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In fog-aided cellular systems, content delivery latency can be minimized by jointly optimizing edge caching and transmission strategies. In order to account for the cache capacity limitations at the edge nodes (ENs), transmission generally involves both fronthaul transfer from a cloud processor with access to the content library to the ENs and wireless delivery from the ENs to the users. In this paper, the resulting problem is studied from an information-theoretic viewpoint by making the following practically relevant assumptions: 1) the ENs have multiple antennas; 2) only uncoded fractional caching is allowed; 3) the fronthaul links are used to send fractions of contents; and 4) the ENs are constrained to use one-shot linear zero-forcing precoding on the wireless channel. Assuming off-line proactive caching and focusing on a high signal-to-noise ratio (SNR) latency metric, the optimal information-theoretic performance is investigated under both serial and pipelined fronthaul-edge transmission modes. The analysis characterizes the minimum high-SNR latency in terms of normalized delivery time (NDT) for worst case users’ demands. The characterization is exact for a subset of system parameters and is generally optimal within a multiplicative factor of 3/2 for the serial case and 2 for the pipelined case. The results bring insights into the optimal interplay between edge and cloud processing in fog-aided wireless networks as a function of system resources, including the number of antennas at the ENs, the ENs’ cache capacity, and the fronthaul capacity. [ABSTRACT FROM AUTHOR]

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The future wireless Fifth Generation (5G) communication network required a higher bandwidth in order to achieve greater data rate. It will be largely characterized by small cell deployments, typically in the range of 200 meters of radius/cell, at most. The implementation of small size networks delivers various advantages such as high data rate and low signal delay. However, it also suffers from various issues such as inter-cell, intra-cell, and inter-user interferences. This paper discusses the issues related to interference management for 5G network from the perspective of Heterogeneous Network and Device-to-Device communication, by using enabling techniques, such as Inter-cell Interference Coordination, Coordinated Multipoint, and Coordinated Scheduling. Furthermore, several pertinent issues have been critically reviewed focusing on their methodologies, advantages and limitations along with the future work. Future directions proposed by the 3rd Generation Partnership Project for interference mitigation has also been outlined. This review will act as a guide for the researchers to comprehend various existing and emerging enabling interference mitigation techniques for further exploration and smooth implementation of 5G wireless network. [ABSTRACT FROM AUTHOR]

We consider a fog radio access network (F-RAN) with multiple transmitters and receivers, where each transmitter is connected to the cloud via a fronthaul link. Each network node has a finite cache, where it fills its cache with portions of the library files in the off-peak hours. In the delivery phase, receivers request each library files according to an arbitrary popularity distribution. The cloud and the transmitters are responsible for satisfying the requests. This paper aims to design content placement and coded delivery schemes for minimizing both the expected normalized delivery time (NDT) and the peak NDT which measures the transmission latency. We propose achievable transmission policies, and derive an information-theoretic bound on the expected NDT under uniform popularity distribution. The analytical results show that the proposed scheme is within a gap of 2.58 from the derived bound for both the expected NDT under uniform popularity distribution and the peak NDT. Next, we investigate the expected NDT under an arbitrary popularity distribution for an F-RAN with transmitter-side caches only. The achievable and information-theoretic bounds on the expected NDT are derived, where we analytically prove that our proposed scheme is optimal within a gap of two independent of the popularity distribution. [ABSTRACT FROM AUTHOR]

Improvement of spectrum efficiency is a valuable research topic in mobile communication system, which impact cell edge user experience especially. According to current research results, three methods to improve inter-cell spectrum efficiency base on inter-cell interference management, including inter-cell interference randomization, inter-cell interference cancellation and inter-cell interference co-ordination. In this paper, one combinatorial method based on uplink power control and SINR prediction with non-ideal MU-MIMO CSI feedback is proposed for optimal management of inter-cell interference co-ordination. The simulation results show that this method performs very well in complex inter-cell interference scenario, and the average spectrum efficiency is improved more than 50%. [ABSTRACT FROM AUTHOR]

This paper proposes low-complexity measures to be deployed on most aircraft to enable the management of Global Navigation Satellite Systems (GNSS) interference, and in particularly of jamming and spoofing threats, in order to reach the Flightpath2050 safety and security targets. It is known that, if there is a jamming interference and GNSS navigation is lost, a disruption will be caused, requiring the likely intervention of Air Traffic Control. Also, the presence of a spoofing signal is a serious security threat with a potentially catastrophic impact on the safety of the aircraft and on any other ground infrastructure. Through our jamming and spoofing detection and localization stages, based on minimal additional infrastructure, we will reduce the time required to detect and localize an interfering source and, therefore, the time required to mitigate it and restore the nominal traffic operations. Our solutions will also improve the safety of the Air Traffic Management system. Moreover, the deployment of our solution, with its capability of localizing an interfering device, could be a deterrent to any agent interested in intentionally generating a jamming or spoofing signal, and so will reduce the likelihood of this type of interference events. [ABSTRACT FROM AUTHOR]

