1. IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 59, NO. 3, MARCH 2010 1567
a small complexity. More explicitly, in Fig. 2, there are QSoIC = [15] L. Hanzo, O. Alamri, M. El-Hajjar, and N. Wu, Near-Capacity Multi-
5 iterations and QBay = 4 iterations, while the stand-alone Bayesian Functional MIMO Systems: Sphere Packing Modulation, Iterative Detec-
tion and Cooperation. New York: Wiley-IEEE Press, Apr. 2009.
MUD requires QBay = 7 iterations, which approximately halves the
[16] R. Zhang, L. Xu, S. Chen, and L. Hanzo, “Repeat accumulate code
complexity imposed. This is not shown in Fig. 2, since the trajec- division multiple access and its hybrid detection,” in Proc. IEEE ICC,
tory of the stand-alone Bayesian MUD would obfuscate that of the Beijing, China, May 19–23, 2008, pp. 4790–4794.
hybrid MUD. [17] J. Hagenauer, “The turbo principle in mobile communications,” in Proc.
Nordic Radio Symp., Oulu, Finland, Aug. 16–18, 2004.
V. C ONCLUSION
In this paper, we have proposed a novel hybrid MUD scheme by Exploring the Dynamic Nature of Mobile Nodes
switching between different MUDs based on the MI gain. Our scheme
for Predicting Route Lifetime in
combines the benefits of both low complexity and high performance
Mobile Ad Hoc Networks
and strikes an attractive tradeoff between the constituent MUDs em-
ployed as benchmarkers. Simulation results quantified the performance Xin Ming Zhang, Feng Fu Zou, En Bo Wang, and Dan Keun Sung
advantage of employing the hybrid MUD: At normalized user load of
β = 3, the SoIC MUD failed to converge, whereas the proposed hybrid
MUD achieved an infinitesimally low BER, which was similar to that Abstract—In mobile ad hoc networks, a host may exhaust its power or
of the optimal Bayesian MUD, while imposing only about half the move away without giving any notice to its cooperative nodes, causing
complexity. changes in network topology, and thus, these changes may significantly
degrade the performance of a routing protocol. Several routing protocol
studies based on node lifetime and link lifetime have been done to address
this problem. We propose a new algorithm to evaluate the node lifetime
ACKNOWLEDGMENT and the link lifetime utilizing the dynamic nature, such as the energy drain
Fully detailed technical reports on this work are available to Indus- rate and the relative mobility estimation rate of nodes. Integrating these
two performance metrics by using the proposed route lifetime-prediction
trial Members of Mobile VCE. algorithm, we select the least dynamic route with the longest lifetime for
persistent data forwarding. Finally, we implement our proposed route
R EFERENCES lifetime-prediction algorithm in an exploring dynamic nature routing
(EDNR) protocol environment based on dynamic source routing (DSR)
[1] P. Li, L. H. Liu, K. Y. Wu, and W. K. Leung, “Interleave-division multiple- and compare the performance through simulations. The EDNR proto-
access,” IEEE Trans. Wireless Commun., vol. 5, no. 4, pp. 938–947, col outperforms the conventional DSR protocols that are implemented
Apr. 2006. with lifetime-prediction routing (LPR) and signal-stability-based adaptive
[2] H. Schoeneich and P. A. Hoeher, “Adaptive interleave-division multiple (SSA) routing mechanisms.
access—A potential air interference for 4G bearer services and wireless
LANs,” in Proc. WOCN, Muscat, Oman, Jun. 7–9, 2004, pp. 179–182. Index Terms—Lifetime prediction, link lifetime (LLT), mobile ad hoc
[3] P. Frenger, P. Orten, and T. Ottosson, “Code-spread CDMA using max- networks (MANETs), node lifetime, route discovery, routing protocol.
imum free distance low-rate convolutional codes,” IEEE Trans. Wireless
Commun., vol. 48, no. 1, pp. 135–144, Jan. 2000.
