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In this paper, we propose an adaptive TDMA based MAC protocol, called Bitmap-assisted Shortest job first based MAC (BSMAC), for hierarchical Wireless Sensor Networks (WSNs). The main contribution of BS-MAC is that: (a) it uses small size time slots. (b) the number of those time slots is more than the number of member nodes. (c) Shortest Job First (SJF) algorithm to schedule time slots. (d) Short node address (1 Byte) to identify member nodes. First two contributions of BS-MAC handle adaptive traffic loads of all members in an efficient manner. The SJF algorithm reduces node’s job completion time and to minimize the average packet delay of nodes. The short node address reduces the control overhead and makes the proposed scheme an energy efficient. The simulation results verify that the proposed BS-MAC transmits more data with less delay and energy consumption compared to the existing MAC protocols.
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JOURNAL OF COMMUNICATIONS AND NETWORKS, VOL. 17, NO. 3, JUNE 2015 247
Enhanced TDMA based MAC Protocol for
Adaptive Data Control in Wireless Sensor Networks
Ahmad Naseem Alvi, Safdar Hussain Bouk, Syed Hassan Ahmed, Muhammad Azfar Yaqub,
Nadeem Javaid, and Dongkyun Kim
Abstract: In this paper, we propose an adaptive time division mul-
tiple access based medium access control (MAC) protocol, called
bitmap-assisted shortest job first based MAC (BS-MAC), for hier-
archical wireless sensor networks (WSNs). The main contribution
of BS-MAC is that: (a) It uses small size time slots. (b) The number
of those time slots is more than the number of member nodes. (c)
Shortest job first (SJF) algorithm to schedule time slots. (d) Short
node address (1 byte) to identify members nodes. First two contri-
butions of BS-MAC handle adaptive traffic loads of all members in
an efficient manner. The SJF algorithm reduces node’s job comple-
tion time and to minimize the average packet delay of nodes. The
short node address reduces the control overhead and makes the
proposed scheme an energy efficient. The simulation results verify
that the proposed BS-MAC transmits more data with less delay and
energy consumption compared to the existing MAC protocols.
Index Terms: Contention free, medium access control (MAC), time
division multiple access (TDMA), wireless sensor networks.
I. INTRODUCTION
WIRELESS sensor networks (WSNs) are used in wide va-
riety of applications like temperature, humidity, etc.
monitoring of such areas where human approach is almost
impossible. Military organizations are also very much inter-
ested in huge deployment of wireless networks for surveillance
and many tactical military applications [1]. Energy efficiency,
scalability, autonomous network operations, end-to-end delay,
throughput, and control overhead are some of the major WSN
constraints in these types of scenarios. In order to mitigate these
challenges, multiple medium access control (MAC) protocols
have been introduced. These MAC protocols are basically cat-
egorized into two main categories: (a) Contention based and
(b) scheduling based.
In contention based MAC Protocols, WSN node contend to
access the medium when it has data to send. Contention oc-
curs when more than one node wants to access same medium
in order to send their information. This increases the chances
Manuscript received May 30, 2013 approved for publication by Lee, Inkyu,
Division II Editor, March 8, 2015.
A. Naseem Alvi is with the Dept. of Electrical Engineering, COM-
SATS Institute of Information Technology, Islamabad, Pakistan,
email: naseem_alvi@comsats.edu.pk.
N. Javaid is with the Dept. of Computer Science, COMSAT In-
stitute of Information Technology, Islamabad, Pakistan, email: nadeem-
javaid@comsats.edu.pk.
S. H. Bouk, S. H. Ahmed, M. A. Yaqub, and D. Kim are with the School
of Computer Science and Engineering, Kyungpook National University, Daegu,
Republic of Korea, emails: {bouk, hassan, yaqub, dongkyun}@knu.ac.kr.
D. Kim is the corresponding author.
Digital object identifier 10.1109/JCN.2015.000046
of collisions, delay and causing more energy loss, which badly
decreases wireless node’s life span. In case of a dense WSN,
the number of collisions increases drastically and results in the
longer channel access delay. One of the standard for contention
based MAC protocols is IEEE 802.11 [2]. In this standard, en-
ergy consumption during idle listening mode is almost same as
in receiving mode. This idle listening energy consumption be-
comes more severe in a densely deployed network scenarios,
i.e. WSN [3]. That is why this standard is not recommended
for WSN. Sensor medium access control (SMAC) [4], Time-
out medium access control (TMAC) [5], Berkley medium ac-
cess control (BMAC) and utilization based duty cycle tuning
medium access control (UMAC) [6] are also contention based
MAC protocols designed for WSN. They adjust duty cycle for
efficient energy consumption.
WSNs are generally deployed in large numbers, therefore,
contention based MAC protocols are not suitable in such sce-
narios. On the other hand, in scheduled based MAC protocols,
there is no contention because all nodes are assigned a sepa-
rate guaranteed time slots (GTS), e.g., time division multiple
access (TDMA), to carry out communication. TDMA avoids in-
terference by offering time based scheduling for nodes to access
radio sub-channels. The variant of TDMA, called Energy effi-
cient TDMA (E-TDMA) [7], is proposed for the hierarchical
WSN, where whole network is divided into groups or clusters.
