Interference Avoidance Scheme Research Articles

Adaptive Interference Avoidance and Mode Selection Scheme for D2D-Enabled Small Cells in 5G-IIoT Networks

Adaptive Interference Avoidance and Mode Selection Scheme for D2D-Enabled Small Cells in 5G-IIoT Networks

Long-distance anti-interference self-feedback regulating fire emergency speaker system

Modern building groups are getting larger and larger, and the lines are getting longer and longer, which directly leads to two major problems. One is that the volume of loudspeakers at the end of the line cannot meet the requirements of normal use. If the power is increased, the loudspeakers near the line will howl and self-excite too much. Second, the power of the power amplifier and the number of loudspeakers cannot be matched exactly. It is urgent to develop fire-fighting loudspeakers or emergency broadcasting systems that can be applied to long-distance transmission, having strong anti-interference ability, and can realize automatic adjustment through feedback. This paper develops a set of intelligent fire broadcast system based on distributed power amplifier, which can realize the following functions: it can connect with other platforms and systems through the big data platform, realize cross-platform, cross-system real-time long-distance playback of the broadcasting system, and solve the problem of terminal volume. By switching channels, power control, etc. Using the near-end strategy optimization algorithm based on tailoring, the optimal joint interference avoidance strategy of the system is obtained to solve the problem of environmental noise interference. Based on the deep reinforcement learning algorithm, the problem of matching the power amplifier power and the number of speakers is solved.

Multilevel Topological Interference Management: A TIM-TIN Perspective

The robust principles of treating interference as noise (TIN) when it is sufficiently weak, and avoiding it when it is not, form the background of this work. Combining TIN with the topological interference management (TIM) framework that identifies optimal interference avoidance schemes, we formulate a TIM-TIN problem for multilevel topological interference management, wherein only a coarse knowledge of channel strengths and no knowledge of channel phases is available to transmitters. To address the TIM-TIN problem, we first propose an analytical baseline approach, which decomposes a network into TIN and TIM components, allocates the signal power levels to each user in the TIN component, allocates signal vector space dimensions to each user in the TIM component, and guarantees that the product of the two is an achievable number of signal dimensions available to each user in the original network. Next, a distributed numerical algorithm called ZEST is developed. The convergence of the algorithm is demonstrated, leading to the duality of the TIM-TIN problem in terms of generalized degrees-of-freedom (GDoF). Numerical results are also provided to demonstrate the superior sum-rate performance and fast convergence of ZEST.

RoF distributed antenna architecture- and reinforcement learning-empowered real-time EMI immunity for highly reliable railway communication.

Highly reliable wireless train-ground communication immune to the electromagnetic interferences (EMIs) is of critical importance for the security and efficiency of high-speed railways (HSRs). However, the rapid development of HSRs (>52,000 km all over the world) brings great challenges on the conventional EMIs mitigation strategies featuring non-real-time and passive. In this paper, the convergence of radio-over-fiber distributed antenna architecture (RoF-DAA) and reinforcement learning technologies is explored to empower a real-time, cognitive and efficient wireless communication solution for HSRs, with strong immunity to EMIs. A centralized communication system utilizes the RoF-DAA to connect the center station (CS) and distributed remote radio units (RRUs) along with the railway track-sides to collect electromagnetic signals from environments. Real-time recognition of EMIs and interactions between the CS and RRUs are enabled by the RoF link featuring broad bandwidth and low transmission loss. An intelligent proactive interference avoidance scheme is proposed to perform EMI-immunity wireless communication. Then an improved Win or learn Fast-Policy Hill Climbing (WoLF-PHC) multi-agent reinforcement learning algorithm is adopted to dynamically select and switch the operation frequency bands of RRUs in a self-adaptive mode, avoiding the frequency channel contaminated by the EMIs. In proof-of-concept experiments and simulations, EMIs towards a single RRU and multiple RRUs in the same cluster and towards two adjacent RRUs in distinct clusters are effectively avoided for the Global System for Mobile communications-Railway (GSM-R) system in HSRs. The proposed system has a superior performance in terms of circumventing either static or dynamic EMIs, serving as an improved cognitive radio scheme to ensuring high security and high efficiency railway communication.

