Combat ICT systems are continually being improved. More efficient use of communications resources may lead to more effective military operations. In this paper, we look at a combination of technologies that enable distributed information exchange, and we have demonstrated this using a distributed command post scenario. We have built a software demonstration leveraging off-the-shelf hardware, showcasing how we can realize policy routing across a mixture of military and civilian carriers. Further, we have deployed adaptive user-facing services, that through cross-layer optimization can react and adapt to underlying network changes. Our demonstration has shown that we can sustain adaptable service quality across frequent network changes, even including a mixture of stationary and mobile command post nodes. This paper was originally presented in Skopje, North Macedonia, 16–17 May 2023.

Drone swarms have great potential to convey sensor information. However, a swarm may have a very high degree of topology dynamics. This impedes the sensor data distribution from the sensor node to consumers which are external to the swarm. A high sensor data rate requires reliable and efficient forwarding between the sensor and the consumer. This often makes unicast the preferred data forwarding method. But routing protocols struggle to achieve stable paths in high-mobile topologies. This makes unicast forwarding without suffering substantial packet loss very difficult. In this paper, we investigate how the swarm nodes can help to provide a stable path for the duration of a sensor data transfer. Stability is achieved by freezing the positions of the swarm nodes for the duration of the unicast flow. We investigate three different mechanisms to trigger this freeze, where two are based on the Ad-hoc On-demand Distance Vector (AODV) routing protocol. The results are very promising, with throughput for one flow remaining stable at almost 100% with 20 m/s swarm mobility, compared to the baseline results of 82% throughput. The results also indicate that even swarms without reactive routing may benefit from the freeze method to provide stable unicast paths as required.

Tactical edge networks represent a uniquely challenging environment from the communications perspective, due to their limited bandwidth and high node mobility. Several middleware communication solutions have been proposed to address those issues, adopting an evolutionary design approach that requires facing quite a few complications to provide applications with a suited network programming model while building on top of the TCP/IP stack. Information Centric Networking (ICN), instead, represents a revolutionary, clean slate approach that aims at replacing the entire TCP/IP stack with a new communication paradigm, better suited to cope with fluctuating channel conditions and network disruptions. This paper, stemmed from research conducted within NATO IST-161 RTG, investigates the effectiveness of Named Data Networking (NDN), the de facto standard implementation of ICN, in the context of tactical edge networks and its potential for adoption. We evaluated an NDN-based Blue Force Tracking (BFT) dissemination application within the Anglova scenario emulation environment, and found that NDN obtained better-than-expected results in terms of delivery ratio and latency, at the expense of a relatively high bandwidth consumption.

Unmanned Aerial Vehicles (UAVs) may become key to communication infrastructures, both in civilian crisis scenarios and in military use-cases. An earlier study has shown that the available capacity can be affected by the UAV's position and that the position for optimal network capacity may not be in the center between two ground nodes. In this paper, we investigate factors that impact the positioning of UAVs used to support ground-based communications. There are multiple trade-offs between the UAV's available information, the number of available UAVs and the resulting achieved throughput. We propose and evaluate strategies through ns-3 simulations. The results show that different positioning strategies are preferable in static versus mobile networks.

Mobile military networks are uniquely challenging to build and maintain, because of their wireless nature and the unfriendliness of the environment, resulting in unreliable and capacity limited performance. Currently, most tactical networks implement TCP/IP, which was designed for fairly stable, infrastructure-based environments, and requires sophisticated and often application-specific extensions to address the challenges of the communication scenario. Information Centric Networking (ICN) is a clean slate networking approach that does not depend on stable connections to retrieve information and naturally provides support for node mobility and delay/disruption tolerant communications - as a result it is particularly interesting for tactical applications. However, despite ICN seems to offer some structural benefits for tactical environments over TCP/IP, a number of challenges including naming, security, performance tuning, etc., still need to be addressed for practical adoption. This document, prepared within NATO IST-161 RTG, evaluates the effectiveness of Named Data Networking (NDN), the de facto standard implementation of ICN, in the context of tactical edge networks and its potential for adoption.

NATO has identified the WS-Notification standard from OASIS to support event-driven communication in the NATO enterprise and when building coalition networks. Using this standard promotes interoperability. However, there is significant overhead associated with WS-Notification since it is built on SOAP Web services (WS). Overhead can be problematic in networks with scarce resources. In this paper we perform a small-scale comparative evaluation of overhead of WS-Notification with another publish/subscribe standard: Message Queuing Telemetry Transport (MQTT). We also measure how these standards compare to the novel approach of content-based networking under the same networking conditions. We use the Named Data Networking (NDN) flavor of content-based networking for our experiment. Though fundamentally different, these approaches can be used to realize the Service-Oriented Architecture (SOA) paradigm. The drawback of standard publish/subscribe approaches is that they usually rely on a broker, which constitutes a single point of failure. NDN, on the other hand, has no broker which makes it interesting to consider for tactical networks. We use NATO Friendly Force Information (NFFI), which is much used for friendly force tracking, as the data format for the payload in all our tests. In the paper we focus on the respective approaches' network resource consumption. Based on the results we argue that the content-based approach seems promising and should be investigated further.

