Towards Improving the Quality of Present MAC Protocols for LECIM Systems

Wireless networking system is quickly growing in the field of communication technology due to its usefulness and huge applications. To make the system more effective to the users its lower energy consumption, security, reliability and lower cost issues must be considered under any circumstances. Low energy wireless is exceedingly required because the sensors are frequently located where mains power and network infrastructure are not reliably available. The recent development of Low Energy Critical Infrastructure Monitoring (LECIM) has vast applications including: Water leak detection, Bridge/structural integrity monitoring, Oil & gas pipeline monitoring, electric plant monitoring, public transport tracking, Cargo container monitoring, Railroad condition monitoring, Traffic congestion monitoring, Border surveillance, Medical alert for at-risk populations and many more. This proposal Low Energy Critical Infrastructure Monitoring (LECIM) is proposed by the Task Group 4k under IEEE P802.15 WPAN. Although many issues related to its quality are involved, but several Media Access Control (MAC) protocols with different objectives were proposed for LECIM. In this research paper, issues related to energy consumption and wastage in LECIM system, energy savings mechanism, relevant energy conscious MAC protocols have been briefly studied and analyzed. Science Direct, Elsevier, Springer, IEEE Explore, Google Scholar and Wiley digital Library databases were used to search for articles related to the existing MAC protocols well suited for LECIM system. Finally, some ideas have been proposed towards developing energy efficient MAC protocol for LECIM applications in order to fulfill and satisfy the major issues of LECIM quality. Keywords—wireless networking; LECIM; IEEE P802.15; WPAN; MAC


INTRODUCTION
In the practical point of view the usefulness of wireless sensor networking (WSN) system requiring certain criteria including lower energy consumption, security, reliability and lower cost.Low energy wireless is particularly required because the sensors are commonly located where mains power and network infrastructure are not reliably available.The recent development of Low Energy Critical Infrastructure Monitoring (LECIM) has vast applications including: Water leak detection, Bridge/structural integrity monitoring, Oil & gas pipeline monitoring, electric plant monitoring, public transport tracking, Cargo container monitoring, Railroad condition monitoring, Traffic congestion monitoring, Border surveillance, Medical alert for at-risk populations and many more.
Low Energy Critical Infrastructure Monitoring (LECIM) is proposed by the Task Group 4k under IEEE P802.15 WPAN.
Although many issues related to developing efficient LECIM applications can be summarized like, protection of the sensed data, accessing the shared medium in LECIM network; endpoints sleep time; proper coordination between coordinator and endpoints basically the way of knowing how the endpoints will know that the coordinator wants to send them the data is a challenging job where battery power must work for several years; lack of energy conservation mechanism related to its quality are involved, where most of the existing MAC protocols that support wireless sensor networks can"t support these issues properly; formative the status of the channel, in LECIM this is very important because most of the nodes in LECIM system are situated in long distance and the distance among the nodes are also long, the large number of endpoints are also a significant factor.In order to solve this problem the existing contention-based and scheduled-based MAC protocols are not the appropriate solution, it needs to give more attention to solve the above mentioned problems.In this paper, we are expecting to analysis and propose some new ideas for improving MAC protocol for LECIM system, which could fulfill and satisfy the major issues of LECIM quality.
The rest of the paper is structured as follows.In Section II, major challenges, constraints and characteristics of low energy critical infrastructure monitoring; in Section III, sources of energy wastage in LECIM system are studied; in Section IV, we discussed communication patterns and energy consumption measuring system; in Section V, we discussed some mechanisms to reducing energy wastage in LECIM; in Section VI, major MAC requirements for LECIM system are defined, in Section VII, MAC protocol types in applications of LECIM system are briefly discussed; in Section VIII, we proposed some ideas for improving better performance and energy efficiency in MAC for LECIM system.Finally, we concluded and discussed future work in Section IX.

II. MAJOR CHALLENGES, CONSTRAINTS AND CHARACTERISTICS OF LOW ENERGY CRITICAL INFRASTRUCTURE MONITORING
Efficient LECIM network including its infrastructure and applications is the important issue for LECIM system.The IEEE TG4K group facilitates single point to several thousands of point"s communication for critical infrastructure monitoring containing one coordinator and multiple end points.In this www.ijacsa.thesai.orgprocess, coordinator is mains powered and end points are battery powered [1] [2].The main characteristics and challenges for LECIM system is illustrated in the following  Sensor node in WSN, the main sources of energy consumption, is divided into three activities including (a) sensing, (b) computation (data processing), and (c) radio operations or communication.Out of those three sources, energy loss due to radio operation or communication for data transmission is the maximum one where energy consumed for radio transmission is directly proportional to distance [6] [7] [8].
Energy waste through communication depends on sensor nodes include theses technological and physical characteristics such as collision, overhearing, control packet overhead, over emitting, idle listening, traffic fluctuation, packet forwarding, excessive state changes of the radio circuit, increased latency [9]- [13].It"s notable that, idle listening is a major cause of energy waste [14].