All nodes in that cluster send their information to the elected
cluster head (CH) by following E-TDMA. In E-TDMA, the CH
turn its Radio off to save energy when members have no data to
send. Though these protocols increase node’s life time by con-
serving its energy, however, they are not scalable due to limited
number of time slots that sometimes are insufficient in unpre-
dictable scalability of WSN.
Due to different transmission behavior and variations in traffic
loads, nodes do not have same volume of data to send. Even the
nodes with similar task have different data collection time and
transmitting time. To cope this adaptive data traffic load, dif-
ferent TDMA based MAC protocols have been proposed, e.g.,
bit-map-assisted (BMA) [8] and BMA with round robin (BMA-
RR) [9]. They utilize different scheduling schemes for alloca-
tion of the fixed time slots to the requesting member nodes. In
result, they conserve and re-allocate those unused time slots to
the nodes with large volume of data.
All the above discussed techniques overcome some of the
limitations of traditional TDMA, however, control overhead in-
creases in these schemes. The second issue in these schemes is
that the number of time slots are equal to the number of mem-
ber nodes. Due to these fixed number of time slots available in
a round, these techniques do not properly address the adaptive
1229-2370/15/$10.00 c
2015 KICS
248 JOURNAL OF COMMUNICATIONSAND NETWORKS, VOL. 17, NO. 3, JUNE 2015
traffic load problem. In result, it increases delay and reduces
throughput.
In this paper, we propose an adaptive TDMA based MAC pro-
tocol, called bitmap-assisted shortest job first based MAC (BS-
MAC), that: (1) Considers small size time slots and their number
is not equal to number of member nodes. This will help in han-
dling adaptive traffic loads of all members in an efficient man-
ner. (2) Shortest job first (SJF) algorithm is applied in order to
reduce node’s job completion time and to minimize the average
packet delay of nodes. (3) The size of control packet is reduced
by using short node address (1 byte instead of 8 bytes), which
reduces the control overhead and makes our proposed scheme
energy efficient.
Rest of the paper is organized as follows: Section II discusses
the previous work related to the proposed scheme. The proposed
TDMA based MAC protocol is described in Section III. Section
IV evaluates and compares the performance of the proposed BS-
MAC protocol with the existing ones. Finally, Section V con-
cludes the paper.
II. RELATED WORK
Energy conservation is one of the main objectives of the MAC
protocols. TDMA based MAC protocols are energy efficient as
they do not waste their energy due to collision such as in con-
tention based MAC protocols, e.g., carrier sense multiple ac-
cess with collision avoidance (CSMA/CA). Many MAC proto-
cols have been designed to achieve energy efficiency. In this
section, we briefly discuss the previous related work, e.g., con-
tention free or TDMA based MAC protocols for WSN [8]–[13].
The Chinese remainder theorem based MAC (CMAC) [10] is
one of the TDMA based MAC protocol proposed for the hier-
archical WSN architecture. The network coordinator (NC) are
selected to collect data from neighboring nodes and forward it
to the sink node. It uses Chinese remainder theorem to find out
the scheduled time slots for the associated nodes. When mem-
ber node(s) transmit data on regular basis, then each node is
allocated a time slot for data transmission on the basis of prime
and remainder sequence calculated from Chinese remainder the-
orem. CMAC reduces latency in a session, however, if a node
has no data to send, then its slot remains unused and other nodes
can not use these slots even if they have data to send.
In [11], TDMA based MAC protocol, called delay guaranteed
routing and MAC, is proposed specifically for the delay sensi-
tive applications in WSN. The deterministic delay is guaranteed
by reusing the allocated time slots. Wu et al. in [12] proposed a
TDMA based MAC protocol by applying Coloring Algorithm,
known as TDMA-CA. In TDMA-CA, different colors are allo-
cated to the conflicting nodes in network and separate time slots
are allocated to each color. Authors have compared the proposed
protocol with SMAC and shown that TDMA-CA outperforms in
terms of energy consumption and latency.
In [13], traffic pattern oblivious (TPO) scheduling scheme
based MAC protocol is proposed. Unlike traditional TDMA
scheduling, TPO is capable of continuous data collection with
dynamic traffic pattern in an efficient manner. It allows the gate-
way to determine data collection on the basis of traffic load.
The BMA [8] and BMA-RR [9]. These protocols introduce
Control
slots
Data slot
annoncement
period
Round
Session
Data slot
annoncement
period
Steady state phase
Data slots
Setup
phase
Control
slots
CH_ANN
JOIN_REQ
CS_ALLOC
...
Fig. 1. One round in a cluster.
varying scheduling techniques to efficiently allocate fixed time
slots. The BMA MAC protocol allocates fixed duration time
slots to the requesting nodes only and the other nodes are not
assigned any time slot at all. In result, BMA conserves time
slots and those slots may be allocated to the nodes with large
volume of data. The BMA method was improved in [9] by in-
troducing Round Robin scheduling technique, named BMA-RR,
to assign time slots to the requesting nodes. Though these tech-
niques overcome some of the limitations of traditional TDMA,
however, control overhead increases in these schemes. The sec-
ond issue in these schemes is that the number of time slots are
equal to the number of member nodes. Due to fixed number of
time slots available in a round, these techniques do not properly
address the adaptive traffic load problem. As a result, it increases
delay and reduces throughput.
