Source Broadcasts Research Articles

Performance of distributed acoustic sensing relative to co-located hydrophone measurements

Distributed acoustic sensing (DAS) is a technology that transforms telecommunication fiber optic cables into dense sensor arrays by continuously transmitting pulses of light down the cable and measuring backscattering from natural inhomogeneities within the fiber cable. The technology can densely sample the acoustic field over long ranges (up to 100 km), providing a means for large scale passive acoustic monitoring. The DAS Calibration Experiment 2022 (DASCAL22) provides 9 days of co-located hydrophone and DAS data in Puget Sound, WA. The DAS data were recorded with a 2kHz sampling rate over ∼3.5 km of cable in a channel reaching close to 100 m depth and with DAS channels spaced 6.38 m. A combination of an active source broadcast from 1, 5, and 10 m depths, and passive signals (primarily boat noise) are used to investigate the capabilities of DAS to sense a range of frequencies and the impacts of the environment on those capabilities.

Impacts of seabed characteristics on short-range acoustic propagation in seismic surveys

An abundance of marine seismic reflection surveys with publicly available datasets have been collected over the last several decades to study the composition of the seabed up to multiple kilometers below the sea floor. In these surveys, a loud impulsive airgun source broadcasts sound into the seabed and the reflections from the seafloor and seabed layers are measured on a long (up to ∼15 km) towed hydrophone array. In these surveys, both the shallow seabed layers (several hundred meters below the seafloor) and deeper layers (multiple kilometers below the seafloor) can significantly impact the acoustic field in the water column at close ranges. Experimental data have shown instances of sound exposure levels (SEL) at ranges between ∼8 and 15 km that exceeded levels predicted by cylindrical spreading models by nearly 15 dB. This work aims to use the abundance of seismic data available to explore the relationship between seabed and sub-seabed characteristics and the acoustic field in the water column. Inversion results that provide seabed sound speed profiles and reflection characteristics will be used to understand the seabed characteristics and its potential effects on SELs or sound pressure levels evaluated along the towed array. [Work supported by ONR.]

AI based elderly fall prediction system using wearable sensors: A smart home-care technology with IOT

Impairment and a substantial decline in the mobility, independence, and quality of life of an elderly person. In this regard, the current work suggests a novel IoT-based system that makes the use of low-power wireless sensing the networks, big data, cloud computing and smart devices to detect falls of older persons in interior situations. A Three-dimensional axis accelerometer integrated into a wearable sixLowPAN device is utilised for this purpose and is in charge of gathering data collected from older people's movements in real-time. The Signals of the sensor are processed and analysed using a machine learning model on a sophisticated IoT gateway to give high efficiency in fall detection. We make use of low-cost wearable sensing devices from Apache Flink and MbientLab an open source broadcast engine, a short-term with a long memory network architecture, and categorization of fall. We examine the ideal Nyquist rate, sensor positioning, and multiple channeling information change using the training set, which was developed using the published dataset “MobiAct.” With a 95.87% accuracy rate, our edge computing system can detect falls using real-time data stream analytics.

A simple Encoding Scheme to Achieve the Capacity of Half-Duplex Relay Channel

In this paper, the Half-Duplex Relay Channel (HDRC) is thoroughly investigated. Even though this channel model is widely studied, the capacity is not yet fully understood and particularly has not been tightly expressed. In this work, a new capacity expression of the discrete memoryless HDRC is explicitly established. In particular, a new expression of the achievable rate is derived by taking advantage of the well-known capacity results of both the degraded broadcast channel and the multiple access channel. Specifically, in order to obtain the achievable rate, the transmission from the source to destination is operated over two phases. In the first phase, the broadcast phase, the source broadcasts to both relay and destination. In the second phase, both source and relay transmit to destination to form multiple access channel. Then, we prove that the new achievable rate meets the cut-set outer bound such that the capacity of the discrete memoryless HDRC is attained. Next, the new derived capacity result is extended to the case of additive Gaussian channel. Further, the attained capacity is analytically and then numerically shown to encompass all well-known available findings in the literature. Additional numerical examples are also shown to present the cases in which the relay is beneficial and how the achievable capacity varies with the source-relay and relay-destination channel gains.

Hybrid NOMA/OMA Broadcasting-and-Buffer-State-Based Relay Selection

In this paper, we propose a novel buffer-aided relay selection scheme that is capable of amalgamating the concepts of non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA) in the context of two-hop cooperative networks supporting multiple relays. This is enabled by allowing relay nodes to share a common information packet in their buffers with the aid of a source-to-relay broadcasting mode. Hence, the proposed relay selection scheme switches between diverse modes of uplink NOMA, downlink NOMA, unicast, source broadcasting, and cooperative beamforming. The theoretical bounds of the outage probability, throughput, average delay, and diversity order are derived for the proposed scheme, based on a Markov chain model. Through our analytical and numerical results, it is demonstrated that the proposed scheme is capable of switching to one of the best modes in an adaptive manner while outperforming the conventional buffer-aided cooperative schemes.

