Energy efficient wireless sensor MAC protocol 

Introduction and Problem definition 

Wireless sensor networks and the corresponding applications are widely used these days and have greater range of applicability across many areas like environment monitoring, medical systems, smart spaces and also robotics. In general a typical wireless sensor network contains number of individual and well configured nodes and operates under a supervision known as a centralized server.

A typical node across the wireless sensor nodes contains one or more sensor nodes, embedded processors and operates with the help of battery power. Each sensor node has some memory and battery capacity and operates with the mutual interaction among the other nodes and also sends the frequent updates of the network across the nodes. A task across the communication process is achieved by these nodes through the mutual cooperation among the sensor nodes.

Successful operation among the sensor nodes is mainly achieved with the implementation of the Medium Access Control (MAC) protocol like any other shared medium communication. In general there could be some chances, where two or more interfacing nodes act on a single communication attribute and cause the collision due to the single time transmission at the network level. It is the fundamental task of the MAC protocol to avoid these types of collisions across the wireless sensor networks and also reduce the energy consumed due to these collisions across the network .

These types of collisions are common across the wireless data and voice communication and the perfect implementation of the MAC protocol is required at this level. There are many MAC protocols developed and discussed across the literature that can be used to reduce the collisions across the wireless sensor networks due the wireless data and voice communication process.  Time division multiple access (TDMA), Code division multiple access (CDMA) and IEEE 802.11 are the few examples of the MAC protocols that can be used in this context to reduce the collisions across the wireless sensor networks. The implementation and functionality of any perfect MAC protocol depends on various factors and few of them are as discussed below 

Energy efficiency of the MAC protocol can be considered as the important and key issues that should be achieved at any cost for the perfect operation of the MAC protocol. In general the sensor nodes across the wireless sensor networks operate with the help of battery power and the consumption of the power would be very high in terms of energy due to the operation and maintenance of the MAC protocols. If this is the case, changing the batteries or recharge the existing batteries is really difficult in this scenario and thus reducing the power is the best way to increase the energy efficiency rather than changing or recharging as discussed.

If the power of the batteries is expired, it indicates that the overall performance of the network is reduced a lot and finally the life time of the wireless sensor network is reduced with respect to these issues. Apart from the energy efficiency, another important factor that determines the performance of the MAC protocol that is being implemented across the wireless sensor network is the scalability. In general the scalability is something that deals with the adaptability of the network to change as per the existing conditions like the change in topology, number of nodes and the present communication pattern being followed across the wireless sensor networks.

Across a typical wireless sensor network there could be some chances where some nodes may be expired due to many reasons, some nodes may join the network later and some nodes may change their location and destination due to several conditions like congestion and density across the wireless sensor networks.  The reliability of a good MAC protocol depends on the level of adaptability shown by it to accept these network and topology changes due to many reasons. Apart from these two factors like energy efficiency and scalability there are few other important factors like fairness, bandwidth utilization, throughput and latency, but these are secondary across the wireless sensor network, where they are given the primary focus across the wireless voice and data communication mechanisms .

As discussed there are many existing MAC protocols and it is proved that they fail across any of the above mentioned conditions like, if a protocol is capable of achieving the energy efficiency another may fail due to the scalability issues and vice versa and one more thing that should be given across these MAC protocols is that they are more generalized and not made in specific to meet the requirements of wireless sensor networks. To meet the more specific needs of the wireless sensor nodes like the radio used across the sensor nodes consumes more energy across the MAC layer and there is also a need of a more specific sensor MAC protocol.

The basic requirements for a MAC protocol across the wireless sensor network should be energy efficient and scalable and should make the network adopt the frequent changes across the wireless sensor networks. The main aim of this project is to design and implement a sensor MAC protocol (S-MAC) to reduce the energy consumption and also improve the scalability of the network and incorporate the collision avoidance mechanism to reduce the usual collisions that are caused across the sensor nodes of the network. To proceed with the research following research questions are identified 

  • What is the role of energy across the wireless sensor networks and how it is affected due to scalability and collisions across the wireless sensor networks?
  • How to design a sensor MAC protocol (S-MAC) to improve the energy efficiency across the wireless sensor networks?

Aims and Objectives 

Following are the aims and objectives of this project 

Aim: To design and implement a sensor MAC protocol (S-MAC) to improve the energy efficiency and scalability across the wireless sensor networks using OPNET modeler simulation tool. 

Objectives

  • To critically review different MAC protocols and evaluate their performance with respect to energy consumption
  • To analyze the importance of a specific sensor MAC protocol across the wireless sensor network to improve the energy efficiency and scalability across the network.
  • To design the simulation model for S-Mac protocol and compare with the existing MAC protocols like IEEE 802.11.
  • To develop the simulation to evaluate the performance of S-MAC using OPNET modeler.
  • To evaluate the comparison results and review the performance of S-MAC protocol across the wireless sensor networks with respect to energy efficiency and scalability. 

Literature review 

In general the communication patterns across the wireless sensor networks has many layers involved like any other network and these layers are really important to decide the performance of the network. Among several layers present at the communication level of the wireless sensor networks, medium access layer (MAC) plays a vital role across the wireless sensor networks and used for many important aspects across the network like reducing the collision across the sensors due to the single time transmissions. MAC protocol ensures a perfect and collision free communication among the sensor nodes, where the chances of collision among the sensor nodes during the transmission process are reduced a lot .

Apart from these communication issues, energy efficiency also plays an important role across the wireless sensor nodes and in general these nodes operate using the battery power and the power of these batteries is reduced due to lot of issues across the wireless sensor nodes. The usual power consumption mechanisms across the wireless sensor networks include the radio that operates across the sensor nodes, transmission, receiving and scanning operations across the communication process also consumes lot of energy in this context.  In general there are different types of MAC protocols like TDMA, CDMA and IEEE 802.11 where the maximum concentration of these protocols is done at the factors like bandwidth utilization, throughput and latency and ignores the important aspects like energy efficiency and scalability.

