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On Energy Efficient Cooperative Routing in Wireless Body Area Network

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Energy efficient and reliable communication is extremely crucial in most of the applications of Wireless Body Area Networks (WBANs). Communication between sensor nodes is the major cause of energy consumption that limits the network lifetime, and hence, disrupts WBAN's operation. Moreover, unreliability in wireless communication caused by the channel impairments, such as shadowing and fading, further exacerbate the situation. In this thesis, we investigate a multi-hop and three cooperative routing schemes to improve Energy Efficiency (EE) and reliability of WBANs. Firstly, we propose a protocol; Critical data transmission in Emergency with Mobility support in WBANs (CEMob), which utilizes both single-hop and multi-hop communication modes and avoids continuous data transmission to preserve energy of sensor nodes. Performance comparison of CEMob is made with contemporary routing protocols, Adaptive Threshold based Thermal-aware Energy-efficient Multi-hop ProTocol (ATTEMPT) and Reliability Enhanced-Adaptive Threshold based Thermal-unaware Energy-efficient Multi-hop ProTocol (RE-ATTEMPT). Simulation results show that CEMob is 71% and 55% more energy efficient than ATTEMPT and RE-ATTEMPT, respectively. Later on, to improve the achieved throughput by CEMob, we introduce the concept of cooperative routing in Cooperative Critical data transmission in Emergency for Static WBANs (Co-CEStat). In this protocol, network throughput is enhanced by propagating independent signal through different paths. Simulation results reveal that Co-CEStat has 51% and 52% more throughput than its counterpart protocols, RE-CEStat (static CEMob) and RE-ATTEMPT, respectively. Availability of multiple links, for the propagation of same data, increases reliability of network at the cost of extra energy consumption by cooperative nodes. To improve EE and Packet Error Rate (PER) of Co-CEStat, we further analyze incremental cooperative communication schemes with different number of relays. We propose a new incremental cooperative communication scheme with 3- stage relaying and compare it with already existing incremental cooperative schemes in literature. Taking into account the effect of PER, analytical expressions for EE of proposed 3-stage cooperative communication scheme are also derived. Our proposed scheme proves to be more reliable with less PER at the cost of some extra energy consumption. In the last, 3-stage incremental relaying and contemporary 2-stage incremental relaying schemes are implemented in two routing protocols; Incremental Cooperative Critical data transmission in Emergency for Static WBANs (InCo-CEStat) and Enhanced InCo-CEStat (EInCo-CEStat), respectively. Simulation results of incremental cooperative protocols are compared with Co-CEStat and it is observed that incremental cooperation is more energy efficient than cooperation approach utilized in Co-CEStat. Results also reveal that EInCo-CEStat proves to be more reliable than InCo-CEStat with 12% more throughput and has less PER by providing three redundant links for a source node. Whereas, InCo-CEStat proves to be more energy efficient with 24% more stability period than EInCo-CEStat, by utilizing two cooperative links for a single source node.
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On Energy Efficient Cooperative Routing
in Wireless Body Area Network
By
Ms. Sidrah Yousaf
CIIT/FA12-REE-039/ISB
MS Thesis
In
Electrical Engineering
COMSATS Institute of Information Technology
Islamabad Pakistan
Fall, 2014
ii
On Energy Efficient Cooperative Routing
in Wireless Body Area Network
A thesis presented to
COMSATS Institute of Information Technology, Islamabad
In partial fulfillment
of the requirement for the degree of
MS (Electrical Engineering)
By
Ms. Sidrah Yousaf
CIIT/FA12-REE-039/ISB
Fall, 2014
iii
On Energy Efficient Cooperative Routing
in Wireless Body Area Network
A Graduate Thesis submitted to Department of Electrical Engineering as partial
fulfilment of the requirement for the award of Degree of M.S (Electrical Engineering).
Name
Registration Number
Ms. Sidrah Yousaf
CIIT/FA12-REE-039/ISB
Supervisor:
Dr. Nadeem Javaid,
Assistant Professor, Center for Advanced Studies in Telecommunications (CAST)
COMSATS Institute of Information Technology (CIIT)
Islamabad Campus.
December, 2014
iv
Final Approval
This thesis titled
On Energy Efficient Cooperative Routing
in Wireless Body Area Network
By
Ms. Sidrah Yousaf
CIIT/FA12-REE-039/ISB
Has been approved
For the COMSATS Institute of Information Technology, Islamabad
External Examiner: __________________________________
Dr. Ijaz Mansoor Qureshi
Professor, Department Of Electrical Engineering
Air University, Islamabad
Supervisor: _____________________________________
Dr. Nadeem Javaid, Assistant Professor,
Center for Advanced Studies in Telecommunications (CAST)
CIIT, Islamabad
Head of Department: _____________________________________
Dr. Shahid A. Khan, Professor,
Department of Electrical Engineering
CIIT, Islamabad
v
Declaration
I, Sidrah Yousaf, CIIT/FA12-REE-039/ISB, herebyxdeclare that I havexproduced
the workxpresented inxthis thesis, duringxthe scheduledxperiod of study. I also
declare that I havexnot taken anyxmaterial from anyxsource exceptxreferred
toxwherever due that amountxof plagiarism isxwithin acceptablexrange. If a
violationxof HEC rulesxon research hasxoccurred in thisxthesis, I shall be liablexto
punishablexaction under the plagiarismxrules of the HEC.
Date: ________________
________________
Ms. Sidrah Yousaf
CIIT/FA12-REE-039/ISB
vi
Certificate
It is certified that Ms. Sidrah Yousaf, CIIT/FA12-REE-039/ISB has carried out all
the work related to this thesis under my supervision at the Department of
Electrical Engineering, COMSATS Institute of Information Technology,
Islamabad and the work fulfills the requirements for the award of the MS degree.
Date: _________________
Supervisor:
____________________________
Dr. Nadeem Javaid
Assistant Professor
Head of Department:
____________________________
Dr. Shahid A. Khan
Professor, Department of Electrical Engineering
vii
DEDICATION
I dedicate this thesis to my parents and brothers who supported me throughout
this process and sacrificed so much for me.
viii
ACKNOWLEDGMENT
I am heartily grateful to my supervisor, Dr. Nadeem Javaid, whose encouragement, guidance and
insightful criticism from the beginning to the final level enabled me to have a deep
understanding of the thesis.
I also offer my profound regard and blessing to everyone who supported me in any respect,
during and at the completion stage of this thesis work.
Ms. Sidrah Yousaf
CIIT/FA12-REE-039/ISB
ix
ABSTRACT
On Energy Efficient Cooperative Routing
in Wireless Body Area Network
Energy efficient and reliable communication is extremely crucial in most of the applications of Wireless
Body Area Networks (WBANs). Communication between sensor nodes is the major cause of energy
consumption that limits the network lifetime, and hence, disrupts WBAN's operation. Moreover,
unreliability in wireless communication caused by the channel impairments, such as shadowing and
fading, further exacerbate the situation. In this thesis, we investigate a multi-hop and three cooperative
routing schemes to improve Energy Efficiency (EE) and reliability of WBANs. Firstly, we propose a
protocol; Critical data transmission in Emergency with Mobility support in WBANs (CEMob), which
utilizes both single-hop and multi-hop communication modes and avoids continuous data transmission to
preserve energy of sensor nodes. Performance comparison of CEMob is made with contemporary routing
protocols, Adaptive Threshold-based Thermal-aware Energy-efficient Multi-hop ProTocol (ATTEMPT)
and Reliability Enhanced-Adaptive Threshold based Thermal-unaware Energy-efficient Multi-hop
ProTocol (RE-ATTEMPT). Simulation results show that CEMob is 71% and 55% more energy efficient
than ATTEMPT and RE-ATTEMPT, respectively. Later on, to improve the achieved throughput by
CEMob, we introduce the concept of cooperative routing in Cooperative Critical data transmission in
Emergency for Static WBANs (Co-CEStat). In this protocol, network throughput is enhanced by
propagating independent signal through different paths. Simulation results reveal that Co-CEStat has 51%
and 52% more throughput than its counterpart protocols, RE-CEStat (static CEMob) and RE-ATTEMPT,
respectively. Availability of multiple links, for the propagation of same data, increases reliability of
network at the cost of extra energy consumption by cooperative nodes. To improve EE and Packet Error
Rate (PER) of Co-CEStat, we further analyze incremental cooperative communication schemes with
different number of relays. We propose a new incremental cooperative communication scheme with 3-
stage relaying and compare it with already existing incremental cooperative schemes in literature. Taking
into account the effect of PER, analytical expressions for EE of proposed 3-stage cooperative
communication scheme are also derived. Our proposed scheme proves to be more reliable with less PER
at the cost of some extra energy consumption. In the last, 3-stage incremental relaying and contemporary
2-stage incremental relaying schemes are implemented in two routing protocols; Incremental Cooperative
Critical data transmission in Emergency for Static WBANs (InCo-CEStat) and Enhanced InCo-CEStat
(EInCo-CEStat), respectively. Simulation results of incremental cooperative protocols are compared with
Co-CEStat and it is observed that incremental cooperation is more energy efficient than cooperation
approach utilized in Co-CEStat. Results also reveal that EInCo-CEStat proves to be more reliable than
InCo-CEStat with 12% more throughput and has less PER by providing three redundant links for a source
node. Whereas, InCo-CEStat proves to be more energy efficient with 24% more stability period than
EInCo-CEStat, by utilizing two cooperative links for a single source node.
x
LIST OF PUBLICATIONS
1. S. Ahmed, N. Javaid, S. Yousaf, et al., "Co-LAEEBA: Cooperative Link Aware and
Energy Efficient protocol for Wireless Body Area Networks", accepted in Computers in
Human Behavior (in press), 2014 (IF=2.2).
2. S. Yousaf, et al., "CEMob: Critical Data Transmission in Emergency with Mobility
Support in WBANs", The 28th IEEE International Conference on Advanced Information
Networking and Applications (AINA-2014), Victoria, Canada, 2014. (Chapter 3 in thesis)
3. M. Akbar, N. Javaid, S. Yousaf, et al., "TRP: Tunneling Routing Protocol for WSNs",
The 28th IEEE International Conference on Advanced Information Networking and
Applications (AINA), Victoria, Canada, 2014.
4. S. Yousaf, et al., "Co-CEStat: Cooperative Critical Data Transmission in Emergency in
Static Wireless Body Area Network", The 9th IEEE International Conference on
Broadband and Wireless Computing, Communication and Applications (BWCCA'14),
Guangzhou, China, 2014. (Chapter 4 in thesis)
5. S. Yousaf, et al., "Incremental Relay-based Co-CEStat Protocol for Wireless Body Area
Networks", The 9th IEEE International Conference on Broadband and Wireless
Computing, Communication and Applications (BWCCA'14), Guangzhou, China, 2014.
