2nd Int'l Conf. on Electrical Engineering and Information & Communication Technology (ICEEICT) 2015 Jahangirnagar University, Dhaka-1342, Bangladesh, 21-23 May 2015
An Energy Efficient and Reliable Cluster-based Adaptive MAC protocol for UWSN Nusrat Z. Zenia* , M. S. Kaisert, M. R. Ahmed t, S. A. Mamun § and M. S. Islam �
Institute of Information Technology * t§� Jahangirnagar University, Dhaka-1342, Bangladesh Radar and Radio Commutations - Marine Engineering Department:!: University of Portsmouth at Military Technological College, Oman Email:
[email protected]*. { kaisert.sam§.sislam� } @juniv.edu.muh
[email protected]
Abstract-Now-a-days, underwater sensor network (UWSN) technology is becoming more appealing to researchers because it has introduced a new flux in diversified fields like scientific exploration, commercial exploitation, disaster prevention etc. Since, underwater sensor nodes are battery operated, energy is a fundamental design aspect of UWSN's protocol . Besides, low capacity and high propagation delay introduce large number of packet loss in underwater communication. To, address these issues several medium access control
(MAC)
protocols have al
ready been proposed. T his survey aims to analyze and summarize these protocols and provide a comprehensive overview through comparison and simulation. Moreover, an energy efficient, reli able, cluster based adaptive
MAC protocol (ERCAMAC) has been
proposed to improve reliability and energy efficiency. Simulation results has proved that the proposed protocol provides superior performance in terms of energy saving and throughput over others.
I. INTRODUCTION
The earth is a water planet as 71 % of its surface is covered with water. The oceans contain about 96.5% of all earth water. Surprisingly, we know very little, only less than 10%, about the Earth's water bodies despite of its vital role for nourishment, transportation, presence of natural resources, defence and ad venturous purposes, while a large area still remains unexplored [1]. Recently, ocean bottom sensor nodes are deployed to facil itate scientific and commercial applications, environment and pollution monitoring disaster prevention, tactical surveillance and assisted navigation [2]. To make these applications viable, it is needed to enable underwater communication among un derwater devices [3]. Typical underwater applications require multihop co-operative network where sensor nodes must be able to exchange configuration, location and movement infor mation and to relay data to an onshore station using satellite terrestrial network radio frequency (RF) [4]. However, RF can be propagated through conductive sea water only at low frequencies ranging from 30-300 Hz, requires large antenna and high transmission power [5]. Optical signals also suffer from attenuation and scattering [6]. So, these are not suitable in underwater environment. As an alternative, wireless acoustic sensor network (WASN) appears to be a feasible technology for underwater communication. Acoustic communications are the typical physical layer technology that propagates sound waves to communicate. The typical frequency range is between 10 Hz to 1 MHz. However, the employment of acoustic signals
978-1-4673-6676-2/15/$31.00 ©2015 IEEE
imposes many distinctive challenges. For instance, it suffers from long propagation delays, low bandwidth, frequent loss of connectivity, sound speed variability, limited battery power and much other environmental impairments [7]. The protocols proposed for terrestrial W SN have a poor per formance in underwater environments. Hence, much research works have focused on designing new network infrastructure and protocols suitable for UWSNs. Many research and survey papers have been presented to give a summary of different progresses made to date in the area of UWSNs. Several fun damental aspects of UWASN and possible solution approaches have been outlined in [2]. Salvador et al. have analyzed the security threads of lower layer of the communication stack and have provided a comprehensive overview of current research [3] . Another paper has investigated the research progress in the area of energy consumption and suggested further required researches to increase energy efficiency of the UWSN system [8]. Moreover, review and comparison of different routing schemes has been presented in [9] and [10]. Again, compara tive analysis of some medium access control (MAC) protocols based on network topology has been given in [11]. only a few of them has focused on reliability and energy efficiency and our prime interest is concentrated on them [12]. The methods adopted by those papers to construct energy efficient or reliable MAC protocol are briefly reviewed in the later sections of the review. Furthermore, a new MAC protocol has been proposed by taking both energy and reliability constraint into consideration. The rest of this paper is organised as follows, section II contains network architecture. Section III reviews energy efficiency based MAC protocols and section IV gives idea about reliability based MAC protocol. Section V describes the proposed scheme. Section VI covers Performance analysis. Finally, section VII briefly concludes this article. II. NETWORK ARCHITECTURE
Figure 1 shows a possible architecture of 3D UWSN, where all the sensor nodes are deployed at different depths to convey oceanographic information. Each sensor node monitors local underwater activities and acoustically transmits data to a surface stations through multiple relays. Relays are considered as direct path between source-destination (S-D) pair may very
weak. Each surface station communicates in parallel with underwater sensor nodes using acoustic wave and on shore base stations or satellite using RF wave.
