Interference Management Scheme Research Articles

A Survey of Resource Management Toward 5G Radio Access Networks

The next generation 5G radio access network (RAN) system is believed to be a true world wide wireless web (WWWW). This is because such system will seamlessly and ubiquitously connect everything, and support at least 1000-fold traffic volumes, 100 billion connected wireless devices, and diversified use cases as well as quality of service (QoS) requirements (e.g., reliability, latency, data rates, coverage, security, and privacy) of multimedia applications by 2020. Recently, a number of research challenges including the explosive growth in mobile traffic volumes, unprecedented connected devices, and diversified use cases have been identified for the 5G RAN systems. In addition, specific technologies such as multitier communication, massive MIMOs, mmWave backhauling, extreme densifications of nodes (UDNs), full-duplex communications (FDCs), and energy harvesting techniques have emerged in the literature to resolve some of these challenges of the 5G RAN systems. However, the research activities defining specific technical advancements for 5G RAN systems are yet to continue in the next half decade before specifications for standardization and commercialization are concluded. Motivated by the limited number of existing surveys of such technical advancements in a broader perspective (i.e., interference, spectrum-efficient, and energy-efficient management schemes), this paper seeks to take stock of state-of-the-art (SOTA) on such technical developments. Our attention focuses on relevant radio interference and resource management (RIRM) schemes that have been proposed in the last five years. Our contribution lies in the analysis, synthesis, and summarized alignments of the conventional RIRM schemes toward overcoming the identified challenges for the $5G$ RAN systems. Finally, the review highlights a number of open research issues deduced from recently proposed RIRM schemes.

Modelling Spatial Distribution of the Carob Tree (Ceratonia siliqua L.) in Azilal Province, Morocco

Factors determining forest species distribution include, in addition to external factors such as human interference and environmental management strategies, also soil and hydrological characteristics and climate conditions in any given areas. Modelling<strong> </strong>distribution has practical application in forest conservation and management, and help decision makers to develop strategies aimed at forest restoration, development of mountainous areas and the continuous and sustainable provision of forest-related services. Species distribution modelling (SDM) can be used for predicting species distribution based on tree presence records and on a number of environmental predictors. In this study we used MaxEnt for niche modelling in predicting carob (<em>Ceratonia siliqua </em>L.) trees spatial distribution in the Province of Azilal in Morocco. The results obtained show that a large area of the mountain regions is suitable for the expansion of <em>Ceratonia siliqua</em> stands. These findings will help decision makers in forest planning to better identify suitable sites for carob tree plantations and assess the potential of the exiting populations.

On Characterization of Feasible Interference Regions in Cognitive Radio Networks

In an underlay cognitive radio network (CRN), in order to guarantee that all primary users (PUs) achieve their target-signal-to-interference-plus-noise ratios (target-SINRs), the interference caused by all secondary users (SUs) to the primary receiving-points should be controlled. To do so, the feasible cognitive interference region (FCIR), i.e., the region for allowable values of interference at all of the primary receiving-points, which guarantee the protection of the PUs, needs to be formally characterized. In the state-of-the-art interference management schemes for underlay CRNs, it is considered that all PUs are protected if the cognitive interference for each primary receiving-point is lower than a maximum threshold, the so called interference temperature limit (ITL) for the corresponding receiving-point. This is assumed to be fixed and independent of ITL values for other primary receiving-points, which corresponds to a box-like FCIR. In this paper, we characterize the FCIR for uplink transmissions in cellular CRNs and for direct transmissions in ad-hoc CRNs. We show that the FCIR is in fact a polyhedron (i.e., the maximum feasible cognitive interference threshold for each primary receiving-point is not a constant, and it depends on that for the other primary receiving-points). Therefore, in practical interference management algorithms, it is not proper to consider a constant and independent ITL value for each of the primary receiving-points. This finding would significantly affect the design of practical interference management schemes for CRNs. To demonstrate this, based on the characterized FCIR, we propose two power control algorithms to find the maximum number of admitted SUs and the maximum aggregate throughput of the SUs in infeasible and feasible CRNs, respectively. For two distinct objectives, our proposed interference management schemes outperform the existing ones. The numerical results also demonstrate how the assumption of fixed ITL values leads to poor performance measures in CRNs.