(Chapter 5 in thesis)
6. S. Yousaf, et al., "Reliable and Energy Efficient Incremental Cooperative
Communication for WBANs", submitted in IEEE ICC (International Conference on
Communcation) SAC-Communications for E-Health, 2015. (Chapter 5 in thesis)
7. S. Yousaf, N. Javaid, et al., "Incremental Cooperative Communication for Improving
Reliability in WBANs", submitted in IEEE transactions on Mobile Computing. (IF=2.9)
(Chapter 5 in thesis)
TABLE OF CONTENTS
1 Introduction 1
1.1 Wireless Body Area Networks . . . . . . . . . . . . . . . . . . . . . 2
1.1.1 Motivation............................ 2
1.1.2 Our Contribution . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Literature Review 6
2.1 RelatedWork .............................. 7
3 CEMob Protocol 12
3.1 Motivation of CEMob . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2 Basic Terminologies and Performance Parameters . . . . . . . . . . 13
3.3 CEMobProtocol ............................ 14
3.3.1 Properties of CEMob . . . . . . . . . . . . . . . . . . . . . . 14
3.3.2 Network Architecture . . . . . . . . . . . . . . . . . . . . . . 14
3.3.3 Routing and Communication Flow . . . . . . . . . . . . . . 15
3.4 EnergyModel.............................. 18
3.5 Simulation Results and Discussions . . . . . . . . . . . . . . . . . . 19
3.5.1 Stability Period and Network Lifetime . . . . . . . . . . . . 20
3.5.2 Residual Energy of WBAN . . . . . . . . . . . . . . . . . . . 20
3.5.3 Network Throughput . . . . . . . . . . . . . . . . . . . . . . 21
4 Co-CEStat Protocol 23
4.1 Motivation of Co-CEStat . . . . . . . . . . . . . . . . . . . . . . . . 24
4.2 Basic Terminologies and Performance Parameters . . . . . . . . . . 24
4.3 Co-CEStat: The Proposed Protocol . . . . . . . . . . . . . . . . . . 25
4.3.1 Properties of Co-CEStat . . . . . . . . . . . . . . . . . . . . 25
4.3.2 Network Topology . . . . . . . . . . . . . . . . . . . . . . . 25
4.3.3 Routing and Communication Flow . . . . . . . . . . . . . . 26
4.4 EnergyModel.............................. 28
4.5 Simulation Results and Discussions . . . . . . . . . . . . . . . . . . 29
4.5.1 Stability Period and Network Lifetime . . . . . . . . . . . . 30
4.5.2 Residual Energy of a Network . . . . . . . . . . . . . . . . . 30
xi
4.5.3 Network Throughput . . . . . . . . . . . . . . . . . . . . . . 30
5 Reliable and Energy Efficient Incremental Cooperative Com-
munication for WBANs 33
5.1 Motivation................................ 34
5.2 Basic Terminologies and Performance Parameters . . . . . . . . . . 34
5.3 SystemModel.............................. 35
5.4 Analysis of 3-Stage Incremental Cooperative Communication . . . . 37
5.4.1 PERanalysis .......................... 37
5.4.2 EEAnalysis........................... 38
5.5 Simulation Analysis of PER and EE for 3-Stage Incremental Coop-
erative Communication . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.5.1 PER ............................... 41
5.5.2 EE................................ 42
5.6 Incremental Cooperative Routing Protocols for WBANs . . . . . . . 44
5.7 Simulation Results and Discussions . . . . . . . . . . . . . . . . . . 45
5.7.1 Stability Period and Network Lifetime . . . . . . . . . . . . 46
5.7.2 Throughput and Packet Drop Rate . . . . . . . . . . . . . . 47
5.7.3 Residual Energy of WBAN . . . . . . . . . . . . . . . . . . . 49
6 Conclusion and Future Work 50
6.1 Conclusion................................ 51
6.2 FutureWork............................... 51
7 References 53
8 List of Publications 59
xii
LIST OF FIGURES
3.1 Connections between nodes for different body postures . . . . . . . 16
3.2 Communication flow diagram . . . . . . . . . . . . . . . . . . . . . 17
3.3 First order radio model . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.4 Stability period and network lifetime comparison . . . . . . . . . . 20
3.5 Residual energy comparison . . . . . . . . . . . . . . . . . . . . . . 21
3.6 Network throughput comparison . . . . . . . . . . . . . . . . . . . 22
4.1 Nodes’ deployment on human body . . . . . . . . . . . . . . . . . . 27
4.2 First order radio model . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.3 Stability period and network lifetime comparison . . . . . . . . . . 31
4.4 Residual energy per round comparison . . . . . . . . . . . . . . . . 32
4.5 Throughput comparison of compared protocols . . . . . . . . . . . . 32
5.1 3-stage incremental cooperative communication . . . . . . . . . . . 36
5.2 PER for on-body NLOS communication . . . . . . . . . . . . . . . 42
5.3 EE for on-body NLOS communication . . . . . . . . . . . . . . . . 42
5.4 PER for on-body LOS communication . . . . . . . . . . . . . . . . 43
5.5 EE for on-body LOS communication . . . . . . . . . . . . . . . . . 44
5.6 Network topology of InCo-CEStat and EInCo-CEStat . . . . . . . . 45
5.7 Stability period and network lifetime . . . . . . . . . . . . . . . . . 47
5.8 Number of packets received successfully at sink . . . . . . . . . . . 48
5.9 Number of packets dropped . . . . . . . . . . . . . . . . . . . . . . 48
5.10 Residual energy of network . . . . . . . . . . . . . . . . . . . . . . . 49
xiii
LIST OF TABLES
3.1 Simulation parameters . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2 Coordinates of deployed nodes on human body . . . . . . . . . . . . 19
3.3 Performance comparison . . . . . . . . . . . . . . . . . . . . . . . . 21
4.1 Coordinates of nodes deployed on human body . . . . . . . . . . . . 26
4.2 Simulation parameters . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.3 Performance comparison . . . . . . . . . . . . . . . . . . . . . . . . 31
5.1 Simulation parameters . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.2 Channel model parameters . . . . . . . . . . . . . . . . . . . . . . . 41
5.3 Coordinates of nodes deployed on human body . . . . . . . . . . . . 46
5.4 Simulation parameters for WBAN protocols . . . . . . . . . . . . . 46
xiv
Chapter 1
Introduction
1
1.1 Wireless Body Area Networks
Health monitoring systems combined with wireless communication create a class
of Wireless Sensor Networks (WSNs), known as Wireless Body Area Networks
(WBANs). Such networks consist of tiny computing devices, called sensor nodes,
along with a central unit called sink. These sensors may be placed in wearable
objects such as belts, headsets, wrist watches, etc., or may be attached to or im-
planted inside the human body to make WBAN. The IEEE 802.15 Task Group
6 has approved the standard for the physical layer and Medium Access Control
(MAC) layer for short range on-body, in-body or off-body wireless communications
[1]. Initially, the main idea behind WBANs was the provision of remote monitor-
ing of vital signs of patients suffering from chronic diseases such as asthma, heart
attack and diabetes. Nowadays, WBANs may also be utilized in sports, military
or security applications. Such networks come with great number of applications
such as, detection of human body postures and activities, monitoring of diet and
support for other health crisis.
1.1.1 Motivation
WBANs are supposed to operate properly for long duration of time without
any battery recharge or replacement, especially for in-body (implanted) sensors.
Therefore, energy management is one of the major concerns for WBAN protocols
so that recharging and replacement of batteries is as infrequent as possible and net-
work is responsive for longer period of time (Network lifetime). Continuous data
sensing and transmission, and greater distance between communicating nodes may
cause more energy consumption. Therefore, routing protocols are needed which
are capable to prolong the time interval before the death of the first node (stability
period ) and network lifetime of WBANs to increase the overall network through-
put.
There may be different modes of communication in WBANs. In case of single-
hop communication, sensors/nodes transmit their data directly to sink. As, en-
ergy consumption is directly proportional to the distance between communicating
nodes, therefore, nodes which are at a greater distance from sink die sooner be-
cause of more energy consumption. In multi-hop communication, nodes which are
at greater distance from sink, utilize intermediate nodes to forward their data to
sink. However, multi-hop communication causes increase in the energy consump-
tion of forwarding/intermediate nodes which are closer to the sink. A solution
2
is proposed in RE-ATTEMPT[2], which guarantees balanced load distribution
among nodes and extends network lifetime by utilizing multi-hop communication
for distant nodes. In the proposed routing protocol, sensor nodes in the network
are equipped with different amount of energies (heterogeneous network ) and are
placed according to their energy levels. Moreover, direct communication is used
for the delivery of emergency data, whereas, multi-hop communication is utilized
for the delivery of normal data. However, continuous data transmission causes
extra energy consumption in RE-ATTEMPT.
In case of WBANs, the sensed information is always critical, therefore, informa-
tion loss is least acceptable. There is always a chance of link failure or reception
of erroneous data due to any type of channel impairments. So, protocols assuring
reliable delivery of information, are required to be designed. Conventional coop-
erative communication is realized to be an efficient technique to achieve higher
energy savings, reliable delivery of information and to overcome the effects of
channel impairments like fading and noise in communication system. Through co-
operative communication information loss is avoided by exploiting the broadcast
nature of wireless channel. It utilizes multi-cast mode in which a single source
node transmits its data to more than one node by exploiting more than one links
at a same time. Such schemes provide spatial diversity and may improve energy
efficiency as well [3]. The main idea behind this is if a signal experiences a noise
on a certain path at particular instant, then other independent path may carry
the same signal with less noise or fading. Physical movement of body parts also
causes variable path loss due to shadowing [4, 5]. By introducing the concept
of cooperative diversity, both Signal-to-Noise Ratio (SNR) and Bit Error Rate
(BER) of signal can be improved at receiver end.
There may be single-relay based or multiple-relay based cooperative communica-
tion. For the selection of cooperative relays, both opportunistic or deterministic
approaches may be used. In opportunistic selection, node that forwards a packet
is determined on-the-fly and depends on packet receiving node. Whereas, in de-
terministic approach, the node that is supposed to forward the packet, is prede-
termined.
Although, cooperative routing significantly increases the rate of successfully re-
ceived packets, however, it is not necessary that it also enhances the overall net-
work performance in terms of Packet Error Rate (PER) and energy consumption.
Conventional cooperative networks make an inefficient use of the channel resources
because relays always forward the source signal to the destination regardless of
the channel conditions.
For a specific relay selection, the relaying strategy can be fixed, selective or in-
cremental. In fixed relaying, relays always forward the received data after certain
3
processing on it. Whereas, selective relaying makes use of instantaneous chan-
nel information to decide between relay forwarding and source re-transmission in
second phase. In incremental relaying [6,8], a short feedback, indicating success
or failure of sent data, from the destination is used. Relay(s) is (are) allowed
to forward signal only when direct transmission fails otherwise source continues
with the next data packet. This approach reduces energy consumption and total
transmission time of a network. Incremental relaying adapts to channel condi-
tions and increases spectral efficiency by saving channel resources. Incremental
relaying protocols are extensions of incremental redundancy protocols, or hybrid
Automatic-Repeat reQuest (ARQ) [6]. In conventional cooperation schemes, so-
phisticated combining techniques at destination are required for achieving spatial
diversity advantage. However, in incremental cooperation scheme, the destina-
tion has to process only one signal at a time during certain transmission phase.