[4] D. Gargy and F. Adachi, “Comprehensive evaluation of chip interleaving I. I NTRODUCTION
effect on turbo-coded DS-SS in a Rayleigh fading channel with antenna
diversity reception,” Wireless Commun. Mobile Comput., vol. 6, no. 1, A mobile ad hoc network (MANET) consists of many mobile nodes
pp. 49–60, Feb. 2006. that can communicate with each other directly or through intermediate
[5] R. Zhang and L. Hanzo, “EXIT chart based joint code-rate and spreading- nodes. Often, hosts in a MANET operate with batteries and can roam
factor optimisation of single-carrier interleave division multiple access,” freely, and thus, a host may exhaust its power or move away, giving no
in Proc. IEEE WCNC, Hong Kong, Mar. 11–15, 2007, pp. 735–739.
[6] L. Hanzo, M. Munster, B. J. Choi, and T. Keller, OFDM and MC-CDMA
notice to its neighboring nodes, causing changes in network topology.
for Broadcasting Multi-User Communications, WLANs and Broadcasting. One of the important and challenging problems in the design of ad hoc
New York: Wiley-IEEE Press, 2003. networks is the development of an efficient routing protocol that can
[7] L. Hanzo, L. L. Yang, E. L. Kuan, and K. Yen, Single- and Multi-Carrier provide high-quality communications among mobile hosts. Several
DS-CDMA: Multi-User Detection, Space-Time Spreading, Synchronisa- studies on the dynamic nature of MANETs have been done. These
tion, Networking and Standards. New York: Wiley-IEEE Press, 2003.
[8] A. J. Goldsmith, Wireless Communication. Cambridge, U.K.: studies often attempt to find a stable route that has a long lifetime [1].
Cambridge Univ. Press, 2005. We can classify these solutions into two main groups: node lifetime
[9] P. Li, Q. H. Guo, and J. Tong, “The OFDM-IDMA approach to wire- routing algorithms and link lifetime (LLT) routing algorithms.
less communication systems,” IEEE Wireless Commun., vol. 14, no. 3, By considering the energy state of nodes, such as residual energy
pp. 18–24, Jun. 2007.
[10] P. Hoeher and W. Xu, “Multi-layer interleave-division multiple access for
and energy drain rate, the node lifetime routing algorithms often select
3GPP long term evolution,” in Proc. ICC, Glasgow, U.K., Jun. 24–28,
2007, pp. 5508–5513. Manuscript received July 27, 2009; revised October 13, 2009. First published
[11] R. Zhang and L. Hanzo, “Three design aspects of multicarrier interleave December 18, 2009; current version published March 19, 2010. This work was
division multiple access,” IEEE Trans. Veh. Technol., vol. 57, no. 6, supported in part by the National Natural Science Foundation of China under
pp. 3607–3617, Nov. 2008. Grant 60673171 and in part by the National Grand Fundamental Research 973
[12] L. Hanzo, T. H. Liew, and B. L. Yeap, Turbo Coding, Turbo Equalisa- Program of China under Grant 2006CB303006. The review of this paper was
tion and Space-Time Coding for Transmission Over Fading Channels. coordinated by Prof. J. Misic.
New York: Wiley-IEEE Press, 2002. X. M. Zhang, F. F. Zou, and E. B. Wang are with the School of Computer
[13] X. D. Wang and H. V. Poor, “Iterative (turbo) soft interference cancellation Science and Technology, University of Science and Technology of China,
and decoding for coded CDMA,” IEEE Trans. Commun., vol. 47, no. 7, Hefei 230027, China (e-mail: xinming@ustc.edu.cn; fengfu@mail.ustc.edu.cn;
pp. 1046–1061, Jul. 1999. wangeb@mail.ustc.edu.cn).
[14] S. ten Brink, “Convergence behavior of iteratively decoded parallel con- D. K. Sung is with the Korea Advanced Institute of Science and Technology,
catenated codes,” IEEE Trans. Commun., vol. 49, no. 10, pp. 1727–1737, Daejeon 305-701, Korea (e-mail: dksung@ee.kaist.ac.kr).
Oct. 2001. Digital Object Identifier 10.1109/TVT.2009.2038708
0018-9545/$26.00 © 2010 IEEE
Authorized licensed use limited to: University of Science and Technology of China. Downloaded on March 18,2010 at 04:40:01 EDT from IEEE Xplore. Restrictions apply.

