Recent research carried out by a group of engineers at Kumoh National Institute of Technology, South Korea focuses on the hybrid medium access control (MAC) protocol for wireless sensor network (WSN) data gathering while employing unmanned aerial vehicles (UAVs).
Studying the Hybrid MAC Protocol and All of its Actions
Obviously, the main aim of this research is to study the hybrid MAC protocol and all of its actions while sending information to the sensor nodes regarding its presence – and afterwards contending to send registration frame to the UAV.
As the abstract of their paper notes:
“The transmission schedule of each sensor is determined based on their priority. Specifically, the priority of each sensor is determined during the registration process. Furthermore, the architecture of UAV-WSN data gathering system is introduced in this paper. Simulations are performed, showing that the proposed MAC protocol achieves fairness while enhancing network performance.”
The Wide Range of Applications for WSNs
As an emerging technology, it is the wireless sensor networks (WSN) that are most applicable in this research as shown by the authors – and their wide range of applications. As they describe them:
“Generally, each 15 sensor in a WSN collects and processes data, routing it to a sink node or base station via other sensors . 16 WSNs employed in disaster-affected areas have different requirements from those of other applications, 17 because sensors deployed in a location distant from the sink node may lose communications. Thus, 18 mobile sink nodes are needed. Unmanned aerial vehicle (UAV) can be employed as mobile sink nodes for 19 various WSN applications. UAV can move easily and quickly to access real time-sensitive information in 20 disaster-affected areas needing mobility communications for emergency rescue purposes. For industrial 21 applications, UAV can be employed to gather sensor data in agricultural  and oil refinery zones , 22 where sensors are scattered around large areas far from control stations.”
Even though UAVs have found their greatest use in military applications since their development, there have been some disadvantages regarding their deployment – mostly seen through the maintenance costs. Currently, UAVs are less expensive and smaller which makes them more attractive to private sectors.
A fundamental limitation of the data gathering systems, according to authors, is the medium access control (MAC) protocol which deteriorates network performance and is unsuitable for UAV-WSN.
Developing a Working Network Model
As we mentioned earlier, the authors propose a hybrid MAC protocol for data gathering – as the result and the perfect example of an architecture that uses effective data gathering with a prioritization scheme, a different DIFS value as well as groupization of notes that are located in the same property area.
Most importantly, they create a UAV-WSN system that can be easily deployed for numerous data-gathering applications in both small and large areas.
“UAV-WSN systems 140 can improve nodes’ power consumption efficiency by dynamically deactivating unused nodes . 141 Furthermore, network performance may improve, owing to better line-of-sight (LoS) between the UAV 142 and nodes . Exponent path loss is small compared to sensor-to-sensor communications. Therefore, 143 the UAV-WSN causes data gathering process to be more efficient than that in common WSN system,” the authors state in the paper.
Conclusion: A Novel MAC Protocol Designed for UAV-WSN Data Gathering
After illustrating the hybrid MAC protocol, the time interval scheme, scheduling rules and the general overview of the MAC mechanism, the authors come to a conclusion which presents a novel MAC protocol designed for UAV-WSN data gathering that is named HP-MAC protocol.
As they put it:
“The HP-MAC protocol is a hybrid MAC protocol that based on the IEEE 802.11 CSMA/CA MAC 342 protocol and TDMA protocol. The superframe of HP-MAC protocol is divided to four periods which are 343 first beacon period to inform the presence of UAV, registration period that used for unregistered node to 344 send their REG frame to the UAV, second beacon period for UAV to broadcast the schedule information 345 for all registered nodes, and gathering period in which each registered node transmits the data according 346 to their time slot schedule.”
According to the authors, the architecture of the drone can tackle the limited communication range of ground control station to transmit the flight path data to the UAV – tested and evaluated as successful, showing its achieved fairness for data gathering in UAV-WSN systems.
Citation: Ramli, M.R.; Kim, D.; Lee, J.M. “Hybrid MAC Protocol for UAV-Assisted Wireless Sensor Networks” – Preprints 2018, 2018110501, https://www.preprints.org/manuscript/201811.0501/v1