Coordinated Multipoint Research Articles

Dynamic Set Planning for Coordinated Multi-Point in B4G/5G Networks.

Coordinated Multi-Point (CoMP) is an important technique in B4G/5G networks. With CoMP, multiple base stations can be clustered to compose a cooperating set to improve system throughput, especially for the users in cell edges. Existed studies have discussed how to mitigate overloading scenarios and enhance system throughput with CoMP statically. However, static cooperation fixes the set size and neglects the fast-changing of B4G/5G networks. Thus, this paper provides a full study of off-peak hours and overloading scenarios. During off-peak hours, we propose to reduce BSs’ transmission power and use the free radio resource to save energy while guaranteeing users’ QoS. In addition, if large-scale activities happen with crowds gathering or in peak hours, we dynamically compose the cooperating set based on instant traffic requests to adjust base stations’ BSs’ transmission power; thus, the system will efficiently offload the traffic to the member cells which have available radio resources in the cooperating set. Experimental results show that the proposed schemes enhance system throughput, radio resource utilization, and energy efficiency, compared to other existing schemes.

Coordinated Multipoint Transmission and Reception in Downlink and Uplink LTE Systems

Coordinated Multi-Point (CoMP) activity is considered as an amazing innovation focused for LTE-A standard to diminish obstruction, improve range effectiveness, increment information throughput and upgrade viable inclusion region, specifically for cell-edge clients. Interference is a major drawback in Long Term Evolution (LTE/LTE-Advanced) framework.The paper focuses the standardization and inspiration of explicit plan decisions for composed multipoint (CoMP) support in reasonable system executions, including Fundamental activity standards. There are a few strategies accessible for CoMP innovation where most methodologies require some planning data in regards to the UEs information at the distinctive BSs that must be mutual among them. This sharing outcomes expanded unpredictability and flagging overhead on arrange.

Mm‐Wave micro‐wave integrated Sub‐RAN for CRAN performance enhancement

Coordinated Multi-Point (CoMP) transmission in Cloud Radio Access Network (CRAN) requires a large amount of data transmission and processing within a coherence time window. Hence, CoMP transmission puts a lot of burden on the central processor and back-haul unit. Also, establishing CoMP for high-mobility users is challenging due to small coherence window and large beamforming overhead over mm-Wave transmission. This paper proposes a two-layer CRAN architecture with intelligent mm-Wave and micro-Wave allocation. A dual connectivity framework has been introduced to increase the coverage of high-mobility users. Further, it is shown that the proposed scenario reduces the load on the central processor and central back-haul. To avoid unnecessary handoffs, a mobility management algorithm is also proposed, which can provide seamless connectivity to the users irrespective of their velocity. Further, through simulation results, it is shown that the proposed network outperforms the existing CRAN framework.

Joint Optimization of BS Clustering and Power Control for NOMA-Enabled CoMP Transmission in Dense Cellular Networks

Non-orthogonal multiple access (NOMA)-enabled coordinated multipoint (CoMP) transmission has great potential in balancing spectrum utilization and interference mitigation in dense cellular networks. However, NOMA reforms the spectrum sharing policy of CoMP transmission due to introducing additional interference among coordinated base stations (BSs), which deteriorates the CoMP transmission rate. In this paper, we investigate the joint optimization of BS clustering and power control for NOMA-enabled CoMP transmission in dense cellular networks to maximize system sum-rate. We first characterize the impact of interference among coordinated BSs on CoMP transmission rate and find that the BS clustering is dependent on NOMA user grouping and restricted by the NOMA decoding condition. We then derive a tight lower bound on the system sum-rate and exploit it to design a joint BS clustering and power control scheme. Specifically, a power control algorithm is designed by a penalty convex-concave procedure to satisfy the NOMA decoding condition and users’ rate requirements. A BS clustering algorithm based on successive convex approximation is designed to iteratively update the BS clustering and NOMA user grouping to increase system sum-rate. Finally, two algorithms are alternately performed until all users successfully access and the system sum-rate converges. Simulation results show that the proposed scheme can efficiently alleviate interference among coordinated BSs to improve system sum-rate and spectrum efficiency of NOMA-enabled CoMP transmission even under high user density.

