Guard Band Research Articles

Enhancing flexibility and system performance in 6G and beyond: A user-based numerology and waveform approach

A Mixed Numerology OFDM (MN-OFDM) system is essential in 6G and beyond. However, it encounters challenges due to Inter-Numerology Interference (INI). The upcoming 6G technology aims to support innovative applications with high data rates, low latency, and reliability. Therefore, effective handling of INI is crucial to meet the diverse requirements of these applications. To address INI in MN-OFDM systems, this paper proposes a User-Based Numerology and Waveform (UBNW) approach that uses various OFDM-based waveforms and their parameters to mitigate INI. By assigning a specific waveform and numerology to each user, UBNW mitigates INI, optimizes service characteristics, and addresses user demands efficiently. Guard Band (GB) requirements, expressed as a ratio of user bandwidth, vary significantly across different waveforms at an SIR of 25 dB. For instance, OFDM-FOFDM needs only 2.5%, while OFDM-UFMC, OFDM-WOLA, and conventional OFDM require 7.5%, 24%, and 40%, respectively. The time-frequency efficiency also varies between the waveforms. FOFDM achieves 85.6%, UFMC achieves 81.6%, WOLA achieves 70.7%, and conventional OFDM achieves 66.8%. The simulation results demonstrate that the UBNW approach not only effectively mitigates INI but also enhances system flexibility and time-frequency efficiency, while simultaneously reducing the required GB.

Guard Band Protection Scheme to Facilitate Coexistence of 5G Base Stations and Radar Altimeters

Reformation of the 3.7–4.0 GHz band to expand 5G communication deployment poses a risk of 5G signals disrupting radar altimeter operation, leading to data loss or inaccuracies. Thus, this paper proposes a guard band protection method to facilitate the coexistence of 5G base stations and radar altimeters operating in the 4.2–4.4 GHz band. To enhance the adjacent channel leakage ratio (ACLR), we implemented spectral regrowth on an oversampled waveform using a high-power amplifier model, filtering out-of-band spectral emissions. The results demonstrated that a 150 MHz guard band enables coexistence, except in the case of the 16-by-16 antenna array in rural environments. Notably, for the 4-by-4 antenna array in urban environments, coexistence can be achieved using a 50 MHz guard band. The proposed mitigation techniques may also be extended to promote coexistence between non-terrestrial networks and 5G communication systems, including satellites, unmanned aerial vehicles, and hot air balloons.

Symmetry-free routing and spectrum assignment: a universal algorithm based on first-fit

First-fit (FF) is a well-known and widely deployed algorithm for spectrum assignment (SA), but until our recent study [J. Opt. Commun. Netw. 14, 165 (2022)JOCNBB1943-062010.1364/JOCN.445492], investigations of the algorithm had been experimental in nature and no formal properties of the algorithm with respect to SA were known. In this work, we make two contributions. First, we show that FF is a universal algorithm for the SA problem in the sense that, for any variant, 1) it can be used to construct solutions equivalent to, or better than, any solution obtained by any other algorithm, and 2) it can construct an optimal solution. This universality property applies to both the min-max and min-frag objectives and to variants of the SA problem with or without guard band constraints. Consequently, the spectrum symmetry-free model of our recent study [J. Opt. Commun. Netw. 14, 165 (2022)JOCNBB1943-062010.1364/JOCN.445492] extends to all known SA variants, which therefore reduce to permutation problems. Second, we extend the spectrum symmetry-free model to the routing and spectrum assignment (RSA) problem in general topologies. This model allows for the design of more efficient algorithms as it eliminates from consideration an exponential number of equivalent symmetric solutions. By sidestepping symmetry, the RSA solution space is naturally and optimally decomposed into a routing space and a connection permutation space. Building upon this property, we introduce a two-parameter, symmetry-free universal algorithm that can be used to tackle any RSA variant in a uniform manner. The algorithm is amenable to multi-threaded execution to speed up the search process, and the value of the parameters can be adjusted to strike a balance between running time and solution quality. Our evaluation provides insight into the relative benefits of path diversity (which determines the size of the routing space) and connection diversity (which determines the size of the permutation space).

