Performance Of Cell-edge Users Research Articles

Enhancing QoS Performance for Cell Edge Users Through Adaptive Modulation and Coding in IEEE 802.11ac WLANs

Wireless communication networks, such as IEEE 802.11ac Wireless Local Area Networks (WLANs), often encounter challenges in providing consistent Quality of Service (QoS) to users situated at the cell edge. The inherent variations in channel conditions, particularly lower signal-to-noise ratios (SNRs) in these regions, lead to compromised data rates and reliability, resulting in significant degradation of throughput. This study presents an innovative solution in the form of an Adaptive Modulation and Coding Scheme (AMCS) algorithm tailored to enhance QoS performance for cell edge users. The primary objective of the AMCS algorithm is to optimize QoS by dynamically adjusting the transmission data rate based on the observed channel conditions, quantified using SNR as a channel state indicator. Conventional approaches might unilaterally select the lowest data rate in challenging conditions, prioritizing reliability at the expense of throughput. However, the proposed AMCS algorithm takes a distinct approach by intelligently determining the Modulation and Coding Scheme (MCS) that offers an optimal balance between throughput and reliability for the given SNR level. To achieve this, the algorithm utilizes real-time SNR measurements to select an MCS that ensures a stable connection while also maintaining an acceptable data rate. By adapting the MCS based on the current SNR, the algorithm aims to mitigate the adverse effects of poor channel conditions experienced by cell edge users. The innovation of the AMCS algorithm lies in its ability to make dynamic adjustments, allowing users to experience improved data rates without compromising connection stability. Through extensive simulations and evaluations, the proposed AMCS algorithm showcases its efficacy in enhancing QoS performance at the cell edge. The algorithm's adaptive approach successfully achieves higher data rates and improved reliability by selecting appropriate MCS configurations tailored to the observed SNR levels. This innovative technique provides a promising solution to the challenge of striking the right balance between throughput and reliability in wireless communication networks, ultimately leading to an improved user experience for those at the network's periphery.

Partial cooperative NOMA for improving outage performance of edge users

ABSTRACT Providing reliable service to cell edge users has been a practical challenge for network operators due to the deep fading effects and limited base station (BS) resources. The low received signal strength causes the Quality of Service (QoS) degradation of the cell edge users and hence demands appropriate solutions to improve the user connectivity. To address this issue, this article proposes a two-tier partial cooperative relaying scheme, deployed in a non-orthogonal multiple access (NOMA)-based downlink network that serves the edge users with the minimum required QoS. Comparative performance analysis has been presented for two relaying schemes: amplify-and-forward (AF) and partial decode-and-forward (DF) in terms of outage probability and overall sum rate of the edge users. Additionally, the maximal ratio combining (MRC) diversity technique is integrated with the relaying network to further enhance the QoS of cell edge users. The impact of successive interference cancellation (SIC) on the outage performance has been thoroughly investigated. It has been established through extensive simulation that the partial DF technique is a promising relaying technique to improve the overall performance of cell edge users.

GSIC for Uplink NOMA With Multiple Intelligent Reflecting Surfaces

Intelligent reflecting surface (IRS) is treated as a cutting-edge technology to boost spectrum and energy efficiency for future wireless communications. In this letter, multiple IRSs are deployed to obtain better performance of cell-edge users and group-level successive interference cancellation (GSIC) is conceived to distinguish the users’ signals of different groups. In order to get the minimum overall transmission power for IRS-assisted uplink multi-antenna non-orthogonal multiple access (NOMA) systems, all user’s transmission power and the IRSs’ phase shifts are jointly devised to achieve this goal. Particularly, a sequential rotation method is applied to optimize phase shifts effectively. It is clearly illustrated from simulation results that our proposed scheme can dramatically decrease total transmit power in comparison with a variety of benchmarking methods.