Multicast eMBB and Bursty URLLC Service Multiplexing in a CoMP-Enabled RAN

This paper is concerned with slicing a radio access network (RAN) for simultaneously serving two 5G-and-Beyond typical use cases, i.e., enhanced mobile broadband (eMBB) and ultra-reliable and low-latency communications (URLLC). Although many researches have been conducted to tackle this issue, few of them have considered the impact of bursty URLLC. The bursty characteristic of URLLC traffic may significantly increase the difficulty of RAN slicing in terms of ensuring an ultra-low packet blocking probability. To reduce the probability, we re-visit the structure of physical resource blocks orchestrated for URLLC traffic based on theoretical results. Meanwhile, we formulate the problem of slicing a RAN enabling coordinated multi-point (CoMP) transmissions for multicast eMBB and bursty URLLC service multiplexing as a multi-timescale optimization problem aiming at maximizing eMBB and URLLC slice utilities, subject to physical resource constraints. To mitigate this problem, we transform it into multiple single timescale problems by exploring sample average approximations. An iterative algorithm with provable performance guarantees is developed to obtain solutions to these single timescale problems and aggregate obtained solutions into those of the multi-timescale problem. We also design a CoMP-enabled RAN slicing system prototype and compare the iterative algorithm with the state-of-the-art algorithm to verify its effectiveness.

Generalized Coordinated Multipoint Framework for 5G and Beyond

The characteristic feature of 5G is the diversity of its services for different user needs. However, the requirements for these services are competing in nature, which impresses the necessity of a coordinated and flexible network architecture. Although coordinated multipoint (CoMP) systems were primarily proposed to improve the cell edge performance in 4G, their collaborative nature can be leveraged to support the diverse requirements and enabling technologies of 5G and beyond networks. To this end, we propose generalization of CoMP to a proactive and efficient resource utilization framework capable of supporting different user requirements such as reliability, latency, throughput, and security while considering network constraints. This article elaborates on the multiple aspects, inputs, and outputs of the generalized CoMP (GCoMP) framework. Apart from user requirements, the GCoMP decision mechanism also considers the CoMP scenario and network architecture to decide upon outputs such as CoMP technique or appropriate coordinating clusters. To enable easier understanding of the concept, popular use cases, such as vehicle-to-everything (V2X) communication and eHealth, are studied. Additionally, interesting challenges and open areas in GCoMP are discussed.

Joint Resource Allocation and UAV Scheduling With Ground Radio Station Sleeping

Applications of Unmanned aerial vehicles (UAVs) have advanced rapidly in recent years. The UAVs are used for a variety of applications, including surveillance, disaster management, precision agriculture, weather forecasting, etc. In near future, the growing number of UAV applications would necessitate densification of UAV infrastructure (ground radio station (GRS) and ground control station (GCS)) at the expense of increased energy consumption for UAV communications. Maximizing the energy efficiency of this UAV infrastructure is important. Motivated by this, we propose joint resource allocation and UAV scheduling with GRS sleeping. Further, we propose the use of coordinated multi-point (CoMP) with joint transmission (JT) and non-orthogonal multiple access (NOMA) along with GRS sleeping to increase the coverage and data rates, respectively. We then present exhaustive simulation results showcasing the trade-off between throughput and energy efficiency with varying UAV densities. We also compare the coverage, throughput, and energy efficiency for NOMA, CoMP with JT and the benchmark scenario.

A Stochastic Gradient Descent Approach for Hybrid mmWave Beamforming With Blockage and CSI-Error Robustness