Conformity assessment of a proficiency test using turbine flowmeters based on the concept of tolerance intervals

A proficiency test determines either conformity or non-conformity states by evaluating the normalized degree of equivalence, EN, among laboratories participating in the test. Concern is paid to the results if EN indicates a boundary between conformity and non-conformity states. Either “concerning” or “warning” can urge the participating laboratories to correct their measurement standards with their measured results. This study investigates how to determine guard bands, i.e., the boundary between conformity and non-conformity, based on the normalized degree of equivalence. Two types of guard bands are demarcated at the center of the boundary of the acceptance interval. 1≤EN≤1.2 is set as a guard band to provide “warning” to a participating laboratory considering producer risks, 0.8≤EN≤1 is set as another guard band to express “concerning” to the participating laboratory considering consumer risks. A proficiency test using turbine flowmeters with temperature correction is conducted to confirm the feasibility of these guard bands.

On the trade‐off between rate and reliability for secret key generation in wireless channels

AbstractWireless propagation channels can be used to obtain secret keys to enhance security. By exploiting the reciprocity of the channel between legitimate users and its independence of an eavesdropper's channel, it can be quantised to produce a string of bits. The quality of these bits can be enhanced by using guard bands when quantising, which means that some samples are not used due to their poor quality. Although this increases the probability that the legitimate users produce the same bits, it also reduces the number of generated bits. We derive the optimal trade‐off between these contrasting quantities, first for a single sample and then extended to a frequency‐selective channel. The results are presented for both software simulations and hardware evaluations.

Carrier-assisted differential detection receiver with low carrier-to-signal power ratio employing parallel multi delay

We propose a parallel multi delay (PMD) carrier-assisted differential detection (CADD) receiver for the first time, including PMD asymmetric-CADD (PMD A-CADD) and PMD symmetric-CADD (PMD S-CADD). The transfer function of the PMD CADD receiver is optimized by expanding the number of optical delays to a general selection, thereby suppressing the signal-signal beat interference (SSBI). As a result, the required carrier-to-signal power ratio (CSPR) is reduced, and the optical signal-to-noise ratio (OSNR) sensitivity is drastically improved. Two schemes for further mitigation of residual SSBI are introduced, namely SSBI iterative cancellation algorithm and the increased guard band mitigation method. For SSBI iterative cancellation algorithm, by optimizing the number of optical delays, the optimal CSPR for the P6D A-CADD and the P5D S-CADD can be reduced to −1 dB, the required number of iterations is only 3, and compared with the parallel dual delay-based asymmetric-CADD (PDD A-CADD) receiver, the OSNR sensitivity is improved by about 4.5 dB. For the increased guard band mitigation method, 2.34 GHz and 3.16 GHz guard band are required for the P6D A-CADD and the P5D S-CADD to meet the 7% FEC threshold at 0 dB CSPR.

Mobile fronthaul solution based on visible light fiber communication and zero-padding 8-D CAP modulation.

With the deployment of the fifth-generation (5 G) emerging technologies, such as massive multiple-input multiple-output (mMIMO), conventional mobile fronthaul (FH) schemes based on Common Public Radio Interface (CPRI) are limited in their abilities to support ultra-high data rate, large bandwidth and massive connectivity. This has led to a growing demand for alternative solutions that can better fulfill these requirements. Visible light communication (VLC) has recently gained increasing research interest as a potential complementary technology for beyond-5 G communication, offering advantages such as unlicensed and abundant spectrum, high bandwidth and cost-efficiency. In this paper, we propose a novel mobile fronthaul solution based on visible light fiber communication (VLFC), incorporating innovative zero-padding N-D (N>2) carrierless amplitude and phase (CAP) modulation. To avoid strong low-frequency noise (LFN) in the practical VLFC system, we innovatively propose zero-padding N-D CAP based on the actual distribution of LFN for the first time. In contrast to frequency division multiplexing (FDM), N-D CAP eliminates guard bands and ensures similar performance among multiple channels. To prove the concept, we demonstrate the transmission of PAM8 symbols at three typical visible light wavelengths (R/G/B) over 100 m multi-mode fiber (MMF) using zero-padding 8-D CAP modulation. The experiment verifies that zero-padding significantly enhances communication performance, with all 8 channels achieving similar BER. Communication performance improves as wavelengths are longer due to attenuation and dispersion caused by MMF. Finally, we have achieved a total data rate of 10.8Gbps at 635 nm (red), 9.0Gbps at 520 nm (green), and 7.5Gbps at 488 nm (blue) under the 7% HD-FEC threshold.