Idle Listening
Occurs when the radio of the node is always on and listening to idle channel or medium even while there is no transmission.This is another source of wasting energy.

Over emitting
Messages or packets are continuing to transmit even when the destinations are not ready for receiving them; as a result, energy for sending the message is wasted.

Overhead
Control data or frames or packets containing protocol information which are transmitting or exchanging instead of application data.Energy is consumed for transmitting and receiving these frames within medium or channels.This results in wasted energy.

IV. STUDY AND ANALYSIS OF SOURCES OF ENERGY WASTAGE IN LECIM SYSTEM
Several communication models namely broadcast, converge-cast and local gossip in WSN has been used for short and long distance based applications [15].Transmitting necessary information to all the sensor nodes of the network a broadcast pattern is used by a sink node; in converge-cast pattern a group of sensors communicate to a specific sensor; and the sensors that detect an event communicate with each other locally is defined by local gossip pattern.Energy consumption in communication pattern depends upon its operating states which are divided into four sub-states namely www.ijacsa.thesai.orgtransmit state, receive state, idle state, and sleep state.Transmit and receive states are used for sending and receiving data; the default state of WSN is idle state, and sleep state consumes very less energy than any other above mentioned states [16] [17].Average power consumption of different substates in operating state is defined by the following ratio [18]: Transmit: receive: idle: sleep= 40.25%: 29.1%: 25.3%:5.4%Total energy consumption "E" in operating state to transmit "k" bit is illustrated by the following equation [19]: Where Pactive , Psleep , Ptransient , Pidle are the power consumption and Tactive , Tsleep , Ttransient , Tidle are the interval or duration of time that a transceiver waits or stays at its active, sleep, transient and idle mode respectively.

V. MECHANISM TO REDUCE ENERGY WASTAGE IN LECIM
In order to increase network"s life time and maximizing node in LECIM it"s very important to reduce energy waste throughout the system and to enhance the performance of medium access control (MAC) protocol.Different wake up mechanisms could be used to enhance the performance of MAC protocol.Due to the unlimited power consumption of nodes in LECIM and long duration of operation energy efficiency is an important issue.It is generally not possible and practical to recharge or replace the exhausted batteries for sensor nodes in the network.So enhancing the lifetime of network as well as the sensor nodes means enhancing batteries life time.
As discussed earlier the energy consumption in sleep state is lower than idle listening state, so another good mechanism would be to maximize sleep period of the node in MAC layer, while conserving the highest throughput, the lowest latency, and the utmost energy conserving in a WSN [6].In order to save the transmission energy, several techniques are being used including, energy-aware routing pursuing multi-hop paths, providing time-based medium access control (MAC) by limiting the potential for collisions and minimize the energy consumed in the receiver by turning the radio off when it is idle [20].Power savings mechanism in MAC layer is classified into three basic classes and they are: effective use of the PHY layer services, optimized media access protocol structure, and useful system design [21].
The power or energy saving mechanisms [22] [23] is illustrated in Table III.Idle listening is the major cause of energy waste, so it is important to introduce suitable MAC protocol which can reduce or prevent energy wastes due to idle listening.Four techniques are being used to avoid idle listening including static sleep scheduling, dynamic sleep scheduling, preamble sampling, and off-line scheduling.Several MAC protocols are already been introduces based on these techniques which are broadly classified into: CSMA, TDMA, hybrid and cross-layer optimization [14].Using the mechanism mentioned in the following Table IV we can easily measure the performance of energy conscious MAC protocol [24].In LECIM system the main goal of MAC protocol is to minimize the energy waste due to idle listening, overhearing and collision.

VI. MAJOR MAC REQUIREMENTS FOR LECIM SYSTEM
A different computation and communication infrastructure is provided by WSN which is based on both physical characteristics including the large scale of deployment, inadequate computing capability, and limitations on power consumption; and typical applications including tracking objects or detecting events.As a result, the requirements for the MAC layer of a LECIM system in WSN are clearly different from those for traditional networks [30].The major requirements for the MAC layer in a LECIM system [31] should be as follows as depicted in Table VI.