Fig. 1.
Possible architecture of wireless sensor network
Due to the harsh environment, many challenges arise with such architecture like limited bandwidth and capacity, variable propagation delays, high bit error rates and temporary losses of connectivity etc. Most notably, underwater acoustic links are severely prone to packet loss and collision. Moreover, unlike other wireless networks, it is generally hard to charge/ replace the exhausted battery. Hence, energy is a critical factor. So, these should be emphasized while designing and evaluating new protocols. I I I. ENERGY EFFICIENCY BASED
MAC
PROTOCOLS
The purpose of MAC protocol is to manage access to the shared communication medium. For different applications of UWSN, researchers have developed various MAC protocols with different objectives. In this section, efforts are made to provide a comprehensive review of energy efficient MAC protocols to determine their strength and weakness. Mainly, energy wastage at MAC layer are caused by packet collision, idle listening, overhearing and control packet overhead [10] . Collision occurs when a receiver node receives more than one packet at the same time. Collision requires retransmission that increases power consumption and latency. Contention based MAC protocols minimize collision using carrier sense multiple access (CSMA) technique in which the wireless nodes sense whether the medium is idle or not. Tone Lohi (T-lohi) is a tone based contention resolution mechanism intended to provide low energy consumption, high throughput and better channel utilization. Data reservation process of this protocol uses short wake up tone and contender counter. Nodes detect
contender by listening to channel after sending short reser vation tones. If it receives no tone within contention round, it wins the contention and start sending data in reservation period [13]. However, listening to idle channel for possible traffic in duces waste of energy. Consequently, in order to conserve power, several energy efficient protocols are designed to keep network in sleep state instead of idle state. In [14], A latency optimized and energy efficient MAC protocol (LO-MAC) has been introduced for delay sensitive application. At receiver dynamic code rate has been implemented to accelerate data reception rate. The proposed crosslayer scheme has combined the physical layer and MAC layer to shorten transmission delay. On physical layer convolutional coding and interleaver has been applied whereas on MAC layer, an energy efficient asynchronous schedule based MAC protocol (ASMAC) has been enforced. ASMAC protocol has divided the system time into four phases: TRFR phase to send TRFR message by data collection nodes, schedule phase is preserved for data gath ering nodes' schedule broadcasting, on phase and off phase allocated to data collection nodes to turn on and off their radios respectively. Again a distributed, scalable and energy efficient MAC protocol (UWAN-MAC) has been formulated for delay tolerant applications in [15]. The scheduling algorithm devel oped does not require any adjustment to the nodes' timers. Initially all nodes broadcast a beacon signal to announce its transmission cycle. After receiving the signals each node figures out its sleep and wake-up schedule. Data transmission starts from the next cycle according to the schedule established in the initialization phase. The protocol is adaptive to node failures, nodes movement and new nodes deployment. W hen a new node joins in the network, it first listens to the channel to achieve frame synchronization and then broadcasts hello packet to its neighbours to inform them about its existence. A node will judge its neighbour node as failure node if it does not receive any signal from that node for two consecutive cycles. On both the sides of the transmission time, guard time is added to avoid receive-receive (Rx-Rx) collisions. In [16], authors has proposed a reservation based MAC protocol which has reduced the collision probability of data packet by transmitting short RTS packet on an orthogonal low bandwidth control channel. Another reservation based MAC protocol called R-MAC has been designed that allows each node in the network to schedule its transmission of data packet and control packet with the aim of resolving data packet collision and supporting fairness in an energy efficient way. R-MAC works in three phases: latency detection, period announcement and periodic operation. Each node records the propagation latencies and schedule of its neighbours relative to its own schedule in first and second phase respectively. In the third phase, the periodic operation phase, nodes listen/sleep pe riodically to reduce energy waste in idle state and overhearing. RMAC has introduced burst-based acknowledgement where the receiver acknowledge per burst instead of per packet, to improve channel utilization and to solve exposed terminal problem of RTS/CTS [17].