Promoting fractional frequency reuse performance for combating pilot contamination in massive multiple input multiple output

<span>Massive multiple-input multiple-output (MIMO) improves spectrum efficiency by increasing the capacity of the wireless structure. Therefore, massive MIMO is promising for fifth generation (5G) wireless communications. In massive MIMO, channel estimation is a crucial part that should achieve reliable performance. Pilots are sent from the end-users to be used for estimating the channel. However, the problem of interference in pilot contamination affects the performance for cell-edge users. Specifically, pilot contamination appears when the same pilot sequence is utilized at the same time by more than one terminal. This lead to an inaccurate estimation of the channel. Consequently, the decoded data will not be reliable. For mitigating these pilot contamination effects, an enhanced fractional frequency reuse (eFFR) scheme is proposed that uses an algorithm in the allocation of pilot sequences to end users’ devices based on the locations of the users from the target base station (BS). The simulation results exhibit that the proposed scenario outweighs the traditional FFR within both signal to interference, and noise ratio (SINR), and capacity. Consequently, the suggested scenario enhances the performance of more than 80% of the cell terminals and the other 20% of the terminals have a slightly lower performance compared to the FFR.</span>

Interference management in backhaul constrained 5G HetNets through coordinated multipoint

The inter-cell interference (ICI) is a major bottleneck that harshly impairs the cell-edge performance in the cellular networks. In heterogeneous networks (HetNets), time domain enhanced inter-cell interference coordination (TD-eICIC) is a promising and well recognized cell-coordination technique to cope with the inter-tier cell interference. However, this scheme incurs significant loss in the allocated spectrum resources caused by blanked or reduced power subframes. The coordinated multipoint (CoMP) is a spectrally efficient and dynamic coordination approach to improve the performance of cell-edge users. In this article, first we provide a brief overview of conventional interference mitigation techniques in the heterogeneous networks. Next, application of CoMP on top of conventional TD-eICIC is investigated to diminish the pitfalls of TD-eICIC. Primarily, we propose a simplified but efficient multi-tier adaptive cell-coordination approach by combining features of joint transmission CoMP (JT-CoMP) and TD-eICIC to provide a pragmatic solution in the dynamically varying mobile environments. Finally, a hypothetical HetNet-CoMP paradigm is propounded that can effectually alleviate the interference in the backhaul-constrained densed fifth generation (5G) and beyond networks where multiple HetNet co-exist in the neighborhood. The analytical expressions and evaluation results validate the improvements achieved by the proposed methods in the network performance in terms of cell-edge user throughput and spectral efficiency performance metrics.

Improving the Performance of Cell-Edge Users in 6G and Beyond Networks by Utilizing a Novel Precoding-based Hybrid CoMP Transmission Design

The authors propose a novel hybrid coordinated multi-point (H-CoMP) design for cell-edge users in 6G networks to combat inter-cell interference (ICI), inter-user interference (IUI), and improve spectral efficiency via using a new, novel channel-based precoding-based approach.

Channel assignment and users mobility influence on primary users QoE in Cognitive Radio Network

Over the recent years, the fifth-generation (5G) of mobile communications, as projected for future requirements, has brought significant changes to our lives. This proliferation, in turn, has led to increasing demands in wireless technologies and developing expectations of wireless applications. As an immediate result, the current spectrum allocation, static allocation policy, has increased the resource demands. Subsequently, Cognitive Radio Network (CRN) has provisioned to resolve spectrum shortages in wireless networks. Additionally, due to a noticeable reduction in signal strength in cell-edges, Coordinated Multi-Point Joint Transmission (CoMP JT) has targeted the performance of cell-edge users. This paper proposes an adaptive data transmission method, namely Adaptive CoMP JT (ACJT), for mobile users in an interweave CRN under 5G technology. We have endeavored to maintain a satisfactory level of Quality of Experience (QoE) for Primary Users (PUs) in the device-to-device (D2D) communications. The ACJT is utilized to meet users’ requirements located in the boundary of cells. Moreover, resources are assigned to PUs based on services with distinct requirements. The evaluations of the proposed method on various circumstances confirm that the ACJT achieves affordable performance in terms of enhancing PUs’ QoE and energy consumption.

A cyclic frequency division non‐orthogonal multiple access system

SummaryIn this paper, we have developed a downlink power domain non‐orthogonal multiple access (NOMA) system based on cyclic frequency division, where interleaved frequency division multiple access (IFDMA) is cyclically combined with NOMA. The newly developed cyclic frequency division NOMA (CFD‐NOMA) system has the benefit of both NOMA and IFDMA. The concept of superposed multiuser principle for non‐orthogonal resource allocation is used in each NOMA cluster, and the users' data associated with different clusters are separated based on IFDMA. Extreme channel conditions are considered among the users in each cluster. Based on channel gain, the users are differentiated as strong and cell edge users. At the strong user terminal, successive interference cancelation (SIC) is applied to decode the strong user data with the aid of the cell edge user data found from a hard decision, whereas the cell edge user terminal detects its signal only through the hard decision. The near‐far effect of the users present in a cluster, the amount of difference among their channel gain, and transmission power play an important role in detecting the cell edge and the strong users. The CFD‐NOMA system inherits an effective use of multipath channel, thereby reaps an increased cell edge user performance in terms of bit error rate (BER).

