Lossy Wireless Channels Research Articles

A Lightweight Sensor Scheduler Based on AoI Function for Remote State Estimation Over Lossy Wireless Channels

A Lightweight Sensor Scheduler Based on AoI Function for Remote State Estimation Over Lossy Wireless Channels

A Protocol for Reliable Real-Time Wireless Communication of Large Data Samples

In this paper, we present a middleware protocol, that transmits larger-than-a-frame data samples within application real-time and reliability requirements over a lossy wireless channel. The protocol efficiently deploys an intelligent retransmission control that exploits the extended deadline requirements of a sample for frame-level scheduling. The transmission of such samples is placed in the context of the necessary integration of such external sensor data into the decision-making process of an autonomous vehicle. Therefore, we provide parameterization and access rules for communication links in resource-managed scenarios and lay out how to integrate the protocol into the popular DDS middleware. The performance of the parameterized links to satisfy their reliability requirements is studied and compared to error protection protocols in the current software stack. We base the evaluation on an OMNeT++ simulation, whereby an established wireless error model is used. The use case is placed in the context of collaborative sensing in a valet parking environment, where external infrastructure sensor data augments the autonomous vehicle's data processing chain via a lossy wireless link. Thereby, the use case adheres to the underlying safety requirements. Results show that if the protocol's awareness of the application requirements is used for parameterization, guarantees for reliability can be provided that outperform existing solutions.

MIMO Terahertz Quantum Key Distribution Under Restricted Eavesdropping

Quantum key distribution (QKD) can provide unconditional security to next generation communication networks guaranteed by the laws of quantum physics. This paper studies the secret key rate (SKR) of a continuous variable quantum key distribution (CV-QKD) system using multiple-input multipleoutput (MIMO) transmission and operating at Terahertz (THz) frequencies. Distinct from previous works, we consider a practical “restricted" eavesdropping scenario in which Eve can collect only a fraction of photons lost in the environment. We propose a system model for the MIMO THz CV-QKD system that accounts for restricted eavesdropping via a lossy wireless channel between Alice and Eve. We derive for this system new SKR expressions for both coherent-state-based and squeezed-state-based CV-QKD protocols. Our results show that previous analysis assuming unrestricted eavesdropping leads to overly pessimistic SKRs, and that in practice, the achievable SKR can be significantly increased under restricted eavesdropping. The increase in the SKR is quantified by the simplified SKR expansions derived in this paper. Our results also reveal that squeezing is beneficial for improving the SKR only for unrestricted eavesdropping. However, in a practical setting with restricted eavesdropping, increased squeezing leads to a reduction in the SKR.

On the Packet Decoding Delay of Linear Network Coded Wireless Broadcast Sur le délai de décodage des paquets de la diffusion sans fil codée par réseau linéaire

We apply linear network coding (LNC) to broadcast a block of data packets from one sender to a set of receivers via lossy wireless channels, assuming that each receiver already possesses a subset of these packets (through previous systematic transmissions) and wants the rest. We aim to characterize the average packet decoding delay (APDD), which reflects how soon each data packet can be decoded by each receiver on average, and to minimize it without sacrificing throughput. To this end, we first derive closed-form lower bounds on the expected APDD of LNC techniques. We then prove that determining whether these lower bounds are tight is NP-hard and so is APDD minimization. We then prove that every throughput-optimal LNC technique can approximate the minimum expected APDD with a ratio between 4/3 and 2 and that this ratio is exactly 2 for random LNC (RLNC). We also show that instantly decodable network coding (IDNC) techniques cannot approximate APDD due to suboptimal throughput. Finally, we propose hypergraphic LNC (HLNC), a novel throughput-optimal and APDD-approximating technique based on a hypergraphic model of receivers. Our simulations show that the APDD of HLNC significantly outperforms existing techniques, including RLNC, under all considered settings without any sacrifice on throughput.

