Effect Of Inter-cell Interference Research Articles

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.

Ambient BackCom in beyond 5G NOMA networks: A multi-cell resource allocation framework

The research of Non-Orthogonal Multiple Access (NOMA) is extensively used to improve the capacity of networks beyond the fifth-generation. The recent merger of NOMA with ambient Backscatter Communication (BackCom), though opening new possibilities for massive connectivity, poses several challenges in dense wireless networks. One such challenge is the performance degradation of ambient BackCom in multi-cell NOMA networks under the effect of inter-cell interference. Driven by providing an efficient solution to the issue, this article proposes a new resource allocation framework that uses a duality theory approach. Specifically, the sum rate of the multi-cell network with backscatter tags and NOMA user equipment is maximized by formulating a joint optimization problem. To find the efficient base station transmit power and backscatter reflection coefficient in each cell, the original problem is first divided into two subproblems, and then the closed form solution is derived. A comparison with the Orthogonal Multiple Access (OMA) ambient BackCom and pure NOMA transmission has been provided. Simulation results of the proposed NOMA ambient BackCom indicate a significant improvement over the OMA ambient BackCom and pure NOMA in terms of sum-rate gains.

5G Cellular Networks: Coverage Analysis in the Presence of Inter-Cell Interference and Intentional Jammers

Intentional jammers (IJs) can be used by attackers for the launching of distributed denial-of-service attacks in 5G cellular networks. These adversaries are assumed to have adequate information about the network specifications, such as duration, transmit power and positions. With these assumptions, the IJs gain the ability to disrupt the legitimate communication of the network. Heterogeneous cellular networks (HetNets) can be considered a vital enabler for 5G cellular networks. Small base stations (SBSs) are deployed inside macro base station (MBS) to improve spectral efficiency and capacity. Due to orthogonal frequency division multiplexing assumption, HetNets’ performance is mainly limited by inter-cell interference (ICI). Additionally, there exist IJs-interference (IJs-I), which significantly degrades the network coverage depending on the IJs’ transmit power levels and their proximity with the target. The proposed work explores the uplink (UL) coverage performance of HetNets in the presence of both IJs-I and ICI. Moreover, to reduce the effects of ICI and IJs-I, reverse frequency allocation (RFA) is employed which is a proactive interference abating scheme. In RFA, different sub-bands of the available spectrum are used by MBS and SBS in alternate regions. The proposed setup is evaluated both analytically as well as with the help of simulation. The results demonstrate considerable UL coverage performance improvement by effectively mitigating IJs-I and ICI.

Multiobjective Beamforming Power Control for Robust SINR Target Tracking and Power Efficiency in Multicell MU-MIMO Wireless System

This study proposes a multiobjective beamforming power control scheme to achieve the robust quality of service (QoS), the optimal signal-to-interference-plus-noise ratio (SINR) target tracking and the minimum average power consumption simultaneously in multicell multiuser MIMO (multicell MU-MIMO) wireless system with imperfect channel. The advantages of the proposed multiobjective beamforming power control optimization method are threefold. First, the proposed power control scheme can simultaneously achieve three objectives as follows: 1) the optimal H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> robust SINR target tracking performance, 2) the optimal H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> SINR target tracking performance, and 3) the minimum average power consumption in the multicell MU-MIMO wireless system. The proposed multiobjective optimization problem (MOP) is equivalently derived as aMOP by minimizing their corresponding upper bounds under the constraint of a set of linear matrix inequalities (LMIs). Second, without the requirement of statistical information and the norm-bounded condition of the channel uncertainty, the effect of inter-cell interference, intra-cell interference, channel uncertainty, round trip delay, and noise can be efficiently attenuated by the proposed robust SINR target tracking method. Third, through the proposed LMIs-constrained multiobjective evolution algorithm (MOEA), the designer can obtain Pareto optimal solutions efficiently with a good distribution along the Pareto front to achieve the proposed multiobjective power control design. Several simulation examples with the proposed multiobjective control scheme are produced with favourable results under the guarantee of the theoretical analysis.