Most of the research work has been focused on energy con-
servation of wireless nodes and to increase the life time of a
WSN. However, in this work, we have focused on the overall
performance of a WSN in terms of energy, throughput and trans-
mission latency. The following section discusses our proposed
scheme in detail.
III. PROPOSED BS-MAC PROTOCOL
We propose a TDMA based MAC protocol, called bitmap-
assisted shortest job first based MAC (BS-MAC), for cluster
based or hierarchical communication scenarios in WSN.
Various clustering techniques are proposed for efficient rout-
ing between wireless nodes and sink in a WSN [14]. Those
schemes divide WSN in different groups, called clusters. In each
cluster, a node is elected as a CH and all the other nodes join that
CH and act as member nodes. The members of that cluster com-
municate with the sink node through their respective CH. In a
cluster setup phase, wireless nodes are organized in a cluster.
Each node at the start of new round decides whether it will be-
come CH for this round or not. This decision is based on the
stochastic algorithm. The probability of each node to become
a CH is 1/p, where pis the desired percentage of CHs. Once
the node becomes CH, it will not be selected as a CH until rest
of the nodes in that cluster become CHs. After successful selec-
tion of a CH, the CH starts communication round(s). Each round
comprises of a setup phase (SP) and steady state phase (SSP),
as shown in Fig. 1. The SSP is further divided into multiple ses-
sions. Following is a brief discussion related to each section of
a round.
ALVI et al.: ENHANCED TDMA BASED MAC PROTOCOL FOR ADAPTIVE... 249
Frame
control
CH short
address
Node1's
extended
address
Node1's
short
address
Node1's
control
slot (s1)
Node2's
extended
address
Node2's
control
slot (s2)
Node2's
short
address
. . . . . . . . . . . Control slot
duration (d)FCS
Start of data slot
announcement
period
Noden's
control
slot (sn)
Noden's
short
address
Fig. 2. CS_ALLOC message format.
A. Setup Phase (SP)
The SP immediately starts after successful selection of a CH.
Following steps will take place during the SP.
1. CH broadcasts CH Announcement (CH_ANN) message.
CH_ANN message starts with control portion (1 byte) along
with CH’s extended address (8 bytes) and frame check se-
quence (FCS) (2 bytes) as redundant bits. Total length of a
CH_ANN message is 11 bytes.
2. Nodes in the range of CH, listens to CH_ANN and replies
with the join request (JOIN_REQ) message to CH. This
JOIN_REQ includes a control byte, Node’s extended address
(8 bytes), CH’s extended address, and FCS. Hence, the size of
a JOIN_REQ is 19 bytes.
3. CH waits for a specific time period to receive JOIN_REQs
from all nodes within its communication range.
4. CH calculates the total number of member nodes by counting
the received JOIN_REQs and allocates a control slot to each
node.
5. A unique 1 byte short address is computed by a CH for
all the associated members and for itself. Therefore, max-
imum 255 nodes can be associated with single CH. After-
ward, CH allocates separate control slot to each member node
and broadcasts the allocated control slot information to all its
members through CS_ALLOC message, as shown in Fig. 2.
CS_ALLOC message mainly consists of control byte, CH’s
extended and short address, nodei’s extended and short ad-
dress, nodei’s allocated control slot number, si, start time of
data slot announcement period and FCS. The detailed flow di-
agram of setup phase is shown in Fig. 3.
B. Steady State Phase (SSP)
After successful completion of the SP, steady state phase
starts immediately with control slots where source nodes (data
sending member nodes) send their DATA_REQ messages dur-
ing their allocated control slots. Detailed flow diagram of SSP
is shown in Fig. 4. DATA_REQ mainly consists the number of
requested slots by the source node. The non-requesting mem-
ber nodes (having no data to send,) keep their radios off in or-
der to save energy. However, the CH remains in receiving mode
during the entire control period in order to receive DATA_REQ
messages from all source nodes. After completion of control pe-
riod, CH computes number of DATA_REQ messages (requesting
nodes) and has complete information about the total number of
data slots requested by source nodes. CH applies SJF algorithm
and informs all source nodes about their allocated data slots
by broadcasting allocated data slot announcement (ADS_ANN)
frame, as shown in Fig. 5. The SJF algorithm for data slot allo-
Receive CH_ANN
messages
Send JOIN_REQ to
nearby CH
Broadcast CH_ANN
message
Announce
CS_ALLOC
message
Turn Rx On
Wait for JOIN_REQ
messages from
nodes
Is node CH
Turn Tx On
Yes
Turn Rx Off
Allocate control slot
to all joined nodes
(members)
Turn Rx OQ
No
Turn Tx OQ
Recv. CS_ALLOC
message and
calculate allocated
slot
Turn Tx OQ
Enter in the steady state phase
Fig. 3. Setup phase communication flow diagram between CH and member
node.
cation is briefly discussed in the next section. If the total number
of requested data slots is more than the total number of available
slots, then some of the nodes will not be entertained during that
session. If a node wants to send data to its neighboring node then
in first session, node sends the data to CH and then during next
session that data is transmitted to the receiving node.
The ADS_ANN message comprise of each source node’s
short address along with its allocated starting time slot and in-
formation of the next control period start time. Therefore, all
member nodes have knowledge about their control slot in the
next session also.