Employing Intelligent Aerial Data Aggregators for the Internet of Things: Challenges and Solutions

Internet-of-Things (IoT) devices equipped with temperature and humidity sensors and cameras are increasingly deployed to monitor remote and human-unfriendly areas (e.g., farmlands, forests, rural highways, and electricity infrastructures). Aerial data aggregators such as autonomous drones provide a promising solution for collecting sensory data of IoT devices in human-unfriendly environments, enhancing network scalability and connectivity. The flexibility of a drone and favorable line-of-sight connection between the drone and IoT devices can be exploited to improve data reception at the drone. This article first discusses challenges of the drone-assisted data aggregation in IoT networks, such as incomplete network knowledge at the drone, limited buffers of the IoT devices, and lossy wireless channels. Next, we investigate the feasibility of onboard deep-reinforcement-learning-based solutions to allow a drone to learn its cruise control and data collection schedule online. For deep reinforcement learning in a continuous operation domain, deep deterministic policy gradient (DDPG) is suitable to deliver effective joint cruise control and communication decision, using its outdated knowledge of the IoT devices and network states. A case study shows that the DDPG-based framework can take advantage of the continuous actions to substantially outperform existing non-learning-based alternatives.

Analytical model of IoT CoAP traffic

The Constrained Application Protocol (CoAP) is a mechanism that enables the efficient transmission of information in the context of Wireless Sensor Networks (WSNs) characteristic of the Internet of Things (IoT). CoAP is specifically intended to work well with low complexity sensors that have limited access to computational resources. And because it lacks the overhead of other more sophisticated transport protocols, it is suitable for high packet loss wireless networks. Relying on the User Datagram Protocol (UDP), CoAP introduces, among other things, confirmable and non-confirmable message types, depending on the nature of the source data. This paper presents a novel analytical model that can relate the application to network packet loss and be used to estimate the effect of lossy wireless channels in CoAP scenarios. Moreover, the model is ultimately validated by an experimental framework in which theoretical and experimental results are compared.

Recursive Bayesian Filtering-Based Error Concealment Scheme for 3D Video Communication Over Severely Lossy Wireless Channels

The three-dimensional video (3DV) is composed of variable-length stream sequences captured via diversified cameras surrounding an object. Thus, it is an urgent task to accomplish sufficient encoding to be compatible with incoming bandwidth demands, while achieving a recommended 3DV reception performance. In the 3DV compression framework, the lost macro-blocks (MBs) might propagate into the following frames and the adjoining views. Therefore, it is obligatory to avoid error propagation by concealing the corrupted MBs at the decoder through the utilization of appropriate post-processing error concealment (EC) techniques. The existing EC algorithms fundamentally exploit the temporal, inter-view, and spatial matching within the 3DV frames and views to reconstruct the disparity vectors (DVs) and motion vectors (MVs) of the corrupted MBs. Unluckily, in the state of high severe corruptions and heavily erroneous MBs, these concealment algorithms are predominantly unreliable and might give unreliable 3DV quality. Thence, in this work, we suggest the utilization of the outer block boundary matching algorithm to estimate the MVs and the directional interpolation EC algorithm to estimate the DVs of the erroneous MBs. After that, the Bayesian Kalman filter (BKF) is employed because of its efficiency to filter out the inherent errors in the previously predicted DVs and MVs to accomplish better 3D video performance. Experimental results on standard 3DV sequences demonstrate that the suggested BKF-based EC scheme is more powerful with heavy losses. It subjectively and objectively outperforms the traditional concealment techniques at severely random and bursty packet loss rates (PLRs).

Optimal Video Streaming in Dense 5G Networks With D2D Communications

Mobile video traffic and mobile devices have now outpaced other data traffic and fixed devices. Global service providers are attempting to propose new mobile infrastructures and solutions for high performance of video streaming services, i.e., high quality of experience (QoE) at high resource efficiency. Although device-to-device (D2D) communications have been an emerging technique that is anticipated to provide a massive number of mobile users with advanced services in 5G networks, the management of resource and co-channel interference between D2D pairs, i.e., helper-requester pairs, and cellular users (CUs) is challenging. In this paper, we design an optimal rate allocation and description distribution for high performance video streaming, particularly, achieving high QoE at high energy efficiency while limiting co-channel interference over D2D communications in 5G networks. To this end, we allocate optimal encoding rates to different layers of a video segment and then packetize the video segment into multiple descriptions with embedded forward error correction before transmission. Simultaneously, the optimal numbers of descriptions are distributed to D2D helpers and base stations in a cooperative scheme for transmitting to the D2D requesters. The optimal results are efficiently in correspondence with intra-popularity of different segments of a video characterized by requesters’ behavior, characteristic of lossy wireless channels, channel state information of D2D requesters, and constraints on remaining energy of D2D helpers and target signal to interference plus noise ratio of CUs. Simulation results demonstrate the benefits of our proposed solution in terms of high performance video streaming.

