Interference Avoidance Techniques Research Articles

Interference Situational Aware Beam Pointing Optimization for Dense LEO Satellite Communication System

Recently, the low earth orbit (LEO) mega-constellation faces serious time-varying interferences due to spectrum sharing, dense deployment, and high mobility. Therefore, it is important to study the interference avoidance techniques for the dense LEO satellite system. In this paper, the interference situational aware beam pointing optimization technique is proposed. Firstly, the angle of departure (AoD) and angle of arrival (AoA) of the interfering links are obtained to represent the time-varying interference. Then, the interference avoidance problem for dense LEO satellite systems is modeled as a non-convex optimization problem, and a particle swarm optimization (PSO) based method is proposed to obtain the optimal beam pointing of the user terminal (UT). Simulations show that the relative error of the mean signal-to-interference plus noise ratio (SINR) obtained by the proposed method is 0.51%, so the co-channel interference can be effectively mitigated for the dense LEO satellite communication system.

Co-Channel Interference Mitigation in 5g Network using Particle Swarm Optimization

The co-channel interference problem in 5G wireless networks is the subject of this research project. Even with the improvements brought forth by 5G, co-channel interference still degrades network speed and signal quality. Particle Swarm Optimization (PSO) is the method used in this study to minimize this interference and improve network performance by fine-tuning resource allocation settings. PSO-based interference mitigation, network modeling, simulation, an overview of the literature, and comparative analysis are all included in the study. The study is valuable for communication engineers since it explores PSO as a means of improving network quality and expanding our knowledge of wireless technology, even though it is restricted to co-channel interference and PSO. In the sphere of 5G wireless communication, this discovery represents a substantial advancement. The application of particle swarm optimization has shown to be innovative in addressing the complex problem of co-channel interference. Insights into the possibilities of clever optimization strategies for interference reduction can be gained from the applied models and results. With 5G networks set to revolutionize the digital environment, these findings provide a strong basis for future research efforts focused at refining interference avoidance techniques and ultimately boosting the performance and dependability of these networks.

On the Stability Region of Intermittent Interference Networks

Recent information-theoretic studies have resulted in several interference management (IM) techniques that promise significant capacity improvements over interference avoidance techniques. However, in practice, the stable throughput region is a more relevant metric compared to the capacity region. In this work, we focus on the stable throughput region of a two-pair intermittent interference network with distributed transmitters and propose a queue-based transmission protocol in different regimes to handle the data between queues. In this context, we translate physical-layer IM protocols to accommodate stochastic message arrivals. To evaluate our proposed techniques, we compare the stable throughput region to the capacity region and show, through simulations, that the stable throughput region matches the capacity region when the latter is known. We show that in order to achieve the optimal stable throughput region, new ingredients are needed when compared to prior results. We quantify the trade-off between encoding/decoding complexity of the proposed scheme (in terms of number of required algebraic operations), and the achievable rates. Finally, we study the lifetime of messages (i.e. the duration from arrival to successful delivery) versus the total communication time, and we observe that the average lifetime scales as the square root of the total communication time.

Analysing the Impact of Mutual Interference in Body Area Networks

The development of electronics and short-range communications gave rise to smart healthcare systems known as body area networks (BAN), to record the vital signs of patients for diagnosis. However, these systems may be located in dense areas, where several networks operate next to each other. Hence, interference occurs, which can adversely affect their proper functioning. Before proceeding with interference reduction or avoidance techniques, it is very important to first analyze this problem under different contexts and scenarios, to better understand it. The aim of this paper is to study the impact of inter-ban interference in body area networks on overall energy consumption, under two different contexts: when the inter-ban distance is varying, and when the amount of nodes in surrounding BANs increases. For this purpose, the two following scenarios are considered: In the first scenario, the distance between two adjacent BANs is decreasing from 6 to 2 m, and the overall energy consumption of the BAN of interest is evaluated. On the other hand, the second scenario highlights the impact of the amount of nodes in an interfering BAN on the overall energy consumption. Simulations were conducted using Castalia 3.3 software. The obtained results showed that when two BANs are located next to each other, if the distance between them becomes smaller, or the amount of nodes in the interfering BAN exceeds that of the reference one, the energy consumption of the BAN of interest will increase, due to the highly experienced interference levels, especially at high data rates.

Interference avoidance and cancellation in automotive OFDM radar networks

With increasing use of millimeter-wave radars in driving safety applications, interference between vehicles becomes a significant issue. Moreover, oscillator imperfections and relative velocity effects induce inter-carrier interference (ICI) owing to frequency offset, leading to degradation of target detection. In this paper, time-frequency resources are divided into several orthogonal logical channels according to the time-frequency division (TFD) scheme. We propose a two-stage interference mitigation method. First, an interference avoidance technique is designed for each piece of radar equipment (RE) to select logical channels with the least ICI. Then, each RE reconstructs and cancels interference according to estimated parameters based on the proposed interference cancellation technique. Computer simulations reveal that the proposed interference avoidance technique can approximately achieve the performance of ground truth, especially when the number of interferers is small. In addition, noise enhancement effects can be effectively mitigated through the proposed cancellation technique.

