Outage probability analysis of device-to-device communications with frequency reuse-2 in fractional frequency reuse method

Device-to-device (D2D) communication is affirmed as one of the dynamic techniques in improving the network throughput and capacity and reducing traffic load to the evolved Node B (eNB). In this paper, we propose a resource allocation and power control technique in which two-pairs of D2D users can simultaneously share same uplink cellular resource. In this case, interference between D2D users and cellular users is no longer insignificant so it must be properly handled. The proposed scheme considers fractional frequency reuse (FFR) scheme as a promising method that can relatively reduce the intra-cell interference. The main objective of the proposed scheme is to maximize the D2D communication throughput and overall system throughput by minimizing outage probability. Hence, we formulate an outage probability problem and overall system throughput optimization problem while guaranteeing minimum allowable signal-to-interference-plus-noise ratio (SINR). For fair distribution of cellular resources to multiple D2D pairs, we used Jain's fairness index (JFI) method. Simulation is conducted in MATLAB and our simulation results demonstrate that the proposed scheme achieves remarkable system performance as compared with existing methods.

There for another way is needed to keep LTE reliable when use in indoor. Femtocell is the solution of the problem. But femtocell uses the same frequency spectrum as any other broadband services. The more femtocell used in an area, overall networks capacity will be disturbed by cochannel interference. There are two scenarios that were examined in this research experiment about femtocell LTE interference. That is between MBS - FUE and FBS - MUE. And then to both scenarios applied FFR method using 4 reuse frequencies, 1 frequency use in center cell and the other 3 is use in the edge cell, where the power transmit of the center cell is greater than edge cell. The using of FFR method is to decrease the interference. Parameter that being use to analyze is SINR value that observed from the user side. FFR algorithm simulated with Matlab 7.11.0 simulator to determine SINR value and to create Layout Position Model of FBS, MBS, and MUE/FUE. Simulation result shows that FFR method is able to increase SINR value in each scenarios. In Scenario 1 with random distance, where the distance between MBS - FBS is 572.503 meters, the distance between FBS - FUE is 33.8378 meters, and the distance between MBS - FUE is 541.288 meters. SINR value increased by 124.4194 dB, that is from 57.8716 dB to 182.291 dB. In scenario 2, where the distance between MBS - FBS is 604 meters, the distance between FBS - MUE is 37.5366 meters, and the distance between MBS - MUE is 641.291 meters. SINR value increased by 104.6943 dB, that is from 78.5277 dB to 183.222 dB. It shows the improvement of quality or the decrease of interference to both Macrocell User and Femtocell User after FFR method being applied.

To handle the fast-growing demand for high data rate applications, the capacity of cellular networks should be reinforced. However, the available radio resources in cellular networks are scarce, and their formulation is expensive. The state-of-the art solution to this problem is a new local networking technology known as the device-to-device (D2D) communication. D2D communications have great capability in achieving outstanding performance by reusing the existing uplink cellular channel resources. In D2D communication, two devices in close proximity can communicate directly without traversing data traffic through the evolved-NodeB (eNB). This results in a reduced traffic load to the eNB, reduced end-to-end delay, and improved spectral efficiency and system performance. However, enabling D2D communication in an LTE-Advanced (LTE-A) cellular network causes severe interference to traditional cellular users and D2D pairs. To maintain the quality of service (QoS) of the cellular users and D2D pairs and reduce the interference, we propose a distance-based resource allocation and power control scheme using fractional frequency reuse (FFR) technique. We calculate the system outage probability, total throughput and spectrum efficiency for both cellular users and D2D pairs in terms of their signal-to-interference-plus-noise ratio (SINR). Our simulation results show that the proposed scheme reduces interference significantly and improves system performance compared to the random resource allocation (RRA) and resource allocation (RA) without sectorization scheme.

Improving cell coverage and network capacity are main issues in LTE networks. By the emergence of heterogeneous cellular networks with different cell size, femtocells have been regarded as a low cost solution to improve poor indoor coverage for home users. However, as Femto Access Points (FAPs) are installed by users, self-organized techniques are needed for allocation of radio resources to femtocells. On the other hand, Fractional Frequency reuse (FFR) has been considered to improve spectral efficiency and quality of edge users in heterogeneous networks (HetNets). In conventional FFR methods, the macrocell area is partitioned into some regions and certain fractions of radio resources are considered for macrocell/femtocell users in each region. Therefore, radio resources are allocated to femtocell/macrocell users based on their region of presence without addressing the density of users in that region and consequently the interference level. In this paper, a new self-organized fractional resource allocation method is proposed for femtocells. The proposed method is based on Learning Automata where FAPs learn to choose the best fraction based on the feedback of femtocell users. Simulation results confirm that the proposed radio resource allocation method improves spectral efficiency and decreases the outage probability compared to conventional Strict FFR method.