Technological advances on Unmanned Aerial Vehicles (UAVs) and autonomous control could make UAVs useful for communication purposes, extending the range and increasing the performance of Mobile Ad-Hoc Networks (MANETs). However, how and whether the UAV should be deployed in an otherwise terrestrial MANET depends on multiple parameters and objectives. In this paper, we analyze the effect of a UAV as a traffic relay compared to terrestrial-bound forwarding in a connected CSMA/CA MANET with omnidirectional antennas. A UAV is superior to terrestrial nodes in terms of connectivity, due to the larger Line-of-Sight coverage. This also means that a UAV can reduce the average number of hops in a MANET, thus reducing the self-interference problem and improve the network resource use. However, there are also negative effects of a UAV. The potential for spatial reuse is reduced, and problems due to hidden nodes increase. The results show that the UAV's impact on throughput and fairness depends on the traffic patterns, the topology, and the traffic load.

We discuss efficient methods for delivering traffic to a group of receivers that is expected to be in close proximity of each other. The methods are based on techniques for efficient flooding of the whole network. If the network covers a large military unit such as a battalion and the data is meant for one company, it is not resource efficient to flood the data to the whole battalion. Therefore, in this article we discuss improvements to Simplified Multicast Forwarding (SMF) that can limit SMF's flooding of a packet to a smaller segment of the network. We also propose a method where the new SMF techniques are used in conjunction with connectionless multicast (Xcast) to improve the flexibility and robustness of the forwarding method.

In emergency and crisis operations, group communication is essential to coordinate rescue efforts. Mobile Ad Hoc Networks (MANETs) can provide dynamic and resilient communication services in areas without a working communication infrastructure. The connectivity of MANETs can be improved using an elevated network node due to larger ground coverage, thus improving node reachability. Simplified Multicast Forwarding (SMF) is a scheme to efficiently distribute group communication packets in MANETs. In this paper, we explore methods to utilize SMF in a MANET supported by an elevated network node. We show that an elevated network node can improve the packet delivery ratio in a MANET with SMF-distribution of multicast packets. Further gains are made by unicasting the packets from the source to the elevated network node, moving the initial point of the SMF-distribution to the elevated network node. The consequences of a potential unicast packet loss are lessened by the source retransmitting the packet as multicast if it fails to receive the SMF-forwarded packet from the elevated network node. We achieve a high packet delivery ratio while maintaining a low cost for most topology sizes. Finally, the paper outlines future research directions for group communication in MANETs.

The performance of ad hoc networks depends greatly on the network topology. Thus, deploying relays or controlling the position of network nodes may impact the performance. Unmanned Aerial Vehicles (UAVs) and other elevated platforms may improve the ground network performance when used as network relays, due to better Line-of-Sight (LoS) conditions. In addition, UAVs can easily move to better locations. This paper shows that positioning a UAV asymmetrically between two ground nodes could result in better communication services than a UAV placed at the center position between the ground nodes, given the use of stepwise adaptive modulation. The IEEE 802.11 WLAN standard, a popular Mobile Ad Hoc Network (MANET) protocol with multi-rate capabilities, is employed for quantification of the effect. Simulations results show that the network performance can be lower with a UAV at the center between two (clusters of) ground nodes for certain geometries. For networks actively supported by UAV relays, this effect must be taken into consideration when choosing the location and when estimating the available capacity, e.g., for routing or call admission.

