Coexistence Of Long Term Evolution Research Articles

Cross-Tier Interference Mitigation in 3D HetNets for LTE and Wi-Fi Access

Due to the unprecedented rate of transformation in the field of wireless communication industry, there is a need to prioritise the coverage, network power and throughput as preconditions. In Heterogeneous Networks (HetNets) the low power node inclusion like Femto and Pico cells creates a network of Multi-Tier (M-Tier) which is regarded as the most significant strategy for enhancing the coverage, throughput, 4G Long Term Evolution (LTE) ability. This work mainly focuses on M-Tier 3D Heterogeneous Networks Energy Efficiency (EE) based Carrier Aggregation (CA) scheme for streaming real-time huge data like images. At first, M-Tier 3D HetNets scheme was made for investigating Signal to Noise Interference Ratio (SNIR) on assessing the collective Pico-tier and Femto-tier interference. Next, the scheme of channel allocation is scrutinised so as to estimate throughput from the multiple tiers. Additionally, with the use of CA technique, the problem of energy efficiency for M-Tier 3D Heterogeneous Network (HetNet) in relation to energy metrics and throughput was evaluated with the use of LTE and Wireless Fidelity (Wi-Fi) coexistence. The simulation is carried out in a MATLAB setting, and the outcomes reveal a huge impact on EE. The simulation is carried in terms of EE, transmission time, throughput, packet success rate, convergence probability, and coverage region. The analysis from simulation shows that on improving the output of the device, interference among small cell base stations is reduced on increasing EE. The outcomes attained aid in the effective creation of M-Tier 3D HetNets for enhancing EE by employing Multi-Stream Carrier Aggregation (MSCA) in HetNets.

A new fair-efficient spectrum allocation scheme for the LTE and WiFi coexistence platform

Long-term evolution (LTE) carrier aggregation with the unlicensed WiFi spectrum band has been pointed out as a good solution to handle the rapidly increasing wireless data traffic amounts. With both LTE and WiFi networks, the investigation of their coexistence is a hot research topic of active interest, primarily driven by industry and academia. In this study, we investigate a new spectrum allocation scheme for the LTE/WiFi coexistence platform. To maximize the system throughput while guaranteeing a relative fairness between heterogeneous networks, we adopt the cooperative game paradigm to design our novel scheme. According to the basic ideas of Proportional Nash bargaining solution (PNBS) and Zhang’s group bargaining solution (ZGBS), we can leverage a mutual consensus to provide a fair-efficient solution for the LTE/WiFi spectrum sharing problem. Based on the online interactive bargaining approach, network agents work together to effectively share the LTE and WiFi spectrum resources. Under dynamically changing network environments, it is an essential approach to find the relevant trade-off between conflicting requirements, i.e., fairness and efficiency. Validated by simulation results, our proposed scheme can provide important insights into the LTE/WiFi system operations. Finally, we forecast further research trends on the basis of our conclusion.

Unlicensed Spectrum Allocation for LTE and Wi-Fi Coexistence with HAP

In order to accommodate the ever-increasing traffic demands, numerous approaches have been developed to improve spectrum utilization. Among others, the coexistence of LTE (Long-Term Evolution) and Wi-Fi, addressed by the 3GPP (3rd Generation Partnership Project) with hyper access points (HAPs) as bridges, is well recognized as a promising candidate solution. Aimed at improving the spectrum utilization of the unlicensed bands by following LTE-Unlicensed (LTE-U), this article contributes to the determination of the optimal time ratio, δ, for the time-division multiplexing of LTE and Wi-Fi over unlicensed bands. Symmetric allocation with a duty cycle of 50% cannot be an optimal option. Asymmetric allocation according to the quality of service (QoS) requirements and traffic demands should be considered. The problem is formulated as an optimization problem optimizing the total throughput. The lower and upper bounds of δ are obtained according to the QoS requirements of Wi-Fi and the admission control requirements of LTE. The detailed procedure for finding an adequate δ is developed and presented. A series of simulations are conducted to demonstrate the feasibility and effectiveness of the proposed approach. Simulation results show that the proposed approach improves the total throughput without compromising the fairness of Wi-Fi, as intended. Ten percent of improvement in throughput compared with LTE-U can be achieved.