Energy utilization has an important role across the wireless sensor networks and there are many traditional MAC protocols that were implemented to reduce the battery power consumption across the network. The basic implementation that was followed across the wireless sensor networks is that, setting the sensor nodes to sleep and idle conditions and thus saving the battery power as much as possible. 

TDMA MAC protocols can be considered as the energy preserving protocols, as the functionality of these protocols does not consume lot of energy due to regular sleep mode instructions passed by the protocol and duty cycle implemented across the protocol implementation. Even TDMA MAC can be considered as the energy efficient in terms of the duty cycle, there are some disadvantages with this implementation like schedule maintenance of the TDMA MAC is really a tedious task at the wireless sensor networks. Schedules of the neighbors across the wireless sensor networks are also important and across the implementation of the TDMA MAC, maintaining these schedules is a bit memory consumption process and thus finally the energy is also affected due to these issues and thus this type of MAC protocol is not perfectly suitable for wireless sensor networks.

Apart from the TDMA MAC approach, the other alternative way to reduce the power is to a use an extra radio across the sensor nodes called as wake up radio and operates at a different frequency range across the communication. Wake up radios are used to wake up the other sensor nodes and thus does not need any further data processing requirements and thus the energy is saved across this type of radios for the wireless sensor networks. Even this type of wake radio implementation is proved to be an energy efficient approach, adding an extra component is not as easy as discussed and with this the complete technical implementation metrics of the wireless sensor nodes are affected a lot.

Current MAC protocols across the networks can be broadly divided in to two types like content based and TDMA based and the basic operation range of TDMA based MAC protocol is discussed above. Content based MAC protocols can also considered as the energy efficient in several aspects and the best example for this is the IEEE 802.11 protocol and this protocol can be considered as the energy efficient protocol even across the operation at the ad hoc level. This type of MAC protocol is best suited for the networks, where all the nodes across the network are located at single cell location, where as the typical wireless sensor nodes are widely spread and operates across the multi-hop environment and thus IEEE 802.11 MAC protocol can’t be considered as the required energy efficient solution for the wireless sensor networks. 

Thus it is clear from this review that, even there are many existing MAC protocols like TDMA, CDMA and IEEE 802.11 and proved to be energy efficient with respect to different issues; the key and common limitation among this protocol implementation is that, they are more generalized and can’t be applied across the wireless sensor networks. To solve all these issues in a possible manner, a more specific MAC protocol with respect to energy efficiency and scalability across the wireless sensor networks is always required.

The primary goal of this protocol should be to achieve maximum energy efficiency and improve the scalability and also to reduce the collisions across the wireless sensor networks due the transmission issues across the interfering sensor nodes and the design of this protocol should be compared to the existing once to evaluate the performance. The performance of the sensor MAC protocol is evaluated in this research and it is compared with the existing protocols like TDMA and IEEE 802.11 in terms of the energy consumption and scalability issues. 

Research methodology 

Quantitative research methodology is followed in this project. In general a quantitative research methodology is the one which can be used compare different results like graphs and charts and these graphs are used to evaluate the performance of any particular system in comparison with an existing or reference system. As the main aim of this project is to evaluate the design of a new sensor MAC (S-MAC) protocol, the proposed protocol is designed using a typical wireless sensor simulation model. OPNET modeler is used as the simulation tool in this project and it can be used to create multiple scenarios and compare the scenarios using the graphs and thus quantitative method of research is appropriate in this project.

Initially two scenarios are considered in this project to evaluate the energy efficiency of the wireless sensor networks using the S-MAC and to proceed with this research two MAC protocols are considered like IEEE 802.11 and S-MAC. Few performance metrics are considered with respect to these two protocols and simulated across the wireless sensor network and individual scenarios are created against the performance metrics. Once these two scenarios are considered and created, individual performance and comparison of the scenarios are evaluated to test the simulation done and also energy efficiency model of the S-MAC is determined. 

Project plan 

Task Description Start Date  End Date  Duration
Introduction  Basic introduction to the project along with the problem definition and aims and objectives are defined in this section.      2 weeks 
Literature review  Following topics are covered under the literature review 

  • Introduction to MAC layer its importance across the networks and communication process
  • Review on different MAC protocols and their implementation procedure towards the energy efficiency across the wireless sensor networks
  • Review on limitations of the existing MAC protocols with respect to the wireless sensor networks and energy consumption aspects
  • Review on wireless sensor network issues like energy, scalability and collision and analysis of the required MAC protocol to achieve the desired energy efficiency and scalability.

 

    4 weeks 
Simulation design  Following design aspects are discussed in this section

  • Introduction to OPNET modeler as the required simulation tool
  • Parameters description of the scenarios
  • Detailed design procedure of the scenarios
  • Explanation to performance evaluation metrics like energy consumption and energy savings

 

 

    3 weeks 
Simulation procedure  Following aspects are covered under this chapter 

  • Detailed explanation to the scenarios considered
  • Steps explaining the simulation procedure to be followed using the OPNET modeler across the scenarios
  • Simulation steps and the corresponding screenshots
  • Procedure to setup the required wireless sensor network and the corresponding MAC protocols
  • Explanation to parameters setup and running the simulation process

 

 

 

 

    4 weeks 
Evaluation of results  Results achieved after running the individual scenarios and after comparing the scenarios are explained in this chapter with reference to the aims and objectives of this project.      2 weeks 
Conclusion and Future work   Conclusion from the total work done and the results evaluation is given and the better ways to improve the project in future are also explained.      1 week