Thereby, avoiding complex systems at destination side.
1.1.2 Our Contribution
In this research, our aim is to design such protocols which help to maximize life-
time, stability period and throughput of WBAN.
A network layer protocol, CEMob, is proposed to achieve higher stability period
with less energy consumption than some already designed WBAN protocols; Adap-
tive Threshold-based Thermal-aware Energy-efficient Multi-hop ProTocol (AT-
TEMPT) [7] and RE-ATTEMPT. Greater distance between nodes causes more
energy to be consumed, so less distant node is selected for data forwarding. Ef-
ficient choice of next sensor node, to which information is to be sent, is made
on the minimum hop count strategy. To preserve energy of sensor nodes, CE-
Mob replaces continuous data transmission in RE-ATTEMPT and ATTEMPT by
non-continuous threshold-based data transmission. Sensed data by sensor nodes
is transmitted only when currently sensed data is different from previously sensed
and transmitted data. Thereby, reducing the energy consumption by the whole
network. Arm’s mobility is also considered in CEMob and three different postures
are taken into consideration.
For further enhancement in stability period and network lifetime, we give the
concept of non-continuous transmission in Residual Energy based Critical data
transmission in Emergency in Static WBANs (RE-CEStat). Normal nodes select
their corresponding forwarder node with greater residual energy. Performance
upgrades and significant increase in the stability period and network lifetime is
observed due to less energy consumption of nodes.
Furthermore, we propose another protocol, Co-CEStat, in which cooperative rout-
4
ing is exploited to increase the average packet rate of our existing scheme. Protocol
is implemented by selecting a shortest path between nodes and then performance
is improved by using cooperation between nodes. Our proposed cooperative pro-
tocol gives higher throughput than our previously designed protocols.
Later on, we analyze three different communication schemes given in [8]. Compar-
ison of direct communication and incremental cooperative communication schemes
is given in this research paper. Performance evaluation shows that incremental two
relay based cooperative communication performs well in terms of PER at the cost
of Energy Efficiency (EE). Results are produced for both on-body and in-body
sensor nodes. We then propose our new incremental three relay based cooperative
communication scheme by considering on-body WBAN. Enhanced performance of
proposed scheme is shown in comparison with contemporary schemes in the lit-
erature. Later on, proposed three-stage incremental relaying scheme and existing
two-stage incremental relaying scheme are implemented in WBAN protocols i.e.,
InCo-CEStat and EInCo-CEStat, respectively. We also derive analytical expres-
sions for the PER and the EE of proposed three-stage cooperative communication
scheme. Simulation results show that the proposed scheme achieves less PER with
more diversity, high channel utilisation and less energy consumption than com-
pared conventional cooperative communication scheme.
5
Chapter 2
Literature Review
6
2.1 Related Work
To enhance the performance of WSNs and WBANs, many developments and im-
provements are made in this field. Routing protocols are designed by taking into
account some major objectives, such as, energy efficiency, quick and reliable de-
livery of data, optimal bandwidth utilization, efficient use of available recourses
etc. A large number of research is done to achieve these mentioned objectives.
In [2], authors presented a protocol in which positive features of both single-hop
and multi-hop communications are utilized. Priority based routing is done in the
protocol for normal and critical data transmission. Routes are selected on the
basis of minimum-hop count which reduces the delay in transmission.Authors in
[7], designed a routing protocol which is energy efficient and support body mo-
bility. Proposed protocol is also thermal-aware and able to change the route in
case of hot-spot detection. Direct communication is used for real-time traffic or
on-demand data while Multi-hop communication is used for normal data delivery.
One of the major challenges in WBANs is sensing of the heat produced by the
implanted sensor nodes. The proposed routing algorithm is thermal-aware which
senses the link Hot-spot and routes the data away from these links.
Analysis for PER and EE of incremental relay based cooperative communication
is made in [8]. Incremental cooperation is compared with direct communication
and is proved to be more reliable than direct communication. Simulations are
conducted to find optimal distance of relay node from source and destination.
Optimal packet size for efficient communication in WBAN is also given in this
research.
Survey is presented in [9] in which discussion about types of communication in
WBAN and their issues are provided. A detailed investigation of sensor nodes,
physical layer, data link layer, and radio technology aspects of WBAN are given
in this research.
Another energy efficient routing protocol for WBANs is proposed in [10]. Protocol
utilizes threshold approach to preserve energy of sensor nodes. Authors in [11],
proposed energy efficient routing protocol by utilizing multi-hop communication
in WBAN. A cost function is calculated to select forwarder/intermediate node
with high residual energy and minimum distance from sink.
In [12], a comprehensive survey on different design problems and techniques in
WSNs is provided. Where, energy efficient routing protocols are classified as flat,
hierarchical, query-based, coherent and non- coherent based, negotiation-based,
location-based, mobile agent-based, multipath-based and QoS-based. It is stated
that location based protocols are useful in increasing the network lifetime. Imple-
mentation of appropriate routing protocol also ensures the network connectivity
7
and reliable data delivery.
In [13], to monitor the daily activities of humans, authors use wearable sensors.
Different movements are observed during different activities. Humans perform
different movements during different activities. For this purpose, authors used a
sensing device called motion node which recognizes the activity and gives accurate
measurements.
Many other energy efficient and reliable cooperative communication schemes are
proposed to make efficient use of available resources. Authors in [14], proposed
a WSN routing protocol for wildfire monitoring. Cooperative communication is
utilized to mitigate the effects of shadowing and to improve network lifetime.
Transmission quality is enhanced by sharing the resources between nodes. A tech-
nique of reinforcement learning by opponent modeling, optimizing a cooperative
communication protocol is used which is based on Received Signal Strength Indi-
cation (RSSI) and node’s energy consumption. Their proposed protocol is energy
and quality-of-service aware cooperative routing protocol.
In [15], minimum-power routing problem is solved by proposing the Minimum
Power Cooperative Routing (MPCR) algorithm which utilize cooperative commu-
nication in wireless network. Routes with minimum transmission power are de-
fined as optimum routes, guaranteeing some certain level of throughput. Routes
are constructed as a cascade of the minimum-power single-relay building blocks
from the source to the destination.
WBAN is usually assumed to be a single-hop star network, whereas, research shows
that conventional multi-hop cooperative relaying has improved the performance
of WBANs. Authors in [16], focused on the possible advantages of cooperative
transmission for implanted sensors. Spatial diversity of multiple single-antenna
terminals is exploited to reduce total power consumed by implanted sensors. A
simple Opportunistic Large Array (OLA) technique is proposed to preserve the
energy of nodes. OLA is supposed to avoid the overhead caused by cluster and
cluster leaders. For the very first time, OLA is used for implanted sensor nodes.
Performance is improved by using cooperative relaying.
A protocol for WSN is proposed in [17], in which some nodes use extra energy
for cooperative transmission to relieve the nodes, near the sink, of their burden.
This protocol extends cooperative transmission range if residual energy of next-
hop node is low.
Authors in [18], presented a cooperative WBAN protocol that is able to support
multi-hop communication along with cooperation. This protocol extends the co-
operation at MAC layer to cross-layered gradient based routing.
In [19], energy consumption and network lifetime of a single-hop network and a
multi-hop network are compared. A propagation model is proposed for commu-
8
nication along the human body. Energy efficiency of a line and a tree topology
are studied. It is shown that single-hop communication is less efficient for distant
nodes from the sink. Author propose a scheme in which dedicated relays or coop-
erative routing approach or combination of both is utilized to increase the energy
efficiency and reliability of network.
In [20], several schemes for multi-hop cooperative relaying are proposed to increase
the lifetime of WBANs. Different models are presented for delay spread and mean
excess delay in the time-domain. Propagation measurements are made on real
human body in a multi-path environment. For analysis different body parts are
considered individually. Path loss parameters and time-domain channel charac-
teristics are obtained from the measurement and simulated data.
In [21], authors proposed cooperative WBAN and analyze channel models, sys-
tem performance and spatial diversity gain for two relays cooperation. Sitting
posture of human body is considered to study the on-body radio propagation in
time-domain UWB channel.
Authors in [22], utilized cooperative communication to reduce the BER and to
improve the network lifetime of WBAN. A mobile device aided cooperative trans-
mission scheme is proposed for BANs. Cooperative transmission is utilized to
enhance the transmission reliability and maintain a low transmission power of
sensor nodes.
In [23], authors considered the topology for WBAN as a time-varying fully con-
nected network instead of a star structure. It is observed that opportunistic co-
operative mechanism based on a decode-and-forward protocol may address the
problems in multi-hop mesh topology. This improves the packet error rate prob-
ability by using multi-hop links instead of direct link.
Authors in [24] and [25], utilized Cooperative Network Coding (CNC) to improve
reliability in WBANs. CNC combines cooperative communications and network
coding, in a feed-forward architecture. Packets are transmitted over spatially dis-
tinct paths which significantly improve the network throughput due to extra paths
for communication. These proposed schemes also provide enhanced self-healing
which is a required feature in WBAN. Moreover, these feed-forward techniques
are mostly suitable for real-time applications, where retransmissions are an inap-
propriate alternative.
In [26], authors evaluated the performance of cooperative relaying schemes for
improving the robustness of WBANs. Some sensors are selected to provide re-
dundant links for other nodes having worst channel conditions. Relay nodes are
elected from a statistical perspective. Packet error rate outage probability is taken
as performance parameter.
In [27], outage performance and energy efficiency of direct transmission, and single
9
and multi-relay cooperation schemes are analyzed in the context of WBANs. To
minimize the energy consumption, authors study the problem of optimal power
allocation with the constraint of targeted outage probability.
A protocol is presented in [28] which considers the possibility of outage between
two communicating nodes. For bandwidth efficiency, incremental relaying cooper-
ation strategy is used in this paper. Trade-off between gains in the transmit power
and the losses due to extra processing and receiving power consumption at the
relay and destination nodes required for cooperation is analyzed. Such a trade-off
is taken into consideration for the design of a network. Some other system param-
eters like the power amplifier loss, the required Quality-of-Service (QoS), the relay
location, and the optimal number of relays are also considered in this research.
Many other techniques and schemes are implemented for communication in WBAN.
A wireless accelerometer sensor module is used to determine the link performance
[29]. It records data and traffic lost on different runners and for different transmit-
ter locations around the human body (foot, leg, and arm). Approximate location
of nodes are determined for accurate and reliable reception of data. The results
also show that the sensor on the wrist gives the best outcome from the locations
tested. In [30], authors proposed a framework for the estimation of network life-
time of WBAN. A parametric model for Health Monitoring Network (HMN) is
created and probabilistic analysis is used to determine the timing and distribution
of time failure in the HMN.