2. 1568 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 59, NO. 3, MARCH 2010
a path consisting of nodes that may survive for the longest time among lifetime of the route becomes the minimum lifetime of all links in this
multiple paths. Shrestha and Mans [2] mentioned that the energy drain route. A link is formed by two adjacent mobile nodes, which have
rate of a node is affected not only by its own but by its neighboring data limited battery energy and can roam freely, and it is broken if any
flows as well. Marbuhk and Subbarao [3] aimed to preserve network of the two nodes is not alive due to exhaustion of energy or if these
connectivity by choosing a route according to the remaining battery two nodes move out of each other’s communication range. We use the
life of nodes along the route. Toh [4] proposed selecting a path with connection lifetime and the node lifetime to distinguish the two cases
minimum total transmission power when there exist some possible described above. The connection lifetime is described as LLT in [7]–
paths, and all nodes through these paths have sufficient residual battery [14]. In this paper, a link is composed of the two nodes in a connection
power. Misra and Banerjee [5] proposed selecting a path that has and the connection itself, and the LLT includes both the node lifetime
the largest packet transmission capacity (the residual energy divided and the connection lifetime.
by the expected energy spent in reliably forwarding a packet) at a A link Li consists of a connection Ci and two nodes (Ni−1 , Ni ),
“critical” node among multiple paths. The critical node is the node where Ci represents the connection between nodes Ni−1 and Ni ,
that has the smallest packet transmission capacity in a path. In the and it is maintained until the adjacent nodes (Ni−1 , Ni ) move out of
lifetime-prediction routing (LPR) algorithm [6], each node attempts each other’s communication range under the assumption of no energy
to estimate its battery lifetime based on its residual energy and its past problem in both nodes Ni−1 and Ni . We introduce connection lifetime
activity. The above algorithms used well-defined metrics to evaluate TCi to represent the estimated lifetime of the connection Ci , and it
the lifetime of nodes. However, all of them ignored the mobility of only depends on their relative mobility and distance of nodes Ni−1
mobile hosts, and thus, it seems that they are more suitable for static and Ni at a given time. The term TNi denotes the estimated battery
networks. lifetime of node Ni . Then, the lifetime of the link Li is expressed as
The LLT routing algorithms are used to estimate the lifetime of the minimum value of (TCi , TNi−1 , TNi ), i.e.,
wireless links between every two adjacent nodes and then to select an
optimal path. In the associativity-based routing algorithm [7], a link is TLi = min(TCi , TNi−1 , TNi ). (1)
considered to be stable when its lifetime exceeds a specific threshold
Take as an example a route P consisting of n links. Route P is said
that depends on the relative speed of mobile hosts. In the signal-
to be broken if any one of the following cases occurs. First, any one of
stability-based adaptive (SSA) routing [8], each link is classified as
the nodes in the route dies because of limited battery energy. Second,
a strong one or a weak one, depending on the received signal strength
any one of the connections is broken because the corresponding two
measured when a node receives data packets from the corresponding
adjacent nodes move out of each other’s communication range. Thus,
upstream node. A mobile node only processes a route request (RREQ)
the lifetime of route P is expressed as the minimum value of the
that is received from a strong link. Tickoo et al. [9] computed the
lifetime of both nodes and connections involved in route P. Assume
fragility of a link as the difference of the received signal strengths of
that Ω represents the set of all nodes in route P and that Ψ is the set of
consecutive packets flowing from the same origin to check if these two
all the connections in route P. Thus, the lifetime Tp of route P can be
nodes are getting closer or moving apart. Gerharz et al. [10] predicted
expressed as
the lifetime of a link between two adjacent mobile hosts through online
statistical analysis of the observed links. Several studies [11]–[14] Tp = min (TNi , TCi ) . (2)
attempted to predict the expiration time of the links by estimating Ni ∈Ω,Ci ∈Ψ
the mobility of nodes. Note that all of these studies assumed for
simplicity that mobile hosts are kept at a constant speed and direction From (2), the lifetime Tp of route P is estimated from the prediction
in a short period. Samar and Wicker [13] developed an analytical lifetime of each node and each connection.
