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Our novel work presents an intelligent, unsupervised organizing neural network based, high power amplifier (HPA) characteristics independent, adaptive method for compensation of nonlinear distortions for orthogonal frequency division multiplexing (OFDM) based wireless communication system. Major elements that contribute to multipath fading effects, like Doppler Effect, interference effects, phase...
Orthogonal Frequency Division Multiplexing (OFDM) in combination with Multiple Input Multiple Output (MIMO) is a popular method for high data rate wireless transmission. The use of multiple antennas at both sides of the link offers an additional fundamental gain-spatial multiplexing gain, which results in increased spectral efficiency. This paper is concerned with the simulation, modeling and performance...
Construction of a cognitive radio network presents a number of challenges, among them communication of the control signals that will allow dynamic spectrum allocation/access (DSA) in the network. The available spectral bands may be retrieved from geolocation databases or the nodes within the cognitive radio network examine the spectra for the primary users activities, thus, identify the white spaces...
Multiple input multiple output (MIMO) - Orthogonal Frequency Division Multiple Access (OFDMA) systems have great potential for providing high spectral efficiency due to its integrated space-frequency and multi-user diversity. In this work a dynamic resource allocation scheme has been devised for MIMO-OFDMA systems in a downlink scenario. The scheme optimizes the power distribution, guarantees each...
To deal with problems that queuing information is not included in cognitive information when performing Resource Allocation (RA), a dynamic cross-layer scheme is proposed for the multimedia cognitive radio (CR) system with Orthogonal Frequency Division Multiplexing (OFDM). In this scheme, we consider that several crucial factors influence the RA decision, including channel state information, interference...
In conventional multicast scheme (CMS), the total throughput of multicast group is constrained by the user with the worst channel quality. In order to overcome this problem of limited throughput, we consider a resource allocation algorithm based on layered coding, when a limited feedback scheme is considered. A novel subcarrier and power algorithm is exploited for targeting the maximum throughput...
We propose an adaptive multiuser QoS-based scheduler based on the users' channel measurements. In order to mitigate the complexity that results from computing non-codebook based beamformers for possibly infeasible users, we propose to preselect the optimal users using a virtual signal-to-noise ratio (vSNR). This is computed assuming non-interfering users and a total power constraint. Solely depending...
Femtocells are low power access points that can be deployed by the consumer indoors to alleviate cellular coverage problems, offload traffic from the cellular network and boost user data rates. To enable the widespread of femtocells coexisting with macrocells, smart interference management schemes are required. Interference management by frequency allocation is still a big challenge in hybrid macro/femto...
Performance optimization of communication networks with quality of services (QOS) considerations for all active users is highly desirable. Using minimum data rate as the primary criterion for the QOS, in this paper, we provide a resource allocation solution for an OFDMA downlink which gets to be optimum when the number of subcarriers goes infinity and the proposed algorithm satisfies QOS of all users...
We study in this paper the problem of queueing theoretic of OFDMA-based WiMAX with two classes of connections, connections with High Priority (HP) and connections with Low Priority (LP). The key idea to solve the problem of the mixed priority strategy is the technique of the Shadow server approximation. Specifically, we present a single-cell WiMAX environment in which the base station allocates subchannels...
This paper studies the resource allocation problem in orthogonal frequency division multiple access (OFDMA) cooperative relaying cellular systems. Most existing work on resource allocation does not fully consider all the influential factors for such systems. In the paper, we formulate the optimization problem for resource allocation, including relay selection, subcarrier assignment, and power allocation...
In this paper, we investigate spectrum sharing and multiple access problems for the high-rate ultra-wideband (UWB) systems. Based on the use of the linear precoded orthogonal frequency division multiplexing (LP-OFDM) proposed as an evolution of the well known multi-band OFDM (MB-OFDM) solution supported by the WiMedia Alliance for future high-rate UWB systems, the objective of this paper is to study...
LTE uses the SC-FDMA radio access technology for its uplink transmission. As a result, resources assigned to the same user must be contiguous in the frequency domain. Several uplink scheduling algorithms were proposed in the literature to fit that constraint. These algorithms take as input a matrix which is used by the Packet Scheduler for an efficient resource allocation. The performance of these...
In the paper, an improved link adaptation scheme is proposed for the WiMedia MB-OFDM UWB system, in which quality of service (QoS) support is provided. The proposed scheme consists of three functional blocks: link quality indicator (LQI) calculator, frame error rate (FER) estimator, and transmitter (TX) parameter selector. Instead of using the average receive SNR (ASNR) as LQI, a new LQI metric is...
In this paper, we present a study on the spectrum sharing matter in orthogonal frequency division multiple access (OFDMA) systems under heterogeneous constraints leading to a joint time-frequency resource allocation model. To take advantage of the flexibility of the OFDMA-based resource allocation scheme, we analytically study the spectrum sharing matter by deriving an optimization problem that takes...
This paper studies QoE (Quality of Experience) enhancement of audio-video IP transmission over the uplink channel, i.e., from subscriber stations (SSs) to the base station (BS), in the IEEE 802.16 BE service. We assume two types of capacity allocation schemes for uplink and downlink burst durations: static and adaptive. Furthermore, we introduce a piggyback request mechanism for uplink bandwidth requests...
We propose a cross-layer algorithm for the down link multiuser orthogonal frequency division multiplexing (OFDM) system. The goal of this algorithm is to ensure fairness among users while preserving the full system throughput as close as possible to the system throughput upper bound. For this, a function is formulated to designate which packet will be scheduled at any given time. This function takes...
In this paper, the filter-and-forward (FF) relay design for OFDM communication systems is considered to enhance the system performance over the conventional amplify-and-forward (AF) relaying scheme. The considered design criterion in this paper is to maximize the worst subcarrier channel signal-to-noise ratio (SNR) subject to the total relay transmit power constraint in order to improve the overall...
To provide high quality of multimedia service in mobile environment, mobile IPTV service technology that enables higher reliability of transmission quality and multimedia service to many subscribers has been developed. One of the important technologies for mobile IPTV is to mitigate interference. This can be done by the configuration of MBS zone. 3GPP/LTE and Mobile WiMAX support MBS technology to...
In this paper, we study the cross-layer resource allocation for the secondary users (SUs) supporting heterogeneous services in interference-limited spectrum sharing system. Two classes of SUs are considered: delay-tolerant SUs (DT-SUs) and delay- sensitive SUs (DS-SUs). With the queue theory, the delay requirements of DS-SUs are transformed into constant rate requirements. Unlike most previous works,...
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