SINR Performance Research Articles

RIS-Aided LDM System: A New Prototype in Broadcasting System

Layer-division multiplexing (LDM) system has developed with significant improvement in spectrum efficiency and service diversity. LDM technology, that superposes multiple signals with different transmit powers, has been adopted by ATSC 3.0 to deliver robust high-definition services. However, due to the high mobility of devices, the wide signal coverage, and the uneven geographical channel condition, there exists under-utilized energy and significant potential of enhancing communication capacity in the LDM system. In this paper, we employ reconfigurable intelligent surface (RIS) to improve the reception quality in the LDM system, especially the SINR performance of the terminals in the edge area. We formulate a problem of maximizing the minimum SINR among all the terminals by jointly optimizing the power control and pairing mechanism, which is a Mixed-integer Nonlinear Programming (MINLP) problem. To solve it, we use the convex-concave procedure (CCCP). We further explore the high-mobility scenario with the limited channel state information (CSI) and the missing knowledge of detailed prediction of terminals’ mobility. We use Brownian Motion to model the possible variation of the terminals’ positions in the high mobility scenario to guarantee the successful reception probability. The analysis shows the RIS can bring obvious SINR gain to the LDM system, and the mobility modification could greatly help improve the successful reception probability.

Performance Analysis of Linearly Arranged Concentric Circular Antenna Array with Low Sidelobe Level and Beamwidth Using Robust Tapering Technique.

In this research, a novel antenna array named Linearly arranged Concentric Circular Antenna Array (LCCAA) is proposed, concerning lower beamwidth, lower sidelobe level, sharp ability to detect false signals, and impressive SINR performance. The performance of the proposed LCCAA beamformer is compared with geometrically identical existing beamformers using the conventional technique where the LCCAA beamformer shows the lowest beamwidth and sidelobe level (SLL) of 12.50° and -15.17 dB with equal elements accordingly. However, the performance is degraded due to look direction error, for which robust techniques, fixed diagonal loading (FDL), optimal diagonal loading (ODL), and variable diagonal loading (VDL), are applied to all the potential arrays to minimize this problem. Furthermore, the LCCAA beamformer is further simulated to reduce the sidelobe applying tapering techniques where the Hamming window shows the best performance having 17.097 dB less sidelobe level compared to the uniform window. The proposed structure is also analyzed under a robust tapered (VDL-Hamming) method which reduces around 69.92 dB and 48.39 dB more sidelobe level compared to conventional and robust techniques. Analyzing all the performances, it is clear that the proposed LCCAA beamformer is superior and provides the best performance with the proposed robust tapered (VDL-Hamming) technique.

On Blind Channel Estimation in Full-Duplex Wireless Relay Systems

We investigate the feasibility of second-order statistics-based blind channel estimation in the context of two-hop full-duplex relay systems. To that end, the performance of blind and traditional pilot-based (training sequence based) channel estimation approaches are compared. This is accomplished by deriving the Cramer-Rao Lower Bound (CRLB) expressions for both blind and pilot-based schemes, and comparing them to each other and to the mean-squared error (MSE) values measured via simulation. Post-equalization SINR expressions are also derived for both blind and pilot-based methods. Furthermore, a modified post-equalization SINR expression, where the channel estimation error is replaced by the inverse of the Fisher information matrix (FIM) is proposed, providing an upper bound for the post-equalization SINR. These analytically-predicted SINR values for the blind approach are compared to the SINR measured via link simulation. The performance of the two channel estimation methods is analyzed by comparing the CRLB, post-equalization SINR, and BER performance for two significantly different transmission packet sizes. All of the above metrics indicate that blind estimation provides clear performance advantages relative to the pilot-based counterpart. Additionally, the blind approach eliminates the overhead associated with the pilot-based method, where a portion of the system resources is allocated to the pilot sequence. To quantify this, the spectral efficiency of the FD relay system employing blind and pilot-based channel estimation methods are compared, indicating that at high SNR, the blind approach provides around 2-bps/Hz spectral efficiency gain relative to a typical pilot-based method. Finally, the computational complexity of the two channel estimation techniques are evaluated and compared. The blind approach has a clear computational advantage for larger packet sizes.