A Review of Radio Resource Management in FemtoCell from Interference Control Perspective

A new and emerging technology called femtocell brings significant improvement in terms of better indoor coverage and higher data rate. Able to be installed and maintained by individual user, femtocell provides a cost effective solution to mobile operators to achieve higher network capacity. However, interference due to two-tier network structure introduces many challenges for successful femtocell deployment. In this article, we summarize various interference and resource management techniques proposed in the context of femtocell. Specifically, we focus on interference avoidance techniques. First, the overview of femtocells, its architecture, and common issues are presented. Next, various interference avoidance techniques are reviewed. At the end, several important research directions are outlined

Path planning method for longitudinal micromarks on blisk root-fillet with belt grinding

The blisk root-fillet exhibits a significant stress concentration in high-load operations, which has a significant influence on fatigue life and aerodynamic performance. To improve the static and dynamic fatigue life of the blisk in the thermal interaction environment, a method based on the anti-fatigue manufacturing principle is introduced to obtain longitudinal micromarks along the root-fillet. First, this paper proposes a belt grinding method that can obtain longitudinal micromarks, and the interference avoidance technique is analysed according to the allowance distribution and structural characteristics of the blisk root-fillet. Second, optimisation of the grinding path step is realised by means of the ‘point to point’ method, and de-noising and smoothing of the grinding vector are carried out. Finally, grinding experiment tests are carried out for the blisk root-fillet. The results demonstrate that the surface roughness is less than 0.4 μm following grinding, and the transition between the plane and fillet (blade profile—root-fillet—tenon plane) is smooth. Moreover, fine and uniform longitudinal micromarks are formed and the precision consistency is significantly improved, which proves the effectiveness of this method.

Interference management with mismatched partial channel state information

We study the fundamental limits of communications over multi-layer wireless networks where each node has only limited knowledge of the channel state information. In particular, we consider the scenario in which each source-destination pair has only enough information to perform optimally when other pairs do not interfere. Beyond that, the only other information available at each node is the global network connectivity. We propose a transmission strategy that solely relies on the available limited knowledge and combines coding with interference avoidance. We show that our proposed strategy goes well beyond the performance of interference avoidance techniques. We present an algebraic framework for the proposed transmission strategy based on which we provide a guarantee of the achievable rate. For several network topologies, we prove the optimality of our proposed strategy by providing information-theoretic outer-bounds.

Distributed User Association with Resource Partitioning in Heterogeneous Cellular Networks

To fully utilize the resources of heterogeneous cellular networks (HCNs), an effective approach that offloads users to the underloaded small cells from overloaded macrocells is widely advocated. However, this operation often leads to a bad result that the offloaded users achieve lower signal-to-interference-plus-noise-ratio (SINR) than these users in macrocells. Thus, some appropriate interference avoidance techniques should be adopted to partially alleviate the SINR degradation. For this, we consider the resource (frequency) partitioning that turns off some fraction of such resources in a macrocell. Naturally, an optimal offloading strategy should be closely coupled with resource partitioning, and in turn the optimal partition decides the offloading performance. In this paper, we propose a distributed association strategy with joint offloading and resource partitioning for HCNs. We reveal that load balancing, by itself, is insufficient, and additional resource partitioning is required to improve system performance. Meanwhile, we also show that, compared with the best power association and range extension association, the proposed scheme provides better association performance.

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.

Recent advances in interference management for wireless networks

Interference has been the central challenge for wireless networks. In wireless networking, the prevailing paradigm to handle interference is avoidance. Over time, many interference avoidance techniques have been proposed following this paradigm. Recently, research advances at the physical layer are allowing us to explore a new direction in interference management. The new direction is to allow interference to occur and exploit the desired information from interference, rather than avoiding interference completely. This new direction allows much higher utilization of radio channel and spectrum, and opens the door for a whole new perspective on how interference should be managed in a wireless network. This article offers a timely overview of recent advances in this exciting area, with a focus on its application in wireless LAN. We envision that the deployment of these new techniques will lead to dramatic change in the wireless networking paradigm, with profound impact on the future research direction for the wireless networking community.

