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Modified LEACH – Energy Efficient Wireless Networks Communication

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Many algorithms and techniques were proposed to increase the efficiency of Sensor Networks. Due to high restrictions of this kind of networks, where the resources are limited, many factors may affect its work. Theses factors are: System throughput, system delay, and energy. Clustering protocols have been propose to decrease system throughput and system delay, and increase energy saving. In this paper, we propose a new technique that can be applied to sensor networks to produce high performance and stable Sensor Networks.
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Modified LEACH Energy Efficient Wireless
Networks Communication
Abuhelaleh, Mohammed Elleithy, Khaled Mismar, Thabet
School of Engineering, University of Bridgeport
Bridgeport, CT 06604
{mabuhela, elleithy, tmismar} @bridgeport.edu
Abstract-Many algorithms and techniques were proposed to
increase the efficiency of Sensor Networks. Due to high
restrictions of this kind of networks, where the resources are
limited, many factors may affect its work. Theses factors are:
System throughput, system delay, and energy. Clustering
protocols have been propose to decrease system throughput and
system delay, and increase energy saving. In this paper, we
propose a new technique that can be applied to sensor networks to
produce high performance and stable Sensor Networks.
Index Terms- LEACH (Low Energy Adaptive Clustering
Hierarchy), Sensor Networks, Network Performance, Routing.
I. INTRODUCTION
There are many advantages of using sensor networks.
They provide dynamic and wireless communication between
nodes in a network, which provides more flexible
communication. At the same time, sensor networks have some
special characteristics compared to traditional networks, which
makes it harder to deal with. The most important property that
affects this type of networks is the limitation of the resources
available, especially the energy.
Wireless Sensor Networks (WSNs) [2] are a special kind
of Ad hoc networks that became one of the most interesting
areas for researchers. Routing techniques are the most
important issue for networks where resources are limited.
Cluster-based organization has been proposed to provide an
efficient way to save energy during communication [3]. In this
kind of organization, nodes are organized into clusters. Cluster
heads (CHs) pass messages between groups of nodes (group
for each CH) and the base station (BS), (Figure1). This
organization provides some energy saving which is the main
advantage for proposing this organization. Depending on this
organization, LEACH (Low Energy Adaptive Clustering
Hierarchy) [3] enhanced security, where the CHs are rotating
from node to node in the network making it harder for
intruders to know the routing elements and attack them. [4]
In this paper, we discuss some existing work of LEACH
and we focus on two important criteria; the performance and
energy consumption. In section two, we discuss the original
work of LEACH, and then in the third section we discuss one
of the most interesting modifications proposed for LEACH to
increase network performance (TCCA). In the fourth section,
we discuss our proposal and we explain the main modifications
that we applied on LEACH to improve network performance.
In section 5, we discuss our experiment that we applied to
show the improvements that may gain from applying our
protocol comparing to the existing protocols.
II. LEACH
Low Energy Adaptive Clustering Hierarchy has been
presented by [1] to balance the draining of energy during
communication between nodes in sensor networks. The BS
assumed to be directly reachable by all nodes by transmitting
with high enough power. Nodes send their sensor reports to
their CHs, which then combine the reports in one aggregated
report and send it to the BS. To avoid the energy draining of
limited sets of CHs, LEACH rotates CHs randomly among all
sensors in the network in order to distribute the energy
consumption among all sensors. It works in rounds; in each
round, LEACH elects CHs using a distributed algorithm and
then dynamically clusters the remaining sensors around the
CHs. Sensor-BS communication then uses this clustering result
for the rest of the round. (See Fig.1)
A. LEACH Protocol
Routing in LEACH works in rounds and each round is
divided into two phases, the Setup phase and the Steady State;
each sensor knows when each round starts using a
synchronized clock [1, 2].
Initially, each sensor decides if it will be a CH or not
based on the desired percentage of the CHs for the network,
and the number of times the sensor has been a CH (to control
the energy consumption), this decision is made by the sensor
(s) choosing a random number between Zero and One. Then it
calculates the threshold for (s) T(s), then it compares the
random number with resulting T(s); if the number is less than
Figure1. Cluster organization for sensor networks
T(s), (s) becomes a CH for the current round. T(s) for x round
with desired percentage of cluster heads P is calculated by (1):
T(s) =
otherwise
Gifn
P
xP
P
P
...................................0
........
