Impact of Equalizer-Enhanced Phase Noise for Coherent Plug-gables

Aero-engine icing, which occurs due to the impingement and subsequent freezing of airborne, super-cooled water droplets in clouds on the exposed surfaces of aero-engine inlet components, such as fan blades and inlet guide vane (IGV), has been widely recognized as a significant hazard to aviation safety in cold weathers. Typical glaze and rime icing process on such aero-engine components would fast change the surface roughness and even the designed geometry, which would degrade the performance of the jet engine and even jeopardize the engine stability. In addition, the potential shedding of large ice chunk would also be a threat to downstream components when be sucked into the core component, for example, the high-pressure compressor. Such impinged ice chunk would significantly distort the incoming flow condition and even cause the blades mechanical vibration. Therefore, the ice accretion process is considered to be one of the most hazardous icing incidents due to the potentially fatal penalties of the surge, stall, and even flameout of aero-engines. By leveraging the Icing Research Tunnel of Iowa State University (ISU-IRT in short), a series of experimental campaigns were conducted to investigate the dynamic icing process over the rotating engine fan and static inlet guide vane model. While different anti-/de-icing strategies were also applied to achieve ice mitigation for the aero-engine rotor and the stator. Firstly, the dynamic icing process of the aero-engine fan was studied using the high-speed imaging system and the digital image projection (DIP) based 3D scanning system, to reveal and quantify the transient ice accretion process over the rotation engine fan model and its performance degradation. Then, three anti-icing coatings, based on different working mechanisms, were also applied to the aero-engine fan model to study the surface wettability effect on the dynamic icing process and to achieve ice mitigation. For the IGV icing and anti-/de-icing study, an experimental campaign was conducted to investigate the IGV icing process under both wet glaze and dry rime icing conditions. While a parametric study was also conducted to study each operating parameter of the hot-air anti-/de-icing system on its anti-/de-icing performance. Finally, a theoretical heat transfer model based on mass and energy conservation was built to study the energy budget during the icing and anti-/de-icing process. During the experiment, an infrared (IR) imaging system, combined with thermocouples and heat flux sensors, was then applied to quantify the energy stored in the control volume and dissipated to the surrounding environment, which would be used to explain the phenomena related to the icing and anti-/de-icing process. The results from this paper would provide a better understanding of the aero-engine components icing physics pertinent to both jet engine rotor and stator. While the explorative study of each anti-/de-icing strategy also helps the design of more effective and robust anti-/de-icing strategies tailored for aero-engine fan and the IGV. Such improvement would fulfill the fast raised standard of the modern aviation industry for a high efficiency and safety aero-engine even operating in cold weather.

Since Bluetooth and wireless local area network (WLAN) technologies both operate at the 2.4-GHz industrial, scientific, and medical (ISM) band, the two types of devices may suffer from mutual interference and performance degradations. In this paper, we propose two new techniques, channel clustering and probabilistic channel visiting, to effectively improve the existing coexistence and interference mitigation mechanisms. The channel clustering technique employs statistical pattern recognition to classify the status of Bluetooth channels more accurately. The probabilistic channel visiting is used to more equitably allocate the channel resources between Bluetooth and WLAN devices. The effectiveness of these techniques is quantified by simulations. Results show that both techniques are beneficial in improving the performance of the existing mechanisms.

The deployment of long term evolution (LTE) in the unlicensed spectrum (LTE-U) has been gaining significant industry momentum in recent months. The US 5-GHz Unlicensed National Information Infrastructure (UNII) bands that are currently under consideration for LTE deployment in the unlicensed spectrum contain only a limited number of 20 MHZ channels. Thus, in a dense multi-operator deployment scenario, one or more LTE-U small cells have to coexist and share the same 20 MHz unlicensed channel with each other and with the incumbent Wi-Fi. In this paper, we present the scenario and demonstrate that in the absence of an explicit interference mitigation mechanism, there will be a significant degradation in the overall LTE-U system performance for LTE-U cochannel coexistence in countries that do not mandate listen-before-talk (LBT) requirements. We then present the unlicensed spectrum intercell interference co-ordination (usICIC) mechanism as a time-domain multiplexing technique for interference mitigation for the sharing of an unlicensed channel by multioperator LTE-U small cells. Through extensive simulation results, we also demonstrate that our proposed usICIC mechanism will result in 40% or more improvement in overall LTE-U system performance.