framework to investigate the behavior of nodes in a random mobility
environment and derived analytical expressions that are related to the A. Node Lifetime Prediction Algorithm
lifetime of links. As a different approach, Wu et al. [14] used a two-
state Markovian model to reflect the mobility of nodes and evaluate the Intuitively, if there are two nodes that have the same residual energy
link dynamics. level, an active node that is used in many data-forwarding paths
In MANETs, a route consists of multiple links in series, and thus, its consumes energy more quickly, and thus, it has a shorter lifetime than
lifetime depends on the lifetime of each node, as well as the wireless the remaining inactive node. With the same concept as described in
links between adjacent nodes. The main contribution of this paper is [6], we evaluate the node lifetime that is based on its current residual
that we combine node lifetime and LLT in our route lifetime-prediction energy and its past activity; however, we present a much simpler
algorithm, which explores the dynamic nature of mobile nodes (i.e., solution that does not need to calculate the predicted node lifetime
the energy drain rate of nodes and the relative mobility estimation from each data packet.
rate at which adjacent nodes move apart) in a route-discovery period The term Ei represents the current residual energy of node i, and
that predicts the lifetime of routes discovered, and then, we select the evi is the rate of energy depletion. Ei can simply be obtained online
longest lifetime route for persistent data forwarding when making a from a battery management instrument, and evi is the statistical value
route decision. The rest of this paper is organized as follows. Section II that is obtained from recent history. We use an exponentially weighted
describes the proposed route lifetime-prediction algorithm. Section III moving average method to estimate the energy drain rate evi .
implements our proposed algorithm in an exploring dynamic nature Every T seconds (the smaller the value of T , the more accu-
routing (EDNR) protocol environment based on dynamic source rout- rate this algorithm is), node i reads the instantaneous residual en-
0 2T 3T (n−1)T nT
ing (DSR). Section IV presents the performance-evaluation results. ergy value Ei , Ei , Ei , . . . , Ei , Ei , . . ., in every period
Finally, Section V draws the conclusion. [0, T], [T, 2T], [2T, 3T], . . . , [(n − 1)T, nT] . . ., and the correspond-
ing estimated energy drain rate evi is obtained as
⎧ 0
II. ROUTE L IFETIME -P REDICTION A LGORITHM ⎪ evi = 0,
⎨ n=0
evi = Ei − Ei /T,
1 0 T
n=1
(3)
Since a route consists of multiple links in series, it is said to be ⎪ ev n = α E (n−1)T − E nT /T + (1 − α)ev n−1 , n > 1
⎩ i
broken if any single link among its links is broken, and thus, the i i i
Authorized licensed use limited to: University of Science and Technology of China. Downloaded on March 18,2010 at 04:40:01 EDT from IEEE Xplore. Restrictions apply.

3. IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 59, NO. 3, MARCH 2010 1569
Fig. 1. Relative motion.
Fig. 2. LLT prediction algorithm.
n
where eviis the estimated energy drain rate in the nth period, and
evin−1
is the estimated energy drain rate in the previous (n − 1)th To calculate the connection time TCi , we apply a triangle geometry
n
period. α denotes the coefficient that reflects the relation between evi theory and improve the method that needs three sample packets and
n−1 predicts the link expiration time for proactive route maintenance in the
and evi , and it is a constant value with a range of [0, 1]. In this
algorithm, to reflect the current condition of node i well, we grant a previous work [11]. Our proposed method requires only two sample
n
higher priority to evi and set α = 0.6. packets, and we implement piggyback information on route-request
At time t, we can obtain the estimated node lifetime as follows: (RREQ) and route-reply (RREP) packets during a route-discovery
procedure (details described in Section III) with no other control
nT n
TNi = Ei /evi , t ∈ [nT, (n + 1)T ] . (4) message overhead, and thus, it does not increase time complexity.
Fig. 2 illustrates the proposed LLT prediction algorithm. If node Ni
is set to the reference frame, node Ni−1 moves at velocity v relative
B. Connection Lifetime-Prediction Algorithm to the velocity of node Ni . Ni−1 receives two packets from node Ni
We evaluate the LLT using the connection lifetime; however, it is at time t0 and t1 . We assume that node Ni−1 moves out of node Ni ’s
difficult to predict the connection lifetime TCi between two nodes radio transmission range at prediction time t.