Bi-Criteria Radio Spectrum Sharing With Subspace-Based Pareto Tracing

Radio spectrum is a scarce resource. To meet demands, new wireless technologies must operate in shared spectrum over unlicensed bands (coexist). We consider coexistence of Long-Term Evolution (LTE) License-Assisted Access (LAA) with incumbent Wi-Fi systems. Our scenario consists of multiple LAA and Wi-Fi links sharing an unlicensed band; we aim to simultaneously optimize performance of both coexistence systems. To do this, we present a technique to continuously estimate the Pareto frontier of parameter sets (traces) which approximately maximize all convex combinations of network throughputs over network parameters. We use a dimensionality reduction approach known as active subspaces to determine that this near-optimal parameter set is primarily composed of two physically relevant parameters. A choice of two-dimensional subspace enables visualizations augmenting explainability and the reduced-dimension convex problem results in approximations which dominate random grid search.

Enhanced network sensitive access control scheme for LTE–LAA/WiFi coexistence: Modeling and performance analysis

Implementation of 5G and beyond networks is looking to expand the operation of licensed systems into unlicensed frequency bands through technologies such as license assisted access (LAA) and New Radio Unlicensed (NR-U). LAA aggregates licensed and unlicensed bands for long term evolution (LTE) implementation to address the ever-increasing demand for cellular data traffic and shortage of licensed spectrum. Spectrum-efficient resource-sharing schemes are, however, critical for the harmonious coexistence of LTE–LAA with incumbent systems on the unlicensed band, especially WiFi, while opportunistically improving LTE throughput and enhancing spectrum utilization of the unlicensed band. In this paper, we present a listen before talk (LBT) based clear channel assessment (CCA) mechanism for LAA eNodeBs (eNBs) to improve the coexistence performance of LTE–LAA with WiFi. Particularly, we propose an adaptive exponential backoff scheme for LTE eNB that dynamically updates the contention window (CW) size and transmission opportunity (TXOP) parameters according to network load variations. A three-dimensional discrete Markov model is developed to describe the LBT procedure of LAA eNB, and a performance model is further derived to evaluate steady-state channel access, transmission, and failure probabilities. The proposed scheme’s performance is evaluated in terms of successful transmission probability, throughput, and delay according to the 3GPP and WiFi guidelines. The results are compared with the traditional schemes proposed in literature considering fixed and adaptive CW size for LAA eNB.

Power-Aware Coexistence of Wi-Fi and LTE in the Unlicensed Band Using Time-Domain Virtualization

The rapid increase of mobile devices requires more network capacity as limited licensed spectrum is diminishing access to long-term evolution (LTE) users. As increasing licensed spectrum becomes costly, a cost-effective solution that improves network capacity is needed. Another overlooked issue is spectrum efficiency, where unused resources could be allocated to more LTE users. This article proposes two solutions to address network capacity and spectrum efficiency: moving into unlicensed spectrum and implementing wireless resource virtualization. In addition, as these solutions enhance data rate, thus increasing power consumption, this article includes power-aware optimization as a solution. Operating in the unlicensed band poses a challenge as 5-GHz bands are predominately used by Wi-Fi systems. Based on this challenge, we are proposing a time-sharing wireless resource virtualization (WRV)-based LTE/Wi-Fi coexistence solution that considers joint resource/access point (AP) allocation and power control problems for both technologies. Accordingly, we formulate a mixed-integer nonlinear programming problem and solve using the Lagrangian dual decomposition. We also propose low-complexity heuristics to solve these problems. Results show that the coexistence of Wi-Fi and LTE can be achieved in the unlicensed band with improved power savings using virtualization. Moreover, there is little to no difference in power savings in heterogeneous-traffic scenarios as the algorithm prioritizes maximizing rate to minimizing power.