In this study, we consider the downlink beamforming problem in millimeter wave (mmWave) systems subjected to both path blockages and imperfect channel state information (CSI), and propose a new robust hybrid sum-outage minimizing design as a solution. We first formulate the problem as an empirical risk minimization (ERM) stochastic learning problem, whose solution can be obtained by the alternate iteration of a baseband digital and a radio frequency (RF) analog Riemann manifold-constrained beamforming updates through a mini-batch stochastic gradient descent (MSGD) approach, with gradient minimizing update rules given in closed-form, and learning rates optimized based on the lower-bounds of the corresponding Lipschitz constants. Unlike existing solutions to the path blockage-robust mmWave beamforming problem, wherein out-of-band side information is required or perfect CSI is assumed, our method relies only on the estimates and statistical knowledge of the channel's angles of departure (AoD) and complex gains, which are simultaneously captured in a Bernoulli-Gaussian model and used to generate the training data for the MSGD-based optimizer. Further, unlike preceding fully-digital or fully-connected hybrid contributions, the proposed scheme assumes a virtually-configured partially-connected setup; therefore, it is compatible with coordinated multipoint (CoMP) architectures, which are known to be crucial in terms of exploiting the full potential of mmWave systems. Simulation results confirm the effectiveness of our MSGD-based robust hybrid CoMP mmWave beamformer in mitigating the effects of path blockage and CSI error, demonstrating its superiority to state-of-the-art (SotA) alternatives.

On Performance of Ultra-Dense Neighborhood Small Cell Networks in Urban Scenarios

The neighborhood small cell (NSC) network, which employs indoor small base stations (SBSs) to serve both indoor and outdoor users, is considered a cost-effective solution to address the increasing wireless traffic demand. In this letter, a novel evaluation scheme is proposed to predict the performance of a pure NSC network. A network model composed of indoor ultra-dense small cells (UDS) with coordinated multi-point (CoMP) transmissions is employed to address the maximum achievable performance gain in a given neighborhood. A closed-form analytical model is proposed to approximately compute the signal strength received by a specific outdoor user from the SBSs in a complex-shaped building and verified by the Monte Carlo simulations. The performance prediction of the ultra-dense NSC network is demonstrated in two practical urban scenarios. The proposed evaluation scheme facilitates the tractability of NSC network performance predictions in practical scenarios, which can be employed in future NSC embedded neighborhoods design.

A Dynamic 3-D Wideband GBSM for Cooperative Massive MIMO Channels in Intelligent High-Speed Railway Communication Systems

Coordinated multipoint (CoMP) and massive multiple-input multiple-output (mMIMO) are two of promising technologies in future intelligent high-speed railway (HSR) communication systems, whose performance is fundamentally determined by the characteristics of cooperative mMIMO channels. This article proposes a dynamic three-dimensional (3-D) wideband geometry-based stochastic model (GBSM) for HSR cooperative mMIMO channels. The proposed GBSM employs a sphere model and two elliptic-cylinder models to describe common and uncommon clusters for different links, and integrates the dynamic cluster evolution in both time and array domains. Statistical properties of the cooperative mMIMO model are investigated, such as multi-link spatial cross-correlation function and sum rate capacity. A corresponding dynamic 3-D wideband simulation model for the HSR cooperative mMIMO channel is also proposed. Finally, numerical results of the statistical properties are analyzed, and the proposed model is validated by realistic HSR channel measurement data, in terms of dual-link spatial cross-correlation and channel capacity. This model is more practical and will be helpful for facilitating the design and performance evaluation of future intelligent HSR communication systems.

Capacity Analysis of Coordinated Multipoint Reception for mmWave Uplink With Blockages

We consider an uplink coordinated multi-point (CoMP) transmission from a user served by multiple base stations (BSs) which are connected to each other via a central unit (CU). We model the millimeter-wave communication link with Nakahami- $m$ fading and random blockage. In this paper, we investigate the impact of blockage on the system ergodic capacity and try to find analytical formulation which can be useful in future optimization problems such as power control and resource allocations. The system performance is analyzed by deriving the probability density function of the received signal and finding closed form solution of ergodic capacity. Finally, the analytical results are compared with simulations and the impact of blockage is studied numerically. Numerical results show the efficiency of using CoMP in capacity improvement and reducing the blockage effect, as well as necessity of considering the blockage effect in performance analysis.

