Channel Loss Research Articles

Analog Approximate-FFT 8/16-Beam Algorithms, Architectures and CMOS Circuits for 5G Beamforming MIMO Transceivers

Emerging millimeter-wave (mmW) wireless systems require beamforming and multiple-input multiple-output (MIMO) approaches in order to mitigate path loss, obstructions, and attenuation of the communication channel. Sharp mmW beams are essential for this purpose and must support baseband bandwidths of at least 1 GHz to facilitate higher system capacity. This paper explores a baseband multi-beamforming method based on the spatial Fourier transform. Approximate computing techniques are used to propose a low-complexity fast algorithm with sparse factorizations that neatly map to integer $W/L$ ratios in CMOS current mirrors. The resulting approximate fast Fourier transform (FFT) can thus be efficiently realized using CMOS analog integrated circuits to generate multiple, parallel mmW beams in both transmit and receive modes. The paper proposes both 8- and 16-point approximate-FFT algorithms together with circuit theory and design information for 65-nm CMOS implementations. Post-layout simulations of the 8-point circuit in Cadence Spectre provide well-defined mmW beam shapes, a baseband bandwidth of 2.7 GHz, a power consumption of 70 mW, and a dynamic range >42.2 dB. Preliminary experimental results confirm the basic functionality of the 8-beam circuit. Schematic-level analysis of the 16-beam I/Q version show worst-case and average side lobe levels of −10.2 dB and −12.2 dB at 1 GHz bandwidth, and −9.1 dB and −11.3 dB at 1.5 GHz bandwidth. The proposed multi-beam architectures have the potential to reduce circuit area and power requirements while meeting the bandwidth requirements of emerging 5G baseband systems.

Characterization of the Fat Channel for Intra-Body Communication at R-Band Frequencies.

In this paper, we investigate the use of fat tissue as a communication channel between in-body, implanted devices at R-band frequencies (1.7–2.6 GHz). The proposed fat channel is based on an anatomical model of the human body. We propose a novel probe that is optimized to efficiently radiate the R-band frequencies into the fat tissue. We use our probe to evaluate the path loss of the fat channel by studying the channel transmission coefficient over the R-band frequencies. We conduct extensive simulation studies and validate our results by experimentation on phantom and ex-vivo porcine tissue, with good agreement between simulations and experiments. We demonstrate a performance comparison between the fat channel and similar waveguide structures. Our characterization of the fat channel reveals propagation path loss of ∼0.7 dB and ∼1.9 dB per cm for phantom and ex-vivo porcine tissue, respectively. These results demonstrate that fat tissue can be used as a communication channel for high data rate intra-body networks.

A 12-Gb/s Stacked Dual-Channel Interface for CMOS Image Sensor Systems.

We propose a dual-channel interface architecture that allocates high and low transition-density bit streams to two separate channels. The transmitter utilizes the stacked drivers with charge-recycling to reduce the power consumption. The direct current (DC)-coupled receiver front-end circuits manage the common-mode level variations and compensate for the channel loss. The tracked oversampling clock and data recovery (CDR), which realizes fast lock acquisition below 1 baud period and low logic latency, is shared by the two channels. Fabricated in a 65-nm low-power complementary metal-oxide semiconductor (CMOS) technology, the dual-channel transceiver achieves 12-Gb/s data rate while the transmitter consumes 20.43 mW from a 1.2-V power supply.

Path-loss modelling for WSN deployment in indoor and outdoor environments for medical applications

Wireless sensor networks (WSNs) and their applications have received significantly interested in the last few years. In WSN, knowing an accurate path-loss model as well as packet delivery should be taken into account for the successful distribution of several nodes in the net-work. This paper presents a path-loss modeling and performance evaluation of the ZigBee wireless standard. Received signal strength indi-cator (RSSI) measurements were achieved in outdoor and indoor environments to derive the path-loss based on Log-Normal Shadowing Model (LNSM). The path-loss parameters such as standard deviation and path loss exponents were estimated over point-to-point ZigBee WSN. In addition, the variances of received RSSI values and standard deviation for these values have been investigated. Furthermore, the data packets received is measured practically. Results revealed that the LNSM can be estimated to reflect the channel losses in both outdoor and indoor environments for medical application. The data delivery was achieved successfully of 100% in outdoor which better than indoor due to multipath propagation and shadowing. Moreover, the data packets delivery of the current work outperformed previous work.

