems caused due to over hearing by the nodes. They have
proposed a new communication mechanism, in which a sender can specify the desired level of overhearing, making a balance
nd routing performance. The transmitter is able to specify the desired level of overhearing in its ATIM (Ad-
frame and is available to its neighboring nodes during the ATIM window. But in [11] more
s method was given. In their protocol, the sender may choose no or unconditional or probability
in ATIM frame control. Each node maintains overhearing probability (Po) and rebroadcast
onsists of frame control, destination address, source address, sequence control etc. They have
Subtype: 1001 for unconditional
1110 for no overhearing. This algorithm enabled the sender to select no
overhearing, unconditional overhearing or probability based overhearing for its neighbors and is specified in the ATIM
the problem of unnecessary overhearing and rebroadcast, and have proposed a
They avoided the transmission of
have selected the forwarding nodes based on the
energy availability of the link. The indication whether to overhear or not has been specified in the subtype field of ad-hoc
rebroadcast based on residual energy (RE) has been
determined for setting this field. They have focused to reduce the amount of overhearing and rebroadcast for achieving
gy of nodes is to put them into sleep state when there is no
But most of the protocols rely on periodically switching the wireless interfaces off to
and perceived Quality of Service (QoS). So to account
sTart Exponential and Linear Algorithm (STELA) was introduced in paper [13].
with the algorithms employed by
IEEE 802.11. This algorithm consists of three sleeping window adaptation phases, each phase employing a different duty
cycle management function. It consists of three phases: slow start, exponential and linear increase of sleeping window
. In each phase, the beacon window is adjusted which eliminates the periodic switching between sleep/wake cycles.
During the first stage, the sleeping window was kept at one beacon period. The next phase is exponential increase of listening
window, which doubled the sleeping window every time the wireless interface wakes up unless the wireless node receives
packets and goes back to slow start phase. During this phase of the algorithm, sleeping window grows fast until it reaches a
predetermined threshold value. Finally the linear mode was introduced after the threshold value is surpassed. Hence, by
linearly and exponentially increasing the sleeping window, the energy consumption of the nodes was reduced
To account for energy efficiency of the ad hoc networks, many energy efficient protocols have been proposed. Paper
DSR), which considered the signal
strength and residual battery capacity of nodes into route selection through cross layer approach. This protocol tried to
nal strength and energy metrics through cross layer
information sharing. They considered the residual energy level of the intermediate routes which helped to protect against

6. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30 – 31, December 2014, Ernakulam, India
52
link breakages due to weak link and energy depletion at the intermediate nodes. In this protocol an extra field called
reliability count (RELCOUNT) was added to the RREQ packet. This field contains reliability count of the path it comes
across. Destination node selects the most reliable route among all the routes based on this value and the hop count value.
In paper [15] a routing algorithm (MEL-AODV) based on remaining energy in each node to increase the network
lifetime and to achieve efficient utilization of node energy was proposed. They designed a new energy cost model to calculate
the cost of the paths. The algorithm selects the path which has minimum cost and maximum energy. The protocol combines
the overall node energy on the link for route selection. Finally they showed that the lower energy nodes on the path are saved
and their lifetimes are also extended. Recently, Reena Singh etal. Have proposed an Energy Efficient AODV (EEAODV)
routing [3], which is an enhancement of the existing AODV protocol. This algorithm used enhanced RREQ and RREP to
handle the process to save the energy in mobile devices. . When the source node sends the RREQ to neighbor nodes, they
sends its energy level REPEL(Reply Energy Level) in response to that RREQ, if path to destination node is available.
If this value is less than the predefined threshold level, then that node may be eliminated from forwarding the packets. Hence
the energy efficiency of the network can be improved.
Maher Heni et al. have proposed a method to reduce the problem of energy consumption by reducing the number of
HELLO messages exchanged [16]. In this protocol they have decreased the number of HELLO messages by increasing the
time between two messages. This solution can provide knowledge about the levels of stored energy of the nodes constituting
the network without affecting the operation of the protocol. After saving this new information, a node chooses the shortest
path that contained enough energy for the correct routing of data packets. In this way the energy consumption of the network
was minimized and also the packet delivery ratio was improved. In [17] Pratik M Zala et al. presented different approaches
of routing protocol that provide the stable path from source to destination which consumed less energy and maximize the
network life time. In this protocol, when sender send the route request to its neighboring nodes, the neighboring nodes
sends route reply which included the RSSI value, battery capacity and SINR value. After that, they compared this value
with the threshold value. If the value (RSSI, SINR, BATTERY CAPACITY) is greater than the threshold, then route
discovery was done on that route. Hence the network life time was improved by this method.