VII. MAC PROTOCOL TYPES IN APPLICATIONS OF LECIM SYSTEM
Low energy consumption is the major issue in any wireless application including LECIM.Therefore designing, implementation and performance of energy efficient MAC www.ijacsa.thesai.orgprotocol is a vital issue.Contention-based MAC protocols don"t allow communication traffic (flow according to a preset schedule) that"s why it"s a major concern of large energy consumption, but a time division multiple access (TDMA) based MAC allows communication traffic which reduces energy consumption and extends the life of WSNs.In these time-based MAC enabled WSNs, the nodes can turn off their transmitters or receivers whenever it requires and collision among nodes can also be avoided because each of the nodes has its own time slots which reduce wastage of energy in communication.[32] [33].The way of prolonging the network/node lifetime in LECIM depends on energy efficient MAC protocols including synchronous MAC protocols and asynchronous MAC protocols.Energy waste is reduced in synchronization because in this mode nodes keep awake only at a specified time and also synchronous protocols maintain a schedule, where, sensor nodes independently schedule their awake period in asynchronous MAC protocols to periodically check the channel while avoiding the synchronization overhead and introducing long latency and excess energy consumption [34]- [36].
There are five categories of MAC protocols specifically designed for WSNs as mentioned below: 1) Scheduling based or contention free or reservation based or cluster based MAC or channel partitioning MAC or controlled access 2) Collision free MAC protocols; 3) Contention based or channels polling or low power listening or cycled receiver or random access MAC or preamble sampling; 4) Scheduledcontention based MAC protocols or common active period protocol; and 5) Hybrid schemes or protocols.

In the upper portion of both tables, Table VII, Table VIII and Table
As mentioned, most of the existing MAC protocols are designed for a single channel only, they do not operate on Multi-PHYs simultaneously.Since different bands have different characteristics in terms of data rate, number of subchannels in a particular frequency band/channel, and data prioritization where a good MAC protocol for LECIM should enable reliable operation on MICS, ISM, and UWB etc bands simultaneously, hence MAC transparency has been a hot topic for the MAC designers [48].Energy saving or energy consumption issue in LECIM MAC is related to synchronous or asynchronous, beacon or preamble, and different periods of wake up and sleep modes.Idle listening dominates the total energy consumption in conventional power management schemes which is based on either periodic wake-up or sleep schedules.Sleep mode power consumption is much less than idle power consumption, which is near to 0.003 mW [49].
The MAC protocols discussed in Tables (VII-IX) in most of the cases cannot satisfy all the requirements of LECIM.Most of the traditional MAC protocols don"t focus on energy conservation a mechanism which is one of the most important requirements of LECIM; they mainly focused on bandwidth utilization and throughput.On other hand contention-based protocols are used to determine the status of the channel supported by, however, this is not always guaranteed in LECIM due to the long distance among the nodes.However scheduled-based protocols provide good solutions for clear channel assessment problems, but due to large number of endpoints and event based traffic these are also not suitable for LECIM.MAC using wakeup radio is also proposed for better communication in LECIM networks.
Large network size, scalability, energy consumption issue including idle listening and delay, long battery lifetime, and security must be the major design issue for constructing any MAC protocol for LECIM.Result: low energy wasted on idle listening, and high energy wasted on transmissions (long preambles).

VIII. PROPOSED IDEAS
Limitation: Overhearing-non-targeted receivers who sample the channel during preamble transmission have to wait until the end of the preamble to go back to sleep.Energy expenditure is a function of density as well as traffic load, where entire preamble needs to be sent before data transmission.
In terms of throughput and delay it provides a good transaction between energy consumption, complexity and performance.It attains the benefits of scheduled MAC protocols because of its simple operation of unscheduled MAC protocols, as well as the low consumption and cost-free maintaining and sharing the schedule.Excellent for high traffic applications.

5.
The nodes may lose synchronization due to its early sleep problems.
3. This mode is loosely and insecurely synchronized.1.Time Division Multiple Access (TDMA) is a schedule-based or contention-free of cluster-based multiple access technique 2. In this technique transmission of packets are administered in the form of time frames and time slot.3.In this mode, a time slot can be seen as a devoted transmission resource.It"s used to carry data with minimum or no overhead.4. In this technique, the channels are particularly divided into fixed or variable time slots which are assigned to a particular sensor node to transmit during its slot period.5.In this protocol, nodes are collision-free because slots are pre-defined and allocated to individual nodes at the beginning, 6.It requires a good synchronization scheme.7.There are no idle listening and overhearing issues are visible in this protocol due to its reduced duty cycle mechanism.8.It is found that Scheduled-based/ contention-free/ cluster-based MAC Protocol is more appropriate for non-dynamic type of networks (with a limited number of sensors generating data at a fixed rate).
Reasons behind energy efficiency:

IX. CONCLUSION
In this paper, the researchers have presented issues related to energy consumption and wastage in LECIM system, energy savings mechanism.We have also studied and analyzed LECIM relevant energy conscious MAC protocols.Finally, some recommendations have been proposed for developing energy efficient MAC protocol to satisfy the major issues of LECIM quality.

