Multiplexing Configuration Research Articles

A Performance Analysis of a Hybrid OCDMA-PON Configuration Based on IM/DD Fast-OFDM Technique for Access Network

The purpose of this article is to propose a new configuration based on OCDMA and Fast-OFDM techniques for access network applications. A hybrid intensity modulation with direct detection, fast orthogonal frequency-division multiplexing–code division multiplexing access (IM/DD Fast-OFDM-CDMA) system is analytically and numerically evaluated for an amplifier-free access network. Therefore, system performance is analytically investigated in terms of bit error rate/Q-factor as a function of simultaneous users, fiber length and launched optical power. Firstly, the proposed analytical model includes the overlapping effect among OFDM subcarriers, the peak-to-average power ratio (PAPR), and multiple access interference (MAI). Secondly, a simulation setup is performed, allowing four simultaneous users operating at 40 Gb/s in a passive optical network (PON) context. Furthermore, a power budget analysis is made between IM/DD Fast-OFDM-CDMA, all-optical IM/DD OFDM-CDMA (IM/DD AO-OFDM-CDMA) and OCDMA wavelength division multiplexing (OCDMA-WDM) configurations. It is shown that at 40 Gb/s and by using 2D-hybrid coding (2D-HC), the maximum achievable transmission-reach of IM/DD Fast-OFDM-CDMA is 142 km, which is 34 km and 60 km higher than those provided by the IM/DD AO-OFDM-OCDMA and OCDMA-WDM PON configurations, respectively.

Air‐interface virtualization using filter bank multicarrier and orthogonal frequency division multiplexing configurations

AbstractMobile networks have to cater for diverse services that have distinct requirements in terms of bandwidth, latency, and so on. Network virtualization is a key technology that efficiently utilizes the network resources to meet these service requirements. In this work, we investigate radio virtualization for creating fine‐grained network slices using orthogonal frequency division multiplexing (OFDM) and filter bank multicarrier (FBMC) combinations; the two are individually referred to as virtual radios (VRs). Using universal software radio peripherals (USRPs), we experimentally analyze multiple configurations of VRs including OFDM‐OFDM, OFDM‐FBMC, and FBMC‐FBMC. An extensive performance comparison is done on the basis of error rate, spectral efficiency, interference power, and computational complexity of the VR configurations that are confined within an operational bandwidth. An increase in transmit power of the VRs is theoretically expected to decrease the error rate, but there is also an increase in adjacent channel interference. Therefore, after a certain decrease in error rate with increase in transmit power, an inflection point is reached after which the error rate starts to increase. Of the three combinations, FBMC‐FBMC gives the lowest error rate (at the highest transmit power), that is, 10% and 18% lower than OFDM‐FBMC and OFDM‐OFDM, respectively. However, FBMC‐FBMC also has the highest complexity. We conclude that this air‐interface virtualization framework allows the network to use the waveform configuration that is best suited to a particular set of services, while considering the pros and cons of the individual waveforms.

Superconducting Nanowire Photon-Number-Resolving Detectors Integrated with Current Reservoirs

Photon-number-resolving detectors (PNRDs) play pivotal roles in many quantum-photonic applications; and intrinsic and multiplexed PNRDs have been reported previously. However, for intrinsic PNRDs, the maximum resolvable photon number is limited to a few photons; for the multiplexed PNRDs, the fidelity generally decreases when the to-be-resolved photon number becomes large. Here, to resolve more photons with high fidelity, we report on combined PNRDs, based on a spatial multiplexing configuration of multiple elements, each capable of resolving a few photons. After setting up a model and calculating the fidelity, we propose a possible physical system to realize the combined PNRDs. The proposed detectors are based on the superconducting nanowire multiphoton detectors integrated with current reservoirs that we recently reported, but are designed and configured into PNRDs. Specifically, information about the detected photon numbers is stored in the format of the supercurrent in the current reservoir and then readout by an integrated yTron. We present in detail the operating principle and show a design that can resolve up to 11 photons with high fidelity.