An Overview and Mechanism for the Coexistence of 5G NR-U (New Radio Unlicensed) in the Millimeter-Wave Spectrum for Indoor Small Cells

In this paper, we first give an overview of the coexistence of cellular with IEEE 802.11 technologies in the unlicensed bands. We then present a coexistence mechanism for Fifth-Generation (5G) New Radio on Unlicensed (NR-U) small cells located within buildings to coexist with the IEEE 802.11ad/ay, also termed as Wireless Gigabit (WiGig). Small cells are dual-band enabled operating in the 60 GHz unlicensed and 28 GHz licensed millimeter-wave (mmW) bands. We develop an interference avoidance scheme in the time domain to avoid cochannel interference (CCI) between in-building NR-U small cells and WiGig access points (APs). We then derive average capacity, spectral efficiency (SE), and energy efficiency (EE) performance metrics of in-building small cells. Extensive system-level numerical and simulation results and analyses are carried out for a number of variants of NR-U, including NR standalone, NR-U standalone, and NR-U anchored. We also analyze the impact of the spatial reuse of both mmW spectra of multiple NR-U anchored operators with a WiGig operator. It is shown that NR-U anchored provides the best average capacity and EE performances, whereas NR-U standalone provides the best SE performance. Moreover, both vertical spatial reuse intrabuilding level and horizontal spatial reuse interbuilding level of mmW spectra in small cells of an NR-U anchored can improve its SE and EE performances. Finally, we show that by choosing appropriate values of vertical and horizontal spatial reuse factors, the proposed coexistence mechanism can achieve the expected SE and EE requirements for the future Sixth-Generation (6G) mobile networks.

Research on large-scale additive manufacturing based on multi-robot collaboration technology

Additive manufacturing is considered a promising technology for many applications, such as in the construction industry. However, the size of a design is constrained by the chamber volume of the 3D printer, and large-scale additive manufacturing technology with flexible equipment is still unproven. This paper proposes a large-scale 3D printing system composed of multiple robots working in collaboration. For this flexible and extensible 3D printing system, the influences of the multi-robot layout on the maximum reachable area and the geometry adaptability are discussed. Furthermore, a printer task optimized scheduling algorithm based on efficiency egalitarianism is proposed in this paper, and a robot interference avoidance strategy is designed by dividing the printing layer into several safe areas and interference areas. Collaborative printing experiments are implemented on the multi-robot platform, and the results show that the efficiency improvement with four robots exceeds 73 % compared with a general printing method.

Proactive real-time interference avoidance in a 5G millimeter-wave over fiber mobile fronthaul using SARSA reinforcement learning

We propose and experimentally demonstrate a proactive real-time interference avoidance scheme using SARSA reinforcement learning (RL) in a millimeter-wave over a fiber mobile fronthaul system. The RL consists of three core factors, including state, action, and reward. The state is defined as a discretized value from the center frequency, the left, right, and center sub-EVM of the signal. We use five actions to shift the signal frequency in the proposed scheme, which is -20, -10, 0, 10, and 20MHz, for the RL agent to choose the action to avoid the dynamic interference. For the agent to learn from the experience, the reward is defined as the log value of BER difference between the past and the present state. The RL-based approach is an online learning algorithm, which can learn in real time based on environmental feedback. Besides, the agent can learn from past experience owing to the Q-value table, which makes it act intelligently when facing a similar situation again. We verify the capability of the proposed scheme under both fixed and dynamic interference scenarios. The agent demonstrates an efficient intelligent mechanism to avoid the interference, which provides a promising solution for proactive interference mitigation in the 5G mobile fronthaul network.

