Next-generation Heterogeneous Networks Research Articles

Game theoretic model for power optimization in next-generation heterogeneous network

Game theoretic model for power optimization in next-generation heterogeneous network

Mode Selection and Resource Allocation for SWIPT NOMA based Three-tier HetNets

In next-generation heterogeneous networks, device-to-device communications are a key enabler to support a wider and diverse range of applications. They play an important role to guarantee the performance and quality of service requirements for the future ultra-dense networks. D2D-enabled cellular networks allow user equipment to communicate directly without any or with a partial association with macro base stations or with small base stations. In this paper, we propose a distance-based dynamic approach to minimize the interference and to guarantee QoS for diverse types of users equipment, such as macro user, small user and D2D user. The mode selection is used for minimize the interference and to guarantee QoS for both cellular and D2D communication links. Moreover, we investigated hybrid simultaneous wireless information and power transfer to achieve the higher data rates while guaranteeing the minimum harvested energy. Additionally, our scheme employs a transmit antenna selection criterion to exploit the spatial diversity gain of a multiple antennas for small base station. Results obtained show that coverage probability is improved in macro and small base stations links, when compared with traditional neighbor-based methods, we validate the theoretical findings and demonstrate that significant performance gain over orthogonal multiple access scheme in terms of spectral efficiency can be achieved by the proposed algorithms in a SWIPT-enabled NOMA system where we show the energy efficiency.

Effective Resource Allocation and Load Balancing in Hierarchical HetNets: Toward QoS-Aware Multi-Access Edge Computing

AbstractMobile edge computing (MEC) is a key feature of next-generation heterogeneous networks aimed at providing a variety of services for different applications by performing related processing tasks closer to the user equipment. In this research, we investigated on connection management approaches in multi-access edge computing systems. This paper presents joint radio resource allocation and MEC optimization in a multi-layer NOMA HetNet in order to maximize system’s energy efficiency. The continues carrier allocation and handoff decision variables, in addition to the interference incorporated in the goal function, modifies the primary optimization problem to a mixed integer nonlinear programming. Network selection is done statically based on the Analytic Hierarchy Process, and station selection is done dynamically based on the Data Envelope Analysis method. Also, an effective feedback mechanism has been designed in collaboration with the server resource manager to solve a global optimization problem in order to load balancing and meet the users quality of service constraints simultaneously. To reduce the computational complexity and to achieve a locally optimal solution, we applied variable relaxation and majorization minimization approach in which offloading decision and multi-part Markov noise analysis have been developed to model users’ preferences without the need for explicit information from the users. Based on the simulations, the proposed approach not only results in a significant increase of system’s energy efficiency but also enhances the system throughput in multiple-source scenarios.

Machine Intelligence Technique for Blockage Effects in Next-Generation Heterogeneous Networks

Machine Intelligence Technique for Blockage Effects in Next-Generation Heterogeneous Networks

Traffic-Aware Rate Adaptation for Improving Time-Varying QoE Factors in Mobile Video Streaming

Mobile video has become one of the most valuable services in next-generation heterogeneous networks, and users’ quality of experience (QoE) is recognized as its important performance metric. In this paper, we propose an adaptive bitrate (ABR) algorithm to achieve improvement of the timevarying QoE determinants during a mobile video playback. Since watching videos will bring mobile data charges to the users, the traffic consumed by video downloads should be customized to a user-specified amount. To this end, we first analyze the real-world traces, and find the key factors to formulate a continuous QoE model. Then, we introduce a traffic-aware rate adaptation strategy (TARA). Given that users are aware of their real-time capabilities when watching a mobile video, TARA enables robust ABR process which can satisfy users’ requirements with traffic constraints. Finally, a centralized reinforcement learning (RL) approach is proposed for the joint optimization of TARA, which aims to maximize the designed QoE metric, and deliver the expected viewing experience to users. Results of experiments driven by both the simulated, and real-world network traces reveal the efficiency of the proposed TARA strategy, and demonstrate its signicant performance improvement as compared to the state-of-the-art ABR algorithms.

Metasurface-enabled interference mitigation in visible light communication architectures

Light can be used for wireless information transmission apart from illumination; that is the key idea behind visible-light communication (VLC), one of the disruptive technologies of our days. It combines remarkably high data rates due to ultrashort wavelengths with huge reliability and security due to small distances; nevertheless, it substantially suffers from interference of neighboring light sources in multiple-link configurations. In this manuscript, we investigate a pair of light emitting diodes interfering each other and propose a simple nanoslit metasurface that radically increases the directivity of the transmitting beams. As a result, enhancement of the signal-to-interference ratio by several orders of magnitude is reported. The considered generic setup retains its beneficial features in the presence of realistic design defects and, accordingly, may inspire standardization efforts towards the adoption of VLC in next-generation heterogeneous communication networks.