)
1
mod(*1
........ (1)
G is a set of nodes that have not been CHs in the last 1/p round.
Setup phase includes three steps. Step1 is the
advertisement step, where each sensor decides its probability to
become a CH, based on the desired percentage of CHs and its
remaining energy, for the current round; Sensor who decides to
become a CH broadcasts an advertising message to other nodes
that it is ready to become a CH. Carrier sense multiple access
protocol is used to avoid the collision. Clustering joining step
is the second step, where the remaining sensors pick a cluster
to join according to the highest signal received; then they send
request messages to the desired CHs. Step three starts after the
CHs receive all requests from other sensors, where CHs
broadcast confirmation messages to their cluster members;
these messages include the time slot schedule to be used during
the steady state phase.
The Steady State phase (the actual communication) then
starts. It consists of two steps; in the first step each nodes starts
by send its sensor report to its CH based on the time provided
by the time slot schedule. When CH receives all the reports, it
aggregates them in one report and it sends this report to the BS
(step 2). Next we show the details of each step by providing
the content of each one; for this purpose we combine the two
phases in one phase with five steps.
In step one, CH broadcasts to the rest of sensors, its ID
and the Advertising message, then, in step two, each sensor
sends its ID, CH ID, and the Join Request message to its
desired CH. When CH received all requests, it broadcasts its
ID, and the time slot schedule for sensors that includes each
member with its time slot (step three). Each sensor then sends
its ID, CH ID, and the sensing report to its CH (step four).
Finally, each CH sends its ID, BS ID, and the aggregate report
of its members to the BS.
The transmission of information between sensors, and
between sensors and BSs, are performed using CSMA MAC
protocol. On the other hand, they communicate using CDMA
codes to reduce the interference that may occur from
communication of nearby nodes.
B. Energy saving in LEACH
LEACH is a self-organization adaptive protocol, and it
uses randomization to evenly distribute the energy load among
the sensors in the network; this and the random way that CHs
rotate around the various sensors reduce the possible draining
of the battery for each sensor.
A local data compression to compress the amount of data
being sent from clusters to BS is used to reduce the energy
consumption and to enhance the system lifetime.
The time schedule that is being performed by CHs to their
members, gives break time for sensors that have not reached
their time yet, to be in sleeping mode which helps them save
their energy for their scheduled time.
Finally, the nature of the way that LEACH changes CHs
each round, and the way that each CH can be elected, provides
high energy saving for whole network.
C. Security in LEACH
LEACH is more powerful against attacks than most other
routing protocols [2, 4]. CHs in LEACH that directly
communicate with BS can be anywhere in the network and
they are changing from round to round, which makes it harder
for intruders to identify the critical nodes in the network.
On the other hand, LEACH is vulnerable to a number of
security attacks [2, 4], including spoofing, jamming, and replay
attacks. Since LEACH is a cluster based protocol, it relies
mainly on the CHs for routing and data aggregation, which
makes the attacks involving CHs, the most harmful attacks.
Some kinds of attacks, such as sinkhole and selective
forwarding, may occur if an intruder manages to become a CH,
which results in disrupting the work of the network.
III. TCCA
Time-Controlled Clustering Algorithm (TCCA) allows
multi-hop clusters using message time-to-live (TTL) and
timestamp to control the way the clusters form. Residual
energy is also considered before a sensor volunteers to become
a CH, and a numerical model is provided to quantify its
efficiency on energy usage.
A. TCCA Protocol
Similar to LEACH, TCCA’s operation is divided into
rounds with two phases concluded in each round (Setup phase
and the Steady State phase). CHs are elected and the clusters
are formed in Setup phase; then the complete cycle of data
collection, aggregation and transfer to the BS occurs in the
Steady State phase.
