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Coordinated Scheduling (CS) is one of the main techniques to control inter-cell interference in present (4G) and future (5G) cellular networks. We show that coordination of a cluster of nodes can be formulated as an optimization problem, i.e., placing the Resource Blocks in each node's subframe with the least possible overlapping with neighboring nodes. We provide a clever formulation, which allow...
Energy-efficient design has emerged as a promising technique in heterogeneous networks. We study the energy efficiency problem of joint user association and power allocation in a two-tier heterogeneous network with small cells. The energy efficiency is maximized under certain prescribed quality-of-service requirement and maximum power limit constraint. The original optimization problem is a nonconvex...
In this paper, we propose a new method of secrecy signal and artificial noise (AN) transmission for a MISO wiretap channel in wireless cellular networks. We first design the secrecy signal beamformer such that its power leakage to the unintended directions is minimized, then we concentrate the AN on the directions with higher risk of information leakage, rather than broadcast it isotropically, such...
In this paper, we propose a robust transmission strategy for multi-cell networks equipped with multiple-antenna base stations (BSs) under universal frequency reuse and in the presence of channel estimation error. We propose a distributed optimization scheme, where each BS individually minimizes a combination of its total transmit power and its resulting overall interference inflicted on the users...
In this paper, power allocation problem is presented for device-to-device (D2D) communications underlying cellular networks in multi-user scenario. In this scenario, multiple D2D pairs are allowed to share one cellular resource. As a preliminary study, we consider the scenario with only two D2D pairs and propose a power optimization scheme under this scenario. For cellular link and the D2D links sharing...
Joint optimization of user association, resource allocation and Almost Blank Subframe (ABSF) based enhanced Inter-Cell Interference Coordination (eICIC), on which macro-cells mute for scheduling the pico users, is of great importance to further improve the network performance in HetNets, however, the introduce of ABSF makes analyzing resource allocation extremely difficult because this results in...
In heterogeneous network where picocells are overlaid onto macrocells, combined usage of cell range expansion (CRE) and enhanced inter-cell interference coordination (eICIC) is very effective in improving the system capacity. Two parameters of the CRE bias value and the ratio of ABS (almost blank subframe) affect each other. Thus, the comprehensive control of both parameters is very important to improve...
We propose a cooperative spectrum sharing strategy in which the secondary system can access to the licensed spectrum of the primary system if it can help the primary system achieve the target rate. Specifically, the secondary system acts as a decode-and-forward relay for the primary system by splitting a fraction of its transmission bandwidth to help forward primary signal. It uses the remaining bandwidth...
Cooperative spectrum sensing has been proposed to significantly improve spectrum sensing accuracy by taking advantage of the cooperation among multiple secondary users (SUs). Most of existing work assumes that all SUs have the same SNR values of primary users' signal while the difference of SNR values among SUs, although it is very common in practice, is largely ignored. In this paper, we investigate...
In this paper, we focus on resource allocation for distributed broadband heterogeneous networks. Considering the fairness among different users, using the game-theoretic diagram, a fair resource allocation scheme is proposed first under each mobile user's minimal rate constraint. Then, an optimal power allocation algorithm is derived based on the Lagrange optimization method. To further improve the...
This paper addresses how to optimize the radio coverage area of OFDMA femtocell networks in enterprise deployment. Considering some basic requirements of coverage, including coverage holes, coverage overlaps, area spectral efficiency (ASE) and load balancing, the coverage optimization problem is modeled as a Multiple Attribute Decision Making (MADM) problem. Then the MADM-based coverage optimization...
In 3GPP Long Term Evolution (LTE) networks, the frequency reuse schemes such as fractional frequency reuse (FFR) and soft frequency reuse (SFR) are used to improve system capacity. The allocation of transmit power and subcarriers to each cell in these schemes are fixed prior to network deployment. This limits the potential performance of these frequency reuse schemes. In this paper, we propose to...
In this paper we propose a novel resource allocation scheme to achieve a balanced performance improvement for all users in a LTE network subject to inter-cell interference. In the proposed scheme the resource allocation process is implemented in two steps. In the first step interference coordination and scheduling are first conducted in a global manner to prevent cell-edge users from mutual interference...
In this paper, we present a binary-based low-complexity interference-aware relay selection scheme for a cognitive radio system with one source and multiple relays, using Biogeography-Based Optimization (BBO) algorithm as one of the novel high-performance Evolutionary Algorithms (EAs). We formulate the joint source and relay power allocation as a mixed integer non-linear programming problem, further...
Cognitive radio (CR) as one of the most promising technologies to solve the problem of exhausting of spectrum resource, draws a lot of attention recently. However, for the highly intelligent wireless devices in the future, the assumption "CR devices introduce no interference to the primary users (PUs)" in traditional CR systems may do not exist anymore, due to that the devices are always...
In this paper, we propose a distributed best-relay node selection scheme to maximize the achievable data rate for cooperative communications over underlay-paradigm based CR networks, and meanwhile guarantee that the primary link is provided with a minimum-rate for a certain percentage of time. Specifically, we formulate the CR relay network as a restless bandit system, where the finite-state Markov...
Optimization of hard fusion spectrum sensing using the k-out-of-N rule is considered. Two different setups are used to derive the optimal k. A throughput optimization setup is defined by minimizing the probability of false alarm subject to a probability of detection constraint representing the interference of a cognitive radio with the primary user, and an interference management setup is considered...
It is well-known that the optimal beamforming problems for cognitive multicast transmission are indefinite quadratic (nonconvex) optimization programs. The conventional approach is to reformulate them as convex semi-definite programs (SDPs) with additional rank-one (nonconvex and discontinuous) constraints. The rank-one constraints are then dropped for relaxed solutions, and randomization techniques...
The wireless ad-hoc networks do not rely on any infrastructure, which comes at the cost of finite and usually unreplenishable power supplies. It has been an area of intense research how to perform effectively maximum lifetime multicast delivery. This paper presents a new method for this problem, called the Directional Reception Two-step Reconstruction (DRTR). Firstly, based on conventional ad-hoc...
The Crane-umbrella Communication Jammer has become an important communication jamming equipment. During the interference process, the single jammer can cover a circular area and multiple jammers can be distributed to cover the target area without any vacancy, but it's a complex problem to distribute the jammers to use the least quantities of jammers, cover the maximal area and receive the signals...
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