This letter proposes a blind phase compensation method for the phase errors in the Multi-Carrier Multiple-input multiple-output (MIMO) radar, which decouples the range and DOA coupling. The phase errors under the Linear Frequency Modulated Continuous Waveform (LFMCW) scheme are firstly derived, followed with the signal processing steps. Further, multiple targets with certain velocities can be handled uniformly without pre-knowledge of the actual range information of the targets. The evaluations of the DOA estimation performance are carried out through simulations, which validate the effectiveness of the proposed method.

In this letter, the performance of a state-of-the-art deep learning (DL) algorithm in [5] is analyzed and evaluated for orthogonal frequency-division multiplexing (OFDM) receivers, in the presence of harmonic spur interference. Moreover, a novel spur cancellation receiver structure and algorithm are proposed to enhance the traditional OFDM receivers, and serve as a performance benchmark for the DL algorithm. It is found that the DL algorithm outperforms the traditional algorithm and is much more robust to spur carrier frequency offset.

This paper proposes an energy efficiency (EE) maximized resource allocation (RA) algorithm in orthogonal frequency division multiple access (OFDMA) downlink networks with multiple relays, where a novel opportunistic subcarrier pair based decode-and-forward (DF) protocol with beamforming is used. Specifically, every data transmission is carried out in two consecutive time slots. During every transmission, multiple parallel paths, including relayed paths and direct paths, are established by the proposed RA algorithm. As for the protocol, each subcarrier in the 1st slot can be paired with any subcarrier in 2nd slot to best utilize subcarrier resources. Furthermore, for each relayed path, multiple (not just single or all) relays can be chosen to apply beamforming at the subcarrier in the 2nd slot. Each direct path is constructed by an unpaired subcarrier in either the 1st or 2nd slot. In order to guarantee an acceptable spectrum efficiency, we also introduce a minimum rate constraint. The EE-maximized problem is a highly nonlinear optimization problem, which contains both continuous, discrete variables and has a fractional structure. To solve the problem, the best relay set and resource allocation for a relayed path are derived first, then we design an iterative algorithm to find the optimal RA for the network. Finally, numerical experiments are taken to demonstrate the effectiveness of the proposed algorithm, and show the impact of minimum rate requirement, user number and circuit power on the network EE.

Among the five carrier aggregation (CA) deployment scenarios, the most preferred scenario is Scenario 1, which maximizes CA gain by fully overlapping a primary cell (PCell) and one or more secondary cells (SCells). It is possible since the same frequency band is used between component carriers (CCs) so nearly the same coverage is expected. However, Scenario 1 cannot guarantee high throughput in multi-radio access technology carrier aggregation (multi-RAT CA) which is actively being researched. Different carrier frequency characteristics in multi-RAT CA makes it hard to accurately match different frequency ranges. If the ranges of PCell and SCell differ, high throughput may not be obtained despite the CA operation. We found a coverage mismatch of approximately 37% between the PCell and SCell in the deployed network and realized a reduced CA gain in those areas. In this paper, we propose a novel PCell change approach named “PCell frequency switching (PFS)” to guarantee high throughput against cell coverage mismatch in multi-RAT CA deployment scenario 1. The experiment results show that the throughput increased by 9.7% on average and especially by 80.9% around the cell edge area when PFS is applied instead of the legacy CA handover operation.

The electric properties of a field-effect transistor not only depend on gate surface sidewall but also on channel orientation when applying channel stain engineering. The change of the gate surface and channel orientation through the rotated FinFETs provides the capability to compare the orientation dependence of performance and reliability. This study characterized the <100> and <110> channels of FinFETs on the same wafer under tensile and compressive stresses by cutting the wafer into rectangular silicon pieces and evaluated their piezoresistance coefficients. The piezoresistance coefficients of the <100> and <110> silicon under tensile and compressive stresses were first evaluated based on the current setup. Tensile stresses enhance the mobilities of both <100> and <110> channels, whereas compressive stresses degrade them. Electrical characterization revealed that the threshold voltage variation and drive current degradation of the {100} surface were significantly higher than those of {110} for positive bias temperature instability and hot carrier injection with equal gate and drain voltage (VG=VD). By contrast, insignificant difference is noted for the subthreshold slope degradation. These findings imply that a higher ratio of bulk defect trapping is generated by gate voltage on the <100> surface than that on the <110> surface.

