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In this paper, a multi-cell joint optimization scheme based on pilot allocation is proposed in order to mitigate pilot contamination for multi- cell massive MIMO systems. This method measures interference of each pilot sequence caused by users multiplexing from adjacent cells exploiting the massive MIMO characteristics of fading channels. The scheme takes jointly optimizing a plurality of cells into...
In the underlay cognitive radio network, the secondary users are allowed to transmit concurrently with the primary users , which shows great potential to relieve the spectrum scarcity problem. However, it raises significant security issues at the physical layer due to the spectrum sharing approach. Different from most present research, in this paper we study the secure communication problem between...
Cognitive radio can be considered as an enabling technology to utilize the white spaces through efficient spectrum sharing techniques. Through the Shanon capacity formula, it is clear that channel capacity is crucial for communication when licensed and unlicensed users share the channels. Further, to address the channel capacity, signal to interference plus noise ratio (SINR) plays an important role...
Femtocell enable larger network capacity by improving channel state and reducing transmission distance. Hybrid access is an efficient approach to reduce cross-tier inference so as to enhance overall network performance. In this paper, we propose a new reverse auction-based access rate allocation mechanism to maximize the utility of the femtocell access point (FAP) and the user for hybrid femtocell...
Cognitive radio technology provides a framework for flexible way to utilize the white spaces using the various spectrum sharing techniques. Interference plays an important role in communication when the channels are shared by the licensed and unlicensed users. Further, the signal to interference plus noise ratio also provide the bounds for the channel capacity. For this the authors introduce a conflict...
In this paper, a study of the effect of full duplex on resource allocation for small cell network is presented. In our model, both the macro-base station and femtocell access point operate in full-duplex where users attempt to connect either to the base station or the femtocell access point. A resource allocation problem is formulated to adjust the base station and the femtocell access point transmitting...
We investigated the use of per-channel rate-adaptive FEC for superchannels, in the presence of fiber nonlinearity, inter-channel interference, and power variations. We found 3∼4% peak capacity and ∼ 0.3dB nonlinear power threshold increase in most cases compared to the conventional method.
The authors have proposed a fair solution to optimal rate adaptation. The problem has been described in terms of the objective function, decision variables and constraints. Furthermore, using this problem definition, a rate adaptation heuristic was developed and divided into two sub- problems; part one requires finding the optimal rate allocation within the network, part two continues by finding a...
The Long Term Evolution-Advanced (LTE-A) networks are being developed to provide mobile broadband services for the fourth generation (4G) cellular wireless systems. Device to-Device (D2D) communications is a promising technique to provide wireless peer-to-peer communication services and enhance resource utilization, as well as spectrum efficiency. In this paper, a centralized resource allocation scheme...
In this paper, we consider a two way cognitive relay network using decode and forward (DF) protocol over Rayleigh fading channels. Under the joint outage constraint of the primary user (PU) caused by a pair of secondary transmitters (ST) and the secondary relay (SR), the problem of power allocation for the secondary users (SU) is reformulated. We derive the optimal power allocation algorithm for the...
A cooperative spectrum sharing, power allocation and user scheduling method is studied in this work under the framework of LTE self-organizing femtocell networks. Making use of dynamic channel and power allocation, and interference control, all femto access points (APs) in a self-organizing network (SON) can share the channels available to the SON with guaranteed quality of service. Simulation results...
In orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems, the optimized algorithms for sub-carrier power allocation face the problems of complex iterative calculation and difficult realization. In this paper, we propose an exponential power distribution function and derive a sub-optimal power allocation algorithm. This algorithm aims to allocate power of in-band subcarriers...
The physical layer network coding (PNC) takes advantages of signal interference at relay node and improves the channel capacity, therefore, PNC becomes an important research topic. However, the frequency-selective fading channel would destroy the performances of PNC. This paper considers orthogonal frequency division multiplex (OFDM) in PNC, when signals transmitted over a frequency-selective fading...
Cognitive relay networks have been studied for the advantages of improving the throughput of secondary users. Relay location and power allocation are the key issues in cognitive relay networks, which impact on the system performance. In this paper, we analyze the problem of optimal relay location and power allocation in cognitive relay networks. Firstly, we deduce an ergodic capacity formula for the...
Device-to-Device (D2D) communications underlying cellular networks have been regarded as a promising way to satisfy the growing requirement for data traffic. However, the D2D pairs may bring significant interference to cellular networks when they share the channel with the cellular user equipments (UEs). In this paper, we consider the scenario in which the D2D pairs share the uplink channel with the...
In the literature, researchers have evaluated optimal power loading algorithms under the Zero Mean Circularly Symmetric Complex Gaussian (ZMCSCG) constraint in OFDM based CR systems. The capacity of the Secondary User (SU) is maximized while keeping the interference introduced to the Primary User (PU) band remains within tolerable range. However the drawback of such an approach is that channel capacity...
The optimization of the channel capacity in the new fourth generation (4G) wireless networks became a key issue during the last decade. In this work, the co-existence of macrocell Base Stations (MBSs) and Femtocell Access Points (FAPs) or home base stations (HBS) with shared and dedicated carrier frequency allocations is considered. The simulation framework for analysis of channel capacity improvement...
In this paper, we evaluate the total ergodic capacity of channels in an OFDMA cognitive radio network using the interference concept. It is assumed that all links associated with primary and secondary networks experience Rayleigh fading. The optimum power allocation scheme and the channel capacity are derived under different secondary to primary interference constraints. These constraints at the primary...
In cognitive multimedia mesh networks (CMMNs), unlicensed users (secondary users, SUs) can share the spectrum with licensed users (primary users, PUs) on a non-interfering basis. The main challenge in CMMN is how to implement an efficient optimal control policy that can allocate spectrum and transmission powers for the SUs efficiently and how to adapt these resources to the changing network conditions...
In this paper, we consider a cognitive radio network in which multiple pairs of secondary users (SUs) exchange their information over two-way relay orthogonal channels with the existence of an eavesdropper. The SU pairs share the same frequency band with a primary user (PU) by satisfying the interference power constraint, and the eavesdropper can listen to all the frequency bands. Our goal is to maximize...
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