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In the present scenario, orthogonal frequency division multiplexing (OFDM) waveform technique is playing a significant part in smart hospitals. Still, its impact is not effective in smart hospitals due to the numerous limitations such as loss of bandwidth due to the use of guard band, spectrum leakage, high peak to average power (PAPR), high detection delay, and thus along. Right now, fifth-generation (5G) employment is becoming regularized around the world and the state-of-the-art radio system is expected to meet all the demands of smart hospitals. High spectrum access, massive capacity, high throughput, and low PAPR are the requirements of smart healthcare hospitals. The digital hospital has seen tremendous progression in bandwidth requirements. From transmitting medical images to wearable devices, networks must operate at maximum speeds to safeguard patient care. The selection of competent transmission technologies will play an important role in the regularization of digital hospitals equipped with 5G. In the projected work, we focus on the implementation of novel waveforms such as Non-orthogonal multiple access (NOMA), Universal filter multi-carrier (UFMC), and filter bank multi-carrier (FBMC) system. Several parameters such as power spectrum density, bit error rate, capacity, and PAPR of advanced waveforms and OFDM methods are analyzed and studied.

With the increasing demand of bandwidth, a higher capacity communication system is required for short-reach optical link. Intensity modulation/direct detection (IM-DD) is considered as a reasonable method, due to its low cost and power consumption. In the aspect of digital signal processing (DSP), discrete Fourier transform-spread (DFT-s) precoding can be used to reduce peak to average power ratio (PAPR) and average the noise among the subcarriers. In addition, probabilistic shaping (PS) turns out to further increase the system capacity. We experimentally demonstrated a 200 Gbit/s single λ dual band DMT transmission with a spectrum efficiency (SE) of 6.29 bit/s/Hz. The achievable information rate (AIR) of the proposed dual band signal increases about 30 Gbit/s compared with that of single band signal. Moreover, single-sideband (SSB) signal and signal with guard band are implemented to mitigate the frequency selective fading of optical fiber chromatic dispersion (CD). The performance of these two methods are quite closed for short reach transmission. Considering the signal-signal beat interference (SSBI) introduced by the SSB signal, an extra Volterra filter is applied in DSP. Besides, an extra optical filter is required to generate the SSB signal.

Self-Heating Effects (SHE) is known as one of the key reliability challenges in FinFET and beyond. Large timing guard bands are necessary, which we try to reduce. In this work, we propose operating (biasing) processors at Zero-Temperature Coefficient (ZTC) to contain (mitigate) SHE-induced delay. Operating at ZTC allows near-zero timing guard band to protect circuits against SHE. However, a trade-off is found between thermal timing guard band and performance loss from lowering the voltage.

This study has investigated the mitigations necessary for successful compatibility between International Mobile Telecommunications (IMT) services and Fixed Satellite Service (FSS) Earth Stations operating in adjacent frequency bands. We consider a problem where IMT services operate in the 3.4–3.6 GHz frequency band and FSS Earth Stations operate in the adjacent 3.6–3.8 GHz band (both bands are within the frequency range designated C-band). The results presented in this paper are applicable to other boundaries between IMT and FSS operating in C-band. This is an adjacent band compatibility problem, hence the mitigation considered is based on frequency separation. We firstly perform a co-frequency interference analysis and then determine the Net Filter Discrimination available for a range of possible frequency separations including Guard Bands. These calculations rest on some assumptions regarding the IMT transmitter and FSS receiver spectrum masks. We present some results which show that an 18 MHz Guard Band is sufficient to mitigate interference. This analysis is based on the median aggregate interference-to-noise ratio $$\Sigma I/N$$ delivered by our co-frequency analysis, using a − 10 dB threshold and covering all of the spectrum mask combinations considered in the study.

Filter bank multicarrier (FBMC) is one of the effective candidates for the fifth generation of wireless communication networks. 5G (5th-generation wireless systems) is accepted as the next major stage of mobile telecommunication technology. The extent of 5G will be expanded mobile broadband services to next-generation automobiles and connected machines. In particular, filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) is determined as the future generation 5G air interface by researchers recently. Filter bank multicarrier (FBMC) is admitted as one of the alternative technologies for multicarrier modulation. Compared to orthogonal frequency-division multiplexing (OFDM), FBMC has better spectrum shape and supports mobility. Therefore, efficient hardware implementations have highly interested researchers. Cyclic prefix (CP) and guard band are used for orthogonal frequency-division multiplexing (OFDM) and this causes loss of spectral efficiency, but FBMC applications do not need CP and guard band. Due to the fact that FBMC has offset QAM (OQAM) and band-limited filtering features on each subcarrier, the need for CP and guard band is eliminated. In this paper, novel pipelined hardware architecture of the filter design of FBMC/OQAM modulator has been proposed.

We experimentally obtain a lower frequency shift based on mode conversion by using a mode-selective coupler (MSC) and an acoustically induced fiber grating (AIFG) for optical heterodyne micro-vibration measurement. Through efficient conversion between LP11 and LP01 core modes in a few-mode fiber, a mode conversion frequency shifter (MCFS) can be achieved and the magnitude of frequency shift is several hundred kHz, which is generally challenging for traditional bulk acousto-optic frequency shifter. Moreover, the signal-to-signal beating interference (SSBI) can be eliminated by using the MCFS without requirement of guard band. The scheme of optical heterodyne micro-vibration measurement based on the MCFS has a high-quality signal-to-noise ratio (SNR) over 85 dB. An all-fiber Bragg grating (FBG) scheme is also designed to improve the measurement sensitivity of heterodyne detection, which has a measurable vibration frequency range of 1 Hz to 300 kHz and minimal detectable amplitude of 0.019 nm. The all-fiber MCFS has the advantages of compactness, easy integration and can be applied directly to satellite ground station and laser feedback tomography.

