Link Quality Assessment Research Articles

Link Characterization and Edge-Centric Predictive Modeling in an Ocean Network

One of the critical problems fishermen face in deep-sea fishing is the lack of low-cost communication mechanisms to the shore. The Offshore Communication Network (OCN) is a network of fishing vessels at sea whose goal is to provide wireless internet over the ocean. The impact of extreme weather conditions on wireless signals, the inability to deploy additional infrastructure, the movements induced by sea waves, the expanded mobility freedom at sea, and the misalignment of directional antenna links are all unique challenges that cause abrupt signal quality fluctuations in OCN. For this reason, it is necessary to integrate near real-time link quality assessment to improve the resilience of communication. This paper examines the characteristics of marine wireless links and the factors impacting communication using data collected through sea-trial experiments involving multiple fishing vessels. The paper proposes a Bayesian framework for forecasting signal strength by employing historical and real-time data. This hybrid learning integrates offline and online probabilistic learning methods to provide intelligence at edge devices. The evaluation of the learning scheme on real datasets and the comparison with baseline methods under different communication contexts show improved predictive accuracy in OCN links.

A Data-Driven Packet Routing Algorithm for an Unmanned Aerial Vehicle Swarm: A Multi-Agent Reinforcement Learning Approach

Routing decisions made by unmanned aerial vehicle (UAV) swarms are affected by complex and dynamically changing topologies. A centralized routing algorithm imposes the entire computational burden on one module, and the high data dimensionality renders computation burdensome. In this letter, we develop a multi-agent reinforcement learning-based routing algorithm for a UAV swarm. The UAVs are trained in a data-driven manner to make distributed routing decisions. Factors that include channel quality, UAV movement, UAV overhead, and the extent of neighbor variation are incorporated into link quality assessment. Long short-term memory is used to improve the Actor and Critic networks, and more information on temporal continuity is added to facilitate adaptation to the dynamically changing environment. Simulations show that the proposed routing algorithm reduces data transmission delay and enhances the transmission rate compared with traditional routing algorithms.

METHODS AND TOOLS FOR ASSESSING THE LEVEL OF NOISE IMMUNITY OF WIRELESS COMMUNICATION CHANNELS

The subject of this article is the process of increasing the noise immunityof wireless channels in the construction or operation of modern digital communication systems (DCS), when the transmission of digital information significantly complicates the presence of interference and distortion in the communication channel. The aim is analysis and development of methods for ensuring stable and reliable operation of ultra-wideband wireless communication system in the conditions of interference and distortion of information in wireless communication channels. The task is creation and implementation of practical recommendations for improving the level of secrecy and quality of information circulating in the communication channel; development of criteria for quality, information efficiency and noise immunityof DCS wireless communication channels in the conditions of interference of natural and artificial origin. The methods used: methods of analytical modeling and the theory of potential noise immunity. The following results were obtained. The feasibility of assessing the DCS efficiency by two indicators - energy and frequency efficiency, which are the components that make up the overall integral indicator of informational efficiency was shown. It was proposed to evaluate the DCS efficiency by comparing the indicators of informational efficiency of the inverse and reference systems, using the Shannon limit as an ideal ratio of energy and frequency efficiency. On the basis of the theory of potential noise immunity it was shown that it is possible to operate wireless communication channels in conditions when the level of information signal and noise have the same value. Conclusions. It is shown that the use of the technology of supersmooth signals allows to carry out wireless redundant transmission of information with low impromptu capacity. Moreover, the efficiency of digital communication systems significantly increases due to the creation of an ensemble of complex signals through one-time encoding and modulation, which expands its information base, ensuring coverage and energy efficiency in a double symmetric channel. This enables the fullest possible utilization of the channel's Shannon capacity with high integrity of information transfer without a significant increase in the signal-to-noise ratio at the receiver's input. An integral indicator of informational efficiency of the wireless DCS communication channel is provided. It enables real-time integral assessment of link quality and optimal routing in a mobile peer-to-peer network – MANET.