A multi-carrier and blind shift-frequency jamming(MCBSFJ) against the pulsed compression radar with order-statistic (OS) constant false alarm rate (CFAR) detector is proposed. Firstly, according to the detection principle of the OS-CFAR detector, the design requirements for jamming signals are proposed. Then, some key parameters of the jamming are derived based on the characteristics of the OS-CFAR detector. As a result, multiple false targets around the real target with the quantity, amplitude and space distribution which can be controlled are produced. The simulation results show that the jamming method can reduce the detection probability of the target effectively.

Electric field induced optical second harmonic generation (EFISHG) measurement at the laser wavelength of 1000nm and 1080nm is conducted to investigate the carrier behaviors in PCPDTBT and PC71BM bulk heterojunction organic solar cells (OSCs). We find that the response time for electrode charging through the external circuit in +1V and -1V are almost identical but the response time for the Maxwell-Wagner-type interfacial charging is different in +1V or -1V. We find that the accumulated charges of PC71BM is more than the accumulated charges of PCPDTBT and consequently affects the efficiency of the bulk heterojunction OSCs.

This letter proposes a new positioning method for WLAN (Wireless Local Area Network) systems based on a principle of the RTK-GPS (Real Time Kinematic-Global Positioning System). The proposed method collects observations of the carrier phase at access points for a double phase difference of the RTK-GPS. We show a numerical example for evaluations of the proposed method considering the measurement error by computer simulations.

Asymmetrically designed polycrystalline silicon (poly-Si) thin film transistors (TFT) were fabricated and investigated to suppress kink effect and to improve electrical reliability. Asymmetric dual channel length poly-Si TFT (ADCL) shows the best reduction of kink and leakage currents. Technology computer-aided design simulation proves that ADCL can induce properly high voltage at floating node of the TFT at high drain-source voltage (VDS), which can mitigate the impact ionization and the degradation of the transconductance of the TFT showing high reliability under the hot carrier stress.

This paper derives highly accurate and effective closed-form formulas for the average upper bound on the pairwise error probability (PEP) of the multi-carrier index keying orthogonal frequency division multiplexing (MCIK-OFDM) system with low-complexity detection (i.e., greedy detection) in two-wave with diffuse power (TWDP) fading channels. To be specific, we utilize an exact moment generating function (MGF) of the signal-to-noise ratio (SNR) under TWDP fading to guarantee highly precise investigations of error probability performance; existing formulas for average PEP employ the approximate probability density function (PDF) of the SNR for TWDP fading, thereby inducing inherent approximation error. Moreover, some special cases of TWDP fading are also considered. To quantitatively reveal the achievable modulation gain and diversity order, we further derive asymptotic formulas for the upper bound on the average PEP. The obtained asymptotic expressions can be used to rapidly estimate the achievable error performance of MCIK-OFDM with the greedy detection over TWDP fading in high SNR regimes.

In this paper, we present self-interference (SI) cancellation techniques in the digital domain for in-band full-duplex systems employing orthogonal frequency division multiple access (OFDMA) in the downlink (DL) and single-carrier frequency division multiple access (SC-FDMA) in the uplink (UL), as in the long-term evolution (LTE) system. The proposed techniques use UL subcarrier nulling to accurately estimate SI channels without any UL interference. In addition, by exploiting the structures of the transmitter imperfection and the known or estimated parameters associated with the imperfection, the techniques can further improve the accuracy of SI channel estimation. We also analytically derive the lower bound of the mean square error (MSE) performance and the upper bound of the signal-to-interference-plus-noise ratio (SINR) performance for the techniques, and show that the performance of the techniques are close to the bounds. Furthermore, by utilizing the SI channel estimates and the nonlinear signal components of the SI caused by the imperfection to effectively eliminate the SI, the proposed techniques can achieve SINR performance very close to the one in perfect SI cancellation. Finally, because the SI channel estimation of the proposed techniques is performed in the time domain, the techniques do not require symbol time alignment between SI and UL symbols.