Cognitive radio (CR) is a promising technology that allows devices to effectively utilize the underutilized or unutilized portions of the licensed spectrum. In literature, several channel assignment and spectrum sharing algorithms for CR Networks (CRNs) have been developed to improve spectrum efficiency without considering the problem of Adjacent Channel Interference (ACI). Guard-Band (GB)-aware mechanisms have been proposed in CRNs to prevent ACI and improve spectrum efficiency. However, most of the existing GB-aware algorithms assume having channels with fixed-rate and employ a sequential channel assignment paradigm. Unfortunately, this assumption is not realistic, because channel’s conditions may vary over time. In this work, we propose a GB-aware channel assignment that considers the channel-dependent achieved transmission rates (due to Rayleigh fading time-varying conditions) at different time slots while simultaneously assigning channels to several CR transmissions. This batch based proposal aims at increasing network capacity and minimizing the number of assigned channels per user subject to rate demand and interference constraints. Simulation experiments demonstrate the effectiveness of our proposed scheme, which show a significant improvement in network performance in terms of the number of served CR users.

We propose the use of the specific form of the integrated device known as the boxcar filters for big data transmission, where the advantage of such device is the number of roll-off (bandwidth) can be increased to meet the large demand of the future bandwidth requirements. A boxcar filter system is formed by the serial Panda-ring resonators, where the initial and end rings are used to form the whispering gallery mode beams for the light fidelity (LiFi) up-down-link conversion. There are 5 boxcar circuits within the system. Each of boxcar devices has the electro-optic connection that can be used to perform the external signal processing applications, where all electronic signals are changed to be the light signals and connected to the network via the free-space up-down link nodes. In a simulation, the selected light source is fed into the boxcar filters via the input port, in which the single roll-off bandwidth of 300 THz is obtained. The frequency guard band is given by each boxcar separation. In applications, the electromagnetic immunity interference (EMI) signals can be obtained by the electro-optic conversion circuit, which is the medical instrument specification requirement. The low EMI signals can be connected to the network and transmission using the LiFi network to the remote area. In addition, the medical information to home using the big data via the ad hoc LiFi network and the internet of thing platform arrangements are also proposed.

The millimeter wave band is becoming popular for mobile broadband usage such as fifth-generation (5G) mobile and mobile satellite services utilizing earth stations in motion (ESIM). According to the 2019 World Radiocommunication Conference (WRC-19), the 5G and ESIM systems will operate in adjacent frequency bands bounded by 27.5 GHz; therefore, the adjacent channel compatibility between ESIM and 5G should be verified. Both, the minimum coupling loss (MCL) and Monte-Carlo (MC) methods are applied to assess the worst and most practical interference effects, respectively, for all types of ESIM including the following: maritime ESIM (M-ESIM), land ESIM (L-ESIM), and aeronautical ESIM (A-ESIM). The distance and guard band between the two systems are indicated by the compatibility conditions. In addition to the conventional interference-to-noise ratio ( $I/N$ ), the throughput loss of a 5G system is proposed to assess the performance degradation caused by the ESIM interference. Two orthogonal frequency division multiplexing (OFDM) waveforms are proposed to suppress ESIM power leakage into an adjacent channel. A mathematical expression regarding the power spectral density (PSD) and frequency dependent rejection (FDR) is derived for these waveforms, suggesting that the interference can be alleviated. A measured single carrier waveform of a commercial ESIM equipment is used as the benchmark against the proposed OFDM waveforms. The windowed OFDM is able to reduce the guard band by 50–77%. The results obtained for various elevation angles of the ESIM antenna are determined to be applicable to various regions globally.

A novel beat interference cancellation receiver (BICR) is proposed to cancel the signal-signal beat interference (SSBI) for polarization division multiplexed (PDM) optical orthogonal frequency division multiplexing (OOFDM) system, where two single sideband (SSB) OOFDM signals are polarization multiplexed along with their offset optical carriers (OCs) located at opposite sides. At receiver, the PDM SSB-OOFDM signal is equally power split into four beams with one or two OCs filtered out, and then fed into two balanced photodiode pairs for recovering the RF-OFDM signals with SSBI cancellation. The PDM SSB-OOFDM system is insensitive to fiber polarization mode dispersion since the proposed BICR is implemented without polarization-sensitive devices. Moreover, the spectral efficiency is greatly improved because of PDM and the small guard band since the SSBIs are eliminated. The proposed BICR scheme is validated with a simulation link of 112 Gbps 16-QAM PDM SSB-OOFDM signals. After 120km SSMF transmission, the EVM keeps below forward error correction limit of 16.3%.

We propose a novel zero guard band (ZGB) multi-twin-SSB bidirectional passive optical network system which combines the multiband carrier-less amplitude phase and twin single sideband (SSB) modulation techniques. The multi-twin-SSB signal is generated at the downlink transmitter side with zero guard band between the left-sideband and right-sideband. A weak local oscillator which is extracted from the uplink optical source aids the downstream signal detection. Kramers-Kronig algorithm is used at both downlink and uplink receiver sides to reconstruct the SSB signal and eliminate the signal-signal beat interference. The downstream and upstream signals are transmitted in a single fiber without any spectral overlap between them and the Rayleigh backscattering noise is removed by the optical band-pass filter. The proposed scheme is extensively investigated and analyzed with four sub-bands using 50 Gbps 16-QAM modulation for each sub-band over a bidirectional 50 km transmission. The results show that, compared with the conventional multi-twin-SSB scheme, the proposed ZGB multi-twin-SSB scheme can improve the spectral efficiency by about 11%. The required optical signal to noise ratio (OSNR) and the required received optical power (ROP) can be reduced by more than 15 dB and 7 dB respectively at the 7% hard decision forward error correction (HD-FEC) threshold (bit error rate of 3.8 × 10-3), respectively. For the uplink transmission, the required ROPs for the inner and outer sub-bands at 7% HD-FEC are about -10 dBm and -11 dBm, respectively. And the signal to noise ratio to the corresponding ROPs for the inner and outer sub-bands are 15.4 dB and 15.3 dB, respectively.