Smart Anti-jamming Mobile Communication for Cloud and Edge-Aided UAV Network

The Unmanned Aerial Vehicles (UAV) networks consisting of low-cost UAVs are very vulnerable to smart jammers that can choose their jamming policies based on the ongoing communication policies accordingly. In this article, we propose a novel cloud and edge-aided mobile communication scheme for low-cost UAV network against smart jamming. The challenge of this problem is to design a communication scheme that not only meets the requirements of defending against smart jamming attack, but also can be deployed on low-cost UAV platforms. In addition, related studies neglect the problem of decision-making algorithm failure caused by intermittent ground-to-air communication. In this scheme, we use the policy network deployed on the cloud and edge servers to generate an emergency policy tables, and regularly update the generated policy table to the UAVs to solve the decision-making problem when communications are interrupted. In the operation of this communication scheme, UAVs need to offload massive computing tasks to the cloud or the edge servers. In order to prevent these computing tasks from being offloaded to a single computing resource, we deployed a lightweight game algorithm to ensure that the three types of computing resources, namely local, edge and cloud, can maximize their effectiveness. The simulation results show that our communication scheme has only a small decrease in the SINR of UAVs network in the case of momentary communication interruption, and the SINR performance of our algorithm is higher than that of the original Q-learning algorithm.

On Receive Window Design for UF-OFDM Signals Over Multipath Channels

We study the impact of receive windowing on the quality of signal reception for the multicarrier waveform “universal filtered orthogonal frequency division multiplexing” (UF-OFDM), which shows a great potential in asynchronous transmissions. Due to the absence of a cyclic prefix (CP), UF-OFDM signals are more vulnerable to multipath channels. We show that the receive window can be designed to suppress the intersymbol interference (ISI) and intercarrier interference (ICI) induced by multipath propagation. The SINR performance of UF-OFDM signals is evaluated, both analytically and by simulations, for various multipath channel models. About 3 dB SINR gain can be achieved by simply extending the length of the receive window for channels with relatively large root mean square delay spreads.

Uplink Null-Space Expansion for Multiuser Massive MIMO in Time-Varying Channels Under Unknown Interference

This article proposes a novel postcoding design scheme for suppressing inter-user interference (IUI) and inter-cell interference (ICI) in uplink multiuser massive multiple-input multiple-output (MIMO) system in time-varying channel environments. In the uplink system, the base station (BS) designs postcoding weight based on estimated channel state information (CSI) to suppress IUI. When user terminals move, the estimated CSI is outdated because actual channels vary with time. This causes IUI and leads to degrading the system capacity. Besides, ICI extensively arises in multiuser massive MIMO systems since many users are simultaneously supported in each cell. The accuracy of CSI estimates is degraded since ICI contaminates the uplink pilot sequences from desired users. Adopting a weight design based on minimum mean square error (MMSE) criteria, we can suppress ICI adequately, and exploiting plentiful degrees of freedom (DoFs) of massive array, we can also suppress IUI even in time-varying channels by steering many nulls for one user based on null-space expansion (NSE) scheme. The computer simulations clarify that the proposed scheme has superior SINR performance in Rayleigh fading channel at low speed, low SIR, and high SNR regions while it is effective at almost all conditions in Rician fading channel.

Recursive Updating Algorithm for Robust Adaptive Beamforming in a Uniform Circular Array

When the phase-mode transformation technique is used in a uniform circular array, its output performance is known to degrade owing to the approximations applied to the formulation. In this paper, we develop a robust recursive updating algorithm based on the worst-case performance optimization and phase-mode transformation in the uniform circular array, which provides efficient robustness not only against the signal steering vector mismatches, but also against the transformation errors. The proposed algorithm belongs to the class of the diagonal loading technique and the transformation matrix belongs to a certain ellipsoid set. The weight vector is updated by the Lagrange multiplier method, in which the parameters are derived simply. The proposed algorithm has a closed-form solution, in which we analyse the reasonable ranges of two key parameters. The convergence performance and the output SINR performance are also analysed. In additional, the implementation complexity costs of the proposed algorithm and MVDR algorithm are presented in this paper. Our robust algorithm has a low implementation complexity cost and achieves the mean output array SINR consistently close to the optimal one. Simulation results are presented to compare the performances of our algorithm with the conventional algorithms.

