HetNet Environment Research Articles

Power control in LTE based on heuristic game theory for interference management

In the conventional LTE homogeneous network, sufficient transmit power of user equipment (UE) is determined by open-loop power control (OL-PC) and closed-loop power control (CL-PC) schemes. However, in a Het-Net environment, setting the UE’s transmit power requires delicate responsiveness to handle the severe and complicated uplink interference. In this paper, an interference-aware uplink power control mechanism based on Heuristic game theory approach is proposed for devices coexisting in a heterogeneous wireless network. Various wireless constraints like channel response, path loss, fading, shadowing, interference and metrics like SNR, SINR, throughput and bit rates are considered. Uplink power is controlled by suitably selecting the penalization factor (β) based on a simple Heuristic game theory approach considering the possible wireless constraints of each user depending on its location in the cell under consideration. The algorithm is framed in such a way to reduce inter-cell interference, limit transmit power, enhance bit rates and throughput of users. A significant improvement of 5.2% in the user coverage/distribution is achieved as a result of interference management compared to conventional power control scheme and power control with convex pricing.

Hybrid Deep Learning Approach for 6G MIMO Channel Estimation and Interference Alignment HetNet Environments

Hybrid Deep Learning Approach for 6G MIMO Channel Estimation and Interference Alignment HetNet Environments

Cooperative Game-Based Resource Allocation Scheme for Heterogeneous Networks with eICIC Technology

Heterogeneous network (HetNet) is considered to be the most promising approach for increasing communication capacity. However, HetNet control problems are difficult due to their intertier interference. Recently, the enhanced intercell interference coordination (eICIC) technology is introduced to offer several benefits, including a more equitable traffic load distribution across the macro and embedded small cells. In this paper, we design a new resource allocation scheme for the eICIC-based HetNet. Our proposed scheme is formulated as a joint cooperative game to handle conflicting requirements. By adopting the ideas of Kalai and Smorodinsky solution (KSS), multicriteria Kalai and Smorodinsky solution (MCKSS), and sequential Raiffa solution (SRS), we develop a hybrid control algorithm for an adaptive resource sharing between different base stations. To effectively adjust the eICIC fraction rates, the concepts of MCKSS and SRS are applied in an interactive manner. For mobile devices in the HetNet, the assigned resource is distributed by using the idea of KSS. The key insight of our algorithm is to translate the originally competitive problem into a hierarchical cooperative problem to reach a socially optimal outcome. The main novelty of our approach is its flexibility to reach a reciprocal consensus under dynamic HetNet environments. Exhaustive system simulations illustrate the performance gains along different dimensions, such as system throughput, device payoff, and fairness among devices. The superiority of our proposed scheme is fully demonstrated in comparison with three other existing eICIC control protocols.

Mitigating Jamming Attack in 5G Heterogeneous Networks: A Federated Deep Reinforcement Learning Approach

Jamming attack is one of the serious security breaches in the upcoming fifth-generation heterogeneous networks (5G HetNets). Most of the existing anti-jamming techniques, such as frequency hopping (FH) and direct sequence spread spectrum (DSSS) lack in self-adaptive capabilities to mitigate the security and privacy issues in highly dynamic 5G HetNet environment. In literature, although reinforcement learning (RL) has been explored a lot in designing various anti-jamming techniques to address the aforementioned problems, but these techniques suffer from the issue of large network resource consumption and slow convergence rate. To mitigate these issues, we propose a federated deep reinforcement learning (DRL) based anti-jamming technique for two-tier 5G HetNets. In the proposal, each femtocell of 5G HetNets is assumed to have multiple single antenna femto users (FUs) and a multi-antenna jammer used to jam the downlink signals from femto base station (FBS) to FUs. Aiming to improve the achievable rate at FUs in the presence of jammers, a joint optimization problem of beamforming and power allocation at FBSs is formulated by considering the quality-of-service (QoS) requirements of FUs. Due to the non-convex nature of the aforementioned optimization problem, we have used the Markov decision process (MDP) to transform the optimization problem into a multi-agent reinforcement learning (MARL) problem. Then, to solve this MDP with large number of states and action spaces, a federated deep reinforcement learning (DRL) scheme is proposed to maximize the achievable rate at FUs. The proposed scheme uses federated learning and dueling architecture of dueling double deep Q network (D3QN) to optimize the beamforming vectors and power allocation jointly at FBSs. The achievable rate performance of the proposed federated DRL scheme is compared with double deep Q network (DDQN) and deep Q network (DQN). Simulation results show that the proposed federated DRL scheme achieves 19.39% and 23.85% better achievable rate in comparison to DDQN and DQN schemes.

