Inter-cell Interference Mitigation Research Articles

Inter-Cell Interference Mitigation for Cellular-Connected UAVs Using MOSDS-DQN

Inter-Cell Interference Mitigation for Cellular-Connected UAVs Using MOSDS-DQN

Heterogeneous Drone Small Cells: Optimal 3D Placement for Downlink Power Efficiency and Rate Satisfaction

In this paper, we delve into the domain of heterogeneous drone-enabled aerial base stations, each equipped with varying transmit powers, serving as downlink wireless providers for ground users. A central challenge lies in strategically selecting and deploying a subset from the available drone base stations (DBSs) to meet the downlink data rate requirements while minimizing the overall power consumption. To tackle this, we formulate an optimization problem to identify the optimal subset of DBSs, ensuring wireless coverage with an acceptable transmission rate in the downlink path. Moreover, we determine their 3D positions for power consumption optimization. Assuming DBSs operate within the same frequency band, we introduce an innovative, computationally efficient beamforming method to mitigate intercell interference in the downlink. We propose a Kalai–Smorodinsky bargaining solution to establish the optimal beamforming strategy, compensating for interference-related impairments. Our simulation results underscore the efficacy of our solution and offer valuable insights into the performance intricacies of heterogeneous drone-based small-cell networks.

Mitigation of Inter-Cell Interference by using MIMO System in Visible Light Communication System

In this paper, the multiple input and multiple output system (MIMO) is investigated to mitigate the inter-cell interference (ICI) in visible light communication (VLC). The interference due to light from neighbor cell deteriorates the channel capacity of the system. Therefore, a MIMO-based VLC system is employed to optimize the capacity especially in ICI areas of the room. In this paper, the capacity of [Formula: see text], [Formula: see text] and [Formula: see text] MIMO systems is investigated and compared with the single input and single output (SISO) channel capacity without interference. The channel capacity improves by increasing the order of MIMO array and it deteriorates due to ICI. However, the effects of ICI are more severe at higher signal-to-noise ratio (SNR) especially at high interference areas. Therefore, the order of MIMO array is investigated at different SNRs in interference regions to achieve the interference-free capacity system. Simulation and theoretical results show that ICI is considerably mitigated by using MIMO system. The high SNR 42, 47 and 51.7 dB is achieved in ICI for [Formula: see text], [Formula: see text] and [Formula: see text] MIMO system, respectively.

SOFT FREQUENCY REUSE FOR MILIGATION OF INTERCELLULER INTEREFERENCE

Background. The appearance of femtocells in LTE networks has provided indoor coverage and overcome large data flows for operators. However, strong interference occurs in neighbouring femtocell users due to the limited available spectrum in cellular networks that transmit data in the same radio range. In densely deployed environments, interference issues in single-channel femtocells cause significant performance degradation. In this study, we mitigate inter-cell interference in femtocell networks by combining femtocells as a result of common interference and soft frequency reuse in downlink and uplink by moving and exchanging interfering physical blocks.
 Objective. The purpose of the paper is to improve the efficiency of ensuring the quality of services in wireless networks by reducing any interference due to the distribution of traffic, which is able to provide uninterrupted connection to the user.
 Methods. Enabling conditions for inter-cell interference mitigation in LTE-based femtocell networks with soft frequency reuse.
 Results. Interference is a key issue in the deployment of LTE femtocells. Closely located femtocells interfere with each other if they transmit on the same frequency. Therefore, crossing femtocells and enabling them to allocate resources and reuse soft frequencies effectively reduces interference and prevents the loss of network resources. The scheme is triggered whenever the user's femto equipment experiences strong interference from neighbouring femtocells. By assigning a separate set of physical resource blocks to users at the edge of the cell, our scheme significantly reduces interference, which automatically increases cell throughput. The simulation results show the advantages of applying our scheme, in particular, the interference of the user's femto-equipment is reduced by 14% and the throughput is improved by 25%. That is, we observe a significant improvement in the performance of femtocells.
 Conclusions. A femtocell crossing scheme with soft frequency reuse is presented to reduce interference between femtocells of LTE networks, which allows effectively ensuring the quality of service transmission in wireless networks by reducing interference and increasing performance through traffic distribution.