The next-generation communication technologies are evolving towards increased flexibility in various aspects. Although orthogonal frequency division multiplexing (OFDM) remains as the waveform of the upcoming fifth-generation (5G) standard, the new radio provides flexibility in waveform parametrization (a.k.a. numerology) to address diverse requirements. However, managing the peaceful coexistence of mixed numerologies is challenging due to inter-numerology interference (INI). This paper proposes the utilization of adaptive guards in both time and frequency domains as a solution along with a multi-window operation in the physical (PHY) layer. The adaptive windowing operation needs a guard duration to reduce the unwanted emissions, and a guard band is required to handle the INI level on the adjacent band. The guards in both domains are jointly optimized with respect to the subcarrier spacing, use case (i.e., service requirement), and power offset between the numerologies. Also, the multi-window approach provides managing each side of the spectrum independently in case of an asymmetric interference scenario. Since the allowed interference level depends on the numerologies operating in the adjacent bands, the potential of adaptive guards is further increased and exploited with a medium access control (MAC) layer scheduling technique. The proposed INI-based scheduling algorithm decreases the need for guards by allocating the numerologies to the available bands, considering their subcarrier spacing, power level, and SIR requirements. Therefore, INI management is performed with a cross-layer (PHY and MAC) approach in this study. The results show that the precise design that accommodates such flexibility reduces the guards significantly and improves the spectral efficiency of mixed numerology systems., Comment: 9 pages, 9 figures, 5 tables, accepted version, (The URL for the final version: https://ieeexplore.ieee.org/document/8986659)

Licensed-assisted access (LAA) is a new feature of 3GPP LTE that utilizes unlicensed spectrum as a means of providing additional bandwidth. For fair coexistence with other incumbent systems such as Wi-Fi, LAA runs a listen-before-talk (LBT) procedure before transmission, which is designed to support multi-carrier operation as well. However, inherent power leakage to adjacent carriers ruins multi-carrier LBT and deteriorates aggregation capacity considerably. To solve this power leakage problem, we propose a hybrid design of the two LBT types of the specification to have the advantages of both, which is realized by carrier grouping, and develop an algorithm that determines division of carriers into multiple groups with a guard band in between to avoid power leakage among groups and selects the primary carrier of each group so as to maximize LAA’s carrier aggregation capacity. Through extensive simulation, we demonstrate that the proposed algorithm enhances system throughput considerably over conventional mechanisms while coexisting fairly with Wi-Fi systems. We also investigate the impact of the depth of group splitting and transmit power on performance.

A considerable part of latency in the baseband of massive multiple-input multiple-output (MIMO) systems is introduced by orthogonal frequency division multiplexing (OFDM) (de)modulation. To address the low-latency demand of massive MIMO systems, a fast Fourier transform (FFT) processor and corresponding reordering scheme are proposed, which reduce the processing latency and reordering latency of OFDM-based systems, respectively. The main idea is to utilize the OFDM guard bands to decrease the number of required computations and thus the processing time. In case of a 2048-point IFFT, the proposed scheme leads to 42% reduction in latency compared to the reported pipelined schemes at the cost of 4% additional memory, which is around 2.4% of the total chip area. To realize this idea, a modified pipelined architecture with a reorganized memory structure and also an efficient data scheduling mechanism for memories and butterflies are developed. Using the proposed scheme, a 2048-point FFT/IFFT processor has been implemented in a 28-nm complementary metal-oxide-semiconductor technology. The post-layout simulations show that our design achieves a throughput of 0.6 GS/s and 1200 clock cycles latency, the lowest latency reported to-date for single-input pipelined FFT/IFFT architectures.

In this letter, a signal-to-signal beating interference (SSBI) cancellation technique is proposed in direct detection transmission system based on balanced photodiodes. We use a pilot-supported single-sideband direct detection scheme to transmit up to 400-Gb/s signal in three branches through a 10-km 7-core fiber. Using the manner of transmitting the signal in one core and the combination of signal and pilot in another core, the SSBI terms can be efficiently mitigated in both 100-Gb/s and 400-Gb/s direct detection optical orthogonal frequency division multiplexing transmission systems. Compared to the conventional pilot-supported direct detection scheme, no guard band is required based on our proposed SSBI elimination technique. The efficiency of the receiver’s bandwidth is significantly enhanced.

We experimentally demonstrate the generation of a single-sideband orthogonal frequency division multiplexed (OFDM) signal using an on-chip silicon photonics microring-based IQ modulator. Over 18-dB sideband suppression ratio is achieved for the wideband OFDM: 15.7-GHz data band and 2.7-GHz guard band. The 31.4-Gb/s signal was transmitted over 20 km of standard single-mode fiber with a bit error rate below the forward error correction threshold. While single-sideband continuous-wave signals have been produced with such hardware, this is the first demonstration of stable data transmission on the single sideband carrier.

