International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 5, May 2012)123
Real Time Data Communication Medium access control
(RC-MAC) Protocol for Wireless Sensor Networks (WSNs)
Umesh Kumar Singh
1, Kailash Chandra Phuleriya
2, RamJi Yadav
3 1,2,3 Institute of Computer Science, Vikram University Ujjain (M. P.)INDIAkailash.phuleriya@gmail.com
Abstract - Reliable data communication in Real Time is one of the most important requirements in Wireless Sensor Networks where different applications have different reliability requirements. Assuring reliable data delivery in real time between sensor nodes and the sink node in WSNs is a challenging task. Most of the existing medium access control protocols only provide reliable data delivery with either congestion control or energy efficiency but not do provide both simultaneously. In this paper, we have made a survey on the existing medium access control protocols and proposed a new Real Time Data Communication medium access control (RC-MAC) protocol for wireless sensor networks.
Keywords-- Real-time, Energy Efficiency, Congestion control, MAC, and WSNs.
I. INTRODUCTION
Wireless Sensor Networks [1, 2], is an emerging technology that has become one of the fastest growing area in the communication industry. It consist of sensor nodes that use low power consumption which are powered by small replaceable batteries that collect real world data, process it and transmit the data by radio frequencies to their destination. A reliable protocol in wireless sensor network is a protocol that allows data transfer reliably from source to destination with reasonable packet loss. The IEEE 802.15.4 [3] standard has received considerable attention as a low data rate and low power protocol for wireless sensor network applications in industry, control, home automation, health care, and smart grids [3-4]. The wireless sensor network (WSN) is made of hundreds or thousands of sensor nodes to cooperatively monitor different condition, such as temperature, sound, vibration, pressure and motion at different locations which is the common task of sensor node is to collect the information from the view of event and send the data to a sink node.
Reliability is especially important for wireless sensor networks since the wireless channel is inherently random and error-prone. Moreover, sensor networks are generally deployed in unfriendly terrains and consist of a crowded deployment of sensor nodes.
This leads to throughput poverty due to hidden terminal problems, multipath fading and packet loss due to channel contention.
Also, for many real-life applications of sensor networks, a critical event detected by the sensor network should be delivered to the user as soon as possible. Energy conservation, on the other hand, is one of the most important design parameters for wireless sensor networks. Being battery operated, sensor nodes require energy conservation mechanisms so as to ensure the extended network lifetime the most crucial requirement is reliable data communication in real time. We have investigate the various reliability strategies employed in wireless sensor networks and discuss their applicability to differing kinds of errors and the amount of delay typically suffered by their use. Figure 1 shows the typical wireless sensor network that consist of multiple number of sensor nodes and 3-sink node where data is collected are deployed in the sensing field.
Fig.1 wireless sensor network
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 5, May 2012)124
II. RELATED WORKThe basic requirement of a sensor network is reliable delivery of data with minimum latency and energy consumption. There are several MAC protocols that have been designed for wireless sensor networks. These protocols can be categories into: contention based, scheduling based, collision free and hybrid protocols. Shown in following fig. 2.
Fig.2.Classification of MAC protocol design approach
Accessing the MAC layer may lead to errors in some particular cases. It is often assumed, incorrectly, that node connectivity is bi-directional and this is sometimes not the case. In these particular instances MAC layer errors can potentially occur. Contention based MAC protocols, whether using collision avoidance or not, falls foul of this condition via the hidden terminal problem. Typically, collision avoidance schemes assume bi-directional connectivity while CSMA schemes explicitly ignore the problem. Results from [5, 6] suggest that bi-directional connectivity assumptions are unrealistic. Other MAC protocols which coordinate with other nodes in order to automatically configure themselves may also be susceptible to errors caused by asymmetrical connectivity. This is particularly true where automatic clustering and synchronization is involved. Wei et al [7], presented sensor-MAC (S-MAC), Sensor MAC (S-MAC) is a contention based protocol proposed for energy constrained devices. Based on CSMA mechanism, it essentially trades energy for throughput and latency by utilizing the sleep mode of the radio. Each node then switches to sleep mode for scheduled periods of time in a TDMA fashion. The protocol, however, fails to deliver reasonable throughput at higher loads. Tijs van dam [8] et al, introduced T-MAC, a contention based Medium Access Control protocol for wireless sensor networks.