Autonomous computing, communication, and collaboration among devices have their importance to transform the digital world. Emerging technology device-to-device (D2D) communication has a great impetus to facilitate peer-to-peer network. Therefore, D2D communication technology is expected to be an essential part of the Internet of Things (IoT). Rapid growth in quality of service demand leads to fundamental changes in the architecture of IoT system. This paper explains the benefits and challenges for intelligent D2D communication that will be required to accomplish the requirements for IoT. Many industries and standardization bodies have shown enormous interest towards the implementation of D2D approach in wireless networks. D2D approach facilitates to work without the essential control of the centralized supervision which makes wireless networks more spectrum and energy efficient with traffic offloading. Inter-networking devices offer various applications towards the development of IoT. Physical constraints of the devices and resource constraints of the networks give rise to several issues which need to be resolved. Here, we review the current status in the advancement of D2D technology subject to resources utilization, routing techniques, and interference management. Moreover, potential future challenges are explored that may be faced by the scientific community. [ABSTRACT FROM AUTHOR]

This paper studies a resource allocation scheme and precoding design to increase the number of quality of service (QoS)-satisfied user equipments (UEs) for multicell multiuser multiple-input-multiple-output downlink systems. The main challenge in such multicell systems is the co-channel interference, including intra-user interference (IUI) and inter-cell interference (ICI). To deal with both IUI and ICI, most conventional schemes aim to maximize the signal to interference plus noise ratio or throughputs through enormous channel state information (CSI) exchange among base stations. In order to avoid such tremendous overhead, this work proposes a novel framework, containing a distributed subcarrier assignment and a block diagonalization (BD) precoding, to cope with both types of interferences based on limited exchanged information of subcarrier-assignment and local CSIs (channel gains). In the subcarrier-assignment process, each sector's base station independently assigns a subset of the served UEs to be served over the subcarrier. The channel gains of a particular subcarrier hold a semi-orthogonal property for that subset. Then, on the basis of limited exchanges of information, a BD-type precoding is presented to completely eliminate all IUI and suppress the major part of the leakage interference to the adjacent sectors by exploiting principal component analysis. The simulation results indicate that the proposed framework can provide more QoS-satisfied UEs than that obtained in a previous work. [ABSTRACT FROM AUTHOR]

In this study, a power management scheme using genetic algorithm optimization method in a heterogeneous LTE network in which there exists femtocells having a low transmission power among macrocells is proposed. The simulation results show that power management for femtocells in the downlink direction plays an important role in reducing the degrading effects of the interference. In the simulations, the results of keeping fixed transmission power of femtocell base stations situation are compared with that of performing optimization case. There is no observable performance loss in the femtocell user's signal-interference and noise ratio due to the power management optimization. On the contrary, almost 50% transmission power decrease of femtocell base station can be provided by means of the proposed power management scheme. [ABSTRACT FROM AUTHOR]

Today’s mobile data traffic is dominated by content-oriented traffic. Caching popular contents at the network edge can alleviate network congestion and reduce content delivery latency. This paper provides a comprehensive and unified study of caching and delivery techniques in wireless radio access networks (RANs) with caches at all edge nodes (ENs) and user equipments (UEs). Three cache-aided RAN architectures are considered: RANs without fronthaul, with dedicated fronthaul, and with wireless fronthaul. It first reviews in a tutorial nature how caching facilitates interference management in these networks by enabling interference cancelation (IC), zero-forcing (ZF), and interference alignment (IA). Then, two new delivery schemes are presented. One is for RANs with dedicated fronthaul, which considers centralized cache placement at the ENs but both centralized and decentralized placement at the UEs. This scheme combines IA, ZF, and IC together with soft-transfer fronthauling. The other is for RANs with wireless fronthaul, which considers decentralized cache placement at all nodes. It leverages the broadcast nature of wireless fronthaul to fetch not only uncached but also cached contents to boost transmission cooperation among the ENs. The numerical results show that both schemes outperform existing results for a wide range of system parameters, thanks to the various caching gains obtained opportunistically. [ABSTRACT FROM AUTHOR]