Heat transfer and pressure loss in small-scale pillow-plate heat exchangers

In this work, an experimental study of heat transfer between air and water in a small-scale pillow-plate heat exchanger (PPHE) consisting of two pillow plates assembled together in one unit was carried out. In the experiments, cooling water flows in two inner channels (i.e., channels inside welded pillow plates), whereas air is directed to the outer channel between the plates. Heat transfer and hydraulic resistance in inner and outer PPHE channels are analysed based on the experimental data. The measurements were used to develop correlations for the pressure loss and heat transfer coefficients in both inner and outer channels. For the detailed investigation of pressure loss and wall shear stress in the outer channel between pillow plates, CFD simulations were carried out for the considered geometry. The Reynolds number was equal to 5,173, which ensured fully developed turbulent flow. The proposed correlations derived from experimental data were compared with the CFD simulation results. They can be used to predict thermal and hydraulic performance of small-scale PPHEs.

Hopf Bifurcation of the Wireless Network Congestion Model with State-Dependent Round Trip Delay

In this paper, the bifurcation analysis software, DDE-BIFTOOL, is employed to analyze the Hopf bifurcation of the wireless network congestion model with state-dependent round trip delay. Hopf bifurcations are investigated for the four typical work conditions. The corresponding stable and unstable bifurcating periodic solutions are quantitatively and qualitatively verified by nonlinear simulation software, WinPP, respectively, which agree with those of DDE-BIFTOOL very well. The results imply that the channel loss probabilities [Formula: see text] and [Formula: see text] can play a more important role than the speed of the network, i.e. the related link bandwidth [Formula: see text]. For larger [Formula: see text] and [Formula: see text] in Cases 3 and 4, the smaller [Formula: see text] and [Formula: see text] can induce Hopf bifurcation. This will result in the loss of stability and performance degradation. So [Formula: see text] and [Formula: see text] should be set smaller to avoid congestion, providing a sound theoretical basis and instructions for the congestion control of the wireless network.

Composable security analysis of continuous-variable measurement-device-independent quantum key distribution with squeezed states for coherent attacks

Measurement-device-independent quantum key distribution protocol, whose security analysis does not rely on any assumption on the detection system, can immune the attacking against detectors. We give a first composable security analysis for continuous-variable measurement-device-independent quantum key distribution using squeezed states against general coherent attacks. The security analysis is derived based on the entanglement-based scheme considering finite size effect. A version of entropic uncertainty relation is exploited to give a lower bound on the conditional smooth min-entropy by trusting Alice's and Bob's devices. The simulation results indicate that, in the universal composable security framework, the protocol can tolerate 2.5 dB and 6.5 dB channel loss against coherent attacks with direct and reverse reconciliation, respectively.

Silicon-based cyclic arrayed waveguide grating routers with improved loss uniformity

We present silicon-on-insulator (SOI)-based cyclic arrayed waveguide grating routers (AWGRs) with improved channel loss uniformity in the full free spectral range (FSR) by using dual-tapered auxiliary waveguides between the ends of arrayed waveguides. The field distribution at the image plane of the output free propagation region (FPR) is adjusted by the auxiliary waveguides and a flat-top shape can be obtained by appropriate optimization. 8×8 and 15×15 AWGRs with optimized auxiliary waveguides, having a channel spacing of 3.2 nm and 1.6 nm, respectively, are fabricated and the measured loss non-uniformity is less than 0.5 dB, significantly improved by at least 1.5 dB compared with conventional AWGRs.

Functional reorganization of the conceptual brain system after deafness in early childhood.

The neurodevelopmental consequences of deafness on the functional neuroarchitecture of the conceptual system have not been intensively investigated so far. Using functional magnetic resonance imaging (fMRI), we therefore identified brain areas involved in conceptual processing in deaf and hearing participants. Conceptual processing was probed by a pictorial animacy decision task. Furthermore, brain areas sensitive to observing verbal signs and to observing non-verbal visual hand actions were identified in deaf participants. In hearing participants, brain areas responsive to environmental sounds and the observation of visual hand actions were determined. We found a stronger recruitment of superior and middle temporal cortex in deaf compared to hearing participants during animacy decisions. This region, which forms auditory cortex in hearing people according to the sound listening task, was also activated in deaf participants, when they observed sign language, but not when they observed non-verbal hand actions. These results indicate that conceptual processing in deaf people more strongly depends on language representations compared to hearing people. Furthermore, additionally enhanced activation in visual and motor areas of deaf versus hearing participants during animacy decisions and a more frequent report of visual and motor features in the property listing task suggest that the loss of the auditory channel is partially compensated by an increased importance of visual and motor information for constituting object knowledge. Hence, our results indicate that conceptual processing in deaf compared to hearing people is more strongly based on the language system, complemented by an enhanced contribution of the visuo-motor system.

