Signal-to-interference-plus-noise Ratio Expression Research Articles

Cognitive Radar Waveform Design Method under the Joint Constraints of Transmit Energy and Spectrum Bandwidth

The water-filling (WF) algorithm is a widely used design strategy in the radar waveform design field to maximize the signal-to-interference-plus-noise ratio (SINR). To address the problem of the poor resolution performance of the waveform caused by the inability to effectively control the bandwidth, a novel waveform-related optimization model is established in this paper. Specifically, a corrected SINR expression is first derived to construct the objective function in our optimization model. Then, equivalent bandwidth and energy constraints are imposed on the waveform to formulate the waveform-related non-convex optimization model. Next, the optimal frequency spectrum is obtained using the Karush–Kuhn–Tucker condition of our non-convex model. Finally, the transmit waveform in the time domain is synthesized under the constant modulus constraint. Different experiments based on simulated and real-measured data are constructed to demonstrate the superior performance of the designed waveform on the SINR and equivalent bandwidth compared to the linear frequency modulated signal and waveform designed by the WF algorithm. In addition, to further evaluate the effectiveness of the proposed algorithm in the application of cognitive radar (CR), a closed-loop radar system design strategy is introduced based on our waveform design method. The experiments under real-measured data confirm the advantages of CR compared to the traditional open-loop radar structure.

IRS-Assisted Full Duplex Systems Over Rician and Nakagami Fading Channels

Intelligent reflecting surface (IRS) has been deemed as an energy and spectral-efficient technology, that can potentially enhance network coverage and transmission reliability, with minimum impact on transceivers' complexity. Motivated by this, we develop a comprehensive analysis on the performance of integrating IRS into full-duplex (FD) cellular or Internet of Things (IoT) networks in both realistic Rician and Nakagami fadings. Firstly, in the context of reciprocal channels in Rician fadings, we derive the closed-form approximations of the users' outage probability (OP) and ergodic capacity (EC), under the non-central Chi-square distribution assumption on the signal-to-interference-plus-noise ratio (SINR). Further following by the Gamma distribution assumption on the SINR, we derive the cumulative distribution function (CDF) expression of the user's SINR, which is then leveraged to obtain simple yet effective closed-form expressions in terms of OP and EC. Subsequently, in Nakagami fading scenarios with the reciprocal and non-reciprocal channels, the closed forms of both users' OP and EC are obtained. Finally, the correctness of all the theoretical expressions is verified through substantial Monte Carlo simulations. The results indicate that the OP and EC deduced from Gamma distribution exhibit the fairly precise results for the arbitrary number of IRS elements, especially in Nakagami fadings.

Performance analysis of spectrum sensing based on distributed satellite clusters under perturbation

In this paper, we investigate the spectrum sensing performance of a distributed satellite clusters (DSC) under perturbation, aiming to enhance the sensing ability of weak signals in the coexistence of strong and weak signals. Specifically, we propose a cooperative beamforming (BF) algorithm though random antenna array theory to fit the location characteristic of DSC and derive the average far-field beam pattern under perturbation. Then, a constrained optimization problem with maximizing the signal to interference plus noise ratio (SINR) is modeled to obtain the BF weight vectors, and an approximate expression of SINR is presented in the presence of the mismatch of signal steering vector. Finally, we derive the closed-form expression of the detection probability for the considered DSC over Shadowed-Rician fading channels. Simulation results are provided to validate our theoretical analysis and to characterize the impact of various parameters on the system performance.

Joint Precoding and Power Allocation for Multiuser MIMO System With Nonlinear Power Amplifiers

As the demand to alleviate the high cost and energy consumption problem in cellular communication systems grows, research on ways to compensate the hardware impairments for introducing low-cost devices into multi-input multi-output (MIMO) systems is becoming important. In particular, the nonlinearity of power amplifiers may severely degrade the performance of MIMO systems by distorting the precoded signals. In this work, we study the performance and precoding strategy of downlink multiuser MIMO systems with nonlinear power amplifiers. First, we analyze the signal-to-interference-plus-noise ratio (SINR) of nonlinear systems to establish the relationship between the transmit power and SINR. We find that the condition for maximizing the SINR depends on the average channel gain. Specifically, the maximum SINR is determined by the uncorrelated distortion when the average channel gain is large and by the distortion of precoding vector when the average channel gain is small. Motivated by the analysis, we propose an iterative algorithm, which alternately updates the precoding and power allocation by resolving the complicated coupling factors in the SINR expressions of nonlinear system. Furthermore, the proposed algorithm implicitly controls the total transmit power so that the desired signal, interference, and distortion are properly balanced. By the simulation results, we verify the analysis results and show that the proposed scheme outperforms the conventional schemes and achieves a near-optimal sum rate.