Small-cell is a key technology for next generation mobile networks to cope with the explosive growth of data traffic. In this paper, our objective is to enhance the sum rate of the small-cell networks. We optimize the uplink transmission subject to guaranteeing the quality of services (QoS) requirement of each user and the maximum transmit power constraint at each node. A new sequential quadratic programming (SQP) based solution is proposed to solve the non-convex optimization problem. Further, a low complexity sub-optimal scheme is also proposed. It is found that under the proposed SQP approach, the sum rate of the system increases with increasing the available transmit power and decreases with increasing the minimum rate requirement. Simulation results show that the proposed SQP approach significantly outperforms the sub-optimal scheme in terms of system sum capacity. [ABSTRACT FROM AUTHOR]

In this study, we establish connections between asymptotic functions and properties of solutions to important problems in wireless networks. We start by introducing a class of self-mappings (called asymptotic mappings) constructed with asymptotic functions, and we show that spectral properties of these mappings explain the behavior of solutions to some max–min utility optimization problems. For example, in a common family of max–min utility power control problems, we prove that the optimal utility as a function of the power available to transmitters is approximately linear in the low power regime. However, as we move away from this regime, there exists a transition point, easily computed from the spectral radius of an asymptotic mapping, from which gains in utility become increasingly marginal. From these results we derive analogous properties of the transmit energy efficiency. In this study, we also generalize and unify existing approaches for feasibility analysis in wireless networks. Feasibility problems often reduce to determining the existence of the fixed point of a standard interference mapping, and we show that the spectral radius of an asymptotic mapping provides a necessary and sufficient condition for the existence of such a fixed point. We further present a result that determines whether the fixed point satisfies a constraint given in terms of a monotone norm. [ABSTRACT FROM AUTHOR]

Femtocell deployment is an important strategy when it comes to improvement of QoS metrics in areas of poor cell coverage like indoors in an LTE environment. This, however, is accompanied by bottlenecks in resource allocation and trade-offs in accuracy for interference management in the heterogeneous two-tier network of macro and femtocell environment. To that end, we propose two schemes using radial division of cells that allocate sub-bands to both femtocell users and macrocell users which in turn, mitigates co-channel interference. Simulation results show that our proposed schemes, commonly named as radial sub-band allocation (RSA-1 and RSA-2) improve performance as measured by signal to interference and noise ratio, sum throughput, outage probability, and channel reuse efficiency while maintaining a balance in computational complexity with existing schemes like F-ALOHA. Further experimentation revealed that the proposed version also works exceedingly well in ultra-dense environments. [ABSTRACT FROM AUTHOR]

The rise in wireless data traffic requires innovative interference management techniques to meet the demand. Transmit cooperation among multiple base stations has been proposed as a solution to this challenge and improve throughput. This paper proposes novel resource allocation algorithms with two different cooperation paradigms, viz. the cooperative beamforming and partial data cooperation. The well-known duality principle, which has been used to solve uplink and downlink optimisation problems in previous literature, is shown to exist for multicell systems with both coordinated beamforming and the novel paradigm termed as partial data cooperation. Using the generalised version of duality, this paper solves relevant resource allocation problems in both cases. The proposed power allocation problems are shown to outperform some of the existing optimisation techniques in terms of throughput while having significant conceptual and theoretical advantage. [ABSTRACT FROM AUTHOR]

We consider the problem of interference management in wireless cellular networks with caches at both base stations and receivers, and we characterize the degrees of freedom (DoFs) per cell to within an additive gap of (1/3) and a multiplicative gap of 2 for all system parameters, under one-shot linear schemes. Our result indicates that the one-shot linear DoF per cell scales linearly with the total amount of cache available in the cell, i.e., the sum of the caches at the central base station and all the receivers within the cell, resembling a similar phenomenon previously observed for the case of fully connected wireless networks. To establish the result, we propose a decentralized and randomized cache placement and a delivery scheme, which, on one hand, utilizes the overlap of contents at the base station caches to zero-force part of their outgoing interference and, on the other hand, uses the receiver cache contents to create coded multicasting opportunities, so that the receivers can eliminate the remaining interference due to undesired packets. We also provide a converse argument, which shows that our achievable one-shot linear DoF per cell is within a constant additive gap of (1/3) and a multiplicative gap of 2 of its optimum. [ABSTRACT FROM AUTHOR]

We consider a mixed numerology spectrum sharing (SS) system where the users have different subcarrier spacing (SCS). Unlike in single numerology SS systems, mixed numerology SS systems suffer from inter-numerology interference (INI). We first derive the interference pattern and find that the variance of interference energy increases due to the difference in SCS. This increase in variance negatively affects decoding performance, since the interference energy is unbalanced between subcarriers. However, previous works on this issue did not take this interference pattern into account for interference management. In order to suppress the increase in variance of the interference energy, we propose a transceiver structure for large SCS users by using simple cyclic shift and frequency shift operations. The proposed transceiver disperses the effect of INI, reducing the variance in the interference energy. From the derived distribution characteristics of the interference energy in closed-form expressions, we show that the proposed transceiver achieves better decoding performance. [ABSTRACT FROM AUTHOR]