To determine the eligibility of sensor to be CH,
TCCA adds some modifications to the LEACH technique. A
sensor residual energy is considered and a random number
between 0 and 1 (Tmin) is generated by each sensor to
determine its eligibility to become CH. If this number is less
than the variable threshold, the sensor becomes a CH for the
current round. The threshold for sensor s in round r, with
desired CH percentage p, residential energy RE and maximum
energy MaxE is calculated by (2):
Gs
GsT
MaxE
RE
p
rp
p
P
sT
0
min)...,
)
1
mod(1
max(
)(
G is a set of nodes that have not been CHs in the last 1/p round
When CH is elected, it advertises to other sensors to
become its members; this advertisement message contains CH
ID, initial TTL, timestamp and its residual energy. Sensors
…… (2)
receive the message will forward it to their neighbors based on
TTL value which may be based on the current energy level of
CH; at the same time they join this CH with the rest of sensors
who received the message. Once a sensor decides to join the
cluster, it informs the corresponding CH by sending a join
request message that carries sensor ID, CH ID, the original
timestamp from advertising message and the remaining TTL
value. The CH uses the timestamp to approximate the relative
distance of its neighbors and to learn the best setup phase time
for future rounds [3].
The time schedule that is to be advertised by the CH is
based on the total number of its members and their relative
distance, to avoid collision.
Timestamp and TTL are used in TCCA to give the CH the
ability to produce multi-hops clusters in efficient way that has
the same performance of the one-hop clusters.
B. Energy saving in TCCA
TCCA applies a new condition for electing CHs by
considering the remaining energy of the sensors. At the same
time, it guarantees that every sensor will become a CH at least
one time per 1/P rounds, where P is the desired percentage of
CHs. These modifications provide the network with high
energy balance by distributing the energy among all sensors.
TCCA provides optimum cluster size (K) for K-hops in
order to produce high performance similar to the performance
in the one-hop network. Also it reduces the complexity of
transmission schedule generation to O (1).
TCCA uses timestamp and Time to live (TTL) tags to
control the cluster formation; this leads to gain more energy
balance.
C. Security in TCCA
TCCA follows the main steps provided by LEACH with
some modifications that do not affect the level of security that
is provided by LEACH; this means that TCCA does not have
enough protection against Spoofing, Jamming, Replay and
some other kind of attacks.
IV. MODIFIED-LEACH
The operation of Modified-LEACH (Mod-LEACH) works
in two rounds: a Full transmission round and a half
transmission one.
Each sensor checks its ability to become a CH depending
on the desired percentage of CHs, current round, and the
remaining energy; we used the same formula used by TCCA to
calculate the threshold.
The sensors that are able to become CH (ready sensors)
for the current round start listening for any query that might be
sent by other sensors; the other sensors start broadcasting their
reports to their neighbors, the packets contain some other tags
to determine the status of the packets; any ready sensor that
receives the report saves it temporarily and sends a
confirmation/request to the related sensor confirming that it is
ready to send its report and providing its ability status to
become a CH for next round. Sensors who receive the
confirmation, reply back to the CH with another confirmation
and save the CH id to use it for the next round (if the status of
the CH shows that it is able to be a CH for two rounds; CHs
will collect all the reports that have been confirmed in one
compressed report and forwards it to the B.S. (This is
considered as a full transmission round).
For the next round, the sensors with no CHs will repeat the
same scenario, and the sensors with CHs will send the report
only to their CHs; when the old CHs receive the reports, it will
aggregate them in one report and forward it to the B.S. (this
considered as a half transmission report).
Next we will explain in details the complete protocol.
A. Mod-LEACH Protocol
The operation of the Mod-LEACH occurs in rounds, and
rounds are classified into two kinds, the full transmission round
and the half transmission round. The main idea here is to skip
the setup phase that is proposed by all other discussed
protocols.
At the beginning of each round, CHs elect themselves. In
order to determine the eligibility of sensor to be a CH, each
sensor (S) generates a random number between 0 and 1; then
this number is compared to a sensor variable threshold value
T(S); if the value of the threshold is greater than the random
number, the sensor becomes a CH for the current round (R).
The Threshold value can be calculated using the same formula
that is used by TCCA; first it calculates the threshold for two
rounds as follows:
)3...(
0
min)...,...