(Ni−1 , Ni ) because the nodes in MANETs may move freely [10]– At time t0 , node Ni−1 receives a packet from node Ni , and the
[12]. In our algorithm, we only handle the connections that are in an received signal power is P0 ; thus, the distance d0 between the two
unstable state and may only last for a short period particularly, ignoring nodes can be calculated by using a radio-propagation model [16].
the stable one for simplicity. The reasons are given as follows: First, we We select a two-ray ground model for simulation in NS-2 [17]. By
are only concerned with the minimum node lifetime or the connection using the same method, d1 can also be calculated. For the three
lifetime in a route from (2). Since two nodes of a stable connection are unknown parameters (t, v, θ) in Fig. 2, we first state them in the
within the communication range of each other, the connection lifetime following when using the law of cosines to solve the triangle problem
may last longer, and they are not a bottleneck from the route to which in Fig. 2:
they belong. Second, it is easier to model the mobility of nodes in a
short period during which unstable connections last. We can assume d2 = d2 + [v(t1 − t0 )]2 − 2d0 v(t1 − t0 ) cos θ
1 0 (6)
reasonably and simply that the nodes move at a constant speed toward
the same direction in such a short period. Note that previous works R1 = d2 + [v(t − t0 )]2 − 2d0 v(t − t0 ) cos θ
2
0 (7)
[11]–[14] are based on this assumption.
The connection time TCi depends on the relative motion between where v = |vi |, and R is the radio-transmission range and is a constant
Ni and Ni−1 , and the connection is said to be broken when two that is determined by the system. Another important equation can be
nodes (Ni−1 , Ni ) are moving out of each other’s radio transmission derived by the area relation among three triangles ( OAB, OBC,
range R. Apparently, there are two important issues here. One is and OAC). In Fig. 2, there is SOAC = SOAB + SOBC , and it is
how to measure the distance between nodes Ni and Ni−1 , while the converted into the following when we apply Heron’s formula to it
other is how to compute the relative velocity of these two mobile [s = l(l − a)(l − b)(l − c), where the term s represents the area of
nodes. a triangle, the terms a, b, and c represent the three sides of the triangle,
It is easy to measure the distance between nodes Ni and Ni−1 and l = (a + b + c)/2]:
when we use Global-Positioning-System-based location information
and then compute it just as described in [12]. Another simple method, l0 (l0 − d0 )(l0 − R) (l0 − v(t − t0 ))
which is our approach, is to measure the received signal strength.
Assuming that senders transmit packets with the same power level, = l1 (l1 − d0 )(l1 − d1 ) (l1 − v(t1 − t0 ))
a receiver can measure the received signal power strength when
receiving a packet and then calculates the distance by directly applying
the radio propagation model [16]. If the received signal power strength + l2 (l2 − d1 )(l2 − R) (l2 − v(t − t1 )) (8)
is lower than a threshold value, we regard this link as an unstable state
and then calculate the connection time. where l0 = (d0 + R + v(t − t0 ))/2, l1 = (d0 + d1 + v(t1 − t0 ))/2,
Fig. 1 shows the relative motion of two nodes (Ni−1 , Ni ) moving at and l2 = (d1 + R + v(t − t1 ))/2 are all formulated by v and t, and
relative velocities vi and vi−1 relative to ground at a given time t. The then, there are three unknown parameters (t, v, θ) in (6)–(8). Thus,
ground is used as a reference frame by default. If we consider node Ni the connection breakage time t can be obtained by solving these
as the reference frame, node Ni−1 is moving at a relative velocity of v, simultaneous equations, and the residual connection time TCi is
as given by the following: calculated as
v = vi−1 − vi . (5) TCi = t − t1 . (9)
Authorized licensed use limited to: University of Science and Technology of China. Downloaded on March 18,2010 at 04:40:01 EDT from IEEE Xplore. Restrictions apply.

