Resource Allocation For Reconfigurable Intelligent Surface Assisted Dual Connectivity

<p>The next generation 6G wireless systems are envisioned to have higher reliability and capacity than the existing cellular systems. The reconfigurable intelligent surfaces (RISs) is one of the promising solution to control the wireless channel by altering the electromagnetic properties of the signal. The dual connectivity (DC) increases the per-user throughput by utilizing radio resources from two different base stations. In this work, we propose the RIS assisted DC system to improve the per-user throughput of the users by utilizing resources from two base stations (BSs) in proximity via different RISs. Given an fairness based utility function, the joint resource allocation and the user scheduling of RIS assisted DC system is formulated as an optimization problem and the optimal user scheduling time fraction is derived. The heuristic is proposed to solve the formulated optimization problem with the derived optimal scheduling time fractions. The exhaustive simulation results for coverage and throughput of the RIS assisted DC system are presented with varying user, BS, blockage, and RIS densities for different fairness values. Further, we show that the proposed RIS assisted DC system provides significant throughput gain of 52% and 48% in certain scenarios when compared to the existing benchmark and DC systems.</p>

Resource Allocation For Reconfigurable Intelligent Surface Assisted Dual Connectivity

<p>The next generation 6G wireless systems are envisioned to have higher reliability and capacity than the existing cellular systems. The reconfigurable intelligent surfaces (RISs) is one of the promising solution to control the wireless channel by altering the electromagnetic properties of the signal. The dual connectivity (DC) increases the per-user throughput by utilizing radio resources from two different base stations. In this work, we propose the RIS assisted DC system to improve the per-user throughput of the users by utilizing resources from two base stations (BSs) in proximity via different RISs. Given an fairness based utility function, the joint resource allocation and the user scheduling of RIS assisted DC system is formulated as an optimization problem and the optimal user scheduling time fraction is derived. The heuristic is proposed to solve the formulated optimization problem with the derived optimal scheduling time fractions. The exhaustive simulation results for coverage and throughput of the RIS assisted DC system are presented with varying user, BS, blockage, and RIS densities for different fairness values. Further, we show that the proposed RIS assisted DC system provides significant throughput gain of 52% and 48% in certain scenarios when compared to the existing benchmark and DC systems.</p>

Effects of Femtocell Ultradense Deployment on Downlink Performance in LTE Heterogeneous Networks

With huge number of smart gadgets and wireless devices being interconnected to each other, the demand for very high data bandwidth is becoming critically challenging. With such density of nodes inside wireless networks, providing high-quality service as well as wide coverage in indoor environment is a real challenge, which is due to the limited radio frequency and intense interference between nodes. As a one way to solve such problem and improve indoor service quality, femtocells have been introduced as an extension to the existing macrocell stations. Although femtocell is a promising technology, the pervasive deployment of huge number of femtocells without very tight network planning as well as coverage strategy may worsen the problem and degrade the service quality. One important problem that needs to be addressed when deploying femtocell technology in heterogenous networks (HetNets) is mitigating the various types of cross-tier and cotier interferences in between wireless cells. This study investigates the effect of unplanned ultradensity femtocell deployment in the downlink performance of two-tier heterogeneous networks in urban area based on LTE system. Instead of deploying femtocells one by one, grids of size either ( 3 × 3 ) or ( 5 × 5 ) of neighboring femtocell will be deployed inside each macrocell sector area. The simulation results show that femtocell deployment improves overall average user throughput in case of low and medium density scenarios. However, for ultradensity scenario, there is no enhancement in terms of fairness and throughput. The results confirm that this leads to high degradation for macrocell and femtocell user performance due to the severe interference between macrocells and femtocells, as well as among neighboring femtocells in each grid.

A Comparative Analysis of Wi-Fi Offloading and Cooperation in Small-Cell Network

Small cells deliver cost-effective capacity and coverage enhancement in a cellular network. In this work, we present the interplay of two technologies, namely Wi-Fi offloading and small-cell cooperation that help in achieving this goal. Both these technologies are also being considered for 5G and B5G (Beyond 5G). We simultaneously consider Wi-Fi offloading and small-cell cooperation to maximize average user throughput in the small-cell network. We propose two heuristic methods, namely Sequential Cooperative Rate Enhancement (SCRE) and Sequential Offloading Rate Enhancement (SORE) to demonstrate cooperation and Wi-Fi offloading, respectively. SCRE is based on cooperative communication in which a user data rate requirement is satisfied through association with multiple small-cell base stations (SBSs). However, SORE is based on Wi-Fi offloading, in which users are offloaded to the nearest Wi-Fi Access Point and use its leftover capacity when they are unable to satisfy their rate constraint from a single SBS. Moreover, we propose an algorithm to switch between the two schemes (cooperation and Wi-Fi offloading) to ensure maximum average user throughput in the network. This is called the Switching between Cooperation and Offloading (SCO) algorithm and it switches depending upon the network conditions. We analyze these algorithms under varying requirements of rate threshold, number of resource blocks and user density in the network. The results indicate that SCRE is more beneficial for a sparse network where it also delivers relatively higher average data rates to cell-edge users. On the other hand, SORE is more advantageous in a dense network provided sufficient leftover Wi-Fi capacity is available and more users are present in the Wi-Fi coverage area.