Reduced-Dimension Wiener Filter Based on Perpendicular Partition

This paper addresses the reduced-dimension Wiener filter based on perpendicular partition. Two algorithms, i.e., cyclic per-weight (CPW) and batch CPW (BCPW) are presented, which can efficiently perform reduced-dimension adaptive beamforming. In particular, the CPW is suitable for the slow changing environments that have large snapshots to train the weight vector. The BCPW is designed for fast changing scenarios that have low training sequences and sometimes the number of snapshots is less than the number of sensors. In these two algorithms, the solutions of the weight vectors are circularly solved one by one, which only refer to scalar optimization problem then the matrix inversion is avoided. There is no intermediate transformation or orthogonal/non-orthogonal decomposition requirement in our algorithms, so their implementations are relatively simple. Convergence analysis and the computational complexities comparison are provided. Simulation results show the superiorities of the proposed algorithms. Specifically, the CPW has better convergence properties than previous schemes, and the BCPW has low computational complexity and good output SINR performance in low snapshots scenarios.

Open Loop and Closed Loop Power Control Analysis on LTE

LTE downlink is using Orthogonal Frequency Division Multiple Access (OFDMA) multiple access system which have high invulnerability from multipath problem. One of the weakness of OFDM system is the high level from Peak to Average Power Ratio (PAPR) that was required higher level transmit power for maintaining the Bit Error Rate (BER) requirement. Using uplink scheme with Single Carrier FDMA (SC-FDMA) which is OFDMA modification, will be offered better level of PAPR than its conventional OFDM. The main problem of using OFDMA is the high level of PAPR, while using SC-FDMA the problem is intra-cell interference. Intra-cell or inter-cell interference is the common problem that can reduce the LTE performance. Minimizing received power for each users (UE) which is still at acceptable tolerance parameter, can be used for reducing the interference problem to another UE. Power control is the appropriate solution for minimizing the interference level. In this paper will be analyzed the power control using open loop and closed loop scheme at LTE network. The simulation result show that without power control schemes, the transmit power of UE is 23 dBm. While, after applying power control scheme, the transmit power is 18.8 dBm at ?=0.4 of open loop condition and 9.05 dBm at closed loop condition. Using this transmit power value as the UE power can improve the SINR performance. The SINR average value without power control scheme is only 20.38 dB which is lower than using open loop scheme is achieved 22.44 dB and 24.02 dB at closed loop scheme.

Relay Placement for Coverage Extension in Cellular Wireless Networks Under Composite Fading Model

In relay-assisted cellular networks, mobile stations are connected to base station through two or more single-hop communication links, where the intermediate nodes act as relay stations (RSs). The focus of this paper is on two-hop relay assisted cellular networks, where optimal relay placement is a crucial issue for achieving maximum extension of the cell coverage. However, the location of RS has significant impact on signal-to-interference plus noise ratio (i.e., SINR) and outage probability experienced on the access and backhaul links. Moreover, the frequency re-use factor also has significant influence on the SINR. In this paper, we develop analytical models for computing the SINR and outage probability performance of a two-hop relay assisted cellular network for both downlink (DL) as well as uplink (UL) transmission scenarios, considering the impact of path loss, shadowing, Nakagami fading and co-channel interference. We then investigate optimal placement of RS while satisfying the required criterion on probability of correct decoding, initially by considering the DL scenario alone and then by considering both DL and UL scenarios jointly. Through extensive evaluations, we report the impact of realistic propagation models on outage probability, optimal relay position and the cell coverage radius. Further, the model can be used to find the impact of co-channel re-use factor on optimal relay positioning in two-hop cellular networks.

Robust Minimum Variance Beamforming Based on Signal Power Maximization

Conventional beamformers are very sensitive to steering vector mismatches and their performance degrades in the presence of array mismatches. This paper proposes a robust minimum variance beamforming algorithm based on signal power maximization. In the proposed algorithm, the beamforming vector is determined by maximizing the signal power while minimizing the output power of the beamformer, with the signal distortionless response constrained to be unity. Numerical results show that the proposed beamformer is robust to the steering vector mismatch, and achieves better SINR performance than other robust beamforming algorithms when the mismatch in the signal look direction is large.

Channel allocation and power control schemes for cross-tier 3GPP LTE networks to support multimedia applications

In this paper, we present the framework of a channel allocation (CA) and power control (PC) schemes for the minimization of interference in cross-tier 3GPP LTE networks that aim to support internet of multimedia things. Channel allocation scheme based on an interference graph preserving the minimum number of interfered MUEs by femtocells (IG-MIM) is proposed to mitigate interference amongst femtocells, and a game theory based power control algorithm is also proposed to reduce interference to surrounding macrocell users (MUEs). The proposed IG-MIM scheme constructs the interference graph based on a predefined threshold and allocates the subchannels to the femtocells that maintain the smallest number of interfered MUEs. For the power control, we design a payoff function based on the rewards from the achieved data rates and the penalties from the interference in regards to its adjacent femtocells. The simulation results show that the IG-MIM channel allocation significantly improves the SINR performance for the femtocell users (FUEs) being served; the game theory based power control decreases the power requirements of a femtocell and alleviates the interference to the MUEs.