QoE-Driven Distributed Resource Optimization for Mixed Reality in Dynamic TDD Systems

With the full development of intelligent mobile communications, wireless mixed reality (MR) provides a more visually immersive experience and stronger interaction with environments than virtual reality (VR) and augmented reality (AR). However, the asymmetric characteristic of wireless MR traffic creates a huge challenge to current mobile networks. Dynamic time division duplex (D-TDD) is considered as a promising technology to improve wireless MR users’ quality of experience (QoE) due to its potentials and advantages in delivering asymmetric traffic. Therefore, in this paper, we propose a QoE-driven distributed multidimensional resource allocation (MRA) supplemented by inter-cell interference (ICI) mitigation scheme for wireless MR in multi-cell D-TDD systems. First, to improve QoE of MR users, we formulate the joint optimization of subframe configuration, channel assignment and computation offloading as a mixed-integer nonlinear programming problem. A novel fully-decentralized multi-agent deep Q-network (DQN) algorithm is developed to solve the problem. Then, to mitigate ICI, a water filling based power control algorithm is investigated to minimize the total power of each small base station and its associated MR users. Simulation results demonstrate that our proposed scheme improves QoE of MR users in a realizable way as compared to existing schemes.

Optimal Frequency Reuse and Power Control in Multi-UAV Wireless Networks: Hierarchical Multi-Agent Reinforcement Learning Perspective

To overcome the problems caused by the limited battery lifetime in multiple-unmanned aerial vehicle (UAV) wireless networks, we propose a hierarchical multi-agent reinforcement learning (RL) framework to maximize the energy efficiency (EE) of UAVs by finding the optimal frequency reuse factor and transmit power. The proposed algorithm consists of distributed inner-loop RL for transmit power control of the UAV terminal (UT) and centralized outer-loop RL for finding the optimal frequency reuse factor. Specifically, the proposed algorithm adjusts these two factors jointly to effectively mitigate intercell interference and reduce undesired transmit power consumption in multi-UAV wireless networks. We show that, for this reason, the proposed algorithm outperforms conventional algorithms, such as a random action algorithm with a fixed frequency reuse factor and a hierarchical multi-agent Q-learning algorithm with binary transmit power controls. Furthermore, even in the environment where UTs are continuously moving based on the mixed mobility model, we show that the proposed algorithm can find the best reward when compared to conventional algorithms.

Hungarian Mechanism based Sectored FFR for Irregular Geometry Multicellular Networks

The growing demands for mobile broadband application services along with the scarcity of the spectrum have triggered the dense utilization of frequency resources in cellular networks. The capacity demands are coped accordingly, however at the detriment of added inter-cell interference (ICI). Fractional Frequency Reuse (FFR) is an effective ICI mitigation approach when adopted in realistic irregular geometry cellular networks. However, in the literature optimized spectrum resources for the individual users are not considered. In this paper Hungarian Mechanism based Sectored Fractional Frequency Reuse (HMS-FFR) scheme is proposed, where the sub-carriers present in the dynamically partitioned spectrum are optimally allocated to each user. Simulation results revealed that the proposed HMS-FFR scheme enhances the system performance in terms of achievable throughput, average sum rate, and achievable throughput with respect to load while considering full traffic.

Resource Allocation in NOMA-Based Self-Organizing Networks Using Stochastic Multi-Armed Bandits

To achieve better connectivity in future communication networks, the deployment of different types of access points (APs) is underway. APs are expected to be equipped with self-organizing capabilities to reduce costs. Moreover, due to the spectrum crunch, frequency reuse among the deployed APs is inevitable, exacerbating the problem of inter-cell interference (ICI). Therefore, ICI mitigation in self-organizing networks (SONs) is commonly identified as a key radio resource management mechanism to enhance performance. To this end, this paper proposes a novel solution for the uncoordinated channel and power allocation problems. Based on the multi-armed bandits (MAB) framework, the proposed technique does not require any communication between the APs. The case of varying channel rewards across APs is considered. In contrast to previous work on channel allocation using the MAB framework, APs are permitted to choose multiple channels for transmission. Moreover, non-orthogonal multiple access is used, allowing multiple APs to access each channel simultaneously. This results in an MAB model with varying channel rewards, multiple plays and non-zero reward on collision. The proposed algorithm has an expected regret in the order of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</i> (log <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> T), with extensive numerical results revealing it significantly outperforms a well-known baseline algorithm in terms of energy efficiency.