A new practical physical layer secret key generation in the presence of an untrusted relay

Physical layer secret key generation (SKG) has recently been introduced as a lightweight and efficient solution for sixth-generation (6G) networks. In this area, schemes based on local random generators are used for high-rate key generation. One of these schemes is random phase injection, where channel probe signals with random phases are exchanged between communication parties (source and destination). This paper proposes an SKG scheme in the presence of an untrusted relay, which helps the SKG process while cannot extract the secret key. To make the scheme operational, for the first time, the channel probe signals are considered discrete random phase based on M-PSK signals and a multi-bit quantizer is used in the reception. In addition, to reduce the key error rate, quantization with guard bands (GB) is used for key extraction. For such a scenario, we derive expressions for key agreement rate, key mismatch rate (KMR), key discarding rate (KDR) and key generation rate (KGR). Additionally, for the first time, this work examines the context of geometric secrecy for the proposed discrete phase key generation scheme for both direct and relaying scenarios. Through simulations, several engineering insights are presented to enhance the quality of the proposed SKG and its security.

Orthogonal-Frequency Simultaneous Wireless Power and Data Transfer for High-Power Wireless EV Charging

In a simultaneous wireless power and data transfer (SWPDT) system using common coils, achieving high-speed communication in high-power wireless charging systems is challenging due to power transfer interference on communication. Based on high-frequency data carrier-based SWPDT (HFDC-SWPDT) technology, this paper proposes an orthogonal-frequency simultaneous wireless power and data transfer (OF-SWPDT) method to minimize interference where the data carrier frequency is orthogonal to the power carrier frequency and its harmonics. In addition, a guard band is inserted between the spectra of power harmonics and data in order to further separate the power and data spectra. Thus, a high-power, high-speed SWPDT system is achieved. Finally, an 11 kW prototype with 64.125 kbps full-duplex communication is developed to validate the proposed method.

Risk Assessment for Linear Regression Models in Metrology

The conformity assessment of products or a measured value with the given standards is carried out based on the global risk of producers and consumers’ calculations. A product may conform to specifications but be falsely rejected as non-conforming. This is about the producer’s risk. If a product does not meet the requirements but is falsely accepted as conforming, that poses a risk to the consumer. The conventional approach to risk assessment, which yields only a single numerical value for the global risk of producers and consumers, is naturally extended and utilized for assessing risk in measurement models with linear regression. The outcomes of the two-dimensional extension, along a moderate scale, are the parabolas with upwards openings. Risk surfaces were obtained through three-dimensional extension over the area limited by the moderate scale and guard band axes. Four models with different ranges of tolerance intervals were used to test this innovative method of risk assessment in linear regression. The corresponding standard measurement uncertainties were determined by applying a simplified measurement model with the use of comprehensive data on the measurement performance and by determining measurement uncertainty derived from consideration of the functional relationship obtained by linear regression analysis. Models that utilize information from linear regression analysis to determine measurement uncertainty are biased towards risks at the edges of the moderate scale. Testing the model’s performances with metrics related to the confusion matrix, such as the F1 score, further substantiated this assertion. The diagnostic odds ratio has been proven to be extremely effective in identifying the curve along the guard band axis, along which the global risks of producers and consumers are at their lowest.