ICI effects on user mobility with different FR schemes in a multi‐cell cellular network

Inter-cell interference (ICI) occurs largely due to allocation or utilisation of the same spectrum in the adjacent or nearby cells has been a root of user throughput degradation in cellular networks. Additionally, limited spectrum and wide augment in the cellular terminals has been a factor for ICI effects. This study proposed a new frequency reuse (FR) scheme ‘FR-9’ and addresses new planning patterns for available FR schemes with 19-macrocells (MCs) network. The work also discusses the effect of ICI on the user, during stationary and mobility to adjacent cells/sectors with different FR schemes. The different scenarios are examined with regular and rearrangement of frequency bands among the network with sectorisation of MCs. The intended user performances such as received signal-to-interference-plus-noise ratio (SINR) and throughput are compared for presented scenarios and FR schemes. The simulated result depicts that for 19-MCs network, 120° sectorisation with proposed regular FR-9 (RegFR-9) pattern results in receiving of good SINR by the user compared to other FR schemes. The results show that FR-3 planning outperforms compared to other presented schemes during stationary and mobility of the user to MC3. The planning of FR-1 among MCs shows better throughput when the user moves within MC1. RegFR-3 seems better when the user moves to MC4.

Effect of intercell interference on cell boundary users in three‐cell and seven‐cell HetCN

SummaryIndoor and cell‐edge coverage has been a major issue of concern for predeployed traditional macrocell (MC)–based homogeneous cellular network. Moreover, with the extensive increase of mobile users and developments of smart and highly specified devices, user demands and activities have led to huge cellular traffic. The key solutions to these that include network upgradation, overlaying of small cells (SCs), and scaling of resources have turned out to be the major causes for intercell interference (ICI) and energy‐efficiency degradation in heterogeneous cellular networks (HetCNs). In this paper, authors have tried to analyze the downlink performance metrics of cell boundary users with MCs overlaying SCs for three‐cell circular and seven‐cell sectorized networks through frequency reuse (FR) schemes. This paper also discusses the impact of ICI being encountered by users and the effect of SCs on the energy efficiency of the network. The locations for SCs are perceived where user density is large and demands high data rate such as at hot‐spot (HS) areas, railway stations, shopping malls, working farms, and organization. The performance metrics sum rate, average user throughput, and energy efficiency are compared by employing FR‐1 (full spectrum) and FR‐3 (three subbands) among MCs and deployed SCs. For both scenarios, simulation results and analyses depict that without SCs, utilization of FR‐1 results in performance degradation due to ICI effects. However, the downlink performance of cell boundary user and energy efficiency of the network could be enhanced by overlaying SCs near cell boundaries of preexisting MCs along with the allocation of FR‐1.

LTE‐Advanced network inter‐cell interference analysis and mitigation using 3D analogue beamforming

This study considers the effects of inter-cell interference (ICI) on the LTE-Advanced physical layer downlink channel for different macro-cell diameters and base station (BS) antenna heights with a frequency reuse factor of one and three sectors per site. A site-specific three-dimensional (3D) ray-tracing tool is used to model the communication channel between the BSs (main and interfering links) and user equipment (UE) terminals. System performance is evaluated in terms of average spectrum efficiency, cell edge throughput and outage probability. Two 3D analogue beamforming algorithms are proposed to mitigate the harmful effects of ICI. These are applied at the BS and/or the UE and compared with a more traditional fractional frequency reuse deployment. Simulations demonstrate that the proposed beamforming algorithms provide significant system level improvements, especially for low BS antenna heights. With 10 × 10 and 2 × 2 antenna arrays at the BS and the UE, respectively, the proposed MaxMin-BF algorithms can provide an average spectrum efficiency of 3.6 bps/Hz and a cell edge throughput of 0.56 bps/Hz up to a cell diameter of 1250 m. Importantly, these results satisfy the IMT-Advanced requirements for candidate fourth generation and beyond radio interface technologies. Furthermore, the performance of proposed beamforming algorithms outperforms those achieved using fractional frequency reuse.