In addition, a MAC protocol has been introduced which was best suited to non synchronized, energy and delay constraint underwater acoustic networks. The protocol minimizes hand shake duration by exploiting receiver tolerance to interference for maximizing throughput and reducing delay. Control pack ets of short duration has been introduced to save energy. The receiver sends a short warning packet to the sender to whom it has sent the CTS if it hears any other RTS during listening period. The sender will wait some time before transmitting the data packet after receiving CTS. It will abort transmission if it receives warning or overhear CTS of other nodes to minimize collision [18]. IV.
RELIABILITY BASED
MAC
PROTOCOL
latency, fairness and reliability are denoted by r, �, p respectively.
T, /'i,
and
TABLE I COMPARISON Of MAC PROTOCOLS
PM
Protocol
Based
Topology
TS
CA
ACK
T-Lohi [13]
Contention
not fixed
x
x
LO-MAC [14]
Schedule
Mobile
V
x
x
x
RMAC [17]
Reservation
Not fixed
x
Contention
adhoc
x
V V
V
UW-MAC [18]
x
K" E r, E
UWAN-MAC
Schedule
x
Rx-Rx
x
E
UWASN
UWASN [15]
dense network
colli-
r, E T, E
sion
Since efficient medium access in underwater is an unre solved problem due to energy limitations, long propagation delays, low data rates and difficulty of synchronization, a range of MAC protocols have been explored to improve the condi tion. However, few of them have considered the reliability of UWASNs. An efficient priority scheduling approach for multi-hop topologies called Routing and Application based scheduling protocol (RAS) has been designed for the MAC layer of the base station (BS) [19]. RAS is then extended to reliable RAS (RRAS) to achieve trade-off between reli ability and efficiency. BS estimates the amount of data to be transmitted and received at each node. RAS calculates a compact schedule at the BS when static routing is applied and for efficient scheduling RAS implements MAC level pipelining by interlacing multiple data transmission. Higher priority for data transmission and reception are given to nodes with heavier traffic. The BS broadcasts the scheduling and routing information to all its children with high power. After receiving routing information and schedule from the BS the nodes perform synchronization to periodically work and sleep. RRAS protocol divides the sleeping period of RAS protocol into small sleeping and retransmission period which can be used to re-transmit the lost data. Another reliable MAC protocol is Multi-session Floor Ac quisition Multiple Access (M-FAMA) which permit session multiplexing and pipelining. It is a greedy protocol that intends to maximize throughput by compensating fairness. Source avoid collision by monitoring MAC level state that includes transmission-reception schedules and propagation delay map of its one hop neighbours. Two M-FAMA variants have been introduced: conservative and aggressive. conservative M FAMA allows multiple session for different source-destination (S-D) pair while aggressive M-FAMA permits multiple session for same S-D pair. M-FAMA has adopted Binary Exponential Back-off (BEB) algorithm to recover control packet from collision [20]. Table I shows the comparison of all underwater MAC protocols investigated in this paper. In the table header CA means contention avoidance, transmission scheduling is ab breviated as TS, PM is refered as performance metrics and ACK refers acknowledgement. Throughput, Energy efficiency,
RRAS [19]
Schedule
Sparse multihop
MFAMA [20]
Contention
mobile UWASN
V.