Spectrum Detection and Link Quality Assessment for Heterogeneous Shared Access Networks

The persistent awareness of dynamic links quality is of critical importance to shared access systems, e.g., promoting sensing accuracy or even enabling seamless sharing, which remains yet as a challenging task. In this paper, we consider the shared access in heterogeneous small-cells, which are likely to be the main infrastructure components by utilizing the carrier aggregation (CA) scheme, potentially combining both licensed and unlicensed bands. We suggest a promising sensing scheme, which permits the simultaneous assessment of multiple links quality when detecting vacant spectrum, and hence is able to solve the long-standing hidden terminal problem. We incorporate an additional objective of acquiring dynamic link state information of multiple incumbent transmitters/receivers, and thereby, structure spectrum sensing as a mixed classification and estimation problem. The main challenge is that multiple channels may become similar with each other, and existing joint estimation schemes are unable to distinguish which incumbent is active and what its associated channel state is. To address this indistinguishable problem and alleviate the error propagation in recursive estimations, a novel alternating Bernoulli filtering algorithm is proposed. By fully exploiting the group transitional behavior of incumbents, a multiple-chains inference framework is developed. Numerical simulations validate our new scheme. Occupancy states of multiple incumbents can be identified accurately, by tracking their links quality and exploiting the underlying dynamics, which lays the foundation for more effective shared access.

A Clustering-Based Fast and Stable Routing Protocol for Vehicular Ad Hoc Networks

For the sake of improving network performances, i.e. end-to-end delay and packet drop ratio (PDR), in vehicular ad hoc networks (VANET), we propose a clustering-based fast and stable routing (CFSR) protocol. The CFSR protocol introduces a link quality assessment mechanism that evaluates the link quality on road segments between intersections and adopts the end-to-end delay as an evaluation metrics to assign a weight to the link corresponding to each road segment. The delay-sensitive application can directly use this weight as the link quality indicator to directly establish the routing path in the sub-zone by using Dijkstra algorithm. At the same time, the concept of local coordinator (LC) is introduced into the routing protocol to help construct the routing path conveniently and quickly. In addition, it can also avoid the local optimum problem caused by single-step decision and reduce the network transmission delay. In this paper, the Simulation of Urban Mobility (SUMO) and Network Simulation 3 (NS3) are used to simulate this protocol. Simulation results reveal that CFSR protocol can obtain lower end-to-end delay and PDR than those of the AODV and DSDV protocols.

Link Quality Assessment Algorithm for Heterogeneous Self-organizing Maritime Communications Network

The article introduces a method of performing a radio link quality assessment based on the Link Quality Indicator (LQI) which will be calculated for every system that is available. The method presented has been developed during the netBaltic project completed in Poland and generally applies to the so-called maritime zone A, i.e. the sea area where ships are still within the range of shore-based radio communication systems, particularly 3G/LTE cellular networks. The algorithm was developed based on the results of measurements obtained during two separate campaigns. That measurement data served as a basis for the method’s initial assumptions and was utilized during the method’s verification.

MEQSA-OLSRv2: A Multicriteria-Based Hybrid Multipath Protocol for Energy-Efficient and QoS-Aware Data Routing in MANET-WSN Convergence Scenarios of IoT

Convergence of typical wireless networks [mobile ad hoc network (MANET) and wireless sensor network (WSN)] is paving the way toward brand-new cooperative platforms for Internet of Things (IoT) communications. The IoT enables the global connectivity of a wide variety of heterogeneous objects in accordance with their battery capacity, processing capabilities, and mobility to serve people in a collaborative manner automatically and intelligently. In such ubiquitous smart environments, efficient and effective data routing among IoT devices represent a real challenge due to nodes heterogeneity. Thus, this paper proposes a hybrid multipath energy and quality of service (QoS)-aware optimized link state routing protocol version 2 (MEQSA-OLSRv2), which is developed to cope with the challenges presented by limited energy resources, mobility of nodes, and traffic congestion during data transmission in the MANET-WSN convergence scenarios of IoT networks. This protocol uses a node rank according to multicriteria node rank metric (MCNR). This MCNR aggregates multiple parameters related to energy and QoS into a comprehensive metric to dramatically reduce the complexity of multiple constrained considerations and avoid the control overhead caused by separately broadcasting multiple parameters. These metrics are the node’s lifetime, residual battery energy, node’s idle time, node’s speed, and queue length. The MCNR metric is utilized by a new link quality assessment function for multiple-route computation. It is also adopted to select a multipoint relay (MPR) set of nodes by using an energy and QoS-aware MPR selection mechanism for flooding topological information. The simultaneous consideration of energy and QoS parameters can benefit the tradeoff between QoS and energy awareness. The performance of the MEQSA-OLSRv2 is evaluated through EXata-based simulations, and its effectiveness is validated by comparing it with the conventional routing protocols. The MEQSA-OLSRv2 is found to outperform existing schemes even in heavy traffic load and high-mobility scenarios. Furthermore, the MEQSA-OLSRv2 considerably enhances QoS, reduces energy consumption, and decreases the energy cost per packet.