Spectral Efficiency and Deployment Cost Efficiency Analysis of mmW/UHF-Based Cellular Network

Next-generation heterogeneous cellular network (HCN) expects more and more deployment of the base stations and spectrum to achieve data rate in gigabits per second with seamless connectivity. Recently, small cell deployment has proven its effectiveness for increasing the coverage and area spectral efficiency (ASE) of the cellular network. Although, dense small cell deployment also increases the deployment cost and cross-tier interference of the network. This paper suggests switching-based mixed millimeter wave (mmW)/ultra high frequency (UHF) cellular network as a possible solution to overcome these challenges. In mixed mmW/UHF cellular network (named as MMUCN), mmW is used as the main transmission link, and UHF band is utilized as a backup link. In this paper, a theoretical framework is developed using tools from the stochastic geometry to analyze the outage performance, ASE, and deployment cost efficiency (DCE) of the MMUCN, which comprises existing macro base stations and mmW base stations. Optimal mmW base station densities constraints by the outage are calculated, which maximizes the ASE and DCE. Furthermore, a multiobjective optimization problem is formulated to maximize ASE and DCE simultaneously. Numerical results show that MMUCN outperforms UHF-based two-tier cellular network and efficiently mitigates the cross-tier interference of the system.

A New Fuzzy-TOPSIS based Algorithm for Network Selection in Next-Generation Heterogeneous Networks

A New Fuzzy-TOPSIS based Algorithm for Network Selection in Next-Generation Heterogeneous Networks

Bidirectional carrier aggregation in next-generation radio-over-fiber heterogeneous network based on FBMC

We have projected and verified a bidirectional intra-/inter-radio-access-technology carrier-aggregation method for a next-generation heterogeneous mobile network supported by filter bank multicarrier (FBMC). Successful transmission of intra/inter-band carrier aggregation between five broadband FBMC signals and three bands 4G long-term-evolution-advanced signal over 50 km single-mode fiber plus 10 m free-space is successfully broadcasted by employing an incoherent light-injection scheme in downlink. In uplink, two intra-bands carrier-aggregated wireless local area network Institute of Electrical and Electronics Engineers 802.11g signal is carried over the equal distance. High receiver sensitivity, low error vector magnitude, and clear constellation diagrams show successful delivery of different wireless services for different consumers. Therefore, the proposed hybrid system should become a potential solution for a future mobile front-haul network because of its low latency and high capacity.

The SMART Handoff Policy for Millimeter Wave Heterogeneous Cellular Networks

The millimeter wave (mmWave) radio band is promising for the next-generation heterogeneous cellular networks (HetNets) due to its large bandwidth available for meeting the increasing demand of mobile traffic. However, the unique propagation characteristics at mmWave band cause huge redundant handoffs in mmWave HetNets that brings heavy signaling overhead, low energy efficiency and increased user equipment (UE) outage probability if conventional Reference Signal Received Power (RSRP) based handoff mechanism is used. In this paper, we propose a reinforcement learning based handoff policy named SMART to reduce the number of handoffs while maintaining user Quality of Service (QoS) requirements in mmWave HetNets. In SMART, we determine handoff trigger conditions by taking into account both mmWave channel characteristics and QoS requirements of UEs. Furthermore, we propose reinforcement-learning based BS selection algorithms for different UE densities. Numerical results show that in typical scenarios, SMART can significantly reduce the number of handoffs when compared with traditional handoff policies without learning.

Optimization of Visible-Light Optical Wireless Systems: Network-Centric Versus User-Centric Designs

In order to counteract the explosive escalation of wireless tele-traffic, the communication spectrum has been gradually expanded from the conventional radio frequency (RF) band to the optical wireless (OW) domain. By integrating the classic RF band relying on diverse radio techniques and optical bands, the next-generation heterogeneous networks (HetNets) are expected to offer a potential solution for supporting the ever-increasing wireless tele-traffic. Owing to its abundant unlicensed spectral resources, visible light communications (VLC) combined with advanced illumination constitute a competent candidate for complementing the existing RF networks. Although the advantages of VLC are multi-fold, some challenges arise when incorporating VLC into the classic RF HetNet environments, which may require new system architectures. The user-centric (UC) design principle for VLC environments constitutes a novel and competitive design paradigm for the super dense multi-tier cell combinations of HetNets. The UC concept may be expected to become one of the disruptive techniques to be used in the forthcoming fifth-generation era. This paper provides a comprehensive survey of visible-light-aided OW systems with special emphasis on the design and optimization of VLC networks, where the radically new UC design philosophy is reviewed. Finally, design guidelines are provided for VLC systems.