Resource allocation and interference management strategies for inband relaying in LTE-A

Relaying is seen as a cost-effective solution to increase the coverage and improve the capacity for long term evolution-advanced networks. However, the resource allocation among different nodes and links and the inter-cell interference coordination (ICIC) are important challenges in order to make the most of the potential benefits of relay deployments. This paper focuses on Type 1 half-duplex inband relaying. Several strategies related to radio resource partition and frequency reuse between nodes and links are reviewed, proposed and evaluated in this work, considering the real impact of the overhead introduced by backhaul links on the system performance and the ICIC schemes applied among macrocells. We also propose a way to multiplex the transmissions addressed to several relay nodes with the aim of improving the resource allocation and the network performance.

Interference management schemes for multi‐user cooperative wireless networks

AbstractCooperative communication is a promising technique for future wireless networks. It can be used in improving communication reliability and enhancing spectrum efficiency by using the broadcast nature of radio communication and exploiting cooperative diversity. However, its performance gain degrades in the presence of co‐channel interference, which makes it essential to propose interference mitigation schemes. In this paper, we introduce three cooperative communication schemes with interference management for multi‐user cooperative wireless networks. The first scheme (best relay selection) is used as a performance benchmark because it completely avoids the interference problem by using the Frequency‐Division Multiple Access technique. The second scheme (best available relay selection) maximizes the received signal‐to‐noise ratio while keeping the interference levels below a certain threshold, and the third scheme (General Order Relay and User Selection) is based on iterative resource allocation algorithm. We derive exact closed‐form expressions of average bit error probability, outage probability, and average consumed power for the proposed schemes. Simulations are used to validate the analytical results. The results confirm the advantage of the proposed cooperation schemes in enhancing the system performance and improving the interference management. Copyright © 2015 John Wiley & Sons, Ltd.

Interference Networks With no CSIT: Impact of Topology

We consider partially connected $K$ -user interference networks, where the transmitters have no knowledge about the channel gain values, but they are aware of network topology. We introduce several linear algebraic and graph theoretic concepts to derive new topology-based outer bounds and inner bounds on the symmetric degrees-of-freedom of these networks. We evaluate our bounds for two classes of networks to demonstrate their tightness for most networks in these classes, quantify the gain of our inner bounds over benchmark interference management strategies, and illustrate the effect of network topology on these gains.

Li-Fi: Light fidelity-a survey

Visible light communication (VLC), which uses a vast unregulated and free light spectrum, has emerged to be a viable solution to overcome the spectrum crisis of radio frequency. Light fidelity (Li-Fi) is an optical networked communication in the subset of VLC to offload the mobile data traffics which offers many advantages at indoor scenario. In this article, we survey the key technologies for realizing Li-Fi and present the sate-of-the-art on each aspect, such as: indoor optical wireless channel model, the VLC modulation techniques with user satisfaction, OFDM in VLC, optical MIMO, optical spatial modulation, multiple user access, resource allocation, interference management and hybrid Li-Fi schemes. Some challenges and future work that need to be solved in the area are also described.

The Transitional Behavior of Interference in Millimeter Wave Networks and Its Impact on Medium Access Control

Millimeter-wave (mmWave) communication systems use a large number of antenna elements that can potentially overcome severe channel attenuation by narrow beamforming. Narrow-beam operation in mmWave networks also reduces multiuser interference, introducing the concept of noise-limited wireless networks as opposed to interference-limited ones. The noise-limited or interference-limited regime heavily reflects on the medium access control (MAC) layer throughput and on proper resource allocation and interference management strategies. Yet, these regimes are ignored in current approaches to mmWave MAC layer design, with the potential disastrous consequences on the communication performance. In this paper, we investigate these regimes in terms of collision probability and throughput. We derive tractable closed-form expressions for the collision probability and MAC layer throughput of mmWave ad hoc networks, operating under slotted ALOHA. The new analysis reveals that mmWave networks may exhibit a non-negligible transitional behavior from a noise-limited regime to an interference-limited one, depending on the density of the transmitters, density and size of obstacles, transmission probability, operating beamwidth, and transmission power. Such transitional behavior necessitates a new framework of adaptive hybrid resource allocation procedure, containing both contention-based and contention-free phases with on-demand realization of the contention-free phase. Moreover, the conventional collision avoidance procedure in the contention-based phase should be revisited, due to the transitional behavior of interference, to maximize throughput/delay performance of mmWave networks. We conclude that, unless proper hybrid schemes are investigated, the severity of the transitional behavior may significantly reduce throughput/delay performance of mmWave networks.

