Congestion Control (CC) has a significant influence on the performance of Transmission Control Protocol (TCP) connections. Over the last three decades, many researchers have extensively studied and proposed a multitude of enhancements to standard TCP CC. However, this topic still inspires both academic and industrial research communities due to the change in Internet application requirements and the evolution of Internet technologies. The standard TCP CC infers network congestion based on packet loss events which leads to long queuing delay when bottleneck buffer size is large. A promising solution to this problem is to use the delay signal (RTT or one-way delay measurements) to infer congestion earlier and react to the congestion before the queuing delay reaches a high value. In this survey paper, we describe the delay signal and the algorithms that completely or partially utilise this type of signal. Additionally, we illustrate standard CC and modern Active Queue Management (AQM) principles and discus the interaction between AQM and the delay signal.

Communication infrastructure is crucial during emergencies because it ensures reliable coordination and information dissemination for effective search and rescue missions. However, these systems rely on physical structures, making them vulnerable to failures caused by disasters like fires and flooding. To enhance resilience, redundant infrastructure is commonly practiced. For instance, redundant systems ensure continuous operation in space missions where repairs are not feasible. A major gap exists, however, as redundancy is not a viable solution for remote areas without existing communication infrastructure. Additionally, victims may need to evacuate to safety zones not covered by mainstream communication systems. In such cases, alternative infrastructure that is easy to deploy is required to address emergency communication challenges fully. This paper presents a framework to analyze the deployability of current satellite communication infrastructure for this purpose. The analysis focuses on deployability dynamics, elements, and applications. We start by discussing the evolution of satellite ground stations into mobile and software-defined systems. In the analysis, we find that, despite these advancements, current infrastructure fails to provide a single device that meets low power and low-cost rapid deployment requirements based on our deployability framework. The product that almost fulfils this is the satellite phone. However, satellite phones are prohibitively expensive for large-scale deployments, with a single device costing over 600 United States Dollars (USD), more than ten times the cost of Internet of Things (IoT) devices supporting similar technologies. Additionally, they are not power efficient. The high cost of satellite applications is associated with spectrum licensing and satellite infrastructural costs. We have analyzed satellite communication frequency bands and architectural design, such as antenna designs, communication protocols and standards, modulation techniques, and signal processing methods, to understand the important factors toward full deployability. Our comprehensive analysis reveals a gap in addressing interoperability issues caused by disparate communication standards, processing power and energy requirements. Further analysis reveals promising open-source initiatives that offer potential solutions, such as low-data rate modulation schemes, low-bitrate voice codecs, and low-power encryption techniques. Additionally, advancements in Artificial Intelligence(AI) and robust cybersecurity techniques provide a solid foundation for future developments of rapidly deployable satellite-based emergency communication infrastructure. Consequently, we have identified opportunities for developing low-power, frequency-agile architectures that integrate satellite and terrestrial network infrastructure. Specifically, the next-generation Cospas-Sarsat Search and Rescue system provides a pathway for eliminating spectrum licensing costs, making deployable systems affordable for mass adoption. Future work should leverage advancements in low-bitrate technologies to enhance emergency systems, ensuring secure and resilient two-way voice, messaging, and distress signalling capabilities for critical communications.

The Internet of Things (IoT) and blockchain are emerging technologies that have attracted attention in many industries, including healthcare, automotive, and supply chain. IoT networks and devices are typically low-powered and susceptible to cyber intrusions. However, blockchains hold considerable potential for securing low-power IoT networks. Blockchain networks provide security features such as encryption, decentralisation, time stamps, and ledger functions. The integration of blockchain and IoT technologies may address many of the security concerns. However, integrating blockchain with IoT raises several issues, including the security vulnerabilities and anomalies of blockchain-based IoT networks. In this paper, we report on our experiments using our blockchain test bed to demonstrate that blockchains on IoT platforms are vulnerable to DDoS attacks, which can also potentially lead to device hardware failures. We show that a number of anomalies are visible during either a DDoS attack or IoT device failure. In particular, the temperature of IoT hardware devices can exceed 90 °C during a DDoS attack, which could lead to hardware failure and potential fire hazards. We also found that the Block Transaction Rate (BTR) and network block loss percentage can increase due to corrupted hardware, with the BTR dropping to nearly zero blocks/sec and a block loss percentage of over 50 percent for all evaluated blockchains, and as high as 81.3 percent in one case. Our experiments demonstrate that anomalous temperature, latency, bandwidth, BTR, and network block loss percentage can potentially be used to identify DDoS attacks.

The performance of many networked applications improves when Round Trip Time (RTT) is reduced. With lower RTTs, human-to-human interactions become more realistic, query-response activities (such as DNS lookups) are more responsive, and transport protocols (such as TCP) can better utilise a path’s available capacity for long-lived file transfers. Additionally, RTT prediction systems are beneficial in distributed networks in order to improve performance and resource allocation. RTT prediction systems predict RTT for all nodes in the network without additional exchange of packets. We discuss thirteen RTT prediction systems under three classes: localisation measurement systems, network coordinate systems, and matrix factorisation systems. RTT prediction systems have been applied with positive results to various applications and services, such as Peer-to-Peer (P2P) networks (e.g. BitTorrent clients, content distribution networks and Internet of things) or Client-Server networks (e.g. game server discovery).

In this paper, we describe a LoRa (from “Long Range”)-based, linear sensor network we have developed for transmitting location information of personnel and equipment in an underground mine. The system is intended to be used during emergencies when existing communications infrastructure has failed. Linear networks comprise a sequence of relays that forward data to a common destination, the headend. Relays forward location information transmitted from tags carried by personnel or equipment. Relays will usually be put in place as investigators or rescuers enter the mine. LoRa is used both by the tags to communicate to the relays and by the relays to forward messages to the headend. We have implemented and tested this system, and have carried out simulations and analyses to determine its scalability, reliability and fairness. The need for robustness and reliability has led us to use flooding rather than unicast communication. We also use message sequence numbers and time-to-live fields to prevent broadcast storms. Contention is managed using a simplified Carrier Sense Multiple Access (CSMA) scheme. We also address fairness. When the network is under load messages may be dropped by relays making messages generated more hops from the headend more likely to be dropped than messages nearer the headend. We explore the relationship between unfairness, traffic load and number of relays. We also observe that a network of larger numbers of lightly loaded relays performs more effectively than smaller numbers of heavily loaded relays.

Underground mining increasingly relies on wireless communications for its operations. The move to automating many underground mining processes makes an understanding of the propagation characteristics of key wireless technologies underground a topic of considerable importance. LoRa has great potential for communications in underground mines, but data on its propagation are quite scarce. In this paper, we describe our measurements of LoRa radio propagation in an underground gold mine. We took measurements in an extraction tunnel with line of sight and in extraction and access tunnels without line of sight. We observed excellent propagation, both with and without line of sight. Our observations support claims by others that the steel-lined tunnels act as a waveguide. As well as reporting measurements, we also developed models of propagation. For line of sight, we show that pathloss is well modelled by a power law with pathloss index of 1.25 and that variability of signal strength is well modelled by a lognormal distribution. We also successfully modelled propagation without line of sight over short distances using a Fresnel Diffraction and Free Space model.