A Scalable and Energy-Efficient IoT System Supported by Cell-Free Massive MIMO

An Internet-of-Things (IoT) system supports a massive number of IoT devices wirelessly. We show how to use cell-free (CF) massive multiple input and multiple output (MIMO) to provide a scalable and energy-efficient IoT system. We employ optimal linear estimation with random pilots to acquire channel state information (CSI) for MIMO precoding and decoding. In the uplink (UL), we employ optimal linear decoder and utilize random matrix (RM) theory to obtain two accurate signal-to-interference plus noise ratio (SINR) approximations involving only large-scale fading coefficients. We derive several max–min type power control algorithms based on both exact SINR expression and RM approximations. Next we consider the power control problem for downlink (DL) transmission. To avoid solving a time-consuming quasiconcave problem that requires repeat tests for the feasibility of a second-order cone programming (SOCP) problem, we develop a neural network (NN) aided power control algorithm that results in 30 times reduction in computation time. This power control algorithm leads to scalable CF Massive MIMO networks in which the amount of computations conducted by each access point (AP) does not depend on the number of network APs. Both UL and DL power control algorithms allow visibly improve the system spectral efficiency (SE) and, more importantly, lead to multifold improvements in energy efficiency (EE), which is crucial for IoT networks.

Max-Min Power Control in Downlink Massive MIMO With Distributed Antenna Arrays

In this paper, we investigate optimal downlink power allocation in massive multiple-input multiple-output (MIMO) networks with distributed antenna arrays (DAAs) under correlated and uncorrelated channel fading. In DAA massive MIMO, the base station (BS) consists of multiple antenna sub-arrays. Notably, the antenna sub-arrays are deployed in arbitrary locations within a DAA massive MIMO cell. Consequently, the distance-dependent large-scale propagation coefficients are different from a user to these different antenna sub-arrays, which makes power control a challenging problem. We assume that the network operates in time-division duplex mode, where each BS obtains the channel estimates via uplink pilots. Based on the channel estimates, the BSs perform maximum-ratio transmission in the downlink. We then derive a closed-form signal-to-interference-plus-noise ratio (SINR) expression, where the channels are subject to correlated fading. Based on the SINR expression, we propose a networkwide max-min power control algorithm to ensure that each user in the network receives a uniform quality of service. Numerical results demonstrate the performance advantages offered by DAA massive MIMO. For some specific scenarios, DAA massive MIMO can improve the average per-user throughput up to 55%. Furthermore, we demonstrate that channel fading covariance is an important factor in determining the performance of DAA massive MIMO.

Max-Min QoS Power Control in Generalized Cell-Free Massive MIMO-NOMA With Optimal Backhaul Combining

This paper studies the uplink (UL) transmission of a generalized cell-free massive multiple-input multiple-output (massive MIMO) system in which multiple base stations (or access points), each equipped with a multiple-antenna array and connected to a central processing unit (CPU) over a backhaul network, simultaneously serve multiple users in a cell-free service area. The paper focuses on the non-orthogonal multiple access (NOMA) approach for sharing pilot sequences among users. Unlike the conventional cell-free massive MIMO-NOMA systems in which the UL signals from different access points are equally combined over the backhaul network, this paper first develops an optimal backhaul combining (OBC) method to maximize the UL signal-to-interference-plus-noise ratio (SINR). It is shown that, by using OBC, the correlated interference can be effectively mitigated if the number of users assigned to each pilot sequence is less than or equal to the number of base stations (BSs). As a result, the cell-free massive MIMO-NOMA system with OBC can enjoy unlimited performance when the number of antennas at each BS tends to infinity. A closed-form SINR expression is derived under Rayleigh fading and used to formulate a max-min quality-of-service (QoS) power control problem to further enhance the system performance. To deal with the NP-hardness of the concerned optimization problem, a successive inner approximation technique is applied to convert the original problem into a series of convex optimizations, which can be solved iteratively. In addition, a user grouping algorithm is also developed and shown to be better than random user grouping and a grouping method recently proposed in the literature. Numerical results are presented to corroborate the analysis and demonstrate the superiority of the proposed optimal backhaul combining over both equal-gain backhaul combining and zero-forcing backhaul combining.