Performance Analysis of Scheduling Schemes for Femto to Macro Interference Coordination in LTE-Femtocell Deployment Scenario

Deploying femtocells that have low power level in LTE with small coverage area is an alternative solution for mobile operators to improve indoors network coverage area as well as system capacity. However deploying femtocells (HeNB) that were used co-channel frequency, can be brought about interference problem to the Macro BTS (eNB). Close Subscriber Group (CSG) of HeNB allows only User equipment (UE) to access HeNB. HeNB is the source of interference for UE who cannot access it. Therefore it is necessary for interference coordination methods among the HeNB and eNB. The methods are ICIC (Intercell Interference Coordination) and eICIC (enhanced Intercell Interference Coordination). This paper proposed performance analysis of scheduling schemes for Femto to macro interference coordination that allocated resource in the frequency and time domain using LTE-Femtocell suburban and urban deployment scenario. Simulation result using ICIC methods can improve SINR performance 15.77 % in urban and 28.66 % in suburban, throughput performance 10.11 % in urban and 21.05 % in suburban. eICIC methods can improve SINR performance 17.44 % in urban and 31.14 % in suburban, throughput performance 19.83% in urban and 44.39 % in suburban.The result prove using eICIC method in time domain resource have better performance than using ICIC method in frequency resource. However using eICIC method in suburban deployment scenariocan increase the performance of SINR and throughput more effective than using eICIC method in urban deployment scenario.

Probabilistic Analysis on QoS Provisioning for Internet of Things in LTE-A Heterogeneous Networks With Partial Spectrum Usage

This paper investigates quality of service (QoS) provisioning for Internet of Things (IoT) in long-term evolution advanced (LTE-A) heterogeneous networks (HetNets) with partial spectrum usage (PSU). In HetNets, the IoT users with ubiquitous mobility support or low-rate services requirement can connect with macrocells (MCells), while femtocells (FCells) with PSU mechanism can be deployed to serve the IoT users requiring high-data-rate transmissions within small coverage. Despite the great potentials of HetNets in supporting various IoT applications, the following challenges exist: 1) how to depict the unplanned random behaviors of the IoT-oriented FCells and cope with the randomness in user QoS provisioning and 2) how to model the interplay of resource allocation (RA) between MCells and FCells under PSU mechanism. In this work, the stochastic geometry (SG) theory is first exploited to statistically analyze how the unplanned random behaviors of the IoT-oriented FCells impact the user performance, considering the user QoS requirements and FCell PSU policy. Particularly, to satisfy the QoS requirements of different IoT user types, the concept of effective bandwidth (EB) is leveraged to provide the users with probabilistic QoS guarantee, and a heuristic algorithm named QA-EB algorithm is proposed to make the EB determination tractable. Then, the interplay of RA between the MCells and FCells is formulated into a two-level Stackelberg game, where the two parties try to maximize their own utilities through optimizing the macro-controlled interference price and the femto-controlled PSU policy. A backward induction method is proposed to achieve the Stackelberg equilibrium. Finally, extensive simulations are conducted to corroborate the derived SINR and ergodic throughput performance of different user types and demonstrate the Stackelberg equilibrium under varying user QoS requirements and spectrum aggregation capabilities.

An Approach for Selecting Optimum Number of Base Stations and Optimizing Site Locations using Flower Pollination Algorithm

Wireless communication has observed inordinate advancement since the beginning of this century. There is an expansion in wireless communication due to upsurgement in demands of customers for better services. To give fine quality to customers there is need to plan the network .This work considers how to optimally locate the BTS so that maximum coverage obtained at lesser infrastructure cost. This dissertation work is intended to present the investigations on swarm based optimization technique to locate the BTS in a network. In this work to locate the BTS, firstly calculate the SINR, capacity and network performance are calculated to find optimal no. of cell sites. Thereafter FPA is used to find the location of these sites. Furthermore FPA is compared with ABC to optimally locate the BTS.