C. Shortest Job First (SJF) Algorithm
In our proposed BS-MAC, allocation of data slots to the
source nodes are prioritized on the basis of SJF algorithm. In
SJF algorithm, nodes with less number of data slot requests are
prioritized over nodes that require more data slots. If two or
more nodes have requested for the same number of data slots,
then the priority will be given to a node with smaller short ad-
dress among the requesting nodes. The reason to adopt SJF in-
stead of round robin is that in round robin mechanism source
node(s) that require more than one time slot for data transmis-
sion has/have to wait for longer time to send their data to CH,
as described in BMA-RR [9]. In addition to the increased delay,
the source node(s) also consume extra energy by toggling their
radios between Off and On states. On the other hand, the SJF
technique saves energy by avoiding this radio toggling. Further-
more, average data transmission time (the average total duration
250 JOURNAL OF COMMUNICATIONSAND NETWORKS, VOL. 17, NO. 3, JUNE 2015
Start
Wait for allocated
control slot
Wait for
announcement
period
Send data req. to
CH
Turn Tx Off
Turn Rx On to
receive
announcement
Turn radio Off
Turn On Rx to
receive data
Receive /
transmit data
Data to send
Information
for node
Turn Tx On
Yes
Yes
No
No
Receive
Transmit
Sleep till allocated
slot
Receive at its
allocated slot
Turn On Tx to
Transmit data
Sleep till allocated
slot
Transmit at its
allocated slot
Fig. 4. Steady State Phase (SSP) communication
Fig. 4. SSP communication flow diagram of a member node.
Frame
control
Node1's
short
address
Node1's
starting
slot
Node2's
short
address
Node2's
starting
slot
FCS
Start of next
session/control
period
Noden's
starting
slot (sn)
Noden's
short
address
. . . . . . . . . . .
Fig. 5. ADS_ANN message format.
between start and end of data transmission) of source nodes is
faster than Round Robin, as shown in Table 1. We have com-
pared SJF with RR by considering 5 source nodes requiring dif-
ferent data slots. It is evident from the results that the nodes with
SJF complete their data transmission quickly than the RR.
Table 1. Comparison between SJF and round robin algorithm.
Node Data slots re-
quested
Slots/job
in SJF
Slots/job in
RR
Job completion ratio
(SJF vs. RR)
A 2 2 6 1:3
B 3 5 11 1:2.2
C 4 9 15 1:1.66
D 4 13 15 1:1.15
E 5 18 18 1:1
D. Slot Duration
Previous TDMA based schemes allocate fixed length data slot
to source nodes and each data slot is of longer time duration.
For efficient use of time slots, the slot duration is kept smaller
as compared to traditional TDMA based schemes. Shorter time
slots will be helpful in order to minimize unused time slots and
consequently helps in minimizing unnecessary wait duration for
other source nodes. Table 2 shows comparison between BMA-
RR and our proposed BS-MAC protocol in terms of excessive
delay calculation when nodes want to generate random data. It
also shows that by introducing shorter data slots, as in proposed
BS-MAC, nodes save substantial time as compared to larger data
slots used in BMA-RR. As CH has to keep its radio in the re-
ceiving state throughout these data slots, therefore, the smaller
length of data slots save significant amount of energy, which
further improves the throughput.
CH informs all source nodes about their allocated data slots
with starting slot number by sending DSA_ANN message. If
there is no request for slot allocation by any source node, then
DSA_ANN contains only the start time information of next con-
trol period. On the other hand, the control slot sequence remains
same throughout the round. As all control slots are of same
length, as informed by CH during the setup phase, hence, mem-
ber nodes only need to know start of the next control period to
compute their control slot as well as start time of the next data
slot announcement period.
E. Energy Consumption during SP
Total energy consumption during setup phase in Nsize clus-
ter (ESetup )is sum of energy consumed by CH and its as-
sociated (N1) member nodes. Energy consumed by a CH
comprises of energy consumption during Active and Idle states.
(ESP Active
ch )is the energy consumed by a CH in active mode
during setup phase and is calculated as:
ESP Active
ch =PAT
ch ×TAT +PJR
ch ×TJR ×(N1)+PCS
ch ×TCS
(1)
where PAT
ch ,PJR
ch , and PCS
ch are the power consumed by the CH
for transmitting the CH_ANN, receiving JOIN_REQ and trans-
mitting the CS_ALLOC message to all member nodes, respec-
tively. The TAT ,TJ R, and TCS are the time required to send
CH_ANN, receive JOIN_REQ and send CS_ALLOC messages,
respectively. In same state, the energy consumed by a member
node m,ESP Active
m, where m(N1), is calculated as:
ESP Active
m=PAT
m×TAT +PJR
m×TJR +PC S
m×TCS (2)
where PAT
m,PJR
m, and PC S
mare the power consumed by a mem-
ber node for receiving CH_ANN, sending JOIN_REQ and re-
ceiving CS_ALLOC messages, respectively.
There are (N1) member nodes in a cluster and energy con-
sumed by all member nodes in active mode, (ESP Activ e
am ), is
computed as in (3).