In paper [18], a new protocol called Route Stability and Energy Aware Ad hoc On-demand Distance Vector (RSEA-
AODV) was introduced. RSEA model considered signal strengths and mobility for computing the probability of link failures.
It computes link stability (LS) using signal strength values received from the MAC layer. They have added three new fields
to the RREQ packets namely, Accumulated Path Stability (APS), Accumulated Energy Metric (AEM) and required energy
(REQe). The node checks whether its residual energy will meet the required energy REQe specified in the RREQ packet. If
these conditions are satisfied, then node makes a reverse route entry in the Routing Table (RT). Then it calculates LS. So by
this method, the authors have shown that this algorithm helps to perform better in frequently changing networks. All these are
some of the approaches that is used to improve the energy efficiency of the ad hoc network.
4.3 Cross Layer Solutions
From the above survey we can see that there are many protocols that are used to improve the energy efficiency of
the network. But one problem with these methods is that, they do not give more importance to the QoS parameters of the
network such as throughput, packet delivery ratio, and end to end delay. Cross layer architecture will help to improve these
performance metrics of the network by allowing coordination and interaction among the layers.
Muhammed Kamrul Islam et al. has donecross layering between physical and the network layer in [19]. The
physical layer is responsible for transmission of bits aiming to achieve minimum bit error rate. In this protocol they assumed
that, during the route discovery process, each node has the channel side information available in terms of received SNR in
that packet transmission. During the route request, the node stores the information of SNR in the buffer. They used this value
to check the SNR values so that we could understand when these values will degrade and hence the network parameters can
be improved. Rekha Patil et al. have proposed a cost based power aware cross layer design to AODV in [20] which utilized
the battery capacity of the node as the performance metrics. It is based on sharing the MAC & physical layer information -
Transmit power, full charge battery capacity and remaining battery capacity of node at time t. All nodes except the source &
destination calculated their link cost (Ci) using the information about transmit power of node, full charge battery capacity and
the remaining battery capacity of the node. After computing, a node adds it to the path cost. Nodes before forwarding the
RREQ packet learns about its remaining battery capacity & drops the packets when it has a lower battery level than its
threshold value. Hence the network parameters are improved by this method.
In paper [21] cross layering between network and mac layers were done. They have developed this cross layered
energy based AODV (ECL-AODV) as a modification the conventional AODV routing protocol. In this protocol when the
RREQ packet is send, they first check the residual energy (Eres) of the node. If this value is less than a predefined threshold
(Eth) value, then that node is no taken into consideration during the route selection. When Eres is higher than Eth, it appends
its identifier and residual energy in the message and forwards it toward the destination. In this protocol, RTS/CTS

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transmission occurred after the route discovery and route reply to reserve the selected path so that the energy of the ad hoc
node can be saved. RTS/CTS transmission consumes low energy since this transmission occurs only in the selected path.
They have implemented this protocol for achieving quality of service (QoS) in terms of average energy consumption, packet
delivery ratio, end-to-end delay and throughput.
Paper [22] focused on the cross layer interaction between mac and routing protocols in manets and is named as LEss
remaining hop More Opportunity (LEMO) algorithm. The routing information about the total hops and the remaining hops
required by a packet to reach its destination is exploited by the MAC layer in order to give priority to the packets that are
closer to their destination. LEMO algorithm required the information of total hop numbers between the source and the
destination of the whole path and the remaining hop numbers at the forwarding node. This information can only be known by
the routing in network layer. So the cross layer interaction between mac and network layer helped to improve the
performance of the network.
5. CONCLUSION
In this paper we have done a detailed survey on various techniques which are used to improve the energy efficiency
of the ad hoc networks. These works have pointed out that energy aware routing is one of the important factors that has to be
considered to maximize the lifetime of the networks. Energy aware issues can be related with different layers of the network.
We have explained the energy aware issues in the MAC and network layers. Subsequently we have listed various methods
that are used to minimize these issues in the network. From our side, we propose a new method which is energy efficient one
using parameters of MAC and network layers based on cross layer approach. This cross layering approach will help to
improve the energy efficiency of the network without degrading the QoS parameters of the ad hoc network.
6. ACKNOWLEDGMENT
We would like to take this opportunity to express our gratitude and deep regard to Mr. George M. Jacob, Lab
Instructor, Toc H Institute of Science and Technology, for the exemplary guidance and support throughout the survey.
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