SecBoost: Secrecy-Aware Deep Reinforcement Learning Based Energy-Efficient Scheme for 5G HetNets

In this paper, we propose a secrecy-aware energy-efficient scheme for a two-tier heterogeneous network (HetNet), consisting of a sub-6 GHz macrocell and multiple millimeter wave (mmWave) picocells. Each picocell is assumed to have several users and an eavesdropper (Eve) which intercepts the signal of the picocell users. In the proposed scheme, firstly, to maximize the secrecy energy-efficiency (SEE) of picocell users, a joint optimization problem of power control, channel allocation, and beamforming is formulated by considering the minimum secrecy rate and signal-to-interference-plus-noise ratio (SINR) constraints. Due to the non-convex nature of the aforementioned optimization problem in a highly dynamic HetNet environment, we transform it into a reinforcement learning (RL) problem using the Markov decision process (MDP). Then, a multi-agent reinforcement learning (MARL) technique is used to obtain the maximum long-term reward. Moreover, we propose a multi-agent cooperative deep reinforcement learning (DRL) scheme known as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SecBoost</i> to solve the MDP with large number of action and state spaces. It uses the dueling and double-Q architecture of dueling double deep Q-network (D3QN) to optimize power control, channel allocation, and beamforming vectors to maximize the SEE of picocells. Also, prioritized experience replay is used to increase the sampling efficiency of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SecBoost</i> . The SEE performance of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SecBoost</i> is compared with MARL, multi-agent deep Q-network (MA-DQN), state-of-the-art joint beamforming based secrecy energy efficiency maximization (JBF-SEEM) scheme, and one-time pad based encrypted data transmission (O-EDT). Simulation results demonstrated that the proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SecBoost</i> scheme achieves 14.7%, 8.33%, 30%, and 69% better average SEE in comparison to MARL, MA-DQN, JBF-SEEM, and O-EDT schemes, respectively, which reveals its effectiveness in improving SEE of picocells.

Combined Resource Allocation for Fronthaul and Backhaul to Improve Throughput and Fairness in HetNet Environment

Combined Resource Allocation for Fronthaul and Backhaul to Improve Throughput and Fairness in HetNet Environment

Analysis of Acquired Indoor LTE-A Data from an Actual HetNet Cellular Deployment

Increasing the user downlink throughput is always a task of utmost importance for any cellular network service provider. However, most of the research is only focused on system simulations due to environmental simplicity. In this paper, instead of focusing on theoretical simulations, we aim to find the best practical solution to increase user throughput in an actual HetNet deployment where many small cells are deployed inside a building. An inter-frequency deployment is implemented in the actual LTE-A HetNet environment. A series of data collections were conducted in an actual indoor LTE-Advanced HetNet (heterogeneous network) environment with optimization strategies such as ABS (Almost Blank Subframe) and turning off/on interfering antennas. Detailed findings and analysis are provided to better understand the complicated actual HetNet environment. This work is also important to understand the future 5G network since the small cells and HetNet will continue to play an important role in the 5G network.

Heterogeneous Network Bandwidth Control Scheme for the Hybrid OMA-NOMA System Platform

The emerging non-orthogonal multiple access (NOMA) has been considered as a promising technology to reach the goals of 5G cellular systems. Due to its superior spectral efficiency, the NOMA has attracted a lot of attention recently, and could play a vital role in improving the capacity of future Heterogeneous networks (HetNets). In this paper, we present a joint bandwidth control scheme, which incorporates both NOMA and orthogonal multiple access (OMA) modes into one unified scheme. For the effective collaboration of different multiple access methods, we adopt the ideas of cooperative bargaining solution concepts. In the proposed scheme, the bandwidth allocation process for base stations and channels follows the OMA mode, and mobile devices within a same channel form a group. The power level selection process for mobile devices in each group follows the NOMA mode. In the OMA mode, traditional Nash bargaining solution is adopted to allocate bandwidth resources. In the NOMA mode, groups of individual devices bargain both within and across groups based on the group bargaining solution. Under the dynamic changing HetNet environments, our joint bargaining approach takes various benefits in a rational way while maximizing the bandwidth efficiency. Comprehensive numerical experiments are provided to show that the performance of our proposed scheme is superior to existing HetNet spectrum control protocols.

Online Distributed User Association for Heterogeneous Radio Access Network.