In this letter, based on orthogonal Golay sequence sets and orthogonal matrices, general constructions of zero correlation zone (ZCZ) aperiodic complementary sequence (ZACS) sets are proposed. The resultant ZACSs have column sequence peak-to-mean envelop power ratio (PMEPR) of at most 2, and the parameters of the sequence sets are optimal with respect to the theoretical bound. The novel ZACS sets are suitable for approximately synchronized multi-carrier CDMA (MC-CDMA) communication systems.

Multiple Subcarrier Multiple Access (MSMA) enables concurrent sensor data streamings from multiple wireless and batteryless sensors using the principle of subcarrier backscatter used extensively in passive RFID. Since the interference cancellation performance of MSMA depends on the Signal to Interference plus Noise Ratio of each subcarrier, the choice of channel allocation scheme is essential. Since the channel allocation is a combinatorial problem, obtaining the true optimal allocation requires a vast amount of examinations which is impracticable in a system where we have tens of sensor RF tags. It is particularly true when we have variable distance and variable bandwidth sensor RF tags. This paper proposes a channel allocation scheme in the variable distance and variable bandwidth MSMA system based on a newly introduced performance index, total contamination power, to prioritize indecision cases. The performance of the proposal is evaluated with existing methods in terms of average communication capacity and system fairness using MATLAB Monte Carlo simulation to reveal its advantage. The accuracy of the simulation is also verified with the result obtained from the brute force method.

This paper presents an overview of the advance of the China millimeter-wave multiple gigabit (CMMG) wireless local area network (WLAN) system which operates in the 45 GHz frequency band. The CMMG WLAN system adopts the multiple antennas technologies to support data rate up to 15Gbps. During the progress of CMMG WLAN standardization, some new key technologies were introduced to adapt the millimeter-wave characteristic, including the usage of the zero correlation zone (ZCZ) sequence, a novel lower density parity check code (LDPC)-based packet encoding, and multiple input multiple output (MIMO) single carrier transmission. Extensive numerical results and system prototype test are also given to validate the performance of the technologies adopted by CMMG WLAN system.

The combination of GPS measurements with the dynamic model via a Kalman filter or an extended Kalman filter, also known as GPS based reduced dynamic orbit determination (RDOD) techniques, have been widely used for accurate and real time navigation of satellites in low earth orbit (LEO). In previous studies, the GPS measurement noise variance is empirically taken as a constant, which is not reasonable because of insufficient prior information or dynamic environment. An improper estimate of the measurement noise may lead to poor performance or even divergence of the filter. In this letter, an adaptive extended Kalman filter (AEKF)-based approach using GPS dual-frequency pseudo-range measurements is presented, where the GPS pseudo-range measurement noise variance is adaptively estimated by the Carrier to Noise Ratio (C/N0) from the tracking loop of GPS receiver. The simulation results show that the proposed AEKF approach can achieve apparent improvements of the position accuracy and almost brings no extra computational burdens for satellite borne processor.