The fifth-generation (5G) mobile communication system is expecting to support users with diverse data rate requirements by densely deploying small cells. The users attached with small cells make use of the same frequency band as the existing macro cell users, that causes severe co-channel interference and degrades the performance. To overcome this challenge, we propose a game theoretical framework for the optimal uplink power allocation for small cells, i.e., femtocell deployed underlaid macrocell. In this paper, femtocell users play a non-cooperative game to choose the optimal power to maximize the sum-rate of the system. Furthermore, an iterative quality-of-service (QoS)-aware game theory based power control (QoS-GTPC) scheme is proposed to optimize the femtocell user power taking into account macrocell user QoS requirements. Simulation results verify that the proposed QoS-GTPC scheme significantly improves the sum-rate and reduces outage and interference, as compared with conventional power control scheme. [ABSTRACT FROM AUTHOR]

We consider expected risk minimization in multi-agent systems comprised of distinct subsets of agents operating without a common time scale. Each individual in the network is charged with minimizing the global objective function, which is an average of sum of the statistical average loss function of each agent in the network. Since agents are not assumed to observe data from identical distributions, the hypothesis that all agents seek a common action is violated, and thus the hypothesis upon that consensus constraints are formulated is violated. Thus, we consider nonlinear network proximity constraints, which incentivize nearby nodes to make decisions that are close to one another but do not necessarily coincide. Moreover, agents are not assumed to receive their sequentially arriving observations on a common time index, and thus seek to learn in an asynchronous manner. An asynchronous stochastic variant of the Arrow–Hurwicz saddle point method is proposed to solve this problem that operates by alternating primal stochastic descent steps and Lagrange multiplier updates that penalize the discrepancies between agents. This tool leads to an implementation that allows for each agent to operate asynchronously with local information only and message passing with neighbors. Our main result establishes that the proposed method yields convergence in expectation both in terms of the primal sub-optimality and constraint violation to radii of sizes ${\mathcal O}(\sqrt{T})$ and ${\mathcal O}(T^{3/4})$ , respectively. Empirical evaluation on an asynchronously operating wireless network that manages user channel interference through an adaptive communications pricing mechanism demonstrates that our theoretical results translates well to practice. [ABSTRACT FROM AUTHOR]

Multi-scale spectrum sensing is proposed to overcome the cost of full network state information on the spectrum occupancy of primary users (PUs) in dense multi-cell cognitive networks. Secondary users (SUs) estimate the local spectrum occupancies and aggregate them hierarchically to estimate spectrum occupancy at multiple spatial scales. Thus, SUs obtain fine-grained estimates of spectrum occupancies of nearby cells, more relevant to scheduling tasks, and coarse-grained estimates of those of distant cells. An agglomerative clustering algorithm is proposed to design a cost-effective aggregation tree, matched to the structure of interference, robust to local estimation errors, and delays. Given these multi-scale estimates, the SU traffic is adapted in a decentralized fashion in each cell, to optimize the trade-off among SU cell throughput, interference caused to PUs, and mutual SU interference. Numerical evaluations demonstrate a small degradation in SU cell throughput (up to 15% for a 0 dB interference-to-noise ratio experienced at PUs) compared to a scheme with full network state information, using only one-third of the cost incurred in the exchange of spectrum estimates. The proposed interference-matched design is shown to significantly outperform a random tree design, by providing more relevant information for network control, and a state-of-the-art consensus-based algorithm, which does not leverage the spatio-temporal structure of interference across the network. [ABSTRACT FROM AUTHOR]

Device-to-Device (D2D) communications can provide proximity based services in the future 5G cellular networks. It allows short range communication in a limited area with the advantages of power saving, high data rate and traffic offloading. However, D2D communications may reuse the licensed channels with cellular communications and potentially result in critical interferences to nearby devices. To control the interference and improve network throughput in overlaid D2D cellular networks, a novel channel assignment approach is proposed in this paper. First, we characterize the performance of devices by using Poisson point process model. Then, we convert the throughput maximization problem into an optimal spectrum allocation problem with signal to interference plus noise ratio constraints and solve it, i.e., assigning appropriate fractions of channels to cellular communications and D2D communications. In order to mitigate the interferences between D2D devices, a cluster-based multi-channel assignment algorithm is proposed. The algorithm first cluster D2D communications into clusters to reduce the problem scale. After that, a multi-channel assignment algorithm is proposed to mitigate critical interferences among nearby devices for each D2D cluster individually. The simulation analysis conforms that the proposed algorithm can greatly increase system throughput. [ABSTRACT FROM AUTHOR]