The existing time-division duplex (TDD) and frequency-division duplex (FDD) techniques rely on a guard time and/or a guard band to avoid self-interference (SI) between the uplink and downlink channels, which results in the wastage of precious spectral resources. The full-duplex (FD) schemes of in-band FD (IBFD), as well as multicarrier division duplex (MDD), may overcome this drawback while retaining the key benefits of both TDD and FDD. Moreover, the MDD exhibits the exclusive benefits of the reduced peak-to-average-power ratio (PAPR) for signal transmission as well as the SI-free signal detection. Against this background, in this paper, we propose a novel FD scheme conceived for frequency-selective millimeter-wave (mmWave) channels, which have not been investigated in the open literature. Furthermore, we propose a novel projection-aided iterative eigenvalue decomposition (P-IEVD) algorithm, which performs null-space SI cancellation in the inherent beamforming structure of mmWave communication. Our simulation results confirm that the MDD is capable of outperforming its half-duplex (HD) counterparts of the TDD/FDD, even the IBFD can only achieve a better bandwidth efficiency than the MDD when a sufficiently high SNR is provided.

For fifth-generation (5G) wireless technologies, one major problem is Doppler shift. In order to overcome this problem, a filter called Fractional Powered Binomial (FPBF) Windowed PHYDYAS filter is proposed in this paper for FBMC system. 5G communication and how Doppler shift worked in 5G communication have been explored in short here. For this the role of different parameters like Signal Interference Ratio (SIR), sub-carrier spacing, guard band has also been explored. The performances of this filter was compared with PHYDYAS filter through parameters like Signal to Interference Ratio (SIR), Bit Error Rate (BER), and impulse responses within the time and frequency domain. The performance of 5G communications and other parameters have been investigated through MATLAB simulations.

Digital predistortion (DPD) is an important technique that is commonly used in wireless transmitters to reduce the out-of-band emissions caused by power amplifier (PA) nonlinearities. This frequency-domain goal is generally achieved by learning a baseband equivalent time-domain inverse transfer function of the PA and applying it to the transmitted digital baseband signal. In this work, we take advantage of the frequency-domain nature of orthogonal frequency-division multiplexing (OFDM) signals by injecting cancellation tones into the guard-band subcarriers to perform DPD. We experimentally evaluate our OFDM-based DPD (ODPD) method using a Doherty PA and show that, when compared to a standard generalized memory polynomial solution, the ODPD can achieve better suppression of out-of-band emissions with lower complexity. Moreover, when combined with a neural network model of the PA, our proposed ODPD method only requires oversampling the transmitted signal by a factor of two, which has important implications for the analog transceiver front-end.

We propose a nonlinear impairments-aware channel estimation model based on deep neural network (DNN) to conduct optimal dynamic modulation format and guard band assignment for RoF broadcasting system.

Elastic optical networks are a network infrastructure capable of withstanding the high demand for data traffic from high-speed networks. One of the problems that must be solved to ensure the smooth functioning of the network is called Routing, Modulation Level and Spectrum Assignment (RMLSA). This work aims to propose a new approach to this problem with an algorithm to select the guard band in an adaptive way. Two algorithms for the adaptive selection of the guard band, called Guard Band according to Use of the Network (GBUN) and Guard Band by OSNR Margin (GBOM), are presented. The GBUN algorithm performs the guard band selection based on the usage level of network. On the other hand the GBOM algorithm uses an Optical Signal to Noise Ratio (OSNR) margin for the selection of the guard band. The performances of the proposed algorithms are compared with algorithms that use fixed guard band values and the adaptive proposal AGBA. The results showed that the GBOM algorithm presented a better performance in terms of bandwidth blocking probability for the studied scenarios. In general, GBOM also presents a better energy efficiency when compared to the other algorithms.

In this paper, we propose the adaptive guard band allocation based on outage probability for the sub-bands with different numerologies on Nakagami-m fading channels in uplink cellular networks. First, we analyze inter-numerology interference and derive the outage probability of each sub-band in closed form. Then, the optimization problem is formulated to obtain the guard band assigned to each sub-band. The validity of the analysis is verified by comparing it to the Monte-Carlo simulation results. It is also shown that applying the guard band determined through the proposed algorithm can allocate smaller guard band than symmetric guard band allocation algorithm.

We demonstrate and analyze the phase noise of optical carrier-assisted (OCA) single-sideband system with Kramers-Kronig receiver. The results show that the tardy variation phase noise induced by Kramers-Kronig receiver is periodically linear related to the guard band and baud rate. © 2020 The Author(s)

The existence of inter-numerology interference (INI) is a major drawback for the flexible multi-numerology frame structure proposed for the upcoming fifth generation New Radio (5G-NR). Insertion of a guard band (GB) between adjacent numerologies has been widely used in the literature as one of the effective ways to reduce the INI. However, the conventional way of implementing GBs is inefficient in terms of spectrum usage. In this letter, we exploit the inherent INI characteristics of the scalable multi-numerology structure to propose a more spectrally efficient way of implementing GBs. It is shown through simulations that the proposed GB insertion technique enhances the GB utilization up to 50% while achieving the same bit error rate performance as the conventionally implemented GB. 218E035

The final publication is available at Springer via http://dx.doi.org/10.1007/s11107-020-00890-z Filterless optical networks (FONs) have been proposed as a feasible solution for optical metro networks. In addition, as a result of the shorter distance compared to core optical networks, direct detection optical transmission systems can be used in metro FONs, which reduces costs, as compared to coherent detection systems. In this work, we present two optical signal tracking approaches for FONs that allow to detect small frequency laser drift problems and enable safely reducing channel spacing. Additionally, we study the most proper resolution for optical spectrum analyzers continuously scanning the whole C-band. Proposed approaches are: (1) feature-based tracking and (2) residual-based tracking. Experiments are carried out to compare the performance of the approaches for both direct detection and coherent detection systems, in the case of a single optical signal with no neighboring signals nearby in the spectrum, as well as in the case of a group of optical signals closely allocated in the spectrum. The results show that the residual-based approach enriched with contextual information enables to better track and correct the wavelength drifts before they reach their limits (e.g.,¿±¿2.5 GHz), leading to the guard band reduction for what concerns wavelength drifts. The research leading to these results has received funding from the European Commission for the H2020-ICT-2016-2 METRO-HAUL project (G.A. 761727), from the AEI/FEDER TWINS project (TEC2017-90097-R), and from the Catalan Institution for Research and Advanced Studies (ICREA).