Authors in [31] addressed WBAN data monitoring challenges, by allowing virtual
groups to be formed between devices of patients, nurses, and doctors to enable
remote monitoring of WBAN data. A new metric, quality of health monitoring,
is also introduced to provide feedback on the quality of data received by WBAN.
A reliable anycast routing protocol, for Zigbee-based wireless patient monitoring
is proposed in [32]. Mobile sensor nodes select the closest sink to forward their
data in a Wireless Mesh Network (WMN). This protocol reduces the number of
control messages with fast rerouting. This scheme also reduces the latency by
using intermediate routers for route recovery. A device for fall monitoring is also
implemented on the basis of proposed scheme.
In [33], data transmission scheduling problem is analyzed to make use of sleep
mode and opportunistic transmission for energy efficiency. Propagation channel
requirements and delay constrains are considered in the design of scheduling policy
to save the energy of sensor nodes. Lyapunov optimization formulation is utilized
to propose a two-step scheduling algorithm. It is proved that the algorithm can
provide worst-case delay which is guaranteed under certain conditions. In [34],
authors utilized low cost wake-up radio module to prolong the network lifetime.
This radio module is attached with the sensor node. By reducing power consump-
10
tion in idle state and increasing the sleep time of a sensor nodes, lifetime of a
network is extended. A MAC protocol is proposed for WBAN which uses on-
demand wake-up radio through a centralized wake-up mechanism. Results of this
proposed method are compared with some of the contemporary MAC protocols.
Authors in [35] presented an efficient technique to make operation of battery pow-
ered devices more reliable and efficient with minimal energy consumption. This
paper combines efficient antenna design with a cross layer energy efficient protocol
to maximize network lifetime of WBAN. Towards this goal, an efficient system is
designed through which performance of WBANs is enhanced.
11
Chapter 3
CEMob Protocol
12
3.1 Motivation of CEMob
Reliable and quick transmission of data with low energy consumption of each
sensor node is of extreme significance in WBANs. In some situations, monitored
parameters require special attention. For example, immediate response is required
whenever the sensed information belongs to the class of emergency data. There-
fore, single-hop communication is appropriate option for such situations in order
to avoid delay. One of the objectives behind this research is to wisely utilize multi-
hop and single-hop communication to enhance the overall network performance.
In ATTEMPT and RE-ATTEMPT routing protocols, continuous transmission of
data to sink occurs with no mobility support. On the other hand, transmission of
similar information increases the load on forwarder/intermediate nodes, thereby
increasing their energy consumption. These drawbacks motivate us to propose a
routing protocol; CEMob, which is capable of avoiding redundant data transmis-
sions with mobility support.
3.2 Basic Terminologies and Performance Parameters
Some basic terminologies and performance metrics used in this study are men-
tioned below:
Throughput: Total number of successfully received packets at sink is called
throughput.
Dynamic routing: Type of routing in which route selection is done on the
bases of destination and certain change in conditions.
Stability period: Stability period is defined as a time duration from the start
of a network till the death of the first node.
Residual energy: Average total remaining energy of a network after each
round is called residual energy.
Network lifetime: Total time duration of a network operation, from the start
of the network establishment till the death of the last node is called network
lifetime.
Heterogeneous network: A network, in which different initial energies are
assigned to sensor nodes, is called heterogeneous network.
Number of alive nodes: This measure gives the total number of nodes which
are not depleted and still have residual energy to communicate.
13
Advanced nodes: Sensor nodes which have more initial energy than that of
normal nodes are called advanced nodes.
3.3 CEMob Protocol
Properties, network architecture and routing flow of CEMob is discussed in the
following subsections.
3.3.1 Properties of CEMob
Following assumptions are taken for the proposed protocol:
Every node in the network is on-body and fixed.
There is only one coordinator (sink node) which is fixed at the center of the
body and responsible for gathering the data from all sensor nodes. Sink has
adequate hardware and software with constant power supply but batteries
of sensor nodes is not rechargeable.
Transmission range and transmission power of each sensor node is fixed.
Location of all nodes is initially known to each node.
The ultimate destination for each sensor node is sink node. Data transmis-
sion beyond the sink node is not allowed.
The size of generated packet by each node is always fixed and each node
transmits its generated data in its own time slot.
3.3.2 Network Architecture
Network architecture may be divided into two types: flat architecture and multi-
tier architecture. In flat architecture, sensor nodes directly send their data to
external network. In later case, data gathering is done using multiple nodes in
the base tier and the sink at the second tier is responsible to link base tier with
the external server at the third tier. Our proposed WBAN architecture is using
multi-tier architecture in which nodes are affixed on the body of patient and sink
is placed at the center of the body.
Two approaches are considered while designing a routing protocol for WBANs.
One approach is the integration of routing functions with that of MAC layer.
Whereas, the other choice is to propose a routing layer protocol such that link
qualities are measured on the bases of selected parameters. Overall performance
14
of a network and several aspects like error-rates, throughput, bandwidth usage,
transmission delay, availability, etc. We focused on the later approach to de-
velop a new energy efficient routing protocol in which dynamic routing is used for
data forwarding. In case of normal transmission, some nodes forward sensed data
through intermediate nodes. Whenever, the sensed data type is emergency or the
intermediate node is dead, node(s) establish(establishes) direct link with sink. As,
we also consider body mobility, so, it is a better strategy to choose the next hop
node by using dynamic routing.
3.3.3 Routing and Communication Flow
In order to preserve communication energy, CEMob exploits the threshold ap-
proach for data transmission. Every time node senses the information, it compares
the current information with the stored information sensed earlier. Transmission
of information occurs if variation is observed. This technique avoids transmission
of same information again and again which results in less energy consumption of
sensor nodes. As shown in the figure 3.1, eight sensor nodes are attached with the
human body. Sink, that is affixed at the center of the body, is the destination for
all nodes. However, CEMob protocol does not consider communication beyond
the sink.
Both single-hop and multi-hop approaches are used to make the network more
efficient in terms of energy consumption and quick transmission of sensed data.
We have two types of data transmission: emergency data transmission and normal
data transmission. In case of emergency data, all the nodes are supposed to estab-
lish direct link with sink. If data is normal and different from previously sensed
data, then advanced nodes are supposed to use single-hop, whereas, other nodes
use multi-hop transmission scheme. Figure 3.1 shows that, node 1, 2, 5 and 6 are
advanced nodes which collect and forward data of normal nodes to the sink after
aggregation. Node 3 and 7 forward their normal sensed data to node 6, whereas,
node 4 and 8 send their normal data to node 5. In case of arms mobility as shown
in figure 3.1, node 3 and 4 will forward their data to less distant advanced node.
Different postures and corresponding routes for nodes are shown in the figure. Ef-
ficient selection of the next hop sensor node is necessary in case of arms’ mobility.
This dynamic routing strategy reduces the energy consumption as nodes choose
less distant node for data forwarding. Communication flow diagram is shown in
figure 3.2.
15
Figure 3.1: Connections between nodes for different body postures
16
Figure 3.2: Communication flow diagram
17
Figure 3.3: First order radio model
3.4 Energy Model
The first order radio model for WBANs, used in [2], is given below:
Transmission energy of each node is calculated as,
if d >do,
Etx(L, d) = Eelec L+L(eamp(n)dn),(3.1)
or if d <do,
Etx(L, d) = Eelec L+L(ef s (n)dn).(3.2)
Whereas, transmission energy for intermediate node is,
Etx(L, d) = ((Eelec +EDA)L) + (eamp Ldn).(3.3)
Equation for reception energy is:
Erx(L) = Eelec L. (3.4)
Here, Etx and Erx are transmitting and receiving energies of each node, respec-
tively, which transmits or receive L bits at a distance d. Eelec is the energy,
which dissipates to run the circuitry of transmitter and receiver. nis the path
loss exponent and dois the reference distance. eamp and efs are characteristics of
transmitter amplifier. Whereas, EDA is the energy consumed in data aggregation.
Used values for these parameters are given in table 3.1.
18
Parameter Value
Number of nodes 8
Sink’s position At the center of the body
Initial energy Advanced node: 0.3 J
Normal node: 0.2 J
Packet size 4000 bits
Eelec 50 nJ/bit
efs 10 pJ/bit/m2
eamp 0.0013 pJ/bit/m4
EDA 5 nj/bit
Table 3.1: Simulation parameters
3.5 Simulation Results and Discussions
Simulations are conducted in MATLAB by considering parameters given in table
3.1. Eight sensors nodes are deployed at fixed positions on a human body of height
1.6 meters and width 0.8 meters. Sink node is placed at the center of the body.
Exact positions of all nodes are shown in table 3.2. We consider a heterogeneous
network such that the normal nodes are initially equipped with 0.2 J, whereas,
each advanced node is equipped with 0.3 J. For evaluation purpose, CEMob is
compared with two existing routing protocols; ATTEMPT and RE-ATTEMPT.
Results are averaged over five independent runs and each run performs 5500 rounds
of monitoring.
Node no. x-axis (m) y-axis (m)
1 0.4 1.5
2 0.2 1.3
3 0.7 0.6
4 0.2 0.6
5 0.3 0.5
6 0.6 0.5
7 0.6 0.3
8 0.3 0.3
Table 3.2: Coordinates of deployed nodes on human body
19
3.5.1 Stability Period and Network Lifetime
Figure 3.4 shows that stability period and network lifetime of CEMob is greater
than that of ATTEMPT and RE-ATTEMPT. This is due to the fact that con-
tinuous transmissions are avoided in proposed protocol which results in less en-
ergy consumption and increases stability period. Also, load distribution is well
balanced in CEMob and multi-hop transmission scheme preserve the energy of
distant nodes. This approach also helps in increasing the total network lifetime.
In ATTEMPT and RE-ATTEMPT, nodes die quickly because of single-hop and
continuous transmissions. The stability period of ATTEMPT and RE-ATTEMPT
is 478 and 569 rounds, respectively. Whereas, the first node dies at 3230th round
in the proposed protocol. So CEMob, has 81% and 84% more stability period
than RE-ATTEMPT and ATTEMPT, respectively.
0 1000 2000 3000 4000 5000
0
1
2
3
4
5
6
7
8
No. of rounds
No. of dead nodes
RE−ATTEMPT 81%
ATTEMPT 84%
CEMob
RE−ATTEMPT
ATTEMPT
Figure 3.4: Stability period and network lifetime comparison
3.5.2 Residual Energy of WBAN
As mentioned before, CEMob only transmits data when the currently sensed data
differs from previously sensed and stored data. This approach produces a slow
decrease in average residual energy of the network as the rounds proceed, thereby,
increasing the network lifetime. It is shown in figure 3.5, that CEMob has 71%
and 55% more network lifetime than that of ATTEMPT and RE-ATTEMPT,
respectively.