Intra-Network Interference Robustness: An Empirical Evaluation of IEEE 802.15.4-2015 SUN-OFDM

While IEEE 802.15.4 and its Time Slotted Channel Hopping (TSCH) medium access mode were developed as a wireless substitute for reliable process monitoring in industrial environments, most deployments use a single/static physical layer (PHY) configuration. Instead of limiting all links to the throughput and reliability of a single Modulation and Coding Scheme (MCS), you can dynamically re-configure the PHY of link endpoints according to the context. However, such modulation diversity causes links to coincide in time/frequency space, resulting in poor reliability if left unchecked. Nonetheless, to some level, intentional spatial overlap improves resource efficiency while partially preserving the benefits of modulation diversity. Hence, we measured the mutual interference robustness of certain Smart Utility Network (SUN) Orthogonal Frequency Division Multiplexing (OFDM) configurations, as a first step towards combining spatial re-use and modulation diversity. This paper discusses the packet reception performance of those PHY configurations in terms of Signal to Interference Ratio (SIR) and time-overlap percentage between interference and targeted parts of useful transmissions. In summary, we found SUN-OFDM O3 MCS1 and O4 MCS2 performed best. Consequently, one should consider them when developing TSCH scheduling mechanisms in the search for resource efficient ubiquitous connectivity through modulation diversity and spatial re-use.

Traffic-driven epidemic spreading in multiplex networks.

Recent progress on multiplex networks has provided a powerful way to abstract the diverse interaction of a network system with multiple layers. In this paper, we show that a multiplex structure can greatly affect the spread of an epidemic driven by traffic dynamics. One of the interesting findings is that the multiplex structure could suppress the outbreak of an epidemic, which is different from the typical finding of spread dynamics in multiplex networks. In particular, one layer with dense connections can attract more traffic flow and eventually suppress the epidemic outbreak in other layers. Therefore, the epidemic threshold will be larger than the minimal threshold of the layers. With a mean-field approximation, we provide explicit expressions for the epidemic threshold and for the onset of suppressing epidemic spreading in multiplex networks. We also provide the probability of obtaining a multiplex configuration that suppresses the epidemic spreading when the multiplex is composed of: (i) two Erdős-Rényi layers and (ii) two scale-free layers. Therefore, compared to the situation of an isolated network in which a disease may be able to propagate, a larger epidemic threshold can be found in multiplex structures.

Efficient Weighted Least-Squares Frequency Synchronization Scheme for Digital Terrestrial Broadcasting System

The integrated services digital broadcasting-terrestrial (ISDB-T) system provides the interesting advantages of hierarchical transmission and partial reception using band segmented transmission orthogonal frequency division multiplexing scheme. In ISDB-T, the hierarchical configuration varies depending on whether a segment is modulated coherently or differentially. Thus, it is important to accomplish frequency synchronization regardless of segment type. For this purpose, an effective weighted least-squares (WLS) carrier frequency synchronization method is presented using transmission and multiplexing configuration control (TMCC) and auxiliary channel (AC) in a blind manner. Thus, the proposed estimation scheme is performed without resorting to a priori knowledge on segment type that can be known after correct TMCC decoding. To eliminate bias caused by using non-uniformly distributed TMCC and AC subcarriers, an appropriate subset is selected to form the basis of robust WLS estimation. Extensive simulations are conducted to verify the efficiency of the proposed WLS estimation method and compare its performance with that of the conventional WLS estimation scheme.

Robust Blind Detection of Integer Carrier Frequency Offset for Terrestrial Broadcasting Systems Using Band Segmented Transmission

In the integrated services digital broadcasting-terrestrial (ISDB-T) system, the combination of digital terrestrial transmission and MPEG-4 advanced video coding (MPEG-4 AVC) has offered ways to provide a variety of digital high-definition television (HDTV) programs. Using band segmented transmission orthogonal frequency division multiplexing (BST-OFDM), the delivery of innovative video-on-demand and HDTV services is supported. To take full advantage of the attractive benefits of BST-OFDM, it is important to estimate integer frequency offset (IFO) without a priori knowledge on the segment type that is transmitted over transmission and the multiplexing configuration control (TMCC) signal. To address this issue, an efficient IFO detection method is proposed for the ISDB-T system employing BST-OFDM. To enable IFO detection independent of the segment type, information-bearing TMCC signals that are asymmetrically distributed in the frequency domain are used as pilot symbols. Numerical analysis is performed to present the relationship between error probability and design parameter. We show via the numerical results that the multiple transmitted TMCC information is efficiently used for blind estimation of the IFO, achieving robust estimation in the presence of the fractional frequency offset.