Modeling and analysis of self-interference impaired two-user cooperative MIMO-NOMA system

In this work we deal with the performance analysis of a cell-edge user with the precoder and equalizer design in a two-user cooperative multiple-input multiple-output non-orthogonal multiple access (MIMO-NOMA) system. Since the data rate fairness and outage performance of cell-edge user are crucial issues in MIMO-NOMA systems, we emphasize on how to sort out these issues. To this end, the coefficients of power allocation are updated with the help of beamformers by utilizing the simultaneous wireless information and power transfer (SWIPT) protocol. Particularly, a user at the cell-center plays the role of a relay to help the cell-edge user and the relaying operation is powered by a hybrid time switching/power splitting SWIPT protocol. For this purpose, first we formulate the signal-to-interference-plus noise ratio of downlink MIMO-NOMA system by considering distinct correlation matrices in term of indefinite eigenvalues by utilizing a quadratic formulation in the presence of both self-interference and multi-user interference. Next, a closed-form expression of the outage probability is derived based on the knowledge of receive and transmit correlation matrices at the transmitter side. The analytical expressions are validated through simulations to affirm the accuracy of our analysis. We showcase the extent by which the cell-edge user’s outage performance is improved by using the antenna diversity at near and far end terminals of the MIMO-NOMA system.

Transmit and Receive Antenna Selection Based Resource Allocation for Self-Backhaul 5G Massive MIMO HetNets

With the advancement in wireless communication technology, the ease of accessibility and increasing coverage area is a major challenge for service providers. Network densification through Small cell Base Stations (SBS) integration in Heterogeneous Networks (HetNets) promises to improve network performance for cell edge users. Since providing wired backhaul for small cells is not cost effective or practical, the third-Generation Partnership Project (3GPP) has developed architecture for self-backhaul known as Integrated Access and Backhaul (IAB) for Fifth Generation (5G). This allows for Main Base Station (MBS) resources to be shared between SBS and MBS users. However, fair and efficient division of MBS resources remains a problem to be addressed. We develop a novel transmit antenna selection/partitioning technique for taking advantage of IAB 5G standard for Massive Multiple Input Multiple Output (MIMO) HetNets. Transmit antenna resources are divided among access for MBS users and for providing wireless backhaul for SBS. We develop A Genetic Algorithm (GA) based Transmit Antenna Selection (TAS) scheme and compare with random selection, eigenvalue-based selection and bandwidth portioning. Our analysis show that GA based TAS has the ability to converge to an optimum antenna subset providing better rate coverage. Furthermore, we also signify the performance of TAS based partitioning over bandwidth partitioning and also show user association can also be controlled using number of antennas reserved for access or backhaul.

On the Design of High Power Efficiency Uplink MIMO-NOMA Systems: A STBC and Joint Detection Perspective

The explosive growth of innovative applications imposes great challenges for future wireless communication systems with respect to ultra-high spectrum and power efficiency. Non-orthogonal multiple access (NOMA) and multiple-input-multiple-output (MIMO) have been acknowledged as two promising spectral-enhancing techniques to address the aforementioned issues. Orthogonal space-time block code (STBC), on the other hand, is capable of exploiting the full diversity gain of MIMO system. In this work, we explore how STBC can be utilized to enhance the performance of two-cell MIMO-NOMA networks. To this end, an uplink power minimization problem for the two-cell STBC-aided MIMO-NOMA system is investigated, wherein the joint detection technique is adopted to boost the cell-edge user's performance. The formulated optimization problem is non-convex and is intractable to be solved directly. A two-tier methodology is applied to decompose the original problem into two sub-problems, namely the beamforming design and the power allocation. Specifically, for the beamforming design, a closed-form expression is derived based on the Gram matrix of channel matrix. In the meanwhile, an efficient iterative method is developed to determine the power allocation coefficients for both the cell-center and the cell-edge users. Simulation results reveal that the proposed scheme outperforms several golden baselines in terms of total power consumption.

