Consensus of multi-agent systems with faults and mismatches under switched topologies using a delta operator method

© 2018 Elsevier B.V. This paper studies the consensus of multi-agent systems with faults and mismatches under switched topologies using a delta operator method. Since faults and mismatches can result in failure of the consensus even for a fixed topology with a spanning tree, how to reach a consensus is a complicated and challenging problem under such circumstances especially when part topologies have no spanning tree. Although some works studied the influence of faults and mismatches on the consensus, there is little work on reaching a consensus for the multi-agent systems with faults and mismatches. In this paper, we introduce the delta operator to unify the consensus analysis for continuous, discrete, or sampled systems under one framework. We develop the theories on the delta operator systems first and then apply theories of the delta operator systems to the consensus problems. By converting the consensus problems into stability problems, we investigate and prove consensus and the associated conditions for systems 1) without any fault, 2) with a known fault, and 3) with unknown faults, under switching topologies with matching or mismatching coefficients. Numerical examples are provided and validate the effectiveness of the theoretical results

Functional genomics in forage and turf - present status and future prospects

The recent advances in plant genomics have greatly influenced basic research in many agriculturally important crops. Along with the availability of complete genome information from the model grass species rice and the model legume species M. trucncatula, the functional genomics activities in other crop species will accelerate the genomics studies of forage and turf. Brachypodium distachyon was recently proposed as a new model plant for forage and turf grass genomics studies. The combination of bioinformatics and genomics will enhance our understanding of the molecular functions of forage and turf species. This review focuses on recent advances and applications of functional genomics for large-scale EST projects, global gene expression analyses, proteomics, and metabolic profiling, as well as the impact of functional genomics on improvement of forage and turf crops. Key words: Functional genomics, forage and turf grasses, ESTs, microarray, proteomics, metabolomics, Medicago truncatula, legume. African Journal of Biotechnology Vol. 2 (12), pp. 521-527, December 200

Multi-gigabit microwave and millimeter-wave communications research at CSIRO

© 2014 IEEE. High speed and long range wireless backhauls are cost-effective alternatives to fibre networks and becoming more and more attractive as the demand for broadband wireless services grows rapidly in recent years. However, current commercially available wireless backhaul systems neither provide sufficiently high speed nor meet the requirements to achieve both high speed and long range at the same time with sufficiently low latency for targeted applications. Traditional microwave systems can achieve long transmission range, but the data rates are limited to a few hundred Mega bits per second only. Multi-Gigabit wireless communications can be achieved using millimetre-wave (mm-wave) frequency bands, especially the E-bands, but the practical transmission range is still a major weakness. In this paper, the state-of-the-art microwave and mm-wave technologies developed at the Commonwealth Scientific and Industrial Research Organization (CSIRO) are introduced to demonstrate CSIRO's technology leadership in multi-Gigabit wireless communications research and development. The technology trends in multi-Gigabit wireless communications are also discussed and various recently developed microwave and mm-wave systems are compared. It is hoped that this paper will stimulate further research interest and industry development

A 30 Gbps Low-Complexity and Real-Time Digital Modem for Wireless Communications at 0.325 THz

© 2019 IEEE. A high-speed wideband terahertz (THz) communication system with low-complexity and real-time digital signal processing (DSP) is presented in this paper. The architectures of baseband platform, intermediate frequency (IF) module and radio frequency (RF) frontend are described. For real-time DSP implementation with affordable field programmable gate array (FPGA) device, some effective strategies are discussed to reduce resource usage and ensure that the clock constraints are met. Adopting these strategies, all physical layer DSP modules are implemented in two FPGAs with more than 300 MHz system clock. The experimental test results using the developed real-time digital modem prototype demonstrate the superb performance for THz wireless communications

Unified out-of-band emission reduction with linear complexity for OFDM

© 2014 IEEE. This paper proposes a unified out-of-band emission (OOBE) reduction framework with linear complexity for orthogonal frequency-division multiplexing (OFDM) systems. Unlike conventional spectral precoding approaches which use orthogonal precoding matrixes, this framework composes cancellation signals from the linear combinations of data symbols and minimizes the average OOBE power with a general least-squares solution. A joint frequency domain cancellation subcarrier and data domain cancellation symbol allocation scheme is also proposed for discrete Fourier transform precoded OFDM, by which the overall signal processing complexity of the OFDM transceiver is further reduced without impact on other system performance. The advantages of the proposed scheme is verified both analytically and by simulation as compared with some well-known low-complexity OOBE reduction schemes

Joint transmitter and receiver I/Q imbalance estimation in presence of carrier frequency offset