Performance Analysis and Optimization of UAV Integrated Terrestrial Cellular Network

Unmanned aerial vehicles (UAVs) have been extensively applied as aerial access points to assist the terrestrial wireless network. Despite the inherent potential, nevertheless, it still remains to explore whether the gain of UAV access points (UAPs) could be fully harvested, which is critically dependent on the factors including the flight altitude and deployment density of UAPs. In this light, we investigate the performance of a downlink UAV integrated terrestrial cellular network (UTCN) and analytically study the influence of varying UAP altitude and density on the spatial throughput (ST) of UTCN. In particular, we obtain the UAP altitude upper bound, below which more line-of-sight (LOS) connections could be provided to improve network ST. Otherwise, cross-layer interference over the LOS paths becomes dominant, which results in significant degradation of network ST. More importantly, we reveal the limitation of the application of UAPs by showing that there exists a critical UAP density, beyond which network ST would encounter a rapid decrease. To fully exploit the potential of UAPs, we further tailor a probabilistic interference avoidance scheme and study the optimization of the UAP activated probability. Remarkably, network ST could be substantially improved using the optimized activated probability, i.e., network ST could increase with the growing UAP density and converge to a positive constant instead of zero in the dense UAP regime. Therefore, the results of this paper could provide insight on the deployment and optimization of UTCN.

Topological Interference Management for MIMO Interference Broadcast Channels

In this paper, we investigate the topological interference management (TIM) for MIMO interference broadcast channels (IBC) under the fixed topology, where only topology information is needed to cancel the inter-cell interference (ICI). For the single user case, where the MIMO IBC network is reduced to the MIMO interference channel (IC) networks, we propose one novel TIM scheme by exploiting the solution to the corresponding SISO IC TIM based on topology information. And also, we present one theorem to characterize the achievable degrees of freedom (DoFs). For the multiple user case, assuming that each BS not only knows topology information but also knows the channel state information at transmitters (CSIT) within its own cell, we propose two novel TIM schemes, i.e., the virtual user compression-based scheme and the virtual base station extension-based scheme. For each scheme, we design transceivers to cancel both the ICI only based on the topology information by exploiting the solution to the corresponding SISO IC TIM and the multiple user interference (MUI) within its own cell based on the CSIT. Furthermore, we present one theorem to characterize the achievable DoF, respectively. Moreover, we prove that the DoF achieved by the virtual base station extension-based scheme is higher than or equal to that achieved by the virtual user compression-based scheme. Hence, the achievable DoF of MIMO IBC TIM is lower bounded by the optimal DoF attainable for the base station extension scheme. Furthermore, the numerical results show that our schemes can achieve significant performance gain against the traditional interference avoidance scheme.

Clustering-Based Channel Allocation Scheme for Neighborhood Area Network in a Cognitive Radio Based Smart Grid Communication

Cognitive radio ((CR))-based standards are apt to cater the diverse communication requirements for the humongous volume of data generated by Smart Grid applications. Although CR technology is one of the most promising techniques to increase the spectral efficiency of any wireless communication network, efficient spectrum allocation among secondary user (SUs) in different application scenarios remains an intriguing area for researchers. In this paper, we propose a clustering-based approach to deal with channel allocation ((CA)) problem among SUs considering practical constraints in SG environment. We first present a simple CR based SG communication network architecture by dividing the service area into groups of SUs called neighborhood area network clusters, depending upon the distance of Smart Meters from data concentrator unit. Then we formulate a multiple constraint NP-hard CA problem using interference avoidance strategy by considering two practical scenarios: fairness-based allocation and priority-based allocation. We then propose our CA algorithm based on cat swarm optimization to eliminate the severe integer constraints of the problem under consideration. We simulate the two above-mentioned practical scenarios to measure a number of allocations per SU, Jain’s Fairness Index and per user average rewards. Moreover, conventional average user rewards are compared for a varying number of channels, SUs, and rounds to evaluate the performance of proposed CA scheme. The results indicate that our proposed CA algorithm works well, for both fairness-based and priority-based cases.