Performance of Multi-Cell mmWave NOMA Networks With Base Station Cooperation

Coordinated multipoint transmission is applied to multi-cell millimeter wave (mmWave) non-orthogonal multiple access (NOMA) networks in downlink transmission in this letter. Multiple cooperative base stations (BSs) jointly transmit same signal to a cell-edge user as a far user. And each BS individually serves a near user at the same beamwidth with NOMA. Subsequently, the outage probability, outage sum rate and energy efficiency are derived. Further, simulation results are provided to verify the correctness of analytical derivation and demonstrate the cell-edge user's performance improvement as well as the superiority of BS cooperation in multi-cell mmWave NOMA networks.

A Joint CoMP C-NOMA for Enhanced Cellular System Performance

The inter-cell interference (ICI) and the intra-user interference in non-orthogonal multiple access (NOMA) cellular networks have serious impacts on the performance of cell edge users. In this letter, we investigate the integration of coordinated multipoint (CoMP) transmission and cooperative NOMA (C-NOMA) aiming to improve the performance of cell edge users. Using this framework, we exploit the cooperation between base stations (BSs) to mitigate the ICI and the successive decoding of users that are near the BSs to further enhance the performance of cell edge users. In this setting, we derive a closed form expression for the outage probability of a cell edge user along with an analytical expression for its ergodic rate. We validate the derived expressions through various Monte-Carlo simulations, where we show the superiority of the proposed framework compared with other multiple access schemes proposed in the literature.

Downlink Radio Resource Management Through CoMP and Carrier Aggregation for LTE-Advanced Network

Long Term Evolution-Advanced (LTE-A) offers several new technologies to improve the performance of the user. However, poor received signal and interference from adjacent cells in the cell-edge area can reduce the efficiency of using individual technology. Therefore, the cell-edge users have lower throughput compared to the other users in the cell and LTE-A standard. An efficient downlink radio resource management scheme is proposed in this paper by combining the coordinated multipoint transmission and reception technique along with carrier aggregation technique to achieve higher throughput for the cell-edge user and better overall performance. The proposed method jointly transmits multiple component carriers to the cell-edge user from different cells to increase the bandwidth, strengthen the received signal, and reduce the interference while it satisfies several constraints. Modified largest weighted delay first packet scheduling algorithm is deployed for resource allocation, which takes into account the delay parameters, the probability of packet loss, and data rates of the user. The obtained system-level simulation results show that the proposed method significantly enhances the throughput performances, spectral efficiency, and fairness index, compared with the existing conventional methods.

Multicell MIMO Communications Relying on Intelligent Reflecting Surfaces

Intelligent reflecting surfaces (IRSs) constitute a disruptive wireless communication technique capable of creating a controllable propagation environment. In this paper, we propose to invoke an IRS at the cell boundary of multiple cells to assist the downlink transmission to cell-edge users, whilst mitigating the inter-cell interference, which is a crucial issue in multicell communication systems. We aim for maximizing the weighted sum rate (WSR) of all users through jointly optimizing the active precoding matrices at the base stations (BSs) and the phase shifts at the IRS subject to each BS’s power constraint and unit modulus constraint. Both the BSs and the users are equipped with multiple antennas, which enhances the spectral efficiency by exploiting the spatial multiplexing gain. Due to the non-convexity of the problem, we first reformulate it into an equivalent one, which is solved by using the block coordinate descent (BCD) algorithm, where the precoding matrices and phase shifts are alternately optimized. The optimal precoding matrices can be obtained in closed form, when fixing the phase shifts. A pair of efficient algorithms are proposed for solving the phase shift optimization problem, namely the Majorization-Minimization (MM) Algorithm and the Complex Circle Manifold (CCM) Method. Both algorithms are guaranteed to converge to at least locally optimal solutions. We also extend the proposed algorithms to the more general multiple-IRS and network MIMO scenarios. Finally, our simulation results confirm the advantages of introducing IRSs in enhancing the cell-edge user performance.

Improved resource allocation scheme for optimizing the performance of cell-edge users in LTE-A system

Improved resource allocation scheme for optimizing the performance of cell edge users in Long Term Evolution-Advanced (LTE-A) system is proposed in this paper. The proposed algorithm optimally assigns and allocates Carrier Components (CCs), Radio Blocks (RBs) and Modulation and Coding Scheme (MCS) index for the users based on the Quality of Service (QoS) provision to meet the on demand service requests. The proposed algorithm divides the cell regions into cell centre and cell edge depending on the traffic load on the network. The available RBs are allocated to meet the on demands requests of the users among these two regions. RB usage ratio for optimizing the performance of the scheduling algorithm is used during resource allocation. As the RB usage ratio reaches more than 70%, throughput and data rates of the cell may not be reached in timely and reliable manner. The proposed algorithm takes RB usage ratio into consideration during scheduling to maintain minimum QoS provisions of the users for resource allocation. Simulation result shows that, performance of the cell edge users optimally met with minimum throughput and data rates for reliable communication in the LTE-A system.