A Tutorial on Fiber Monitoring for Applications in Analogue Mobile Fronthaul

Radio access networks must evolve to meet future communication requirements. One of the development directions is the future radio base station architecture and its functional splits. The very last connectivity segment to a simple antenna unit is analogue in nature and, to centralize the important and expensive radio access network resources, one would potentially want to extend it to several kilometers. This sort of requirement calls for development of new fiber-based transport technologies with strong emphasis on reach improvement, bandwidth efficiency, and link reliability. With regards to the later aspect, efficient monitoring of physical links would become essential. It should provide rapid and detailed in-service link quality assessment and troubleshooting while imposing minor additional costs and preserving signal integrity. While link monitoring possibilities in baseband transmission for backhaul or digital radio over fiber for fronthaul have been extensively studied, the analogue radio over fiber transmission brings opportunities for application of novel and potentially more efficient transceiver-embedded techniques. It is the objective of this paper to emphasize the critical importance of analogue radio over fiber link monitoring in the era of rapidly developing mobile communications. Our aim in this communication is to define requirements, which an efficient monitoring solution is expected to satisfy, and provide an overview of recent developments. It is assumed that the readers possess general knowledge of fiber optic transmission, reflectometry, passive optical networks and are familiar with various optical components. Set of selected references is provided for those willing to deepen their knowledge of aspects addressed in this paper.

Routing metric of interference-aware link quality: an improved ETX in wireless mesh networks

This article addresses the problem of route selection in wireless mesh networks (WMNs). The traditional routing metrics adopt packet delivery ratio (PDR) as a representative metric of wireless link quality assessment. However, PDR measured by the broadcast-based probe method is affected by the size, number and transmission rate of probe packets, which influences the metric accuracy. In this paper, improved expected transmission count (iETX), a new routing metric of interference-aware link quality, is proposed for WMNs. Dispensing with traditional broadcast-based probing method, the iETX uses regional physical interference model to obtain PDR. Regional physical interference model is built upon the relationship between signal to interference plus noise ratio (SINR) and PDR, which contributes to the improvement of metric accuracy. The iETX comprehensively considers the effects of interference and link quality and minimizes the expected number of packet transmissions required for successful delivery, which helps find a path with minimum interference and high throughput. Simulation shows that the proposed metric can significantly improve the network performance.

A Link Quality Prediction Metric for Location based Routing Protocols under Shadowing and Fading Effects in Vehicular Ad Hoc Networks

The location-based routing protocol has been chosen as one of the efficient routing approaches in vehicular ad hoc networks in terms of low overhead and high scalability. Its critical advantage lies in performing a pathless routing such that a node having a packet forwards it to its neighbor node that provides the shortest physical distance to destination and this process continues until the packet reaches destination. The problem lies in that the link stability of the neighbors varies largely depending on the mobility of vehicles and the environmental factors that incur shadowing and fading effects. In this paper, we propose a new link quality prediction metric associated with location based protocols to improve the selection of next hop, that consider both the link quality assessment based on the transmission success rate and the link quality assessment based on the prediction of the future locations of vehicles. Simulation results are presented to demonstrate the efficiency of the proposed metric.

Reliable multihop broadcast protocol with a low-overhead link quality assessment for ITS based on VANETs in highway scenarios.

Vehicular ad hoc networks (VANETs) have been identified as a key technology to enable intelligent transport systems (ITS), which are aimed to radically improve the safety, comfort, and greenness of the vehicles in the road. However, in order to fully exploit VANETs potential, several issues must be addressed. Because of the high dynamic of VANETs and the impairments in the wireless channel, one key issue arising when working with VANETs is the multihop dissemination of broadcast packets for safety and infotainment applications. In this paper a reliable low-overhead multihop broadcast (RLMB) protocol is proposed to address the well-known broadcast storm problem. The proposed RLMB takes advantage of the hello messages exchanged between the vehicles and it processes such information to intelligently select a relay set and reduce the redundant broadcast. Additionally, to reduce the hello messages rate dependency, RLMB uses a point-to-zone link evaluation approach. RLMB performance is compared with one of the leading multihop broadcast protocols existing to date. Performance metrics show that our RLMB solution outperforms the leading protocol in terms of important metrics such as packet dissemination ratio, overhead, and delay.

