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This study suggests the optimization of the acceptance in testing from the economic point of view. For this purpose, a type of the global consumer's risk different from that expressed in JCGM 106 is used. The consumer's risk in this study considers the risk of market-available items, and may be helpful for the economical assessment. We have developed a mathematical expression of the revenue increasing by testing items under the existence of the measurement uncertainty. The acceptance can be optimized in terms of the maximization of the revenue. A simple but accurate approximate solution is given.

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.

Two-dimensional magnetic recording (TDMR), which combines shingled magnetic recording (SMR) with 2-D signal processing attracts attention from the hard disk drive industry. SMR is a magnetic recording system in order to increase the track density by writing tracks without the guard band. Therefore, the influences of writing and reading intertrack interferences (ITIs) deteriorate the quality of reproducing waveforms. Additionally, degradation of track due to overwriting and crosstalk from the adjacent tracks due to the width of reader sensitivity. The equalization using 2-D finite impulse response filter for the waveforms from three adjacent tracks is proposed as a method to reduce the influence of reading ITIs. In this paper, we evaluate the bit aspect ratio (BAR) in TDMR read/write channel under a specification of 4 Tb/in2 using bit error rate of the low-density parity-check (LDPC) coding and iterative decoding system obtained by computer simulation. The results show that the suitable BAR in array head reading is 2.0.

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.

In this paper, a novel seamless guard band (SGB) technique for charge sharing mitigation is studied using 3-D TCAD numerical simulations. The simulations results in 65-nm twin-well bulk CMOS technology indicate that the SGB technique can not only mitigate the single-event transient pulsewidth greatly but also mitigate the charge sharing between logical nodes or logical cells significantly. The simulation results also indicate that the SGB technique is superior to the conventional guard band (GB) technique, for it is more beneficial for parasitic bipolar effect mitigation. Using SGB technique, the single-event double-transient (SEDT) generation is mitigated completely under low LET particle (LET $\le \text{40}\ \text{MeV}\cdot \text{cm}^{2}/\text{mg}$ ) radiation, and the SEDT pulsewidth is mitigated > 50% even with the LET of 80 $\text{MeV}\cdot \text{cm}^{2}/\text{mg}$ , which is > 25% from GB technique. Finally, the SGB technique can be applied to the construction of a radiation-hardened standard cell library conveniently, and its area penalty is 1–1.67 $\times$ , which is the same with that of the GB technique.

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.

In the last few years there has been a growing interest in Wireless Body Area Network (WBAN) due to its latency and enhance the health care features by continuously monitoring the condition of the patient and early identification of problems. A major difficulty has been occurring to design network such as Medium Access Control (MAC) protocol that primarily part of the WBANs for functioning in a well-organized way. Therefore, it limits the sensor node energy for Quality of Service (QOS) and life cycle of the network. Accordingly, this work introduces a Versatile Synchronization Guard Band Protocol (VSGP) namely VSGP, which deals with guard band (GB) in each time slot it reduces the interference of the transmitting signal and increase the efficiency of QOS and its energy. WBAN performed with more number of sensor nodes are connected to the coordinator. VSGP protocol is compared with two existing methods called Self Adaptive Guard Band (SAGB) and Traditional Guard Band protocol. Comparisons are made with time and packet flow of each transmission and energy per packet flow.

IMT-2020 (5G) is a solution to addressing continuous increased in global data traffic. Amongst candidate bands to be allocated for IMT-2020 mid bands, the extended C-band (±3.5 GHz) becomes favorite due to its advantages in terms of both technology and economy. Thus, many countries identify it as one of the candidate bands for IMT-2020. In Indonesia, C-Band and extended C-band are primarily occupied by Fixed-Satellite Services (FSS) because of its robustness to heavy rain. This study investigates the feasibility for IMT-2020 and FSS systems to coexist in the extended-C band by analyzing the possibility of interference from IMT-2020 base stations to FSS earth stations using deterministic calculations. The calculations use FSS earth station and IMT-2020 base station trial parameters in Indonesia. The study results show that under any circumstances, co-channel scenario is very challenging since it requires very significant separation distance between the two systems. By employing off-axis angle of 50°, IMT 2020 base station need to be separated at least 78 km away from any FSS earth station. On the contrary, in the adjacent channel scenario, two systems are possible to coexist with a small protection distance (about 1 km) and a guard band of 10 MHz. The protection distance can be minimized by directing the IMT-2020 base station transmitting antenna away from the direction of the FSS earth station antenna.

This paper was studied about an application behavior of coexistence LTE-TDD and LTE-FDD networks, which used by network provider for optimal the capacity of networks. The results shown bandwidth, packets size and type of protocols are affected the system throughput. The power allocation and guard band techniques are improve the behavior of coexistence network by 30%.

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.

