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In this paper, we introduce a full-duplex relay (FDR) based on block diagonalization (BD) and analyze the corresponding sum rate in a multiantenna multiuser relay system. The poposed precoding scheme can suppress the self-interference as well as to support multiple users at the same time slot. Simulation results show that the proposed FDR scheme enhances significantly the sum rate performance compared...
The next generation of wireless networks (e.g., Long Term Evolution (LTE)and WiMAX) use multiple techniques to improve channel spectral efficiencies. In this paper we focus on one such technique, namely Coordinated Beam Switching (CBS). With CBS, each sector determines a sequence of beams (possibly with repetitions) over which it continuously cycles. Each sector independently determines its beam pattern...
In this paper, we study the optimal power allocation of wireless relay nodes which are used in the secondary user (SU) communication of a cognitive radio (CR) network. We consider the behavior of transmitting powers of SUs where those powers are limited to the tolerable interference as seen by the primary user (PU) communication. To improve the performance of the secondary communication based on minimizing...
The latest generation of wireless networks use OFDMA (Orthogonal Frequency Division Multiple Access) transmission technology in the downlink (e.g, WiMAX and LTE). The downlink is divided into bandwidth units and UEs (User Equipments) are each allocated a subset of these. Since at most one UE is assigned to each of these units, downlink transmissions within a sector are orthogonal. However, the transmission...
In this paper, we consider the problem of joint adaptive beamforming from multiple Access Points (APs), equipped with array antennas, to multiple single-antenna User Equipments (UEs). We derive an iterative algorithm for Multi-Cell Beam-Forming (MCBF) under per-cell power constraints and the constraint that a UE may receive data transmission from a single AP. The scheme is suitable for coordinated...
This paper addresses the issues of coexistence for cognitive radio networks including both the coexistence between primary users (PUs) and secondary users (SUs), as well as the coexistence among SUs. The coexistence between SUs and PUs addresses the interference from SUs to PUs, whereas, the coexistence among SUs addresses sharing of identified spectrum opportunity among SUs to achieve efficient spectrum...
In the relay-enhanced cellular network, the target user will receive uncertain interference due to orthogonal transmission between BS and RS, which would make the traditional mechanisms of link adaptation and channel-aware scheduling invalid. In this paper, a novel resource scheduling scheme is proposed with a semi-static mode, in which dominant interferences for a target user are identified and inter-cell...
This paper investigates the problem of uplink subcarrier and power allocation in a Cognitive Radio (CR) network that operates opportunistically within vacant licensed Primary Users (PUs)spectrum. The resource allocation algorithm aims to maximize the CR network throughput under PUs interference constraints. In this paper, CR interference introduced into PUs sub-bands is modeled as a composite of two...
For mitigating inter-symbol interference (ISI) and inter-carrier interference (ICI) caused by insufficient cyclic prefix (CP), per-tone equalizer (PTEQ) outperforms traditional time domain equalizer (TEQ) since each tone is equalized independently. However, PTEQ with equal number of taps (equal length) for all the tones can not achieve the optimal performance because channel conditions of different...
Femtocell is one of promising key technologies to increase the efficiency and coverage of next generation broadband wireless networks. However, there exists interference problem between femtocells and macrocell due to co-channel operation. In this paper, we propose an efficient frequency resource allocation scheme for newly deployed femtocells in the legacy OFDMA networks in order to maximize the...
In this paper, we propose user grouping algorithms to provide power minimization in grouped MC-CDMA systems. Depending on the channel fading conditions, power control is utilized to minimize the total transmitted power under a bit error rate (BER) constraint. When the allocation is performed without a fair data rate requirement, we provide the optimal solution to the minimization problem. However...
Multi-cell cooperation has been regarded as a promising technique of the future cellular wireless network to achieve higher transmission rate and better QoS (quality of service) performance. Cooperation among base stations can be classified into two categories: centralized and distributed cooperation. In this work, we mainly consider efficient and practical cooperation clustering approaches in the...
In the downlink of multiuser MIMO (MU-MIMO) systems, the co-channel interference (CCI) and noise are two major impairments. Maximizing signal to leakage plus noise ratio (SLNR) is a good criterion for the design of precoders since it making a balance between eliminating the CCI and noise. In this text, we propose a channel adaptive power allocation scheme based on SLNR precoding. Simulation results...
In this paper, a new algorithm is proposed for cooperative beamforming and power allocation (CBPA) in the downlink of multi-input multi-output (MIMO) cognitive radio systems. Increasing the efficiency of spectrum usage is the main goal of the cognitive radio systems by servicing a number of secondary users in addition to the primary user. The proposed CBPA algorithm is developed based on a criterion...
The International Telecommunications Union established through the International Mobile Telecommunications-Advanced a set of requirements for high performance 4rd Generation communication systems and, with the aim of meeting such requirements, 3rd Generation Partnership Project Long Term Evolution (LTE) is considering a set of enhancements, referred to as LTE-Advanced. In LTE-Advanced context, Coordinated...
The goal of our work is to limit in-band inter-cell interference in wireless communication cellular systems. Based on interference classification techniques, we propose a novel centralized inter-cell power allocation algorithm which computes the minimum power budget required in each cell to meet its local quality of service (QoS) constraints. Both analytical and numerical results applied to cellular...
This paper studies the different uses of repeaters and remote radioheads (fiber repeaters) in cellular networks. Traditional uses include coverage extension and eliminating points of pilot pollution (three-way handoff). In addition, we find that careful placement of repeaters can improve capacity substantially. We also find that in layouts where some sectors are much more heavily loaded than others,...
In this paper, we consider a system based on Orthogonal Frequency Division Multiple Access (OFDMA) and investigate the benefits of combining the Satisfaction Oriented Resource Allocation (SORA) algorithm, which aims at maximizing the number of satisfied users in a system, and Orthogonal Random Beamforming (ORB), which provides spatial multiplexing gains and has low computacional complexity, low signaling...
It has been identified in numerous contributions that dynamic interference coordination is very appealing in case of dense and uncoordinated deployments of home eNBs, also known as femtocells. One of the proposed schemes for LTE-Advanced is known as Autonomous Component Carrier Selection (ACCS). Previous contributions presented extensive downlink performance results attesting the effectiveness of...
Resource (power and bandwidth) allocation is an important issue in orthogonal frequency division multiple access (OFDMA) systems. For multi-cell systems, the interference across different cells makes the optimization of resource allocation difficult. Large system analysis is applied for multi-cell OFDMA systems with the fairness constraint of equal grade of service (EGOS). An interference function...
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