Energy Efficiency in 5G Communications – Conventional to Machine Learning Approaches

Demand for wireless and mobile data is increasing along with development of virtual reality (VR), augmented reality (AR), mixed reality (MR), and extended reality (ER) applications. In order to handle ultra-high data exchange rates while offering low latency levels, fifth generation (5G) networks have been proposed. Energy efficiency is one of the key objectives of 5G networks. The notion is defined as the ratio of throughput and total power consumption, and is measured using the number of transmission bits per Joule. In this paper, we review state-of-the-art techniques ensuring good energy efficiency in 5G wireless networks. We cover the base-station on/off technique, simultaneous wireless information and power transfer, small cells, coexistence of long term evolution (LTE) and 5G, signal processing algorithms, and the latest machine learning techniques. Finally, a comparison of a few recent research papers focusing on energy-efficient hybrid beamforming designs in massive multiple-input multiple-output (MIMO) systems is presented. Results show that machine learningbased designs may replace best performing conventional techniques thanks to a reduced complexity machine learning encoder

Joint Cancellation of Phase Noise and NB-IoT Interference in OFDM System

In the scenario of the coexistence of long term evolution (LTE) system using orthogonal frequency division multiplexing (OFDM) and narrowband Internet-of-Things (NB-IoT), when the in-band model is used, the narrowband interference caused by NB-IoT will seriously degrade the performance of OFDM. Meanwhile, the phase noise (PHN) generated by the local oscillators also reduce the reliability of OFDM transmission. In this letter, an algorithm of jointly eliminating NB-IoT interference and PHN is proposed within the sparse Bayesian learning framework for OFDM system, when the channel noise follows non-Gaussian distribution. An iterative solution is derived after the optimization structure is constructed. Simulation results demonstrate that the gain of proposed method over the conventional methods is approximately 1.5-3.5 dB when the bit error rate is 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> .

Predicted Decoupling for Coexistence Between WiFi and LTE in Unlicensed Band

Wireless fidelity (WiFi) and long term evolution (LTE) coexistence system has attracted significant attention recently. However, most studies on coexistence only consider the issues about downlink performance and fairness between WiFi network and LTE network. In this paper, we take a comprehensive consideration of both the performance of WiFi and LTE, to propose a downlink/uplink decoupling (DUDe) scheme for the fairness of the coexistence system. Through the process of modeling construction, problem formulation with reformulation, solution and simulations, we illustrate that DUDe can achieve proportional fairness in terms of sum throughput and load balancing between uplink and downlink. In our decoupling model for coexistence between WiFi and LTE, resource allocation is under adaptive spectrum partitioning and users can access each network of WiFi and LTE. Moreover, to make our proposal more realistic, we adopt support vector machine (SVM) to predict the total number of users in WiFi and LTE coexistence system, where the predictive simulation shows its high prediction accuracy with low complexity. We further apply the prediction results to the optimization problem of DUDe. Simulation results manifest that the proposed DUDe scheme has better performance in terms of sum throughput. The sum throughput of DUDe scheme can come up to almost twice more than that of coupled association scheme. The result shows that DUDe can also achieve load balance between uplink and downlink in the coexistence system.