20
0 1000 2000 3000 4000 5000
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
RE−ATTEMPT 55%
ATTEMPT 71%
No. of rounds
Residual energy of the network (J)
CEMob
RE−ATTEMPT
ATTEMPT
Figure 3.5: Residual energy comparison
3.5.3 Network Throughput
As the network lifetime of CEMob is more than ATTEMPT and RE-ATTEMPT
routing protocol, therefore, the sink will receive data packets for longer duration in
case of CEMob. It is obvious from the figure 3.6 that the total number of packets
received at the sink for CEMob is less than that of RE-ATTEMPT because of
non-continuous transmission. However, it is still equal to that of ATTEMPT till
800th round. We utilize uniform random model for packet drop calculation, in
which probability of packet drop is set as 0.4.
Parameter CEMob ATTEMPT RE-ATTEMPT
Stability period High Low Low
Network lifetime High Low Low
Energy consumption Low High High
Throughput High Low Low
Network type Heterogeneous Heterogeneous Heterogeneous
Mobility Yes No No
Table 3.3: Performance comparison
21
0 1000 2000 3000 4000 5000
0
1000
2000
3000
4000
5000
6000
No. of rounds
Total no. of packets received at sink
RE−ATTEMPT 23%
ATTEMPT 77%
CEMob
RE−ATTEMPT
ATTEMPT
Figure 3.6: Network throughput comparison
22
Chapter 4
Co-CEStat Protocol
23
4.1 Motivation of Co-CEStat
In previously designed protocol, CEMob, we propose a solution to make a network
more energy efficient by utilizing non-continuous transmissions and multi-hop ap-
proach to preserve the energy of distant nodes. Furthermore, we introduce the
static version of CEMob, RE-CEStat, in which next-hop node is selected on the
basis of residual energy of next-hop node. RE-CEStat also avoids redundant trans-
missions to preserve energy of nodes. Reliable delivery of data is also of great
importance in WBANs. As, link between two nodes may be effected by chan-
nel impairments, therefore, a protocol is required which may ensure reliability of
the network by providing redundant links for data transmissions. Conventional
cooperation approach is one of the techniques to increase the overall network
throughput by utilizing more than one link for the same data transmission. For
this purpose, we propose a conventional cooperation protocol, Co-CEStat that
utilizes cooperation between nodes to enhance the network performance.
4.2 Basic Terminologies and Performance Parameters
Some major terminologies and performance metrics are defined below:
Throughput: Total number of packets successfully received at the sink is
called throughput.
Stability period: In applications such as body area network,stability period
is usually defined as a time interval between the start of a network and the
time at which the first node dies.
Residual energy: Average total energy of a network after each round is called
residual energy.
Network lifetime: Total time duration of a network operation, from the start
of the network establishment till the death of the last node is called network
lifetime.
Heterogeneous network: A network in which different initial energies are
assigned to sensor nodes is called heterogeneous network.
Data aggregation: Forwarding nodes process the raw data received by other
nodes and send the aggregate value to the sink.
Number of alive nodes: This measure gives the total number of nodes which
are not depleted and still have residual energy to communicate.
24
Advanced nodes: Sensor nodes which have more initial energy than that of
normal nodes are called advanced nodes.
4.3 Co-CEStat: The Proposed Protocol
Co-CEStat is using multi-tier architecture in which nodes and sink are affixed
on the human body. Co-CEStat aims to achieve energy efficiency by utilizing
cooperation between nodes for data forwarding. Co-CEStat is discussed in detail
in the following subsections.
4.3.1 Properties of Co-CEStat
Proposed protocol has following properties:
Every node in the network is fixed.
There is only one coordinator (sink node) which is fixed at the center of the
body and responsible for gathering the data from all sensor nodes. Sink has
adequate hardware and software with constant power supply but batteries
of sensor nodes is not rechargeable.
Transmission range and transmission power of each sensor node is fixed.
Location of all the nodes is initially known to each sensor node.
The main destination for each sensor node is sink node. Data transmission
beyond the sink node is not considered.
The size of generated packet by each node is always fixed and each node
transmits its generated data in its own time slot.
4.3.2 Network Topology
Figure 4.1 shows the network topology of Co-CEStat compared with NoRE-
CEStat routing protocol. Eight sensor nodes are attached with the human body.
Sink, that is affixed at the center of the body, is responsible for collecting and for-
warding data of all the sensor nodes to external server. However, communication
beyond sink is not considered for this protocol. Coordinates of sensor nodes de-
ployed on human body are shown in table 4.1. Network is heterogeneous in terms
of initial energies of nodes and there are two types of nodes: Advanced nodes
and normal nodes. Advanced nodes have more initial energy than that of normal
nodes. In figure 4.1, nodes 1, 4, 5 and 8 are normal nodes, whereas, nodes 2, 3,
25
6 and 7 are advanced nodes. In NoRE-CEStat, forwarder node is selected on the
basis of residual energy. Whereas, in Co-CEStat , cooperative nodes are fixed and
allow source nodes to utilize more than one link at a time for data transmission.
To differentiate cooperative routing protocol with non-cooperative protocols, we
use No with each protocol’s name throughout the discussion.
Node no. x-axis (m) y-axis (m)
1 0.4 1.5
2 0.6 1.2
3 0.2 1.2
4 0.7 0.8
5 0.1 0.8
6 0.5 0.5
7 0.2 0.5
8 0.2 0.2
Table 4.1: Coordinates of nodes deployed on human body
4.3.3 Routing and Communication Flow
Co-CEStat is cooperation based protocol in which there are four advanced nodes
which are serving as cooperative nodes. By using cooperation, normal nodes are
allowed to forward more packets through cooperating nodes in each round. Each
link has its own capacity and every node receives a flow which cannot exceed the
total capacity of the link. Outgoing and incoming flow for each node must be equal
to satisfy the flow network restriction, except when it is a normal source node,
which has more outgoing flow, or sink, which has just incoming flow. Link between
cooperative node and sink is high capacity link as it carries regular packets along
with forwarded packets. Normal source nodes multi-cast data simultaneously on
two links to avoid information loss.
To minimize energy consumption, Co-CEStat makes use of threshold approach for
data transmission. Every time the information is sensed, threshold is compared.
If threshold value is crossed, sensed data is considered to be emergency data and
is directly sent to sink. Otherwise, the current information is matched with stored
information which is sensed earlier. Transmission of information occurs if variation
is observed. This technique avoids transmissions of the same information which
26
Figure 4.1: Nodes’ deployment on human body
27
results in less energy consumption of sensor nodes. Whenever,the sensed data is
emergency or the cooperative nodes are dead, node(s) establish(establishes) direct
link with sink. If the data is normal and it is different from previously sensed value,
than cooperative nodes are supposed to use single-hop communication, whereas,
normal nodes utilize cooperative routing. Node 1, 4, 5, and 8 forward their normal
sensed data to sink through their corresponding cooperative nodes. Node 2, 3,
6 and 7 are cooperative nodes which collect and forward data of normal nodes
with their own sensed data to the sink after aggregation. This dynamic routing
strategy reduces the energy consumption as nodes choose less distant node for
data forwarding. Energy consumption for transmission of data from a node ito
another node jis proportional to distance dn
ij between two nodes. nis the path
loss exponent and depends on the transmission environment.
Transmission energy depends on whether the node directly transmits data to sink
or transmits cooperatively using neighbouring nodes as relays. Transmission and
reception energy of each node is calculated with the help of energy model discussed
in the following section.
4.4 Energy Model
According to first order radio energy model [2], transmission energy of sensor node
at distance, d >dois ,
Etx(L, d) = Eelec L+L(eamp dn),(4.1)
and for d <dois,
Etx(L, d) = Eelec L+L(efs dn).(4.2)
Whereas, transmission energy for intermediate node is,
Etx(L, d) = ((Eelec +EDA)L) + (eamp Ldn).(4.3)
Equation for reception energy of all sensor nodes is:
Erx(L) = Eelec L. (4.4)
Here, Etx and Erx are transmitting and receiving energies of each node, respec-
tively, which transmits or receive L bits at a distance d. Eelec is the energy,
which dissipates to run the circuitry of transmitter and receiver. nis the path
loss exponent and dois the reference distance. eamp and efs are characteristics of
transmitter amplifier. Whereas, EDA is the energy consumed in data aggregation
28
Figure 4.2: First order radio model
by intermediate or forwarder nodes. Used values for these parameters are given
in table 4.2. Figure 4.2 explains the radio energy model.
4.5 Simulation Results and Discussions
In order to validate the proposed idea, simulations are conducted in MATLAB.
Performance of the proposed Co-CEStat is compared with non-cooperative NoRE-
CEStat and NoRE-ATTEMPT routing protocols. The aim of this evaluation is
to observe the effects of cooperative routing in Co-CEStat. Different performance
parameters are compared and discussed in the following subsections. Simulation
parameters are presented in table 4.2. Results are averaged over five indepen-
dent runs and each run performs 5500 rounds of monitoring. To differentiate
cooperative routing protocol with non-cooperative protocols, we use No with each
protocol’s name in simulated plots and discussions.
Parameter Value
Number of nodes 8
Initial energy Advanced node: 0.3 J
Normal node: 0.1 J
Packet size 1000 bits
Data generation rate 4000 bits
Eelec 50 nJ/bit
efs 10 pJ/bit/m2
eamp 0.0013 pJ/bit/m4
Table 4.2: Simulation parameters
29
4.5.1 Stability Period and Network Lifetime
Figure 4.3 shows the stability period and network lifetime of all the compared
protocols. It is clear from the results that stability periods for Co-CEStat and
NoRE-CEStat are almost same and greater than NoRe-ATTEMPT. As NoRE-
ATTEMPT transmits information continuously, more energy is consumed by each
node in each round. Increased Stability period of Co-CEStat and NoRE-CEStat
is because of non-continuous data transmission. Data is transmitted only if some
difference is found between current and previously transmitted data.
4.5.2 Residual Energy of a Network
Figure 4.4 shows the residual energy per round of all the analyzed protocols.
Networks are equipped with two types of sensor nodes in terms of initial energy.
There are normal nodes with initial energy equal to 0.1 joules, whereas, advanced
nodes have 0.3 joules as initial energy. Initial total energy of all protocols is
kept same i.e. 1.6 Joules. It is observed from compared results of four protocols
that non-continuous transmission in Co-CEStat and NoRe-CEStat causes greater
residual energy per round. Another reason for more residual energy is that multi-
hop transmission is utilized for each distant node in Co-CEStat and NoRe-CEStat.
4.5.3 Network Throughput
Communication is mediated by two different links in terms of bit rates. In
Co-CEStat, links between cooperative nodes and sink are high data rate links,
whereas, links between source nodes and cooperative nodes have low data rates.
Nodes which transmit data through cooperative nodes are allowed to transmit
more packets per round than nodes using non-cooperative or direct communi-
cation. It is clear from figure 4.5 that Co-CEStat achieves 51% and 52% more
throughput due to cooperative routing than that of NoRe-CEStat and NoRe-
ATTEMPT, respectively. We also assume that the link failure may occur and
there is a chance of packet loss due to bad link condition. For simulations, we as-
sume the probability of link failure equal to 0.3. Overall performance comparison
of the compared protocols is given in table 4.3.