A dynamic Q-learning beamforming method for inter-cell interference mitigation in 5G massive MIMO networks

Beamforming is an essential technology in 5G Massive Multiple-Input Multiple-Output (MMIMO) communications, which are subject to many impairments due to the nature of wireless transmission channel. The Inter-Cell Interference (ICI) is one of the main obstacles faced by 5G communications due to frequency-reuse technologies. However, finding the optimal beamforming parameter to minimize the ICI requires infeasible prior network or channel information. In this paper, we propose a dynamic Q-learning beamforming method for ICI mitigation in the 5G downlink that does not require prior network or channel knowledge. Compared with a traditional beamforming method and other industrial Reinforcement Learning (RL) methods, the proposed method has lower computational complexity and better convergence efficiency. Performance analysis shows the quality of service improvement in terms of Signal-to-Interference-plus-Noise-Ratio (SINR) and the robustness towards different environments.

Inter-cell interference mitigation using adaptive reduced power subframes in heterogeneous networks

With the remarkable impact and fast growth of the mobile networks, the mobile base stations have been increased too, especially in the high population areas. These base stations will be overloaded by users, for that reason the small cells (like pico cells) were introduced. However, the inter-cell interference will be high in this type of Heterogeneous networks. There are many solutions to mitigate this interference like the inter-cell interference coordination (ICIC), and then the further enhanced ICIC (Fe-ICIC) where the almost blank subframes are used to give priority to the (victim users). But it could be a waste of bandwidth due to the unused subframes. For that reason, in this paper, we proposed an adaptive reduced power subframe that reduces its power ratio according to the user’s signal-to-interference-plus-noise ratio (SINR) in order to get a better throughput and to mitigate the intercell interference. When the user is far from the cell, the case will be considered as an edge user and will get a higher priority to be served first. The results show that the throughput of all users in the macro cells and pico cell will be improved when applying the proposed scheme in term of throughput for the users and the cells.

A REVIEW OF INTER CELL INTERFERENCE MANAGEMENT IN REGULAR AND IRREGULAR GEOMETRY CELLULAR NETWORKS

This paper reviews the inter-cell interference (ICI) mitigation approaches in the OFDMA based multicellular networks with more emphasis on the frequency reused based ICI coordination schemes in the downlink systems. The geometry of the network severely affects the Signal to Interference and Noise Ratio (SINR); therefore, the wireless cellular systems are strongly dependent on the spatial BSs configuration and topology of a network. ICI mitigation techniques for both regular and irregular geometry networks are analyzed and a qualitative comparison along with the future research directions are presented.

Performance evaluation of inter-cell interference prediction in massive MIMO

This paper presents inter-cell interference prediction in massive multiple input multiple output. The rapid demand for widespread multimedia services notwithstanding the deployment of 4G in Lagos, Nigeria and the urgent need to upgrade to 5G networks with downlink and uplink data capacities of not less than 300 and 60 Mbps, respectively for at least 95% penetration rate at any instantaneous time; there is a possibility of experiencing crosstalk and adjacent inter-cell interference within the receiving antennas. 5G inter-cell interference prediction scheme that employs LTE performance index using locally sourced data from Huawei Nigeria limited was presented. The performances of the currently deployed LTE network were evaluated by employing performance metrics such as uplink and downlink capacities and recommending a possible inter-cell interference mitigation technique to be implemented in the deployment of 5G network in Lagos. The identified key performance metrics used include over the air emulation, carrier to interference plus noise ratio, peak RLC throughput, coverage probability, and the map-based model. Hence, ICIC static coordination algorithm, which comprise NOICIC, Hard FFR, PFR, SFR and SFFR were analyzed. With static ICIC algorithm, the coverage probability was 78% for receiving more than 20 kbps, with cell-edge users using resources of centre-users and with edge-users of neighbouring cells using different resource block; therefore reducing interference and consequently increasing throughput when there is static ICIC coordination. Implementing the static ICIC schemes on the 5G network when deployed in Lagos will improve the average downlink throughput over what is currently attainable with the 4G network in use at the moment

Walsh–Hadamard Transform Based Non-Orthogonal Multiple Access (NOMA) and Interference Rejection Combining in Next-Generation HetNets