Co-Channel interference appears a significant challenge in LTE-A heterogeneous networks (HetNets), which degrades the overall performance of the system. Therefore, an adequate interference management strategy is necessary to implement the HetNets properly. In this study, a new Fractional Frequency Reuse (FFR) method is proposed, where the whole coverage area of a macrocell is partitioned into three sectors and three layers. Moreover, the proposed FFR method divides the total bandwidth into seven subbands. Macrocells and femtocells efficiently utilize these subbands in different regions. The Monte Carlo simulation is run, to evaluate and examine the system in terms of throughput. The simulation results show that the proposed method achieves higher throughput and improves the overall performance of the LTE-A HetNet system when compared with the existing FFR methods.

Device-to-Device (D2D) communications underlaying cellular networks have been considered as an efficient way to improve the system capacity of the cellular networks in an underlaying paradigm. However, increasing interferences between regular cellular communications and D2D communications often prevent the overall system throughput from being further enhanced. To address the corresponding interference management issue, we in this paper study the intelligent resource allocation for D2D pairs. Unlike the conventional resource allocation scheme where each D2D pair shares only one cellular user's entire resources upon approval, our approach allows D2D pairs to share only part of each cellular user's resources, such that the interference on regular cellular communications can be suppressed. In the mean time, D2D pairs can share multiple cellular users' resources to meet their own quality of services (QoS) requirement. Following the aforementioned principles, we propose a Partial Time-frequency Resource Allocation (PRA) framework for D2D communications. Under this framework, we design a category of sharing functions to map the channel status between D2D transmitters and cellular receivers to the resource proportion shareable for D2D users, through which a suboptimal yet simple and effective solution is derived, termed PRA scheme. Simulation results show that while meeting the D2D users' QoS requirement, our proposed PRA scheme can improve the overall system capacity and stability as compared to the conventional approaches.

Device‐to‐device (D2D) communication underlaying cellular networks is considered a promising technology to enhance network throughput, spectral efficiency, and performance of next generation networks. However, these potential gains hinge on the exploiting mechanism for resource sharing between cellular users (CUs) and D2D pairs. In this paper, we analytically formulate the problem of resource sharing as an optimization problem to maximize network throughput while guaranteeing the required quality‐of‐service (QoS) for both cellular and D2D users. We propose a low‐complexity four‐step resource allocation algorithm to address the optimization problem. We exploit a distance‐based method to derive a resource reuse candidacy graph (RCG) and three exclusive regions (ERs) to evaluate the suitability of resource sharing between each CU and D2D pair. Then, we use a paring mechanism to find the optimal set of D2D pairs for spectrum sharing with each CU to maximize network throughput. The performance of the proposed algorithm is investigated in terms of network throughput, outage probability, and computational complexity. Numerical results show that the proposed algorithm provides high throughput and spectrum utilization with low complexity while efficiently guaranteeing QoS for CUs and D2D pairs.

The sum throughput of a cellular network can be improved when nearby devices employ direct communications using a resource sharing technique. Multicast device-to-device (M-D2D) communication is a promising solution to accommodate higher transmission rates. In an M-D2D communication, a multicast group is formed by considering a transmitter that can transmit the same information to multiple receivers by considering the transmission link conditions. In this paper, we focus on the uplink interference generated due to the non-orthogonal sharing of resources between the cellular users and M-D2D groups. To mitigate the interference, we propose a spectrum reuse-based resource allocation and power control scheme for M-D2D communication underlaying an uplink cellular network. We formulate the throughput optimization problem by considering the fractional frequency reuse (FFR) method within a multicell cellular network. In addition, a metaheuristic-tabu search algorithm is developed that maximizes the probability of finding optimal solutions by minimizing uplink interference. To analyze fairness resource distribution among users, we finally consider Jain’s fairness index. Simulation results show that the proposed scheme can improve the coverage probability, success rate, spectral efficiency, and sum throughput of the network, compared with a random resource allocation scheme without a metaheuristic-tabu search algorithm.