30
0 1000 2000 3000 4000 5000
0
1
2
3
4
5
6
7
8
No. of rounds
No. of dead nodes
NoRE−CEStat
NoRE−ATTEMPT
Co−CEStat
Figure 4.3: Stability period and network lifetime comparison
Parameters Co-CEStat RE-CEStat RE-ATTEMPT
Stability period High High Low
Network lifetime High High Low
Throughput Higher High Low
Cooperation Yes No No
Network type Heterogeneous Heterogeneous Heterogenous
Table 4.3: Performance comparison
31
0 1000 2000 3000 4000 5000
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
No. of rounds
Residual energy of the network (J)
NoRE−CEStat
NoRE−ATTEMPT
Co−CEStat
Figure 4.4: Residual energy per round comparison
NoRE−CEStat NoRE−ATTEMPT Co−CEStat
0
0.5
1
1.5
2
2.5
3
3.5
4x 104
51%
52%
No.of Packets
Figure 4.5: Throughput comparison of compared protocols
32
Chapter 5
Reliable and Energy Efficient Incremental Cooperative
Communication for WBANs
33
5.1 Motivation
In WBANs, low energy consumption of sensor nodes with reliable and quick de-
livery of data is of special concern. Direct link between transmitter and receiver is
appropriate to deliver data from source to destination in WBANs. However, links
between nodes may experience path-loss due to fading or noise in both Line-of-
Sight (LOS) and Non-LOS (NLOS) scenarios. Less SNR at any particular time,
causes packet drop at sink due to more BER than certain threshold. Therefore,
an efficient and reliable topology for WBAN is required which may ensure greater
throughput with less energy consumption of sensor nodes. Conventional coop-
erative communication proves to be more reliable by providing cooperative links
along with direct link for the transmission of same information. To reduce the
energy consumed by cooperative nodes in conventional cooperation, incremental
cooperation approach is used in the literature to wisely utilize the merits of both
direct and cooperative links. This type of cooperative communication increases
the EE of WBAN. Major objectives behind this research are: (i) to study the ef-
fects of incremental relay-based cooperation with different number of cooperative
relays/nodes, (ii) to improve the EE of conventional cooperative scheme by using
incremental cooperative scheme and (iii) to implement incremental cooperation
schemes in WBAN’s protocols to improve the overall network PER and EE.
5.2 Basic Terminologies and Performance Parameters
Some basic terminologies and performance metrics that are used in this research
are mentioned below:
Path loss: Reduction in the power of signal as it propagates through the
channel is called path loss.
Fading: Degradation of a signal on propagation paths is called fading. En-
ergy absorption, reflection, diffraction, shadowing by body, and body posture
may cause fading.
Shadowing: Variation in path loss, due to movement of body parts or envi-
ronment, around the mean is called shadowing.
PER: Number of successfully received packets divided by the total number
of packets transmitted is called PER.
EE: The way of managing and restraining the growth of energy consumption
is called energy efficiency.
34
BER: Number of erroneous bits divided by the total number of received bits
is called BER.
Diversity: Antenna diversity or space diversity, is a wireless diversity schemes
that uses two or more antennas to improve the quality and reliability of a
wireless link.
SNR: It is defined as the ratio of signal power to the noise power, often
expressed in decibels.
Stability period: In WBAN, stability period is usually defined as a time
interval between the start of a network and the time at which the first node
dies.
Residual energy: Average total remaining energy per second of a network is
called residual energy of a network.
Network lifetime: Total time duration of a network operation, from the start
of the network establishment till the death of the last node is called network
lifetime.
Throughput: Total number of successfully received packets per unit time at
the sink is called throughput.
Heterogeneous network: A network in which different initial energies are
assigned to sensor nodes is called heterogeneous network.
Advanced nodes: Sensor nodes which have more initial energy than that of
normal nodes are called advanced nodes.
5.3 System Model
We consider a WBAN which consists of on-body sensor nodes which are supposed
to transmit their sensed data to coordinator/sink attached with the body. Ulti-
mate destination for each node is sink and it is assumed that sink has a constant
power supply with no energy constraint. We propose a three-stage cooperation
protocol for WBAN and compare its analytical and simulation results with the
contemporary schemes. As the distances between sensor nodes in WBAN is small,
so it is assumed that all the nodes are within the transmission range of each other.
Communication is considered to be half-duplex. Fig. 5.1 explains the system
model of proposed scheme.
Our proposed WBAN scheme consists of four communication phases. There are
three potential relays R1,R2and R3available for a source node. Proposed scheme
35
has a three stage ARQ mechanism as shown in figure 5.1. In the first phase of
cooperation, the source transmits the data packet to the destination, and all three
relays overhear this packet. If the destination node decodes the packet successfully
in the first phase, it sends a short feedback in the form of positive ACKnowledge-
ment (ACK 1) which indicates that there is no need of relaying. However, if the
destination node fails to decode the data packet correctly, a Negative ACKnowl-
edgement (NACK 1) is sent which is also heard by all relays. After this, three
stage relaying process is invoked. If relay R1has received and decoded the data
packet correctly in the first phase, it forwards that packet to the destination dur-
ing the second phase. If packet is decoded successfully at destination, it transmits
back ACK (ACK 2), and hence, the first stage of cooperative relaying becomes
successful. Otherwise, destination node sends NACK (NACK 2), implying the
need for second stage of cooperative relaying. Upon overhearing NACK 2, relay
R2forwards the data packet, which is received correctly in the first phase, to the
destination in the third phase. If the destination node is able to decode the packet
successfully, it sends back ACK 3, otherwise it sends NACK 3, which indicates the
failure of second stage of cooperation as well. It may be noted that, even if R1
does not transmit in the second phase (due to decoding failure at R1), R2can for-
ward the packet to the destination in the third phase, if it had received the packet
correctly in the first phase. Same is the case with third relay R3, if R2is unable
to decode the packet in the first phase or destination fails to decode and receive
the packet correctly from R2,R3is responsible to transmit that data packet to
the destination. If the destination node is able to decode the packet successfully,
the success of third stage of relaying is occurred otherwise the packet is considered
dropped. Figure 5.1 shows the incremental cooperative communication model for
three stage relaying. In the next section, we present expressions for the PER and
Figure 5.1: 3-stage incremental cooperative communication
36
EE for the three stage relaying scheme and to explain signal propagation. Expres-
sions for single and two stage relaying communication schemes may be seen in [8].
Our derived expressions are mostly dependent on distance between sensor nodes.
5.4 Analysis of 3-Stage Incremental Cooperative Communication
In this section, we derive expressions for calculating PER for three-stage incre-
mental relaying. We also analyze the overall energy consumption for our proposed
cooperative scheme. It is assumed that link between two nodes in WBAN is
affected by path loss, shadowing and Additive White Gaussian Noise (AWGN).
According to [3], the path loss model for WBAN, which is dependant on distance
dbetween communicating nodes, is based on the Friis formula in free space and
is described as:
P L(d) = P L(do) + 10nlog d
do
,(5.1)
where P L(do) is the path loss in dB at a reference distance doand nis the path
loss exponent. Path loss due to distance may vary with the body movement and
certain changes in surrounding environment. It may differ from its mean value and
this phenomena is called shadowing. Shadowing may also occur in static body.
By considering the factor of shadowing, the total path loss may be given as:
P L =P L(d) + Xσ.(5.2)
Here Xσis a shadowing factor in dB which is a Gaussian-distributed random
variable with zero mean and a standard deviation, σ. According to channel model
for WBAN given in [3], SNR at the receiver end is computed as:
γ(dB) = PTP L PN(5.3)
where PTis the transmit power and PNis the noise power for all nodes.
5.4.1 PER analysis
For three-stage incremental relaying, it is assumed that there are three poten-
tial relays, R1,R2and R3available to cooperate with the source. Let P E RSR1,
P ERS R2,P ERSR3,P E RR1D,P ERR2Dand P ERR3Drepresent the probability of
error of source-to-relay (R1) (SR1), source-to-relay (R2) (SR2), source-to-
relay (R3), (SR3), R1-to-destination (R1D), R2-to-destination (R2D) and
R3-to-destination (R3D) links, respectively.
37
The three-stage relaying process fails if one of the following events occur:
(i) the four links, SD,SR1,SR2and SR3fail,
(ii) SD,SR2and SR3links fail, SR1link is error free, R1decodes and
forwards but R1Dlink fails;
(iii) direct communication, SR1and SR3links fail, R3decodes and forwards
the data packet, but R3Dlink fails,
(iv) SD,SR1and SR3links fail while SR2link is error free, R2decodes
and forwards but fails due to error in R2Dlink,
(v) SD,SR1,SR2and SR3links fail, whereas, R1D,R2Dand
R3Dlinks are in error,
(vi) SDand SR3link fail, SR1and SR2links are in error free, but
R1Dand SR2links fail,
(vii) SDand SR1links fail, SR2and SR3links are error free, R2and
R3decode and forward the packet but R2Dand R3Dlink fail,
(viii) SDand SR2links fail, SR1andSR3links are error free, R1and
R3decode and forward the packet but R1Dand R3Dlinks fail.
Hence, the PER for the three-stage relaying scheme is given as:
P ER(3)
CC =
P ERSD P ERS R1P ERSR2P E RSR3
+P ERSD (1 P ERS R1)P ERSR2P E RSR3P ERR1D
+P ERSD P ERS R1(1 P ERSR2)P E RSR3P ERR2D
+P ERSD P ERS R1P ERSR2(1 P E RSR3)P ERR3D
+P ERSD (1 P ERS R1)(1 P ERSR2)(1 P E RSR3)P ERR1DP E RR2DP ERR3D
+P ERSD (1 P ERS R1)(1 P ERSR2)P E RSR3P ERR1DP E RR2DP ERR3D
+P ERSD P ERS R1(1 P ERSR2)(1 P E RSR3)P ERR1DP E RR3D
+P ERSD (1 P ERS R1)P ERSR2(1 P E RSR3)P ERR1DP E RR3D
(5.4)
5.4.2 EE Analysis
we analyze EE for three-stage incremental cooperation according to energy model
given in [20]. This model considers the energy required to run the circuitry of
transmitter and receiver for both data and ACK/NACK packets. The total energy
consumed in the transmission of a data packet is computed below for three stage
38
relaying process.