Cognitive orthogonal frequency-division multiplexing (OFDM) systems are spectrum-efficient yet vulnerable to intercarrier interference (ICI), especially in high-mobility scenarios. In this paper, the energy efficiency optimization problem in high-mobility cognitive OFDM system is considered. The aim is to maximize the energy efficiency by adapting subcarrier bandwidth, power allocation and sensing duration in the presence of ICI, under the constraints of the total power budget of secondary networks, the probabilistic interference limits for the protection of primary networks, and the subcarrier spacing restriction for high-mobility OFDM systems. In order to tackle the intractable non-convex optimization problem induced by ICI, an ICI-aware power allocation algorithm is proposed, by referring to noncooperative game theory. Moreover, a near-optimal subcarrier bandwidth search algorithm based on golden section methods is also presented to maximize the system energy efficiency. Simulation results show that the proposed algorithms can achieve a considerable energy efficiency improvement by up to 133% compared to the traditional static subcarrier bandwidth and power allocation schemes.

This paper presents indoor and outdoor experiments that confirm 4-Gbps throughput based on 400-MHz bandwidth transmission when applying carrier aggregation (CA) with 4 component carriers (CCs) and 4-by-4 single-user multiple-in multiple-out multiplexing (MIMO) in the 15-GHz frequency band in the downlink of 5G cellular radio access. A new radio interface with time division duplexing (TDD) and radio access based on orthogonal frequency-division multiple access (OFDMA) is implemented in a 5G testbed to confirm ultra-high speed transmission with low latency. The indoor experiment in an entrance hall shows that the peak throughput is 4.3Gbps in front of the base station (BS) antenna where the reference signal received power (RSRP) is -40dBm although the channel correlation at user equipment (UE) antenna is 0.8. The outdoor experiment in an open-space parking area shows that the peak throughput is 2.8Gbps in front of a BS antenna with a high RSRP although rank 2 is selected due to the high channel correlation. The results also show that the average throughput of 2Gbps is achieved 120m from the BS antenna. In a courtyard enclosed by building walls, 3.6Gbps is achieved in an outdoor-to-outdoor environment with a high RSRP and in an outdoor-to-indoor environment where the RSRP is lower due to the penetration loss of glass windows, but the multipath rich environment contributes to realizing the low channel correlation.

This paper proposes approximated log likelihood ratios (LLRs) for single carrier millimeter-wave (mmW) transmission systems in the presence of phase noise. In mmW systems, phase noise on carrier wave signals in very high frequency bands causes severe performance degradation. In order to mitigate the impairments of phase noise, forward error correction (FEC) techniques, such as low density parity check (LDPC) code, are effective. However, if the probabilistic model does not capture the exact behavior of the random process present in the received signal, FEC performance is severely degraded, especially in higher order modulation or high coding rate cases. To address this issue, we carefully examine the probabilistic model of minimum mean square error (MMSE) equalizer output including phase noise component. Based on the derived probabilistic model, approximated LLR computation methods with low computational burden are proposed. Computer simulations confirm that the approximated LLR computations on the basis of the derived probabilistic model are capable of improving bit error rate (BER) performance without sacrificing computational simplicity in the presence of phase noise.

Zero correlation zone (ZCZ) aperiodic complementary sequence (ZACS) sets have potential applications in multi-carriers (MC) CDMA communication systems, which can support more users than traditional complementary sequence sets. In this letter, methods for constructing ZACS sets based on orthogonal matrices are proposed. The new constructions may propose ZACS sets with optimal parameters. The new ZACS sets can be applied in approximately synchronized MC-CDMA to remove interferences.

The impact of intersymbol interference (ISI) on single carrier frequency domain equalization with multiple input multiple output (MIMO-SCFDE) systems is severe. Most existing channel equalization methods fail to solve it completely. In this paper, given the disadvantages of the error propagation and the gap from matched filter bound (MFB), we creatively introduce a decision feedback equalizer with frequency-domain bidirectional noise prediction (DFE-FDBiNP) to tackle intersymbol interference (ISI) in MIMO-SCFDE systems. The equalizer has two-part equalizer, that is the normal mode and the time-reversal mode decision feedback equalization with noise prediction (DFE-NP). Equal-gain combining is used to realize a greatly simplified and low complexity diversity combining. Analysis and simulation results validate the improved performance of the proposed method in quasi-static frequency-selective fading MIMO channel for a typical urban environment.