A severe spectrum shortage for wireless communication systems poses the spectrum overlapping and the interference problem with a significant performance degradation. To avoid this problem, it is essential to employ the techniques for interference mitigation. The goal of this paper is to investigate the performance of some interference mitigation techniques in the systems using Viterbi decoding, i.e., 1-norm metric, received power based limiting, puncturing and metric based limiting. These methods are compared from the view point of bit error rate (BER) obtained by computer simulations. Simulation results show the superiority of metric based limiting, which yields better BER performance.

Continuous and precise code delay tracking is essential in challenging environments such as urban canyons where multipath and frequent signal blockage may lead to performance degradation and loss of lock of signals. The strobe correlator (SC) is an effective technique for baseband multipath mitigation and is commonly used for GNSS signal tracking enhancement. An SC has two pairs of early and late correlators, one with a wide and another with a narrow correlator spacing. This paper extends the conventional SC design by applying its correlator pairs on dual-band GNSS signals to realize an extended strobe correlator (ESC). An ESC takes advantage of the natural distinct bandwidth of narrow-band and wide-band signals, e.g., L1 C/A and L5Q signals, to form a dual-band combination at the correlator level in a deeply-coupled manner. Narrow-band L1 signal tracking ensures robustness, while the wide-band L5 signal improves the tracking precision. A moving average window filters the L1 measurement to prevent the noise impact on L5 tracking, providing necessary inter-band assistance to resolve challenges such as code delay misalignment and precision mismatch. Through both Monte Carlo simulation and real data collected in urban environments, this work demonstrates that an ESC can achieve improved overall robustness against loss-of-lock and multipath mitigation performance over standalone tracking. Compared with KF-based combined (KFC-based) tracking, ESC has higher tracking precision under weak signal environment and robustness during signal blockage, but larger residual multipath error.

An important problem in satellite communication systems which operate in the Ka and EHF frequency bands consists of the degradation in link performance of mobile terminals due to blockage of the link to the satellite, especially in urban environments. In this paper, we focus on the hard and soft link blockage problem, and we provide a very efficient and cost effective solution via the use of fountain codes. We first introduce a hard-blockage channel model based on a composite Poisson process, which yields an excellent match to actual measured data. The soft-blockage is essentially due to signal shadowing, and we model this channel by means of the generalized Nakagami-m distribution with the parameter m in the range m = 4, or 5. This model approximates well the measured data, and it can be used as a more tractable alternative to the traditional lognormal distribution, and it has been used extensively in terrestrial wireless systems. The advantage of this model is that it covers a wide range of channel conditions that lead to shadowing, ranging from shallow to relatively deep shadowing/fading. We then consider the use of fountain codes, with focus on Raptor codes, as our main mitigation technique to combat the degradation in link performance due to hard- or soft-blockage. The performance of the receiver is obtained in terms of average probability of bit and message error as a function of bit energy-to-noise density ratio, Eb=No, and other parameters of interest, via a combination of analysis and computer simulations, and we show that the use of fountain codes is extremely effective in overcoming the effects of hard- and soft-link blockage.

Aging of transistors is a limiting factor for long term reliability of devices in sub-100nm technologies. It's a worst-case metric where the lifetime of a device is determined by the earliest failing component. Impact is more serious on memory arrays, where failure of a single SRAM cell would cause the failure of the whole system. Previous works have shown that partitioning based strategies based on power management techniques can effectively control aging effects and can extend lifetime of the cache significantly. However, such a benefit comes as a trade-off with performance which reduces proportionally as the time elapses. To address this problem and provide a single solution to concurrently improve aging, energy and performance of the cache, we propose an architectural solution based on the dynamically re-sizable cache [5] and cache partitioning approaches. By this strategy, cache is dynamically re-sized and reconfigured whenever a cache block becomes unreliable. Coupling such aging mitigation technique along with dynamically re-sizable cache approach provides on average 30% lifetime improvement with less than 0.4x degradation in performance whereas, in previous solutions, performance degradation sometimes goes upto 10x.

As the size of data increases and computation becomes complicated in fog computing environments, the need for highperformance computation is increasing. One of the most popular ways to improve the performance of a virtual machine (VM) is to allocate a graphic processing unit (GPU) to the VM for supporting general purpose computing on graphic processing unit (GPGPU) operations. The direct pass-through, often used for GPUs in VMs, is popular in the cloud because VMs can use the full functionality of the GPU and experience virtually no performance degradation owing to virtualization. Direct pass-through is very useful for improving the performance of VMs. However, since the GPU usage time is not considered in the VM scheduler that operates based on the central processing unit (CPU) usage time of the VM, the VM performing the GPGPU operation degrades the performance of other VMs. In this paper, we analyze the effect of the VM performing the GPGPU operation (GPGPU-intensive VM) on other VMs through experiments. Then, we propose a method to mitigate the performance degradation of other VMs by dynamically allocating the resource usage time of the VM and preventing the priority preemption of the GPGPU-intensive VM.