PERFORMANCE ANALYSIS OF RESOURCE ALLOCATION TECHNIQUES FOR POWER CONTROL IN DEVICE-TO-DEVICE CELLULAR SYSTEMS

Recent development in pairs of devices communications in the cellular system has necessitated the emergence of various resource allocation strategies for power control with the hope of achieving higher data rate, enhanced system capacity and overall spectral efficiency. Strategies for efficient service delivery in device-to-device (D2D) cellular system have often posed daunting challenges requiring uncompromising techniques. In this work, various techniques for resource allocation strategies for power control in D2D cellular system are investigated. This work is dedicated at the best technique of achieving maximum transmission power of users of cellular and the device pair users with reference to the efficient service delivery coupled with established signal-to-interference-plus-noise ratio (SINR) at the base station and the D2D users across the channel of the uplink because of the ability of the individual transmitter of devices have been able to realign with the power of transmitter relative to the calculated SINR and interference parameters. An expression of SINR, D2D pairs and the distance between device pairs with respect to base station for the optimized network for the various techniques are analyzed. The performance of the resource-based power control technique (RPCT) and the adaptive power control technique (APCT), with respect to the SINR and the device pairs, has shown effectiveness in its ability to address over forty-three pairs of D2D in order to have an improved level of SINR as obtained in this work, it is convenient to say that an increase in the number of cellular users, enables a corresponding increase in the total capacity of D2D users. When an increase is experienced in the number of users of cellular, it automatically adds a value of increase to the reusable channels thereby enabling additional quantity of D2D users in the clusters, such that co-channel interference within the D2D users in the neighboring cluster reduces, thereby enabling an increased capacity of the user of D2D.

SINR and Rate Distributions for Downlink Cellular Networks

Signal-to-Interference-plus-Noise Ratio (SINR) measures the quality of the radio link between a base station and a User Equipment (UE). This quality indicator is important for the operator as it is used to measure and to optimize network coverage and the maximum user bitrate (which can be deduced from the SINR using the Shannon formula). In this paper, we study the SINR distribution for the downlink assuming that the received signals from serving and interfering cells undergo a path-loss and log-normal shadowing fading. We show that SINR can be approximated by a log-normal random variable and we give analytical expressions of characteristics parameters of its distribution. We then derive the average SINR expression. Also, we give a closed-expression of the rate probability density function and the outage probability and we obtain closed expressions of the average rate and lower and upper bounds of the average rate. For validation, we first compare theoretical results to Monte-Carlo network simulations and show that all the theoretical curves approximate well those obtained by simulations. Then using real measurements obtained by a measurement campaign, we validate the SINR distribution assumption. Based on a test of normality, we find that the recorded SINR samples are normally distributed in the logarithmic domain. We also show that the theoretical probability density function curves and the histogram of the measured samples of SINR are close.

Robust Transceiver Design for AF Asymmetric Two-Way MIMO Relaying

We consider a multiple-input multiple-output (MIMO) asymmetric two-way relay (A-TWR) system, wherein the base station (BS) serves a transmit-only user (TU) and receive-only user (RU). The TU transmits data to the BS and the RU receives data from the BS. Because of the asymmetric nature of A-TWR, the RU experiences interference and necessitates a joint transceiver design at the TU, RU, and relay. The existing literature has designed such transceivers by assuming perfect channel state information (CSI) at all the nodes. Obtaining perfect CSI at all the nodes is, however, not viable in practice due to the distributed nature of the system. This work constructs a transceiver design with perfect CSI at the relay and perturbed CSI at the TU, RU and BS. The perturbed signal-to-interference-plus-noise ratio (SINR) is analyzed by exploiting the properties of the singular value decomposition and the results from theory of matrix normal distributions. The resulting closed-form SINR expressions are then used to perform robust power allocation at all the nodes. Two different settings, namely maximization of the minimum SINR across all streams and minimization of the total network transmit power are considered. The performance gains from the proposed robust designs are validated numerically.