Design and implementation of a frame preemption model without guard bands for time-sensitive networking

In time-sensitive networks, the frames of time-triggered (TT) flows need to be transmitted in scheduled slots. To avoid the interference of frames from other flows to the frames of the TT flows, guard bands are generally reserved prior to scheduled slots. The time-sensitive networking (TSN) standard, IEEE 802.1Qbu, specifies a frame preemption model that enables frames of TT flows (preemption frames) to preempt frames of other flows (preempted frames). According to this model, preempted frames are divided into fragments that are transmitted in the gaps of preemption frames. Consequently, the IEEE 802.1Qbu model reduces the guard band from the longest Ethernet frame (typically 1518 bytes) to 123 bytes, which improves the bandwidth utilization and delay performance of preempted frames without causing frame disorder. However, in scenarios in which the preempted frame load is heavy, and the length is short, numerous guard bands smaller than 123 bytes are generated. These guard bands prevent the IEEE 802.1Qbu model from transmitting preempted frame fragments, resulting in a considerable decrease in bandwidth utilization. To solve this problem, we propose a novel frame preemption model without guard bands, based on a padding and splicing mechanism. While ensuring that preemption frames are transmitted according to scheduled slots, this model can transmit preempted frames within arbitrary byte gaps based on the schedule without obtaining the length of the preempted frames in advance. We compared the transmission-delay performance of the proposed model with that of the IEEE 802.1Qbu model using a theoretical analysis. The evaluation results obtained from heavily loaded preemption frame scenarios revealed that the proposed model improved link utilization by 32.8% relative to the IEEE 802.1Qbu model and reduced the transmission delay by more than one order of magnitude. Moreover, when the IEEE 802.1Qbu model fails, the proposed model still transmits 60% of preempted frames.

150 Gbps THz Chipscale Topological Photonic Diplexer.

Photonic diplexers are being widely investigated for high data transfer rates in on-chip communication. However, dividing the available spectrum into nonoverlapping multicarrier frequency sub-bands has remained a challenge in designing frequency-selective time-invariant channels. Here, an on-chip topological diplexer is reported exhibiting terahertz frequency band filtering through Klein tunneling of topological edge modes. The silicon topological diplexer chip facilitates two high-speed channels with quadrature amplitude modulation (QAM) over a broad bandwidth of 12.5 GHz each. These channels operate at carrier frequencies of 305 and 321.6 GHz, achieving a combined diplexer capacity of 150 Gbits-1. To ensure minimal interference between adjacent channels, a guard band is implemented. Topologically protected edge modes suppress the frequency selective fading of the broadband signals and hold promise for diverse integrated photonic applications spanning terahertz and telecommunication realms, including the design of lossless topological multiplexers, interconnects, antennas, and modulators for the sixth to X generation (6G to XG) wireless.

Configuration of Guard Band and Offsets in Cyclic Queuing and Forwarding

Configuration of Guard Band and Offsets in Cyclic Queuing and Forwarding

Application of analytical quality by design (AQbD) for stability-indicating method development for quantification of nevirapine and its degradation products

Development of stability-indicating method by liquid chromatography are always a challenge for analytical researchers. A traditional way is by varying one chromatographic parameter at a time assessing the responses from each test. Recent international guidelines encourage the implementation of systematic approaches in analytical development, such as Analytical Quality by Design (AQbD). The aim of this paper was to develop, using the AQbD approach, an efficient and selective stability-indicating method by high performance liquid chromatography for nevirapine and its related substances. The Analytical Target Profile (ATP) and the Critical Method Attributes (CMA) were determined. Through the risk assessment studies, the high-risk analytical conditions were considered as Critical Method Parameters (CMP) and they were screened and optimized by Design of Experiment (DoE). The Method Operable Design Region (MODR) was defined using Monte Carlo Simulation. A control strategy was established by the definition of the system suitability of the analytical procedure. Optimal chromatographic conditions were achieved using an isocratic elution consisting of a mixture of 5 mM ammonium formate buffer pH 5.4/acetonitrile/methanol (60:20:20), with a flow rate of 1.0 mL/min, oven temperature of 30 °C, injection volume of 5 µL and an ACE C18 250 mm x 4,6 mm x 5 µm chromatographic column. Finally, analytical validation and forced degradation studies confirmed the performance of the analytical method. From the estimation of measurement uncertainty, strategies were outlined so that the method is fit for purpose throughout its life cycle. Additionally, guard bands were defined, changing the specification for nevirapine quantification from 90 % to 100 % to the acceptance zone of 92.1–107.9 %. The AQbD method development provided strong justifications for the selection of important parameters for nevirapine method during regulatory filling. Furthermore, with the pass/fail decision rule using guard band, restricted acceptance zones were defined, reducing the risk to the consumer of taking a drug product whose batch was inadequately approved.