Throughput and Power Efficiency Analysis Considering Traffic Loads in FFR with Movable Boundary

ABSTRACTIn Fractional frequency reuse (FFR) technique, the available physical resource blocks are reused among different cells in a manner that co-channel interference and/or inter-cell interference effect is reduced. However, when the resources are highly utilized, the sharing of these resources becomes exhausted and/or limited, and this leads to a high interference and hence high call blocking probability. Therefore, this paper proposes a call admission control in FFR to improve the performance of the FFR-based cellular system. The results of the two quality of service (QoS) constraints, the call blocking probabilities and the resource utilizations for users are used for some design criteria of the cell inner/outer area to maximize the throughput and hence for the evaluation of the system power efficiency.

Exploiting Impacts of Intercell Interference on SWIPT‐Assisted Non‐Orthogonal Multiple Access

In this paper, we examine the influence of intercell interference (ICI) on the system outage behavior with important derived results in the proposed model of simultaneous wireless information and power transfer (SWIPT) together with the nonorthogonal multiple access (NOMA) using the amplify‐and‐forward protocol. We derive the closed‐form expression of coverage probability for two NOMA users as a function of the signal‐to‐interference‐plus‐noise ratio (SINR). To fully take into account the effect of ICI, we adopt more practical parameters to evaluate the optimal power splitting coefficient regarding energy harvesting system performance analysis. Furthermore, to consider a more practical scenario, based on the fact that the number of ICI sources can affect wireless powered relays, we investigate the average outage probability by considering impacts of the reasonable number of participating ICI.

Row-by-Row Coding Schemes for Inter-Cell Interference in Flash Memory

Inter-cell interference (ICI) is a significant cause of errors in flash memories. In single-level cell (SLC) flash memory, ICI arises when 1 0 1 patterns are programmed either in the horizontal or vertical directions. Since data pages are written sequentially in horizontal wordlines, one can mitigate the effects of horizontal ICI by applying conventional constrained codes that forbid the 1 0 1 pattern. This approach does not address the problem of vertical ICI, however. In this paper, a row-by-row coding technique that eliminates vertical 1 0 1 patterns while preserving the sequential wordline programming order is presented. This scheme, though efficient, necessarily suffers a rate loss of almost 20%. We therefore propose another coding scheme, combining a weak constraint on vertical 1 0 1 patterns with a systematic error-correcting code, that can mitigate vertical ICI errors while achieving a higher overall coding rate, provided that the vertical ICI error probability is sufficiently small. Some extensions for multi-level cell (MLC) flash memory are discussed as well.

Iterative beamforming algorithm for improved throughput in multi‐cell multi‐antenna wireless systems

Mitigating the effects of inter-cell interference in a multi-cell wireless network is essential to improve the achieved performance. In this study, the authors develop an iterative distributed beamforming scheme that addresses the effect of inter-cell interference problem on the downlink of a multi-cell multi-antenna wireless system with linear beamformers. The proposed scheme attempts at improving the overall system performance by exploiting network duality principle to jointly compute the optimal transmit and receive beamforming weights such that the desired received power is maximised while minimising the caused interference to other users. Network duality allows the serving base stations and the intended users to jointly compute the beamforming weights of the transmit/receive antenna elements, which improve network performance. The proposed scheme considers variable levels of channel information feedback and different transmit–receive antenna configurations. Simulation results show that a significant performance improvement is achieved through the joint optimisation of the transmit/receive beamforming vectors. Results also indicate that compared with reference schemes, their scheme improves the achieved sum-rate by up to 50%.