ESP Active
am =
N1
X
i=1
Ei.(3)
During SP, some of the energy also consumed when CH and
member nodes are in idle listening mode. If PS P Idle
ch is the
power consumed by CH during idle state as it has to keep its re-
ceiver ON in order to receive member node’s JOIN_REQ mes-
sages and TSP I dle
ch is the time for idle period, then total energy
ALVI et al.: ENHANCED TDMA BASED MAC PROTOCOL FOR ADAPTIVE... 251
Table 2. Comparison of data transmission delay between proposed BS-MAC and BMA-RR based MAC protocol.
Node Data
length
(bytes)
Data rate
(bps)
Time
to send
data
(ms)
Bits/slot
in
BMA-
RR
Slot
length in
BMA-RR
MAC(ms)
Slots
re-
quired
Time required
to send data
in BMA-RR
(ms)
Bits/slot
in BS-
MAC
Slot
length
in BS-
MAC
Slots
re-
quired
Time required
to send data in
BS-MAC (ms)
Time
lapsed in
BMA-RR
(ms)
Tme
lapsed in
BS-MAC
(ms)
A 120 24,000 40 2,000 83.33 1 83.33 200 8.33 5 41.67 43.33 1.67
B 180 24,000 60 2,000 83.33 1 83.33 200 8.33 8 66.67 23.33 6.67
C 210 24,000 70 2,000 83.33 1 83.33 200 8.33 9 75.00 13.33 5.00
D 240 24,000 80 2,000 83.33 1 83.33 200 8.33 10 83.33 3.33 3.33
E 280 24,000 93.33 2,000 83.33 2 166.67 200 8.33 12 100.0 73.33 6.67
consumed by CH during idle period in SP (ES P Idle
ch )is calcu-
lated as:
ESP I dle
ch =PIdle
ch ×TSP I dle
ch .(4)
All member nodes after sending JOIN_REQ messages keep
their radios ON and wait to receive CH’s CS_ALLOC mes-
sage. Member nodes in idle mode also wait to receive CH_ANN
message from CH in the beginning of the SP, as shown in
Fig. 3. If a member node mconsumes PS P Idle
mpower and
has TSP I dle
midle listening period, then the overall energy con-
sumption of a member node mduring idle listening period in
SP, i.e., ES P Idle
m, is computed as:
ESP I dle
m=PSP I dle
m×TSP I dle
m.(5)
Total energy consumed by (N1) member nodes during idle
mode in SP, i.e., ESP Idle
am , is calculated as:
ESP I dle
am =
N1
X
i=1
ESP I dle
i.(6)
Total energy consumption in a cluster during setup phase, i.e.,
ESetup , is computed as in (7):
ESetup =ESP Activ e
ch +ESP Active
am +ESP I dle
ch +ESP I dle
am .
(7)
F. Energy Consumption during SSP
In a single round, there is one SP and one SSP. A SSP com-
prises of multiple sessions and each session starts with control
period followed by data slot allocation period and dedicated data
slots for communication. In session j, source node(s) send their
data request(s), DATA_REQ message(s), during their allocated
control slot, whereas all the other nodes keep their radios off to
save energy. Energy consumed by a source node sduring con-
trol period in session j, i.e., ECPj
s, is calculated as:
ECPj
s=PCPj
s×Ts(8)
where PCPj
sis power consumed during transmitting DATA_REQ
message and Tsis the control slot duration in session j.
CH in that control slot period always remains in receiving
mode to receive DATA_REQ messages. If there are xnumber
of source nodes, then the energy consumption during complete
control period, i.e., EC Pj, is computed as:
ECPj=EC Pj
s×x+ (N1x)×PCP I dlej
ch ×Ts
+x×PCP Rxj
ch ×Ts.(9)
Here, PCP I dlej
ch is power consumed by CH during idle listen-
ing in the control period and PC P Rxj
ch is power consumed in
receiving DATA_REQ message during control period by CH.
Control period is followed by data slots allocation period in
which CH announces data slots allocation information to all
member nodes, ADS_ANN message, in the cluster along with
starting of next control period. Total energy consumed during
data slots allocation period in session j, i.e., EAD Sj, is calcu-
lated as:
EADSj=PADSj
ch ×TADSj+
N1
X
i=1
PADSRxj
i×TADSj(10)
where PADSj
ch is power consumed by a CH in transmitting
ADS_ANN message, PDS ARx
iis power consumed by node
ito receive that message, and TADSjdenotes the time required
to send and receive ADS_ANN message during session j.
Next, we calculate the energy consumed by all member nodes
to transmit data in session j, i.e., ED Tj, as in (11).
EDTj=
N1
X
i=1
PDTj
i×k×TDS (11)
where k,PDTj
i, and TDS are number of time slots used by
source node ito transmit data, power consumed to transmit data
and duration of a single data slot in session j, respectively.
Energy consumed by a CH in receiving all data packets, i.e.,
EDTj
ch , from source nodes during same session is computed as:
EDTj
ch =PDRj
ch ×k×TDS (12)
where PDRj
ch is power consumed by CH in receiving data pack-
ets from all source nodes during session j. Therefore, the overall
energy consumption during session j, i.e., ES teady
j, is:
ESteady
j=ECPj+EADSj+ED Tj+EDTj
ch .(13)
If there are nsteady state sessions in a round, then the total
energy consumed during SSP is:
ESteady =
n
X
l=1
ESteady
l.(14)
Total energy consumed in a cluster is sum of energy con-
sumed in SP as well as in SSP and is computed as:
Etotal =ESetup +ESteady .(15)
252 JOURNAL OF COMMUNICATIONSAND NETWORKS, VOL. 17, NO. 3, JUNE 2015
Table 3. Simulation parameters.