Future-generation radio access networks (RAN) are projected to fulfill the diverse requirements of user equipment (UE) by adopting a heterogeneous network (HetNet) environment. Necessary integration of different radio access technologies (RAT), such as 2G, 3G, 4G, wireless local area network (WLAN), and visible light communication (VLC) is inevitable. Moreover, UEs equipped with diverse requirements will be capable of accessing some or all the RATs. The complex HetNet environment with diverse requirements of UEs will present many challenges. The HetNet is likely to suffer severely from load imbalance among the base stations (BSs) from inheriting the traditional user association scheme such as max-SINR (signal-to-interference-plus-noise ratio)/max-RSSI (received signal strength indicator), unless some sophisticated schemes are invented. In this paper, a novel scheme is devised for a joint-user association for load balancing, where BSs are densely deployed and UEs typically have a certain degree of mobility. Unlike most of the present works, a dynamic network is considered where the position and channel condition of the UEs are not fixed. We develop two complex and distributed association schemes based on probability and d-choices, while carefully considering both loads of the BSs and SINR experienced by the UEs. Numerical results validate the efficiency of the proposed schemes by showing a received data-rate fairness among UEs and an improvement in the UE’s minimum received data rate.

Interdependency Analysis of Inter-Site-Distance on Configuration of Handover Control Parameter in LTE-A HetNets

Handover (HO) is the procedure performed to maintain the ongoing session of mobile User Equipment (UE). In Long Term Evolution-Advanced (LTE-A) network, the UE-assisted, network controlled hard HO procedure is suggested by 3GPP. The adoption of the traditional HO mechanism in Heterogeneous Network (HetNet) concept of LTE-A imposes several challenges such as increase in frequent and unnecessary handover rate. This leads to complexity in network planning and maintenance resulting in inefficient resource utilization. Further, the increase in radio link and HO failures are caused due to high-speed UEs. To overcome these challenges, the HO control parameters such as Hysteresis Margin, Cell Specific Offsets, Frequency-Specific Offsets, A3offset and Time-To-Trigger need to be properly configured in consideration with environmental, network and UE characteristics. Hence in this research, an attempt has been made to investigate the impact of these control parameters on HO performance in HetNet environment. Three types of analysis that includes (1) the impact of Inter-Site-Distance, (2) the impact of offloading and (3) the impact of velocity are carried out. The HO performance in terms of HO success rate has been analyzed for Macro---Pico and Pico---Macro scenarios. The results have confirmed that the considered control parameters have a high impact on HO performance.

On Downlink NOMA in Heterogeneous Networks With Non-Uniform Small Cell Deployment

Compared to orthogonal multiple access (OMA), non-orthogonal multiple access (NOMA) can achieve higher spectral efficiency by exploiting the power domain multiplexing. In this paper, we investigate the performance of NOMA in a two-tier heterogeneous network (HetNet) with non-uniform small cell deployment, where critical performance metrics like coverage probability and achievable rate are analyzed. First, a NOMA-based HetNet model is established, where users are paired based on the proposed user pairing scheme. Then the distribution of the order statistics for the distances between different NOMA users and the serving base station (BS) is presented considering the channel qualities from the NOMA users to the BSs. On this basis, we analytically demonstrate the impact of various network parameters on the coverage probability and achievable rate of NOMA users, such as signal-to-interference-plus-noise ratio threshold and BS density. Furthermore, an analysis is presented to provide insight into the energy efficiency of the considered system. Finally, extensive simulation and comparisons are conducted, which validate the advantages of NOMA over OMA in the considered HetNet environment.

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.

Comparison of Performance of Packet Scheduling Algorithms in LTE-A HetNets

The concept of usage of heterogeneous networks (HetNets) is about improving the LTE system performance by increasing the capacity and coverage of the Macro cell. In this paper, a performance comparison of various packet scheduling algorithms such as Proportional Fair, Maximum Largest Weighted Delay First and Exponential/Proportional Fair is studied in detail in the HetNets environment. The key performance indicators such as throughput, packet loss ratio, delay and fairness are considered to judge the performance of the scheduling algorithms. Various strategies such as increasing the number of Pico cells in the cell edge were used in the simulation for the performance evaluation study. The results achieved through various simulations show that adding Pico cells to the existing Macros enhances the overall system performance in addition to the various scheduling algorithms implemented in Macros. For reader’s convenience, various types of graphs have been used to represent the simulation results to better understand the performance metrics of various scheduling algorithms. Simulation results shows that overall system gain has increased because of adding Picos and thereby providing better coverage in the cell edge areas and thereby increasing the capacity of the network to provide better quality of service.