Price bargaining based on the Stackelberg game in two‐tier orthogonal frequency division multiple access femtocell networks

This study presents a solution to the interference management scheme and resource allocation strategy for the two-tier femtocell networks, where the femtocell users (FUEs) share the same frequency band with the existing macrocell users. It is assumed that the FUEs compete for the available spectrum to fulfil their own communication. And the macrocell base station protects itself by pricing the interference from the FUEs, which formulates the Stackelberg game. In this study, two effective pricing schemes, uniform pricing scheme and non-uniform pricing scheme, combining with admission control are proposed to maximise the revenues and protect the quality of service requirements. The Stackelberg equilibriums for the proposed games are investigated. Besides, a novel distributed interference pricing algorithm is provided for the uniform pricing case. Numerical results show that, in two-tier femtocell networks with shared spectrum, the proposed pricing schemes are effective in resource allocation and performance protection.

Power and Contention Control Scheme: As a Good Candidate for Interference Modeling in Cognitive Radio Network

Due to the ever growing need for spectrum, the cognitive radio (CR) has been proposed to improve the radio spectrum utilization. In this scenario, the secondary users (SU) are permitted to share spectrum with the licensed primary users (SU) with a strict condition that they do not cause harmful interference to the cognitive network. In this work, we have proposed an interference model for cognitive radio network that utilizes power or contention control interference management schemes. We derived the probability density function (PDF) with the power control scheme, where the power of transmission of the CR transmitter is guided by the power control law and also with contention control scheme that has a fixed transmission power for all CR transmitter controlled by a contention control protocol. This protocol makes a decision on which CR transmitter can transmit at any point in time. In this work, we have shown that power and contention control schemes are good candidates for interference modeling in cognitive radio system. The impact of the unknown location of the primary receiver on the resulting interference generated by the CR transmitters was investigated and the results shows that the challenges of the hidden primary receivers lead to higher CR-primary interference in respect to higher mean and variance. Finally, the presented results show power control and the contention control scheme are good candidates in reducing the interference generated by the cognitive radio network.

Femtocell Subband Selection Method for Managing Cross- and Co-tier Interference in a Femtocell Overlaid Cellular Network

The femtocell overlaid cellular network (FOCN) has been used to enhance the capacity of existing cellular systems. To obtain the desired system performance, both cross-tier interference and co-tier interference in an FOCN need to be managed. This paper proposes an interference management scheme that adaptively constructs a femtocell cluster, which is a group of femtocell base stations that share the same frequency band. The performance evaluation shows that the proposed scheme can enhance the performance of the macrocell-tier and maintain a greater signal to interference-plus-noise ratio than the outage level can for about 99% of femtocell users.

Cross-tier interference management schemes in cognitive heterogeneous networks

To satisfy the ever-increasing data rate and service coverage demands, wireless communication networks evolve into heterogeneous networks (HetNets), where low-cost small base stations are embedded in conventional macrocells. Intercell interference emerges as the key capacity-limiting factor in such dense networks, restricting the reusability of spectral resources. Therefore, advanced interference mitigation techniques relying on multi-cell cooperation have attracted significant attention from the wireless industry and academia. This paper discusses interference management schemes for multi-tiered spectrum access in next-generation HetNets. A novel scheme based on full system cognition and base station cooperation is proposed as an enabler for high-capacity HetNets. In addition, practical implementation and operational challenges are investigated.

Evolution toward 5G multi-tier cellular wireless networks: An interference management perspective

The evolving fifth generation (5G) cellular wireless networks are envisioned to overcome the fundamental challenges of existing cellular networks, e.g., higher data rates, excellent end-to-end performance and user-coverage in hot-spots and crowded areas with lower latency, energy consumption and cost per information transfer. To address these challenges, 5G systems need to adopt a multi-tier architecture consisting of macrocells, different types of licensed small cells, relays, and device-to-device (D2D) networks to serve users with different quality-of-service (QoS) requirements in a spectrum and energy-efficient manner. Starting with the visions and requirements of 5G multi-tier networks, this article outlines the challenges of interference management (e.g., power control, cell association) in these networks with shared spectrum access (i.e., when the different network tiers shares the same licensed spectrum). It is argued that the existing interference management schemes will not be able to address the interference management problem in prioritized 5G multi-tier networks where users in different tiers have different priorities for channel access. In this context, a survey and qualitative comparison of the potential existing cell association and power control schemes is provided to demonstrate their limitations for interference management in 5G networks. Open challenges are highlighted and guidelines are provided to modify the existing schemes in order to overcome these limitations and make them suitable for the emerging 5G systems.