We experimentally demonstrate a single-carrier dual-SSB signal generation without guard band based on a low-cost DDMZM. A 112-Gb/s dual-SSB modified duobinary PAM4 signal is transmitted over 80-km SMF by using a MIMO linear equalizer.

A 5G communication system includes massive machine-type communication, enhanced mobile broadband, and ultra-reliable low-latency communication. To meet the requirements of 5G applications, researchers have considered various scalable subcarrier spacings and transmission time intervals. In this article, we introduce the concept of waveform multiplexing, which is a resource management system for numerology multiplexing that employs appropriate waveforms to various numerologies. It also possesses both a dynamic cyclic prefix and a minimum guard band, which are the key features for achieving high spectral efficiency. We verify the significant gain produced by proposed waveform multiplexing by performing extensive 3D ray-tracing- based system-level evaluations in realistic 3D environments. Finally, we provide guidelines on waveform multiplexing design by considering the time-domain and frequency-domain characteristics of the new radio waveform candidates.

Modern fiber-optic coherent communications employ advanced, spectrally efficient modulation formats that require sophisticated narrow-linewidth local oscillators (LOs) and complex digital signal processing (DSP). Self-coherent optical orthogonal frequency-division multiplexing (self-CO-OFDM) is a modern technology that retrieves the frequency and phase information from the extracted carrier without employing a LO or additional DSP. However, a wide carrier guard is typically required to easily filter out the optical carrier at the receiver, thus discarding many OFDM middle subcarriers that limit the system data rate. Here, we establish an optical technique for carrier recovery, harnessing large-gain stimulated Brillouin scattering (SBS) on a photonic chip for up to 116.82 Gbit·s−1 self-CO-OFDM signals, without requiring a separate LO. The narrow SBS linewidth allows for a record-breaking small carrier guard band of ∼265 MHz in self-CO-OFDM, resulting in higher capacity than benchmark self-coherent multi-carrier schemes. Chip-based SBS-self-coherent technology reveals comparable performance to state-of-the-art coherent optical receivers while relaxing the requirements of the DSP. In contrast to on-fiber SBS processing, our solution provides phase and polarization stability. Our demonstration develops a low-noise and frequency-tracking filter that synchronously regenerates a low-power narrowband optical tone, which could relax the requirements on very-high-order modulation signaling for future communication networks. The proposed hybrid carrier filtering-and-regeneration technique could be useful in long-baseline interferometry for precision optical timing or reconstructing a reference tone for quantum-state measurements.

In this paper, we have proposed a polarization-division multiplexing (PDM) single-sideband optical orthogonal frequency division multiplexing (SSB-OOFDM) scheme with signal-signal beat interference cancellation receivers with balanced detection (ICRBD). This system can double channel capacity and improve spectrum efficiency (SE) with the reduced guard band (GB) due to the PDM. Multiple input multiple output (MIMO) technique is used to solve polarization mode dispersion (PMD) associated with channel estimation and equalization. By simulation, we demonstrate the efficacy of the proposed technique for a 2 × 40 Gbit/s 16-QAM SSB-PDM-OOFDM system according to the error vector magnitude (EVM) and the constellation diagrams.

Body area networks (BANs) are systems of wearable computing devices for long-term monitoring of personal health care. BAN is an emerging technology for the worldwide ageing population. In the BAN system, the transceiver is the most energy-consuming part of a sensor node and radio transmission in the vicinity of the human body is highly lossy and inefficient. Therefore, the energy of the sensor node constraints the life cycle and quality of service of the network; consequently, low-cost protocol shaves attracted wide interest. This study proposes a frame structure model of a self-adaptive guard band protocol, which introduces a GB in each time slot according to the allowed maximum time drift of the crystal, adaptively adjusts the value of the GB based on the actual time drift, and then ensures that the node simultaneously maintains the sleeping state and synchronisation with the coordinator during beacon transmission, thus reducing the energy consumption.

We theoretically study the performance of single sideband discrete multitone (SSB-DMT) in the C -band with intensity modulation and direct detection. Our analysis allows us to quantify the impact of different noise sources such as signal-to-signal beating interference, phase-to-amplitude noise, attenuation, and receiver sensitivity on SSB-DMT. Our analytical tools also allow us to optimize the signal-to-carrier power ratio to maximize SSB-DMT throughput. We provide equations to calculate bit error rate of bit allocated SSB-DMT. Finally, we examine various system parameters (laser linewidth, system bandwidth, and fiber length) to determine their impact on the performance of zero guard band SSB-DMT.

To further improve receiver sensitivity of spectrally-efficient guard-band direct-detection optical orthogonal frequency-division multiplexing (OFDM) with twin single-side-band (SSB) modulation technique, an optical IQ modulator (IQM) is employed to optimize optical carrier-to-signal power ratio (CSPR). The CSPRs for the guard-band twin-SSB-OFDM signal generated by using dual-drive Mach–Zehnder modulator (DD-MZM) and optical IQM are theoretically analyzed and supported by simulations. The optimal CSPR for the two types of guard-band twin-SSB-OFDM are identified. The simulations exhibit that the error vector magnitude (EVM) performance of the IQM-enabled guard-band twin-SSB-OFDM is improved by more than 4-dB compared to that of the twin-SSB-OFDM enabled by DD-MZM after 80-km single-mode fiber (SMF) transmission. In addition, more than 3-dB and 10 dB receiver sensitivity improvements in terms of received optical power (ROP) and optical signal-to-noise ratio (OSNR) are also achieved, respectively.