4. 1570 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 59, NO. 3, MARCH 2010
III. D ESCRIPTION OF THE P ROPOSED E XPLORING
DYNAMIC NATURE ROUTING P ROTOCOL
Since DSR [15] is one of the most popular routing protocols in
MANETs and it is easy to extend the routing control message format of
DSR, we implement the proposed route lifetime-prediction algorithm
in the DSR protocol. The proposed algorithm consists of the following
three phases: route discovery, data forwarding, and route maintenance.
There are three main differences between the EDNR and the DSR.
First, in the EDNR protocol, every node saves the received signal
strength and the received time of the RREQ packet in its local memory,
and adds this information into the RREP packet header in a piggyback
manner when it receives the RREP for the corresponding RREQ
packet to meet the requirement of the connection lifetime-prediction
algorithm. Second, node agents need to update their predicted node
lifetime during every period. Finally, the node-lifetime information in
the RREP packet is updated when the RREP packet is returned from a
destination node to the source node.
At every EDNR node agent, a variable NLT, which represents the
node lifetime, is added to represent the estimated lifetime of this node, Fig. 3. Throughput.
and it is updated by the algorithm in Section II-A. For the lifetime of a
link Ci , there are two sample packets exchanged between nodes Ni−1
RREQ RREP
and Ni (packet 1: Ni−1 − − − −→ Ni ; packet 2: Ni−1 ←− − Ni ) in
−−
the route-discovery phase, and thus, we can estimate the LLT using
the proposed algorithm presented in Section II-B. To implement this,
every node agent needs to maintain a data structure called RREQ_Info
table in its local memory. This structure includes the RREQ id, the
forwarding RREQ time, and the RREQ received signal strength. For a
path sequence S, . . . , Ni−1 , Ni , Ni+1 , . . . , D, when an intermediate
node Ni receives an RREQ packet from Ni−1 , it adds this RREQ id,
the current time, and the received signal strength to its RREQ_Info
table before it continues to forward this RREQ packet. Similarly, node
Ni+1 also saves the RREQ_Info from node Ni in its local memory.
In the returning RREP period, when node Ni receives an RREP
packet from node Ni+1 , the RREQ_Info from Ni (information of
RREQ
Ni − −
− −→ Ni+1 ) has been added to the RREP header by Ni+1 before
node Ni+1 sends an RREP packet to node Ni . Simultaneously, node
Ni knows the RREP time and the RREP received signal strength from
RREP
node Ni+1 (information of Ni ←− − Ni+1 ). Thus, it can obtain the
−− Fig. 4. Number of routing failures.
second sample packet that is delivered between the corresponding two
nodes (Ni , Ni+1 ), and, thus, we can calculate the connection time TCi
using the connection lifetime-prediction algorithm and then update the
local LLT value. Similarly, node Ni should add the RREQ_Info entry IV. P ERFORMANCE E VALUATION
that is received from node Ni−1 to the RREP header before sending the
RREP to node Ni−1 , and then node Ni−1 calculates the LLT between A. Simulation Environment
nodes (Ni−1 , Ni ). For our simulations, we use a discrete event-driven simulator NS-2
Three new entries, i.e., path lifetime (PLT), RREQ time, and RREQ [17]. To evaluate the effect of mobility on the performance of routing
signal strength, are added to the common header of an RREP packet. protocols, the mobility of nodes follows a random way-point model
The PLT represents the predicted lifetime of the source route in this [18]. A mobile node starts a trip to a random destination at a con-
packet header and can be updated when RREP packets are forwarded stant speed chosen from a uniform distribution (1, max speed] [19],
from the destination node to the source node in the route-discovery then stops for a predefined pause time, and starts another trip to a
phase. The RREQ time and the RREQ signal strength represent the random destination again. The source–destination connection patterns
RREQ_Info of the previous RREQ node. The EDNR node agent only are generated using cbrgen.tcl in NS-2. The initial energy is the same
updates the PLT value in the common header of the RREP packet with as [6], and simulation time is set to 1000 s, which is different from
a local NLT value or LLT value, if NLT < PLT or LLT < PLT, before that in [6] because we employ the time of the first node breakdown
forwarding this RREP packet. When this RREP packet reaches the as the criterion of the network lifetime, whereas the network lifetime
source node, the PLT becomes the minimum value of the estimated in [6] is the time taken for a fixed percentage of the nodes to die.
lifetime of all nodes and links through the route from the source node Each data point represents an average of five different randomly
to the destination node, as described in (2). In the persistent data- generated mobility models. The confidence level is set to 95%, and the
forwarding period, a source node tends to select the path with the confidence interval is shown as a vertical bar in the figures (Figs. 3–5).
longest lifetime (the path with the maximum PLT value) from multiple Table I summarizes the more detailed simulation parameter
paths as a source route for data forwarding. values.