TABLE I .
CHARACTERISTICS AND CHALLENGES FOR LECIM SYSTEM

TABLE III .
CLASSIFICATION OF ENERGY SAVINGS MECHANISMS

TABLE IV .
MECHANISM TO MEASURE THE PERFORMANCE OF ENERGY CONSCIOUS MAC PROTOCOL There are many reasons behind energy consumption in LECIM in WSN as explained earlier.Based on these reasons as mentioned in Table I some approaches are also proposed which are illustrated in Table V below.Approaches those have been proposed in many research papers for wireless systems in general can easily be added to a large variety of WSN MAC protocols.www.ijacsa.thesai.org define energy efficiency of the sensor nodes.The unit of energy efficiency is joules/bit.The lesser the result of ration, the better is the efficiency of a protocol in transmitting the information in WSN by satisfying all the major sources of energy waste in WSN including sleep and idle listening, collisions, overhearing, control packet overhead, message passing, etc.

TABLE V .
APPROACHES TO REDUCE ENERGY CONSUMPTION

TABLE VI .
MAC REQUIREMENTS FOR LECIM SYSTEMS TO ENSURE BETTER PERFORMANCE AND ENERGY EFFICIENCY IN MAC FOR LECIM a) MAC Protocol with adjustable sensor Sleep Mode.b) Reduced idle listening based medium access control (MAC) protocol: idle mode of operation should be minimized.

TABLE VII .
THE MAJOR CHARACTERISTICS OF LOW POWER LISTENING-LPL MAC PROTOCOL, AND A WIDESPREAD STUDY OF THE EXISTING PROTOCOLS IN THE PERSPECTIVE OF ENERGY EFFICIENCY FOR LECIMChannel polling or Low Power Listening-LPLLPL is unable to contain or accommodate a periodic traffic and low duty cycle nodes in wireless sensor network based applications.Channel

polling or Low power listening (contention based LPL) Scheduled listening and LPL Major
reasons of energy wastage in contusion based LPL including: a. node periodically wakes up, b. turns radio on and c. checks channel.

TABLE VIII .
THE MAJOR CHARACTERISTICS OF CONTENTION-BASED MAC PROTOCOL AND A COMPREHENSIVE STUDY OF THE EXISTING PROTOCOLS IN THE CONTEXT OF ENERGY EFFICIENCY IN LECIM

Scheduled-contention/ contention based MAC Protocol/ Random access MAC Basic
characteristics including:1.Contention-based MAC such as Carrier Sense Multiple Access/ Collision Avoidance (CSMA/CA) protocols nodes competes for the channel to transmit data.2. In this scheduled-contention method, nodes must perform clear channel assessment (CCA) before transmission of data.3.In this mode, if the channel is busy, the node defers its transmission till it becomes idle.In a scheduled-contention mechanism, both schemes are combined to gain scalability and to avoid collision during transmission 2. In this mechanism, the nodes become accustomed a common schedule for data communication.3.During a synchronization period of this mode schedules are exchanged periodically.4. If two neighboring nodes reside in two different clusters, they keep the schedules of both clusters resulting in extra energy consumption.5. Listening for full contention period, even listening before transmitting.6.Although the mechanism is synchronous, but low duty cycle nodes don"t need frequent synchronization/exchange of schedules in wireless sensor network based applications.

TABLE IX .
THE MAJOR CHARACTERISTICS OF SCHEDULED-BASED MAC PROTOCOL AND A COMPREHENSIVE AND WIDESPREAD STUDY OF THE EXISTING PROTOCOLS IN THE CONTEXT OF ENERGY EFFICIENCY FOR LECIM

scheduled-based MAC protocols: Adaptability to LECIM Flow-Aware Medium Access (FLAMA) LEACH PACT Ultra low power MAC or BSN MAC
1. Time division multiple access (TDMA) or schedule-based protocol can easily support low duty cycles, which is one of the important reasons of energy efficiency.2. It can easily avoid usage of extra energy that leads reducing energy waste from all major sources [collision, idle listening etc.]. 3. Having low duty cycle nodes it doesn"t require frequent or regular synchronization at the beginning of each super-frame.