In heterogeneous networks (HetNets), non-orthogonal multiple access (NOMA) has recently been proposed for hybrid-access small-cells, promising a manifold network capacity compared to OMA. One of the major issues with the installation of a hybrid-access mechanism in small-cells is the cross-tier interference (intercell interference (ICI)) caused by the macrocell users (MUs) that are unable to establish a connection to the small-cell base station (SBS). In this paper, a joint strategy is proposed for hybrid-access small-cells using the Walsh–Hadamard transform (WHT) with NOMA and interference rejection combining (IRC) to achieve high performance gains and mitigate intercell interference (ICI), respectively. WHT is applied mathematically as an orthogonal variable spreading factor (OVSF) to achieve diversity in communication systems. When applied jointly with NOMA, it ensures better performance gains than the conventional NOMA. It reduces the bit error rate (BER) and enhances subsequent throughput performance of the system. IRC is used at the receiver side for managing the cross-tier interference caused by MUs that are unable to connect to the small-cell base station (SBS) for hybrid-access. The work considers both ideal and nonideal successive interference cancellation (SIC) conditions for NOMA. Mathematical modeling is provided for the proposed joint strategy for HetNets and the results validate it in terms of BER and subsequent user throughput performance, compared to the conventional NOMA approach.

Synchronization of Variable-Length Constrained Sequence Codes

We study the ability of recently developed variable-length constrained sequence codes to determine codeword boundaries in the received sequence upon initial receipt of the sequence and if errors in the received sequence cause synchronization to be lost. We first investigate construction of these codes based on the finite state machine description of a given constraint, and develop new construction criteria to achieve high synchronization probabilities. Given these criteria, we propose a guided partial extension algorithm to construct variable-length constrained sequence codes with high synchronization probabilities. With this algorithm we construct new codes and determine the number of codewords and coded bits that are needed to recover synchronization once synchronization is lost. We consider a large variety of constraints including the runlength limited (RLL) constraint, the DC-free constraint, the Pearson constraint and constraints for inter-cell interference mitigation in flash memories. Simulation results show that the codes we construct exhibit excellent synchronization properties, often resynchronizing within a few bits.

Energy-Efficient ICI Mitigation with Dynamic and Location-Based Power Allocation in Mobility-Based 5G HetCN

This paper proposes a power allocation mechanism for the HetCNs which is both dynamic and location-based. This mechanism could be adopted for both macrocells (MCs) and superimposed fixed or mobile small cells (SCs) to mitigate the inter-cell interference (ICI) effects. The proposed power allocation scheme could be termed as Dynamic Power Allocation based on User Location (DPAUL) mechanism, which dynamically changes the transmit power of serving base stations (BSs) depending on the location of users in the cell and then allocates to the concerned BSs. The work illustrates the dynamic downlink interference mitigation occurring within the cells, mainly due to the mobile SCs and mobile users. The Cell-User Mobility model has been adopted in this work, to analyze the mobility of cells and its users within the network. The proposed DPAUL scheme has been compared with some other works, including the author’s previously proposed DPAM mechanism. The proficiency of the proposed scheme on setup network has been investigated with sub 6 GHz and mmWave spectrums, and then effect on performance metrics such as sumrate, user throughput, energy-efficiency, and outage probability have been observed.

Fluid-Based Energy Efficiency Analysis of JT-CoMP Scheme in Femto Cellular Networks

As the progress towards 5G wireless networks, energy efficiency (EE) has become one of the critical design criteria for future wireless communications. In this regard, the joint transmission coordinated multipoint (JT-CoMP) technique is considered as a promising technology to save energy by mitigating intercell interference and improving spectral efficiency. However, additional power for data sharing and resource information is consumed by this technology. To evaluate the EE in dense femtocell networks with joint transmission CoMP approach and capture the significant factors involved in the energy consumption process, representative and accurate models are needed. In this article, while applying a realistic power consumption model, we develop a tractable model in a JT-CoMP downlink transmission network based on spatial fluid modeling, which reduces the analysis complexity. Moreover, the proposed model’s effectiveness and accuracy are shown by comparing the obtained results to those of Monte Carlo simulations. Afterward, our simulation outcomes point out that EE is mainly highest in free space than urban areas, and can be improved with the increase of cooperative BSs number for a constant backhauling power cost. Moreover, in the case of a variable backhauling power cost, JT-CoMP becomes beneficial when the SINR threshold is 3dB.