The critical path delay and, as a consequence, the maximum operating frequency of a digital system are dependent on the supply voltage, so is its power consumption. Typically, voltage guard bands are added in order to improve reliability, at the expense of power efficiency. It has been shown that error detection and correction (EDAC) techniques can be used to mitigate the effects of the reduced safety margins. This Ph.D. project aims to develop a MPSoC capable of self regulate its operating voltage by monitoring the error rate reported by a EDAC system, virtually eliminating voltage safety margins. Literature review and preliminary experiments supports the viability of this approach, motivating further investigation.

Mobile network Operator is implemented coexistence LTE-TDD and LTE-FDD network, this technique used to improve the system capacity. The adjacent cell interference or ACI caused by these coexisting networks, which affected to the network performance. This paper investigates the load sharing technique to optimal the capacity of coexistence LTE network. Results show 4:6 of FDD and TDD user ratio that give maximum system throughput and comparing with power allocation and guard band technique will describe in this paper.

As redes ópticas elásticas compõem uma infraestrutura de rede capaz de suportar a grande demanda de tráfego de dados das redes de alta velocidade. Um dos problemas que devem ser solucionados para garantir o bom funcionamento da rede é o chamado Routing, Modulation Level and Spectrum Allocation (RMLSA). Este trabalho tem como objetivo propor uma nova abordagem para esse problema por meio do uso de um algoritmo para provisão de banda de guarda adaptativa, baseado no nível de utilização da rede, chamado de GBUN. O desempenho do algoritmo proposto é comparado com algoritmos que usam valores de banda de guarda fixa e a proposta adaptativa AGBA. Os resultados mostram que o algoritmo proposto apresenta um melhor desempenho em termos de probabilidade de bloqueio de banda para os cenários estudados.

The basis of generating secret key from the common wireless channel at two communication parties is reciprocity. However, due to non-simultaneous measurements and unavoidable estimation error, bias always exists and key disagreement occurs. In this paper, performance analysis and improvements for key generation exploiting imperfect channel statement information (CSI) is studied. Firstly, the closed-form expression for key disagreement rate (KDR) is derived to evaluate the key mismatch caused by time delay and estimation error. Secondly, the energy efficiency involving power allocation between key generation and private data transmission is presented. After that, a neural network based prediction (NNBP) algorithm is proposed to improve the key consistency. Simulation results verify the theoretical analysis and show that NNBP achieves significant improvements. And it's interesting to find that NNBP algorithm achieves a higher performance gain in low signal-to-noise ration (SNR) and high delay condition, which is different from other methods, like guard band based quantizer (GBBQ).

In this paper, we investigate binary frequency shift keying (BFSK) over ambient OFDM signals. By cycling through a sequence of antenna loads providing different phase shifts at the tag, we are able to unidirectionally shift the ambient spectrum either up or down in frequency allowing the implementation of BFSK. We exploit the guard band and the orthogonality of the OFDM subcarriers to avoid both direct-link and adjacent channel interference. Different from energy detection based techniques which suffer from asymmetric error probabilities, the proposed scheme has symmetric error probabilities. Furthermore, we analyze the error performance of the optimal noncoherent detector and obtain an exact expression for the average probability of error. Finally, simulation results corroborate our analysis and show that the proposed scheme outperforms energy detection based schemes available in the literature by up to 3 dB.

Narrow-Band Internet of Things (NB-IoT) offers low power and wide coverage for IoT services which reuse existing Long Term Evolution (LTE) technology. Coverage enhancement at weak signal area may be achieved by channel repetition to improve signal quality. In this paper, the performance of NB-IoT is evaluated for three different modes of deployments by repeating the downlink physical channel. It is proved that the increase in the number of repetitions will give better performance of NB-IoT system. It also shows that the standalone and guard band modes perform better compared to in-band mode.

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.

Spatial division multiplexing (SDM) can support the capacity demand increase in short-range optical link, but the communication is affected by the intermodal crosstalk. In order to target a low-cost energy-efficient solution, we propose to exploit direct modulation and direct detection without MIMO post-processing in a mode division multiplexed (MDM) system. We theoretically analyze the frequency distribution of the crosstalk contributions taking into account that directly modulated sources at the same nominal wavelength are actually characterized by a certain frequency shift. Our model demonstrates that this shift originates a non-uniform beating noise in the frequency domain due to the intermodal crosstalk. We propose to exploit discrete multitone modulation and a guard band in the multicarrier spectrum to cope with the non-uniform crosstalk issue for typical crosstalk values due to present commercial multi-plane light conversion MUX/DEMUX devices and propagation in few few-mode fiber (FMF) kilometers. The model is validated by comparing simulations and experimental results in the case of a 2-mode MDM system. We demonstrate in a pure SDM scenario that, with respect to single mode transmission, the capacity can be increased of 2.3 times in a 10-km FMF link with 4-modes exploiting direct detection, limited-bandwidth directly modulated lasers and commercial mode MUX/DEMUXs.