Joint User Association and Resource Partitioning with QoS Support for Heterogeneous Cellular Networks

In heterogeneous cellular networks (HCNs), it is desirable that users in macrocells should be offloaded to small cells with less congested traffic. However, these offloaded users often have lower signal-to-interference-plus-noise-ratio (SINR) than them in macrocells. The degradation of SINR can be partially alleviated by adopting interference avoidance techniques, such as resource partitioning, whereby the macrocell lets some fraction of such resources be unavailable. Naturally, an optimal offloading scheme should be tightly coupled with resource partitioning; the optimal partition in turn decides the number of offloaded users. Moreover, in order to reduce the call blocking probability of users, we need to consider their quality of service (QoS) requirements. Thus, in this paper, we propose a distributed QoS-aware strategy with joint offloading and resource partitioning for HCNs. We reveal that load balancing, by itself, is insufficient, and additional resource partitioning should be considered to reduce the call blocking probability. Meanwhile, we also show that compared with the best power association and range expansion association, the proposed scheme has more obvious superiorities over call blocking probability.

Throughput and cost‐efficient interference cancelation strategies for the downlink of spectrum‐sharing Long Term Evolution heterogeneous networks

AbstractIn a heterogeneous network (HetNet), small cells such as femtocells considered in this work are deployed jointly with macrocells. This new cells' layer, when added to the network, generates interference, which could hamper neighboring macro‐user equipment (MUE) and femto‐user equipment (FUE) transmissions. In fact, this interference results in degradation of the network performance. In this paper, we propose a downlink interference cancelation (DL‐IC) strategy for spectrum‐sharing Long Term Evolution (LTE) HetNet. This DL‐IC strategy aims to reduce the interference impact on users by optimizing their received signal to interference plus noise ratio (SINR) using new utility functions for both FUEs and MUEs. These utility functions allow relaxation of the cancelation ratios in order to reduce implementation complexity while maximizing SINR, QoS, and throughput. We support by different system‐level simulations that both global network performance and user experience in terms of total throughput and received SNR or link‐level throughput, respectively, are significantly enhanced. Throughput gains achievable by the new DL‐IC strategy can reach as much as 200% against a homogeneous LTE network without IC along with an extra 48% per additional femtocell base station against a basic spectrum‐sharing LTE HetNet without IC. These performance figures are shown to surpass those achieved by interference avoidance techniques using either power or frequency resource allocation. Copyright © 2014 John Wiley & Sons, Ltd.

Autonomous Schemes for Inter-cell Interference Coordination in the Downlink of LTE Systems

Inter-cell interference (ICI) is one of the key challenges that limit the performance of Long Term Evolution and Long Term Evolution Advanced cellular systems. One approach to deal with ICI is through interference avoidance. Unlike static avoidance techniques where a-priori frequency planning and/or explicit inter-cell coordination is used, dynamic avoidance techniques rely on adapting its frequency planning and allocation based on the current state of the network. However, this improvement in performance comes with the cost of an increased complexity due to the coordination and alignments needed among the base stations (eNB) to manage and allocate channels among the users. Accordingly, autonomous ICI coordination techniques are receiving much interest among the various interference avoidance techniques. In this paper, we propose an autonomous self-adaptive scheme (SA, for short) for radio resource management and interference coordination. We then extend the proposed scheme to become self-adaptive power-aware (SAPA) in order to optimize and reduce the transmission power of the eNBs. A key feature in the proposed schemes is that all computations are independent of the number of users and cells in the network. This allows the proposed schemes to adapt to networks of any size and with an arbitrary number of users. Extensive simulation confirms that the proposed SA scheme ensures efficient frequency reuse patterns that lead to significant performance improvements in the throughput of the edge users without affecting other users. Moreover, the SAPA scheme achieves significant improvement in the power efficiency, while maintaining the throughput enhancements achieved by the SA scheme for both center and edge users.

On Interference Avoidance Through Inter-Cell Interference Coordination (ICIC) Based on OFDMA Mobile Systems

The widely accepted OFDMA air interface technology has recently been adopted in most mobile standards by the wireless industry. However, similar to other frequency-time multiplexed systems, their performance is limited by inter-cell interference. To address this performance degradation, interference mitigation can be employed to maximize the potential capacity of such interference-limited systems. This paper surveys key issues in mitigating interference and gives an overview of the recent developments of a promising mitigation technique, namely, interference avoidance through inter-cell interference coordination (ICIC). By using optimization theory, an ICIC problem is formulated in a multi-cell OFDMA-based system and some research directions in simplifying the problem and associated challenges are given. Furthermore, we present the main trends of interference avoidance techniques that can be incorporated in the main ICIC formulation. Although this paper focuses on 3GPP LTE/LTE-A mobile networks in the downlink, a similar framework can be applied for any typical multi-cellular environment based on OFDMA technology. Some promising future directions are identified and, finally, the state-of-the-art interference avoidance techniques are compared under LTE-system parameters.