Dimming-Aware Interference Mitigation for NOMA-Based Multi-Cell VLC Networks

This letter proposes inter-cell interference mitigation in a dimming-aware way for multi-cell visible-light communication networks, through efficient time-scheduling, scaling, and coordination of non-orthogonal multiple access (NOMA) transmissions at the access points. By this method, users are grouped and served in different time slots depending on whether they are at the center or at the edge of the cell. This reduces the number of NOMA users per time slot, which decreases the network computational complexity, by reducing the average number of successive interference cancellation steps. Comparison of the proposed scheme with the classical NOMA over different dimming constraints shows an improvement of up to 39% and 37% in the average sum-rate and fairness, respectively, for a 30% duty cycle transmission in a 4-cell scenario with 8 users.

Dynamic and location‐based power allocation mechanism for inter‐cell interference mitigation in 5G heterogeneous cellular network

SummaryIn this paper, a dynamic and location‐based power allocation mechanism is proposed which could be adopted at both macrocell (MC) and overlaid fixed/mobile small cells (SCs) to mitigate inter‐cell interference (ICI) effects in heterogeneous cellular networks (HetCNs). The proposed Dynamic Power Allocation based on User Location (DPAUL) mechanism allows both MCs and deployed fixed/mobile SCs to dynamically allocate transmit power to its serving base stations (BSs) based on the location of a user in the cell. The paper illustrates the mitigation of dynamic downlink interferences occurring due to the mobility of SCs and users. The mobility of cell and its users is analyzed by introducing the Cell‐User mobility (CUM) model in the network. The proposed DPAUL mechanism is compared with the authors' other ICI mitigation techniques: Dynamic Fixed Region Cooperation (DFRC) and Dynamic Power Allocation Mechanism (DPAM). The network metrics Sumrate, User throughput, Energy‐efficiency, and Outage probability are investigated with allocation of sub 6 GHz and mmWave spectrums at MCs and fSCs/mSCs, respectively.

Evidence‐based dynamic radio resource allocation to mitigate inter cell interference employing cooperative communication

The paper proposes a framework for traffic based dynamic radio resource allocation to mitigate Inter Cell Interference (ICI) in cooperative communication for LTE MIMO-OFDMA systems using evidence theory. The objective is to address ICI, by dynamic user categorization, resource partitioning and management of radio resources. Through evidence based dynamic categorization of users, dynamic frequency planning and dynamic allocation of resources, spectral efficiency is enhanced by increasing data rate of users. It requires the cell users to be categorized into edge and center users depending on the confidence factor, computed using Dempster Shaffer Combinational Rule (DSCR). A traffic based dynamic Soft Frequency Reuse (SFR) plan is proposed using categorized user information to partition the available resources i.e., subcarrier and associated power. A subset of resources is allocated to identified edge users based on dynamic traffic. The traffic based evidential categorization of users, partitioning of resources provides improved data rate and spectral efficiency of edge users. The allocation of resources is dynamic in the proposed framework, leading to an improvement of spectral efficiency from 6.6 b/s/Hz to 12.4 b/s/Hz in a cell. The proposed methodology adapts to the user traffic in a cell and allocates the resources satisfying maximum users.

Dynamic and energy‐efficient ICI mitigation techniques for mobility‐based 5G HetCN

In this study, two dynamic mechanisms are proposed to mitigate inter-cell interference (ICI) in the heterogeneous cellular network (HetCN) namely: Dynamic Fixed Region Cooperation (DFRC) and Dynamic Power Allocation Mechanism (DPAM). The DFRC allows serving mSCs and other interfering base stations (BSs) to cooperate during transmission of a signal to a user. The DPAM dynamically allocates power to serving BS based on the farthest user in a cell. The study illustrates downlink interferences typically linked with a HetCN. For analysis, a macrocell (MC) network distributed with heterogeneous users is overlaid with both fixed and mobile small cells (SCs). The authors also introduced the cell-user mobility model for deployed mobile SCs in the network. The effects on network performance metrics: Sumrate, Average user throughput, and Energy efficiency are investigated with an allocation of sub 6 GHz and mmWave bands at MC and deployed SCs, respectively.