Suboptimal Maximum Likelihood Detection of Integer Carrier Frequency Offset for Digital Terrestrial Television Broadcasting System

The integrated services digital broadcasting-terrestrial (ISDB-T) system adopts band segmented transmission orthogonal frequency division multiplexing (BST-OFDM) to support different services using hierarchical transmission. In the ISDB-T system, in particular, a hierarchical configuration depends on modulation type used in OFDM segment, which has to be decoded at the receiver. Therefore, it is necessary to detect integer carrier frequency offset (IFO) before decoding the modulation type carried through transmission and multiplexing configuration control (TMCC) signal. To address this issue, an effective IFO estimation scheme is presented for the ISDB-T system, considering information-carrying TMCC signal as pilot symbol without any need of additional pilots. In order to verify the performance of the proposed estimation scheme, theoretical detection error rate is derived. It is shown from simulation results that the redundantly transmitted TMCC signal can be efficiently utilized for IFO detection, offering an approximate performance of maximum likelihood detection.

Solitary states in multiplex networks owing to competing interactions.

Recent researches in network science demonstrate the coexistence of different types of interactions among the individuals within the same system. A wide range of situations appear in ecological and neuronal systems that incorporate positive and negative interactions. Also, there are numerous examples of systems that are best represented by the multiplex configuration. The present article investigates a possible scenario for the emergence of a newly observed remarkable phenomenon named as solitary state in coupled dynamical units in which one or a few units split off and behave differently from the other units. For this, we consider dynamical systems connected through a multiplex architecture in the presence of both positive and negative couplings. We explore our findings through analysis of the paradigmatic FitzHugh-Nagumo system in both equilibrium and periodic regimes on the top of a multiplex network having positive inter-layer and negative intra-layer interactions. We further substantiate our proposition using a periodic Lorenz system with the same scheme and show that an opposite scheme of competitive interactions may also work for the Lorenz system in the chaotic regime.

Effective Blind Frequency Offset Estimation Scheme for BST-OFDM Based HDTV Broadcast Systems

The integrated services digital broadcasting-terrestrial (ISDB-T) system is designed in order to accommodate high-quality video/audio and multimedia services, using band segmented transmission orthogonal frequency division multiplexing (BST-OFDM) scheme. In the ISDB-T system, the pilot configuration varies depending on whether a segment uses a coherent or differential modulation. Therefore, it is necessary to perform a joint estimation of carrier frequency offset (CFO) and sampling frequency offset (SFO) independent of the segment format in the ISDB-T system. The goal is to complete those synchronization tasks while considering an information-carrying transmission and multiplexing configuration control (TMCC) signal as pilot symbols. It is demonstrated through numerical simulations that the differential BPSK-modulated TMCC information can be efficiently used for a least-squares estimation of CFO and SFO, offering an acceptable performance.

Relay synchronization in multiplex networks

Relay (or remote) synchronization between two not directly connected oscillators in a network is an important feature allowing distant coordination. In this work, we report a systematic study of this phenomenon in multiplex networks, where inter-layer synchronization occurs between distant layers mediated by a relay layer that acts as a transmitter. We show that this transmission can be extended to higher order relay configurations, provided symmetry conditions are preserved. By first order perturbative analysis, we identify the dynamical and topological dependencies of relay synchronization in a multiplex. We find that the relay synchronization threshold is considerably reduced in a multiplex configuration, and that such synchronous state is mostly supported by the lower degree nodes of the outer layers, while hubs can be de-multiplexed without affecting overall coherence. Finally, we experimentally validated the analytical and numerical findings by means of a multiplex of three layers of electronic circuits.

On the Performance of Multiplexing FSO MIMO Links in Log-Normal Fading With Pointing Errors

In this paper, we employ a spatial multiplexing scheme with M transceivers to increase the data rate of a free-space optical (FSO) system. In our proposed scheme, each transmitter sends independent information toward the center of its related receiver aperture. We analyze the performance of the proposed scheme in terms of average achievable rate. To compare the performance of our proposed scheme with its spatial diversity FSO system counterpart, we define a case in which M transmitters send the same information. To facilitate performance analysis, we also derive the analytical expressions for spectral efficiency of both spatial multiplexing and diversity configurations, which reduces the (M+2)-dimensional integration of spatial multiplexing and (M2+2)-dimensional integration of spatial diversity FSO systems to a two-dimensional integration in both configurations. The adequacies of our analytical results are thoroughly confirmed by numerical simulations.

Nucleic acid sensing with enzyme-DNA binding protein conjugates cascade and simple DNA nanostructures.

