![](bg2.png)
battery of the nodes as well as minimizing the total
transmission energy.
It has been seen from [8, 9, 10] that the Ant
Colony Optimization (ACO) scheme when applied to
ad-hoc networks greatly enhances the packet delivery
ratio. Some of the popular ACO based routing
schemes are AntNet (Dorigo et al., 1991), AntHocNet
(Di Caro et al., 2005) and ARA (Guenes et al., 2002).
The earlier ACO – based routing schemes such as
AntHocNet (Di Caro et al., 2005) and ARA (Guenes
et al., 2002), devised for ad-hoc networks, were not
targeted towards energy conservation.
In the protocol proposed in this paper, we have
applied this ACO scheme in CMMBCR. The
proposed protocol is inspired from the EAAR. In
EAAR, ACO scheme is applied on the already
existing MMBCR and thus significantly improving
the packet delivery ratio. In the proposed work we
have applied ACO scheme to develop a more
efficient energy aware protocol that not only takes
care of minimizing total energy consumed in the path
but also gives special attention to the residual battery
of nodes.
EAAR only talks about residual battery of nodes,
but doesn’t bother about the total transmission
energy. Our protocol is better than CMMBCR
because we have applied ACO scheme which ensures
that there is always a back up path available in case a
route breaks due to the mobile nodes. This greatly
enhances the packet delivery ratio. Moreover, it also
takes care of the fact that if a route gets overloaded
due to traffic, an alternate route is selected for
routing which ultimately takes care of the residual
battery of nodes.
2 PROPOSED SCHEME
Initially, when a Source node 'S' wishes to
communicate with a Destination node 'D' and it does
not have the routing information for ‘D’ available, it
broadcasts a route request packet (RREQ). Each
neighbour of ‘S’ thus receives the RREQ packet. At
each node this Request packet is used to find the
destination node and the corresponding node checks
whether there is an entry in its routing table for this
destination node. If an entry for the destination node
‘D’ is found the node sends a route reply packet back
to the source node along the same path from which it
received the RREQ. If it does not have any entry for
‘D’ available in its routing table, it further broadcasts
the RREQ packet. Furthermore, to apply the ACO
scheme, we need to calculate the pheromone for each
path. A-CMMBCR considers a combination of two
routing schemes, hence, we need to calculate two
pheromones – pheromone(mt) for MTPR and
pheromone(mm) for MMBCR.As the route request
packet traverses through the path it keeps on storing
the path so that the route request packet will have to
traverse back along the same path in the opposite
direction.
Meanwhile, all the route request packets received
get converted to route reply packets as soon as they
arrive to the destination and they travel back to the
source retracing the path. If this is not possible
because of the absence of the next hop due to node
movements, the route reply packet is discarded. At
the source node when RREP packet is received
corresponding values of pheromone(mt) and
pheromone(mm) are also received. Moreover the
MBR of that route is also received.
Each node has a routing table associated with it.
The routing table contains the addresses of
destination nodes along with the neighbor node to
which the source node should forward the packet in
order to make it reach the destination. Moreover it
contains the values of various pheromones associated
with a route.
If a source node 'S' wants to send data to a
destination node 'D' then following steps must take
place:
Step 1: The node S checks its routing table to find
whether a path to D exists or not. If a path exists, it
sends the data to the next Hop; else Step 2 is
performed.
Step 2: The node S broadcasts route request packet
(RREQ). Then Step 3 is performed.
Step 3: If any neighbor node’s routing table has a
path to D exists it replies back to node S through
Route Reply packet (RREP) else it broadcasts the
RREQ. Step3 is followed for each intermediate node
thus receiving the RREQ. If
no path for D is
available, the intermediate node relays the RREQ
packet.
Step 4: As the RREQ packet is broadcast in the
network, it can eventually reach the destination node
D. At the destination node, Route Reply packet
(RREP) is generated and reply is sent back to S.
RREP is passed to node S through the intermediate
nodes along the path from which RREQ was
received. Now as each node receives the RREP
packet, it updates its routing table and inserts an
entry for the destination node.
Calculations: Since we have to apply ACO we need
to know the Pheromone for each route generated and
our scheme requires calculation of TWO
pheromones: one for MTPR and the other for
APPLICATION OF ANT COLONY OPTIMIZATION TO DEVELOP ENERGY EFFICIENT PROTOCOL IN MOBILE
AD-HOC NETWORKS
13