Interference Avoidance Techniques for Closed Access Small Cells Networks

This paper investigates the impact of small cells networks deployment in a typical residential environment. First we will present some aspects with regard to small cells coverage area when deployed in a macrocell sector area. Using the observations with regards to coverage we will further investigate the deployment of a residential femtocell network, implemented in closed access form. The paper proposes two algorithms in order to reduce the interference level at the macrocell user site, considering that the operator owns at least two carrier frequencies which will be used for both the macrocellular and femtocellular layers. The performances of the two proposed algorithms are presented in comparison with the case when no interference mitigation methods are implemented. The obtained results show a significant improvement in the signal to interference and noise ratio, obtained at the user location.

Mobility-Aware Interference Avoidance Scheme for Vehicular WLANs

Communication technology of future networks is predicted to provide a large variety of services including WiFi service in vehicular network. In this paper, we assume that vehicles are embedded with WiMAX antenna and in-vehicle terminals receive WiMAX traffic through WiFi interface. This assumption will impose severe performance degradation due to interference among mobile BSSs when WiFi access points (APs) are densely located. Existing interference avoidance techniques cannot properly resolve the above problems and do not cope with dynamically moving vehicular scenario since they focus only on the fixed network topology. In this paper, we propose a mobility-aware interference avoidance scheme for WiFi services. The proposed scheme computes the interference duration by exploiting mobility vector and location information of neighboring APs. If the interference duration is not negligible, our scheme searches for another channel in order to avoid interference. However, if the interference duration is negligible, our scheme continues to use the channel to reduce switching overhead. To measure the effectiveness of the proposed scheme against other existing techniques, we evaluated performance by using OPNET simulator. Through the simulation, we obtained about 60% reduction in the maximum interference frequency and about 67% improvement in throughput. Furthermore, our scheme provides fair channel usage.

An Interfering Signal Detection Technique Using an Ultra Wideband Chirp Template Waveform

This paper discusses a coexisting signal detection technique for sharing the spectrum of an Ultra Wideband (UWB) radio with other radio systems. In some countries' regulations, the Detection and Avoidance technique is required to be implemented in UWB systems so they do not interfere with other radio systems. In most interference avoidance techniques it is necessary to detect emissions of the interfering system and the interfering bands. In this paper, correlation detection is applied for interfering signal detection without band pass filters. In the detector, a Chirp-UWB is prepared as a template waveform. The signal received before UWB communications is correlated with the Chirp-UWB template waveform, and is then integrated. The integral period is decided from the sweep function of the Chirp-UWB and the interfering bands. Therefore the detection technique can detect arbitrary frequency band signals by modifying the integral period. The sweep function of the Chirp-UWB also improves the detection performance. A sine function is adopted for the sweep function of the chirp. The miss Detection Error Rate and False Alarm Rate are evaluated to show the effectiveness of the proposed interference detection technique.

Intracell Handover for Interference and Handover Mitigation in OFDMA Two-Tier Macrocell-Femtocell Networks

There are two main access policies (open and closed) to Femtocell Access Points (FAPs), being closed access the customers favorite. However, closed access is the root cause of crosstier interference in cochannel deployments of two-tier networks (i.e., macrocells and femtocells). Further, the effect of this problem is remarkably serious in the downlink of outdoor users not subscribed to any femtocell. Open access has been considered as a potential solution to this problem. However, this increases signaling in the network due to the elevated number of HandOvers (HOs) that mobile users have to perform. Therefore, this paper proposes an interference avoidance technique based on the use of Intracell HandOvers (IHOs) in Orthogonal Frequency Division Multiple Access (OFDMA) femtocells. It is shown that a proper combination of IHO and power control techniques reduces the outage probability for nonsubscribers compared with that of closed and open access. In addition, the impact of several network parameters such as the femtocell penetration is also considered in the analysis.

A Novel Interference Avoidance Technique on Mobile Wireless Routers Using IEEE802.11n PSMP

This paper proposes an interference avoidance technique that allows wireless device with similar frequency bands to be operated adjacent to each other for compact mobile wireless routers (MWRs). This MWR implements two devices of Wireless LAN (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX). The MWR connects WLAN terminals to the backbone network by using WiMAX-WLAN relay. Generally, different frequency channels are assigned for the wireless systems assign in order not to interfere among multiple systems. However, mutual system interference is generated if the space between each device is very close and if the frequency using each system is adjacent. To suppress this interference, this paper proposes a novel interference avoidance technique that leverages IEEE802.11n Power Save Multi-Poll (PSMP). First, we clarify the conditions that raise the issues of mutual interference by experiment. Simulations are conducted to show that the proposed scheme outperforms the conventional schemes. Finally, the effectiveness of the proposed scheme is shown by the computer simulation.