Characterization and Classification of Human Body Channel as a function of Excitation and Termination Modalities.

Human Body Communication (HBC) has recently emerged as an alternative to radio frequency transmission for connecting devices on and in the human body with order(s) of magnitude lower energy. The communication between these devices can give rise to different scenarios, which can be classified as wearable-wearable, wearable-machine, machine-machine interactions. In this paper, for the first time, the human body channel characteristics is measured for a wide range of such possible scenarios (14 vs. a few in previous literature) and classified according to the form-factor of the transmitter and receiver. The effect of excitation/termination configurations on the channel loss is also explored, which helps explain the previously unexplained wide variation in HBC Channel measurements. Measurement results show that wearable-wearable interaction has the maximum loss (upto -50 dB) followed by wearable-machine and machinemachine interaction (min loss of 0.5 dB), primarily due to the small ground size of the wearable devices. Among the excitation configurations, differential excitation is suitable for small channel length whereas single ended is better for longer channel.

Channel Loss in Contactless Human Body Communication.

Human body communication (HBC) utilizes human body as the transmission medium to facilitate data communications in a wireless body area network (WBAN). It normally uses a pair of transmitting (Tx) and receiving (Rx) electrodes clinging to the body surface to form a low-loss body channel, so a higher energy efficiency can be achieved in comparison to conventional wireless communications. In HBC, the Tx electrode can be shared with vital sign monitoring electrode, such as ECG electrode or EEG electrode, to inject the signal into body. As for the Rx electrode, it can be either in direct contact to body surface or placed in proximity to body surface. The late case forms a contactless HBC communication, which find more applications in the WBAN, e.g. a smart phone in one's pocket to receive ECG signal from the chest electrode. In view of the adverse effect caused by the contactless case, this paper presents a study on the path loss of contactless HBC, which are investigated by finite element method (FEM) and verified by actual measurements. An empirical formula for path loss and contactless space is derived, showing that the path loss is increased by 18 dB when the distance between electrode and body increases from 1 mm to 10 mm. It also shows a 5 dB reduction on path loss with a 50% increase of the electrode size.

A Power-Saving Adaptive Equalizer With a Digital-Controlled Self-Slope Detection

When operating at a gigahertz-level frequency, a high-frequency signal is distorted and degraded through the channel. To meet the demand of low cost and the low power consumption for consumer electronic products, this paper proposes a power-saving adaptive equalizer with digital-controlled self-slope detection to compensate channel losses. Reducing and shutting down high-speed circuits in addition to digitization are the most effective methods for minimizing both power and cost. This study also proposes a serial processing for reducing one high-speed detection circuit. The main concept is to use a self-slope detection circuit, which compares two continuous serial slopes, instead of a previous detection circuit, which uses a slicer. After compensation, a shutdown mechanism switches OFF the control circuit to reduce power. A serial processing enables channeling the data through the same circuit and path to avoid swing balancing and mismatch problems. An experimental chip was implemented using 90-nm 1P9M CMOS technology. In the experiment, the equalizer is operated at a supply power of 1 V with 4.35 mW. The core area occupies of $120~\mu \text{m} \times 189~\mu \text{m}$ , and the peak-to-peak jitter measured at 5 Gb/s by using the PRBS31 pattern through a 1.5-m channel is 0.36 UI.

