Interference Avoidance Research Articles

Minimax Optimization Strategy for Process Parameters Planning: Toward Interference-Free Between Tool and Flexible Workpiece in Milling Process

In milling of flexible workpieces, like axial-flow compressor impellers with thin-wall blades and deep channels, interference occurrence between workpiece and tool shaft is a great adverse issue. Even though interference avoidance plays a mandatory role in tool path generation stage, the generated tool path remains just a nominally interference-free one. This challenge is attributed to the fact that workpiece flexibility and dynamic response cannot be considered in tool path generation stage. This paper presents a strategy in process parameters planning stage, aiming to avoid the interference between tool shaft and flexible workpiece with dynamic response in milling process. The interference problem is formulated as that to evaluate the approaching extent of two surfaces, i.e., the vibrating workpiece and the swept envelope surface generated by the tool undergoing spatial motions. A metric is defined to evaluate quantitatively the approaching extent. Then, a minimax optimization model is developed, in which the optimization objective is to maximize the metric, so as the interference-free can be guaranteed while constraints require the milling process to be stable and process parameters to fall into preferred intervals in which material removal rate is satisfactory. Finish milling of impeller using a conical cutter governed by a nominally interference-free tool path is numerically simulated to illustrate the dynamics responses of the spatially distributed nodal points on the thin-wall blade and approaching extent of the time-varying vibrating blades to the tool swept envelope surface. Furthermore, the present model results suggest to use an optimal process parameters set in finish milling, as a result improving machining efficiency in addition to ensuring the interference-free requirement. The model results are verified against milling experiments.

Improved Interference-Free Channel Allocation in Coordinated Multiuser Multiantenna Open-Access Small Cells

This paper investigates low-complexity joint interference avoidance and desired link improvement for single-channel allocation in multiuser multiantenna access points (APs) for open-access small cells. It is considered that an active user is equipped with an antenna array that can be used to suppress interference sources but not to provide spatial diversity. On the other hand, the operation of APs can be coordinated to meet design requirements, where each of which can unconditionally utilize assigned physical channels. Moreover, each AP is equipped with uncorrelated antennas that can be reused simultaneously to serve many active users. The analysis provides new approaches to exploit physical channels, transmit antennas, and APs to mitigate interference, while providing the best possible link gain to an active user through the most suitable interference-free channel. The event of concurrent service requests placed by active users on a specific interference-free channel is discussed for either interference avoidance through identifying unshared channels or desired link improvement via multiuser scheduling. The applicability of the approaches to balance downlink loads is explained, and practical scenarios due to imperfect identification of interference-free channels and/or the scheduled user are thoroughly investigated. The developed results are applicable for any statistical and geometric models of the allocated channel to an active user, as well as channel conditions of interference users. They can be used to study various performance measures. Numerical and simulation results are presented to explain some outcomes of this paper.

Coexistence of Smart Utility Networks and WLANs in Smart Grid Systems

This paper aims to analyze coexistence performance and study the impact of WLAN interferences on SUNs. To quantitatively reveal packet error rate (PER) performance of SUNs under multiple WLAN interferers, a segmentation scheme for desired data packet with multiple interferers is developed, based on which a packet collision model in a multi-interferer environment is proposed. The new packet collision model captures interference scenarios in every time segment of a desired packet using the proposed segmentation scheme. It paves a way to make a precise estimation of the PER of SUNs under multiple WLAN interferers. Furthermore, we design a channel agility scheme for coexistence of SUNs and WLANs via improving the existing ones, and analyze its performance in interference identification and avoidance. The proposed scheme performs interference detection for every data packet, and thus, an SUN is able to avoid WLANs interferences in a timely manner.

An Enhanced Cognitive Femtocell Approach for Co-Channel Downlink Interference Avoidance

The deployment of low-power nodes such as femtocells within the macrocell’s coverage area is one of the main features of future 5G networks. However, challenges arise in the femtocell planning and management, particularly due to interference occuring when femtocells are deployed in a co-channel with the macrocell. The cognitive radio inspired femtocell is one of the solutions to mitigate interference. In this study, the cognitive scheme is enhanced by enabling the femtocell to take advantage of LTE channel-dependent scheduling in order to predict the future resources of nearby victim macro- users and avoid using them. Simulation results show that the co-channel interference on the macrocell downlink signal is minimal, and therefore performance is improved under the condition that the cognitive femtocell operates adaptively and monitors spectrum allocations continuously.