A versatile and universal DNA sensing platform is presented based on enzyme-DNA binding protein tags conjugates and simple DNA nanostructures. Two enzyme conjugates were thus prepared, with horseradish peroxidase linked to the dimeric single-chain bacteriophage Cro repressor protein (HRP-scCro) and glucose oxidase linked to the dimeric headpiece domain of Escherichia coli LacI repressor protein (GOx-dHP), and used in conjunction with a hybrid ssDNA-dsDNA detection probe. This probe served as a simple DNA nanostructure allowing first for target recognition through its target-complementary single-stranded DNA (ssDNA) part and then for signal generation after conjugate binding on the double-stranded DNA (dsDNA) containing the specific binding sites for the dHP and scCro DNA binding proteins. The DNA binding proteins chosen in this work have different sequence specificity, high affinity, and lack of cross-reactivity. The proposed sensing system was validated for the detection of model target ssDNA from high-risk human papillomavirus (HPV16) and the limits of detection of 45, 26, and 21pM were achieved using the probes with scCro/dHP DNA binding sites ratio of 1:1, 2:1, and 1:2, respectively. The performance of the platform in terms of limit of detection was comparable to direct HRP systems using target-specific oligonucleotide-HRP conjugates. The ratio of the two enzymes can be easily manipulated by changing the number of binding sites on the detection probe, offering further optimization possibilities of the signal generation step. Moreover, since the signal is obtained in the absence of externally added hydrogen peroxide, the described platform is compatible with paper-based assays for molecular diagnostics applications. Finally, just by changing the ssDNA part of the detection probe, this versatile nucleic acid platform can be used for the detection of different ssDNA target sequences or in a multiplex detection configuration without the need to change any of the conjugates. Graphical abstract DNA sensing platform based on an immobilized ssDNA capture probe and a hybrid ssDNA-dsDNA detection probe that specifically hybridize with the ssDNA target. The hybrid ssDNA-dsDNA detection probe also provides the binding sites for the enzyme-DNA binding protein conjugates (HRP-scCro and GOx-dHP) that generate the colorimetric signal.

Improving LTE ${e}$ MBMS With Extended OFDM Parameters and Layered-Division-Multiplexing

The evolved multimedia broadcast multicast service ( ${e}$ MBMS) system was developed to achieve higher spectrum efficiency on video traffic delivery over the long term evolution (LTE) networks. As an integrated component of the LTE, ${e}$ MBMS can be deployed with great flexibility using the existing LTE infrastructure. However, the current ${e}$ MBMS was designed as a supplementary subsystem, and has limited capability to deliver high-quality broadcast-type video services in a spectrum efficient manner. This paper first studies the capability and limitations of the current LTE ${e}$ MBMS system to deliver broadcast services when deployed as single-frequency-network (SFN). Next, potential physical-layer enhancements are investigated for future ${e}$ MBMS systems to achieve enhanced broadcast service delivery capability, higher spectrum efficiency, improved service quality, and more efficient SFN deployment options. These include wideband transmission, non-orthogonal multiplexing, e.g., layered-division-multiplexing technology, and more flexible orthogonal frequency division multiplexing system configurations, such as longer cyclic prefix and smaller subcarrier spacing. Other technologies defined in the latest next generation digital television system are also discussed that might be applicable to the development of a more capable standalone future ${e}$ MBMS system.

Design of manifold multiplexers in all‐inductive dual‐mode rectangular waveguide technology using the coupling matrix formalism

AbstractThis paper presents for the first time the design of manifold multiplexers in waveguide technology using all‐inductive dual‐mode channel filters. It is shown that very complex transfer functions can be implemented for the channels, using simple structures that can be analyzed and manufactured with increased simplicity as compared to other commercial solutions. In this paper we adapt a standard design technique for manifold multiplexers to the new proposed technology. The paper is illustrated with the design of two triplexers, using H‐type and E‐type waveguide manifolds, with filters implementing two transmission zeros in the insertion loss response for maximum isolation between channels. Results show that the procedure is indeed effective and can be used for the design of practical multiplexer configurations.

Maximizing algebraic connectivity in interconnected networks.

Algebraic connectivity, the second eigenvalue of the Laplacian matrix, is a measure of node and link connectivity on networks. When studying interconnected networks it is useful to consider a multiplex model, where the component networks operate together with interlayer links among them. In order to have a well-connected multilayer structure, it is necessary to optimally design these interlayer links considering realistic constraints. In this work, we solve the problem of finding an optimal weight distribution for one-to-one interlayer links under budget constraint. We show that for the special multiplex configurations with identical layers, the uniform weight distribution is always optimal. On the other hand, when the two layers are arbitrary, increasing the budget reveals the existence of two different regimes. Up to a certain threshold budget, the second eigenvalue of the supra-Laplacian is simple, the optimal weight distribution is uniform, and the Fiedler vector is constant on each layer. Increasing the budget past the threshold, the optimal weight distribution can be nonuniform. The interesting consequence of this result is that there is no need to solve the optimization problem when the available budget is less than the threshold, which can be easily found analytically.