This paper investigates the uplink spectral efficiency (SE) characterization and energy efficiency (EE) optimization of device-to-device (D2D) communications underlying a multi-cell massive multiple-input single-output (m-MISO) network, assuming that the channels are modeled with Rician fading. First, an analytical expression for the lower-bound of the ergodic capacity of a typical cellular user (CU) is derived with imperfect channel state information in the presence of D2D links’ interference. Then, a closed-form approximate achievable SE expression for a typical D2D pair is derived considering Rician fading between D2D pairs. The asymptotic SE behavior is analyzed in strong line-of-sight (LOS) conditions for CU and D2D pairs. Also, simplified expressions are obtained for the special case of Rayleigh fading. Next, to optimize the total EE, a transmit data power allocation based on the derived rate expressions is formulated. Since the optimization problem has a non-linear and non-convex objective function, it is intractable to be solved straightforwardly. Therefore, we resort to utilizing an iterative algorithm relying on fractional programming. The numerical results show that a stronger LOS component (i.e., larger Rician K-factor) between a typical CU and its serving BS leads to a significant improvement in the system performance, while it has less effect on the D2D network.

Many of the most advanced technology has a basic need for efficient telecommunication. In order to achieve this goal, the team should allocate those frequency channels in an intelligent way so that the interference can be reduced to the maximum extent. Here the team introduced a new method based on IFR3&IFR1 (Integer frequency reuse) in a 19-cell network, but also apply the FFR (fractional frequency reuse) method to reduce the interference ulteriorly. In the pure IFR situation, the integer frequency reuse factor and the cellular network specification collectively decide the network capacity. While in FFR only a fraction of the whole bandwidth is used by the users in the edge. By contrast, the users near the BS can make use of the total bandwidth. The cell is divided into an outer and an inner part in this effective way. Fractional Frequency Reuse (FFR) and its derivative method are accepted widely in the downlink (DL) inter-cell interference coordination(ICIC) schemes. The team also optimized the FFR method by measuring the distance in a more precise way. The team utilized Matlab to make a simulation of the system applying the new method and come to a couple of reasonable conclusions by comparing the FFR+IFR3 with FFR+IFR3. FFR+IFR3 has a better performance against FFR+IFR1 in a system whose distance between each cell is with more accuracy. While the average number of users per cell and transmission power for cell edge have little impact on average capacity. When the SNR increases, the network capacity starts steep but later flattens. Our method is more intelligent and can minish interference efficiently.

The performance of Device-to-Device (D2D) commu- nications in a cellular network depends on the resource sharing scheme between D2D links and cellular users. Existing research on resource sharing mainly focuses on power allocation under the condition that each D2D pair shares one cellular user's entire resources upon approval. Unlike conventional resource sharing schemes, this paper focuses on the low energy characteristics of the filtered OFDM signals in the guard band, and provides a novel resource sharing strategy which allows D2D pairs to share only part of one cellular user's resources. In the proposed approach, the base station allocates the resource blocks in the guard band to the D2D pairs first; if the allocated resource blocks can't meet the D2D communication requirement, the base station allocates part of the downlink resource blocks to the D2D users. The proposed scheme can further suppress the cellular-user-induced interference, and thereby improves the D2D capacity performance while guaranteeing the stability of cellular communications. Numerical results show that the proposed resource sharing strategy provides better D2D capacity performance.

The increasing demands for multimedia mobile traffics in cellular communication networks have resulted in a massive increase in interests of researchers to increase network capacity and to improve the network quality. Device to Device (D2D) communication has emerged as a promising technology to improve spectral efficiency further. In a conventional cellular network, cellular users or Cellular User Equipment (CUE) communicate with each other through a central coordinator such as a base station (BS) or E node B (eNB). D2D communication allows the users (D2D pair) communicate directly each other without going through eNB. However, enabling D2D communication in the cellular networks cause the interference issues, since D2D devices share the frequency bandwidth with the conventional cellular networks, i.e., in-band D2D. The interference situations become more worse in the multicell scenario of cellular system. This paper proposes a resource allocation method for D2D communication in downlink cellular systems using soft Fractional Frequency Reuse (FFR) scheme. Modeling and simulation have been used to examine the proposed soft FFR in multicell scenario consisting of three cell of macrocell cellular communication networks. Extensive simulation experiment has been carried out and the performance parameters in terms of Signal to Interference plus Noise Ratio (SINR), throughput, and Bit Error Rate (BER) has been measured. The simulation results for soft FFR are compared to the three multicell cellular networks without soft FFR. The simulation results show that the proposed soft FFR can improve the cellular network with a number of D2D pairs deployed. SINR performance achieves 50% improvement with 100 D2D pairs deployed in the cell center of macrocell.