Simultaneous co-channel transmission and reception, denoted as in-band full-duplex (FD) communications, has been promoted as a solution to improve the spectral efficiency in wireless networks. For cellular networks, in addition to the existing aggregate interference in half-duplex transmission, the residual self-interference and cross-mode interference [i.e., between uplink (UL) and downlink (DL)] impose major obstacles for FD communications’ deployment. Although the FD communication’s promising impact on the overall network data rate has been established in the literature, the rate gains are achieved in the DL transmissions at the expense of marginal gain, or even degradation, for the UL transmissions. This paper, therefore, focuses on the analysis of UL ergodic rate in FD cellular networks where a minimum distance between BSs using the same time-frequency resource block is imposed. Hence, the mutually interfering BSs’ locations are modeled by Matérn hard core point process. The distribution of the aggregate interference and the channel-to-interference-plus-noise ratio at the UL of a typical user are characterized using a stochastic geometry analysis. Several UL power control techniques are presented and their resulting ergodic rates are derived and compared. The simulation results suggest that the UL performance highly depends on the network parameters and the UL power control techniques. [ABSTRACT FROM AUTHOR]

In full-duplex cloud radio access network systems, the uplink received signal of each remote radio head (RRH) contains downlink-to-uplink (D2U) interference signal which is a linear combination of the transmit signals of nearby RRHs including itself. Since the fronthaul links that connect RRHs to a baseband processing unit (BBU) have finite capacity, the RRHs forward quantized versions of the uplink received signals to the BBU. To improve the fidelity of the quantization, it is important to suppress the impact of the D2U interference signals prior to the quantization. This paper tackles the problem of jointly optimizing the D2U interference suppression and fronthaul quantization strategies with the goal of maximizing the sum rate of uplink user equipments. To tackle the formulated non-convex problem, we derive an iterative algorithm based on the successive convex approximation approach. To save the complexity, a simpler algorithm, which non-iteratively pre-fixes the D2U interference suppression matrices, is also proposed. Extensive numerical results confirm the advantages of the proposed schemes compared to conventional schemes. [ABSTRACT FROM AUTHOR]

This paper considers an analytical approach to evaluate the outage behavior of the device-to-device (D2D) communication, which is underlaid with cellular networks, as an enabling technology for Internet-of-Things (IoTs). In such an architecture, a group of IoT devices (IoTDs) communicate with an IoT gateway by reusing the resources of cellular users (CUEs) to enhance the spectral efficiency of the fifth-generation networks. Two interference management schemes are widely used in the literature for the sharing of D2D spectrum, namely the fixed-power margin (FPM) and the cooperative pairing (CooP) schemes. We investigate and compare the performance of the two schemes from the perspective of outage probability (OP). While satisfying the minimal performance of the system, the OP of an arbitrary pair (i.e., one IoTD and one CUE) under both schemes are derived in closed form in terms of hyper-geometric functions via the Mellin transform technique. Moreover, for the CooP scheme, an iterative alternating Dinkelbach algorithm is proposed as an outage-optimal power allocation scheme. Analytical and simulation results reveal that the CooP scheme is the outage optimum for the high SNR regime while the FPM scheme is the optimal one for the low SNR regime. Simulation results also show that the suitable power margin of the FPM scheme lies in between 2 and 3 dB. Under these two interference management schemes, the accuracy of the analytical results is verified through numerical simulation and it turns out that these are well matched. [ABSTRACT FROM AUTHOR]

Abstract Heterogeneous network (HetNet) is recognized as a promising technique to provide blanket wireless coverage and high throughput in 5G wireless networks. With the heterogeneous characteristics, HetNet achieves higher capacity, wider coverage and better performance in energy efficiency and spectrum efficiency. However, HetNet also brings complex interference management in the network. In this paper, we present a security analysis for a proposed interference management mechanism in a two-tier heterogeneous network (HetNet) system. The proposed interference management mechanism aims to maximize the secrecy rate of a cellular user under eavesdropping attack. The HetNet system model includes a macro base station, several small base stations, several users, and one eavesdropper. To further improve the performance of the network, massive multiple-input multiple-output technology is applied to base stations. A single antenna is applied to users and the eavesdropper. Device-to-device (D2D) communications are considered in the HetNet system model for introducing interference in the macro cell to the eavesdropper. The proposed interference management mechanism takes consideration of three factors as transmit beamforming, spectrum reuse and D2D communications. Not only the secrecy rate of the user under eavesdropping attack but also the communication quality of services of SBSs users are considered in the security analysis. An optimization problem is formulated for the secrecy rate maximization of the user under eavesdropping attack with the constraints of quality of services of users associated with base stations and power limitation of base stations. The security analysis and numerical results show that our proposed interference management mechanism for physical layer security can utilize the interference in the network to improve the secrecy rate of the cellular user under eavesdropping attack. [ABSTRACT FROM AUTHOR]

