Ilker Bekmezci

Flying Ad-Hoc Networks (FANETs)

One of the most important design problems for multi-UAV (Unmanned Air Vehicle) systems is the communication which is crucial for cooperation and collaboration between the UAVs. If all UAVs are directly connected to an infrastructure, such as a ground base or a satellite, the communication between UAVs can be realized through the in-frastructure. However, this infrastructure based communication architecture restricts the capabilities of the multi-UAV systems. Ad-hoc networking between UAVs can solve the problems arising from a fully infrastructure based UAV networks. In this paper, Flying Ad-Hoc Networks (FANETs) are surveyed which is an ad hoc network connecting the UAVs. The differences between FANETs, MANETs (Mobile Ad-hoc Networks) and VANETs (Vehicle Ad-Hoc Networks) are clarified first, and then the main FANET design challenges are introduced. Along with the existing FANET protocols, open research issues are also discussed.

Survey Flying Ad-Hoc Networks (FANETs): A survey

One of the most important design problems for multi-UAV (Unmanned Air Vehicle) systems is the communication which is crucial for cooperation and collaboration between the UAVs. If all UAVs are directly connected to an infrastructure, such as a ground base or a satellite, the communication between UAVs can be realized through the in-frastructure. However, this infrastructure based communication architecture restricts the capabilities of the multi-UAV systems. Ad-hoc networking between UAVs can solve the problems arising from a fully infrastructure based UAV networks. In this paper, Flying Ad-Hoc Networks (FANETs) are surveyed which is an ad hoc network connecting the UAVs. The differences between FANETs, MANETs (Mobile Ad-hoc Networks) and VANETs (Vehicle Ad-Hoc Networks) are clarified first, and then the main FANET design challenges are introduced. Along with the existing FANET protocols, open research issues are also discussed.

On the performance of Flying Ad Hoc Networks (FANETs) utilizing near space high altitude platforms (HAPs)

High altitude platforms (HAPs) and Flying Ad Hoc Networks (FANETs) are some of the most promising technologies for both military and civilian near space wireless networks. HAP systems usually reside on stratospheric altitudes up to 25 km and have the advantages of flexible deployment, wide area coverage and line-of-sight propagation, compared to ground or satellite based systems. Also Unmanned Air Vehicles (UAVs) have the ability for persistent flight over periods of days to weeks which cannot be achieved by manned aircrafts. Thus, utilization of FANETs in conjunction with HAP stations would present numerous advantages over traditional networking. However one of the most challenging issue for FANETs is the awareness of the locations of the neighboring UAVs. It is vital for FANET scenarios in the sense of reliability, security and collision avoidance. In this study we investigate how HAP&FANET architectures can be usefully employed in such scenarios. We propose a Medium Access Control (MAC) protocol which we name as Location Oriented Directional MAC (LODMAC) protocol. LODMAC successfully handles the neighbor discovery and data transmission in parallel with the help of directional antennas. Also we present the capacity gain of LODMAC protocol which verify that it is a good alternative for HAP&FANET based scenarios.

LODMAC: Location Oriented Directional MAC protocol for FANETs

Abstract Flying Ad Hoc Network (FANET) is a novel mobile ad hoc network type where the communicating nodes are Unmanned Aerial Vehicles (UAVs). FANETs promise many new ways for both civilian and military applications. Today, traditional omnidirectional antennas are deployed on UAV nodes which result in reduced spatial reuse and limited network capacity. Alternatively, deployment of directional antennas can significantly increase the capacity, spatial reuse and communication range of FANETs. In addition, being aware of the exact locations of the neighboring nodes in a FANET is vital especially for directional ad hoc multi-UAV scenarios. In this paper, we present a novel MAC protocol, LODMAC (Location Oriented Directional MAC), which incorporates the utilization of directional antennas and location estimation of the neighboring nodes within the MAC layer. By defining a new Busy to Send (BTS) packet along with the Request to Send (RTS) and Clear to Send (CTS) packets, LODMAC effectively addresses the well known directional deafness problem. In terms of throughput, utilization, average network delay and fairness, LODMAC protocol outperforms the well-known DMAC (Directional MAC) protocol which puts LODMAC to be a robust mile-stone for the on-coming FANET MAC protocols.

Weighted relay node placement for wireless sensor network connectivity

In wireless sensor networks (WSN), which are composed of unreliable sensor nodes, preserving the connectivity is a serious problem and one of the most effective solutions of this problem is to deploy powerful relay nodes (RN). The location of the RN is an important parameter for the network performance. In this paper, we investigate relay node placement (RNP) problem on a weighted terrain structure to satisfy WSN connectivity. Contrary to the existing studies, instead of minimizing the number of RN, the main objective of weighted RNP is to minimize the total weight of the points on which RN are deployed. In order to solve the weighted RNP problem, a mathematical formulation is proposed to find the optimal solution. However, because of the NP-complete nature of the problem, a polynomial time heuristic algorithm is also developed. Performance results show that the proposed heuristic algorithm can find near-optimal solutions in a reasonable time bound.