Joint Power Allocation in Classified WBANs With Wireless Information and Power Transfer

In this article, a classified system with a relay is investigated in wireless body area networks (WBANs), where some on-body sensors are divided into several sensor groups on the basis of different body parts. Not only can the network detect basic vital signs but also the physiological signals of special diseases. All groups of sensors and the relay harvest energy by the radio-frequency (RF) source broadcasting, then the same group of sensors simultaneously sends common information through cooperation to the source. Since the classified system is a confined system, we maximize the system throughput with a joint power allocation on maximum ratio combining (JPA-MRC) protocol, where the transmission power allocation at the relay is unequal for each relaying subslot. The optimal problem is solved by the Lagrange multiplier method and the Karush-Kuhn-Tucker (KKT) optimal conditions. To further the obtain optimal solution, we simplify co-optimization of relay power and sensor power to the optimization of single power by the equivalent channel gains. Analytical and simulation results show that our proposed optimal method can greatly improve the information throughput compared to the conventional mean power allocation method. In addition, the protocol based on the classified scheme outperforms than that of the conventional unclassified scheme. The impacts of various important system parameters are analyzed, which provide useful design insights under different cases.

Delay Performance of a Two-User Broadcast Channel with Security Constraints

In this paper, we consider the two-user broadcast channel with security constraints. We assume that a source broadcasts packets to two receivers, and that one of them has secrecy constraints, i.e., its packets need to be kept secret from the other receiver. The receiver with secrecy constraint has full-duplex capability, allowing it to transmit a jamming signal to increase its secrecy. We derive the average delay per packet and provide simulations and numerical results, where we compare different performance metrics for the cases when both receivers treat interference as noise, when the legitimate receiver performs successive decoding, and when the eavesdropper performs successive decoding. The results show that successive decoding provides better average packet delay for the legitimate user. Furthermore, we define a new metric that characterizes the reduction on the success probability for the legitimate user that is caused by the secrecy constraint. The results show that secrecy poses a significant amount of packet delay for the legitimate receiver when either receiver performs successive decoding. We also formulate an optimization problem, wherein the throughput of the eavesdropper is maximized under delay and secrecy rate constraints at the legitimate receiver. We provide numerical results for the optimization problem, where we show the trade-off between the transmission power for the jamming and the throughput of the non-legitimate receiver. The results provide insights into how channel ordering and encoding differences can be exploited to improve performance under different interference conditions.

Source Broadcasting and Asymmetric Data Transmission With Bandwidth Expansion

We consider the broadcasting of a scalar memoryless Gaussian source over a two-user Gaussian broadcast channel with bandwidth expansion. In concurrent with the source description, a message that should be decoded reliably just by the “higher quality” user is sent. Conditioned on the message rate, we derive a necessary condition for the achievability of a mean-squared-error distortion pair at the two receivers, which extends the Reznic–Feder–Zamir bound. This necessary condition and a sufficient condition that we derive establish the set of achievable energy-distortion exponents for this setting.

Distortion Bounds for Source Broadcast Problems

This paper investigates the joint source-channel coding problem of sending a memoryless source over a memoryless broadcast channel. An inner bound and several outer bounds on the admissible distortion region are derived, which respectively generalize and unify several existing bounds. As a consequence, we also obtain an inner bound and an outer bound for the degraded broadcast channel case. When specialized to the Gaussian or binary source broadcast, the inner bound and outer bound not only recover the best known inner bound and outer bound in the literature, but also generate some new results. Besides, we also extend the inner bound and outer bounds to the Wyner-Ziv source broadcast problem, i.e., source broadcast with side information available at decoders. Some new bounds are obtained when specialized to the Wyner-Ziv Gaussian and Wyner-Ziv binary cases.