Authorized licensed use limited to: University of Science and Technology of China. Downloaded on March 18,2010 at 04:40:01 EDT from IEEE Xplore. Restrictions apply.

5. IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 59, NO. 3, MARCH 2010 1571
Fig. 3 shows the throughput performance in terms of the number of
packets for the four routing protocols. The proposed EDNR protocol
outperforms the remaining three protocols in varying node velocity en-
vironments. Its throughput enhancement is achieved by approximately
79.2%, 14.2%, and 13.8%, compared with that of the original DSR,
LPR, and SSA mechanisms, respectively.
Fig. 4 shows the advantage of the EDNR protocol in terms of the
number of routing failures. To adapt to dynamically varying network
topology environments, the EDNR, LPR, and SSA protocols do their
best to find a more stable route, reducing the number of routing
failures by 21.2%, 15.6%, and 14.2%, respectively, compared with
that of the original DSR. Fig. 4 shows that the number of routing
failures greatly increases with an increase in the node’s mobility
speed.
Routing overhead is defined as the amount of routing control
packets, including RREQ and RREP. Fig. 5 shows the routing overhead
of the four routing protocols. The EDNR protocol yields a significant
improvement with the help of our proposed route lifetime-prediction
Fig. 5. Routing overhead. algorithm, and its overhead is reduced by 25.6%, 9.4%, and 6.3%,
compared with that of the original DSR, LPR, and SSA, respectively.
However, the length of RREP packets is 3 × 4 B longer than that of
TABLE I
S IMULATION PARAMETERS the DSR.
V. C ONCLUSION
In MANETs, a link is formed by two adjacent mobile nodes, which
have limited battery energy and can roam freely, and the link is said
to be broken if any of the nodes dies because they run out of energy
or they move out of each other’s communication range. In this paper,
we have considered both the node lifetime and the LLT to predict
the route lifetime and have proposed a new algorithm that explores
the dynamic nature of mobile nodes, such as the energy drain rate
and the relative motion estimation rate of nodes, to evaluate the node
lifetime and the LLT. Combining these two metrics by using our
proposed route lifetime-prediction algorithm, we can select the least
dynamic route with the longest lifetime for persistent data forwarding.
Finally, we have evaluated the performance of the proposed EDNR
protocol based on the DSR. Simulation results show that the EDNR
protocol outperforms the DSR protocol implemented with LPR and
SSA mechanisms.
R EFERENCES
[1] X. H. Wei, G. L. Chen, Y. Y. Wan, and X. M. Zhang, “Longest lifetime
path in mobile ad hoc networks,” J. Softw., vol. 17, no. 3, pp. 498–508,
2006.
B. Simulation Results [2] N. Shrestha and B. Mans, “Exploiting overhearing: Flow-aware routing
for improved lifetime in ad hoc networks,” in Proc. IEEE Int. Conf.
To evaluate the performance of the EDNR, we compare the per- Mobile Ad-hoc Sens. Syst., 2007, pp. 1–5.
formance of the EDNR with those of the following three routing [3] V. Marbukh and M. Subbarao, “Framework for maximum survivability
protocols: 1) the original DSR, 2) the DSR with the existing LPR routing for a MANET,” in Proc. MILCOM, 2000, pp. 282–286.
[4] C.-K. Toh, “Maximum battery life routing to support ubiquitous mobile
mechanism [6], and 3) the DSR with SSA [8], in terms of network computing in wireless ad hoc networks,” IEEE Commun. Mag., vol. 39,
throughput, routing failures, and control packet overhead. The original no. 6, pp. 138–147, Jun. 2001.