The ability to locate a hidden Radio Frequency (RF) transmitter is important in military operations. Moreover, the ability to detect and geolocate transmitters in noisy environments can be very challenging. Since the transmitters are unknown, no assumptions about their radiated effect and frequency can be made, i.e. a hidden transmitter. Efficient collection of data, with minimal human intervention and supervision is particularly important. These scenarios require mobile platforms to enable operations over larger areas with quick response times. Unmanned Aerial Vehicles (UAVs) are an ideal platform for RF sensors. Since the platform is elevated, lineof-sight is achieved, increasing the system performance. To locate a hidden transmitter quickly and effectively several agents need to cooperate. Swarm Intelligence (SI) is a term used to describe biologically inspired methods enabling groups of agents to cooperate. SI agents are focused on the global best, but act according to local rules using local communication. This makes the desired goal state an emergent property of the system, making it fault-tolerant, scalable and less reliant on centralized coordination. This paper presents simulation results that indicate that the geolocation task can be performed with as little as 3 agents. In addition we present both upper and lower bounds for Power Difference of Arrival geolocation, which can be used when studying Swarm Intelligence methods for geolocation. 1.0 INTRODUCTION The motivation for this work is to lay the ground work for using UAVs to autonomously geolocate, i.e. find the geographical location of, a hidden RF transmitter. In this context a hidden transmitter is a transmitter where the frequency, position and transmitting power is unknown. Such transmitters are abundant in the real world, where different devices contains several transmitters working with different frequencies and transmitting at varying intensities, even changing intensities based on power saving concerns. In a military context most modern radio systems have the ability to quickly change frequency to avoid interference or hostile jamming and can therefore be considered hidden transmitters. Geolocating hidden transmitters can be used in many military contexts. Examples such as detecting and locating hidden soldiers and intrusion detection around static and dynamic encampments are some of many possible scenarios where using RF geolocation is relevant. However, for such a system to work it needs to be operated autonomously with little to no human intervention. The system needs to be robust against unexpected failure and should be able to scale to different operating requirements. Unmanned Vehicles (UVs) and especially UAVs have become much more affordable in recent years. Their performance and robustness have also improved to a point where large numbers of UAVs can be deployed in the same environment with little effort. With the speed and maneuverability of modern UAVs, rapidly deploying and searching a large area is now a possibility. UAVs are therefore an ideal platform to utilize. STO-MP-SET-222 6 1 PUBLIC RELEASE PUBLIC RELEASE Locating a Hidden Transmitter Using Swarm UAVs Amplitude measurements are a simple way to gather information about RF signals. These measurements are easy to collect because of the inexpensive hardware required, in the form of a Received Signal Strength (RSS) indicator. In recent years these sensors have become small and inexpensive enough that almost any UV can be expected to have one. Power Difference of Arrival (PDOA) is based on comparing different amplitude measurements from three or more locations in order to estimate the position of a RF transmitter [16]. By using this technique combined with simple RSS measurements new low-cost UAVs can be used to locate RF transmitters. Coordinating several autonomous agents can be quite the challenge. A key challenge is how the individual agents should behave when taking into consideration that they are a small part of a larger system. SI and the more specialized field of Swarm Robotics (SR) uses simple agents and emergent behavior to design large scale distributed systems. SI takes inspiration from natural systems [4, 28] and utilizes local communication to achieve swarm level emergent behavior. The promise of SI is the simple agent design, scalability and fault tolerance. Simple agent design require less sophisticated UVs which can be a way to reduce cost. Greater scalability means that the system as a whole can handle different scenarios and is flexible to different operational requirements. Because the system is scalable it must also be fault tolerant, which means that when faults occur the systems ability to maintain the current task is not diminished. In other words, the system should not stop functioning simply because a smaller part has failed. These properties makes SI and SR capable of handling many different tasks [2, 5, 7, 11, 13, 35]. This paper presents the background and simulation study conducted in preparation for real-world experiments. We will first describe the background theory of RF detection, geolocalization, and SR. Then we will describe the simulation study carried out to test behavioral strategies for the UAVs. Results of the simulation study accompanied by a discussion follows before the conclusion is presented. 2.0 BACKGROUND In this section we will first discuss the challenges surrounding RF signal propagation, detection and localization. Then different techniques for geolocation will be discussed along with requirements for these techniques. We will then conclude this section with background information about SI and SR. 2.1 Signal Propagation RF signals are electromagnetic waves with a frequency between 3kHz and 300GHz [29]. When RF signals propagate they incur losses. With no external influences the signal is degraded by the free space path loss [29] which occurs because the wave propagates as an expanding sphere, where the power density decreases while the surface area expands.

Path capacity estimation is used for e.g admission control decisions and rate adaptation. This has resulted in a variety of proposed techniques, mostly for the wired domain. In this paper, we evaluate the accuracy of one packet-pair estimator in a wireless test-bed. We study the performance of the estimator when it is configured to be low-intrusive and also gain experience with its use on different radio transmission technologies and in the presence of traffic-shapers and IP packet fragmentation. The results show that the estimator can give valuable information to an admission control element. However, in a wireless network operating on a contention based shared channel, the packet-pair technique is vulnerable to the scheduling order of the probe packets on multi-hop paths. We also conclude as expected that the estimator can not be used uncritically on all types of transmission technologies.

