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Dr. David Grace
tel: +44 (0)1904 322396
email: david.grace@york.ac.uk

The University of York is a participant in the OPNET University Program, allowing us to use this industry-standard networking simulation tool in both teaching and research within the Communications Research Group.

The Department has considerable expertise in applying OPNET to research problems, with past and current projects in routeing, medium access control and wireless transport layer protocols making use of this resource.

Research Projects

Intelligent Medium Access Control Protocols for Wireless Sensor Networks


Yan Yan, Paul Mitchell, Tim Clarke and David Grace

Wireless sensor networks (WSNs) can help people access a large amount of reliable information from any place, in any environment and at any time. However, large-scale deployments, battery powered sensor nodes, limited radio resource, low computation capability and other unique properties represent serious challenges to the development of WSNs. Therefore, in the majority of wireless sensor network applications it is difficult to achieve high energy efficiency and good network performance.

The aim of the project is to develop an intelligent MAC protocol for WSNs with the objectives of prolonging the lifetime and improving the overall performance of WSNs. In particularly, this project bridges the fields of communication and machine learning. Multiple learning techniques will be investigated in this project, such as reinforcement learning, neural networks, etc. These techniques assist individual sensor nodes to self-organise themselves with the purpose of achieve best scheduling. Compared to existing approaches, the envisaged protocols will provide high throughput and low energy consumption. This adaptability of the proposed approach makes it suitable for a wide range of topologies, with high scalability and intelligent self-organisation capability.

OPNET Modeler is being used to implement and evaluate the proposed ideas and MATLAB is used for the result validation process. Some proposed schemes will be examined through hardware implementation. The key objectives of this project are:

  •     To explore the benefits of machine learning techniques in the design of MAC protocols.
  •     To establish a set of wireless sensor network models in OPNET and implement the proposed ideas using these models.
  •     To develop a complete MAC protocol which is expected to achieve perfect scheduling in a changing environment.
  •     To analyse the simulation outcomes and demonstrate substantial performance improvements.

Application of Reinforcement Learning on Medium Access Control for Wireless Sensor Networks

Yi Chu, Paul Mitchell, David Grace, Tim Clarke

Wireless Sensor Network (WSN) is a self-organised network which consists of a large number of randomly deployed nodes. It has a wide range of applications in industry, security, military, medical treatments and environmental research. Medium Access Control (MAC) protocols deal with how to schedule transmission and reception while sharing the same channel resource, and they have significant impact on energy efficiency and network life-time.

According to the energy constraints of WSNs, MAC protocols need to minimise energy cost associated with idle listening, overhearing and control packets while maintaining necessary throughput and delay performance. This project aims to develop energy-efficient MAC protocols with low complexity based on ALOHA and Reinforcement Learning.  Reinforcement Learning offers the potential for nodes to learn the most appropriate times to transmit on a shared channel, avoiding contention and resulting in almost perfect slot selection, thereby improving the energy efficiency.

The protocols are being simulated in OPNET alongside other protocols for comparison.

Key objectives for this project are:

  • To understand the special requirements of MAC protocols for WSNs.
  • To understand the advantages and disadvantages of ALOHA and other existing MAC protocols.
  • To apply Reinforcement Learning to Slotted ALOHA and compare with other protocols.

Low Power Medium Access Control Protocol Design for Wireless Sensor Networks

Kunyoung Lee, Paul Mitchell, David Grace

Wireless sensor networks are a novel form of communication network. For organization of these WSNs, each individual nodes are deployed randomly to a specific extent of areas based on application. These sensor nodes form a network automatically without outside intervention and send the information obtained by monitoring physical conditions to a server through an external formed network. This helps users collect necessary information easily by building extensive networks in even inaccessible areas. These WSNs are used in a variety of applications including home, industry, environment control and so on. Nowadays, the demand for these WSNs is increasing more and more.

The most important factor involving in WSNs is ultra low power consumption. In general, it is difficult and infeasible to replace each battery of nodes separately because the number of nodes is very large and also nodes are spread through remote and large regions. Therefore the aim of this research is focused upon an energy efficient medium access control (MAC) protocol for long life time of sensor nodes.

