Intelligent reflecting surface (IRS) can be densely deployed in complex environment to create cascaded line-of-sight (LoS) paths between the base station (BS) and multiple users via tunable single/multiple signal reflections, thereby significantly enhancing the BS's coverage performance. To achieve this goal, we present an optimization framework for multi-IRS deployment in this paper and study its efficient design. In particular, we assume that a set of candidate locations for deploying IRSs are given in an area of interest, and show that there exists a fundamental trade-off between maximizing the BS's coverage in the area and minimizing the total cost in multi-IRS deployment design. Specifically, the more IRSs deployed over those candidate locations, the smaller number of IRS reflections on average required for achieving a LoS link between the BS and any user location in the area, which helps reduce the cascaded path loss and thus enhance the communication performance. To optimally characterize this trade-off, we formulate the multi-IRS deployment problem based on graph theory and propose a new successive removal algorithm to efficiently solve this problem by iteratively removing IRSs from the candidate locations while satisfying a given communication performance constraint. Simulation results are provided to show the efficacy of the proposed design approach and algorithm for multi-IRS deployment.
Intelligent reflecting surface (IRS) has emerged as a promising technique to enhance wireless communication performance cost effectively. The existing literature has mainly considered IRS being deployed near user terminals to improve their performance. However, this approach may incur a high cost if IRSs need to be densely deployed in the network to cater to random user locations. To avoid such high deployment cost, in this paper we consider a new IRS aided wireless network architecture, where IRSs are deployed in the vicinity of each base station (BS) to assist in its communications with distributed users regardless of their locations. Besides significantly enhancing IRSs' signal coverage, this scheme helps reduce the IRS associated channel estimation overhead as compared to conventional user-side IRSs, by exploiting the nearly static BS-IRS channels over short distance. For this scheme, we propose a new two stage transmission protocol to achieve IRS channel estimation and reflection optimization for uplink data transmission efficiently. In addition, we propose effective methods for solving the user IRS association problem based on long term channel knowledge and the selected user IRS BS cascaded channel estimation problem. Finally, all IRSs' passive reflections are jointly optimized with the BS's multi-antenna receive combining to maximize the minimum achievable rate among all users for data transmission. Numerical results show that the proposed co site IRS empowered BS scheme can achieve significant performance gains over the conventional BS without co site IRS and existing schemes for IRS channel estimation and reflection optimization, thus enabling an appealing low cost and high performance BS design for future wireless networks.
In this paper, we consider the constrained estimation problem for the binomial AR(1) model using Bayesian approach. We show that by using Gibbs sampling algorithm, the constrains for the parameters and latent variables can be routinely implemented. While obtaining all the full conditional distributions under the unconstrained environment, we only need to generate samples from them and make restrictions to easily described cross-sections, respectively, which avoids complex numerical integrations under the overall constraint set. In the simulation study, the performance of our algorithm is checked. Finally, the method is applied to two real data examples.
This paper advances the proactive eavesdropping research by considering a practical half-duplex mode for the legitimate monitor and dealing with the challenging case that the suspicious link opportunistically communicates over parallel fading channels. To increase eavesdropping success probability, we propose cognitive jamming for the monitor to change the suspicious link's long-term belief on the parallel channels' distributions, and thereby induce it to transmit more likely over a smaller subset of unjammed channels with a lower transmission rate. As the half-duplex monitor cannot eavesdrop the channel that it is simultaneously jamming to, our jamming design should also control the probability of such "own goal" that occurs when the suspicious link chooses one of the jammed (uneavesdroppable) channels to transmit. We formulate the optimal jamming design problem as a mixed integer nonlinear programming and show that it is non-convex. Nevertheless, we prove that the monitor should optimally use the maximum jamming power if it decides to jam, for maximally reducing suspicious link's communication rate and driving the suspicious link out of the jammed channels. Then we manage to simplify the MINLP to integer programming and reveal a fundamental trade-off in deciding the number of jammed channels: jamming more channels helps reduce the suspicious link's communication rate for overhearing more clearly, but increases own goal probability and thus decreases eavesdropping success probability. Finally, we extend our study to the two-way suspicious communication scenario, and show there is another interesting trade-off in deciding the common jammed channels for balancing bidirectional eavesdropping performances. Numerical results show that our optimized jamming-assisted eavesdropping scheme greatly increase eavesdropping success probability as compared with the conventional passive eavesdropping.