V
x
V
r, p
V
V
x
r, p
PROPOSED SCHEME
Considering the energy constraint and reliability issues of acoustic communication, in this research, we propose an energy efficient, reliable, cluster based adaptive MAC protocol (ERCAMAC) that unicasts data packet to the intended receiver without collision of control and data packets. The protocol can adaptively change its sleeping and working period based on traffic load which will substantially reduce energy waste and fairness problem. Furthermore, it removes the exposed terminal problem of CSMNCA. Since MAC protocol do not maintain any link state infor mation, we will assume that an efficient routing protocol is working with it. In our proposed protocol, the time frame of cluster head is divided into two broad parts: one part is reserved for receiving data from nodes within cluster and another part is dedicated to communicate with another cluster heads in the network. During inter cluster communication period, the nodes in a cluster except the cluster head remain in sleep mode. Cluster head serves like a gateway to accomplish data forwarding towards the sink. Each part of the time frame is subdivided into scheduling period, working period, acknowl edgement period and sleeping period. Scheduling period is fixed. Others period can change adaptively with traffic load. As shown in figure 2 Schedule period within cluster's node consists of n timeslots to receive RTS (where, n is a number of nodes within cluster) one timeslot to send CTS. Scheduling among cluster heads period consists of k RTS timeslots (k is a number of cluster heads in the network) and one CTS time slot. There is a one to one relationship between scheduling period RTS timeslots and nodes. The ERCAMAC protocol for intra cluster node and cluster head is given in algorithm 1 and 2 respectively To understand the data communication process of ERCA MAC we can consider the scenario of (fig 3). In the scenario, node Nl and N3 has data to send to CHI. N2 and N4 has
no data, so they will remain in sleep mode. CHI will receive RTS from NI and N2 in the reserved RTS timeslots of them. Time slot reserved for N2 and N4 in the scheduling period will be empty. Then, CHI will divide its data communication period into two timeslots. Since NI has more data than N3, timeslot for NI > timeslot for N3. CHI will multicast one CTS that contains the schedule as signed for NI and N3. After receiving the CTS, data sending nodes will send data during their respective timeslot and go to sleep mode until the acknowledgement period. After receiving data successfully, CHI sends acknowledgement to the sender of data. In inter cluster communication period CHI will aggregate the data received from intra cluster nodes and forward them to CH2 following the same RTS-CTS-DATA-ACK mechanism. The whole procedure of data communication is depicted in figure 4
VI.
PERFORMANCE ANALYSIS
This section evaluates and compare the performances of the MAC protocols discussed earlier. For simulation purpose, the following scenario is used. 20 nodes are randomly deployed over 500 x 500m2 area. Transmission range of each node is 50m. The network is assumed to be static that means no nodes can leave or enter the network during simulation. Data generation follows a poisson distribution with average rate A. Parameters used in simulation is given in table n
A. Energy efficiency Analysis In figures 5 to 6, we study the energy consumption of MAC protocols (UWAN-MAC, R-MAC, T-LOHI, UW-MAC, LO MAC and ERCAMAC). Total energy consumption is plotted against total number of traffic packets . For comparison energy consumption of CSMA-CA potocol is also diagramed. As noticed from figures, energy consumption of each protocol follows similar increasing trend. Performance of T-Iohi and UW-MAC is evaluated in figure 5. Compared to CSMA CA and T-LOHI, UW-MAC employes short control packet which introduce s low energy consumption. Figure 6 compares energy consumption of UWAN-MAC, R-MAC, LO-MAC and ERCAMAC. In R-MAC no centralized synchronization is needed. R-MAC can avoid collision , energy waste on idle state and overhearing by adopting periodic listen and sleep mode. In addition the protocol sends acknowledgement on packet per data burst instead of per packet. These are the reasons for the superior performance of R-MAC compared to that of LO-MAC and UWAN-MAC. UWAN -MAC consumes more energy than R-MAC because of collision and overhearing. In case of LO-MAC synchronization is necessary which results in control packet overhead. Increasing number of control packet and dynamic code rate leads more energy consumption . However, Our proposed ERCAMAC has combined clustering technique and burst based CTS, ACK mechanism. Besides, adaptive sleep-wake up method improves the energy efficiency
Algorithm
1: ERCAMAC protocol for intracluster nodes
Notations: Ni
=
