Dynamic Frequency Reuse Research Articles

5G multi-tier radio access network planning based on voronoi diagram

Network planning of multi-layer heterogeneous mobile networks with complex topology is an important task. In this paper the spectral and energy efficiency of integrated LTE/Wi-Fi technologies for 5G are improved. A method of adaptive formation of the structure of radio access level (RAL) with the provision of the required quality of service (QoS) and the possibility of broadband data transmission is proposed. The Voronoi tessellation is used for designing the RAL of 5G mobile networks for the placement of base stations, which allowed optimum delimiting the coverage area for each base station and provide users the cell interface services. To minimize interference there was proposed a method of dynamic frequency reuse for different sizes of Voronoi cells. Modelling shows the developed method is effective both at low and at high network load, however, at high load there is a slightly smaller gain in energy efficiency than at low load.

Dynamic resource allocation and interference coordination for millimeter wave communications in dense urban environment

AbstractInter cell interference coordination (ICIC) strategies in cellular systems have vital importance for spectrum efficiency in dense urban networks. Frequency reuse and resource allocation approaches are used to overcome the interference and the efficiency problems. Users in the cell edge suffer from low throughput and signal to interference plus noise ratio. Although increasing the transmit power of the BS can be considered as a solution, it also causes ICI. Considering these difficulties, we propose a technique called Experience Based Dynamic Soft Frequency Reuse in the 5G millimeter‐wave (mmWave) at 28 GHz band. The first objective of the proposed technique is to minimize the inter cell interference by using Soft Frequency Reuse method. The technique also aims to increase the overall system throughput by using Dynamic Channel Allocation. The third objective is to progress a fairness scheduler algorithm among users by optimizing the base station schedulers, which we call Experience‐Based Packet Scheduler. The main purpose of this article is to find the best value for α in order to maximize the average user and cell edge user throughput while considering the users' fairness. Simulations and numerical results show that the proposed algorithm can achieve up to 30% higher performance in terms of the average user throughput rates and has better fairness for lower α values (0.3 and 0.4).

Joint power and spectrum allocation for D2D communication overlaying cellular networks

Device to Device communication (D2D) for the cellular networks enables direct communication between the mobile devices that are in close proximity of each other. However, the scarce cellular spectrum for D2D in-band overlay communication must be intelligently assigned in order to optimize the overall network spectral and energy efficiency. With the help of graph theory, we demonstrate that the joint power and spectrum allocation optimization problem has an exponential time complexity that increases with the number of D2D nodes and frequency resources. We then propose an algorithm that solves the aforementioned optimization problem in two phases. The first phase performs admission control for the nodes that meet the power feasibility requirement along with the resource block assignment based on frequency reuse strategies with the aim to minimize the required frequency resources, whereas, the next phase minimizes the required transmission power of the nodes scheduled on those resource blocks while meeting the Quality of Service (QoS) requirements. We also propose several dynamic frequency reuse strategies and highlight the trade-off between spectrum and energy efficiency within an outage constraint for a given network with different service requirements and applications. The proposed strategies outperform other state-of-the-art strategies effectiveness of which is evaluated using extensive network level simulations.

Optimal frequency reuse scheme based on cuckoo search algorithm in Li‐Fi fifth‐generation bidirectional communication

Huge demand for bandwidth and capacity is exhibited by various wireless users and applications, for that purpose now the light-fidelity (Li-Fi)-based technologies are developing. In visible light communication, the hybrid networks based on Wi-Fi and Li-Fi has emerged recently. It is based on the concept of integrating small cell Li-Fi networks with large coverage radio frequency (RF) communication systems. For bidirectional data communication, the access links use shared bandwidth since the link of wireless backhaul invokes in the visible light spectrum. Due to the RF spectrum shortage, the bandwidth of Wi-Fi access point (AP) and the coverage of Li-Fi AP are limited in the outdoor environment. To tackle this issue, the authors propose a swarm intelligence-based improved cuckoo search into the frequency reuse of a hybrid Wi-Fi–Li-Fi network in the outdoor environment. The proposed approach employed bidirectional visible light propagation with non-orthogonal multiple access (NOMA) which is an effective approach towards fifth-generation wireless networks. The NOMA can help various users at the same time with the same frequency and multiple power levels. The system throughput and spectral efficiency are improved with dynamic frequency reuse scheme. The simulation results are compared with conventional techniques to show its effectiveness.