Comprehensive Spectrum Management for Heterogeneous Networks in LTE-U

Recent interesting activities in spectrum analysis have introduced an additional band, the 5 GHz unlicensed spectrum, which has been primarily used for Wi-Fi. There are many challenges related to the coexistence of two different networks, a Wi-Fi network and an LTE network, sharing unlicensed bands but causing interference with each other. In this article, to solve the coexistence challenges, we propose a new protocol for carrier sensing and interference avoidance for heterogeneous networks: carrier sense LTE unlicensed access (CASLUA). The key idea of this protocol is that it listens to the channel by using a Wi-Fi air interface, but actually transmits data via an LTE air interface. This is achieved by using a proposed dual frame aggregation scheme where two frames (an L-frame and a U-frame) are allocated to licensed and unlicensed bands, respectively. Two implementations of CASLUA are carried out, one based on standalone operation (S-CASLUA)and the other operating with assistance from a software-defined network controller (SDN-CASLUA). SDN assistance lies in the monitoring of multiple network parameters, which are then used to make a decision on effective spectrum allocation with awareness of interference and capacity demands. Simulation results show that the CASLUA protocol helps to avoid interference and increases the average throughput by up to 40 percent for both Wi-Fi and LTE users in LTE-Unlicensed.

Memory Transformation Enhances Reinforcement Learning in Dynamic Environments.

As time passes, memories transform from a highly detailed state to a more gist-like state, in a process called "memory transformation." Theories of memory transformation speak to its advantages in terms of reducing memory interference, increasing memory robustness, and building models of the environment. However, the role of memory transformation from the perspective of an agent that continuously acts and receives reward in its environment is not well explored. In this work, we demonstrate a view of memory transformation that defines it as a way of optimizing behavior across multiple timescales.

Acoustic and visual courtship traits in two sympatric marine Gobiidae species – Pomatoschistus microps and Pomatoschistus minutus

Divergence in courtship traits across species can evolve as adaptations to different environments, and also through avoidance of reproductive interference and character displacement. Differences may also be explained by phylogenetic relationships. We compared different courtship traits, including male courtship sounds, in two sympatric Pomatoschistus species. Both species are characterised by having male and female courtship, and paternal care of eggs in nests under mussel shells and rocks. In addition to presenting novel observations, we reviewed the literature on courtship traits for both species and complemented it with new observations. We found that courting males of the common goby P. microps sing louder and produce sounds of shorter duration than males of the sand goby P. minutus. Furthermore, males of P. microps swim faster towards females during courtship than males of P. minutus. The eyes of P. minutus females turn black during courtship attempts, whereas this is not the case for females of P. microps. Species-specific differences in courtship sounds and behavior may lead to different susceptibility of the two species to environmental change such as noise pollution and turbidity.

Radio resource management scheme and outage analysis for network-assisted multi-hop D2D communications

In a cellular network it's very difficult to make spectrum resource more efficiently. Device-to-Device (D2D) technology enables new service opportunities, and provides high throughput and reliable communication while reducing the base station load. For better total performance, short-range D2D links and cellular links share the same radio resource and the management of interference becomes a crucial task. Here we argue that single-hop D2D technology can be used to further improve cellular networks performance if the key D2D radio resource management algorithms are suitably extended to support multi-hop D2D communications. Aiming to establish a new paradigm for the analysis and design of multi-hop D2D communications, We propose a radio resource allocation for multi-hop D2D routes based on interference avoidance approach in LTE-A networks. On top of that, we investigate the outage probability of D2D communication. We first introduce a new definition of outage probability by considering the maximum distance to be allowable for single-hop transmission. Then we study and analyze the outage performance of a multi-hop D2D route. We derive the general closed form expression of outage probability of the multi-hop D2D routes. The results demonstrate that the D2D radio, sharing the same resources as the cellular network, provide higher capacity compared to pure cellular communication where all the data is transmitted through the base station. They also demonstrate that the new method of calculation of D2D multi hop outage probability has better performance than classical method defined in the literature.

