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Recently, there has been an increasing interest in exploiting interference cancelation to support multiple adjacent concurrent transmissions instead of avoiding interference through scheduling. In line with these efforts, this paper propose an interference coordinated routing (ICR) scheme for wireless multi-hop networks to achieve more transmission concurrence, and thus lower the end-to-end delay. The proposed ICR scheme firstly constructs an initial path by the interference-aware routing algorithm, which captures the end-to-end latency and spatial resource cost as the routing metrics. Then, to analyze the feasibility of concurrent transmission for a given link set, we consider the interference coordination and formulate the concurrent transmission of multiple links as a linear programming (LP) problem. The solution to the LP problem indicates the power allocation. Finally, a distributed guard zone based selection (GBS) algorithm is further proposed to iteratively explore the maximum feasible link set for each time slot. The selected links are simultaneously active for packet transmission with the allocated power in the current time slot, and the remaining links will be put off to the next. Simulation results confirm that ICR reduces the end-to-end delay by 9.16% to 73.82%, and promotes better transmission concurrence compared with the existing schemes.

Background Evidence has been shown that circular RNAs (circRNAs) play a vital role during the development of ovarian cancer. However, the mechanism by which circEXOC6B regulates tumorigenesis of ovarian cancer remains unknown. Thus, this study aimed to investigate the role of circEXOC6B during the progression of ovarian cancer. Materials and methods The dual-luciferase reporter system assay was used to determine the interaction between circEXOC6B, miR-421 and RUS1 in ovarian cancer, respectively. CCK8 and colony formatting were used to evaluate cell proliferation. Meanwhile, the expressions of RSU1, PINCH1 and ILK in SKOV3 cells were detected with Western blot. Results Downregulation of circEXOC6B markedly promoted the proliferation and invasion in A2780 cells. In contrast, upregulation of circEXOC6B significantly inhibited the proliferation and invasion in SKOV3 cells. Moreover, overexpression of circEXOC6B obviously induced the apoptosis of SKOV3 cells. Furthermore, luciferase reporter assay identified that miR-421 was the potential miRNA binding of circEXOC6B, and RUS1 was the potential binding target of miR-421. Mechanism analysis indicated that upregulation of circEXOC6B increased the level of RUS1 by acting as a competitive "sponge" of miR-421. Conclusion In this study, we found that circEXOC6B suppressed the growth of ovarian cancer cells through upregulating RSU1 partially via sponging miR-421. Therefore, circEXOC6B might be a potential target for the treatment of ovarian cancer.

Accurate estimation of channel log-likelihood ratio (LLR) is crucial to the decoding of modern channel codes like turbo, low-density parity-check (LDPC), and polar codes. Under an additive white Gaussian noise (AWGN) channel, the calculation of LLR is relatively straightforward since the closed-form expression for the channel likelihood function can be perfectly known to the receiver. However, it would be much more complicated for heterogeneous networks where the global noise (i.e., noise plus interference) may be dominated by non-Gaussian interference with an unknown distribution. Although the LLR can still be calculated by approximating the distribution of global noise as Gaussian, it will cause performance loss due to the non-Gaussian nature of global noise. To address this problem, we propose to use bi-Gaussian (BG) distribution to approximate the unknown distribution of global noise, for which the two parameters of BG distribution can easily be estimated from the second and fourth moments of the overall received signals without any knowledge of interfering channel state information (CSI) or signaling format information. Simulation results indicate that the proposed BG approximation can effectively improve the word error rate (WER) performance. The gain of BG approximation over Gaussian approximation depends heavily on the interference structure. For the scenario of a single BSPK interferer with a 5 dB interference-to-noise ratio (INR), we observed a gain of about 0.6 dB. The improved LLR estimation can also accelerate the convergence of iterative decoding, thus involving a lower overall decoding complexity. In general, the overall decoding complexity can be reduced by 25 to 50%.

This letter studies the ergodic mutual information (EMI) of keyhole multiple-input multiple-output channels having finite-alphabet input signals. The EMI is first investigated for single-stream transmission considering both cases with and without the channel state information at the transmitter. Then, the derived results are extended to the scenario of multi-stream transmission. Asymptotic analyses are performed in the regime of high signal-to-noise ratio (SNR). The high-SNR EMI is shown to converge to a constant with its rate of convergence determined by the diversity order. On this basis, the influence of the keyhole effect on the EMI is discussed. The analytical results are validated by numerical simulations., Comment: 5 figures