GT-QoSec: A Game-Theoretic Joint Optimization of QoS and Security for Differentiated Services in Next Generation Heterogeneous Networks

Recently, numerous real-time, data-rich, and differentiated applications and services have appeared in the next-generation Heterogeneous Networks. As a result, the number of potentially “untrusted” connections to the mobile operator’s core network is expected to dramatically increase. Therefore, the operators must provide adequate security, without significantly affecting the quality of service (QoS). Hence, joint consideration of QoS and security is a critical research issue. However, due to their difficult-to-model conflicting objectives, existing research works have often dealt with them separately. In this paper, we address this problem, formally formulate it, and envision GT-QoSec, a game-theoretic joint optimization of QoS and security. Using GT-QoSec, the mobile user equipment (UE) and their servicing base stations (eNBs) play games with each other. Thus, the UE obtains a balanced set of QoS and security levels while the eNBs maximize their bandwidth utilization. Extensive analysis and simulation results are presented to evaluate the performance of GT-QoSec in contrast with several conventional methods.

A study on cell association in heterogeneous networks with joint load balancing and interference management

Exponential growth in the demand for network capacity has led to extensive research on advanced cellular network technology. A heterogeneous network in which traditional well-planned macro cell deployment is overlaid by small-scale unplanned base stations is one effective solution for next-generation networks. However, the cell association techniques currently used in macro-only cellular networks are not suitable for next-generation heterogeneous networks. Finding effective methods to handle the cell association problem in this new type of network is a hot topic of research in this field. This paper provides an overview of the cell association problem in heterogeneous networks and discusses the main issues that need to be addressed by an efficient cell association technique in order to maximize the network throughput. It has been shown that an efficient cell association scheme in heterogeneous networks must balance the load among different cells while minimizing the inter-cell interference at the same time. Jointly considering these two objectives is a challenge currently being investigated by researchers. An overview on load balancing and interference management in heterogeneous networks is provided in this paper. A review of the existing literature shows that there is a need for an efficient distributed solution in which load balancing approaches are observed and at the same time users prone to harmful interference are protected. A framework for modeling the heterogeneity of this type of network is presented, a simulation is performed in order to verify the effects of different parameters, and, finally, the problem is formulated. Future research directions are also provided in the paper.

Analog Spatial Cancellation for Tackling the Near-Far Problem in Wirelessly Powered Communications

The implementation of wireless power transfer in wireless communication systems opens up a new research area, known as wirelessly powered communications (WPC). In next-generation heterogeneous networks where ultradense small-cell base stations are deployed, simultaneous-wireless-information-and-power-transfer (SWIPT) is feasible over short ranges. One challenge for designing a WPC system is the severe near-far problem where a user attempts to decode an information-transfer (IT) signal in the presence of extremely strong SWIPT signals. Jointly quantizing the mixed signals causes the IT signal to be completely corrupted by quantization noise, and thus the SWIPT signals have to be suppressed in the analog domain. This motivates the design of a framework in this paper for analog spatial cancellation in a multiantenna WPC system. In the framework, an analog circuit consisting of simple phase shifters and adders is adapted to cancel the SWIPT signals by multiplying it with a cancellation matrix having unit-modulus elements and full rank, where the full rank retains the spatial-multiplexing gain of the IT channel. The unit-modulus constraints render the conventional zero-forcing method unsuitable. Therefore, this paper presents a novel systematic approach for constructing cancellation matrices. For the single-SWIPT-interferer case, the matrices are obtained as truncated Fourier/Hadamard matrices after compensating for propagation phase shifts over the SWIPT channel. For the more challenging multiple-SWIPT-interferer case, it is proposed that each row of the cancellation matrix is constructed as a Kronecker product of component vectors, with each component vectors designed to null the signal from a corresponding SWIPT interferer similarly as in the preceding case.

Energy-Efficient and QoE-Aware TV Broadcast in Next-Generation Heterogeneous Networks

Future networks will comprise a large number of inter-connected heterogeneous devices that will receive ubiquitous multimedia services over integrated but diverse wireless network technologies. In this context, optimization of multimedia broadcast transmissions based on network resources and user-end constraints (price sensitivity, device display, and limited battery) is essential to ensure high QoE. This article discusses underlying challenges, and suggests hybrid system architecture and potential cross-layer adaptive unified solutions for energy-efficient and QoE-aware digital television broadcast services in future heterogeneous network environments. Experimental and architecture-level simulation studies of the cross-layer adaptive strategies demonstrate an increase in user equipment energy saving, QoE, and number of multimedia broadcast/multicast users being served.