2*
Re
)
1
mod(1
max(
)(
otherwise
GifST
MaxEng
mEng
P
RP
P
P
aST
If formula (3) is approved, then it is ready to become a CH for
two rounds. If formula (3) is not approved, the sensor will
calculate the formula (4) to see if it is able to become a CH for
only one round.
)4...(
,0
min)...,...
Re
)
1
mod(1
max(
)(
otherwise
GifST
MaxEng
mEng
P
RP
P
P
ST
Where P is the desired percentage of CHs, Tmin is a minimum
threshold (to avoid the possibility of remaining energy
shortage), and G is the set of sensors that have not became CHs
in 1/P round, MaxEng is the maximum energy that the sensor
could have, RemEng is the sensor remaining energy.
Each elected CH starts listing to the network; other sensors
start broadcasting their reports to their neighbors (using Carrier
sense multiple access protocol for transmission to avoid
collisions); this message consists of Sensor ID, report,
Requesting type tag (RT: 0 for request, 1 for approves), Time
to live (TTL: set to 1, broadcast to only direct neighbors),
packet request status tag (PR: 0 for the first packet, 1 for the
second packet). When ready sensors (CHs) receive the
messages, it saves each report with the node id temporarily in
its memory, and then it sends requests with confirmation to
those sensors indicating that it is ready to become their CH for
the current round, when formula3 applies, it also indicates that
it is also ready to be their CH for the next round; the message
contains: CH id, pairs of Sensor id with its time (to prevent
collisions and provide less delay), TTL (set to 1), RT (set to 1),
PR (set to 0) and the ability tag (AT: 0 for one round ability,
and 1 for two rounds ability). Sensors receive the message
form CHS; if they receive more than one request then they will
choose the one with the ability to become CH for two rounds,
AT=1 (here it will save the CH id to use it in the next round); if
they receive many requests with the same values, then they
pick the CH randomly; Sensors then reply to CHs with
confirmation; the message contains: Sensor id, CH id, and an
Acknowledgment tag (ACK: set to 1). When a CH receives the
confirmations it combines all the reports that it has in one
compressed report and forwards it to the B.S.; the message
contains: CH id, BS id and the aggregation report.
In the next round, sensors check first if they are group
members of a CH with an ability to handle two rounds, if they
are, then they use it for the current round (half transmission
round is applied); the sensor sends its report to its CH; the
message contains: Sensor id, CH id, PR (set to 1), TTL (set to
1), PR (set to 1). CH receives the reports, aggregate then in one
report, and then send them to the B.S., the message contains:
Ch id, B.S id, and the aggregation report; then the CH will
send acknowledgments to its members and remove them from
its memory; the acknowledgment message contains: Ch id,
Sensor id, and ACK (set to 1); sensors who receive the
acknowledgment then remove CH info from their memories.
In the case that the sensor does not have a CH from the
previous round, it will repeat the first scenario for full round
transmission.
B. Energy saving in Mod-LEACH
Mod-LEACH applies the same condition that has been
applied by TCCA for electing CHs by considering the
remaining energy of the sensors. At the same time, it
guarantees that every sensor will become a CH at least one
time per 1/P rounds, where P is the desired percentage of CHs.
These modifications provide the network with high energy
balance by distributing the energy among all sensors.
Mod-LEACH provides enhanced energy saving by dealing
with double round technique, where it saves almost half of the
energy used in one regular round; for the full transmission
round, it will consume more energy than LEACH and TCCA,
but it covers that gab in the next round, and even saves more
total energy than other protocols may save.
Mod-LEACH uses Time to live (TTL) tags to control the
cluster formation, where the broadcasting occurs only on the
direct neighbors; this leads to a more energy balanced network.
C. Security in Mod-LEACH
Mod-LEACH provides the same level of security that has
been provided by LEACH and TCCA, where it didn’t affect
the main idea of these protocols which is the dynamic rotation
of CHs around the network.