Timeout-MAC enhances the performance of SMAC for higher loads, while Dynamic Sensor-MAC [9] reduces its overall latency. Tao Zheng [10] et al, proposes a new MAC protocol, called PMAC, where the sleep wake up times of the sensor nodes are adaptively determined.
The schedules are decided based on a node’s own traffic and that of its neighbors. Sung-Chan Choi [11] et al, proposed PS-MAC (Probability Sensor-MAC), a time slotted MAC protocol like S-MAC but unlike SMAC in which all nodes have the same synchronized and periodic listen and sleep cycle, in this protocol, different transmitter and receiver node pairs have asynchronous and non-periodic listen and sleep schedules.
TRAMA [12] is an energy efficient collision-free channel access protocol for WSN. TRAMA reduces energy consumption by ensuring that Uni-cast, multicast, and broadcast transmissions have no collisions, and by allowing nodes to switch to a low-power, idle state whenever they are not transmitting or receiving. MMAC [13] is a scheduling-based protocol and thus it guarantees collision avoidance. MMAC allows nodes the transmission rights at particular timeslots based on the traffic information and mobility pattern of the nodes. A large amount of work-has been focused on Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), and Energy Efficient MAC Protocol for Sensor Networks (EMACS) etc. TDMA allows several users to share the same frequency channel by dividing the signal into different time-slots. Zebra MAC (MAC) [14] is a hybrid protocol based upon CSMA. Z-MAC uses CSMA at the base but follows TDMA depending on the contention level. The overhead of Z-MAC protocol is the setup phase, which is done at the beginning. In the setup phase, the nodes are assigned with the timeslots for the data transmission. RT-Link [16] focuses on reducing the communication delay between a node and the base station. It uses a centralized slot computing mechanism, using the distance-k node coloring approach (slot scheduling), to minimize the number of collisions along each transmission hop in a multi-hop wireless network.
Wan Mohd et al [17], present a novel approach that tries to reduce idle energy consumption by implementing scheduled active-sleep algorithm named energy aware A-MAC protocol. From the computational model, we show that the algorithm can prolong the network lifetime by switching to sleep mode when there is no packet scheduled to be transmitted or received. Simulation study also has been done to prove the A-MAC algorithm can prolong the network lifetime compared to the classical CSMA approach.
MAC PROTOCOL DESIGN APPROACHES
SCHEDULING BASED
COLLISION FREE
HYBRID CONTENTION
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 5, May 2012)125
III. CHARACTERISTICS OF RELIABLE AND ENERGYEFFICIENT MAC PROTOCOLS
The following attributes are to be considered, while designing a good MAC protocol for the wireless sensor networks:-
Latency: Latency requirement basically depends on the application. In the sensor network applications, the detected events must be reported to the sink node in real time so that the appropriate action could be taken immediately.
Reliability: Reliability in wireless sensor networks can be examined from both the packet level and the event level. Packet level reliability refers to how many packets are successfully received at the final destination. Event level reliability refers to the delivery of certain data objects or events to the receiver.
Energy Efficiency: The sensor nodes are battery powered and it is often very difficult to change or recharge batteries for these sensor nodes.
Fairness: In many sensor network applications when bandwidth is limited, it is necessary to ensure that the sink node receives information from all sensor nodes fairly. However among all of the above aspects the energy efficiency and throughput are the major aspects. Energy efficiency can be increased by minimizing the energy wastage.
IV. PERFORMANCE MATRICES FOR MAC PROTOCOLS
The research community considers the following matrices in order to evaluate and compare the performance of real time data delivery and energy conscious protocols.
A. End-to-End Reliability
End-to-End Reliability metrics are concerned with reliable data Delivery in real time to all the direction of data flow such as upstream (sensor-to-sink) and downstream (sink-to sensor). End-to-End Reliability in WSN can be classified into two categories which are packet reliability and event reliability. Packet reliability which is applications is loss sensitive and requires successful transmission of all packets. While event reliability is how well an event is reported to the base station. End-to-End reliability for i nodes is defined as follows:
( )
B. Energy Consumption per Bit
Sensor nodes have limited energy and it is important for the transport protocol to maintain the high energy in order to achieve maximize system lifetime.