Parameters BS-MAC BMA-RR E-TDMA
Data rate (bps) 24,000 24,000 24,000
Control packet size (bits) 32 144 1
Control slot length (s) 0.00133 0.006 0.00004166
Data slot length (s) 0.0083 0.083 0.083
Transmitting energy (nJ) 50 50 50
Receiving energy (nJ) 50 50 50
Idle energy (nJ) 5 5 5
IV. SIMULATION ANALYSIS
This section discusses the simulation analysis of our pro-
posed BS-MAC protocol in contrast with the BMA-RR [9] and
E-TDMA [7] that are considered as conventional schemes. As
we discussed that our proposed BS-MAC protocol improves
throughput, minimizes delay and increases energy efficiency of
the whole network. In order to evaluate the effectiveness of the
proposed BS-MAC protocol, we compared throughput, energy
efficiency and delay with E-TDMA and BMA-RR, through sim-
ulations. During simulations, we considered the network with
cluster of size Nnodes, among them one node acts as CH and
rest as member nodes. These nodes are deployed in an area of
100 ×100 m2. Probability Pis set on the basis of nodes having
data requests e.g., if P= 0.1, then only one out of 10 mem-
ber nodes require to send data. Random data traffic is generated
by the data requesting nodes within the range of 0.175 KB to
2.875 KB. The data slots are varied and are analyzed for 4 and
6 steady state sessions.
The impact of varying cluster size is analyzed for the clus-
ter of 11, 21, and 31 nodes, where one node acts as CH and
remaining are member nodes. Transmitted data along with en-
ergy consumption and average transmitted delay are analyzed
for three sessions. Rest of the simulation parameters are shown
in Table 3.
A. Transmitted Data
The transmitted data is calculated as amount of data sent from
source to the destination node successfully. Figs. 6 and 7 show
the transmitted data for varying probability (p) and sessions, re-
spectively. It is evident from the results that BS-MAC transmits
data prior to E-TDMA and BMA-RR. In Fig. 6, for 2 and 4
sessions, it is observed that BS-MAC transmits more data com-
pared to the BMA-RR and E-TDMA when number of source
nodes increases. However, when pincreases from 0.6 and 0.8,
then BS-MAC does not send more data because all data slots are
occupied, for 2 and 4 sessions, respectively. In Fig. 7, the sim-
ilar increase in transmitted data is observed. It also shows that
BS-MAC outperforms the other two MAC protocols in terms of
data transmitted in first 2 for p= 0.4and 3 sessions for p= 0.6.
In order to further validate our results, we analyzed its perfor-
mance for network with cluster size of 11, 21, and 31 nodes.
Fig. 8 shows that BS-MAC transmits more data as compared to
other two protocols for cluster of 11, 21, and 31 nodes. Simi-
larly, it is evident from the results that BS-MAC transmits more
data compared to the other two protocols for varying cluster size.
It is noticed that average improvement in transmitted data by
BS-MAC is 3% and 35.4% for 2 sessions and 4.3% and 16.3%
for 4 sessions, refer Fig. 6. This significant improvement in
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0
10
20
30
40
50
60
70
80
Probability (p)
Data Wransmitted (Kbits)
BS−MAC (2 sessions)
BS−MAC (4 sessions)
BMA−RR (2 sessions)
BMA−RR (4 sessions)
E−TDMA (2 sessions)
E−TDMA (4 sessions)
Fig. 6. Transmitted data versus probability (p) for 2 and 4 sessions.
0123456
0
10
20
30
40
50
Sessions
Data Wransmitted (Kbits)
BS−MAC (p=0.4)
BS−MAC (p=0.6)
BMA−RR (p=0.4)
BMA−RR (p=0.6)
E−TDMA (p=0.4)
E−TDMA (p=0.6)
Fig. 7. Transmitted data versus session for p= 0.4and 0.6.
0 0.1 0.2 0.3 0.4 0.6 0.7 0.8 0.9 1
0
20
40
60
80
100
120
140
160
180
0.5
Data Wransmitted (Kbits)
BS−MAC (11 Qodes)
BS−MAC (21 Qodes)
BS−MAC (31 Qodes)
BMA−RR (11 Qodes)
BMA−RR (21 Qodes)
BMA−RR (31 Qodes)
E−TDMA (11 Qodes)
E−TDMA (21 QRGHV)
E−TDMA QRGHV
Probability (p)
Fig. 8. Transmitted data of 11, 21, and 31 nodes versus pfor 3 sessions.
transmitted data by BS-MAC is due to the selection of smaller
data slots, which can accommodate different data requirements
effectively. Whereas, in other two TDMA based MACprotocols,
larger data slots are used that cannot accommodate adaptive data
traffic requirements efficiently.