DSR tends to find the shortest path from the source node to the [5] A. Misra and S. Banerjee, “MRPC: Maximizing network lifetime for
destination node, ignoring the node lifetime and wireless LLT. The reliable routing in wireless environments,” in Proc. IEEE WCNC, 2002,
pp. 800–806.
LPR mechanism attempts to find a stable route by considering the
[6] M. Maleki, K. Dantu, and M. Pedram, “Lifetime prediction
node lifetime based on residual battery and past activity. The SSA routing in mobile ad hoc networks,” in Proc. IEEE WCNC, 2003,
mechanism estimates the wireless LLT by classifying neighbors into pp. 1185–1190.
a strongly connected set and a weakly connected set, and it drops [7] C. K. Toh, “Associativity-based routing for ad hoc mobile networks,”
the RREQ from weakly connected neighbors. Generally speaking, the Wirel. Pers. Commun.—Special Issue on Mobile Networking and Com-
puting Systems, vol. 4, no. 2, pp. 103–139, Mar. 1997.
LPR mechanism performs better in a low-mobility scenario, whereas [8] R. Dube, C. D. Rais, K. Y. Wang, and S. K. Tipathi, “Signal stability-
the SSA mechanism seems to be more suitable for a high-mobility based adaptive routing (SSA) for ad hoc mobile networks,” IEEE Pers.
scenario. Commun., vol. 4, no. 1, pp. 36–45, Feb. 1997.
Authorized licensed use limited to: University of Science and Technology of China. Downloaded on March 18,2010 at 04:40:01 EDT from IEEE Xplore. Restrictions apply.

6. 1572 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 59, NO. 3, MARCH 2010
[9] O. Tickoo, S. Raghunath, and S. Kalyanaraman, “Route fragility: A novel [14] X. Wu, H. R. Sadjadpour, and J. J. Garcia-Luna-Aceves, “An analytical
metric for route selection in mobile ad hoc networks,” in Proc. IEEE framework for the characterization of link dynamics in MANETs,” in
ICON, 2003, pp. 537–542. Proc. IEEE Mil. Commun. Conf., 2006, pp. 1–7.
[10] M. Gerharz, C. de Waal, M. Frank, and P. Martini, “Link stability in [15] D. Johnson, Y. Hu, and D. Maltz, DSR:RFC 4728. [Online]. Available:
mobile wireless ad hoc networks,” in Proc. 27th Annu. IEEE Conf. Local http://www.ietf.org/rfc/rfc4728.txt
Comput. Netw., 2002, pp. 30–42. [16] T. K. Sarkar, Z. Ji, K. Kim, A. Medouri, and M. Salazar-Palma, “A
[11] L. Qin and T. Kunz, “Pro-active route maintenance in DSR,” ACM survey of various propagation models for mobile communication,” IEEE
SIGMOBILE Mobile Comput. Commun. Rev., vol. 6, no. 3, pp. 79–89, Antennas Propag. Mag., vol. 45, no. 3, pp. 51–82, Jun. 2003.
Jul. 2002. [17] [Online]. Available: http://www.isi.edu/nsnam/ns
[12] W. Su, S. J. Lee, and M. Gerla, “Mobility prediction and routing in [18] C. Bettstetter, G. Resta, and P. Santi, “The node distribution of the random
ad hoc wireless networks,” Int. J. Netw. Manage., vol. 11, no. 1, pp. 3– waypoint mobility model for wireless ad hoc networks,” IEEE Trans.
30, Jan./Feb. 2001. Mobile Comput., vol. 2, no. 3, pp. 257–269, Jul.–Sep. 2003.
[13] P. Samar and S. B. Wicker, “On the behavior of communication links of [19] J.-Y. Le Boudec and M. Vojnovic, “Perfect simulation and station-
a node in a multi-hop mobile environment,” in Proc. Int. Symp. Mobile arity of a class of mobility models,” in Proc. IEEE INFOCOM, 2005,
Ad Hoc Netw. Comput., 2004, pp. 145–156. pp. 2743–2754.
Authorized licensed use limited to: University of Science and Technology of China. Downloaded on March 18,2010 at 04:40:01 EDT from IEEE Xplore. Restrictions apply.