In this paper, the tradeoff between energy efficiency and spectral efficiency in multicell heterogeneous networks is investigated. Our objective is to maximize both energy efficiency and spectral efficiency of the network, while satisfying the minimum rate requirements of the users. We define our objective function as the weighted summation of energy efficiency and spectral efficiency functions. The fractional frequency reuse (FFR) scheme is employed to suppress intercell interference. We formulate the problem as cell-center boundary selection for FFR, frequency assignment to users, and power allocation. The optimal solution of this problem requires exhaustive search over all cell-center radii, frequency assignments, and power levels. We propose a three-stage algorithm and apply it consecutively until convergence. First, we select the cell-center radius for the FFR method. Second, we assign the frequency resources to users to satisfy their rate requirements and also maximize the objective function. Third, we solve the power allocation subproblem by using the Levenberg-Marquardt method. Minimum rate requirements of users are also included in the solution by using dual decomposition techniques. Our numerical results show a Pareto-optimal solution for energy efficiency and spectral efficiency. We present energy efficiency, spectral efficiency, outage probability, and average transmit power results for different minimum rate constraints. Among other results, we show that, in a particular setting, 13% energy efficiency increase can be obtained in a multicell heterogeneous wireless network by sacrificing 7% spectral efficiency.

In OFDMA-based cellular system, inter-cell interference (ICI) reduces system capacity by aggravating receiving performance of the users located in edge of the cell. Therefore, to mitigate ICI is very important issue in cellular system. To deal with ICI problem, fractional frequency reuse (FFR) is introduced. FFR is an interference management technique. It separates each cell into inner cell and outer cell. Then, it allocates whole system bandwidth to inner cell and different frequency partition to each sector of outer cell. By doing this, outer cell users can ignore interferences from adjacent cells. So, the receiving performance of the cell edge users can be fairly increased. However, using FFR technique has a fatal side effect. In order to use different frequency partition among three sectors of outer cell, they can use only a third of the whole system bandwidth. Then, the reduction of available bandwidth reduces the system throughput directly. To solve this problem, we propose a new FFR method that allocates partially overlapped frequency partition to each sector of outer cell. And then, we suggest a proper overlapping ratio for practical cellular system.

The focus of this thesis is on studying the tradeoff between efficiency and fairness in interference-limited cellular networks. We start by characterizing the optimal tradeoff between efficiency and fairness in cellular networks, where efficiency is measured by the sum-rate and fairness is measured by the Jain's fairness index. Finding the optimal Efficiency-Jain Tradeoff (EJT) corresponds to solving potentially difficult non-convex optimization problems. To alleviate this difficulty, we derive sufficient conditions, which are shown to be sharp and naturally satisfied in various radio resource allocation problems. These conditions provide us with a means for identifying cases in which finding the optimal EJT can be reformulated as convex optimization problems. The new formulations are used to devise computationally-efficient resource schedulers that achieve the optimal EJT and surpass baseline schedulers in terms of EJT, median rate, and user satisfaction, without incurring additional complexity. Finding the optimal EJT in the long-term average rates in interference-limited cellular networks is tackled by designing an efficient inter-cell interference coordination (ICIC) scheme to manage interference by coordinating the allocation of radio resources across multiple cells. The goal of the ICIC scheme is to solve a multi-cell weighted sum-rate maximization optimization problem. By identifying a separable structure and a network-flow structure, we show that such optimization problem is amenable to powerful optimization methods, including the primal-decomposition method, the projected-subgradient method, and the network-flow optimization methods. Using these optimization methods, we propose a polynomial-time distributed ICIC scheme that finds a near-optimum multi-cell resource allocations. In comparison with baseline ICIC schemes, the proposed scheme is shown to achieve higher gains in efficiency, Jain’s fairness index, cell-edge rate, and outage probability.