V. EXPERIMENTATION AND ANALYSIS
In this section, we discuss the numerical experimentation;
here we describe the chosen parameters groups for each
protocol, following the same scenario. The experiment is
applied on LEACH, TCCA, and Mod-LEACH protocols; we
applied them on three different network sizes (100, 1000, and
10000 sensors); for each size, 1000 rounds were processed
with the following initial values of main parameters:
- The desired percentage of CHs (P) is set to 0.05.
- Each sensor starts with 0.5 j energy.
- The amplifier energy is assumed to be 100 pj.
- The electronic energy is assumed to be 50 nj.
- Each sensor data range is set to 30m.
- The message size of a sensor data is set to 50 bits.
- Each node has 2000-bit data packet to send to the BS.
Next, we analyze the results that appeared from applying
our experiment on each of the protocols discussed before,
using the same initial values and following the same scenario.
We start with comparing the results based on energy saving
results from each protocol, and then we discuss them based on
data overload produced by each protocol, then we compare the
results based on the number of the dead sensors at the end of
the experiment for each protocol..
A. Energy saving
LEACH provides many techniques to save energy during
network communication; where it is a self-organization,
adaptive protocol and it uses randomization to evenly distribute
the energy load among the sensors in the network, in addition
to the random way that CHs rotate around the various sensors
which is reducing the possible draining of the battery for each
sensor. Also, performing a local data compression to compress
the amount of data being sent from clusters to BS reduces the
energy consumption and enhances the system lifetime. These
factors, in addition to the way that CHs change every cycle
provide LEACH with High energy saving. Mod-LEACH
applies the same factors to Sensor networks which provide it
with similar energy saving to the LEACH at this point.
Fig.2. Total energy consumption in LEACH, TCCA, and Mod-LEACH
after 1000 rounds for different network sizes (100, 1000, 10000).
TCCA adds additional factors to save energy; it uses Time
to live (TTL) tag to control the cluster formation, which leads
to gain more energy balance. It also uses the new condition
provided by TCCA to elect CHs each round, which results in
more energy control. [3] Shows that TCCA works almost three
times better than LEACH in energy saving. Mod-LEACH
applied TCCA factors, which means that it works three times
better than LEACH in energy saving. Now by applying the
new idea that we discussed before, we can notice that Mod-
LEACH provides the network with almost four times more
energy saving than what is provided by LEACH, and almost
double of that in TCCA.
Our experiment shows that the variation of energy
consumption is very small when network size is small (i.e. 100
sensors), but it varies more if we increase the network size.
Fig.2 shows that, for network size of 10,000 sensors, total
energy consumption is minimum in Mod-LEACH with almost
0.1X10
12
nj, then TCCA comes with energy consumption of
almost 1.2X10
12
nj at second place, and last comes LEACH
with 3.3X10
12
nj. The variation comes from the nature of how
Mod-LEACH works; using TTL, in addition to continuous
checking of residual energy of each sensor, gives Mod-
LEACH and TCCA protocols more energy balance for large
network size; working and double round technique provides
Mod-LEACH with more energy saving.
B. Data Overload
TCCA works with multi-hops clusters; this reduces
the number of clusters, which reduces the total transactions
required in network communications; this leads to highly
reduce data overload compared with LEACH. Mod-LEACH
has two different round types; in the full transmission round it
will produce more data overload than that produced by TCCA
and LEACH, but by applying the half transmission technique
on the next round, we balance the increase in the data in the
previous round and we provide less total data overload than
that provided in double rounds with LEACH and TCCA.
Our experiment shows that, for a large network size
(i.e. 10000 sensors); the total data overload is minimized using
Mod-LEACH. Fig.3 shows that with Mod-LEACH data
overload reaches almost 0.1X10
12
bits, where in TCCA it
reaches 2.2X10
12
bits and in LEACH it reaches 9.3X10
12
; this
shows that LEACH produces more data overload, almost nine
times more than the data overload produced by Mod-LEACH.
Moreover, TCCA produces more data overload, almost twice
as much data overload produced by Mod-LEACH.
C. Performance
Here, we analyze the performance based on the expected
Dead Nodes that may result in each solution after the same
number of rounds.