Adaptive Jamming Waveform Design for Distributed Multiple‐Radar Architectures Based on Low Probability of Intercept

AbstractThis paper investigates the problem of low probability of intercept (LPI)‐based adaptive jamming waveform design for distributed multiple‐radar architectures. Such a smart jammer system adopts a multibeam working mode, where multiple simultaneous jamming beams are synthesized to interfere with multiple radars independently. The primary objective of the smart jammer is to minimize the total jamming power by optimizing the transmitted jamming waveform while the achieved signal‐to‐interference‐plus‐noise ratio (SINR) and mutual information (MI) between the received echoes from the target at each radar receiver and the target impulse responses are enforced to be below specified thresholds. First, the expressions of SINR and MI are derived to characterize target detection and characterization performance, respectively. Then, two different LPI‐based jamming waveform design strategies are proposed to minimize the total noise jamming power by optimizing the jamming waveform while the achieved SINR/MI is enforced to be below a certain threshold. The resulting optimization problems are solved analytically by employing the technique of Lagrange multipliers. With the aid of some numerical examples, it is illustrated that the two schemes result in different jamming waveform design results, which is useful to guide jamming power allocation for various jamming tasks. It is also shown that the LPI performance of the smart jammer can be efficiently improved by exploiting the proposed jamming waveform design criteria.

NOMA With Guaranteed Weak User QoS: Design and Analysis

Non-orthogonal multiple access (NOMA) in the power domain serves multiple users at the same time and frequency slot. The significance of NOMA is its ability to increase the sum rate of the system and serve more users relative to orthogonal techniques. In this paper, we look at the high rate NOMA implementations where a single beamforming vector is shared by multiple users in the same cluster in a NOMA zero-forcing beamforming (NOMA-ZFBF) system. In order to maintain user fairness, it is important to guarantee the quality of service (QoS) of all clustered users. First, considering a target signal to interference plus noise ratio (SINR) for the weak user, i.e., guaranteeing the weak user's QoS (W-QoS), we propose a simple W-QoS-based NOMA (W-QoS NOMA) algorithm for NOMA cluster formation and power allocation that always exceeds the time division multiple access rates. Second, the correlation between the users plays a vital role during NOMA cluster formation in NOMA-ZFBF system. Therefore, we integrate the proposed W-QoS with partially correlated user clustering algorithms in order to analyze the effect of using the W-QoS technique. The numerical results confirm that the integration of W-QoS with partially correlated user clustering algorithms improves the sum capacity of the system. Third, considering an arbitrary correlation between users, we derive the signal to noise ratio (SNR)/SINR expressions of strong and weak users. These expressions show the importance of correlation factor which has a higher impact on the power penalty of the strong user, which in turn affects the clustering rate. Finally, we devise a mathematical technique using a perfectly correlated channel for the strong and weak users in each NOMA cluster to derive the exact SNR/SINR distributions of singletons, strong, and weak users. This gives a closed form expression for the expected sum rate, which gives an upper bound on performance. Furthermore, we investigate how close that realistic partially correlated user clustering can get to this bound.

Wideband Millimeter Wave Communication With Lens Antenna Array: Joint Beamforming and Antenna Selection With Group Sparse Optimization

For millimeter wave (mm-wave) communication systems, a lens antenna array with single-carrier transmission and path delay compensation is a promising technique for realizing cost-effective large multiple-input multiple-output communications with limited number of radio frequency chains. In this paper, we study the multi-user mm-wave downlink lens antenna array system for the general frequency-selective channels. By leveraging the angle-dependent energy focusing property of the lens antenna array and the angular sparsity of mm-wave channels, we investigate the low-complexity single-carrier transmission scheme with path delay pre-compensation applied at the base station (BS). The resulting signal-to-interference-plus-noise ratio (SINR) is derived by taking into account both the residual inter-symbol interference and inter-user interference. Based on the derived SINR expression, we propose an effective joint antenna selection and beamforming scheme by utilizing the group sparse optimization to accommodate for the limited number of RF chains at the BS. Thus, the proposed scheme can obtain the approximate performance with the fully digital case and has a better performance than the conventional orthogonal frequency-division multiplexing mode for the frequency-selectivity channels. Numerical results are provided to verify the effectiveness of the proposed schemes.