Backbone Source and Positional Broadcast Routing for Emergency System in Urban VANETs

Backbone Source and Positional Broadcast Routing for Emergency System in Urban VANETs

Deterministic Broadcasting and Random Linear Network Coding in Mobile Ad Hoc Networks

Network coding has been successfully used in the past for efficient broadcasting in wireless multi-hop networks. Two coding approaches are suitable for mobile networks; random linear network coding (RLNC) and XOR-based coding. In this paper, we focus on the problem of multiple source broadcasting in mobile ad hoc networks. We make the observation that RLNC provides increased resilience to packet losses compared with XOR-based coding. We develop an analytical model that justifies our intuition. However, the model also reveals that combining RLNC with probabilistic forwarding, which is the approach taken in the literature, may significantly impact RLNC’s performance. Therefore, we take the novel approach to combine RLNC with a deterministic broadcasting algorithm in order to prune transmissions. More specifically, we propose a connected dominating set-based algorithm that works in synergy with RLNC on the “packet generation level.” Since managing packet generations is a key issue in RLNC, we propose a distributed scheme, which is also suitable for mobile environments and does not compromise the coding efficiency. We show that the proposed algorithm outperforms XOR-based as well as RLNC-based schemes even when global knowledge is used for managing packet generations.

Dual‐hop signal space cooperative systems using multiple DF relays

In a dual-hop relaying system without a direct link between the source and the destination, the source broadcasts information signal to the relay and relay broadcasts it to the destination, thus it uses two phases to transmit one symbol. This study proposes a novel scheme to incorporate signal space diversity into a dual-hop relaying system with multiple decode-and-forward (DF) relays to enhance its spectral efficiency. The proposed dual-hop signal space cooperative relaying scheme transmits two symbols in three phases while the conventional dual-hop DF relaying system uses four phases to transmit the same two symbols. Therefore, the proposed scheme improves the spectral efficiency without additional complexity, bandwidth or transmit power. The proposed scheme is analysed over Rayleigh fading channel and error probability performance is derived. Moreover, an asymptotic approximation for the error probability is obtained to illustrate the impact of different system parameters and diversity gain. In addition, this study discusses the power allocation optimisation, relay position optimisation and the joint optimisation of both. Furthermore, closed-form expression for the average channel capacity is derived. In the end, analytical results are compared and validated through Monte Carlo simulations.

Comments on “Approximate Characterizations for the Gaussian Source Broadcast Distortion Region”

Recently, Tian et al. [1] considered joint source-channel coding of transmitting a Gaussian source over $K$-user Gaussian broadcast channel, and derived an outer bound on the admissible distortion region. In [1], they stated "due to its nonlinear form, it appears difficult to determine whether it is always looser than the trivial outer bound in all distortion regimes with bandwidth compression". However, in this correspondence we solve this problem and prove that for the bandwidth expansion case ($K\geq2$), this outer bound is strictly tighter than the trivial outer bound with each user being optimal in the point-to-point setting; while for the bandwidth compression or bandwidth match case, this outer bound actually degenerates to the trivial outer bound. Therefore, our results imply that on one hand, the outer bound given in [1] is nontrivial only for Gaussian broadcast communication ($K\geq2$) with bandwidth expansion; on the other hand, unfortunately, no nontrivial outer bound exists so far for Gaussian broadcast communication ($K\geq2$) with bandwidth compression.

A Source-Channel Separation Theorem With Application to the Source Broadcast Problem

A converse method is developed for the source broadcast problem. Specifically, it is shown that the separation architecture is optimal for a variant of the source broadcast problem and the associated source-channel separation theorem can be leveraged, via a reduction argument, to establish a necessary condition for the original problem, which unifies several existing results in the literature. Somewhat surprisingly, this method, albeit based on the source-channel separation theorem, can be used to prove the optimality of non-separation based schemes and determine the performance limits in certain scenarios where the separation architecture is suboptimal.

Outer Bounds on the Admissible Source Region for Broadcast Channels With Correlated Sources

Two outer bounds on the admissible source region for broadcast channels with correlated sources are presented: the first one is strictly tighter than the existing outer bound by Gohari and Anantharam, while the second one provides a complete characterization of the admissible source region in the case where the two sources are conditionally independent given the common part. These outer bounds are deduced from the general necessary conditions established for the lossy source broadcast problem via suitable comparisons between the virtual broadcast channel (induced by the source and the reconstructions) and the physical broadcast channel.

Double-layer video transmission over decode-and-forward wireless relay networks using hierarchical modulation.

We consider a wireless relay network with a single source, a single destination, and a multiple relay. The relays are half-duplex and use the decode-and-forward protocol. The transmit source is a layered video bitstream, which can be partitioned into two layers, a base layer (BL) and an enhancement layer (EL), where the BL is more important than the EL in terms of the source distortion. The source broadcasts both layers to the relays and the destination using hierarchical 16-QAM. Each relay detects and transmits successfully decoded layers to the destination using either hierarchical 16-QAM or QPSK. The destination can thus receive multiple signals, each of which can include either only the BL or both the BL and the EL. We derive the optimal linear combining method at the destination, where the uncoded bit error rate is minimized. We also present a suboptimal combining method with a closed-form solution, which performs very close to the optimal. We use the proposed double-layer transmission scheme with our combining methods for transmitting layered video bitstreams. Numerical results show that the double-layer scheme can gain 2-2.5 dB in channel signal-to-noise ratio or 5-7 dB in video peak signal-to-noise ratio, compared with the classical single-layer scheme using conventional modulation.