The energy efficiency of the sensor nodes can be defined as the total energy consumed / total bits transmitted. The unit of energy efficiency is joules/bit. Packet loss in WSN can be common due to bit error or congestion. Thus, the packet loss ratio can be calculated as follows:
Packet loss ratio will results for energy loss per node and the whole network which is important to evaluate energy efficient at medium access control protocol. Assuming dropped packets have a direct relation with energy wastage, the energy loss per node can be measured by as follows:
( )
Whereas the energy loss for the whole network can be calculated as follows:
C. Congestion Control
Congestion degree, d is congestion detection metric that defined by:
( )
Where, is the mean packet servicing time and is the mean packet inter-arrival time of node i. The average delivery ratio is calculated as:
V. PROPOSED WORKS
Since the main function of medium access control protocol is to provide reliable data delivery in real time and congestion control, hence that will be primary focus on sub layer of data link layer called MAC layer. Due to the unique characteristic of WSN, the MAC protocols should have the requirements as the following:
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 5, May 2012)126
Congestion control: Since congestion increases packet loss and energy consumption, congestion control is need to avoid or reduce packet loss, results in high link utilization and low packet delay. Provide cross layer optimization with the others layer (i.e., transport layer and physical layer) to achieve gains in overall system performance in wireless network
Be able to cope with the variable reliability that required by the applications.
[image:4.612.321.552.366.563.2]Now we have concentrated the OSI Reference model, the International Standards Organization (ISO) has defined a networking model known as the Open Systems Interconnection (OSI) model [17]. The OSI model is a 7-layers model. The application, presentation and session layers also called upper layer and the transport, network, data link and physical layers also called Lower layers. Now we have studies the part of data link layer in Open Systems Interconnection (OSI) model, called as medium access control (MAC) layer, which sits on peak of physical layer as shown in Fig. 3. Therefore, the medium access control layer, controls the physical (communication device), it has a large collision on the on the whole energy consumption, and hence, the natural life of a node.
Fig.3 comparison of 7-layers OSI with 4-layers DOD model [18].
The process for reliable data transfer in real time and congestion control at MAC layer is shown in figure 4.
[image:4.612.61.249.414.643.2]In [15], author proposed a transport protocol for reliable data transfer in WSNs using the three ways which are hop-by-hop reliability, hop-hop-by-hop re transmission timeout and congestion control scheme, we have change the scheme and apply this scheme for medium access layer and proposed a new protocols state diagram. This proposed protocol can be dividing into three sections, which are End-to-End reliability, End-to-End retransmission timeout and congestion control scheme. The main part of the process is End-to-End reliability that has four state conditions. This state diagram shows the process for sending data from transmitter (sensor node) to receiver (sink node). If the congestion is experience during data transfer, the congestion control will take a part of the process. While if the timeout is occurring before packets successfully transmit, the mechanism of End-to-End retransmission timeout will play the role. Finally, to calculate the performance of proposed RC-MAC protocol, the formula from section 4 will be used.
Fig. 4. State Diagram of MAC protocol process.
VI. CONCLUSION
In this paper, we had made a survey on the existing several medium access control protocols. The current issues of medium access control protocol are how to implement reliable data communication in real time, congestion control and energy efficient. We have proposed a new Real Time Data Communication medium access control (RC-MAC) protocol for WSNs.
PROCESS/ APPLICATION
HOST-TO-HOST
INTERNET
NETWORK ACCESS APPLICATION
TRANSPORT PRESENTATION
SESSION
NETWORK
DATA LINK Medium Access Control
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, Volume 2, Issue 5, May 2012)127
The most important functions of RC-MAC protocol should be focused including provide an End-to-End reliable data communication, Energy Aware and effective congestion control mechanism. Both factors of congestion control and End-to-End reliability will helps in reducing packet loss which result in an energy efficient for operation of the network. Furthermore the proposed protocol will increase the lifetime of the sensor network. To the best of our knowledge, looking onto the positivity of the concept given by as, we can say that it might be very useful to solve the problem of Real time data Communication on Wireless Sensor Networks. In future we have done the simulation work on the based this protocol architecture I hope this is provide a based architecture for solve the problem of real time data delivery and energy efficiency.REFERENCES
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