Our research focuses on the development of a low power and complexity MAC protocol based on the IEEE 802.15.4 wireless medium access control (MAC) and physical layer (PHY) specifications for low-rate wireless personal area networks (LR-WPANs). The existing MAC protocols still have problems of consuming a high power in communication algorithms, operation scheme and processing technique. Our research achieves the more energy efficient performance of MAC protocol in terms of removing unnecessary execution and optimizing transmission algorithm. For theoretical simulation, OPNET modeller is used and for practical experiment, IRIS Mote platform is used.

Key Objectives

  • To develop low power and complexity MAC protocol using optimized communication algorithm, adaptive operation scheme and refined processing technique.
  • To prove better performance through comparison of power consumption between existing MAC protocols and proposed MAC protocol

Energy-Efficient Medium Access Control for Wireless Sensor Networks Realised through Aerial Platforms

Jian Qiu, Paul Mitchell, David Grace

Wireless sensor networks (WSNs) represent a hot research topic which has developed rapidly nowadays. In future, WSN technology will improve the quality of human life significantly with its diverse applications. But energy efficiency is commonly accepted as the key design criterion for WSNs, given the limited power supply. The purpose of this project is to investigate how an aerial platform (AP) can be applied to improve the energy efficiency of medium access control (MAC) protocol for WSNs.

 This project mainly focuses on applying an aerial platform as a centralised coordinator to remove the burden of distributed scheduling, and inherently form the routes through the network. Using the radio link information which is uploaded by the sensor nodes, the AP can gather global topology information, and work out an optimal schedule for channel access and shortest path routes by using appropriate algorithms. To validate this, the feasibility of applying an AP will be examined through link budget calculations, and more accurate interference models will be designed. The benefits of better scheduling and routing will be determined by mathematical analysis. And then network simulations will be carried out to assess performance of the new protocols. A key output will be the end-to-end delay performance and energy consumption per packet, which can be compared with existing MAC protocols of WSNs.

 This work will integrate closely with other sensor network research activities within the Group.

Key Objectives

  • To understand the implications of using aerial platform for WSNs and check the feasibility of the link budget from sensor nodes to the platform.
  • To develop high energy-efficiency, low end-to-end delay, low system complexity schedule-based protocols for WSNs.
  • To develop performance models which illustrate the benefits on different topologies and traffic models of sensor network.


  • Design new schedule-based MAC protocols for WSNs realised through aerial platform for different network scenarios.
  • Simulations and analysis showing relative performance of the protocols.
  • Contributions to conference and journal papers.

Medium Access Control for Wireless Sensor Networks Realised Through Aerial Platforms

Hengguang Li, Paul Mitchell

Wireless Sensor Networks consist of a large number of wireless sensor nodes randomly deployed in an ad-hoc fashion in a test area; all the nodes then organise themselves to produce an efficient and effective sensor system.  WSNs can be used in many applications such as disaster prevention, environmental monitoring, and military projects. Because the test areas are often in remote or inaccessible locations, it is hard to recharge wireless sensor nodes with a fixed power supply, and to prolong the network's useful lifetime, battery capacity must be used as efficiently as possible. Medium Access Control (MAC) protocols are responsible for managing how nodes send out packets via a shared communication channel, and can have a major impact on system energy consumption.

The purpose of this project is to develop an energy-efficient MAC protocol that allows information to be transferred through a sensor network over a common radio channel directly to, or from, an aerial platform (a plane, balloon, or airship at high altitude).  With all communications over direct channels, there is no need to route packets through several nodes, reducing the overall routing burden on the sensor network.

A mixture of simulation and analysis is used. The MAC protocol designed in the project will be simulated in OPNET to get system performance results, which can be compared with existing MAC protocols.

Key objectives of this work are to:

  • To understand how the design of MAC protocols can affect the energy efficiency of a sensor network.
  • To simulate and characterise the main existing MAC protocols for wireless sensor networks.
  • To understand the application of aerial platforms and their characteristics to wireless sensor networks.
  • To combine MAC protocol design with aerial platforms.


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