Evidence‐based dynamic radio resource allocation to mitigate inter cell interference employing cooperative communication

The paper proposes a framework for traffic based dynamic radio resource allocation to mitigate Inter Cell Interference (ICI) in cooperative communication for LTE MIMO-OFDMA systems using evidence theory. The objective is to address ICI, by dynamic user categorization, resource partitioning and management of radio resources. Through evidence based dynamic categorization of users, dynamic frequency planning and dynamic allocation of resources, spectral efficiency is enhanced by increasing data rate of users. It requires the cell users to be categorized into edge and center users depending on the confidence factor, computed using Dempster Shaffer Combinational Rule (DSCR). A traffic based dynamic Soft Frequency Reuse (SFR) plan is proposed using categorized user information to partition the available resources i.e., subcarrier and associated power. A subset of resources is allocated to identified edge users based on dynamic traffic. The traffic based evidential categorization of users, partitioning of resources provides improved data rate and spectral efficiency of edge users. The allocation of resources is dynamic in the proposed framework, leading to an improvement of spectral efficiency from 6.6 b/s/Hz to 12.4 b/s/Hz in a cell. The proposed methodology adapts to the user traffic in a cell and allocates the resources satisfying maximum users.

Dynamic Frequency Reuse Based on Improved Tabu Search in Multi-User Visible Light Communication Networks

The visible light communication (VLC) system using light-emitting diodes (LEDs) is able to achieve a higher transmission rate compared with the traditional radio frequency network. However, the throughput and average spectral efficiency (ASE) of the system may decrease due to the inter-cell interference and the inter-user interference, particularly for the indoor environment, where the LEDs are densely deployed in the case of multiple users. To suppress such interference, we introduce innovatively the improved tabu search (TS) algorithm into the frequency reuse in the multi-user VLC networks. We propose a bidirectional double tabu list strategy to avoid getting trapped in the situation of the local optimum. In addition, we design the evaluation function and aspiration criterion of the algorithm. We employ the improved TS algorithm to find the optical dynamic frequency reuse scheme by combining the interference graph. The interference graph is used to determine the interference relationships and to construct the solutions to the algorithm. The simulation results show that our proposed scheme effectively improves the throughput and the ASE of the system without lowering the fairness performance, especially in the scenario of numerous users.

Interference Avoidance Using Dynamic Frequency Reuse For LTE-A System

To meet the increasing demand for spectrum in communication system, Long Term Evolution (LTE) system has been proposed. It allowed users to use a new and much wider spectrum comparing to the other previous technologies. To utilize the full capacity of the LTE system Frequency Reuse (FR) has been adapted. It is a promising aspect of transmission of high rate data stream with better system capacity and fading immunity in the modern Long-Term Evolution-Advanced (LTE-A) system. Fractional Frequency Reuse (FFR) is the commonly used frequency reuse technique to increase the system capacity. But the problem is, with introduction of FR, it also increases the Inter Cell Interference (ICI) of the system. The out of cell interference coming from the neighbouring e-NodeBs (eNB) as a result of using the same frequency band and they act as an interference source. This ICI decreases the system capacity, resulting in hampering of communication, browsing and in worst case no connection at all. This condition highly affects the users under a cell specially those who are located in the cell edge areas. To take care of this issue an approach called Dynamic Frequency Reuse scheme has been proposed in this paper to mitigate the interference thus increasing the system capacity. This scheme uses continuous assessment of resource allocation and choosing the best sub-band for the user with least interference. There is a sequential order to be maintained for the users with using off minimum Base Station (BS) transmit power. The cell edge area users are the primary concern in terms of increasing their service quality. MATLAB simulation software has been used to justify the theory that the proposed scheme is capable increase the capacity of the cell edge areas as well as the cell centre area user. The results achieved from the simulation also indicates that the proposed model can enhance the system capacity comparing to the existing FFR scheme.