intracluster node i; TD(i)
reserved for i; TRTS(i)
=
=
data period
RTS tirneslot reserved for i
= time slot RTS, DATA Result: CTS, ACK
Algorithm
2: ERCAMAC protocol for cluster head
Notation: Pktno packet number; Tsc scheduling period; Tw working period; TACK ACK period ; =
=
=
=
; T
Initialization;
Data:
while intra cluster period do if T
while intra cluster period do if
Ni has data
load;
divides working pe riod according to RTS; multicasts CTS at TCTS including each node's tirneslot from which it has received RTS;
Send RTS at TRTS(i)
sleep until TCT S
T
TCTS then receives CTS ==
extract s
else
TD (i)
if
else I sleep
end
==
TD('i) then
I
sends data sleep until T ACK
I
sleep
if
T
TACK then checks receives data sequence number if receives aLL data then
I
end
T
multicasts acknowledgement to intra cluster nodes ;
else I sends
TACK then receives ACK from cluster head ==
P ktno to missing data node s;
end
else I sleep
else I sleep;
end
end
else I sleep end
==
with corresponding RTS data sequence;
else
if I
Tw then
==
else
end
T
T
for each node Ni that receives CTS; do I receives DATA at TD(i) from Ni;
sleep until TD (i)
if
Tsc then
examines RTS data sequence to estimate traffic
to send to cluster head then
Wake up
if
==
receives RTS from each intracluster node that has data to send during RTS period;
Initialization;
end end
end
end
while inter cluster period do
while inter cluster period do
if receives wakeup signal from cluster head then if data to send then performs contention to get timeslot if receive CTS then I sends data to cluster head else I sleep
if data to send then sends data using the same
procedure of ERCAMAC protocol intrac1uste r period for intracluster nodes;
else broadcasts wakeup tone to intracluster nodes; if receives RTS from intracluster nodes then I sends CTS and receives data;
end
else I sleep
else I sleep
end
end else I sleep
end end
end end performance versus number of nodes. Packet of ERCAMAC than others. B. Throughput Analysis
In figure 7 we compare the throughput performance of M FAMA and RAS with CSMA protocol. figure plots throughput
arrival rate is assumed to be same for each node. It is observed from the figure that M-FAMA outperforms the other protocols. The reason behind it is the greedy behaviour of M-FAMA. M-FAMA also achieve higher throughput by utilizing high propagation dela y through session multiplexing and pipelining. ERCAMAC provides quite same throughput as M-FAMA
TABLE II
SIMULATION Parameter
Value
Tx Power
50W
Rx Power
2W
Idle listening Power
0.45W
Sleep Power
0.05W
Tsync
55. 2ms
Tsleep
4241.8ms
DIP S
10ms
SIFS
5ms
L isten window
65m s
Data packet l ength
120 b ytes
Control packet length
I1bytes
Throughput analysis of M-FAMA.RAS and
0.65
PARAMETERS
CSMA-CA -e--RSA --'$- M-FAMA -e-- ERCAMAC -e--
0.6 0.55
- - - arrival rate
0.5 :;
� OJ :J
e t.l:
0.45 0.4 0.35 0.3 0.25 0.2 0
50001---,----,---,---r;:::===::::;-J
.! c: o
4000
iil 5
e' " c: W
2500 2000 1000 500 20
40
60
80
100 120 140 160 180 200
number of packet
F ig. 5. E nergy consumption of T-Iohi and UWMAC
50001---,----,---,---,.--;=====:::;-J �CSMA-CA
4500
14
16
18
CO N C LUS ION
2014 [5]
C.Petrioli et al. , "A Comparative Performance Evaluation of MAC Protocols for Un derw ater Sen sor Netw ork s", IEEE Conference, Quebec Ci ty, QC, 15-18 Sept. 2008, pp. 1-10.
:J
§ 2500 ()>. e' 2000 "
[6]
L.Brekhovskikh and I.P.Lysanov, "Fundamentals of Ocean Acoustics", Springer: New York, NY, USA, 2003.
[7] J.Cui et al., "Challenges of building scalable mobile underwater wireless
1500
1000 500 OL-���__�__�__�__-L__-L__-L__�__� o
C. Salvador et al., "Underwater Acoustic Wireless Sensor Networks:
Advances and Future Trends in Physical, MAC and R outing Layer s", Sensors, vo1.14( l ) , pp.795-833, 2014. [4] N. Z. Zenia, F. Afsana, M. S. Kaiser, S. A. Mamun, ''Performance anal ysis of LDP C coded wireless ad-hoc network for emergency response communications," Computer and Information Technology (ICClT), 2014
i 3000
�
12
17th International Conference on , vol., no. , pp.446,451, 22-23 Dec.
§
]i
10
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4000
13500
c: W
8
number of nodes
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E"
6
This research work presents review of different energy effi cient and reliable (MAC) protocols. Then, an energy efficient, reliable, cluster based adaptive MAC protocol (ERCAMAC) has been proposed to improve reliability and energy efficiency. Performance of the proposed method has been evaluation and simulation results showed that the proposed protocol provides superior performance in terms of energy saving and throughput over others.
- 1500 � t-
4
VII.
3500
i 3000 ()>.
2
F ig. 7. Throughput analysis of M-FAMA and RAS
4500 E" ..
ERCAMAC
20
40
60
80
100 120 140 160 180 200
number of packet
Fig. 6. Energy cons um ption of R-MAC, UWAN-MAC and LO-MAC
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