Guard Band-Based Resource Sharing for Device-to-Device Communications Underlying Cellular Network

The performance of device-to-device (D2D) communication in a cellular network depends on the resource sharing between D2D links and cellular users. Existing researches on resource sharing mainly focus on power control between the D2D users and cellular users that operate in the same frequency band. However, the D2D outage probability performance is hampered by the cellular interference to D2D links. Therefore, the D2D users may not achieve satisfactory SINR performance when D2D users and cellular users are geographically located in a small area; as a result, the outage probability performance would be significantly degraded. In this paper, we provide a novel resource sharing strategy to mitigate the interference from cellular users to D2D receivers by utilizing the low energy characteristics of signals in the guard band and analyze the D2D outage probability performance mathematically. Both the mathematical analysis and numerical results show that the proposed resource sharing strategy provides 1.2 dB SNR gain in D2D outage probability performance while guaranteeing the cellular throughputs.

Spatially Robust Far-field Beamforming Using the von Mises(-Fisher) Distribution

This paper presents spatially robust far-field microphone beamformers and nullformers derived using the von Mises and von Mises-Fisher distributions to model the expected direction of arrival. Simple analytic expressions are presented for 2D and 3D far-field correlation functions and used to design spatially robust beamformers and nullformers. It is demonstrated that the spatially robust beamformers show a modest improvement in tolerating uncertainty in the target direction of arrival without incurring a significant penalty in terms of SINR performance compared with the MVDR beamformer. In addition, the spatially robust formulation shows significantly improved numerical robustness, indicating improved ability in tolerating intrinsic array errors.

A Signal Detection Technique for OFDMA-based Wireless Mesh Networks with TDoAs

In this paper, the effect of time difference of arrival (TDoA) is investigated for distributed nodes in OFDMA-based wireless mesh networks (WMNs). In order to minimize the interferences caused by TDoA in WMNs, the optimal starting point of FFT window at the receiver side of a node is derived by maximizing the effective SINR for each subcarrier. Also, a signal detection technique, called two dimensional ordered successive interference cancellation (TD-OSIC), is proposed for WMNs with TDoAs. It was shown via simulation that the proposed technique can achieve effective SINR and BER performances similar to the ideal case (no TDoA), even in WMNs with large TDoAs.

Orthogonal Space Projection (OSP) Processing for Adaptive Interference Cancellation

An Orthogonal Space Projection (OSP) processing methodology is introduced that achieves interference cancellation within a single time compression interval, e.g. pulse interval for fast time or dwell interval for slow time. The OSP technique can operate in pre-compression or post-compression spaces where covariance matrix development and compression are performed simultaneously. OSP projects the signal and interference into a space that is matched to the signals of interest and into a space that is mismatched to the signals of interest similar to a blocking matrix in conventional adaptive processing methods. The output of the OSP process is a two-dimensional image space that combines signal compression and interference cancellation. A pre-compression OSP technique is applied to array processing for jammer suppression and a two-dimensional array example is used to assess SINR performance.

3GPP LTE-A에서의 진화된 간섭 제거 수신기

본 논문은 3GPP Rel-12 표준에서 진행되고 있는 간섭 제거 수신기에 대한 동향과 연구이다. 최근 급증하는 무선 데이터 트래픽 요구에 대응하기 위해 단말 수신기 측면에서는 가장 문제가 되는 셀 간 간섭을 제어할 수 있는 수신기가 필요하다. 이를 위해 근본적인 간섭의 원인인 인접 셀의 데이터 및 제어 신호를 직접 제거하여 수신기의 SINR을 향상시켜 수신 성능을 올리는 네트워크 보조 간섭 제거 (NAICS) 수신기가 표준에서 논의 되고 있다. 본 논문에서는 현재 3GPP 표준에서 논의하는 네트워크 보조 간섭 제거 수신기에 대한 개념 및 동작, 그리고 고려되고 있는 수신기의 기본 성능을 파악하고, 이를 바탕으로 향후 표준에서 진행될 수 수신기의 진화 방향에 대해 살펴본다. This paper focuses on advanced receiver for interference suppression or cancellation from neighbor cells in the 3GPP Rel-12 standard. From UE (User Equipment) perspective, the advanced receiver which can manage inter-cell interference of adjacent cell is required to support and manage fast-growing wireless data traffic. In 3GPP standard, NAICS which is one of approaches to improve SINR and receiver performance by directly suppression or cancellation of data (PDSCH) and control (PDCCH) signal from interference cells is discussed. In this paper, we briefly introduce the concept and candidate receivers for NAICS (Network Assisted Interference Cancellation and Suppression) based on 3GPP Rel-12 standard, and simulation results for basic NAICS receiver performance are provided.