B. Total Energy Consumption
Energy efficiency of sensor nodes is required to increase life
time of a WSN. Total energy consumption versus probability
and sessions are shown in Figs. 9 and 10, respectively. It is ev-
ident from the figures that BS-MAC, while transmitting same
amount of data, consumes less energy as compared to other two
MAC protocols. It is evident from Fig. 9 that BS-MAC con-
sumes less energy throughout 2 sessions. However, for 4 ses-
sions, BS-MAC consumes less energy when p= 0.8and con-
sumes more energy when p > 0.8. This is due to the increase
in amount of data transmitted during that period. On the other
hand, E-TDMA consumes less energy compared to the proposed
ALVI et al.: ENHANCED TDMA BASED MAC PROTOCOL FOR ADAPTIVE... 253
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0
2
4
6
8
10
12
Probability (p)
Energy Fonsumption (mJ)
BS−MAC (2 Vessions)
BS−MAC (4 Vessions)
BMA−RR (2 Vessions)
BMA−RR (4 Vessions)
E−TDMA (2 Vessions)
E−TDMA (4 Vessions)
Fig. 9. Energy consumption of the cluster size versus pfor 2 and 4 sessions.
0123456
0
1
2
3
4
5
6
Sessions
Energy Fonsumption (mJ)
BS−MAC (p=0.4)
BS−MAC (p=0.6)
BMA−RR (p=0.4)
BMA−RR (p=0.6)
E−TDMA (p=0.4)
E−TDMA (p=0.6)
Fig. 10. Energy consumption of the cluster versus sessions for p= 0.4and
0.6.
0 0.1 0.2 0.3 0.4 0.6 0.7 0.8 0.9 1
0
5
10
15
20
25
30
35
0.5
Energy Fonsumption / session (mJ)
BS−MAC (11 Qodes)
BS−MAC (21 Qodes)
BS−MAC (31 Qodes)
BMA−RR (11 Qodes)
BMA−RR (21 Qodes)
BMA−RR (31 Qodes)
E−TDMA (11 Qodes)
E−TDMA (21 Qodes)
E−TDMA (31 Qodes)
3UREDELOLW\S
Fig. 11. Energy consumption of 11, 21, and 31 nodes cluster versus pfor 3
sessions.
MAC protocol as well as BMA-RR. It is only because it fails to
transmit more data compared to both the protocols. The similar
behavior is also observed in Fig. 10.
To further validate our results we analyzed energy consump-
tion of BS-MAC with other two TDMA based MAC protocols
for varying cluster size. It is evident from the results shown
in Fig. 11 that BS-MAC consumes less amount of energy for
N= 11, 21, and 31 while transmitting same amount of data,
however energy consumption increases with the increase in
probability. This is because of larger amount of data transmitted
in BS-MAC.
C. Transmission Delay
Transmission delay of a node is calculated from the time
when node has a data request till the time it sends all of its
data to the destination successfully. Figs. 12 and 13 show the
transmission delay versus pand session, respectively. Unlikely,
0 0.1 0.2 0.3 0.4 0.6 0.7 0.8 0.9 1
0
5
10
15
20
25
30
0.5
Average Gelay (s)
BS−MAC (2 Vessions)
BS−MAC (4 Vessions)
BMA−RR (2 Vessions)
BMA−RR (4 Vessions)
E−TDMA (2 Vessions)
E−TDMA (4 Vessions)
3UREDELOLW\S
Fig. 12. Transmission delay of the cluster versus pfor 2 and 4 sessions.
0123456
0
5
10
15
20
Sessions
Average Gelay (s)
BS−MAC (p=0.4)
BS−MAC (p=0.6)
BMA−RR (p=0.4)
BMA−RR (p=0.6)
E−TDMA (p=0.4)
E−TDMA (p=0.6)
Fig. 13. Transmission delay of the cluster versus sessions for p= 0.4and 0.6.
0 0.1 0.2 0.3 0.4 0.6 0.7 0.8 0.9 1
0
10
20
30
40
50
60
70
80
90
0.5
Average Gelay (s)
BS−MAC (11 Qodes)
BS−MAC (21 Qodes)
BS−MAC (31 Qodes)
BMA−RR (11 Qodes)
BMA−RR (21 Qodes)
BMA−RR (31 Qodes)
E−TDMA (11 Qodes)
E−TDMA (21 Qodes)
E−TDMA (31 Qodes)
3UREDELOLW\S
Fig. 14. Transmission delay of 11, 21, and 31 nodes cluster versus pfor 3
sessions.
in BMA-RR and E-TDMA, the BS-MAC has significantly less
transmission delay. This is due to the implication of SJF algo-
rithm as nodes transmit their data at once instead of transmit-
ting in parts. This results in avoiding nodes to keep data in their
buffer for longer time, as shown in Table 1. Smaller slot length
further improves the network delay, as shown in Table 2. The
same trend is observed for cluster size of 11, 21, and 31 nodes.
Results shown in Fig. 14 verify that average transmission delay
of BS-MAC for 31 nodes is even smaller than 10 nodes of other
two TDMA schemes.
The results in Fig. 12 show that average transmission delay
of the network is minimized by BS-MAC up to 72% and 79%
for 2 sessions and 80% and 85% for 4 sessions, compared to
BMA-RR and E-TDMA, respectively. Similar amount of delay
has been reduced by the BS-MAC for varying sessions as shown
in Fig. 13.