Aggregate interference modelling and static resource allocation in closed and open access femtocells

Femtocell has appeared as a solution to increase both the coverage and the capacity of cellular networks. However, interference problem between the macrocell and the femtocell must be solved before any deployment. Since femtocells are deployed by home users in random locations, decentralised interference management schemes remain worth of investigation. In this study, the author deal with the problem of aggregate interference modelling and static resource allocation in orthogonal frequency division multiple access (OFDMA)-based two-tier femtocell networks for both closed and open access femtocells. It is assumed that for macrocell users (MUs), spectrum allocation is accomplished through fractional frequency reuse. The author's objective is to maximise the femtocell user's throughput while maintaining as low as its possible impact on the MUs' performance. Their proposed algorithm is decentralised, and based on some measurements, needs to be performed only when femtocell access point is plugged in. Simulation results show the accuracy of their model and the effectiveness of the proposed scheme compared to the previous methods.

Device-to-device communication in 5G cellular networks: challenges, solutions, and future directions

In a conventional cellular system, devices are not allowed to directly communicate with each other in the licensed cellular bandwidth and all communications take place through the base stations. In this article, we envision a two-tier cellular network that involves a macrocell tier (i.e., BS-to-device communications) and a device tier (i.e., device-to-device communications). Device terminal relaying makes it possible for devices in a network to function as transmission relays for each other and realize a massive ad hoc mesh network. This is obviously a dramatic departure from the conventional cellular architecture and brings unique technical challenges. In such a two-tier cellular system, since the user data is routed through other users? devices, security must be maintained for privacy. To ensure minimal impact on the performance of existing macrocell BSs, the two-tier network needs to be designed with smart interference management strategies and appropriate resource allocation schemes. Furthermore, novel pricing models should be designed to tempt devices to participate in this type of communication. Our article provides an overview of these major challenges in two-tier networks and proposes some pricing schemes for different types of device relaying.

Interference management in LTE‐based HetNets: a practical approach

AbstractInterference is a major obstacle in radio communications, especially when opportunistic frequency reuse is an inherent requirement for maximising spectral efficiency in heterogeneous networks. A typical example is encountered in cellular communications where macrocell‐edge users receive interference from small cell transmissions that use the same radio frequency band. Innovating interference management algorithms are employed towards this end, which because of their interdependencies with numerous parameters of the target operating scenario and various low‐level implementation aspects, need to be prototyped in real‐time signal processing platforms in order to be credibly verified. In this paper, we present the development and experimental validation of a macrocell/femtocell coexistence scenario in close to real‐life conditions. The inclusion of an agile interference management scheme increased the signal processing complexity at the physical layer. This overhead was appropriately addressed by engaging advanced parallel processing techniques, optimisations of the arithmetic operations and intelligent reuse of logic and memory resources in the field programmable gate array (FPGA)‐based baseband processing architecture. Copyright © 2014 John Wiley & Sons, Ltd.

Clustering and Resource Allocation for Dense Femtocells in a Two-Tier Cellular OFDMA Network

Small cells such as femtocells overlaying the macrocells can enhance the coverage and capacity of cellular wireless networks and increase the spectrum efficiency by reusing the frequency spectrum assigned to the macrocells in a universal frequency reuse fashion. However, management of both the cross-tier and co-tier interferences is one of the most critical issues for such a two-tier cellular network. Centralized solutions for interference management in a two-tier cellular network with orthogonal frequency-division multiple access (OFDMA), which yield optimal/near-optimal performance, are impractical due to the computational complexity. Distributed solutions, on the other hand, lack the superiority of centralized schemes. In this paper, we propose a semi-distributed (hierarchical) interference management scheme based on joint clustering and resource allocation for femtocells. The problem is formulated as a mixed integer non-linear program (MINLP). The solution is obtained by dividing the problem into two sub-problems, where the related tasks are shared between the femto gateway (FGW) and femtocells. The FGW is responsible for clustering, where correlation clustering is used as a method for femtocell grouping. In this context, a low-complexity approach for solving the clustering problem is used based on semi-definite programming (SDP). In addition, an algorithm is proposed to reduce the search range for the best cluster configuration. For a given cluster configuration, within each cluster, one femto access point (FAP) is elected as a cluster head (CH) that is responsible for resource allocation among the femtocells in that cluster. The CH performs sub-channel and power allocation in two steps iteratively, where a low-complexity heuristic is proposed for the sub-channel allocation phase. Numerical results show the performance gains due to clustering in comparison to other related schemes. Also, the proposed correlation clustering scheme offers performance, which is close to that of the optimal clustering, with a lower complexity.