EE (3)
CC,DAT A =
[(ET Xelec + 4ERXelec +PT
R)(1 P ERSD )
+ (2ET Xelec + 5ERXelec + 2 PT
R)P ERSD (1 P ERS R1)
+ (2ET Xelec + 5ERXelec + 2 PT
R)P ERSD P ERS R1(1 P ERSR2)
+ (2ET Xelec + 5ERXelec + 2 PT
R)P ERSD P ERS R1P ERSR2(1 P E RSR3)
+ (2ET Xelec + 5ERXelec + 2 PT
R)P ERSD (1 P ERS R1)P ERR1DP E RSR2(1 P ERS R3)
+ (3ET Xelec + 6ERXelec + 3 PT
R)P ERSD (1 P ERS R1)P ERR1D(1 P E RSR2)P ERR2DP E RSR3
+ (4ET Xelec + 7ERXelec + 4 PT
R)P ERSD (1 P ERS R1)P ERR1D(1 P E RSR2)P ERR2D(1 P E RSR3)
+ (ET Xelec + 4ERXelec +PT
R)P ERSD P ERS R1P ERSR2P E RSR3](L+H).
(5.5)
Where, L is the packet size and H is overhead size in bits. ET Xelec and ERXelec are
the energies required for transmitter and receiver electronics in transmitting and
receiving one bit, respectively. Ris the data rate.
We find the total energy consumption of all the events in which packet transmis-
sion is successful:
(i) The probability of successful direct transmission is (1 P E RSD ). Three relays
overhear the packet which consumes receiving energy, (ET Xelec + 4ERXelec +PT
R) .
(ii) The direct link (S-D) fails and R1correctly receives and decodes the mes-
sage from source. R1forwards the packet to the destination with probabil-
ity P ERSD(1 P E RSR1) which results in total energy consumption per bit of
(2ET Xelec + 5ERXelec + 2PT
R).
(iii) In case SDand SR1links fail and SR2link is error free. The energy
consumption is same as in (ii).
(iv) In case SD,SR1and SR2links fail and SR3link is error free. The
energy consumption is same as in (ii).
(v) SDlink fails, SR1link error free, and R1decodes and forwards the message
to the destination. SR2and R1Dlinks fail and SR3link is error free. The
probability of this event is P E RSD(1 P E RSR1)P ERR1DP E RSR2(1 P ERSR3)
and energy consumption per bit is same as in (ii).
(vi) The SDlink fails, SR1and SR2links are error free, and R1D,
R2Dand SR3links are in error with total probability of P ERSD(1
P ERS R1)P ERR1D(1 P ERS R2)P ERR2DP E RSR3. The energy consumption per
bit is (3ET Xelec + 6ERXelec + 3PT
R).
(vii) Direct link fails, SR1,SR2and SR3are error free links, whereas,
R1Dand R2Dlinks are in error with the total probability of P ERSD(1
P ERS R1)P ERR1D(1P E RSR2)P ERR2D(1 P ERS R3). Energy consumption per
bit is (4ET Xelec + 7ERXelec + 4PT
R).
(viii) All four links from source to destination and relays fail with probability
P ERS DP ERS R1P ERS R2P ERSR3. The energy consumption per bit for this event
39
is (ET Xelec + 4ERXelec +PT
R). Total energy consumption also includes the energy
involved in the transmission of ACK/NACK packets and is computed as follows:
EE (3)
CC,ACK/N ACK = [(ET Xelec + 4ERXelec +PT
R)
+ (ET Xelec + 4ERXelec +PT
R)P ERSD (1 P ERS R1)
+ (ET Xelec + 3ERXelec +PT
R)P ERSD (1 P ERS R1)(1 P ERSR2)P E RR1D
+ (ET Xelec + 3ERXelec +PT
R)P ERSD P ERS R1(1 P ERSR2)
+ (ET Xelec + 3ERXelec +PT
R)P ERSD P ERS R1(P ERSR2)(1 P E RSR3)
+ (ET Xelec + 3ERXelec +PT
R)P ERSD (1 P ERS R2)P ERSR1P E RR2D(1 P ERS R3)](A+H)
(5.6)
Where A is the size of ACK/NACK in bits. Energy consumption is same for the
transmission and reception of both ACK and NACK. The first term in (6) shows
the energy consumption involved in the transmission of ACK/NACK by the des-
tination in the first phase. (1-P E RSD) is the probability of ACK and NACK is
transmitted with probability P ERS D. In second phase, either ACK or NACK is
transmitted for the the packet decoded and forwarded by R1to destination, this
happens with probability P ERS D (1-P E RSR1). The second term in eq. 5.6 rep-
resents the energy consumption associated with second phase. In the third phase,
R2forwards the packet, which is followed by another sequence of ACK/NACK
transmissions. ACK/NACK is transmitted if R2decodes and forwards the packet
to the destination. This may happen because of the following reasons: (i) failure
of direct communication, one-stage relaying, SR2link becoming error free and
(ii) failure of SDand SR1links, SR2link becoming error free. In the
fourth and last phase, ACK/NACK is transmitted if R3decodes and forwards the
packet to the destination. This may happen because of the following mentioned
reasons: (i) failure of SD,SR1and SR2,SR3link is error free and
(ii) failure of SDand SR1, success of SR2, failure of R2Dlink and
SR3link is error free. Therefore, the EE of three-stage incremental cooperative
communication is computed as follows:
η(3)
CC =(1 P ER3
CC )xL
E3
CC +EE (3)
CC,ACK/N ACK
.(5.7)
Where x=(ET Xelec +4ERXelec +PT
R).
5.5 Simulation Analysis of PER and EE for 3-Stage Incremental Co-
operative Communication
In this section, we present performance evaluation of our proposed WBAN, which
is compared with existing schemes, in terms of PER and EE . All results are
obtained from the expressions presented in section 5.4. Simulation parameters are
40
Table 5.1: Simulation parameters
Parameter Value
Packet size 500 bits
Overhead 80 bits
ACK/NACK 64 bits
Transmission power -12 dBm
Data rate 2 Mbps
ET Xelec 50 nJ/bit
ERXelec 50 nJ/bit
Table 5.2: Channel model parameters
Parameters NLOS LOS
do(cm) 10 10
PL(do)(dB) 48.4 35.2
n 5.9 3.11
Xσ5 6.1
given in tables 5.1 and 5.2. We only consider the case of on-body sensor nodes as
we further implement these models in on-body WBAN protocols.
5.5.1 PER
PER is plotted against distance to see the effect of various distances between
source and destination, rsd. For cooperative communication, distance between
source and relay, rsr , and relay and destination, rr d, are kept half of the distance
between source and destination. Figure 5.2 and 5.4 show PER for on-body LOS
and NLOS, direct and cooperative communication schemes. It is observed from the
figure 5.2 and 5.4 that PER for direct communication is higher than the PER for
cooperative communication. When direct link is not reliable enough for efficient
transmission, cooperative communication proves to be better solution by providing
redundant links for packet transmission. It is seen from the figures that path
loss increases with the increase in distance. Therefore for larger distance, direct
communication has more PER. Thus, for increased hop length between source and
destination, cooperative communication is useful. It is obvious from the plots that
two relay communication is better than single relay communication, same is the
41
case for three relay communication which is better than single and double relay
communication. When the first and second stage of relaying fails, relay R3provides
an extra redundant link to the destination and enhances network reliability. It is
also shown that PER of LOS communication is less than NLOS communication
due to more path loss in NLOS communication. Therefore, LOS communication
offers less PER for longer hop lengths between source and destination.
10 20 30 40 50 60
10−15
10−10
10−5
100
Source destination hop length (cm)
PER
Direct
Single relay
Two relay
Three relay
Figure 5.2: PER for on-body NLOS communication
10 20 30 40 50 60
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Source destination hop length(cm)
EE
Direct
Single relay
Two relay
Three relay
Figure 5.3: EE for on-body NLOS communication
5.5.2 EE
EE of direct and incremental cooperative communication schemes are observed
in figure 5.3 and 5.5. Series of experiments are performed in [6] to find the best
distance between source and relay and between relay and destination. The hop
42
lengths of SRand RDlinks are selected to be 0.5 times the distance between
the source and the destination. Figure 5.3 and 5.5 show the results for the EE of
on-body NLOS and LOS scenarios, respectively. EE is plotted against SDhop
length, rsd, for direct and cooperative communication schemes. It is concluded
from the results that increased distance between source and destination, rsd, de-
creases EE considerably. For lower distances, direct transmission proves to be
more energy efficient than cooperative transmissions. When the hop length, rsd ,
exceeds certain threshold, cooperative communication turns out to be more en-
ergy efficient than direct communication. Although, cooperative communication
improves reliability as it has lower PER, its EE is significantly affected because
of increased energy consumption due to additional transmissions and decoding by
the relays. When rsd is above the threshold, the PER of direct communication is
so high that its EE is significantly affected. As the PER of three relay communi-
cation is lowest than the other two relaying schemes, so it has lowest EE due to
more energy consumption by relays.
0 50 100 150 200 250 300 350
10−15
10−10
10−5
100
Source destination hop length (cm)
PER
Direct
Single relay
Two relay
Three relay
Figure 5.4: PER for on-body LOS communication
43
0 50 100 150 200 250 300 350
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Source destination hop length (cm)
EE
Direct
Single relay
Two relay
Three relay
Figure 5.5: EE for on-body LOS communication
5.6 Incremental Cooperative Routing Protocols for WBANs
We consider two incremental cooperative communication schemes, discussed in
the previous sections. We design two network layer protocols for WBANs and
implement two and three-relay incremental cooperation in them to analyze and
compare their performance. Firstly, we study the effect of two-stage incremental
cooperation in InCo-CEStat protocol. To study the effects of three-stage incre-
mental cooperation, we design EInCo-CEStat protocol and compare its results
with the InCo-CEStat. EE, PER, throughput and stability period for all three
protocols are observed. We also compare EInCo-CEStat with a conventional co-
operation protocol; Co-CEStat.
We consider four phase incremental relay-based cooperation in EInCo-CEStat by
using three potential relays for each source node. In the first phase, the source
transmits data to sink, which is overheard by its three potential relays, R1,R2
and R3. If the destination/sink is able to detect the packet correctly in this phase,
it sends back an ACK, and relays just remain idle. If NACK is received from sink
at source node, it indicates that data packet is dropped due to high BER and
data forwarding from R1is needed. If R1successfully detects the data packet in
the first phase, it forwards the data packet to the destination (sink) in the second
phase. If data packet is received with acceptable BER at the sink, the second
phase of cooperation is successfully completed. However, if sink fails to detect
the packet sent by R1,R2is supposed to forward the packet to sink which was
correctly received in the first phase. If the sink again fails to receive the packet
from R2due to high BER, failure of the third phase occurs. Finally, the last phase
of communication occurs between R3and sink. System model for InCo-CEStat is
also the same with two relay cooperative communication. Therefore, InCo-CEStat
44
consists of three communication phases accordingly.
Figure 5.6 shows the topology of InCo-CEStat and EInCo-CEStat protocols for
comparison. Two heterogeneous networks consisting of eight sensor nodes are
shown in figure 5.6. There are four normal source nodes (S), four cooperative
nodes (R), and a sink node (D). Cooperative nodes also have their own sensed
data to be transmitted along with data to be forwarded. In the proposed proto-
cols, it is assumed that sink limits all nodes to transmit only in their own reserved
time slots. Collision avoidance and network coordination is essential to maintain
QoS in WBANs. Further, half-duplex communication is assumed, and all the
nodes are within the transmission range of each other.