Effective Capacity of Licensed-Assisted Access in Unlicensed Spectrum for 5G: From Theory to Application

License-assisted access (LAA) is a promising technology to offload dramatically increasing cellular traffic to unlicensed bands. Challenges arise from the provision of quality-of-service (QoS) and the quantification of capacity, due to the distributed and heterogeneous nature of LAA and legacy systems (such as Wi-Fi) coexisting in the bands. In this paper, we develop new theories of the effective capacity to measure LAA under statistical QoS requirements. A new four-state semi-Markovian model is developed to capture transmission collisions, random backoffs, and lossy wireless channels of LAA in distributed heterogeneous network environments. A closed-form expression for the effective capacity is derived to comprehensively analyze LAA. The four-state model is further abstracted to an insightful two-state equivalent which reveals the concavity of the effective capacity in terms of transmit rate. Validated by simulations, the concavity is exploited to maximize the effective capacity and effective energy efficiency of LAA, and provide significant improvements of 62.7% and 171.4%, respectively, over existing approaches. Our results are of practical value to holistic designs and deployments of LAA systems.

Performance analysis of XOR two‐way relay with finite buffers and instant scheduling

This study investigates the performance of practical wireless exclusive OR (XOR) two-way relay (TWR) system, in which finite buffer, lossy wireless channels and non-negligible signalling overhead are considered. Specifically, the authors develop a new analytical model to explicitly characterise the transmissions of both the end-nodes and the relay. The impact of scheduling on the throughput, queuing delay, power consumption and buffer overflow probability of XOR-TWR is evaluated. Validated by simulations, the model can precisely quantify the performance of XOR-TWR and adequately allocate the relay's buffer adapting to the wireless link qualities and signalling overhead.

Packet routing in 3D nanonetworks: A lightweight, linear-path scheme

Packet routing in nanonetworks requires novel approaches, which can cope with the extreme limitations posed by the nano-scale. Highly lossy wireless channels, extremely limited hardware capabilities and non-unique node identifiers are among the restrictions. The present work offers an addressing and routing solution for static 3D nanonetworks that find applications in material monitoring and programmatic property tuning. The addressing process relies on virtual coordinates from multiple, alternative anchor point sets that act as viewports. Each viewport offers different address granularity within the network space, and its selection is optimized by a packet sending node using a novel heuristic. Regarding routing, each node can deduce whether it is located on the linear segment connecting the sender to the recipient node. This deduction is made using integer calculations, node-local information and in a stateless manner, minimizing the computational and storage overhead of the proposed scheme. Most importantly, the nodes can regulate the width of the linear path, thus trading energy efficiency (redundant transmissions) for increased path diversity. This trait can enable future adaptive routing schemes. Extensive evaluation via simulations highlights the advantages of the novel scheme over related approaches.

Hybrid alternative receiver-sender approach with a coloured DR/BDR mechanism for the broadcast of safety messages in VANETs

Multi-hop broadcasting represents the key technique to disseminate warning messages in vehicular networks. Its core problem is how to minimise the number of redundantly received messages while maintaining good latency and reachability that are hard to achieve simultaneously owing to the vehicles mobility and the lossy wireless channel. The proposed Sender-Oriented approaches delay the rebroadcast and cannot ensure reliability. Receiver-oriented ones, which are most suitable for safety applications, have to benefit in an efficient way from the exchanged IEEE802.11P safety beacons. In this paper, we propose an alternative Receiver-Sender approach that combines advantages of the two existing approaches to ensure low latency and high reliability. To overcome the unreliability and broadcast overhead generated by periodic rebroadcasts and multiple relay schemes, we introduce a designated relay (DR)/backup designated relay (BDR) mechanism where the BDR has to replace the DR when detecting its failure in informing concerned vehicles based on exchanged coloured beacons. Simulations show that combining the two approaches with the DR/BDR mechanism has a better performance than using each approach separately.