According to the energy saving analysis, we can figure out
that the number of Dead Nodes that may appear in LEACH
will be much higher than the number of dead nodes in Mod-
LEACH, where the number of Dead Nodes depends on the
energy consumption by the network.
Fig.4 shows that Mod-LEACH and TCCA remain
completely alive (i.e. no dead sensors) after 1000 rounds. On
the other hand, in the case of 10000 sensors network size
LEACH results in almost 2300 dead sensors.
VI. CONCLUSIONS
Modified-LEACH provides large sensor networks with
high energy saving, and high level of performance, more than
nine times better than LEACH and twice better than TCCA. At
the same time it produces a much higher level of network
stability than offered by LEACH. These results show that our
proposal provides an efficient solution for high performance
sensor networks communication.
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Fig.3. Total data overload in LEACH, TCCA, and Mod-LEACH after
1000 rounds for different network sizes (100, 1000, 10000).
Fig.4. Dead nodes occur in LEACH, TCCA, and Mod-LEACH after
1000 rounds, for different network sizes (100, 1000, 10000).
... Clusters are organized at the beginning of each round and data are transferred from the nodes to the cluster head and on to the base station after the set-up phase. As LEACH is a typical clustering protocol, several modifications have been made PEGASIS [7], LEACH-E [12], LEACH-D [13], Mod-LEACH [14], LEACH-E (ELE) [15] and HEEP [16]. ...
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We introduce TinySec, the first fully-implemented link layer security architecture for wireless sensor networks. In our design, we leverage recent lessons learned from design vulnerabilities in security protocols for other wireless networks such as 802.11b and GSM. Conventional security protocols tend to be conservative in their security guarantees, typically adding 16--32 bytes of overhead. With small memories, weak processors, limited energy, and 30 byte packets, sensor networks cannot afford this luxury. TinySec addresses these extreme resource constraints with careful design; we explore the tradeoffs among different cryptographic primitives and use the inherent sensor network limitations to our advantage when choosing parameters to find a sweet spot for security, packet overhead, and resource requirements. TinySec is portable to a variety of hardware and radio platforms. Our experimental results on a 36 node distributed sensor network application clearly demonstrate that software based link layer protocols are feasible and efficient, adding less than 10% energy, latency, and bandwidth overhead.
Conference Paper
A prerequisite for a secure communication between two nodes in an ad hoc network is that the nodes share a key to bootstrap their trust relationship. In this paper, we present a scalable and distributed protocol that enables two nodes to establish a pairwise shared key on the fly, without requiring the use of any on-line key distribution center. The design of our protocol is based on a novel combination of two techniques - probabilistic key sharing and threshold secret sharing. Our protocol is scalable since every node only needs to possess a small number of keys, independent of the network size, and it is computationally efficient because it only relies on symmetric key cryptography based operations. We show that a pairwise key established between two nodes using our protocol is secure against a collusion attack by up to a certain number of compromised nodes. We also show through a set of simulations that our protocol can be parameterized to meet the desired levels of performance, security and storage for the application under consideration.
Establishing Pairwise Keys for Secure Communication in Ad Hoc Networks: A Probabilistic ApproachICNP’03) Fig.3. Total data overload in LEACH, TCCA, and Mod-LEACH after 1000 rounds for different network sizes (100
  • Sencun Zhu
  • Shouhuai Xu
  • Sanjeev Setia
Sencun Zhu, Shouhuai Xu, Sanjeev Setia, and Sushil Jajodia. Establishing Pairwise Keys for Secure Communication in Ad Hoc Networks: A Probabilistic Approach. Proceedings of the 11th IEEE International Conference on Network Prot1ocols (ICNP’03) Fig.3. Total data overload in LEACH, TCCA, and Mod-LEACH after 1000 rounds for different network sizes (100, 1000, 10000). Fig.4. Dead nodes occur in LEACH, TCCA, and Mod-LEACH after 1000 rounds, for different network sizes (100, 1000, 10000).
Total data overload in LEACH, TCCA, and Mod-LEACH after 1000 rounds for different network sizes (100
  • Fig
Fig.3. Total data overload in LEACH, TCCA, and Mod-LEACH after 1000 rounds for different network sizes (100, 1000, 10000).