Interference graph-based dynamic frequency reuse in optical attocell networks

Indoor optical attocell network may achieve higher capacity than radio frequency (RF) or Infrared (IR)-based wireless systems. It is proposed as a special type of visible light communication (VLC) system using Light Emitting Diodes (LEDs). However, the system spectral efficiency may be severely degraded owing to the inter-cell interference (ICI), particularly for dense deployment scenarios. To address these issues, we construct the spectral interference graph for indoor optical attocell network, and propose the Dynamic Frequency Reuse (DFR) and Weighted Dynamic Frequency Reuse (W-DFR) algorithms to decrease ICI and improve the spectral efficiency performance. The interference graph makes LEDs can transmit data without interference and select the minimum sub-bands needed for frequency reuse. Then, DFR algorithm reuses the system frequency equally across service-providing cells to mitigate spectrum interference. While W-DFR algorithm can reuse the system frequency by using the bandwidth weight (BW), which is defined based on the number of service users. Numerical results show that both of the proposed schemes can effectively improve the average spectral efficiency (ASE) of the system. Additionally, improvement of the user data rate is also obtained by analyzing its cumulative distribution function (CDF).

Dynamic Frequency Reuse: A Method for Interference Mitigation in OFDMA Based LTE-A Networks

Spectrum scarcity is one of the most discussed restraining aspects in wireless communication system. To solve this issue Frequency Reuse (FR) concept is introduced. It is a promising development to fulfil the requirement of Long Term Evolution Advanced (LET-A). With the introduction of FR comes the problem of Inter Cell Interference as the neighboring eNodeBs (eNB) which uses the same frequency band that will act as an interference source. In this paper, a Dynamic Frequency Reuse (DFR) method is anticipated. Continuous optimization of resource allocation of each cell is considered in this method. The important focus of the paper is to expand the capacity of the users placed in cell edge areas by reducing out of cell interference. Simulation has been done to prove that the proposed scheme leads to efficient resource management.

Joint Downlink Cell Association and Bandwidth Allocation for Wireless Backhauling in Two-Tier HetNets With Large-Scale Antenna Arrays

The problem of joint downlink cell association (CA) and wireless backhaul bandwidth allocation (WBBA) in two-tier cellular heterogeneous networks (HetNets) is considered. Large-scale antenna array is implemented at the macro base station (BS), while the small cells within the macro cell range are single-antenna BSs and they rely on over-the-air links to the macro BS for backhauling. A sum logarithmic user rate maximization problem is investigated considering wireless backhauling constraints. A duplex and spectrum sharing scheme based on co-channel reverse time-division duplex (TDD) and dynamic soft frequency reuse (SFR) is proposed for interference management in two-tier HetNets with large-scale antenna arrays at the macro BS and wireless backhauling for small cells. Two in-band WBBA scenarios, namely, unified bandwidth allocation and per-small-cell bandwidth allocation scenarios, are investigated for joint CA-WBBA in the HetNet. A two-level hierarchical decomposition method for relaxed optimization is employed to solve the mixed-integer nonlinear program (MINLP). Solutions based on the General Algorithm Modeling System (GAMS) optimization solver and fast heuristics are also proposed for cell association in the per-small-cell WBBA scenario. It is shown that when all small cells have to use in-band wireless backhaul, the system load has more impact on both the sum log-rate and per-user rate performance than the number of small cells deployed within the macro cell range. The proposed joint CA-WBBA algorithms have an optimal load approximately equal to the size of the large-scale antenna array at the macro BS. The cell range expansion (CRE) strategy, which is an efficient cell association scheme for HetNets with perfect backhauling, is shown to be inefficient when in-band wireless backhauling for small cells comes into play.

Dynamic frequency reuse based on guard regions in two‐layer heterogeneous networks

The guard region for a randomly select user is introduced based on the stochastic geometry model. The guard region, through which a frequency reuse criterion is proposed, is calculated based on parameters such as user position, path loss exponents and transmission power. A dynamic frequency reuse scheme based on the guard regions of macrocell users is proposed to mitigate inter-layer interference. A frequency reuse criterion, which changes along with user position adaptively and is derived through stochastic geometry theory, is believed to be the first effort that can be found in the literature.