Practical, high-speed Gaussian coherent state continuous variable quantum key distribution with real-time parameter monitoring, optimised slicing, and post-processed key distillation

Gaussian coherent state continuous variable quantum key distribution has gained interest owing to its security and compatibility with classical coherent optical fibre networks. For successful system deployment it is necessary to implement practical high speed systems which distil keys efficiently. Here, we demonstrate a Gaussian coherent state continuous variable quantum key distribution system at a 50 MHz symbol rate. Unlike most demonstrations to date which measure excess noise and infer key rates from this, we record signals in real time and distil keys. We also demonstrate, for the first time, slice reconciliation with optimised guard bands to maximise achievable secret key rates. Using this optimisation with multilevel slicing, a record 5 Mb/s secret key rate after a transmission distance of 25 km is achieved. This is a significant improvement on the 3 Mb/s secret key rate which is achieved with single level optimised slice reconciliation.

Applied Cavity Perturbation Used for Frequency Identification of Channel Ports in Manifold-Coupled Multiplexers

We investigate a practical technique for deembedding the channel filter S-parameters of manifold-coupled multiplexers (MUXs), without detaching filters from the manifold. The method is applicable for MUXs with an arbitrary number of channels and can be used for the device regardless of its bandwidth, guard band, or loss of filters. We reconfigure the N-port MUX to two simpler networks cascaded to each other. We assume that the manifold response is unknown and use the idea of applied perturbation on the channel filter, and then by comparing the response of the overall cascaded network, before and after the perturbation, we approximate the channel port response. The technique is useful in fast detecting the unexpectedly detuned channels or likely faults in the device without unnecessary plugging/unplugging; it is also useful in roughly tuning of the channel filers at the early stage of MUX tuning. The technique can be easily traced by the telecommunication community.

Data reconciliation connected to guard bands to set specification limits related to risk assessment for radiopharmaceutical activity

Radiopharmaceuticals have been used to diagnose several diseases, particularly because the procedure is non-invasive. However, it is important that the correct amount of radiopharmaceutical is used to avoid inaccurate diagnostic results and suboptimal therapeutic outcomes. The amount of the radiopharmaceutical is measured when produced (by the supplier) and a second time (by the receiver), before it's use. When measured at the receiver, the result is corrected for its normal radioactivity decay. Even then, it is possible that both measurements should be considered nominal different or even statistically different when compared through various statistical tools. This research combines two innovative techniques in the field of clinical metrology. The first technique is data reconciliation, which not only enhances measurement accuracy but also reduces measurement uncertainty. The second technique involves using uncertainty information to establish specification limits for compliance assessments. In this way, our proposal aimed to minimize the risk of making incorrect decisions regarding the conformity of the concentration of radiopharmaceutical activity, that is, rejecting an item or batch that is within specification or accepting an item or batch that is outside of specification. A spreadsheet, based on these metrology fundamentals, is available to help the user with the calculations, presenting numerical and graphical results for some common radioisotopes. Reliable specification limits can be calculated and used to determine if the radiopharmaceutical is in accordance with its proposed application.