Quantized Massive MIMO Systems With Multicell Coordinated Beamforming and Power Control

In this paper, we investigate a coordinated multipoint (CoMP) beamforming and power control problem for base stations (BSs) with a massive number of antenna arrays under coarse quantization at low-resolution analog-to-digital converters (ADCs) and digital-to-analog converter (DACs). Unlike high-resolution ADC and DAC systems, non-negligible quantization noise that needs to be considered in CoMP design makes the problem more challenging. We first formulate total power minimization problems of both uplink (UL) and downlink (DL) systems subject to signal-to-interference-and-noise ratio (SINR) constraints. We then derive strong duality for the UL and DL problems under coarse quantization systems. Leveraging the duality, we propose a framework that is directed toward a twofold aim: to discover the optimal transmit powers in UL by developing iterative algorithm in a distributed manner and to obtain the optimal precoder in DL as a scaled instance of UL combiner. Under homogeneous transmit power and SINR constraints per cell, we further derive a deterministic solution for the UL CoMP problem by analyzing the lower bound of the SINR. Lastly, we extend the derived result to wideband orthogonal frequency-division multiplexing systems to optimize transmit power and beamformer for all subcarriers. Simulation results validate the theoretical results and proposed algorithms.

Energy-efficient relay selection and power allocation for multi-source multicast network-coded D2D communications

Device-to-device (D2D) communication improves spectrum efficiency (SE) and increases system capacity. Heterogeneous networks comprise macrocell and several small cells, such as picocells and femtocells, where femtocells are more efficient. In cooperative communications, one or several additional nodes help to send data from source to destination to improve the quality of service (QoS). Network coding (NC) in cooperative networks can extend data rate and coverage area of D2D communication. The purpose of this article is to minimize power consumption of transmitting nodes during network-coded cooperative D2D transmission to reduce the interference on co-channel transmissions. In this study, we consider cooperative multicast D2D communication with NC, where femtocell base stations (FBSs) are used as relay. We propose a method based on energy efficiency (EE) maximization for relay selection and power allocation for multi-source network-coded cooperative D2D communication in heterogeneous cellular networks. We present a solution to the proposed method and evaluate its performance. The results show that the introduced method significantly improves the SE and EE compared to the coordinated multi-point (CoMP) transmission, multi-source direct D2D communication (D-D2D), and other works.

Resource Allocation for CoMP Enabled URLLC in 5G C-RAN Architecture

Ultrareliable low-latency communication (URLLC) is one of the important service categories of 5G, where high reliability and low latency are to be met simultaneously. Coordinated multipoint (CoMP), where a user equipment (UE) is connected to multiple base stations simultaneously, can provide high reliability for interference limited cell-edge UEs. Short-packet communication and 5G physical layer enablers combined with CoMP can be a potential solution to meet the quality of service requirements of the URLLC traffic. However, there exist some challenges in using CoMP for URLLC in a cloud radio access network (C-RAN) architecture; mainly fronthaul capacity and remote radio head resource availability constraints. These resource constraints are addressed in this article; and a resource allocation scheme based on the effective bandwidth concept and 5G enablers is proposed, which can meet the reliability and delay requirements of the URLLC traffic. End-to-end error and latency components are identified and the interplay existing among the error components is utilized for bandwidth minimization. A novel packet delivery mechanism, queuing strategy, and time-frequency resource allocation for CoMP enabled URLLC in C-RAN architecture are proposed. The proposed scheme shows superior performance, in terms of the resource utilization and UE satisfaction, when compared with the existing techniques.

CoMP Transmission in Downlink NOMA-Based Heterogeneous Cloud Radio Access Networks

In this paper, we investigate the integration between the coordinated multipoint (CoMP) transmission and the non-orthogonal multiple access (NOMA) in downlink heterogeneous cloud radio access networks (H-CRANs). In H-CRAN, low-power high-density small remote radio heads (SRRHs) are underlaid by high-power low-density macro RRH (MRRH). However, co-channel deployment of the different RRHs gives rise to the problem of inter-cell interference that significantly affects system performance especially the cell-edge users. Thus, the users are first categorized into Non-CoMP users and CoMP users based on the relation between the useful signal to the dominant interference signal. The Non-CoMP user is the user equipment (UEs) having high signal-to-interference-plus-noise-ratio (INR) and hence associates with only one RRH. On the other hand, the CoMP user, cell-edge user, is the UE that experiences less distinctive received power with the best two RRHs. In the proposed CoMP-NOMA framework, each RRH schedules CoMP-UE and non-CoMP-UE over the same transmission channel using NOMA. We first design an analytical framework based on tools from the stochastic geometry to evaluate the performance of the proposed framework (CoMP-NOMA) which is based on H-CRAN in terms of the average achievable data rate for each NOMA UE. We then examine the spectral efficiency of the proposed CoMP-NOMA based H-CRAN. Simulation results are provided to validate the accuracy of the analytical models and to reveal the superiority of the proposed CoMP-NOMA framework compared with conventional CoMP orthogonal multiple access (CoMP-OMA) techniques. By reaping the benefits of both JT-CoMP and NOMA, we prove that the proposed framework can successfully deal with the inter-cell interference by using CoMP and improve the network's spectral efficiency through NOMA technique. We also show that, with an appropriate power allocation coefficient setting at the Non-CoMP-UEs, a fairness performance can be achieved between the CoMP-UEs and the Non-CoMP-UEs.