Body area networks (BAN) are at the forefront of technologies for long-term monitoring of personal healthcare, which is intended be an effective strategy to address the aging population worldwide. The transceiver is the most energy-consuming part of a sensor node, and radio transmission in the vicinity of the human body is highly lossy and inefficient. Therefore, the energy of the sensor node constrains the life cycle and quality of service (QoS) of the network; consequently, low-cost protocol shave attracted wide interest. This paper proposes a frame structure model of a self-adaptive guard band (SAGB) protocol, which introduces a guard band (GB) in each time slot according to the allowed maximum time drift of the crystal, adaptively adjusts the value of the GB based on the actual time drift, and then ensures that the node simultaneously maintains the sleeping state and synchronization with the coordinator during beacon transmission, thus reducing the energy consumption.

For short reach and metro applications, single sideband (SSB) is a promising scheme due to its high spectral efficiency and tolerance to chromatic dispersion. In this study, we propose a novel asymmetric twin-SSB scheme based on Nyquist pulse shaping. Without joint equalization, the two sidebands can be separately detected with a small guard band. We experimentally demonstrate 224-Gb/s 16-ary quadrature amplitude modulation (16-QAM) asymmetric twin-SSB transmission with direct detection. After 240-km standard single mode fiber (SSMF) transmission, the bit error rates (BERs) of the right-sideband (RSB) and the left-sideband (LSB) are 3.2 × 10−3 and 2.8 × 10−3, respectively, which are below the 7% hard-decision forward error correction (HD-FEC) threshold of 3.8 × 10−3. The net bitrate is 203.7 Gb/s with consideration of both frame redundancy and HD-FEC overhead. To our best knowledge, we report the longest transmission distance for 200G single wavelength and single polarization direct detection systems. The advantages of the asymmetric twin-SSB scheme over the symmetric scheme are discussed through simulating the crosstalk resistance of both two schemes. We also demonstrate 300-Gb/s 32-QAM transmission over 80-km SSMF. The BERs of RSB and LSB are 1.50 × 10−2 and 1.61 × 10−2, respectively, which are below the 15% soft-decision forward error correction (SD-FEC) threshold of 1.8 × 10−2. The net bitrate is 254.3 Gb/s with consideration of both frame redundancy and SD-FEC overhead. To our best knowledge, it is the maximum bitrate ever reported for C-band 80-km single wavelength and single polarization direct detection transmission. The proposed scheme provides a useful and low-cost solution for high speed datacenter interconnection and metro-scale transmission.

One of the fundamental problems in cryptography is the generation of a common secret key between two legitimate parties to prevent eavesdropping. In this paper, we propose an information-theoretic secret key generation (SKG) method for time division duplexing (TDD)-based orthogonal frequency-division multiplexing (OFDM) systems over multipath fading channels. By exploring physical layer properties of the wireless medium, i.e., the reciprocity, randomness, and privacy features of the radio channel, an SKG method is proposed to maximize the number of secret bits given a target secret key disagreement ratio (SKDR). In the proposed SKG method, the phase information of the estimated channel state information (CSI) is distilled for SKG, and a special guard band (GB) scheme is designed to achieve the target SKDR with a small phase information loss. The proposed GB consists of both the amplitude GB (AGB) and phase GB (PGB), where the AGB is determined by the average signal-to-interference plus noise ratio (SINR), whereas the PGB adapts itself to the instantaneous SINR and thus incurs a smaller phase information loss in the higher SINR region. Analyses show that this GB scheme trades off a small loss of channel phase information for a better SKDR performance, and achieves a much larger number of quantization levels for a given SKDR due to the fact that the PGB decreases quickly as the SINR increases. Based on the performance analysis on the SKDR, the average secret key length, the phase information loss percentage (PILP), and the optimal GB and quantization level of the adaptive quantizor are derived for a given target SKDR. Both analytical and simulation results are presented to demonstrate the superiority of the proposed scheme for TDD-OFDM systems over frequency-selective fading channels.

Semiconductor aging is a serious threat to the reliability of a system. We address the aging level of semiconductor components by describing the degree of semiconductor aging under certain operating conditions, including voltage, frequency, temperature, and usage rate. Aging level information can be used to follow the real aging rate of a device, predict the remaining life, and control the device performance under certain degradation conditions by balancing the operation of various device components. Such applications can improve the reliability of automotive semiconductor systems, which should have longer lives than mobile systems. In this brief, we present an aging level estimating flip-flop (FF) that can be used for these and other applications as well. Moreover, we can control the operation of the proposed FF by controlling its clock and control signals. We demonstrate an application of the proposed FF for aging-monitoring, showing that, by halting the operation of the proposed FF, the power consumption is significantly reduced compared with other approaches.

Simplified, closed-form, mathematical expressions for four wave mixing (FWM) in coherent optical systems are derived. FWM is an important limitation in both coherent OFDM (CO-OFDM) and Nyquist-WDM systems. The effect is also important in networks deploying dispersion shifted fiber and/or based on very narrow channel spacing. In this work, 1) we improve the accuracy of the formalism in CO-OFDM systems by taking into account not only the contribution due to the power of the central carrier but also the contribution due to the spectral flanks as well as the guard band between channels and 2) we extend the formalism to work for flexgrid systems. The derived expressions can be used for a quick estimation of system performance and/or can be incorporated in routing algorithms that account for physical layer effects. The formalism for flexgrid systems is estimating the power of FWM with improved accuracy compared to existing models in the literature so it can be a key asset in dynamic resource allocation operations. Finally, the derived expressions are valid for both, uncompensated and dispersion managed systems.