Two Birds With One Stone: Towards Secure and Interference-Free D2D Transmissions via Constellation Rotation

This paper studies the cooperative device-to-device (D2D) transmissions in cellular networks, where two D2D users communicate bidirectionally with each other and simultaneously serve as relays to assist the two-way transmissions between two cellular users. For this scenario, both cellular and D2D links share the same spectrum, thus creating mutual interference. In addition to that, a security problem also exists since the cellular users want to keep their messages secret from the D2D users and vice versa . To address these two issues, a security-embedded interference avoidance scheme is proposed in this paper. By exploiting the constellation rotation technique, the proposed scheme can create interference-free links for both D2D and cellular communications, thereby significantly improving the system error performance. Moreover, our scheme also provides an inherent secrecy protection at the physical layer, which makes the information exchange between cellular users and that between D2D users confidential from each other.

A comprehensive approach to determining minimum cutter lengths for five-axis milling

Interference detection and avoidance by the shortest cutter for the five-axis milling machining is a critical task. Short tool length increases the rigidity and chatter stability of the cutter. In this research, a new and efficient method of interference detection and avoidance by the shortest cutter is developed. For the specific five-axis machine configuration, first possible candidate parts for the collision are found, which are complete cutting system (spindle, tool holder, and cutter), the work in process model, and the fixture. Spindle, tool holder, and tool are represented by the solid geometry identity of the cylinder, truncated cone, and cylinder, respectively, with the length and diameter as parameters. The surfaces of the work in process model and the fixture model are represented as the point cloud data of the suitable density. The Kd-tree data structure is employed on point cloud data which gives an efficient searching of the potential candidate points for the interference detection with the complete cutting system. All existing methods are able to detect the collision, but they are not capable to remove it with the optimum cutter length. The proposed algorithm has not only the capability of collision detection; it can also remove the collision with the optimum tool length. Other scope of the proposed algorithm is the selection of the tool holder to minimize the overhang tool length.

Proactive Interference Avoidance for Mobile-to-Mobile Communication in LTE Networks

We present in this paper a novel proactive interference avoidance scheme for mobile-to-mobile (M2M) communication as an underlay in Long-Term Evolution (LTE) downlink networks. The proposed scheme introduces an intelligent user-selective resource allocation algorithm that aims to proactively avoid interference between M2M pairs and LTE regular users while achieving a satisfactory link budget for both M2M and LTE regular links. The proposed resource allocation algorithm is based on a novel low-complexity interference estimation approach that requires only channel quality indicator (CQI) information (CSI). Since the CQI reporting mechanism has been already implemented in current LTE systems, the proposed algorithm is indeed practical and standard compatible, compared with the existing works that require perfect knowledge of the channel state information (CSI). In this research, achievable data throughput with LTE-compliant adaptive modulation and coding has been adopted as the optimization measurement, rather than the information-theoretic capacity. Therefore, the performance of the proposed scheme is practically realizable in LTE communication systems. Since the performance of the proposed scheme highly relies on the accuracy of CQI feedback, we also carry out performance analysis to evaluate the impact of CQI estimation error and delay. The simulation results show that the total achievable data throughput for LTE networks is dramatically enhanced by M2M communication with this proposed interference avoidance resource allocation scheme.

Power Spectra Separation via Structured Matrix Factorization

Power spectra separation aims at extracting the individual power spectra of multiple emitters from the received mixtures. Traditional spectrum sensing for dynamic spectrum sharing is mostly concerned with detecting or estimating the aggregate spectrum. Spectra separation can be considered as a further step towards full awareness of the radio frequency (RF) environment, which may enable judicious routing, scheduling and beamforming with more effective interference avoidance. In other applications such as geoscience, astronomy, and chemometrics, separating the spectra of the objects/analytes from the sensed mixtures is also of great interest. Our prior work tackled this problem from a tensor decomposition point of view, but this requires delicate and careful receiver setups, and the algorithms are computationally heavy and difficult to decentralize. In this work, we propose to solve the power spectra separation problem using a structured matrix factorization model, where the columns of one of the two factor matrices live in the unit simplex. The salient features of this new framework are that 1) the receivers can be far simpler in terms of hardware, 2) an algebraically very simple algorithm can be employed for the centralized case, 3) and that effective decentralized algorithms can be devised under this framework. Numerical simulations and a laboratory experiment using real software-defined radios are presented to demonstrate the effectiveness of the proposed algorithms.