Interference-Aware Uplink Power Control in 3GPP LTE-A HetNet

The latest evolution of cellular network, i.e., the heterogeneous network (HetNet) is a promising technique for facing the explosive data demands that the macro-only network can barely meet. However, unplanned small cell deployments, along with an aggressive frequency reuse scheme, generate severe interference between adjacent cells, degrading system performance. In the conventional homogeneous network, fractional power control (FPC), which consists of open-loop power control (OL-PC) and closed-loop power control (CL-PC), is used to determine adequate transmit power of user equipment (UE) to avoid inter-cell interference. However, setting the UE transmit power requires delicate awareness of uplink interference to properly avoid the severe and complicated inter-cell interference in an uplink HetNet environment. In this paper, we propose an interference-aware uplink power control scheme that considers outgoing and incoming interference in each cell in order to fully take the interference situation of the HetNet into account while setting the OL-PC parameter. By using the proposed scheme, uplink interference existing in a HetNet environment can evidently be reduced; therefore, the total cell capacity of both the macro- and the femtocell is increased by 25.6 %. Furthermore, the simulation results of a CL-PC on a 10 ms basis show that the received signal to interference-plus-noise ratio (SINR) of OL-PC with CL-PC is spread less around the target SINR compared to the case of OL-PC alone. Therefore, it is verified that the CL-PC supports the received SINR of OL-PC to meet the target SINR by compensating the channel variation caused by the fading effect.

Low-complexity distributed algorithms for uplink CoMP in heterogeneous LTE networks

Coordinated multi-point transmission (CoMP) techniques are being touted as enabling technologies for interference mitigation in next generation heterogeneous wireless networks (HetNets). In this paper, we present a comparative performance study of uplink (UL) CoMP algorithms for the 3GPP LTE HetNets. Focusing on a distributed and functionally-split architecture, we consider six distinct UL-CoMP algorithms: 1. Joint reception in the frequency-domain (JRFD) 2. Two-stage equalization (TSEQ) 3. Log-likelihood ratio exchange (LLR-E) 4. Symmetric TSEQ (S-TSEQ) 5. Transport block selection diversity (TBSD) 6. Coordinated scheduling with adaptive interference mitigation (CS-AIM) where JRFD, TSEQ, S-TSEQ, TBSD and CS-AIM are our main contributions in this paper, and quantify their relative performances via the post-processing signal-to-interference-plus-noise ratio distributions. We also compare the CoMP-specific front-haul rate requirements for all the schemes considered in this paper. Our results indicate that, with a linear minimum mean-square error receiver, the JRFD and TSEQ have identical performances, whereas S-TSEQ relaxes the front-haul latency requirements while approaching the performance of TSEQ. Furthermore, in a HetNet environment, we find that CS-AIM provides an attractive alternative to TBSD and LLR-E with a significantly reduced CoMP-specific front-haul rate requirement.

A network-assisted flow mobility architecture for optimized mobile medical multimedia transmission

A large part of mobile Health (mHealth) use-cases such as remote patient monitoring/diagnosis, teleconsultation, and guided surgical intervention requires advanced and reliable mobile communication solutions to provide efficient multimedia transmission with strict medical level Quality of Service (QoS) and Quality of Experience (QoE) provision. The increasing deployment of overlapping wireless access networks enables the possibility to offer the required network resources for ubiquitous and pervasive mHealth services. To address the challenges and support the above use-cases in today’s heterogeneous network (HetNet) environments, we propose a network-assisted flow-based mobility management architecture for optimized real-time mobile medical multimedia communication. The proposed system is empirically evaluated in a Pan-European HetNet testbed with multi-access Android-based mobile devices. We observed that the proposed scheme significantly improves the objective QoE of simultaneous real-time high-resolution electrocardiography and high-definition ultrasound transmissions while also enhances traffic load balancing capabilities of wireless architectures.

Scalability study of backhaul capacity sensitive network selection scheme in LTE‐WiFi HetNet