CoMP-Based Dynamic Handover for Vehicular VLC Networks

Visible light communication (VLC) has emerged as a potential wireless connectivity solution for infrastructure-to-vehicle networks where street lights can be configured to serve as access points. In this letter, we propose dynamic soft handover algorithm based on coordinated multipoint (CoMP) transmission. The proposed algorithm takes the rate of change in the received power as an input and accordingly revises the handover margin and time-to-trigger value without explicit information of the vehicle velocity. Our simulation results demonstrate that the proposed algorithm outperforms conventional CoMP and hard handover and maintains a stable signal quality regardless of vehicle velocity.

Stochastic Learning Robust Beamforming for Millimeter-Wave Systems With Path Blockage

We introduce a new robust, outage minimum, millimeter wave (mmWave) coordinated multipoint (CoMP) beamforming scheme to combat the random path blockages typical of mmWave systems. Unlike state-of-the-art methods, which are of limited applicability in practice due to their combinatorial nature which leads to prohibitive complexity, the proposed method is based on a stochastic-learning-approach, which learns crucial blockage patterns without resorting to the well-known worst-case optimization framework. Simulation results demonstrate the superior performance of the proposed method both in terms of outage probability and effective achievable rate.

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.

Movement Aware CoMP Handover in Heterogeneous Ultra-Dense Networks

The densification of base station (BS) deployments is driving the evolution of network structures towards heterogeneous ultra-dense networks (UDN), making coordinated multipoint (CoMP) a viable and promising transmission solution. However, the BS cooperation regions formed by applying CoMP in the UDN are small and irregular, which causes frequent handover for mobile users. Different from most existing work that focus on the trigger time of handover, we explore how to choose the appropriate BS cooperation set to reduce handover rate. In this paper, we consider movement aware CoMP handover (MACH). By estimating cell dwell time, a user would be intelligently assigned to macro cell or small cell according to its movement trend. To enhance reliability, we further proposed improved MACH (iMACH) to achieve a trade-off between BSs with long dwell time and the current best performed BS for multipoint cooperation while user moving. Using stochastic geometry method, expressions of coverage probability, handover probability and throughput that characterize performance of the proposed schemes are derived. The numerical results indicate that the theoretical analyses fit the simulation results well and the proposed schemes surpass the existing schemes in terms of the aforementioned metrics, and more intelligent and suitable for ultra-dense scenarios.

Cooperative resource management for C-V2I communications in a dense urban environment

Cellular-based vehicle-to-everything (C-V2X) is one of the emerging and promising techniques to support vehicular communications by enabling both safety-critical and non-safety services. C-V2X communications is a core solution to manage and advance future traffic safety and mobility. In this paper, we design a cellular-based vehicle-to-infrastructure (V2I) communications model for a Manhattan dense urban environment that has many roads deployed in the cell edge region, which results in severe co-channel interference (CCI). Thus, we aim to utilize two cooperative interference management schemes such as dynamic inter-cell interference coordination (ICIC) and coordinated multipoint (CoMP) to mitigate interference and to improve communication reliability. We evaluate the performance of the interference management schemes based on various performance indexes, such as vehicle UE average throughput, vehicle UE received interference, and vehicle UE outage probability. By effectively implementing the dynamic ICIC scheme, we achieve an immense reduction in CCI, which results in the improvement of user (UE) received signal quality. Moreover, we employ coordinated scheduling (CS) CoMP scheme to further mitigate the interference among cells. Finally, by implementing both dynamic ICIC and CS CoMP schemes simultaneously, a meaningful level of performance enhancement is achieved.