254 JOURNAL OF COMMUNICATIONSAND NETWORKS, VOL. 17, NO. 3, JUNE 2015
V. CONCLUSION
In this work, we proposed TDMA based MAC protocol,
called BS-MAC that adaptively handles the varying amount of
data traffic by using large number of small size data slots. In ad-
dition, it implements SJF algorithm to reduce node’s job com-
pletion time that results in significant improvement in average
packet delay of nodes. The control overhead and energy con-
sumption is also minimized by introducing the 1 byte short ad-
dress to identify the member nodes. The performance of the pro-
posed BS-MAC protocol is compared with the BMA-RR and E-
TDMA through simulations. It shows that BS-MAC achieves
more than 70% and 80% efficiency in data transmission de-
lay and more than 3% and 17% data is transmitted compared
to BMA-RR and E-TDMA without compromising energy con-
sumption.
ACKNOWLEDGMENT
This work was supported by Defense Acquisition Program
Administration and Agency for Defense Development under the
contract UD130007DD.
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Ahmad Naseem Alvi was born in Gujarnwala, Pun-
jab, Pakistan in 1972. He received his B.S. degree
in Electronics Engineering from NED University,
Karachi, Pakistan in 1996. Afterwards, he served Tele-
com and IT industry in Pakistan for more than 10
years. Mr. Alvi completed his Masters in Computer
Systems Engineering from Halmstad University, Swe-
den in 2009. Currently he is pursuing his Ph.D. and
also serving as an Assistant Professor in the Depart-
ment of Electrical Engineering at COMSATS Institute
of Information Technology, Islamabad, Pakistan. His
research interests include wireless ad-hoc and sensor networks.
Safdar Hussain Bouk was born in Larkana, Pak-
istan in 1977. He received the B.S. degree in Com-
puter Systems from Mehran University of Engineer-
ing and Technology, Jamshoro, Pakistan, in 2001 and
M.S. and Ph.D. in Engineering from the Department
of Information and Computer Science, Keio Univer-
sity, Yokohama, Japan in 2007 and 2010, respectively.
Currently he is a working as a Postdoctoral Fellowship
at Kyungpook National University, Daegu, Korea. His
research interests include wireless ad-hoc, sensor net-
works, underwater sensor networks, and information
centric networks.
Syed Hassan Ahmed did his B.S. in Computer Sci-
ence from Kohat University of Science and Technol-
ogy (KUST), Kohat, Pakistan in 2012. Later on, he
joined School of Computer Science and Engineer-
ing, Kyungpook National University, Korea, where he
completed his M.S. in Computer Engineering in 2014.
During his B.S. and M.S., he published 20+ interna-
tional journal and conference papers in multiple topics
of wireless communication. Currently he is pursuing
his Ph.D. in Computer Engineering at MoNeT Lab,
Kyungpook National University, Korea. He is also an
IEEE/ACM Member and serving several conferences and journals as a TPC and
Reviewer, respectively. In 2014 and 2015, he won the successive Gold and Top
Contributor awards in the 2nd and 3rd KNU workshop for future researchers,
South Korea. His research interests include WSN, underwater WSN, cyber
physical systems, VANETs, and CCN in vehicular communications.
Muhammad Azfar Yaqub was born in Islamabad,
Pakistan in 1985. He received the B.S. degree in Elec-
trical (Telecommunication) Engineering from COM-
SATS Institute of Information Technology, Islamabad,
Pakistan in 2007 and M.S. in Mobile Broadband Com-
munications from the Lancaster University, United
Kingdom in 2010. Currently he is pursuing his Ph.D.
in Computer Engineering at MoNeT Lab, Kyungpook
National University, Korea. He is also an IEEE mem-
ber. His research interests include wireless ad-hoc,
sensor networks, and vehicular networks.
Nadeem Javaid received the Ph.D. degree from the
University of Paris-Est, Paris, France, in 2010, and
the master’s degree from Quaid-I-Azam University,
Islamabad, Pakistan. He is currently working as an
Assistant Professor, and founding head of the Com-
Sense Research Group at the Department of Computer
Science, COMSATS Institute of Information Technol-
ogy, Islamabad. His research interests include ad hoc
networks, vehicular ad hoc networks, body area net-
works, underwater wireless sensor networks, and en-
ergy management in smart grids. He is serving as Edi-
torial Board Member, and a Organizer/TPC Member of several conferences. He
ALVI et al.: ENHANCED TDMA BASED MAC PROTOCOL FOR ADAPTIVE... 255
has authored more than 250 research articles in reputed international journals
and conferences, supervised 40 master thesis students, and is supervising/co-
supervising 9 Ph.D. students.
Dongkyun Kin is a Professor with the Department
of Computer Engineering, Kyungpook National Uni-
versity, Daegu, Korea. He received the B.S. degree at
Kyungpook National University. He pursued his M.S.
and Ph.D. degrees at Seoul National University, Ko-
rea. He was a visiting researcher at Georgia Institute
of Technology, Atlanta, GA, USA. He also performed
a post-doctorate program at University of California,
Santa Cruz. He has been a TPC member of several
IEEE conferences. He received the Best Paper Award
from the Korean Federation of Science and Technol-
ogy Societies, 2002. His research interests are ad-hoc network, sensor network,
and wireless LAN, etc.
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