Service diversity is expected in the upcoming fifth-generation (5G) cellular networks, which poses great challenges to the underlying waveforms to accommodate heterogeneous service requirements in a flexible way. By dividing the bandwidth into several subbands, each having a different numerology, this paper reports a field trial in time division duplex downlink conducted on a configurable test bed in a real-world environment for the performance evaluations of orthogonal frequency-division multiplexing (OFDM)-based 5G waveform candidates, i.e., cyclically prefixed OFDM (CP-OFDM), windowing OFDM (W-OFDM), and filtered OFDM (f-OFDM), in the presence of mixed numerologies. Field trial results confirm the feasibility of mixed numerologies and reveal the impact of several important system parameters, e.g., guard bandwidth, data bandwidth, signal-to-noise ratio (SNR), and transmit power. The results also suggest that f-OFDM outperforms CP-OFDM and W-OFDM in terms of both the spectrum efficiency and robustness in a high SNR regime, and the gain increases with a higher inter-numerology out-of-band interference. In some specific scenarios, ideal spectrum utilization can be realized by f-OFDM which completely removes the guard band.

Filter-bank multicarrier (FBMC) is proposed to demonstrate a full-duplex asynchronous quasi-gapless (only one subcarrier spacing) carrier aggregation for millimeter-wave (MMW) radio-over-fiber radio access technology (RAT) in next-generation 5G heterogeneous mobile-data-network (Het-Net). Fourteen broadband FBMC signals are aggregated with only one subcarrier guard band in the 60-GHz MMW downlink. In the uplink quasi-gapless asynchronous inter-RAT carrier aggregation between 60-GHz MMW and 4G long-term evolution (LTE) signals are also demonstrated. System performances assessment of FBMC and orthogonal frequency-division multiplexing (OFDM) under different operation condition are studied. Our results also show that the FBMC-based new RAT is also backward compatible with existing LTE systems in the Het-Net. Compared with OFDM-based signals with large guard bands, FBMC achieves higher spectral efficiency with better error vector magnitude performance at less received power and smaller guard bands.

A low-power 2-Mb Resistance random access memory (ReRAM) macro is developed in a 90-nm CMOS platform with a 3-nm-thick TaO x /Ta2O5 switching layer of the active area of $0.01~\mu \text{m}^{2}$ . Instability of the ON-state minority bits degrades the high-temperature retention lifetime. The oxygen vacancies in the filament are annihilated by oxygen ions, which have been generated mainly by the OFF-write bias repeated in the ON/OFF switching cyclesbefore the retention. This instability is improved by decreasing the oxygen concentration near Ru bottom electrode as well as lowering the OFF-write bias. Instability of the OFF-state minority bits narrows the memory window by random telegraph noise (RTN). Setting a statistically derived guard band with a pulse-modulated verify sequence is able to handle RTN to ensure the memory window. The 2-Mb ReRAMmacro with 1-b error-correcting code is confirmed to ensure ten years’ retention from −40 °C to 85 °C after 1E3 ON/OFF cycles.

In high volume manufacturing, conventional approach to deal with inverse-temperature dependence (ITD) and aging is to add a postsilicon flat voltage guard band to all dies based on testing a small random sample of dies. Although this scheme guarantees error-free operation, it significantly degrades energy efficiency, as it penalize all dies for the maximum delay degradation due to ITD and aging as seen by the worst case die, while also assuming maximum aging condition. In this paper, a graphics execution core implemented in 22 nm trigate process uses per-die tunable replica circuit (TRC) to monitor delay degradation due to ITD and actual aging conditions. TRC triggers adaptive voltage scaling to dynamically adjust $V_{\mathrm {CC}}$ as needed during run time to maintain correct operation at minimum additional voltage. Measured data show up to 33% (14%) energy savings at 0.4 V (0.8 V) compared with baseline scheme. The TRC is also utilized in a dynamic power gating (DPG) scheme to lower energy overhead due to fast droop guard band. DPG introduces a load line effect during normal operation, thus saving energy, while deactivating this load line upon droop detection by the TRC to maintain ISO performance as baseline. Silicon data show that DPG can improve energy efficiency by 14.5% (7%) at 0.8 V (0.6 V).

The phenomenon of four-wave mixing in passive optical networks with wavelength-division multiplexing of channels has been studied. This paper presents the results of modeling the distribution of combination frequencies over the spectrum as a function of the number of channels and the channel frequency spacing. To suppress crosstalk between the channels at combination frequencies, it is proposed to divide the spectrum into two parts and select a guard band between them. The effect of combination frequencies on the signal transmission quality is considered as a function of the channel power, channel frequency spacing, and transmission length.

A secret key can be generated between two legitimate parties from observations of the common wireless channel. However, key disagreement usually occurs due to the estimation errors. Considering a guard band, the key disagreement rate (KDR) is firstly derived in a closed-form expression. Although increasing the size of the guard band can decrease KDR; the length of the raw key bit sequence is also shortened. To evaluate such an effect, the raw key generation rate is defined and derived. The simulation results verify the theoretical analysis and are useful for the determination of pilot power and guard band size.