Green two‐tiered wireless multimedia sensor systems: an energy, bandwidth, and quality optimisation framework

In wireless multimedia sensor systems (WMSSs), the devices are equipped with multiple energy-constrained camera sensors (CSs) distributed over bandwidth-constrained and lossy wireless channels, in catastrophe-prone areas. Meanwhile, multimedia applications, e.g. video streaming, require considerable energy and bandwidth resources to gain long lifetime and high streaming quality. This study proposes an energy, bandwidth, and quality (EBQ) optimisation framework for green two-tiered WMSSs. The first tier contains the CSs and the second tier includes cluster heads (CHs) selected from the CSs with higher available energy and processing capacity. In the EBQ optimisation framework, a rate allocation optimisation problem is formulated under given constraints of available backhaul bandwidth of the CHs and quality of received videos at base stations (BSs). This problem is solved for optimal encoding rates to packetise each video captured from different environments into multiple descriptions for transmission. Consequently, the average energy consumption per CS is minimised for long lifetime while conserving the bandwidth of the CHs and guaranteeing high quality of received videos for the purpose of monitoring at the BSs. Simulations demonstrate that the proposed EBQ optimisation framework can efficiently enhance the performance of green two-tiered WMSSs in terms of minimum energy consumption, bandwidth efficiency, and high quality.

Performance analysis of two‐way MAC layer network coding under finite relay buffer and non‐negligible signalling overhead

AbstractTwo‐way exclusive OR (XOR) relay can enable hidden nodes to exchange data with low delays and high data rate, while keeping signal processing simple. In this paper, we analyse practical two‐way XOR relaying systems, where finite relay buffer, non‐negligible signalling overhead, and lossy wireless channels are all captured. A two‐layer model is developed to characterise such practical two‐way relay systems, which is then reformulated into a Markov process after we project and combine inter‐layer state transitions of the two‐layer model. Using Markov techniques, we evaluate the steady state probabilities of the Markov process and, in turn, the key performance measures of two‐way XOR relaying, such as throughput, delay, and packet loss. The accuracy of our model is validated by simulations. Our model can also be used as an online tool to configure the buffer resources, adapting to wireless channel conditions and signalling requirements. Copyright © 2016 John Wiley & Sons, Ltd.

Wireless Sensor Array Network DoA Estimation from Compressed Array Data via Joint Sparse Representation.

A compressive sensing joint sparse representation direction of arrival estimation (CSJSR-DoA) approach is proposed for wireless sensor array networks (WSAN). By exploiting the joint spatial and spectral correlations of acoustic sensor array data, the CSJSR-DoA approach provides reliable DoA estimation using randomly-sampled acoustic sensor data. Since random sampling is performed at remote sensor arrays, less data need to be transmitted over lossy wireless channels to the fusion center (FC), and the expensive source coding operation at sensor nodes can be avoided. To investigate the spatial sparsity, an upper bound of the coherence of incoming sensor signals is derived assuming a linear sensor array configuration. This bound provides a theoretical constraint on the angular separation of acoustic sources to ensure the spatial sparsity of the received acoustic sensor array signals. The Cramr–Rao bound of the CSJSR-DoA estimator that quantifies the theoretical DoA estimation performance is also derived. The potential performance of the CSJSR-DoA approach is validated using both simulations and field experiments on a prototype WSAN platform. Compared to existing compressive sensing-based DoA estimation methods, the CSJSR-DoA approach shows significant performance improvement.

Modeling Reliable Broadcast of Data Buffer over Wireless Networks

Reliable transfer of a data buffer window over lossy wireless channels may require many retransmissions. Due to high power consumption of radio hardware and delay constraints of real time applications, wireless link protocols operating at resource poor environments aim to minimize the number of these retransmissions. In this paper, we consider reliable broadcast of the full buffer in a window to multiple recipients over wireless channels. We present a generic sender initiated negative acknowledgement based joint retransmission scheme and its mathematical analysis in terms of the total number of packets transmitted in a reliable transfer session. In the analysis, we assume that the communication channels have independent packet loss probabilities. Hence, some packets may successfully be received by only a subset of the receivers. The analysis concludes with a generalized formula derived as a function of number of receivers (k) and buffer size (N). The formula, which is also verified with simulations, can be useful as a basis for the theoretical analysis of joint retransmission based cooperative Automatic-Request-Reply (ARQ) protocols.