Wireless Fidelity (Wi-Fi) has been introduced in Third Group Partnership Project (3GPP) Release 12 as an alternative solution for offloading high traffic in LTE network. In addition, Wi-Fi has many advantages such as low operation cost, easy-installed systems and it is currently widely implemented in houses and offices. However, a phenomenon called co-channel interference may occur within LTE-Wi-Fi networks because of its low power transmission when compared to the macrocell. Hence, Wi-Fi users may suffer worst network degradation at frequency 2.4GHz due to its collision with LTE band 40. In order to solve this network issue, an interference management is needed as it affects users perceive experiences and services when using LTE-Wi-Fi integrated networks. In this paper, a method known as Pulse-Shaping Algorithm (PSA) has been integrated with Direct Sequence Spread Spectrum (DSSS) which is called Enhanced Direct Sequence Spread Spectrum (EDSSS) to model Signal-to-Interference-Noise Ratio (SINR). The introduction of this method is for reducing the occurrence of co-channel interference. Furthermore, a new coefficient named as a radius fraction (β) has been introduced in order to evaluate the SINR expression for User Equipments (UEs) in LTE-Wi-Fi networks. The simulation results discovered that β-coefficient with value of 0.2 has given the most optimum improvement of SINR for LTE and Wi-Fi users. By modifying the SINR expression with PSA method, the network performances for users have improved significantly. [ABSTRACT FROM AUTHOR]

In multi-user wireless packet networks, interference, typically modeled as packet collision, is the throughput bottleneck. Users become aware of the interference pattern via feedback and use this information for contention resolution and packet retransmission. Conventional random access protocols interrupt communication to resolve contention, which reduces network throughput and increases latency and power consumption. In this paper, we take a different approach, and we develop opportunistic random access protocols rather than pursuing conventional methods. We allow wireless nodes to communicate without interruption and to observe the interference pattern. We then use this interference pattern knowledge and channel statistics to counter the negative impact of interference. We prove the optimality of our protocols using an extremal rank-ratio inequality. An important part of our contributions is the integration of spatial correlation in our assumptions and results. We identify spatial correlation regimes in which inherently outdated feedback becomes as good as idealized instantaneous feedback and correlation regimes in which feedback does not provide any throughput gain. To better illustrate the results, and as an intermediate step, we characterize the capacity region of finite-field spatially correlated interference channels with delayed channel state information at the transmitters. [ABSTRACT FROM AUTHOR]

A novel blind interference alignment (IA) scheme in conjunction with interference decoding by virtue of integer forcing is proposed for downlink cellular networks without channel state information at the base station. In the proposed scheme, inter-user interference at each mobile user is aligned in blind manner, and by employing the same lattice code for all users, each user directly decodes integer-linear combinations of interfering codewords from the aligned interference signals in contrast to the previous works that simply null out the aligned interference by zero forcing. Numerical simulations demonstrate that the proposed scheme significantly improves the sum rate compared with the previous blind IA schemes. [ABSTRACT FROM AUTHOR]

In order to troubleshoot the problem that the initial scheduling program needs to be altered due to the disruption incidents in the production process, a disruption management model that allows for the perturbation perception of the three behavioral subjects, i.e. customers, business managers and workshop workers, is proposed herein. Based on the prospect theory, it is considered that the behavior subject benefits from the interference with scheduling process. A dissatisfaction measurement approach is proposed for behavioral subjects. A lexicographical order multi-objective programming method is also developed to better address the multi-objective shop scheduling problem based on the disruption management. A quantum genetic algorithm with rotation angle adaptive adjustment as designed herein inherits the randomness and stability tendency of the cloud model to adaptively adjust the rotation angle so that the optimization capacity of the algorithm can be improved. Quantum crossover and mutation are used to improve population diversity and avoid premature convergence. Numerical test shows that the algorithm has a good performance. [ABSTRACT FROM AUTHOR]