On the Sensitivity of Hillslope Runoff and Channel Transmission Losses in Arid Piedmont Slopes

AbstractChannel transmission losses alter the streamflow response of arid and semiarid watersheds and promote focused groundwater recharge. This process has been primarily studied in dryland channels draining large areas that are displaced away from hillslope runoff generation. In contrast, small watersheds on arid piedmont slopes allow the investigation of interactive hillslope and channel processes that control the partitioning between surface and subsurface flows. In this study, we utilize high‐resolution, long‐term measurements of water balance components in an instrumented watershed of the Chihuahuan Desert to set up, parameterize, and test a process‐based, distributed hydrologic model modified to account for channel losses. A transient method for capturing capillary effects in channels results in simulations with a reliable representation of the watershed energy balance, soil moisture dynamics, hillslope infiltration, channel transmission (or percolation) losses, and streamflow yield over the study period. The simulation also reproduces a conceptual model of hillslope infiltration‐excess runoff generation linked to downstream channel percolation losses that depend on the rainfall event size. Model‐derived thresholds were obtained for the amount of hillslope runoff (6 mm) and rainfall (12.5 mm) necessary for streamflow yield, such that 40% of percolation occurs for small events that do not reach the outlet. Using a set of scenarios, we identify that hillslope infiltration controls the rainfall threshold necessary to initiate percolation, while channel infiltration affects the partitioning into percolation and streamflow yield. Thus, the connectivity along hillslope‐channel pathways is deemed an essential control on the streamflow generation and groundwater recharge in arid regions with complex terrain.

Muscarinic receptor-induced contractions of the detrusor are impaired in TRPC4 deficient mice

Acetylcholine contracts the bladder by binding to muscarinic M3 receptors on the detrusor, leading to Ca2+ influx via voltage-gated Ca2+ channels. The cellular mechanisms linking these events are poorly understood, but studies have suggested that activation of TRPC4 channels could be involved. The purpose of this study was to investigate if spontaneous and cholinergic-mediated contractions of the detrusor were impaired in TRPC4 deficient (TRPC4−/−) mice. Isometric tension recordings were made from strips of wild-type (WT) and TRPC4−/− detrusor. Spontaneous phasic detrusor contractions were significantly smaller in TRPC4−/− mice compared to wild-type, however no difference in response to exogenous application of 60 mM KCl was observed. Cholinergic responses, induced by electric-field stimulation (EFS), bath application of the cholinergic agonist carbachol, or the acetylcholinesterase inhibitor neostigmine were all significantly smaller in TRPC4−/− detrusor strips than wild-type. Surprisingly, the TRPC4/5 inhibitor ML204 reduced EFS and CCh-evoked contractions in TRPC4−/− detrusor strips. However, TRPC5 expression was up-regulated in these preparations and, in contrast to wild-type, EFS responses were reduced in amplitude by the TRPC5 channel inhibitor clemizole hydrochloride. This study demonstrates that TRPC4 channels are involved in spontaneous and cholinergic-mediated contractions of the murine detrusor. TRPC5 expression is up-regulated in TRPC4−/− detrusor strips, and may partially compensate for loss of TRPC4 channels.

Aerodynamics and Heat Transfer over Solid-Deflectors in Transverse, Staggered, Corrugated-Upstream and Corrugated-Downstream Patterns

Computational fluid dynamic simulations were conducted to analysis the influences of two different deflector orientations on turbulent forced-convection flow and skin friction loss of two-dimensional horizontal rectangular cross section channels with upper and lower wall-attached corrugated baffles. The governing flow equations, i.e., continuity, momentum, and energy, were numerically solved by the Finite Volume Method (FVM) using the Semi-Implicit Method for Pressure Linked Equation (SIMPLE) discretization formulation. The help of the CFD code FLUENT was employed to solve the dynamic and thermal behavior of air in the whole domain under investigation. The flow rate in terms of Reynolds number is ranged from 5,000 to 32,000. The obtained results show that augmenting the Reynolds number makes the dynamic thermo energy field redirect in the vicinity of deflector corners, and forces an augmentation in the thermal transfer rate from baffles.

40 Gbps 4‐level pulse amplitude modulation closed‐loop decision‐feedback equaliser with high‐speed comparator in 55 nm CMOS technology

A 40 Gbps 4-tap 4-level pulse amplitude modulation closed-loop decision feedback equaliser (DFE) is proposed. The DFE adopts a novel high-speed comparator to resolve the critical timing constraints of the first tap. The comparator decreases the slicing delay by shortening the gap between initial and target voltages. Compared with the existing closed-loop DFE designs, the proposed scheme relieves timing constraints without complex clock distribution circuits and extra area. Simulations based on the RF-MOS model verify that the delay of the comparator is improved by 32.8% and the output swing is increased by more than 2.8 times. The proposed DFE which can compensate −9.5 dB channel loss is designed in 55 nm CMOS technology. The power consumption is 67 mW from a 1.2 V supply and the circuit occupies an active area of 0.021 mm2, achieving 1.68 pJ/bit energy efficiency.