Cooperative Interference Mitigation for Heterogeneous Multi-Hop Wireless Networks Coexistence

This paper studies the coexistence of heterogeneous multi-hop networks, which use different physical-layer technologies. We propose a new paradigm, called cooperative interference mitigation (CIM), which exploits recent advancement in interference cancellation (IC), such as technology-independent multiple output. CIM makes it possible for disparate networks to cooperatively mitigate the interference to/from each other to enhance everyone’s performance. We first show the feasibility of CIM among heterogeneous multi-hop networks by exploiting only channel-ratio information. Then, we establish two tractable models to characterize the CIM behaviors of both networks by using full IC and receiver-side IC only. We propose two bi-criteria optimization problems aiming at maximizing both networks’ throughput, while cooperatively canceling the interference between them based on our two models. Several simulations are carried out to compare the Pareto-optimal throughput curves by using our CIM paradigms and traditional interference-avoidance (IAV) paradigm. By comparing the results from CIM and IAV, we show that CIM could remarkably improve the coexisting networks’ throughput in different network settings.

Phenotypic plasticity of mate recognition systems prevents sexual interference between two sympatric leaf beetle species.

Maladaptive sexual interactions among heterospecific individuals (sexual interference) can prevent the coexistence of animal species. Thus, the avoidance of sexual interference by divergence of mate recognition systems is crucial for a stable coexistence in sympatry. Mate recognition systems are thought to be under tight genetic control. However, we demonstrate that mate recognition systems of two closely related sympatric leaf beetle species show a high level of host-induced phenotypic plasticity. Mate choice in the mustard leaf beetles, Phaedon cochleariae and P. armoraciae, is mediated by cuticular hydrocarbons (CHCs). Divergent host plant use causes a divergence of CHC phenotypes, whereas similar host use leads to their convergence. Consequently, both species exhibit significant behavioral isolation when they feed on alternative host species, but mate randomly when using a common host. Thus, sexual interference between these syntopic leaf beetles is prevented by host-induced phenotypic plasticity rather than by genotypic divergence of mate recognition systems.

Neutralizing interferences in two‐hop amplify‐and‐forward MIMO relay systems

In this paper, we present the interference neutralization technique for two‐hop multiple‐input multiple‐output (MIMO) relay systems. It enables multiple MIMO transmitters (sources) to simultaneously transmit independent data streams to their MIMO receivers (destinations) without mutual interferences, thereby improving spectral efficiency of the systems. To neutralize the mutual interferences using multiple amplify‐and‐forward (AF) MIMO relays, we establish the sufficient condition for the antenna configuration in the MIMO relay networks, and provide a filter design technique for the AF MIMO relays. The proposed method increases sum rates of the systems linearly with the number of transmitters participating in simultaneous transmission. To improve the sum rates further, this method is combined with transmit power allocation using the water‐filling algorithm. In addition, it is shown that by employing the minimum number of relays required to meet the sufficient condition, the system cost for the proposed method can be reduced without compromising the sum rate performance severely. Finally, simulation results successfully demonstrate that by exploiting radio resources such as frequency and time efficiently, the proposed method achieves a higher sum rate than the existing techniques based on interference avoidance. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Quantum versus simulated annealing in wireless interference network optimization.

Quantum annealing (QA) serves as a specialized optimizer that is able to solve many NP-hard problems and that is believed to have a theoretical advantage over simulated annealing (SA) via quantum tunneling. With the introduction of the D-Wave programmable quantum annealer, a considerable amount of effort has been devoted to detect and quantify quantum speedup. While the debate over speedup remains inconclusive as of now, instead of attempting to show general quantum advantage, here, we focus on a novel real-world application of D-Wave in wireless networking—more specifically, the scheduling of the activation of the air-links for maximum throughput subject to interference avoidance near network nodes. In addition, D-Wave implementation is made error insensitive by a novel Hamiltonian extra penalty weight adjustment that enlarges the gap and substantially reduces the occurrence of interference violations resulting from inevitable spin bias and coupling errors. The major result of this paper is that quantum annealing benefits more than simulated annealing from this gap expansion process, both in terms of ST99 speedup and network queue occupancy. It is the hope that this could become a real-word application niche where potential benefits of quantum annealing could be objectively assessed.