Wideband millimeter wave communication: Single carrier based hybrid precoding with sparse optimization

In millimeter wave (mmWave) communication systems, hybrid analog/digital precoding with single-carrier transmission and time delay compensation is a promising technique for realizing the cost-effective large-scale multiple-input multiple-output (MIMO) communications with limited radio frequency (RF) chains. This paper studies the mmWave downlink with fully connected MIMO architecture system for the general frequency-selective channels. By leveraging the fact that the mmWave channels are likely to be sparse in the directions and the signal propagation is usually dominated by the line of sight path, we investigate the low-complexity single-carrier transmission scheme with time delay precompensation applied at the base station (BS). The resulting signal-to-interference-plus-noise ratio (SINR) is derived in terms of the precoding vectors by taking into account both the residual intersymbol interference and interuser interference. Based on the derived SINR expression, we first propose a codebook based precoding scheme, then develop an effective joint codeword selection and precoding algorithm by utilizing the group sparse approaches to accommodate a limited number of RF chains at the BS. Numerical results are provided to validate the effectiveness of the proposed schemes, showing that the proposed scheme achieves a performance close to the fully digital system.

Performance of uplink WFRFT‐based hybrid carrier systems with non‐orthogonal multiple access

In this paper, the performance of hybrid carrier (HC) systems based on weighted fractional Fourier transform (WFRFT) is investigated in an uplink non-orthogonal multiple access (NOMA) scenario. NOMA is a promising technology to improve the system capacity, in which two users (far-user and near-user relative to a base station) are allocated to use the same time-frequency resources, and the successive interference cancellation (SIC) technique is implemented to decode signals at the receiver. Considering the actual error decoding in the SIC process (i.e. imperfect SIC), NOMA cannot avoid the inter-user interference (IUI) and residual interference (or error propagation). Therefore, firstly IUI and residual interference are analysed, and signal to interference plus noise ratio (SINR) of the far-user is expressed mathematically considering the residual interference. Then, based on the analysis of IUI, considering different WFRFT orders, a near-user BER expression over additive white Gaussian noise (AWGN) channels is derived. Furthermore, the optimal WFRFT order selection to minimise the interference influence in the uplink is formulated and solved efficiently. Simulation results have verified the mathematical expression of SINR, the near-user theoretical BER expression, and the proposed optimal WFRFT order selection to obtain the maximum sum spectral efficiency.

Robust Transmission Design for Multicell D2D Underlaid Cellular Networks

This paper investigates the robust transmission design (RTD) of a multi-cell device-to-device (D2D) underlaid cellular network with imperfect channel state information (CSI). The bounded model is adopted to characterize the CSI impairment and the aim is to maximize the worst-case sum rate of the system. To protect cellular communications, it is assumed that the interference from all D2D transmitters to each base station (BS) is power-limited. It is first shown that the worst-case signal-to-interference-plus-noise ratio (SINR) of each D2D link can be obtained directly, while that of cellular links cannot be similarly found since the channel estimation error vectors of cellular links are coupled in the SINR expressions. To solve the nonconvex problem, the objective function of the original problem is replaced with its lower bound, and the resulted problem is decomposed into multiple semidefinite programming (SDP) subproblems which are convex and have computationally efficient solutions. An iterative RTD algorithm is then proposed to obtain a suboptimal solution. Simulation results show that D2D communication can significantly increase the performance of the conventional cellular systems while causing tolerable interference to cellular users. In addition, the proposed RTD algorithm outperforms the conventional non-robust transmission design greatly in terms of network spectral efficiency.