GPS has been more and more important in people's life, which can provide accurate positioning for us.However, under realistic conditions GPS signal is very weak, it is easy to be outside intentional and unintentional interference, and thus can't achieve good positioning.This article describes the basic composition, structure and typical applications such as GPS satellite navigation system, followed by introduction of the principle of anti -jamming, anti -jamming analysis of satellite navigation needs, combined with the principle of anti -jamming system design platform to platform for the overall design, combined with the overall framework of the platform, designed the anti -jamming of RF circuits and digital hardware overall system.In this paper, mainly from the spatial and space-time domain algorithm anti -jamming anti -jamming algorithm.Because airspace anti -jamming algorithm is simple to implement, it can well suppress narrowband interference; at the same time, space-time domain algorithm on the basis of anti -jamming for wideband interference suppression also have a good effect.
The paper studies power control schemes for achieving the ergodic capacity of vector block-fading (BF) channels when the channel state information (CSI) is available to both transmitter and receiver sides. The optimal water-filling solution achieves the maximum ergodic capacity, but requires complicated calculations and frequent adjustment of the transmission powers. On the other hand, a single-target constant power (ST-CP) policy is easier to implement, but experiences large capacity loss compared to the optimal solution. A suboptimal policy is proposed which first groups the sub-channels within the frame of interest into multiple grouped channels, then allocates different constant powers to each grouped channel using a statistical water-filling (SWF) policy. The new scheme asymptotically achieves the maximum ergodic capacity. Simulations are given to evaluate the performance of the new scheme, and to compare it with the optimal power allocation scheme and the single-target constant power policy.
This paper studies a full-duplex filter-and-forward (FD-FF) relay system in frequency-selective channels. Conventionally, the loop-back signal at the FD relay is treated as harmful self-interference and needs to be significantly suppressed via both analog- and digital-domain cancellation. However, the performance of the conventional self-interference cancellation approach is fundamentally limited due to the quantization error induced by the analog-to-digital converter (ADC) with limited dynamic range. In this paper, we consider an analog filter-and-forward design to help avoid the quantization error, and surprisingly show that the maximum achievable rate of such an FD-FF relay system is in fact regardless of the loop-back channel at the FD relay. We characterize the maximum achievable rate of this channel by jointly optimizing the transmit power allocation over frequency at the source and the frequency response of the filter at the relay, subject to their individual power constraints. Although this problem is non-convex, we obtain its optimal solution by applying the Lagrange duality method. By simulations it is shown that the proposed joint source and relay optimization achieves rate gains over other heuristic designs, and is also advantageous over the conventional approach by cancelling the relay loop-back signal as self-interference, especially when the residual self-interference after cancellation is still significant.
This letter describes a novel Surface Acoustic Wave (SAW) sensor for carbon dioxide (CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) detection based on electric loading effect with a graphene (G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> )/nickel (Ni) - L-alanine- Al sandwich structure (MIM) as a sensing capacitance. This capacitance, which is fully coated on the IDTs and reflectors of SAW device and is sensitive to the pH value of the environment, is paralleled with the static capacitance (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> ) of IDTs constructing an equivalent static capacitance (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</sub> '). When the concentration of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> increased from 0 ppm to 40000 ppm, the equivalent static capacitance decreased from 5.402pF to 4.358pF. Then the center frequency of SAW sensor increases 20 kHz due to the electric loading effect. And the sensitivity of the fabricated SAW sensor for CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas was about 0.38 MHz/ (ppm*m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ).
A novel construction method of Quasi-Cyclic Low-Density Parity-Check (QC-LDPC) code is proposed in this paper, which is based on protograph and Balanced Block Design (BIBD) in combinational mathematics.The method is to fill the base matrix of protograph with the base set elements of BIBD in accordance with certain mathematical rules.And the base matrix of protograph proposed in the paper has special double diagonal structure, which overcomes the low weight code words in general structure and achieves rapid encoding at the same time.The QC-LDPC code in this paper possesses lower encoding complexity and less memory occupation; therefore it is easy for hardware implementation.In addition, it effectively avoids girth 4. Simulation results show that when the Bit Error Rate (BER) is 10 -7 , QC-LDPC codes based on Protograph and BIBD (PBIBD-LDPC) proposed in this paper has 0.5dB Net Coding Gain (NCG) compared with the protograph QC-LDPC codes that based on Vander monde matrix and PEG algorithm structure, and has 0.15dB NCG compared with the excellent code QC-LDPC that based on the lifting structure.
This paper shows a real improvement example of CNC machine control relay circuit. The improvement is based on the reliability analysis to fit the high reliability requirement. This paper gives the suggestion and method of the reliability analysis to instruct the similar design and improvement.
A solution based on utility function is proposed for the load balancing of CDMA and WIFI wireless access networks.The first step is to acquire the key indicators of the network.Based on the network indicators,a game model will then be established.An optimal network resource allocation strategy will be developed through game model calculations,in order to balance the network load and achieve maximum benefits for the operators.The solution includes a C+W network load balancing diagram.Simulation results show the effectiveness of the algorithm,which can improve network utilization and achieve balanced C+W network loads.