Top-Down TDMA Scheduling Algorithm in Wireless Sensor Networks

 Abstract—This paper aims at the design of a centralized-controlled TDMA scheduling algorithm in the single channel Wireless Sensor Network (WSN) environments. We consider the network scenario where packets generated by each WSN device are destined for the common Gateway. A Top-down scheduling mechanism is proposed to assign wireless devices near the Gateway with high priority for transmitting packets. Through simulations, this paper compares and analyzes the scheduling efficiency and packet delay performance achieved by the proposed mechanism and other related works under various network topologies and scenarios. We also investigate the capability of these algorithms in providing differentiated service to those packets with multiple frequency generation patterns and different priority orders. Furthermore, the lossy wireless channel with PDR<1 is also considered to evaluate the reliability performances. Performance results have revealed that the proposed mechanism can achieve satisfactory results in terms of packet delay and packet loss probability for lots of network scenarios.

UWB Wind Turbine Blade Deflection Sensing for Wind Energy Cost Reduction.

A new application of utilizing ultra-wideband (UWB) technology to sense wind turbine blade deflections is introduced in this paper for wind energy cost reduction. The lower UWB band of 3.1–5.3 GHz is applied. On each blade, there will be one UWB blade deflection sensing system, which consists of two UWB antennas at the blade root and one UWB antenna at the blade tip. The detailed topology and challenges of this deflection sensing system are addressed. Due to the complexity of the problem, this paper will first realize the on-blade UWB radio link in the simplest case, where the tip antenna is situated outside (and on the surface of) a blade tip. To investigate this case, full-blade time-domain measurements are designed and conducted under different deflections. The detailed measurement setups and results are provided. If the root and tip antenna locations are properly selected, the first pulse is always of sufficient quality for accurate estimations under different deflections. The measured results reveal that the blade tip-root distance and blade deflection can be accurately estimated in the complicated and lossy wireless channels around a wind turbine blade. Some future research topics on this application are listed finally.

Cooperative content and radio resource allocation for visual information maximization in a digital signage scenario

In this paper, we present a cooperative content and resource allocation algorithm that selects networks and sub-carriers for digital signage scenarios based on visual information. In these scenarios, both 2D and 3D content are handled in open space for the advertisement of commercial products. To quantify visual information, we propose a quality of visual service (QoVS) metric based on human perception. We then construct the expected QoVS problem to guarantee the maximum QoVS for service users. The QoVS is determined based on the level of 2D visual sensitivity, and on the ability to perform 3D binocular fusion by users located at various viewing distances. By utilizing the QoVS, we predict wireless packet errors and loss of visual information caused by limited radio resources. After 3D content is selected to be multicasted to users by means of the large displays, sub-carriers are optimally allocated for the remaining smartphone users to facilitate point-to-point communication through lossy wireless channels. Simulation results of the proposed scheme demonstrate the advantages of automatic control of visual information and radio resources for multiple users without additional interactions. Moreover, the method developed herein can be flexibly applied with low complexity to several visual application services provided over heterogeneous displays and channels, such as advertisements, exhibitions, and forums.

On the multi‐hop performance of receiver based MAC protocol in routing protocol for low‐power and lossy networks‐based low power and lossy wireless sensor networks

In this study, the authors focus on utilising receiver-based MAC protocol (RB-MAC) and adaptive RB-MAC in routing protocol for low power and lossy wireless sensor networks routing protocol in low-power and lossy wireless channel. This results in a cross-layer approach in which routing decisions can be made based on MAC-layer functionalities. The authors study the effects of multiple receiver nodes, size of preamble and variable duty-cycle in number of retransmissions. Retransmissions increase energy consumptions and delay. Analytical and numerical results confirm that the RB-MAC and adaptive RB-MAC outperform the existing state-of-the art sender-based MAC protocols in terms of end-to-end energy-efficiency, reliability and delay. Simulation result demonstrates that using receiver-based MAC protocols in RPL-based lossy channel imply less retransmissions than sender-based MAC.