All nodes transmit on different links and are independent of each other. Time
Division Multiple Access (TDMA) scheme is utilized and channel is accessed by
nodes in different time slots.
Figure 5.6: Network topology of InCo-CEStat and EInCo-CEStat
5.7 Simulation Results and Discussions
We compare the performance of incremental relay-based cooperation implemented
in InCo-CEStat and EInCo-CEStat; with conventional cooperative protocol, Co-
CEStat. We assume network area of 0.9m×1.7m, where on body nodes are
45
Table 5.3: Coordinates of nodes deployed on human body
Node no. x-axis y-axis
1 0.45 1.6
2 0.2 1.5
3 0.7 1.5
4 0.1 0.85
5 0.8 0.85
6 0.2 0.5
7 0.7 0.5
8 0.7 0.3
deployed at fixed positions as shown in table 5.3 and sink is placed at the center
of the body i.e., 0.4m×0.8m. Co-CEStat and InCo-CEStat use two relays for
each normal source node, whereas, EInCo-CEStat uses three relays. Topology of
InCo-CEStat and EInCo-CEStat is shown in figure 5.6 and topology of Co-CEStat
is already shown in previous chapter. Table 5.4 shows the simulation parameters
considered for all three schemes. Rest of the simulation parameters are same as
Table 5.4: Simulation parameters for WBAN protocols
Parameter Value
Number of nodes 8
Number of sink 1
Initial energy Cooperative node: 0.3 J
Normal node: 0.15 J
Offered load 10,000 bits/node
Average wait time [38] 4 seconds/packet
BER threshold 0.5
given in table 5.1 and 5.2.
5.7.1 Stability Period and Network Lifetime
Stability period and network lifetime of compared protocols is shown in Figure
5.7. It is observed from the figure that Co-CEStat has less stability period than
46
InCo-CEStat and EInCo-CEStat because in Co-CEStat, cooperative nodes always
forward data irrespective of channel conditions. Each cooperative node forwards
data of two other nodes along with its own sensed data which causes extra en-
ergy consumption. InCo-CEStat and EInCo-CEStat prove to be more stable with
greater network lifetime because incremental relaying adapts to channel condi-
tions and cooperative nodes forward the data only when it is needed. However,
EInCo-CEStat has less stability period than InCoCEStat. This is due to extra
energy consumption by third node which acts as a relay when two-stage cooper-
ative relaying is unsuccessful. Third relay node, which is invoked for forwarding
data in fourth phase, is always a normal source node having less residual energy
than cooperative nodes. As this node forwards the data along with its own sensed
data and has less initial energy, therefore, it dies earlier than other nodes. EInCo-
CESTat has 24% less stability period than that of InCo-CEStat and 17% more
stable than Co-CEStat.
0 0.5 1 1.5 2 2.5 3 3.5x 104
0
1
2
3
4
5
6
7
8
Time (s)
No. of dead nodes
In−CoCEStat −24%
Co−CEStat 17%
InCo−CEStat
EInCo−CEStat
Co−CEStat
Figure 5.7: Stability period and network lifetime
5.7.2 Throughput and Packet Drop Rate
Figure 5.8 and 5.9 show results for total number of packets received at sink suc-
cessfully and the number of packets dropped due to higher BER than certain
pre-defined threshold, respectively. It is observed from the figure 5.9 that EInCo-
CEStat has highest overall throughput. This is due to availability of more links
for packet transmission, in case of failure of direct link. InCo-CEStat has two co-
operative nodes, whereas, EInCo-CEStat has three cooperative nodes to forward
data of normal nodes. Higher throughput is achieved by increasing diversity or-
der in EInCo-CEStat at the cost of EE. During network lifetime, Co-CEStat has
highest throughput due to reception of three copies of transmitted data at sink,
47
whereas, incremental relaying allows the reception of single copy of data at a time.
Availability of three redundant links and longer network lifetime in EInCoCEStat,
causes highest overall network throughput. EInCo-CEStat has 5% and 12% more
throughput than Co-CEStat and InCo-CEStat, respectively.
Packet drop rate of EInCo-CEStat is also less than that of InCo-CEStat, as shown
in figure 5.9. In case, the direct communication between source and sink fails,
there are three more communication links available to forward the data to the
sink. Whereas, InCo-CEStat completes its relaying in three phases and has two
more redundant links after the failure of direct link. This behaviour supports the
simulation results shown in figure 5.2 and 5.4. Packet drop rate of Co-CEStat is
also greater than incremental cooperative communication protocols. More number
of transmissions leads to more number of link failures and more packet drops.
0 0.5 1 1.5 2 2.5 3 3.5x 104
0
5000
10000
15000
Time (s)
Packet received at sink
Co−CEStat 5%
InCo−CEStat 12%
InCo−CEStat
EInCo−CEStat
Co−CEStat
Figure 5.8: Number of packets received successfully at sink
0 0.5 1 1.5 2 2.5 3 3.5x 104
0
2000
4000
6000
8000
10000
12000
Time(s)
Packets dropped
Co−CEStat 71%
InCo−CEStat 22%
InCo−CEStat
EInCo−CEStat
Co−CEStat
Figure 5.9: Number of packets dropped
48
5.7.3 Residual Energy of WBAN
Residual energy of all three compared WBANs is evaluated in figure 5.10. EE
of Co-CEStat is improved by using incremental cooperation in InCo-CEStat and
EInCo-CEStat. It is shown previously in figure 5.3 and 5.5 that 2-relay incre-
mental cooperation is more energy efficient than 3-relay incremental cooperation.
Figure 5.10 supports the results in figure 5.3 and 5.5. In order to reduce PER and
to achieve higher diversity order, three cooperative links are used in EInCo-CEStat
which consumes more transmission and reception energy than InCo-CEStat with
two cooperative links. However, EInCo-CEStat is still more energy efficient than
Co-CEStat. Therefore, EInCo-CEStat and Co-CEStat have increased throughput
at the cost of increased energy consumption. In Co-CEStat, cooperative nodes
always forward the data and consume energy even when it is not needed. So, it is
seen from the figure 5.9 that at any instant of time, InCo-CEStat has highest resid-
ual energy which leads to highest network lifetime. Incremental relaying saves the
channel resources, however, extra energy is consumed in redundant transmissions.
0 0.5 1 1.5 2 2.5 3 3.5x 104
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Time (s)
Residual energy (J)
InCo−CEStat
EInCo−CEStat
Co−CEStat
Figure 5.10: Residual energy of network
49
Chapter 6
Conclusion and Future Work
50
6.1 Conclusion
In this thesis, four network layer protocols are proposed for WBANs. The first
proposed protocol, CEMob, is an energy efficient routing protocol for WBANs
which exploits both single-hop and multi-hop communications in heterogeneous
network. It avoids transmission of similar information to preserve energy of com-
municating nodes. Moreover, effects of body mobility, on communication between
nodes, are also observed in this work. Performance comparison of CEMob with two
existing routing protocols; ATTEMPT and RE-ATTEMPT, shows that CEMob’s
performance is superior in terms of energy efficiency. CEMob has 23% and 77%
more stability period than ATTEMPT and RE-ATTEMPT, respectively. Sec-
ond protocol, Co-CEStat, is a cooperative routing protocol for WBANs. Purpose
of this research is to exploit cooperative routing in heterogenous network to en-
hance WBAN’s performance in terms of throughput. By avoiding repeated data
transmission, Co-CEStat achieves greater stability period. Whereas, use of co-
operative routing increases the overall network throughput due to availability of
more than one link for transmission of same data. Simulation results of Co-CEStat
are compared with already designed routing protocols; RE-ATTEMPT and RE-
CEStat. Performance comparison shows that Co-CEStat has 51% and 52% higher
throughput than RE-CEStat and RE-ATTEMPT, respectively. Thirdly, we pro-
posed two incremental cooperative communication protocols; InCo-CEStat and
EInCo-CEStat, to enhance the performance of Co-CEStat protocol. These pro-
tocols utilize incremental cooperation to improve energy efficiency and PER of
Co-CEStat in the presence of AWGN and fading channel. Network throughput is
enhanced by propagating independent signal through different paths. Whereas, en-
ergy efficiency is improved by utilizing incremental relay-based cooperation which
saves channel resources by ensuring that relaying process is adaptable to channel
conditions. Simulation results show that InCo-CEStat is 17% more energy efficient
than Co-CEStat, whereas, EInCo-CEStat has 12% and 5% more throughput than
InCo-CEStat and Co-CEStat, respectively. This type of cooperative transmission
improves number of successful packets received at sink and achieves higher energy
savings than Co-CEStat.
6.2 Future Work
In future, we aim to analyze and deal with multiple BANs along with mobile
sink concept in our work. Research is being done in WSNs to achieve higher
energy savings and greater network lifetime with sink mobility [39-42]. We want
51
to implement such sink mobility in our WBAN protocols in future. Our focus
will also be on secure and reliable delivery of information for critical data of
WBAN [32]. For this purpose, we are required to study and analyze different QoS
requirements, bandwidth limitations and other challenges to design an efficient
routing protocol as in [43-45]. Our goal is to implement these features in our
WBANs protocols.
52
Chapter 7
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Chapter 8
List of Publications
59
1. S. Ahmed, N. Javaid, S. Yousaf, et al., “Co-LAEEBA: Cooperative Link Aware
and Energy Efficient protocol for Wireless Body Area Networks”, accepted in
Computers in Human Behavior (in press), 2014 (IF=2.2).
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bility Support in WBANs”, The 28th IEEE International Conference on Advanced
Information Networking and Applications (AINA-2014), Victoria, Canada, 2014.
(Chapter 3 in thesis)
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for WSNs”, The 28th IEEE International Conference on Advanced Information
Networking and Applications (AINA), Victoria, Canada, 2014.
4. S. Yousaf, et al., “Co-CEStat: Cooperative Critical Data Transmission in
Emergency in Static Wireless Body Area Network”, The 9th IEEE International
Conference on Broadband and Wireless Computing, Communication and Appli-
cations (BWCCA’14), Guangzhou, China, 2014. (Chapter 4 in thesis)
5. S. Yousaf, et al., “Incremental Relay-based Co-CEStat Protocol for Wire-
less Body Area Networks”, The 9th IEEE International Conference on Broad-
band and Wireless Computing, Communication and Applications (BWCCA’14),
Guangzhou, China, 2014. (Chapter 5 in thesis)
6. S. Yousaf, et al., “Reliable and Energy Efficient Incremental Cooperative Com-
munication for WBANs”, submitted in IEEE ICC (International Conference on
Communcation) SAC-Communications for E-Health, 2015. (Chapter 5 in thesis)
7. S. Yousaf, N. Javaid, et al., “Incremental Cooperative Communication for
Improving Reliability in WBANs”, submitted in IEEE transactions on Mobile
Computing. (IF=2.9) (Chapter 5 in thesis)
60
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