Dynamic Orthogonal Frequency Division Multiple Access resource management for downlink interference avoidance in two‐tier networks

SUMMARYIn two‐tier networks, which consist of macrocells and femtocells, femtocells can offload the traffic from macrocells thereby improving indoor signal coverage. However, the dynamic deployment feature of femtocells may result in signal interference due to limited frequency spectrum. The tradeoff between broad signal coverage and increased signal interference deserves further exploration for practical network operation. In this paper, dynamic frequency resource management is proposed to avoid both co‐tier and cross‐tier Orthogonal Frequency Division Multiple Access downlink interference and increase frequency channel utilization under co‐channel deployment. A graph‐based non‐conflict group discovery algorithm is proposed to discover the disjoint interference‐free groups among femtocells in order to avoid the co‐tier interference. A macrocell uses the femtocell gateway for frequency resource allocation among femtocells to avoid cross‐tier interference. We formulate the optimized frequency resource assignment as a fractional knapsack problem and solve the problem by using a greedy method. The simulation results show that the average data transfer rate can be increased from 21% to 60%, whereas idle rate and blocking rate are decreased in the range of and , respectively, as compared with conventional graph coloring and graph‐based dynamic frequency reuse schemes. Copyright © 2013 John Wiley & Sons, Ltd.

Dynamic Spectrum Management for Intercell Interference Coordination in LTE Networks Based on Traffic Patterns

Next-generation cellular networks will provide users with better experience employing smaller cells, which results in high dynamics and strong interference. Conventional intercell interference coordination (ICIC) approaches are based on fixed or dynamic frequency reuse, which more or less underutilize frequency resources or reduce network-wide performance. As a result, the benefit brought by ICIC is questionable in practical networks. In this paper, we tackle this problem from the self-organizing network (SON) viewpoint by optimizing fractional frequency reuse (FFR) and adapting to dynamic traffic maps. The approach proposed by this paper formulates this problem as an optimization problem with multiple key performance indicators (Multi-KPIs), and a traffic-based dynamic spectrum management (DSM) algorithm is proposed to reduce the call drop and block ratio (CDBR) and to also improve the network throughput. To reduce further the cost of spectrum partition and assignment, we conduct data mining for the traffic maps from realistic networks and then obtain traffic stable states for a longer specific period of time. DSM based on the stable states (DSM-SS) approach brings further benefits for Long Term Evolution networks in terms of operational costs. Simulation results show that the proposed schemes significantly outperform the traditional schemes.

Joint Opportunistic Spectrum Sharing and Dynamic Full Frequency Reuse in OFDMA Cellular Relay Networks

This paper considers the problem of spectrum sharing in orthogonal frequency division multiple access cellular relay networks. Firstly, a novel dynamic full frequency reuse scheme is proposed to improve the spectral efficiency. Different from the conventional full frequency reuse scheme which only allows the base station (BS) reusing the subcarriers in the specific regions, an improved full frequency reuse scheme is proposed to allow the BS reusing all the subcarriers in the whole BS coverage region to exploit additional multiuser diversity gain. In order to dynamically reuse the frequency resource among the BS and relay stations (RSs) to further improve the spectral efficiency, the adaptive subcarrier scheduling is introduced into the improved full frequency reuse scheme to obtain more multi-user diversity gain, which forms the proposed novel dynamic full frequency reuse scheme. Secondly, in order to further increase the system throughput, the opportunistic spectrum sharing scheme is introduced to allow the RSs selectively reusing the subcarriers among each other, which joint with the proposed dynamic full frequency reuse scheme to intelligently allocates the subcarriers originally reused by the BS and a RS to another suitable RS which can best improve the system performance after considering the additional interference. Thirdly, in order to select The optimal reusing combination scheme of BS and RSs to exploit more potential system performance, a heuristic approach based on genetic algorithm is proposed to search the optimal BS and RSs combination to opportunistically share the frequency resource. Simulation results show that the proposed dynamic full frequency reuse scheme can obtain high spectral efficiency, fine fairness and low outage probability compared to the conventional full frequency reuse scheme. Furthermore, the system performance can be improved when considering the opportunistic spectrum sharing among RSs. Finally, after adopting the genetic algorithm, the system performance can be greatly improved by the frequency reusing among the optimal BS and RSs combination.