A Passive Equalizer Optimization Method Based on Time-Domain Inter-Symbol Interference (ISI) Cancellation Technique

In this letter, a channel loss equalization method based on a time-domain inter-symbol interference (ISI) cancellation technique for passive interconnects is proposed. The proposed method can be applied to conventional passive equalizer designs that intentionally suppress the low-frequency and dc components of passive channel responses to compensate for the frequency-dependent losses. An R–L passive equalizer design composed of surface mount inductors and a resistor was employed for validation of the proposed method. With the proposed channel equalization method, it was demonstrated that the ISIs were successfully removed with a significantly improved eye-opening and timing margin.

Optical circulation in a multimode optomechanical resonator

Breaking the symmetry of electromagnetic wave propagation enables important technological functionality. In particular, circulators are nonreciprocal components that can route photons directionally in classical or quantum photonic circuits and offer prospects for fundamental research on electromagnetic transport. Developing highly efficient circulators thus presents an important challenge, especially to realise compact reconfigurable implementations that do not rely on magnetic fields to break reciprocity. We demonstrate optical circulation utilising radiation pressure interactions in an on-chip multimode optomechanical system. Mechanically mediated optical mode conversion in a silica microtoroid provides a synthetic gauge bias for light, enabling four-port circulation that exploits tailored interference between appropriate light paths. We identify two sideband conditions under which ideal circulation is approached. This allows to experimentally demonstrate ~10 dB isolation and <3 dB insertion loss in all relevant channels. We show the possibility of actively controlling the circulator properties, enabling ideal opportunities for reconfigurable integrated nanophotonic circuits.

Hybrid Precoder and Combiner Design With Low-Resolution Phase Shifters in mmWave MIMO Systems

Millimeter wave (mmWave) communications have been considered as a key technology for next generation cellular systems and Wi-Fi networks because of its advances in providing orders-of-magnitude wider bandwidth than current wireless networks. Economical and energy efficient analog/digial hybrid precoding and combining transceivers have been often proposed for mmWave massive multiple-input multiple-output (MIMO) systems to overcome the severe propagation loss of mmWave channels. One major shortcoming of existing solutions lies in the assumption of infinite or high-resolution phase shifters (PSs) to realize the analog beamformers. However, low-resolution PSs are typically adopted in practice to reduce the hardware cost and power consumption. Motivated by this fact, in this paper, we investigate the practical design of hybrid precoders and combiners with low-resolution PSs in mmWave MIMO systems. In particular, we propose an iterative algorithm which successively designs the low-resolution analog precoder and combiner pair for each data stream, aiming at conditionally maximizing the spectral efficiency. Then, the digital precoder and combiner are computed based on the obtained effective baseband channel to further enhance the spectral efficiency. In an effort to achieve an even more hardware-efficient large antenna array, we also investigate the design of hybrid beamformers with one-bit resolution (binary) PSs, and present a novel binary analog precoder and combiner optimization algorithm with quadratic complexity in the number of antennas. The proposed low-resolution hybrid beamforming design is further extended to multiuser MIMO communication systems. Simulation results demonstrate the performance advantages of the proposed algorithms compared to existing low-resolution hybrid beamforming designs, particularly for the one-bit resolution PS scenario.

0.5–4.4 Gbit/s PAM4/NRZ dual‐mode transceiver with 0.6 V near‐ground NMOS driver for low‐power memory interface

An efficient dual-mode input and output transceiver scheme is proposed. The transceiver can achieve the data speed from 0.5 up to 4.4 Gbit/s with 0.6 V supply voltage and can support the near-ground mode for low-power memory interface application. The transceiver can transmit both PAM4/NRZ signals flexibly depending on the channel loss conditions. The prototype bi-directional two-channel transceiver is implemented in 45 nm CMOS process and occupies 0.0516 mm2 chip area. The IP shows power consumption of 2.24/2.78 mW during 4.4 Gbit/s PAM4/NRZ mode operation, each, respectively.