Fast and Chaotic Fiber-Based Nonlinear Polarization Scrambler

We report a simple and efficient all-optical polarization scrambler based on the nonlinear interaction in an optical fiber between a signal beam and its backward replica which is generated and amplified by a reflective loop. When the amplification factor exceeds a certain threshold, the system exhibits a chaotic regime in which the evolution of the output polarization state of the signal becomes temporally chaotic and scrambled all over the surface of the Poincare sphere. We numerically derive some design rules for the scrambling performances of our device which are well confirmed by the experimental results. The polarization scrambler has been successfully tested on a 10-Gb/s On/Off Keying Telecom signal, reaching scrambling speeds up to 500-krad/s, as well as in a wavelength division multiplexing configuration. A different configuration based on a following cascade of polarization scramblers is also discussed numerically, which leads to an increase of the scrambling performances.

Control of Multilayer Networks.

The controllability of a network is a theoretical problem of relevance in a variety of contexts ranging from financial markets to the brain. Until now, network controllability has been characterized only on isolated networks, while the vast majority of complex systems are formed by multilayer networks. Here we build a theoretical framework for the linear controllability of multilayer networks by mapping the problem into a combinatorial matching problem. We found that correlating the external signals in the different layers can significantly reduce the multiplex network robustness to node removal, as it can be seen in conjunction with a hybrid phase transition occurring in interacting Poisson networks. Moreover we observe that multilayer networks can stabilize the fully controllable multiplex network configuration that can be stable also when the full controllability of the single network is not stable.

Present and Future Trends in Filters and Multiplexers

In the last 10 or 15 years, exciting new developments have occurred in the field of filters and multiplexers. The two words that best explain this phenomenon are “topology” and “technology.” Thus, this paper will cover new connections, new materials, and new processes. This paper summarizes what is new, describes the new devices, and avoids simply surveying the entire field. It is not possible to cover everything, and regrettably, some new and possibly exciting areas are omitted (such as filters fabricated using liquid crystal polymers, active element inclusion, extreme power devices used in accelerators), and others, $\ldots$ , because something has to be left for the next paper! The paper does cover bandstop filters, intrinsically switched film bulk acoustic resonator, and barium–strontium–titanate filters, brand new derivations of lossy filter synthesis and dual-band filter synthesis, multimode networks, new work on optimal multiplexer (multiport network) configurations, and substrate integrated waveguide filters. In each of these areas significant new work has been recently performed and is presented in a summary format suitable for those thinking that the area of filters and multiplexers has become mature (stagnant) with nothing interesting to learn. Nothing could be further from the truth!

Electrical delay line multiplexing for pulsed mode radiation detectors

Medical imaging systems are composed of a large number of position sensitive radiation detectors to provide high resolution imaging. For example, whole-body Positron Emission Tomography (PET) systems are typically composed of thousands of scintillation crystal elements, which are coupled to photosensors. Thus, PET systems greatly benefit from methods to reduce the number of data acquisition channels, in order to reduce the system development cost and complexity. In this paper we present an electrical delay line multiplexing scheme that can significantly reduce the number of readout channels, while preserving the signal integrity required for good time resolution performance. We experimented with two 4 × 4 LYSO crystal arrays, with crystal elements having 3 mm × 3 mm × 5 mm and 3 mm × 3 mm × 20 mm dimensions, coupled to 16 Hamamatsu MPPC S10931-050P SiPM elements. Results show that each crystal could be accurately identified, even in the presence of scintillation light sharing and inter-crystal Compton scatter among neighboring crystal elements. The multiplexing configuration degraded the coincidence timing resolution from ∼243 ps FWHM to ∼272 ps FWHM when 16 SiPM signals were combined into a single channel for the 4 × 4 LYSO crystal array with 3 mm × 3 mm × 20 mm crystal element dimensions, in coincidence with a 3 mm × 3 mm × 5 mm LYSO crystal pixel. The method is flexible to allow multiplexing configurations across different block detectors, and is scalable to an entire ring of detectors.