Resource Management and Inter-Cell-Interference Coordination in LTE Uplink System Using Random Neural Network and Optimization

In orthogonal frequency division multiple access systems, inter-cell interference (ICI) can be considered as a collision between resource blocks (RBs), which can be reduced by employing a power control strategy at colliding RBs. This paper presents a random neural network (RNN) and a genetic algorithm-based hybrid cognitive engine (CE) architecture to reduce the ICI and achieve the coverage and capacity optimization in a long-term evolution uplink system. The embedded CE within eNodeB learns from the local environment about the effect of ICI on the reliability of communications. Consequently, the CE dynamically selects the optimal transmission power for serving users based on an experienced signal-to-interference-plus-noise ratio and an ICI on a scheduled RB in the subsequent transmission time intervals. The CE also suggests acceptable transmit power to users operating on the same scheduled RB in adjacent cells through the X2 interface (a communication interface between eNodeBs). The RNN features help the CE to acquire long-term learning, fast decision making, and less computational complexity, which are essential for the development and practical deployment of any real-time cognitive communication system. In six different test cases, the simulation results have shown improvements up to 87% in long-term learning and a quick convergence of the RNN as compared with artificial neural network models. Moreover, the gains of 7% in average cell capacity and 118% in system coverage have been achieved as compared with a fractional power control method.

Cooperative Inter-cell Interference Mitigation Scheme with Downlink MU-MIMO Beamforming for Dense Wireless LAN Environment

A cooperative inter-cell interference (ICI) mitigation scheme with transmit beamforming for dense wireless LAN systems is proposed. The proposed scheme applies transmit beamforming used for downlink multiuser MIMO in order to mitigate the effect of ICI and selectively determines whether an access point (AP) performs null beamforming for each station (STA) in overlapping basic service sets (OBSSs) according to the ICI power. Null beamforming is used to suppress ICI if its power exceeds a threshold, otherwise, it is not carried out and the transmit antenna is used to obtain a diversity gain for STAs associated with the AP. Computer simulations confirm that the achievable rate obtained with the proposed scheme is superior to that obtained with either time resource sharing or conventional ICI mitigation in an OBSS environment.

On Multi-cell Packet Scheduling of LTE-A Cellular Networks: A Survey of Concepts Related Challenges and Solutions

The upcoming generations of cellular networks are foreseen to deliver a ubiquitous access to the rapid growing volume of mobile users. Therein, a stunning key feature of LTE is the ability to adapt the advancement in Radio Resource Management entity which scales up its potential to deal with multi-transmission scenarios by employing novel multi-antenna techniques on eNBs. This survey come in place to enlighten the aforementioned notions and deeply investigates the principles and approaches of LTE/LTE-A packet scheduling that are adapted in either Dl or UL channels. The main purpose of the study is to come out with a preliminary conceptual design of an optimal scheduling techniques in multi-cell heterogeneous environment keeping in mind the effects of inter-cell interference on the model overall QoS. Finally, it is recommended that a wise packet scheduling model for multi-cell LTE-A should involve an optimal trade-off between several QoS parameters having in mind interference mitigation as a main concern. Whereby, performance features of the known LTE/LTE-A scheduling categories, opportunistic scheduling, ICIC and CoMP can be realized in a single model.

Interference Self-Coordination: A Proposal to Enhance Reliability of System-Level Information in OFDM-Based Mobile Networks via PCI Planning

For system-level information in OFDM-based mobile networks, the full-cell coverage requirement raises the issue of Inter-Cell Interference (ICI) in physical control channels. Unfortunately, conventional approaches (e.g., scheduling, beamforming) cannot effectively deal with this kind of ICI because of configuration limitations in physical control channels. To solve this challenge, this study defines a new concept of `Interference Self-Coordination (ISC)' for enhancing this system-level information delivery. Specifically, we apply ISC to relieve the ICI effect over the Physical Downlink Control Channel (PDCCH), the most important physical control channel in Long-Term Evolution (LTE/LTE-Advanced) networks, in which Physical Cell Identifier (PCI) planning naturally serves as a self-coordination mechanism. We prove that PCI planning is the most effective solution to relieve ICI over PDCCHs, under the constraint of non-orthogonal control regions between neighboring cells. Since PCI planning is an NP-Complete problem, heuristic-strategy algorithms are devised for implementation, which are self-adaptive to dynamic configurations of the network and system, and compatible with any applicable ICI solutions. The numerical analysis and system-level simulation experiment results demonstrate that this proposal can increase overall system throughput by up to 17%, and also improve cell-edge throughput by up to 42%. In the worst 5% of sectors, the proposal can still obtain 45% system throughput and 200% cell-edge throughput gain.