Performance evaluation of video streaming on LTE with coexistence of Wi-Fi signal

The continuous growth in mobile data traffic and limited license wireless spectrum have led to dramatically increase the demand of the radio spectrum. It is widespread the concern about the coexistence of long term evolution (LTE) and Wi-Fi in the unlicensed band. There are several techniques have been proposed to enable the coexistence of LTE and Wi-Fi in the unlicensed band, but these works are targeted on the impact of the LTE to the Wi-Fi network performance. An experiment is carried out in this work to evaluate the impact of Wi-Fi signal on the video streaming in the LTE network. The experimental test comprised of the national instrument (NI) universal software radio peripheral (USRP) 2953R that is controlled by the LabVIEW Communication LTE application framework. Extensiveexperiments are carried out under two scenarios, i.e. (1) Coexistence of LTE and Wi-Fi signal, (2) LTE signal only. Performance evaluations are carried out with different Modulation and coding schemes (MCS) values and different mode of operations, i.e. frequency division duplex (FDD) and time division duplex (TDD) mode. The results illustrated that the interference from Wi-Fi signal caused the performance degradation of the LTE network in throughput and the power received by user equipment (UE).

Q-Learning Based Fair and Efficient Coexistence of LTE in Unlicensed Band.

The increased demand for spectrum resources for multimedia communications and a limited licensed spectrum have led to widespread concern regarding the operation of long term evolution (LTE) in the unlicensed (LTE-U) band for internet of things (IoT) systems. Because Wi-Fi and LTE are diverse with dissimilar physical and link layer configurations, several solutions to achieve an efficient and fair coexistence have been proposed. Most of the proposed solutions facilitate a fair coexistence through a discontinuous transmission using a duty cycling or contention mechanism and an efficient coexistence through a clean channel selection. However, they are constrained only by fairness or efficient coexistence but not both. Herein, we propose joint adaptive duty cycling (ADC) and dynamic channel switch (DCS) mechanisms. The ADC mechanism supports a fair channel access opportunity by muting certain numbers of subframes for Wi-Fi users whereas the DCS mechanism offers more access opportunities for LTE-U and Wi-Fi users by preventing LTE-U users from occupying a crowded channel for a longer time. To support these mechanisms in a dynamic environment, LTE-U for IoT applications is enhanced using Q-learning techniques for an automatic selection of the appropriate combination of muting period and channel. Simulation results show the fair and efficient coexistence achieved from using the proposed mechanism.

Joint Optimization of Channel Selection and Frame Scheduling for Coexistence of LTE and WLAN

Recently, the interest in operating long term evolution (LTE) in unlicensed bands (i.e., LTE-U) has increased. However, since LTE does not sense for channel vacancy prior to transmissions, whereas a wireless local area network (WLAN) is based on carrier sensing multiple access, LTE interference severely degrades the performance of WLAN. To maximize the LTE throughput while maintaining fairness between LTE and WLAN, we formulate a joint optimization problem of channel selection and frame scheduling in LTE. As a practical solution of this problem, we propose a low-complexity heuristic algorithm called the sequential operation algorithm (SOA). Evaluation results demonstrate that SOA can achieve an LTE throughput comparable to that of the optimal solution, while maintaining fairness between LTE and WLAN by selecting appropriate channels and conducting effective frame scheduling.

Spectral Overlap Optimization for DVB-T2 and LTE Coexistence

In this paper, we analyze the spectral coexistence between the second generation terrestrial digital video broadcasting (DVB) and the long term evolution (LTE) networks. In particular, the global spectral efficiency (SE) of both systems is investigated when a partial spectral overlap between DVB and LTE signals occurs. Our contribution lies in twofold: 1) the interfering signal variance in each network is derived analytically according to the frequency overlap while taking into account the difference between the characteristics of LTE and DVB networks, especially the OFDM subcarrier spacing and then the OFDM symbol duration and 2) SE is derived with uniform and non uniform power allocation between overlapped and non overlapped subcarriers of the two networks. This derivation offers an analytical evaluation of the effect of the spectral overlap ratio variation and different power allocation scenarios and provides insightful results on the cooperation between the two networks.