An Efficiency-Improved Clustering Algorithm Based on KNN Under Ultra-Dense Network

Ultra-Dense Network (UDN) is one of the key techniques for the next generation of mobile network due to providing high system throughput. However, severe interference often occurs in UDN, which greatly impact the data rates of cell-edge users. User-centric wireless access virtualization has been widely adopted in UDN to mitigate the interference of cell-edge users by sharing resources and eliminating cell boundary. However, it's only effective for moderate scale networks. Moreover, the efficiency needs further improvement. In this paper, we study effective cooperative clustering method for large scale UDN with less computations in order to improve the throughput of cell-edge users. We formulate a convex optimization problem in which the objective is to maximize the system throughput with overlapping virtual cells. We propose a clustering method to solve this optimization problem. We design a fast-convergent iterative algorithm called K-Nearest Neighbor (KNN) algorithm to perform users clustering. Simulation results show that our proposed algorithm has better throughput performance for both average and cell-edge users. Especially, the per-carrier throughput is improved, which leads to more serviceable users with limited resources.

Coverage Analysis of Integrated Sub-6GHz-mmWave Cellular Networks With Hotspots

Deploying Sub-6GHz networks together with millimeter wave (mmWave) is a promising solution to achieve high data rates in traffic hotspots while guaranteeing sufficient coverage, where mmWave small cells are densely deployed to provide high quality of service. In this paper, we propose an analytical framework to investigate the integrated Sub-6GHz-mmWave cellular networks, in which the Sub-6GHz base stations (BSs) are modeled as a Poisson point process, and the mmWave BSs are clustered following a Poisson cluster process in traffic hotspots. We conduct stochastic geometry-based analysis and derive the performance metrics including the association probability, signal-to-interference-plus-noise ratio coverage probability and average achievable rate, which are validated to be accurate by Monte Carlo simulations. We analyze the impact of various deployment parameters on the network performance to give insights on the network design. In particular, it is shown that deploying mmWave small cells in traffic hotspots will outperform both traditional Sub-6GHz heterogeneous network and isolated mmWave system in terms of the coverage probability. It can also be shown that extremely high and extremely small association weight for mmWave BSs will deteriorate the performance for cell edge users and cell interior users, respectively. Moreover, there exists an optimal pre-decided dispersion parameter of mmWave BSs that contributes to the maximum coverage probability.

Mutual Successive Interference Cancellation Strategies in NOMA for Enhancing the Spectral Efficiency of CoMP Systems

The densification of mobile networks should enable the fifth generation (5G) mobile networks to cope with the ever increasing demand for higher rate traffic, reduced latency, and improved reliability. The large scale deployment of small cells and distributed antenna systems in heterogeneous environments will require more elaborate interference mitigating techniques to increase spectral efficiency and to help unlock the expected performance leaps from the new network topologies. Coordinated multi-point (CoMP) is the most advanced framework for interference management enabling the cooperation between base stations to mitigate inter-cell interference and boost cell-edge user performance. In this paper, we study the combination of CoMP with mutual SIC, an interference cancellation technique based on power-domain non-orthogonal multiple access (NOMA) that enables multiplexed users to simultaneously cancel their corresponding interfering signals. A highly efficient inter-cell interference cancellation scheme is then devised, that can encompass several deployment configurations and coordination techniques. The obtained results prove the superiority of this approach compared to conventional NOMA-CoMP systems.

An Efficient Uplink Power Control Algorithm for LTE-Advanced Relay Networks to Improve Coverage Area

Power and spectrum are limited resource, so always we needed efficient control techniques to handle them in every generation. In this paper an efficient uplink power control algorithm is proposed for LTE-Advanced relay networks to improve coverage area. It is a co-operative power control method. It is developed using the utility function concept that belongs to economic theory. This algorithm is a distributed one, which is to be set up in mobile stations operating at 3GPP LTE or LTE-Advanced relay networks. In this the Lagrangian equation is used to solve the utility function to achieve optimal power control in the network. The outage probability analysis is carried out for the coverage area determination. It is observed that the proposed algorithm improves the cell edge user performance by maintaining the defined power levels in every mobile, improves the base station coverage area and decreases the interference level in the network.