In this paper, a crosstalk-mitigated transmission scheme in arrayed waveguide grating router (AWGR) based two dimensional infrared beam-steered optical wireless communication (OWC) system is proposed for indoor applications. By creating polarization orthogonality between the odd and even AWGR channels, high crosstalk tolerance between spectrally overlapping AWGR channels is realized experimentally. Because two signals with orthogonal polarization states will not beat with each other in a photodiode. The optical crosstalk on the orthogonal polarization state will not generate a beat note upon detection and thus crosstalk in the electrical domain can be largely reduced. Reduced crosstalk leads to a reduction in the required spectral guard band and/or an improved tolerance to spectral overlap, which allows higher spectral efficiency. Moreover, the port number of an AWGR can be increased by simply shortening the spatial gap between adjacent output waveguides on a chip. The higher port number can support the high spatial resolution of the steered OWC system. This technique can also tolerate the wavelength misalignment between AWGRs and lasers, which relaxes the design of low crosstalk AWGRs and high wavelength stable lasers. A 20 Gbit/s data rate, four-level pulse amplitude modulation OWC transmission has been experimentally demonstrated over 1.2-m free-space link. The experimental results show that the proposed scheme can maintain stable, low crosstalk impact with an apparent improvement of the responsivity.

Shared frequency operation of different radio systems causes the need to investigate electromagnetic compatibility conditions for these systems. According to the National Frequency Allocation Table the operation of communication facilities of LTE technology and space operation service is allowed in the 2.3–2.4 GHz band. Conditions ensuring joint action of communication facilities of LTE technology and space operation service in shared frequency band are considered. A procedure to evaluate the required frequency–distance separation between means of these different radio services and the necessary guard band is presented.

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)

On the basis of coherent optical orthogonal frequency-division-multiplexing (CO-OFDM), CO-OFDM/ offset quadrature amplitude modulation (CO-OFDM/OQAM) improves the spectrum efficiency by utilizing specially designed filter banks to eliminate the cyclic prefix (CP) inserted between consecutive OFDM blocks and decreases the demanding of guard band between two channels, being a promising candidate for the next generation optical transmission link. Due to the relaxation of the orthogonal condition from the complex field to the real field, chromatic Dispersion (CD) and polarization mode dispersion (PMD) bring serious intrinsic imaginary interference (IMI) to an optical OFDM/OQAM system. Channel estimation schemes based on the interference approximation method (IAM) have been proved to be effective in suppressing the IMI with low complexity. For the IAMs, increasing the power of the pseudo pilot could decrease the effects of amplified spontaneous emission (ASE) noise and other frequency domain residual error on the channel estimation accuracy. In most of the previous reported IAM works, pilot blocks were designed according to the structure of the center pilot block loaded, while the two side pilots nulled for simplicity. However, the power of the pseudo pilot under this method did not reach the maximum, resulting in non-optimal channel estimation accuracy. In this paper, channel estimation method based on the combined phase offset (CMPO) is proposed and systematically discussed. For the proposed method, three consecutive full loaded blocks are treated as the pilot blocks and the optimal pilot structure have been obtained by utilizing the maximum likelihood algorithm. As validated by numerous Montel Carlo simulations results, system robustness against IMI, phase noised induced interference, and nonlinear effect have been improved significantly, thanks to CMPO.

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.

This paper computes the distortion power at the receiver side of an FBMC/OQAM-based OFDMA uplink channel under strong frequency selectivity and/or user timing errors. More precisely, it provides a distortion expression that is valid for a wide class of prototype pulses (not necessarily perfect-reconstruction ones) when the number of subcarriers is sufficiently large. This result is a valuable instrument for analyzing how users interfere to one another and to justify, formally, the common choice of placing an empty guard band between adjacent users. Interestingly, the number of out-band subcarriers contaminated by each user only depends on the prototype pulses and not on the channel nor on the equalizer. To conclude, the distortion analysis presented in this paper, together with some simulation results for a realistic scenario, also provide convincing evidence that FBMC/OQAM-based OFDMA is superior to classic circular-prefix OFDMA in the case of asynchronous users., 27 pages, 12 figures; new version corrects few minor typos and reports final reference

This paper assumes that Long Term Evolution (LTE) will be deployed in TV White Spaces (TVWSs). Beamforming is a technology that is applied to an LTE base station (BS) for reducing interference impact of LTE on DTV. A simulation method based on Monte Carlo is proposed to evaluate the interference probability in DTV receivers in the case of interference impact of LTE BS on DTV receiver. As per simulation results, the interference impact of LTE BS on DTV receiver is efficiently mitigated and the guard band remarkably reduced when LTE BS uses beamforming.