Earth station in motion (ESIM) is a technology that provides wireless communication to users at their locations and is considered to operate at 27.5-29.5 GHz. The next-generation mobile communication service, 5G, is expected to operate at 24.25-27.5 GHz. These systems can experience interference because both the frequency bands are contiguous. The possibility of the adjacent channel compatibility between an ESIM and 5G should be verified by an interference analysis. However, ESIMs are mounted on ships, aircraft, and land vehicles. Therefore, the analysis methods and scenarios should be applied differently. We propose orthogonal frequency division multiplexing (OFDM) waveforms of an ESIM for their coexistence. Because OFDM has a lower out-of-band emission (OOBE) than a single carrier signal, this proposed approach can save frequency resources. Minimum coupling loss (MCL) and Monte Carlo (MC) methods are used to obtain the minimum separation distance and guard band according to the frequency-dependent rejection for determining the adjacent channel compatibility.

By applying the windowing process, the sharper OOB spectral characteristics can be obtained, which can be used for the reduction of guard band between the operators frequency assignment and can save the very valuable frequency resources. WR-OFDM (window and reconstruction – orthogonal frequency division multiplex) system is proposed to upgrade the existing CP-OFDM system for research of mobile communication system after 5th generation. We have applied window function and analyzed performance change according to window length. This system can improve efficiency of spectrum resources by reducing gap from adjacent channels. The WR-OFDM system complements disadvantage that OOB (out-of-band power of the existing CP-OFDM system is high. In transmitter, the window function is applied to lower OOB power and receiver reconstructs damaged data through restructuring process. In this way, OOB power can be reduced without additional time resources such as time extension. However, in WR-OFDM system, partial interference occurs by applying the window function and multipath delay signal in multipath channel. In this study, we investigated effect of window length on BER performance in WR-OFDM system and obtained the interaction formula between window length and multipath delay signal through simulation with each tap of multipath delay signal. Also, it can be confirmed that adjusting the window length in the multipath channel can mitigate trade-off characteristics between OOB power reduction and BER performance.

Sinc-shaped Nyquist pulses have a rectangular spectrum. In the spectral domain, adjacent Nyquist wavelength division multiplexed (WDM) channels can be multiplexed without any guard band. Theoretically, they can be used to transmit the maximum possible symbol and data rate. The demultiplexing of channels requires filters with transfer functions that are as close as possible to rectangular shapes. Here we present the successful demultiplexing of rectangular-shaped optical Nyquist dense wavelength division multiplexed channels, modulated with an advanced modulation format, with an eight-channel integrated silicon photonics device.

The next generation communication systems are evolving towards an increased flexibility in different aspects. Enhanced flexibility is the key in order to address diverse requirements. This paper presents the significance of adaptive guards considering a windowed-OFDM system which supports a variety of services operating asynchronously under the same network. The windowing approach requires a guard duration to suppress the out-of-band emissions (OOBE), and the guard band is required to handle the adjacent channel interference (ACI) along with the windowing. The guards in both time and frequency domains are optimized with respect to the use case and power offset between the users. To fully exploit and further increase the potential of adaptive guards, an interference-based scheduling algorithm is proposed as well. The results show that the precise design that facilitates such flexibility reduce the guards significantly and boost the spectral efficiency., Comment: 5 pages, 6 figures, 5 tables; accepted version (The URL for the final version: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8292413&isnumber=8292162)

Among the theory and design of oversampled nonuniform filter banks (NUFBs), most of the existing works only consider the cases with integer decimators, and up to now the issue with rational sampling factors has not been discussed yet. In this paper, we generalize the partial modulation technique to realize arbitrary rational frequency partitioning of oversampled NUFBs with highly desired linear-phase (LP) property. Further for the subbands with sampling factors violating the guard band restriction, a phase-modification scheme is derived to avoid uneliminable large aliasing and meanwhile preserving the LP characteristics of shifted analysis/synthesis filters. By using the proposed method, the design issue of LP oversampled NUFBs can be reduced to that of several prototypes, decreasing the design complexity largely. As illustrated by examples, the proposed algorithm is more general in terms of arbitrary rational decimation and thus has broad application prospects.

In this paper, we propose an emergency wake-up alert system (EWAS) for providing accurate and rapid emergency information. The proposed system can provide an emergency wake-up alert service without an additional frequency allotment by utilizing the guard band of the Advanced Television Systems Committee (ATSC) Terrestrial Digital Television (DTV) system. The design target of the proposed system is to match the indoor reception coverage of EWAS with the outdoor reception coverage of the ATSC DTV system. To achieve this, the proposed system should be about 35.65 dB more robust than the ATSC DTV system. The simulation results show that the proposed system offers an emergency wake-up alert service supporting a data rate of up to 23 bps.

Offset quadrature amplitude modulation-based orthogonal frequency division multiplexing (OFDM) systems cannot be directly combined with the Alamouti code because of the intrinsic imaginary interference. In this paper, we propose a block-wise space-frequency block coding (SFBC) scheme and a block-wise space-time block coding (STBC) scheme for offset quadrature amplitude modulation-based OFDM systems, which achieve bit error rate performances that are close to OFDM systems. The proposed schemes satisfy the orthogonality condition of the Alamouti code in the complex field with guard band/intervals. To improve the spectral efficiency of the block-wise SFBC scheme, we also consider the case without the guard band. It is observed that only the two innermost subcarriers do not satisfy the complex orthogonality condition when the guard band is removed. Then, a simple equalization scheme is proposed to independently equalize the two innermost subcarriers. Simulation results show that the block-wise SFBC scheme works well under channels with mild-to-moderate frequency selectivity, and the block-wise (STBC ) scheme suffers less than 1 dB loss under severe frequency selective channels at the bit error rate of 10 − 3, when only a simple one tap zero-forcing equalizer is employed. Copyright © 2016 John Wiley & Sons, Ltd.