A frequency hopping method for spatial RFID/WiFi/Bluetooth scheduling in agricultural IoT

Currently, a variety of wireless modules are purposed for different criteria in the area of the agricultural internet of things; however, there is a lack of appropriate methods enabling these wireless modules to operate in the same frequency band. The goal of this paper is to make a very thorough quantitative analysis on the theoretical maximum collision time and collision probability of WiFi or Bluetooth network with RFID interferers. We propose the interference avoidance scheme which requires the knowledge of the theoretical maximum collision time and collision probability between RFID and WiFi/Bluetooth packets. This scheme generates an optimal channel based on the current usage of the adjacent frequency channels thereby reducing the interference. We also propose two solutions from this scheme: a frequency hopping combined with white space exploitation method and an intelligent frequency hopping scheme; for maintaining a quality connection of the WiFi or Bluetooth network in the presence of heavy RFID interferers. We implement a hybrid backscatter-based RFID architecture in existence of the WiFi/Bluetooth infrastructure for efficient operations within the 2.4 GHz ISM band. Results obtained are very encouraging and indicate that quantifying the maximum collision time and collision probability is a vital step for the interference avoidance scheme, which can be adopted in the avoidance of the interference from RFID modules.

Empowering Device-to-Device Networks with Cross-Link Interference Management

Device-to-device (D2D) communications is an emerging service model that is currently under standardization by 3GPP. While D2D offloading has a great potential to relieve increasingly congested cellular networks, its benefits, however, come at a cost, namely interference. Most of the prevailing D2D designs conservatively avoid interference via either spectrum resource allocation or power control. These designs, however, do not exploit spatial degrees of freedom (DoF), which are inherently supported by multi-antenna devices. In this work, we present $\sf {MD2D}$ , a multiuser D2D system that embraces concurrent D2D transmissions, while leveraging MIMO techniques to actively eliminate interference across D2D pairs. $\sf{MD2D}$ has a systematic methodology that checks whether the antenna combination in a D2D network is capable of eliminating cross-pair interference and, thereby, ensuring interference-free concurrent transmissions. If the interference can be eliminated, then $\sf{MD2D}$ applies a bucket-based DoF assignment algorithm to determine an effective antenna usage configuration that handles the interference. We evaluate our design via testbed experiments and large-scale simulations. The results show that, as compared to the traditional interference avoidance scheme, $\sf{MD2D}$ improves the throughput by 87.39 and 218.84 percent in a three-pair testbed and in large-scale simulations, respectively.

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.

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.

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.

Throughput enhancement of IEEE 802.11ad through space‐time division multiple access scheduling of multiple co‐channel networks

60-GHz millimetre-wave (mm-wave) communication is gradually becoming a promising candidate for the next generation wireless system to meet the demands of mobile applications. To compensate for high path loss, directional links are established in mm-wave communication system, which adds opportunity for spatial reuse. As one of its most promising protocols for commercial production, IEEE 802.11ad standard provides a mechanism to support space-time division multiple access (STDMA) within a single network. However, the interference level among different co-channel networks is much lower than that inside a network, which provides greater potential for spatial reuse. In this study, based on the architecture and timing structure of IEEE 802.11ad, the authors propose a spatial reuse strategy among multiple co-channel networks. They formulate the problem as a mixed-integer non-linear programming problem, and then propose an inter-network STDMA scheduling algorithm, which considers clustering frame structure in IEEE 802.11ad, and combines greedy principle and mutual interference avoidance strategy. Extensive simulation results have shown that the proposed scheme enlarges total throughput in comparison with STDMA inside each network, as well as non-STDMA scheme. Meanwhile, it achieves the lowest packet loss rate under heavy traffic load.

Spatial Reuse Precoding for Scalable Downlink Networks

In this paper, we develop linear precoding schemes for MIMO downlink networks with quasi-static channels that are scalable, in the sense that they can be implemented with moderate complexity in networks with increasing numbers of cells and users. The principle that underlies the proposed precoding scheme is to exploit the decomposable structure of the equivalent channel matrix by designing the precoders at the base stations to be decomposable as well. Thus, the channel matrices and the designed precoders can be expressed as the Kronecker product of constituent matrices. For networks with a finite number of cells, the proposed structured precoding schemes enable inter-cell interference cancellation without the need for inter-cell feedback and provide more degrees of freedom than conventional interference avoidance schemes, while incurring a latency that grows only linearly in the number of cells. The proposed structured precoding schemes also enable a scaling approach for unbounded networks that we have called “spatial reuse precoding” (SRP). SRP is based on the observation that at each receiver, the signals from interfering sources that employ the same precoder arrive in the same subspace, regardless of the particular channel matrices between the interfering sources and the receiver. In some typical cellular architectures we show how an SRP scheme based on the proposed structured precoders can be designed to eliminate the dominant sources of interference without requiring cooperation between cells. In addition, we show that SRP can provide substantial performance gains in certain heterogeneous networks.