Maintaining Communication Links Using a Team of Mobile Robots

This paper presents a comprehensive metric to evaluate the link quality and the corresponding control schemes for the distributed control of a team of robots to maintain the communication links. The mobile robots dynamically reconfigure themselves to maintain reliable end-to-end communication links. Such applications require online measurements of communication quality in real time and require a mapping between link quality and robot positions. In this paper, we present the empirical results and analysis of a link variability study for an indoor and outdoor environments including received signal strength indicator (RSSI), throughput and packet loss rate. The distributed control algorithms consider the environmental constrains and obstacles. Moreover, the self-deployment algorithms allow a team of robots to recognize the coverage gap by monitoring link qualities, and deploy the mobile robots for a variety of applications including self-healing, tethering, intelligent relaying. The assessment of link quality acts as the feedback for cooperative control of mobile robots. The experimental results have shown the effectiveness of evaluation for communication links and the related control schemes.

Partner Selection in Indoor-to-Outdoor Cooperative Networks: An Experimental Study

In this paper, we develop a partner selection protocol for enhancing the network lifetime in cooperative wireless networks. The case-study is the cooperative relayed transmission from fixed indoor nodes to a common outdoor access point. A stochastic bivariate model for the spatial distribution of the fading parameters that govern the link performance, namely the Rician K-factor and the path-loss, is proposed and validated by means of real channel measurements. The partner selection protocol is based on the real-time estimation of a function of these fading parameters, i.e., the coding gain. To reduce the complexity of the link quality assessment, a Bayesian approach is proposed that uses the site-specific bivariate model as a-priori information for the coding gain estimation. This link quality estimator allows network lifetime gains almost as if all K-factor values were known. Furthermore, it suits IEEE 802.15.4 compliant networks as it efficiently exploits the information acquired from the receiver signal strength indicator. Extensive numerical results highlight the trade-off between complexity, robustness to model mismatches and network lifetime performance. We show for instance that infrequent updates of the site-specific model through K-factor estimation over a subset of links are sufficient to at least double the network lifetime with respect to existing algorithms based on path loss information only.

An Investigation of Link Quality Assessment for Mobile Multi-hop and Multi-rate Wireless Networks

Wireless ad hoc networks will be an important component in future communication systems. The performance of wireless ad hoc networks can be improved by link quality-aware applications. Wireless link quality is dynamic in nature, especially in mobile scenarios. Therefore, accurate and fast packet delivery ratio estimation is a prerequisite to good performance in mobile, multi-hop and multi-rate wireless ad hoc networks. In this paper, we propose a novel packet delivery ratio estimation method that improves the accuracy and responsiveness of the packet delivery ratio estimation. The proposed link quality estimation components are implemented in a IEEE 802.11b/g test-bed. The experiment results show that the accuracy of the packet delivery ratio estimation can improve up to 50% in mobile scenarios without introducing overhead. We also show the end-to-end performance impact of this improved estimation on route selection using different routing metrics and configurations. The measurement results show that our packet delivery ratio method leads to better route selection in the form of increased end-to-end throughput compared to traditional methods, which respond slowly to the link dynamics.

Channel Characterization and Link Quality Assessment of IEEE 802.15.4-Compliant Radio for Factory Environments

Wireless sensors have started being utilized for process monitoring in factory environments, which are typically harsh for low-power wireless communication due to their complicated layout and plentiful stationary/moving obstacles. Sensor radios available so far have been engineered for consumer-grade applications, featuring low cost, low power, and minimal radio complexity. In order to utilize such radios for factory applications, their channel characteristics and link quality must be investigated for optimal design and reliability assessment. In this paper, a series of measurements were made with IEEE 802.15.4-compliant sensor radios to study both their spatial and temporal characteristics with respect to the factory surroundings found in a university machine shop. Critical communication properties were investigated in terms of received signal strength, link quality indication, and packet error rate. It is found that received signal strength shows dependency on surrounding structures, radio link qualities with respect to received signal strength and link quality indication are stable before a grey zone is reached, and average link quality indicator serves as a better packet success rate indication than average received signal strength indication. The findings in this paper provide a useful guidance to the ongoing explorations for a methodology to predict radio performance at any location within a given factory floor plan and to online assess the time-variant link qualities.