Interference-aware Coordinated Access Control for Heterogeneous Cellular D2D Communication Networks

Device-to-Device (D2D) communications is expected to be a key technology of the forthcoming mobile communication networks because of its benefits in terms of spectral efficiency, energy efficiency, and system capacity. To mitigate frequency collisions as well as reduce the effects of co-channel interference between user's connections, we propose an interference-aware coordinated access control (IaCAC) mechanism for heterogeneous cellular D2D communication networks with dense device deployment of user equipment (UEs). In the proposed network setting, we consider the co-existence of both macro base stations (MBSs) and smallcell base stations (SBSs). In the proposed IaCAC mechanism, MBSs and SBSs are coordinated to perform access control to their UEs while MBSs allocate bandwidth parts dynamically to SBSs based on the interference levels measured at SBSs. Besides, to reduce D2D-to-cellular interference, device user equipments (DUEs) can perform power control autonomously. Simulation results show that the proposed IaCAC can provide higher system throughput and user throughput than those achieved by the network-assisted device-decided scheme proposed in [21]. Moreover, simulation results also reveal that the proposed IaCAC also significantly improve SINR of MUE’s and SUE’s uplink connections.

LTE Network Analysis in Frequency Reuse Recycling Techniques

In recent years, several researchers have embraced fractional frequency (FF) reuse as a strategy for resolving the inter-cell and co-channel interferences of adjacent cells (ICI, CCI) as the number of wireless networks grows. This technique is focused on the cell division of two parts, the inner and the outer, which enables multiple frequency bands to be assigned. The frequency advantages can be completely used in each inner zone, since there is no inter-cell disturbance for consumers in inner regions. According to this effective usage of the frequency spectrum available, FF will reduce the interruption of the channel and improve device efficiency. This manuscript presents a comprehensive study of different mechanisms to select the optimal FF scheme based on the user throughput. The analysis was conducted in order to obtain the optimal internal and external range for the cells as well as the optimal frequency distribution between the areas of the FR, Fractional Frequency Reuse 1 (FFR1) and Fractional Frequency Reuse 2 (FFR2) and evaluating their outputs and their number of users. In detail the overall consumer efficiency through the configured frequency distribution is analyzed. The FFR is a resource allocation technique that can effectively mitigate inter-cell interference (ICI) in LTE based HetNets and it is a promising solution. The proposal also employs high number sectors in a cell, low interference and good frequency reuse. The processes are tested by way of multiple modeling simulations.

Personal Picocell Scheme Using Adaptive Control CRE in Heterogeneous Mobile Networks

Heterogeneous networks (HetNets), which are combined with a macrocell and picocell in the same coverage, are expected to further increase the system capacity in fifth-generation mobile systems and beyond. In HetNets, the cell range expansion (CRE) technique plays an important role and can allow more user equipment (UE) to access the picocell, i.e., virtually expand the picocell coverage. However, conventional CRE techniques that provide a fixed cell selection offset (CSO) for all UE may worsen user throughput if UE is forced to connect to the picocell because the received signal-to-interference plus noise ratio of the UE becomes lower. Therefore, we propose a personal picocell scheme using an adaptive control CRE technique to improve user throughput in which different CSOs are assigned to UE to form each optimal picocell for each UE. In this paper, we first describe the aspects and algorithm of the proposed scheme. Then, we show the user throughput for adaptive control CRE in comparison with conventional CRE by using system-level computer simulations for the two types of HetNets, i.e., single-band and multi-band HetNets. In the simulations, we first clarify the optimal parameters of the adaptive control CRE. We then show the average and 5-percentile user throughput of the optimized adaptive control CRE in comparison with that of conventional CRE. From these results, we confirmed that the personal picocell scheme using the adaptive control CRE can improve the 5-percentile user throughput while maintaining the average user throughput compared with that of conventional CRE.