AbstractWireless heterogeneous network (HetNet) with small cells presents a new backhauling challenge that differs from those of experienced by conventional macro‐cells. In practice, the choice of backhaul technology for these small cells whether fibre, xDSL, point‐to‐point and point‐to‐multipoint wireless, or multi‐hop/mesh networks, is often governed by availability and cost and not by required capacity. Therefore, the resulting backhaul capacity of the small cells in HetNet is likely to be non‐uniform because of the mixture of backhaul technologies adopted. In such an environment, a question then arises whether a network selection strategy that considers the small cells' backhaul capacity will improve the end users' usage experience. In this paper, a novel dynamic backhaul capacity sensitive (DyBaCS) network selection scheme is proposed and compared with two commonly used network selection schemes, namely, WiFi First and physical data rate in an LTE‐WiFi HetNet environment. The proposed scheme is evaluated in terms of average connection or user throughput and fairness among users. The effects of varying WiFi backhaul capacity (uniform and non‐uniform distribution), WiFi‐LTE coverage ratio, user density and WiFi access points (APs) density within the HetNet form the focus of this paper. Results show that the DyBaCS scheme generally provides superior fairness and user throughput performance across the range of backhaul capacity considered. Besides, DyBaCS is able to scale much better than WiFi First and physical data rate across different user and WiFi densities. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Deciding Handover Points Based on Context-Aware Load Balancing in a WiFi-WiMAX Heterogeneous Network Environment

The heterogeneous network (HetNet) is an important concept for next-generation wireless Internet architecture and Internet of Things, where several wireless technologies can coexist, and the users should have the flexibility to select the connectivity based on the environmental condition and application demands. IEEE 802.11 (or WiFi) and IEEE 802.16 (or WiMAX) are the two primary building block technologies for HetNets because of their sustainability, cost effectiveness, well-deployed architectures, and ability to support high-data-rate wireless communications. The existing literature has extensively studied the interoperability between these two technologies, and seamless handover schemes are designed to support WiFi-WiMAX integration in a HetNet environment. However, effective utilization of these two technologies from the end users' point of view is another important research area. The authors have the following question: When should a user migrate between these two technologies in a HetNet environment? This paper proposes a handover decision mechanism in a WiFi-WiMAX integrated HetNet environment, which supports the “quality of service” and “quality of experience” requirements of the end users. The effectiveness of the proposed scheme is analyzed using simulation results.

Reverse Auction Based Green Offloading Scheme for Small Cell Heterogeneous Networks

The small cell is treated as a promising proposition to provide hot spot capacity and higher data rates. However, even with dense small cell deployment scenario, the heavy traffic load pressure and low energy efficiency in the small cell heterogeneous network (HetNet) still exist. Therefore, how to make the best use of densely deployed small cells under HetNet environments becomes the focus of researches. Offloading provides a feasible solution to promote cooperation between macrocells and small cells for user traffic supporting. In this paper, we propose the reverse auction based Green Offloading (GO) scheme for energy efficiency improvements. The proposed GO scheme employs the reverse auction theory to handle the offloading decision process, aiming at maximizing the system energy efficiency under the constraints of user Quality of Service (QoS) requirements, bandwidth, and transmission power limitations. Moreover, the reverse auction model gives the facility of multicell coordination transmissions with multiple winners situation. The energy efficiency optimization problem with constraints is solved by Dynamic Programming method with Karush-Kuhn-Tucker (KKT) conditions. The Individual Rationality and Truthfulness of the reverse auction model are also proved. By comparing the energy efficiency performances of the proposed GO scheme with current works within the Long Term Evolution-Advanced (LTE-A) system downlink scenario, simulation results show the improvements of the proposed GO scheme.

A Femto-Aided Location Tracking Algorithm in LTE-A Heterogeneous Networks

In dense urban or indoor environments under a weak global positioning system (GPS) signal, the Long-Term Evolution Advanced (LTE-A) system can provide range measurements for location estimation of mobile stations (MSs). Based on the reference signals transmitted from macro base stations (mBSs), femto BS (fBSs), and neighbor MSs in LTE-A heterogeneous networks (HetNets), the femto-aided cooperative location tracking (FACLT) algorithm is proposed to estimate an MS's position. Since fBSs are user-deployed in the residential or business buildings, the locations of fBSs are usually not known exactly. Moreover, an MS can communicate with its neighbor MSs with the support of device-to-device (D2D) communications. To deal with the uncertain neighbor MSs' positions and the imprecise fBSs' positions, we utilize a Bayesian framework to investigate a distributed cooperative location tracking problem and a particle filter (PF) to develop the FACLT algorithm. Different femto-aided strategies are adopted to deal with the uncertainty of fBS position. The utilization of the PF not only allows the fusion of time difference of arrival (TDOA) and two-way time of arrival (TW-TOA) measurements but enables the line-of-sight (LOS)/non-LOS (NLOS) condition as well, based on the information of the Markov model or indoor map. Performance evaluation is conducted based on the system-level simulation of LTE-A HetNet environments, where the proposed FACLT algorithm using the assistive fBSs and cooperative MSs provides better location tracking of MSs.