The mm-wave spectra at 71–76 GHz (70 GHz) and 81–86 GHz (80 GHz) have the potential to endow fifth-generation new radio (5G-NR) with mobile connectivity at gigabit rates. However, a pressing issue is the presence of incumbent systems in these bands, which are primarily point-to-point fixed stations (FSs). In this paper, we first identify the key properties of incumbents by parsing databases of existing stations in major cities to devise several modeling guidelines and characterize their deployment geometry and antenna specifications. Second, we develop a detailed uplink interference framework to compute the aggregate interference from outdoor 5G-NR users into FSs. We then present several case studies in densely populated areas, using actual incumbent databases and building layouts. Our simulation results demonstrate promising 5G coexistence at 70 and 80 GHz as the majority of FSs experience interference well below the noise floor, thanks to the propagation losses in these bands and the deployment geometry of the incumbent and 5G systems. For the few FSs that may incur higher interference, we propose several passive interference mitigation techniques such as angular-based exclusion zones and spatial power control. The simulation results show that the techniques can effectively protect FSs, without tangible degradation of the 5G coverage. [ABSTRACT FROM AUTHOR]

Deploying femtocells underlaying macrocells is a promising way to improve the capacity and enhance the coverage of a cellular system. However, densely deployed femtocells in urban area also give rise to intra-tier interference and cross-tier issue that should be addressed properly in order to acquire the expected performance gain. In this paper, we propose an interference management scheme based on joint clustering and resource allocation for two-tier Orthogonal Frequency Division Multiplexing (OFDM)-based femtocell networks. We formulate an optimization task with the objective of maximizing the sum throughput of the femtocell users (FUs) under the consideration of intra-tier interference mitigation, while controlling the interference to the macrocell user (MU) under its bearable threshold. The formulation problem is addressed by a two-stage procedure: femtocells clustering and resource allocation. First, disjoint femtocell clusters with dynamic sizes and numbers are generated to minimize intra-tier interference. Then each cluster is taken as a resource allocation unit to share all subchannels, followed by a fast algorithm to distribute power among these subchannels. Simulation results show that our proposed schemes can improve the throughput of the FUs with acceptable complexity.

As one of the key technologies in 5G networks，ultra-dense wireless network is utilized to approach the future 1 000 ultra-high traffic volume.Nevertheless，the dense deployment of network nodes would result in severe interference，and thus interference management was proposed as the big principle behind 5G ultra-dense wireless networks research.Firstly，the interference management schemes were classifed from two aspects：avoidance and utilization.Then，an intelligent interference management architecture was proposed to accommodate the development trend of future wireless networks in terms of intelligence and heterogeneity in order to realize the dynamic tightly coupled interference management of wireless network environment and interference management.Taking the intrinsic relationship between interference management and resource management into consideration，three cutting-edge interference management schemes were introduced，which could significantly improve the network resource utilization and the network capacity.

Interference management is one of the most critical issues in underlaying device-to-device (D2D) communication due to the coexistence of D2D pairs and cellular users that operate under the same spectrum. In this paper, we provide the interference management algorithm to maximize the performance of the D2D communication while satisfying the quality-of-service requirements of the cellular communications in both uplink and downlink phases. The proposed algorithm includes: 1) the admission control and power allocation to ensure that the interference from D2D communication does not affect to the cellular communications and 2) the shared channel assignment to maximize the total throughput of the D2D communication. We prove that our proposed algorithm can achieve at least half of the performance of optimal algorithm. The simulation results validate the feasibility, convergence, and optimality of our algorithm: it cannot only closely approximate the optimal throughput of D2D communication but also outperform existing algorithms.

Wireless Sensor Networks are constrained by low channel utilization and limited battery capacity, so they are widely regarded as the mainly performance bottlenecks. In this paper, in order to improve channel utilization and prolong network lifetime, we investigate the cooperation of multi-hop Wireless Rechargeable Sensor Networks (WRSNs) with Successive Interference Cancellation (SIC) technology. In WRSNs, since the flow rate of each node is unknown, the power of the nodes is not constant. However, SIC will not work if the signal power levels at receive node cannot be sorted. To solve this issue, we first construct a minimum energy routing and unify the transmit rate to determine the transmit power. We can also obtain the time scheduling scheme after determining the routing and power. Next, we formulate an optimization problem, with the objective of maximizing the mobile charger’s vacation time over the rechargeable cycle. Finally, we provide a near-optimal solution and prove its feasible performance. Simulation results present that SIC can achieve the better upper boundary on throughput (compared to inference avoidance increasing about 180−450%) and no extra transmit and receive energy consumption in the multi-hop WRSNs.