Transmission scheduling in optical CDMA networks using hybridized overlap and threshold (HOT) scheduling algorithm

The bane of optical network is multiuser interference as a result of codewords overlap from different nodes simultaneously transmitting. Transmission scheduling is a good interference avoidance scheme which helps prevent throughput degradation at high offered load in an optical code division multiple access local area network. Interference avoidance consists of state estimation and transmission scheduling. This work examines different scheduling algorithms and parameter variations. This work investigated the performance of three scheduling algorithms (Pure Selfish Scheduling, Threshold Scheduling and Overlap Section Scheduling) against the ALOHA CDMA and our novel Hybrid--Hybridized Overlap and Threshold Scheduling--HOT algorithms using the modified padded prime codeset. The performance of the scheduling algorithms are measured in terms of its normalized network throughput, packet error rate and the average number of codewords allow into the line against the normalized offered load. The analysis shows that under this condition, the Hybridized Overlap--Threshold scheduling perform best and has throughputs as high as the 52 % with nearly zero packet error rate while the non-scheduled algorithm produce a throughput as low as 10 % and very high error rate at maximum offered load. Overall, the Threshold Scheduling and HOT algorithm are head to head and performed best in terms of normalized network throughput, however the HOT scheduling is best in terms of the packet error rate. Analysis also shows that the throughput is not affected by changes in codeset length and the mean packet size but it is affected by changes in the codeset weight. The study also analyzes the performance of the network under a bimodal packet distribution and with the Prime code codeset family. Optical Orthogonal Codeset and the Prime codeset family are used in the study under the assumption of perfect state estimation; that all nodes have the same view of the network and the transmission lines and the distance between the nodes and the central star coupler is assumed to be zero. A novel hybrid Scheduling Algorithm, the HOT Scheduling which proved better than traditional Scheduling Algorithms is peddled here.

An Adaptive WLAN Interference Mitigation Scheme for ZigBee Sensor Networks

We propose an adaptive interference avoidance scheme that enhances the performance of ZigBee networks by adapting ZigBees' transmissions to measured wireless local area network (WLAN) interference. Our proposed algorithm is based on a stochastic analysis of ZigBee operation that is interfered with by WLAN transmission, given ZigBee and WLAN channels are overlaid in the industrial, scientific, and medical (ISM) band. We assume that WLAN devices have higher transmission power than ZigBee devices. Then, the high transmission power of WLAN devices causes the capture effect when WLAN and ZigBee transmit simultaneously. On the other hand, ZigBee performs backoff during clear channel assessment (CCA) operation if the WLAN is transmitting its frames on the channel. We adopt a widely used WLAN queueing/transmission model that is based on a Markov chain concept. We model a ZigBee device's operation using the Markov chain that includes WLAN interference statistically derived from the WLAN queueing/transmission model. Our proposed algorithm is evaluated in a simulated ZigBee network in the presence of varying WLAN interference. Numerical results show that our WLAN interference mitigation scheme finds the ZigBee control parameters, among a candidate set, which enhances ZigBee network performance compared to the conventional ZigBee operation.

무선 USB 시스템에서 간섭 회피를 위한 채널 스케쥴링 기법

Wireless universal serial bus (WUSB) is the USB technology merged with WiMedia PHY/MAC. WUSB can be applied to wireless persanal area network (WPAN) applications as well as PAN applications like wired USB. Because numerous WUSB networks operate independently for each application, data conflict can occur between adjacent networks. To avoid data conflict, the resource in a different time zone can be utilized. However, if devices in a network increase, available resources in the network decrease, and then the lack of resources necessary to provide service can occur. To solve this problem, we propose interference avoidance scheme for WUSB systems.