Mobile networks in the military tactical domain, include a range of radio networks with very diverse characteristics and which may be employed differently from operation to operation. When interconnecting networks with dissimilar characteristics (e.g. capacity, range, mobility) a difficult trade-off is to fully utilize the diverse network characteristics while minimizing the cost. To support the ever increasing requirements for future operations it is necessary to provide tools to quickly alter the rule-set during an ongoing operation, due to a change in operation and/or to support different needs. Our contribution is a routing protocol which targets these challenges. We propose an architecture to connect networks with different characteristics. One key point is that low capacity links/networks segments can be included in the heterogeneous network, these segments are protected from overload by controlling where and when signaling/data traffic is sent. The protocol supports traffic policing, including resource reservation. The other key point is the ability to quickly alter the network policy (rules-set) including QoS support during an operation or from operation to operation.

In this article, we examine some major challenges to be solved in order to provide efficient end-to-end connectivity, resource management and QoS in a tactical military heterogeneous network (including the mobile edge). We briefly describe a selected set of possible solutions and mechanisms to improve inter-domain and intra-domain networking for the tactical heterogeneous network that will be further studied in the NATO STO IST-124/RTG-061 group "Heterogeneous tactical networks - improving connectivity and network efficiency".

In this paper we propose a Quality of Service (QoS) connectionless multicast protocol called QMCOM (QoS Multipoint relay Connectionless Multicast) providing QoS for realtime applications in Mobile Ad Hoc Networks. The QMCOM protocol scales with both group size and number of multicast groups. QMCOM builds on the multicast protocol MCOM by the addition of admission control and preemption. The admission control in QMCOM is a probe-based admission control scheme that is able to keep QoS demands of flows in multi-class systems. The preemption mechanism based on Backward Explicit Congestion Notification is able to reduce the QoS degradation of realtime flows. We evaluated the performance of QMCOM protocol in both testbed and simulation. The results show that QMCOM is a good candidate for an efficient QoS multicast protocol in Mobile Ad Hoc Networks.

Connectionless multicast protocols are well suited for networks with a large number of small multicast groups. These protocols however do not scale with large groups, and are not robust for high mobility. We proposed a connectionless multicast protocol named MCOM that addresses the issues of mobility, scalability, and robustness. The MCOM protocol design allows for better scalability by group size and has better protection for packet delivery under high mobility. The MCOM protocol is also able to adapt to the density of multicast group members. MCOM was implemented in Click Modular Router and evaluated in a testbed consisting of eight computers. The results indicate that MCOM is suited for dynamic MANETs in terms of mobility and the density of multicast group members.

Tactical ad-hoc networks are evolving today towards complex heterogeneous networks in terms of architecture, protocols and security. Due to the difference in network resources and reliability, end-to-end quality of service provisioning becomes very challenging. If we also take into account communication issues such as unpredictable connectivity, preferential forwarding for special traffic classes, intermittency due to node or communication link failure, the problem is further aggravated.In this article, we examine the major challenges that must be solved in order to provide efficient QoS provisioning in the heterogeneous network. Finally we describe QoS-aware mechanisms for inter-domain and intra-domain heterogeneous networks, also including real-time services provision in highly mobile environments.

Routing loops accounts for a fair share of packet loss in mobile networks, particularly so for heterogeneous mobile networks. Loops occur when nodes build routes based on inconsistent topology databases. The inconsistency is caused by, but not limited to, dissimilar transmission delay, lost signaling messages, mobility, traffic load, and dissimilar frequency for route update messages. The latter cause is a consequence of optimization of control traffic overhead in heterogeneous networks. These networks are networks that consist of links, or network segments, based on radios with unlike transmission technologies. Such networks typically operate in areas that enforce network topologies with non-optimal radio degree for some of the network types. This paper studies the phenomenon of routing loops in mobile heterogeneous networks. It is shown where the loops occur. Methods to reduce the occurrence of the loops, and ways to do local repair, are proposed.

Energy consumption determines the lifetime of Wireless Sensor Networks, WSN. In current radio chip sets the energy consumption for receiving a packet is of the same order as transmitting a packet. In such a setting, the transmission range and sleep strategies should be reevaluated. We present a simple extension to the MAC protocol that reduce the waste of energy for processing packets not addressed to a node by letting them sleep during transmission. The nodes enter sleep mode by means of a Transmission Announcement packet, TAN, sent by the transmitter. The performance is evaluated through simulation. Based on a simplified model, we show that the optimal transmission range in such a setting is given by the minimum needed to avoid partitioning. We use data sheet values from three different WSN Transceiver modules to derive parameter values to be used in the model. The model and related analysis concentrates on the energy consumption in transmitting and receiving, since the radio is the main contributor to energy consumption in WSN. We show that it is the energy consumption in receiving that is the main contributor to total energy consumption in WSN. Keywords-WSN; Energy Consumption; Sleep control; Optimal transmission range