Energy efficient coordinated radio resource management: a two player sequential game modelling for the long-term evolution downlink

Inter-cell interference (ICI) is a key limiting factor to the radio frequency (RF) energy performance of a multi-cell multi-user radio access network (RAN). The channel quality of the cell edge users is greatly impaired by ICI owing to the fact that cell edge users are furthest away from their serving base stations (BSs) and closest to the interfering BSs. Consequently the BS is compelled to allocate more physical resource blocks [PRBs (In LTE a PRB spans 12 sub-carriers each with a bandwidth of 15 kHz over a 0.5 ms time slot)] to the cell edge users in order to meet their quality-of-service (QoS) targets. The study proposes a novel ICI management technique that mitigates the effects of ICI through a sequential game play between cells in the E-UTRAN [Evolved Universal Mobile Telecommunications Systems (UMTS) terrestrial radio access network] based on the instantaneous cell offered load. The proposed technique is shown to produce greater user channel quality improvements of 4 dB greater than the state-of-the-art ICI management techniques. The channel quality improvements result in a utilisation of less PRBs, RF and radio head energy which translate to energy reduction gains of 34 and 45% at low- and high-offered loads, respectively. In addition the proposed scheme does not require a central processing entity such as a radio network controller and can be implemented in unplanned self-organising networks.

Performance analysis of multiple-input multiple-output singular value decomposition transceivers during fading and other cell interference

A generalised method is derived to compute the error probabilities of singular value decomposition (SVD)-based receivers for a multiple-input multiple-output (MIMO) system with uncoded transmission. The method can be used for a wide class of flat fading environments, including independent and identically distributed (i.i.d.) and semi-correlated Rayleigh and i.i.d. Ricean channels. Although the method is applied to equal-power binary phase shift keying, it can easily be extended to higher-order M-ary phase shift keying (M-PSK) and M-ary quadrature amplitude modulation (M-QAM) signal constellations and adaptive ‘water-filling’ schemes. The error probability curves derived from closed-form formulas and simulations demonstrate very close agreement. The error performances of channel inversion, minimum mean square error and zero forcing receivers are compared with the SVD receiver for a single-user system. The impact of multiple users is considered by studying the performance of an adaptive MIMO SVD transmission scheme operating in a cellular environment. In particular, the effect of inter-cell interference on the performance of the scheme is quantified, modelling the interference as increased Gaussian noise. A number of cellular layouts are examined and the impact of the resulting singal-to-interference and noise ratio on the constellation sizes that can be supported, the BER and so on is considered. The primary metric used for our performance analysis is the error-free transmission rate, which is derived for our adaptive system. For the cellular scenarios considered, it can be found that the effect of interference is considerable and the performance of the adaptive MIMO SVD scheme is only marginally better than that provided by conventional diversity methods.

Commutation Signaling to Combat ISI over Nakagami and Ricean Fading

Bandwidth expanding signaling with quasi-orthogonal short codes is considered. The evaluation of the average probability of error analytically and by simulation is presented, for channels with multipath induced intersymbol interference (ISI) and for two different fading distributions. Namely Nakagami and Ricean fading distributions. The effect of intercell interference due to frequency reuse is also taken into account. Bit error rates (BER) for rake receiver with equal gain combining and postdetection integrator are presented. Both DBPSK and π/41 DQPSK modulations with noncoherent demodulation are analysed. The effect of TCM coding, in the expected BER is also evaluated.