Users First: User-Centric Cluster Formation for Interference-Mitigation in Visible-Light Networks

Visible light communication (VLC) combined with advanced illumination may be expected to become an integral part of next-generation heterogeneous networks. In order to mitigate the performance degradation imposed by the intercell-interference (ICI), a user-centric (UC) cluster formation technique employing vectored transmission (VT) is proposed for the VLC down-link system, where multiple users may be simultaneously supported by multiple access points (APs). In contrast to the traditional network-centric (NC) design, the UC-VT cluster formation is dynamically constructed and adjusted, rather than remaining static. Furthermore, we consider the critical issue of multiuser scheduling (MUS) relying on maximizing the “sum utility” of this system, which leads to a joint cluster formation and MUS problem. In order to find a practical solution, the original problem is reformulated as a maximum weighted matching (MWM) problem relying on a user-AP distance-based weight and then a low-complexity greedy algorithm is proposed, which offers a suboptimal yet compelling solution operating close to the optimal value found by the potentially excessive-complexity exhaustive search. Our simulation results demonstrate that the proposed greedy MUS algorithm combined with the UC-VT cluster formation is capable of providing an average user throughput of about 90% of the optimal throughput, which is about three times the throughput provided by the traditional cellular design in some of the scenarios considered.

Cloudification of mmwave-based and packet-based fronthaul for future heterogeneous mobile networks

Current deployments of mobile networks are seriously challenged by increasing capacity demands, and traditional solutions are no longer practical. The use of small cells is considered as a viable technique to meet these demands. In this context, the use of centralized signal processing in a pool is seen as an enabler for next-generation heterogeneous mobile networks. This allows for simpler base stations and savings in deployment costs, but introduces challenges in the fronthaul network connecting the sites to the processing pool. The fronthaul needs to have very low latency and high capacity, but the traditional architecture of this network uses point-to-point links between each site and the pool, thus making it impossible to share capacity as the demands change. To address these challenges, a flexible network architecture for the fronthaul is presented that is based on Ethernet to carry the baseband samples. This architecture is integrated with baseband over millimeter waves for the fronthaul toward the small cells to save in fiber deployment and cope with the spectrum shortage in the traditional microwave frequencies. Simulation results show that few hundreds of microseconds of latency in the fronthaul can be tolerated for the applications running in the user equipment to respond within acceptable times. Furthermore, our estimations show that the use of millimeter waves allows an 11 percent reduction in the number of cells needed for the same traffic volume.

Ad hoc cooperative vertical handover for next-generation heterogeneous networks

We propose a new vertical handover scheme that uses cooperative ad hoc nodes, instead of interworking via backhaul, for the fast handover of mobile nodes (MN) in next-generation heterogeneous network environments. An MN requiring a vertical handover requests an adjacent ad hoc node to undertake some of the handover procedures that require latency, such as authentication and registration procedures, and to process them in place of the requested MN before the handover completion. A vertical handover procedure that uses this takeover technique is described in detail and its performance is analyzed by investigating the success probability of takeover. The results confirm that the proposed vertical handover scheme using takeover reduces both connection disruption time and packet loss compared with conventional vertical handover schemes without takeover.

Adaptive Threshold and Hysteresis for Handoff Initiation in Next Generation Networks from Path Loss Model

Mobility management is evolving as the most astounding area of research for the upcoming researchers. Many issues such as signalling overhead, latency, low bandwidth, low reliability, etc., existed in traditional mobility schemes in wireless networks. But the next-generation heterogeneous networks have resolved many issues and researchers are looking forward to take best use of upcoming generations to provide constant connectivity. In this paper, a fuzzy logic-based adaptive threshold and adaptive hysteresis handoff initialisation algorithm is proposed. It uses data rate, received signal strength indicator and SINR to determine the value of threshold and hysteresis. This algorithm makes use of Okumura Hata Path loss model to determine the value of RSSI, which is then given to fuzzy inference engine. It has been shown that threshold and hysteresis are not only dependent on RSSI but also on many other parameters such as on transmitter height, receiver height and antenna gain, frequency and cable loss.

Non-data-aided joint bit-rate and modulation format identification for next-generation heterogeneous optical networks

A novel and cost-effective technique for simultaneous bit-rate and modulation format identification (BR-MFI) in next-generation heterogeneous optical networks is proposed. This technique utilizes an artificial neural network (ANN) in conjunction with asynchronous delay-tap plots (ADTPs) to enable low-cost joint BR-MFI at the receivers as well as at the intermediate network nodes without requiring any prior information from the transmitters. The results of numerical simulations demonstrate successful identification of several commonly-used bit-rates and modulation formats with estimation accuracies in excess of 99.7%. The effectiveness of proposed technique under different channel conditions i.e. optical signal-to-noise ratio (OSNR) in the range of 14–28dB, chromatic dispersion (CD) in the range of −500 to 500ps/nm and differential group delay (DGD) in the range of 0–10ps, is investigated and it has been shown that the proposed technique is robust against all these impairments.