A self-adaptive reconfiguration scheme for throughput maximization in municipal WMNs

Multi-hop wireless mesh network (WMN) is considered to be an economical technique for last-mile broadband Internet access (Tang et al., 2006). Fueled by the rapid development of the Internet of Things, it is increasing important to provide robust and high-quality urban wireless mesh networks (WMNs) for public service. However, WMNs encounter frequent link failures during their lifetime in practical use as a consequence of large-scale wireless interference, block buildings, etc., which deeply influences the performance of the network. These failures should be recovered in time or prevented with foresight. Tremendous labor and management cost should also be avoided. In this paper, we focus on an interesting phenomenon called “loop effect” in urban WMNs which may cause frequent link failures. A scheme named anti-loop network reconfiguration system (ALRS) for link recovery in municipal WMNs with QoS requirement is proposed and analyzed. ALRS takes the historical information into consideration to achieve maximum throughput, interference avoidance and self-reconfiguration with no requirement on mesh node antennas. Our evaluation results show that ALRS outperforms all the existing techniques in improving network throughput and reducing the occurrence probability of continuous link failure.

Packet-Based Energy Efficiency of MIMO Systems With Interference Avoidance Over Frequency-Selective Fading Channels

In this paper, we analyze packet-based energy efficiencies (EE) of battery-powered multiple-input multiple-output (MIMO) mobile radio communications over frequency-selective fading channels in the presence of cochannel interference (CCI). An efficient interference avoidance (IA) technique is proposed that relies on the conveyance of interference statistics derived at the receiver. Using the IA information, which incurs very small overhead, the transmitter selects the subchannels to be used for communications and on these subchannels, channel state information (CSI) derived from time-division duplexing (TDD) operation is applied in linear precoding strategies to minimize transmit energy consumption. The minimum energy solution is conditioned on various factors such as channel coding characteristics, linear precoding beams, interference avoidance schemes, and channel realizations. A method for identifying the transmit power leading to optimization is derived and simulation results show the effectiveness of the techniques over MIMO fading channels with different CCI conditions.

A Low-Complexity Cyclostationary Spectrum Sensing for Interference Avoidance in Femtocell LTE-A-Based Networks

This paper focuses on a new spectrum sensing algorithm based on the exploitation of the primary signal cyclostationarity property, which is used to avoid the intercell interference in a heterogeneous Long-Term Evolution Advanced (LTE-A) network. The performance of the proposed spectrum sensing method will be evaluated by means of a suitable analytical approach whose accuracy will be validated by comparing analytical predictions with simulation results under different communication channel propagation conditions. Furthermore, it will be shown that the proposed approach requires the lowest computational complexity among the cyclostationarity-based methods and allows better performance, even in the case of noise uncertainty, in terms of false alarm, detection probability, and deflection coefficient .

QoS Guaranteed Resource Allocation Scheme for Cognitive Femtocells in LTE Heterogeneous Networks with Universal Frequency Reuse

In this paper, we propose a novel resource allocation scheme for co-channel interference avoidance in LTE heterogeneous networks with universal spectrum reuse where both macro users (MUs) and cognitive femto base stations (FBSs) within the same macrocell coverage can dynamically reuse whole spectrum. Specifically, resource blocks (RBs) are shared between cognitive FBSs in underlay mode while the resource sharing among FBSs and MUs is in overlay mode. The macrocell is divided into inner and outer regions with the inner region further divided into three sectors. The proposed scheme addresses co-channel interference (CCI) by employing fractional frequency reuse (FFR) for RB allocation in the outer region of the macrocell and increase the distance of users that reuse the same RB within the macrocell. Part of RBs are allocated to the outer region of the macrocell with a FFR factor of 1/3, while the remaining RBs are dynamically allocated to each sector in the inner region of macrocell based on MUs demand to efficiently utilize the available spectrum. A basic macro base station (MBS) assistance is required by the FBS in selection of suitable RB to avoid interference with MU in each sector. With the proposed solution, both macro and femto users can dynamically access the whole spectrum while having minimum bandwidth guarantee even under fully congested scenarios. Moreover, the proposed scheme practically eliminates the cross-tier interference and the CCI problem in heterogeneous network reduces to inter-femtocell interference. The throughput and outage performances of the proposed scheme are validated through extensive simulations under LTE network parameters. Simulation results show that the proposed scheme achieves a performance gain of more than 1.5 dB in terms of SINRs of both macro user and femto user compared to traditional cognitive and non-cognitive schemes without bandwidth guarantee for femtocells.