© 2015 IEEE. This paper proposes a simple frequency domain joint transmitter and receiver I/Q imbalance estimation method which exploits the phase rotation introduced by carrier frequency offset. Using two frequency domain training sequences inserted in each transmission frame, the transmitter and receiver I/Q imbalances can be jointly estimated over multiple frames. The transmitter I/Q imbalance parameter can be fed back to the transmitter for I/Q imbalance pre-compensation, whereas the receiver I/Q imbalance can be compensated locally followed by conventional frequency domain equalization. Numerical simulation results show that the image rejection ratios for both transmitter and receiver after I/Q imbalance compensation can be improved to over 50 dB which is necessary for multichannel systems with high order modulation and wide transmission bandwidth

Wireless Device-to-Device Caching Networks with Distributed MIMO and Hierarchical Cooperations

© 2017 IEEE. In this paper, we propose a new caching scheme for a random wireless device-to-device (D2D) network of n nodes with local caches, where each node intends to download files from a prefixed library via D2D links. Our proposed caching delivery includes two stages, employing distributed MIMO and hierarchical cooperations respectively. The distributed MIMO is applied to the first stage between source nodes and neighbours of the destination node. The induced multiplexing gain and diversity gain increase the number of simultaneous transmissions, improving the throughput of the network. The hierarchical cooperations are applied to the second stage to facilitate the transmissions between the destination node and its neighbours. The two stages together exploit spatial degrees of freedom as well as spatial reuse. We develop an uncoded random caching placement strategy to serve this cooperative caching delivery. Analytical results show that the average aggregate throughput of the network scales almost linearly with n, with a vanishing outage probability

Directional antennas for point-to-multipoint millimetre wave communications

© 2016 IEEE. In this paper, we investigate the feasibility and potential performance of applying an antenna array of directional elements such as horn antennas for mmWave point-to-multipoint communications. We propose a conceptual design of the array, and review options for antenna elements and mechanical steering devices. We then estimate the achievable performance with respect to link data rate and distance, and show that pointing to users exactly does not always achieve system capacity, but the gap is typically small. We also provide comparison for two types of multiple access schemes

Massive hybrid antenna array for millimeter-wave cellular communications

© 2002-2012 IEEE. A massive hybrid array consists of multiple analog subarrays, with each subarray having its digital processing chain. It offers the potential advantage of balancing cost and performance for massive arrays and therefore serves as an attractive solution for future millimeter-wave (mm- Wave) cellular communications. On one hand, using beamforming analog subarrays such as phased arrays, the hybrid configuration can effectively collect or distribute signal energy in sparse mm-Wave channels. On the other hand, multiple digital chains in the configuration provide multiplexing capability and more beamforming flexibility to the system. In this article, we discuss several important issues and the state-of-the-art development for mm-Wave hybrid arrays, such as channel modeling, capacity characterization, applications of various smart antenna techniques for single-user and multiuser communications, and practical hardware design. We investigate how the hybrid array architecture and special mm-Wave channel property can be exploited to design suboptimal but practical massive antenna array schemes. We also compare two main types of hybrid arrays, interleaved and localized arrays, and recommend that the localized array is a better option in terms of overall performance and hardware feasibility

A Linear Network Coding Approach for Uplink Distributed MIMO Systems: Protocol and Outage Behavior

© 1983-2012 IEEE. A distributed multiple-input-multiple-output (MIMO) system consists of M users served by L distributed base stations (BSs) , where the BSs are connected to a central unit (CU) via L independent backhaul (BH) links. In this paper, we consider the design of an uplink distributed MIMO system where 1) the channel state information is not available at the transmitters and 2) the BH links are rate constrained. We propose a new linear network coding (LNC)-based protocol: the M users transmit simultaneously. Each BS generates N linear functions of the M users' messages, based on a preassigned LNC coefficient matrix. The CU collects N ·L linear functions from the L BSs and recovers all M users' messages by solving these linear functions. The decoding becomes successful if the linear functions has full rank M and fails if the linear functions are rank deficient. We derive the preassigned LNC coefficient matrix that minimizes the probability of rank deficiency. We then analyze the outage probability (OP) of the proposed scheme over a Rayleigh fading channel. We analytically show that as long as the BH rate is greater than the individual data rate of one user, the OP of the proposed scheme decays like 1/SNRL at high SNR. This is in contrast to the existing scheme whose OP decays like 1/SNRL. As the BH rate constraint approaches M times the data rate of one user, the performance of the proposed scheme is 10/L log10 (L!) dB away from that of the full MIMO scenario at high SNR. We also develop a structured way to efficiently construct the preassigned LNC coefficient matrix that yields the optimized OP performance. Numerical results show that the proposed scheme has significantly improved performance over existing schemes