Performance Comparisons of Optimal Power Allocation over Nakagami-m and Rayleigh Fading Channels in Wireless Cooperative Systems

Cooperative wireless communication has been newly proposed in wireless communication systems for discovering the inherent spatial diversity in relay channels. The Amplify- and-Forward (AF) cooperation protocols with multiple relays have not been sufficiently examined; however, it has a low complexity in terms of application. Through this article, we evaluate a cooperative diversity technique whereby a source broadcasts some data to a destination with the assistance of multiple relay nodes with AF protocols, by taking into account the challenge of allocating power to be able to increase the total capacity of AF and also enhance resource utilization. We analyse the optimality of how much the power should really be allocated at the source as well as relays system by optimizing the symbol error rate (SER) performance in a useful method on the basis of Rayleigh and Nakagami- m fading. Firstly, we derive a closed-form SER formulation for MPSK signal making use of the idea of moment generating function (MGF) and some statistical approximations in high signal to noise ratio (SNR) for the system under studied. We therefore determine a tight corresponding lower bound, which converges to the identical limit the same as the theoretical upper bound, after that develops an optimal power allocation (OPA) strategy with mean channel gains over Rayleigh and also Nakagami- m fading to reduce the SER. Simulation results prove that our approach using Nakagami- m fading outperforms the (OPA) using Raleigh fading scheme and is tight with the theoretical approximation based on the SER upper bound in high SNR for a different number of relays .  Index Terms—Wireless communication, amplify-and-forward, symbol error rate, Nakagami- m fading, power allocation.

Performance Analysis of Improving ZigBee Wireless Network Using AODV Mesh Routing Model

ZigBee is an emerging standard for the low cost, low power and low rate wireless networks and the ZigBee technology is well suited to a wide range of energy management and efficiency applications in areas such as building automation, industrial, medical and home automation. ZigBee is a version of AODV routing protocol, where the routes are discovered RREQ through the network by the source broadcasting and sending RREP back the destination, so make ZigBee routing efficient, we used AODV mesh topology methods to send and receive data from source to destination and vice versa. In this paper we present an improved version of ZigBee-AODV mesh network, which utilizes and divide the topology of network into one or more logical clusters and restricts the flooding of route request outside the cluster. ZigBee-AODV mesh network uses nodes of the same cluster to share routing information, which significantly reduces the route path discovery and created cluster formation to decrease the routing path. The proposed protocol has higher reliability and lower overhead than AODV.

Multisource Broadcast in Wireless Networks

Nowadays, there is urgent demand for wireless sensor network applications. In these applications, usually a base station is responsible for monitoring the entire network and collecting information. If emergency happens, it will propagate such information to all other nodes. However, quite often the message source is not a fixed node, since there may be base stations in charge of different regions or events. Therefore, how to propagate information efficiently when message sources vary from time to time is a challenging issue. None of conventional broadcast algorithms can deal with this case efficiently, since the change of message source incurs a huge implementation cost of rebuilding a broadcast tree. To deal with this difficult problem, we make endeavor in studying multiple source broadcast, in which targeted algorithms should be source-independent to serve the practical need. In this paper, we formulate the Minimum-Latency Multisource Broadcast problem. We propose a novel solution using a fixed shared backbone, which is independent of the message sources and can be used repeatedly to reduce the broadcast latency. To the best of our knowledge, our work is deemed the first attempt to design such a multisource broadcast algorithm with a derived theoretical latency upper bound.

Stability-Based RREQ Forwarding Game for Stability-Oriented Route Discovery in MANETs

In traditional stability-oriented route discovery of mobile ad hoc networks, in-between nodes need to rebroadcast identical route request (RREQ) packets, which contain same source node ID and broadcast sequence number, to discover more stable route, yet it increases routing overhead and data transmission delay obviously. Therefore, a stability-oriented route discovery algorithm is proposed to limit routing overhead and decrease transmission delay. In this algorithm, all neighbor nodes of some node will play a mix strategy game named stability-based RREQ forwarding game after receiving an identical RREQ, and independently determine the RREQ forwarding probability based on Nash equilibrium, respectively. The simulation results show that the proposed stability-oriented route discovery algorithm not only reduces routing overhead and transmission delay effectively, but also improve other routing performance.