Frequency resource allocation strategy with QoS support in hybrid cellular and Device‐to‐Device networks

SummaryHybrid networks, comprising a conventional cellular network overlaid with Device‐to‐Device (D2D), offer efficient way to improve system throughput. In this paper, a novel orthogonal frequency‐division multiple access channel‐assignment method is proposed for hybrid network. The proposed approach is optimal in terms of throughput and is subjected to a sensible QoS requirement, which guarantees that macrocell and D2D achieve a prescribed data rate and outage probability, respectively. Our solution consists of two phases. In the first phase, the minimum sub‐channels are allocated to the macrocell to satisfy their data rate requirements. This problem is mapped to the 0‐1 Knapsack Problem and solved by integer programming based Lagrange dual approach. In the second phase, the redundant sub‐channels are allocated to D2D pairs to maximize the throughput of D2D networks. An interference management scheme is proposed to guarantee the outage probability of D2D communications. A cluster is taken as the unit for frequency reuse among D2D pairs. The problem of clustering is mapped to the MAX k‐CUT problem in graph theory and is solved by graph‐based heuristic algorithm. Extensive simulations demonstrate the superior performance of the proposed solution compared with the existing scheme. Copyright © 2014 John Wiley & Sons, Ltd.

Regionalized Interference Alignment in Two-Tiered Cognitive Heterogeneous Networks

Interference alignment in cognitive networks is an efficient way to achieve the cognitive system throughput gain without degrading the throughout of the primary system. In this paper a novel interference management strategy is presented to use interference alignment in cognitive heterogeneous networks flexibly. Characteristics of interference distribution in two- tiered networks are considered to divide the cell deployed by this structure into two regions. Cognitive radio system determines which region the primary users locate in based on channel state information, and suppresses interference by designing their precoders to achieve interference alignment, hence is termed regionalized interference alignment. Thereby, it can manage interference in different situations effectively. Numerical results are given for the uplink average rates of primary user and second users, which shows that regionalized interference alignment ensures the performance of the cognitive heterogeneous networks.

인지 라디오 시스템에서의 능동적인 간섭 관리 기법

인지 라디오 시스템은 1차 시스템이 사용 중인 주파수를 공유함으로써 지역 당 주파수 이용효율을 향상시킬 수 있는 중요한 기술로 인식되고 있다. 본 논문에서는 2차 시스템이 1차 시스템에 간섭을 미치지 않으며 주파수를 공유할 수 있는 보다 능동적인 간섭 관리 기법을 제안한다. 제안된 프로토콜을 통해 2차 사용자는 1차 시스템의 간섭 채널 정보 및 송 수신 필터 정보를 획득하고 이를 이용하여 프리코딩 행렬을 계산한다. 이때 2차 시스템으로부터의 간섭은 1차 시스템의 사용되지 않는 부채널로 모이기 때문에 1차 시스템은 추가적인 연산 없이 자동적으로 간섭을 제거한다. 그리고 2차 시스템은 백색화 정합 필터를 통해 1차 시스템으로부터의 간섭을 제거함으로써 스펙트럼 효율을 향상시킨다. 전산모의실험을 통해 제안된 기법이 1차 시스템에 간섭을 미치지 않는 동시에 2차 시스템의 성능을 향상시키고, 2차 시스템의 수가 증가하더라도 1차 시스템의 성능이 저하되지 않음을 보였다. Cognitive radio systems have been considered as a strong solution of frequency scarcity due to the limit of frequency resources. This paper proposed an active interference management scheme that the secondary system can coexist with the primary system in the same frequency band without interference. Using the proposed protocol, the secondary user acquires interference channel information and transmit/receive filter information and designs precoding matrix using these information. Since interference from the secondary systems are collected to unused subchannels of the primary system, the primary system can suppress interference without additional process. The secondary systems suppress interference from the primary system using whitening matched filter so that the spectral efficiency can be improved. Numerical results provides that the proposed scheme improves performance of the secondary systems without interference to the primary system and do not degrade performance of the primary system even if the number of the secondary systems increases.