Opportunistic Coexistence of LTE and WiFi for Future 5G System: Experimental Performance Evaluation and Analysis

To alleviate the problem of scarce spectrum resources and meet the ever-increasing of mobile broadband data traffic demands, Licensed Assisted Access (LAA)-Long Term Evolution (LTE), operating in the unlicensed spectrum, is a promising solution. Considering that the unlicensed spectrum is shared by a few incumbent systems, such as IEEE 802.11 (i.e., WiFi), one main target is to guarantee the friendly and harmonious coexistence of LTE with other wireless systems in the unlicensed spectrum. Both listen-before-talk (LBT) and duty cycle methods are regarded as effective ways to solve the coexistence problem in academia and industry so far. Although there are a large number of theoretical researches on LTE in unlicensed spectrum (LTE-U), field trail results are still lacking. In this paper, an experimental testing platform is deployed to model the realistic environment. This paper focuses on three aspects. First, a typical indoor field trial scenario in 5.8 GHz unlicensed bands is deployed, and the performance of LTE-U and WiFi, including coverage and capacity, is evaluated. Specifically, a methodology to determine the proper clear channel assessment energy detection (CCA-ED) threshold for LTE-U is proposed to implement the friendly coexistence between LTE-U and WiFi systems. Second, supplementary downlink (SDL) and Cell ON/OFF mechanisms are investigated to verify the fair coexistence between LAA and WiFi in the unlicensed spectrum. Third, the Enhanced Cell ON/OFF scheme, which introduces Clear to Send (CTS)-to-Self (CTS2S) message, is discussed and evaluated. Based on the built testbed, we obtain threefold conclusions. First of all, introducing LTE into unlicensed spectrums can greatly improve the spectrum efficiency and optimize wireless resources. Furthermore, test results and analyses show that a proper CCA-ED threshold is necessary for coexisting friendly and fairly among different systems, and experiments are also provided to validate the feasibility of the suggested method in various scenarios. Second, experimental results show that SDL mechanism guarantees relatively friendly and harmonious coexistence between LAA and WiFi only in the sparse scenario, while basic Cell ON/OFF mechanism is more effective to ensure coexistence between LAA and WiFi than the SDL. Finally, with the introduction of CTS2S message, the Enhanced Cell ON/OFF scheme is able to achieve more peaceful coexistence between LTE and WiFi users employed in the same bands compared with the Basic Cell ON/OFF scheme.

On the Coexistence of LTE-LAA in the Unlicensed Band: Modeling and Performance Analysis.

Long term evolution (LTE) technology leveraging the unlicensed band is anticipated to provide a solution for the challenges stemming from the rapid growth of mobile wireless services, the scarcity of available licensed spectrum, and the expected significant increase in mobile data traffic. Ensuring fair operation in terms of spectrum sharing with current unlicensed spectrum incumbents is a key concern relative to the success and viability of Unlicensed LTE (U-LTE). This paper addresses the problem of modeling and evaluating the coexistence of LTE license-assisted-access in the unlicensed band. The paper presents a novel analytical model using Markov chain to accurately model the LAA listen-before-talk scheme, as specified in the final technical specification 36.213 of 3GPP release 13 and 14. Furthermore, model validation is demonstrated through numerical and simulation results comparison. Model performance evaluation is examined and contrasted with IEEE 802.11 distributed coordination function. Finally, a comprehensive coexistence performance analysis is conducted for both homogeneous and heterogeneous network scenarios and coexistence results are presented and discussed herein.

On a fair coexistence of LTE and Wi-Fi in the unlicensed spectrum: A Survey

To overcome the lack of spectrum resources, the proposal of extending LTE (Long Term Evolution) to the readily available unlicensed spectrum is receiving much attention. However, gaining capacity in a band where Wi-Fi is widely used and guaranteeing fairness between systems is not an easy to address issue. Analyzing the impact of operating LTE in the unlicensed band on the performance of Wi-Fi and devising solutions to minimize such an impact have been the goals of a considerable amount of work carried out by the research community, standardization bodies and telecom operators. In this paper, we first present a basic overview of Wi-Fi and LTE, which serves the purpose of illustrating why the fair coexistence of the two technologies in the unlicensed band is an issue. Basically, since LTE has been designed to operate in licensed bands, the centralized scheduling performed by LTE eNodeBs saturates all the channel resources, while Wi-Fi stations refrain from transmitting if the channel is sensed busy. Then, we illustrate the main approaches proposed to ensure a fair coexistence between Wi-Fi and LTE in the unlicensed band, namely Listen Before Talk (LBT) and Almost Blank Subframe (ABS), along with some other minor techniques. We describe the main solutions that are currently being developed by standardization bodies and telecom industry: LTE–U, Licensed Assisted Access (LAA) and MuLTEfire. Finally, we present an overview of the work appeared in the literature analyzing the impact of LTE on the performance of Wi-Fi and proposing solutions to mitigate such an impact.