Background: With the advancement of Industry 4.0, the automation of industrial processes has shifted from wired communication technologies to wireless networks, enabling greater flexibility, efficiency, and scalability. Technologies such as LoRaWAN and NB-IoT have been widely adopted due to their low energy consumption and long-range communication capabilities, which are essential for industrial applications. However, the increasing density of connected devices has introduced new challenges, particularly related to electromagnetic interference (EMI), which can degrade network performance, cause packet loss, and delay communication. EMI, caused by various sources such as electronic devices and natural phenomena, is a critical issue in industrial environments. EMI simulations and analyses allow for network parameter adjustments and the implementation of mitigation techniques, ensuring robust communications. This study's primary objective is to test the radiated electromagnetic immunity of the LoRa protocol, assessing its ability to operate in environments subject to electromagnetic interference. The research emphasizes the importance of understanding EMI impacts to preserve data accuracy, improve communication performance, and ensure regulatory compliance, fostering a safe, reliable, and efficient industrial environment. Materials and Methods: The study evaluates the radiated electromagnetic immunity of Heltec LoRa ESP32 V2 boards, essential for IoT applications, in compliance with the IEC 61000-4-3 standard, which establishes methods for testing immunity to high-frequency electromagnetic fields. The boards were tested in an anechoic chamber to analyze the impact of radiated fields on LoRa communication. During the tests, conducted at frequencies from 80 MHz to 6 GHz and with a field intensity of 10 V/m, a transmitting board continuously sent LoRa packets while the receiving board recorded RSSI values and packet reception rates. The results demonstrated the sensitivity of the LoRa protocol to electromagnetic interference, evidenced by RSSI variations and packet losses under certain conditions. The tests highlighted the importance of robust configurations to maintain data integrity and device functionality in challenging industrial environments. The study provides valuable insights for improving electromagnetic compatibility in Industry 4.0 and IoT applications, meeting the criteria established by the IEC 61000-4-3 standard. Results: The study identified critical communication disruptions in the LoRa system at specific frequencies (305 MHz and 730 MHz) under radiated electromagnetic fields with a power of 1.5 dBm, characterized by packet loss and performance degradation. At 3 dBm, total communication failure occurred, attributed to internal resonances in the RF components and insufficient shielding or filtering of the modules. The interference likely overlapped with harmonics of the LoRa signal, reducing its ability to distinguish useful signals from noise. These findings highlight the system's vulnerability to specific EMI conditions, emphasizing the need for improved filtering, shielding, and protocol adjustments to enhance robustness in industrial environments. Conclusion: The study finds LoRa unstable at 305 MHz and 705 MHz with 1.5 dBm, causing packet loss and potential communication failure, highlighting the need for mitigation in high-interference environments.

Side-channel attacks have recently progressed into software-induced attacks. In particular, a rowhammer attack, which exploits the characteristics of dynamic random access memory (DRAM), can quickly and continuously access the cells as the cell density of DRAM increases, thereby generating a disturbance error affecting the neighboring cells, resulting in bit flips. Although a rowhammer attack is a highly sophisticated attack in which disturbance errors are deliberately generated into data bits, it has been reported that it can be exploited on various platforms such as mobile devices, web browsers, and virtual machines. Furthermore, there have been studies on bypassing the defense measures of DRAM manufacturers and the like to respond to rowhammer attacks. A rowhammer attack can control user access and compromise the integrity of sensitive data with attacks such as a privilege escalation and an alteration of the encryption keys. In an attempt to mitigate a rowhammer attack, various hardware- and software-based mitigation techniques are being studied, but there are limitations in that the research methods do not detect the rowhammer attack in advance, causing overhead or degradation of the system performance. Therefore, in this study, a rowhammer attack detection technique is proposed by extracting common features of rowhammer attack files through a static analysis of rowhammer attack codes.