Massive MIMO Uplink Scheme Design and System-Level Performance Analysis

The intercell interference in massive multiple-input-multiple-output uplink consists of both correlated and uncorrelated components, where the former is due to pilot contamination and the latter is usually neglected in most of the existing literature. In this paper, we show that the uncorrelated intercell interference is actually not negligible for reasonably many antennas at the base station. Hence, a novel and general uplink performance analysis framework is established to take the uncorrelated interference into account. Specifically, we investigate the tradeoff between pilot overhead and uplink signal-to-interference-plus-noise ratio (SINR) in four uplink transmission schemes. Without cell coordination, the conventional uplink scheme and the soft pilot reuse scheme are evaluated. Compared with the former one, the soft pilot reuse scheme has higher mitigation efficiency on correlated intercell interference. However, the uncorrelated intercell interference cannot be mitigated without cell coordination. With cell coordination, we first evaluate the scheme that the pilot information can be shared via backhaul. Hence, both the correlated and uncorrelated interference can be canceled effectively. We also propose and analyze a novel pilot extension scheme in the cell coordination scenario, which could address different preferences of both cell-edge and cell-center users. In all the above four schemes, the asymptotic expressions of uplink SINR for arbitrary user are first obtained. Based on them, we derive the distribution of uplink SINR by considering the randomness of interfering users’ locations. It is shown that the analytical results match the numerical simulation tightly. Besides, both analytical and numerical results demonstrate the performance gain of the proposed scheme.

Non-Linear Programming: Maximize SINR for Designing Spreading Sequence

Signal to interference plus noise ratio (SINR) is an important index for wireless communications. This paper shows a method to derive spreading sequences utilized in code division multiple access systems as the solutions of the non-linear programming: maximize SINR. To this end, we consider a frequency-selective wide-sense-stationary uncorrelated-scattering channel and obtain the worst case of SINR. In the course of the evaluation, we derive an expression of SINR, whose main terms consist of periodic correlation terms and odd periodic correlation terms. Also, we show a relation between SINR and mean square correlations. With our expression, we obtain the problem: maximize SINR. Since this problem is not convex, we obtain the relaxed problem with a semidefinite relaxation technique. From this relaxed problem, we obtain the approximated solutions and evaluate the bit error rate for the solutions.

Performance Analysis of Non-Regenerative Massive-MIMO-NOMA Relay Systems for 5G

The non-regenerative massive multi-input-multi-output (MIMO) non-orthogonal multiple access (NOMA) relay systems are introduced in this paper. The NOMA is invoked with a superposition coding technique at the transmitter and successive interference cancellation (SIC) technique at the receiver. In addition, a maximum mean square error-SIC receiver design is adopted. With the aid of deterministic equivalent and matrix analysis tools, a closed-form expression of the signal to interference plus noise ratio (SINR) is derived. To characterize the performance of the considered systems, closed-form expressions of the capacity and sum rate are further obtained based on the derived SINR expression. Insights from the derived analytical results demonstrate that the ratio between the transmitter antenna number and the relay number is a dominate factor of the system performance. Afterward, the correctness of the derived expressions are verified by the Monte Carlo simulations with numerical results. Simulation results also illustrate that: 1) the transmitter antenna, averaged power value, and user number display the positive correlations on the capacity and sum rate performances, whereas the relay number displays a negative correlation on the performance and 2) the combined massive-MIMO-NOMA scheme is capable of achieving higher capacity performance compared with the conventional MIMO-NOMA, relay-assisted NOMA, and massive-MIMO orthogonal multiple access (OMA) scheme.

A method using optimized combinations based on energy spectrum extension factor to reduce MAI in asynchronous DS-CDMA systems

The principle to suppress multiple access interference (MAI) using double chip waveforms (DCW) in asynchronous DS-CDMA systems is analyzed in the paper. Based on the principle, a new method adopting optimized combinations of chip waveforms (CCW) to reduce MAI is proposed. The energy spectrum extension factor (ESEF) of equivalent chip waveform is introduced to optimally select CCW to reduce MAI, improve the signal to interference plus noise ratio (SINR) and bite error rate (BER) performance of asynchronous DS-CDMA users. The general closed form expression of SINR for asynchronous DS-CDMA users with CCW is obtained. The BER is also derived by improved Gaussian approximation (IGA). The theoretical analysis and numerical simulation results show that the optimized CCW using ESEF can effectively suppress MAI better, achieve higher SINR and BER performance compared with DCW. Moreover, the overlap between the simulation and IGA BER curves verifies the theoretical derivation.