Connected multi UAV task planning for Flying Ad Hoc Networks

Flying Ad Hoc Networks (FANETs) is one of the most effective multi communication architectures through its capability of transferring data simultaneously without any infrastructure. The FANET task allocation problem is one-to-one assignment of agents to tasks so that the overall benefit of all the agents is maximized by taking delays and costs into account, given a set of agents and a set of tasks. A coordination based task allocation system ensuring spatial and temporal coordination between UAVs is essential for FANETs. In this paper, a new multi UAV task planning heuristic is proposed for FANETs to visit all target points in a minimum time, while preserving all time network connectivity. Effectiveness in the mission execution and cost efficiency in the task allocation have been presented by conducting a bunch of experiments performed on 2D terrains. Performance results validated the usage of our algorithms for the connected multi UAV task planning problem for FANET.

A new three-dimensional wireless multimedia sensor network simulation environment for connected coverage problems

A wireless multimedia sensor network (WMSN) is a network of wirelessly interconnected sensors that can gather multimedia information, such as sound and vision. One of the most important design issues of a WMSN is to maximize the coverage, while preserving the network connectivity. Although there are many studies about coverage for WMSNs, most of them are based on two-dimensional terrain assumptions. However, particularly for outdoor applications, three-dimensional (3-D) terrain structure affects the performance of the WMSN remarkably. In this paper, a novel 3-D WMSN simulation environment for connected coverage issues is presented. There are four main modules of our simulation environment. The terrain generator (TerGen) generates a synthetic 3-D landscape with different weather conditions (snow, rain, and fog), object occlusions (artificial or natural objects), and toughness levels of terrain (smooth or rough). The scenario editor (SenEd) is used to define various sensor types that have various behavioral and locational attributes. The outputs of TerGen and SenEd are the inputs of the simulator engine (SimEn), which simulates the WMSN and gives the performance results. The Optimization Module (OptMod), which is optional, can be used to determine the location of the sensors optimally, while satisfying a set of predefined constraints. Different scenarios are simulated to show the capabilities of the simulation environment. The performance results show that the 3-D terrain structure affects the coverage performance of the WMSN directly. The object occlusions and weather conditions are also very important for WMSN coverage.

Flying ad hoc networks (FANET) test bed implementation

One of the most important design problems for the multi unmanned aerial vehicles systems is communication between UAVs. In a multi-UAV system, the communication between UAVs is provided with all UAVs connecting directly to the ground station via satellite or infrastructure. However, infrastructure or satellite-based communication architectures restrict the capabilities of the multi-UAV systems. Infrastructure or satellite-based communication problems of multi-UAV systems can be solved with ad hoc networks among UAVs. This special ad hoc network structure is called as FANET. In this paper, a FANET test bed implementation study is presented.

Delay Sensitive, Energy Efficient and Fault Tolerant Distributed Slot Assignment Algorithm for Wireless Sensor Networks Under Convergecast Data Traffic

The scarcest resource for most of the wireless sensor networks (WSNs) is energy and the major factor in energy consumption for WSNs is communication. Not only transmission, but also reception is the source of energy consumption. The lore to decrease energy consumption is to turn off the radio circuit when it is not needed. This is why TDMA is advantageous over contention based methods. A time slot assignment algorithm is an essential part of TDMA based systems. Although centralized time slot assignment protocols are preferred in many WSNs, a centralized approach is not scalable. In this article, a new energy efficient, delay sensitive, and fault tolerant distributed time slot assignment algorithm, referred to as ft_DTSM, is proposed for sensor networks under convergecast traffic pattern. ft_DTSM aims at operating with low delay and low energy under faulty nodes assumption. Instead of random access based periods, it assigns slots with the help of tiny request slots. While traditional slot assignment algorithms do not allow assigning the same slot within two hop neighbors, because of the hidden node problem, ft_DTSM can assign, if the assignment is suitable for convergecast traffic. Simulation results have shown that both delay and energy consumption performances of ft_DTSM is superior to existing distributed slot assignment protocols for WSNs. ft_DTSM can also distribute the slots so that the network can continue its operation against a single point of failure. Although ft_DTSM has a somewhat longer execution time, its scalability characteristic may provide application specific time durations.

Periodic Global Broadcast Time Synchronization (PGB-TS) for TDMA Based Sensor Networks

Wireless sensor networks become a new alternative for satellite systems to sense fine grained small size subjects. Time synchronization is an important aspect of distributed systems including wireless sensor networks (WSNs). Traditional time synchronization methods are mostly optimized for scalability and precision. We propose a Periodic Global Broadcast Time Synchronization (PGB-TS) mechanism for TDMA based WSNs to maximize energy efficiency. PGB-TS assumes that the sink can send periodic broadcast to all sensor nodes. Sensor nodes receive the global reference broadcast and synchronize themselves to the sink PGB-TS estimates clock drift with linear regression and accepts receive error. Energy consumption of radio circuit of a sensor network is modeled analytically. Simulation results show that PGB-TS consumes significantly less energy at the expense of somewhat lowered precision. Unfortunately, because of its lower precision, energy consumption of a sensor network with PGB-TS increases with the increased number of children. To avoid the dependency in the number of children, we also propose to employ a new Data Indication Slot Mechanism (DISM) into PGB-TS. Beneficially, DISM prevents redundant checks at the expense of possible overhearing situations. Analytical model for the proposed PGB-TS with DISM is supported by the simulation results.