Power Allocation for Relay-Assisted TDD Cellular System with Dynamic Frequency Reuse

This paper considers the power allocation problem in a relay-assisted Time-Division-Duplex-based multiple-cell system. In such a system, the achievable data rate of each user is not only coupled with those of others due to the inherent dynamic spatial frequency reuse therein, but also coupled between consecutive time slots due to the required two-hop transmission, which results in the so-called "spatial-coupling" and "time-coupling" nature, respectively. To address both of the two coupling effects in a relay assisted TDD cellular system, we formulate an optimal power allocation problem for the asynchronous scenario of the system where different cells work independently. We observe that the problem is non-convex and NP-hard, but can be converted to Geometric Programming (GP) problems and solved by interior-point methods. In case there is no central controller and/or massive information exchange among cells is prohibitive, game theory is employed to derive the distributed solutions. Finally, we validate the proposed algorithms by extensive simulations.

Cost-Effective Frequency Planning for Capacity Enhancement of Femtocellular Networks

The femto-access-point, a low-cost and small-size cellular base-station, is envisioned to be widely deployed in subscribers homes, as to provide high data-rate communications with improved quality of service. As femtocellular networks will co-exist with macrocellular networks, mitigation of the interference between these two network types is a key challenge for successful integration of these two technologies. In particular, there are several interference mechanisms between the femtocellular and the macrocellular networks, and the effects of the resulting interference depend on the density of femtocells and the overlaid macrocells in a particular coverage area. While improper interference management can cause a significant reduction in the system capacity and can increase the outage probability, effective and efficient frequency allocation among femtocells and macrocells can result in a successful co-existence of these two technologies. Furthermore, highly dense femtocellular deployments—the ultimate goal of the femtocellular technology—will require significant degree of self-organization in lieu of manual configuration. In this paper, we present various femtocellular network deployment scenarios, and we propose a number of frequency-allocation schemes to mitigate the interference and to increase the spectral efficiency of the integrated network. These schemes include: shared frequency band, dedicated frequency band, sub-frequency band, static frequency-reuse, and dynamic frequency-reuse. We derive an analytical model, which allows us to analyze in details the users outage probability, and we compare the performance of the proposed schemes using numerical analysis.

Cognitive Radio Through Primary Control Feedback

A fundamental problem in dynamic frequency reuse is that the cognitive radio is ignorant of the amount of interference it inflicts on the primary license holder. Policies that attempt to limit interference without the active participation of the primary are thus difficult to implement. However, many wireless systems use flow control feedback such as ARQs. By listening to these control signals, a cognitive radio can obtain indirect information about the interference it generates and thus behave in an acceptable manner. This paper introduces an information-theoretic model of this basic observation and develops and analyzes algorithms that can exploit it. In particular, a simple generic strategy is proposed where the cognitive radio monitors the primary's effective packet rate and only transmits when that rate is above a threshold. The strategy is shown to have important universality properties with respect to unknown time-varying interference characteristics as well as favorable delay properties.

Cooperative interference mitigation using fractional frequency reuse and intercell spatial demultiplexing

For mobile wireless systems with full frequency reuse, co-channel interference near the cell coverage boundaries has a significant impact on the signal reception performance. This paper addresses an approach to efficiently mitigate the effect of downlink co-channel interference when multi-antenna terminals are used in cellular environments, by proposing a signal detection strategy combined with a system-level coordination for dynamic frequency reuse. We demonstrate the utilization of multi-antennas to perform spatial demultiplexing of both the desired signal and interfering signals from adjacent cells results in significant improvement of spectral efficiency compared to the maximal ratio combining (MRC) performance, especially when an appropriate frequency reuse based on the traffic loading condition is coordinated among cells. Both analytic expressions for the capacity and experimental results using the adaptive modulation and coding (AMC) are used to confirm the performance gain. The robustness of the proposed scheme against varying operational conditions such as the channel estimation error and shadowing effects are also verified by simulation results.

A PLL clock frequency multiplier using dynamic current matching adaptive charge-pump and VCO frequency reuse

A 3.5 times PLL clock frequency multiplier for low voltage different signal (LVDS) driver is presented. A novel adaptive charge pump can automatically switch the loop bandwidth and a voltage-controlled oscillator (VCO) is designed with the aid of frequency ranges reuse technology. The circuit is implemented using 1st Silicon 0.25 μm mixed-signal complementary metal-oxide-semiconductor (CMOS) process. Simulation results show that the PLL clock frequency multiplier has very low phase noise and very short capture time.