Anti-crosstalk absolute phase retrieval method for microscopic fringe projection profilometry using temporal frequency-division multiplexing.

In microscopic fringe projection profilometry (MFPP), the traditional absolute phase retrieval method using composite frequency fringe has the shortcomings of low accuracy and poor robustness due to mutual crosstalk of harmonic from the different channels of frequency-division multiplexing. In this study, an absolute phase retrieval method that avoids the inter-channel crosstalk is proposed. By introducing guard bands to accommodate the frequency channels corresponding to the second harmonic that dominate the high order harmonics, the aliasing between the second harmonic and the fundamental is eliminated. Consequently, phase maps without crosstalk can be demodulated using appropriate phase-shifting algorithms. The proposed method is well-suited for high-precision three-dimensional shape measurement scenarios in many fields such as integrated circuit manufacturing process control and micro-electro-mechanical system quality inspection. The experiment results demonstrate that the anti-crosstalk method is effective and can realize three-dimensional reconstruction for discontinuous planar surface and spherical surface.

A three-level slicing algorithm in a multi-slice multi-numerology context

Fifth generation (5G) mobile networks feature a new concept called Bandwidth Part (BWP) that permits applying various multiple Orthogonal Frequency-Division Multiplexing (OFDM) subcarrier spacing, also coined numerologies, in the same band. With flexible numerology, the sought-after purpose is achieving lower latency for the Ultra Reliable Low Latency Communications (URLLC) service. However, the lucrative multiple numerology gains might not stand because of the ensuing Inter-Numerology Interference (INI) problems. In this paper, we assess the feasibility, as well as the profitability, of multi-numerology in a multi-slice setting. In such a context, it is paramount to study the radio resource allocation problem at the Radio Access Network (RAN) level. To that aim, we propose a three-level slicing algorithm that efficiently selects the BWP serving the URLLC users from a set of BWPs using different numerologies, designs a guard band among these BWPs to reduce INI without wasting radio resources, and attributes a bandwidth to each slice depending on multiple parameters such as the users’ Key Performance Indicators (KPIs), channel conditions, INI, and the incurred monetary cost. This work considers the three 5G services, namely the enhanced Mobile BroadBand (eMBB) service, the URLLC service and the massive Machine-Type Communications (mMTC) service. The proposed algorithm combines various tools from Game Theory, Deep-Q learning Networks as well as savvy heuristics. The performance evaluation demonstrates the high efficiency of our solution in terms of latency and throughput compared to well-known approaches in the State-of-the-Art.

Digital mobile fronthaul based on noise-coupling sturdy-multistage noise-shaping modulator

In this paper, digital mobile fronthaul (MFH) architecture enabled by noise-coupling sturdy-multistage noise-shaping (SMASH_NC) modulator is experimentally demonstrated and investigated. To verify the noise-shaping capability of the proposed SMASH_NC modulator, 12 aggregated orthogonal frequency division multiplexing (OFDM) component carriers (CCs) are firstly modulated to 4-level pulse-amplitude-modulation (PAM4) signal, and then transmitted over optical intensity modulation-direct detection (IM-DD) links. After 20 km single mode fiber (SMF) transmission, the error vector magnitude (EVM) floor of signal modulated by traditional SMASH is beyond the 512-quadrature amplitude modulation (QAM) EVM threshold of 3%, while the minimum EVMs of signal modulated by our previous proposed SMASH_FB and SMASH_NC are 1.81% and 1.16%, respectively. Compared with SMASH_FB, SMASH_NC achieves 0.6 dB receiver sensitivity improvement at 3% EVM threshold, in addition, the number of adders and multipliers can be reduced by 25% and 26.32%, respectively. To better accommodate the out-of-band leakage in the CCs aggregation, filter-bank-multicarrier (FBMC) is demonstrated and investigated with only 22.89 kHz guard band between two adjacent CCs. Compared with OFDM, the EVM floor of FBMC is successfully reduced to 0.39%, and a 0.9 dB receiver sensitivity improvement is obtained with less guard band.