There are many scenarios that have been proposed for fifth generation (5G) networks. Some of them, if implemented, will bring fundamental changes at the architectural and node level. One example of such proposed technologies is device-to-device (D2D) communications which will change the nature of conventional cellular network design. D2D permits direct communication between two or more user devices without intervention of the base station (i.e. eNB). D2D can ensure network performance improvement over the traditional cellular network, because it can offload the mobile data traffic from the other devices. However, applying D2D features in a cellular network will bring about more complex interference problems, since D2D communication uses the same band as its underlying cellular communication network. The aim of this research is to investigate interference-related problems caused by D2D communications, affecting the underlying cellular networks, during downlink and uplink transmissions. The paper examines the use of power control methods to mitigate interference. A comparison is offered between fixed power level (FC) with or without power control, and adaptive power controls using two methods (AC1 and AC2), on a base station or on each of the D2D devices, based on the measured signal to interference plus noise ratio (SINR). The simulation results show that both power control methods contribute to improvement of network performance. AC1 and AC2 can improve SINR by about 1 dB and 0.5 dB compared to FC in a downlink transmission, and by 0.5 dB in an uplink transmission.

We consider a wireless network strategy based on successive interference cancellation (SIC) for mine locomotives. We firstly build the original mathematical model for the strategy which is a non-convex model. Then, we examine this model intensively, and figure out that there are certain regulations embedded in it. Based on these findings, we are able to reformulate the model into a new form and design a simple algorithm which can assign each locomotive with a proper transmitting scheme during the whole schedule procedure. Simulation results show that the outcomes obtained through this algorithm are improved by around 50% compared with those that do not apply the SIC technique.

We study a distributed channel allocation problem of non-cooperative OFDMA femtocells in two-tiered macro-femto networks. The objective is to maximize the total capacity of uplink macro users and femto users. We assume a time-slotted system, a time-invariant channel model (no fading), each user knows the signal-to-interference-plus-noise ratio (SINR) of all channels, and the channel selection happens only at the beginning of each time-slot. We study the performance of a best-response strategy where each user chooses to transmit in the highest-SINR channel. For simplicity, we focus on the homogeneous 3-link, 2-channel case and show that if all users update their actions every time-slot (i.e., all users make simultaneous moves), an oscillation can occur and result in the worst performance. To avoid the oscillation and achieve the highest total capacity, while still assuming no coordination among the users, we propose a stochastic best-response algorithm, where each user updates its channel selection with a selection probability p. We use a Markov chain to analyze the average capacity performance and use simulation results to confirm our analysis and also provide performance of other homogeneous cases with more number of links and channels. It is shown that the highest total capacity can be achieved when the selection probability p is very small. This stochastic best response with small p in effect provides a sequential move mechanism which requires no coordination.

We consider the base station placement problem for wireless sensor networks with successive interference cancellation (SIC) to improve throughput. We build a mathematical model for SIC. Although this model cannot be solved directly, it enables us to identify a necessary condition for SIC on distances from sensor nodes to the base station. Based on this relationship, we propose to divide the feasible region of the base station into small pieces and choose a point within each piece for base station placement. The point with the largest throughput is identified as the solution. The complexity of this algorithm is polynomial. Simulation results show that this algorithm can achieve about 25% improvement compared with the case that the base station is placed at the center of the network coverage area when using SIC.

Abstract Device-to-device (D2D) communications in cellular networks enable user equipments (UEs) to directly communicate with each other without the relay of base stations (BSs). They can improve network performance, while they also complicate interference management (IM). In this paper, the IM issue is studied for the D2D communications underlaying heterogeneous networks consisting of macro and small cells. Investigation is first made into D2D performance for UEs in different communication modes (D2D mode and device-to-cell modes). Then, a D2D feasible set is defined and derived which gives a region to allow D2D links to share network resource; and a feasible set scheme is proposed to manage the interference among communication links in order for the cellular links and D2D links to satisfy quality of service (QoS) requirements. After this, the optimal deployment of small cells is studied and an optimal deployment scheme is found that maximizes the transmission density while the QoS of links in different communication modes can be guaranteed. The analytical results are obtained and the calculations show that the proposed interference management schemes can effectively mitigate interference among cellular links and D2D links; and all the links (macro cell link, small cell link and D2D link) can satisfy the QoS requirement when they are sharing the resources. Compared to the neighbor based scheme, the proposed scheme can reduce the average outage probability up to 92%. In addition, the proposed deployment scheme can maximize the transmission capacity with guaranteed link QoSs. [ABSTRACT FROM AUTHOR]

To disperse traffic explosion in hotspot areas, the operators have been overlaying their formerly deployed legacy networks with small cells in a denser manner. In this letter, a location-aware self-optimization scheme is proposed, which improves per-user throughput by adjusting downlink transmission power offset based on the effective provision of positioning. The simulation results confirm that, without relying on discovery signals, the proposed scheme provides higher average SINR per user equipment than the small cell on/off control scheme with the discovery signal in 3GPP-LTE Standards, and the localized capacity is also improved. [ABSTRACT FROM AUTHOR]