The 5.9 GHz spectrum band is proposed for vehicular communications using Dedicated Short Range Communications (DSRC), but this band may need to be shared with unlicensed Wi-Fi devices. A recent Federal Communications Commission (FCC)’s Notice of Proposed Rulemaking (NPRM) outlines two interference mitigation techniques for spectrum coexistence: Detect and Vacate and Re-channelization. A major technical challenge of Re-channelization is that DSRC may experience harmful or a reduced functionality because of adjacent channel interference from Wi-Fi transmitters. We therefore conducted Wi-Fi/DSRC adjacent channel interference experiments to evaluate the significance of Wi-Fi signals adjacent to DSRC transmissions. Our measurements show a significant degradation of DSRC performance from 802.11ac adjacent channel interference only for certain scenarios where the distances between the Wi-Fi transmitter to DSRC receiver is 15 m or below and the distances between the DSRC transmitter to receiver is 300m or higher. However, there is no severe effect when the DSRC transmit power is at the standard 33 dBm level, even considering the recommended fading margin of 5-10 dB.

It is well known that the presence of unintentional or intentional Radio Frequency Interference (RFI) signals in the Global Navigation Satellite Systems (GNSS) frequency bands can cause severe positioning performance degradation and even a complete service unavailability. Moreover, with the development of Software Defined Radio (SDR) GNSS signal generators and the popularization of low-cost SDR front-ends, the spoofing of the GNSS civil service turns out to be a real threat for GNSS receivers. Complementary to time and frequency-domain mit-igation techniques, antenna-array based receivers can benefit from spatial domain processing. An antenna array receiver can also discriminate between legitimate GNSS signals from these being broadcasted by the spoofer. In this work, we present an evolution of a receiver-independent GNSS smart antenna architecture for a real-time, automatic and autonomous, simultaneous anti-jamming and anti-spoofing spatial filtering for GNSS bands. The novel spoofer detection and mitigation algorithm is able to detect the spoofer and protect the receiver even in a scenario where the spoofer is transmitted in combination with a strong jammer to force the receiver to lose the legitimate GNSS signal lock. A prototype is also presented, implemented using Commercial Off The Shelf (COTS) components. The proposed smart antenna can be connected to any conventional single-antenna GNSS receiver. The paper includes both the theory of operation, the implementation details and its performance analysis in an extended measurement campaign.

Wireless in-vehicle networks are considered as a flexible and cost-efficient solution for the new generation of cars. One of the candidate wireless technologies for these wireless sensor networks is the IEEE 802.15.4 standard which operates in the 2.4 GHz ISM band. This is while the number of wireless devices that operate in this band is ever increasing. This broad usage of the same RF band may cause considerable performance degradation of wireless networks due to interference. There is some work on the coexistence of the IEEE 802.15.4 protocol and other standard technologies such as IEEE 802.11 (Wi-Fi) and IEEE 802.15.1 (Bluetooth), but none of it considers the highly dynamic conditions of in-vehicle networks. In this paper, we investigate the interference behavior in in-vehicle environments using real-world experiments. We consider different scenarios and measure the interference on all the 16 channels of IEEE 802.15.4 in the 2.4 GHz band.The measurement data set is available to the public. This real-world data set can be used for realistic and accurate network simulation. To study the effect of interference on in-vehicle networks, we use this data set to evaluate the performance of an IEEE 802.15.4e TSCH link. The simulation results show that the packet error rate for some interference scenarios is considerably high and dynamic over time. This shows the value of the data set and reveals the importance of using adaptive interference mitigation techniques to improve the reliability of wireless in-vehicle networks.

Distributed controls have promising applications that include both highly fault-tolerant motor drives and modular drivesfor large machines. Communications speed limitations of these drive systems require each modular sub-drive to operate nearly independently over short timescales. As a result, sensor errors and system unbalances that cause only minor performance degradation in conventional drive systems can lead to complete loss of function in modular drives with distributed control architectures. This paper investigates alternative techniques such as calibration function compensation that can be applied to mitigate these challenges, making it possible for modular drives with weakly-coupled distributed controllers to deliver high-performance motor control. Simulation results are used to evaluate theeffectiveness of the proposed control techniques for addressing the special challenges posed by these distributed control architectures.

Multi-user multiple-input multiple-output (MU-MIMO) systems in the indoor visible light communication (VLC) have attracted significant attention due to the use of the lighting-emitting diodes (LEDs) for illumination and communication. However, they experience performance degradation due to interference from multiple users and low modulation bandwidth requiring the development of mitigation techniques. This work proposes a joint transceiver design using the minimum mean square error (MMSE) to minimize interference for the VLC systems. The mean square error (MSE) is minimised assuming perfect channel state information (CSI) to suppress the interference. The developed results show the proposed transceiver design providing fair data transmission and improving the bit error rate (BER) over the zero-forcing (ZF) scheme. Moreover, the proposed transceiver design shows better convergence than the ZF scheme.