License assisted access-WiFi coexistence with TXOP backoff for LTE in unlicensed band

License assisted access (LAA) was proposed as a solution to the challenge of satisfying high throughput requirement in cellular network with limited licensed band. LAA uses long term evolution (LTE) carrier aggregation technique to combine licensed and unlicensed bands, specifically 5 GHz WiFi band, in order to achieve high data rates. However, LAA has several critical concerns for services provision on 5 GHz unlicensed band. In this article, an overview of the techniques concerning the coexistence of LTE and WiFi on the same unlicensed band is presented. We first present several general approaches including power control of LTE evolved Node B (eNB), carrier selection, LTE duty cycling, self clear to send (CTS) and request to send/CTS (RTS/ CTS), and listen before talk (LBT). Then, we focus on LBT techniques for LAA-WiFi coexistence and discuss how LBT based coexistence solutions can dynamically respond to the variations in network load and ensure fair coexistence in a distributed manner. Based on the LBT mechanism, we also present a fairness-aware LAA-WiFi coexisting scheme with TXOP (transmitted in a single transmission opportunity) backoff for LAA eNB. Finally, the performances of various LBT solutions for LAA-WiFi coexistence are evaluated using Markov chain analytical model.

LTE and WiFi co-existence in 5 GHz unlicensed band

Since the future mobile networks will require significantly higher data throughput, and the Long-Term Evolution (LTE) licensed bands are already occupied, the frequency band extension and the data rate increase may be achieved by using some of the available unlicensed bands. The most appropriate unlicensed band for this purpose lies in 5 GHz frequency range. However, this unlicensed band is already occupied by WiFi networks and a special attention has to be paid to coordinate these two different networks in the shared spectrum usage. Therefore, this paper considers the shared access co-existence in 5 GHz unlicensed band between uncoordinated LTE and WiFi networks. More precisely, it considers the influence of the LTE downlink transmission on the performance of the WiFi networks. The experimental results show that the LTE significantly degrades the WiFi network performance, which means that some of the coordination algorithms have to be employed.

WiFi leakage detection in LTE downlink for in‐device interference avoidance

To allow users to access networks ubiquitously, more user equipments contain multiple radio transceivers. Because of the proximity of transmit and receive frequencies of in-device wireless technologies, the transmitter (TX) of one in-device wireless technology can interfere with the reception of another technology within the same device, and the spurious emissions of the aggressor TX may result in unacceptable interference at the victim receiver. Hence, it is crucial to detect the in-device interference and adapt strategies to avoid harm. Here, we consider one scenario in 3GPP discussions: the co-existence of Long-Term Evolution (LTE) with WiFi. Different from traditional spectrum sensing which detects signal in the background of Gaussian noise, the WiFi leakage detection in this study aims to detect WiFi leakage in the presence of both LTE signal and noise. Furthermore, most of the WiFi signal features are lost in the WiFi leakage because of the LTE RX filtering which makes the WiFi leakage problem very challenging. By identifying unique features of the WiFi leakage, we investigate this problem thoroughly and propose a suite of detection algorithms, including energy-ratio-based, entropy ratio-based and cyclostationary analysis-based algorithms. Simulations under different scenarios are presented to illustrate the effectiveness and efficiency of the proposed techniques.