Physical layer security is investigated over mixture Gamma (MG) distributed fading channels with discrete inputs. By the Gaussian quadrature rules, closed-form expressions are derived to characterize the average secrecy rate (ASR) and secrecy outage probability (SOP), whose accuracy is validated by numerical simulations. To show more properties of the finite-alphabet signaling, we perform an asymptotic analysis on the secrecy metrics in the large limit of the average signal-to-noise ratio (SNR) of the main channel. Leveraging the Mellin transform, we find that the ASR and SOP converge to some constants as the average SNR increases and we derive novel expressions to characterize the rates of convergence. This work establishes a unified and general analytical framework for the secrecy performance achieved by discrete inputs., 8 figures 6 pages

Channel modeling is crucial to the development and evaluation of modern wireless communication systems including satellite communication system, since there might be critical safty-of-life applications. Also, the channel model is of great importance to the performance evaluation of mobile communication systems. In recent years, encouraged by the widely application of unmanned aerial vehicles, the research on channel modeling for aerial and aeronautical communications attract lots of interests. In the published articles, stationary and non-stationary channel models have been developed for air-to-ground communications based on regular shaped geometry-based stochastic model (RS-GBSM). The modeling of air-to-air or satellite-to-aircraft (S2A) communication is still quite simple or completely lacking. For obtaining more precise model of S2A channel, this paper presents an analytical non-stationary S2A channel mode based on RS-GBSM with considerations on line-of-sight path, specular reflection path, and ground scattering path. Analytical expressions of the channel impulse responses, the transfer functions, the auto-correlation functions, and the Doppler power spectrum density based on 3-path model are derived and simulated. Also, the distributions of the path antennation, the path delay, and the normalized Doppler shift based on uniform distribution of the scatterers are derived, simulated and fitted.

With the rapid growing demand for transmission rate, transmission security is becoming increasingly important. This paper proposes a novel scheme aiming at transmission security enhancement on the basis of the spatial modulation technology. In the proposed scheme, the transmitter maps the information bits to the index of a receive antenna, then a precoding vector is randomly selected in the null space of the targeted antenna. Due to the randomness of the precoding vector, it's difficult for the eavesdropper in unknown locations to detect the index of the targeted antenna using maximum-likelihood detection, hence its receiving performance can be greatly degraded compared with the legitimate receiver. Both theoretical analysis and simulation results verified the secure enhancement performance of the proposed scheme. Moreover, unlike most of the existing schemes which require that the transmitter should equip more antenna than the receiver, our scheme works well even if the transmitter has less antennas than the receiver.

To provide system design insights for practical communication systems equipped with the frequency diverse array (FDA), this letter investigates the secrecy performance of FDA systems exploiting finite-alphabet inputs over fluctuating two-ray (FTR) fading channels. More specifically, closed-form expressions for the average secrecy rate (ASR) and the secrecy outage probability (SOP) are derived, while their correctness is confirmed by numerical simulations. In addition, we perform asymptotic analysis to quantify the secrecy performance gap between Gaussian and finite-alphabet inputs, for a sufficiently large average signal-to-noise ratio (SNR) of the main channel. Compared with Gaussian inputs-based research, this letter focuses on practical scenarios which sheds lights on properties of FDA systems.

This paper studies the secrecy performance of multiple-input multiple-output (MIMO) wiretap channels, also termed as multiple-input multiple-output multiple-eavesdropper (MIMOME) channels, under transmit antenna selection (TAS) and BPSK/QPSK modulations. In the main channel between the transmitter and the legitimate receiver, a single transmit antenna is selected to maximize the instantaneous Signal to Noise Ratio (SNR) at the receiver. At the receiver and the eavesdropper, selection combining (SC) is utilized. Additionally, suppose that the transmitted message is modulated by BPSK/QPSK modes. We first derive the closed-form approximated expression for the ergodic secrecy rate under Rayleigh fading, assuming that the channel state information of the eavesdropper (CSIE) is available at the transmitter. Next, analytical formulas for the approximated and asymptotic secrecy outage probability are also developed when CSIE is unavailable (NCSIE). Simulation results are provided to demonstrate the approximation precision of the derived results above. Furthermore, the asymptotic results reveal that the secrecy diversity order degrades into 0 due to the finite-alphabet inputs, which is totally different from that driven by the Gaussian inputs.

Unmanned aerial vehicle (UAV) communication system equipped with multiple input and multiple output (MIMO) antennas has been recognized as an efficient technique for obtaining high spectral efficiency. To improve the system capacity in UAV communication scenario, this paper investigates the user clustering and downlink user scheduling strategy. We first develop a channel correlation based K-means algorithm for user clustering. Furthermore, to diminish intergroup interference, a greedy user scheduling algorithm driven by the K-means clustering strategy, is devised to appropriately select the users with low-correlated channels to schedule at the same time slot. Simulation results are provided to demonstrate the superior performance of the proposed scheduling algorithm over conventional method. It is observed that the presented K-means aided algorithm can achieve near maximum average sum rate with much lower computational complexity.