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Motivated by the possibility of decreasing the intersymbol interference (ISI) which is due to large delays of a multipath mobile radio channel, orthogonal frequency division multiplexing (OFDM) became very popular. However, the timevariance of the mobile radio channel induces intercarrier interference (ICI) yielding substantial channel estimation errors and thereby tremendous transmission impairments...
Coordination of base stations is essential in the mitigation of inter-cell interference in cellular communication systems. One of practical solutions is a cluster-based intercell scheduling where base stations in each cluster determine their transmissions in cooperative fashion. In spite of potential performance improvement, the inter-cell scheduling may result in conflict between clusters. However,...
As a next generation mobile satellite network, an integrated satellite and complementary ground component (CGC) network is recently considered in order to provide seamless,transparent and ubiquitous wireless coverage over the world. In this network, it is essential to reuse efficiently frequencies between satellite and CGC components under tolerable interference level. In this paper, we propose how...
This paper investigates the legacy compatibility between IEEE 802.11n and 802.11a/g devices, focusing on the performance of legacy 802.11a/g auto-correlation and cross-correlation joint time and frequency synchronization schemes operating over 802.11n networks. It is shown that synchronization schemes based on auto-correlation metric allow the backward compatibility, considering a different number...
In this paper, we consider a multi-antenna wireless multicast system with multiple multicast groups. The problem of resource allocation with downlink precoding for the multicast systems is studied, assuming the channel state information between transmit and all the receivers is available at the transmitter. Specifically, we formulate an optimization problem to maximize the system throughput given...
In order to improve the transmit power efficiency at the Mobile Station (MS), the transmit power is usually adjusted based on feedback information from the Base Station (BS) or Channel State Information (CSI) estimated at the MS. In fast-varying channels, because of the propagation and estimation delays, and the short channel coherence time, both the feedback information and the estimated CSI may...
In this paper, the error performances and diversity gains of two wireless relay networks are studied. The distributed space-time block coding in a synchronous relay network with multiple relay nodes is considered. The distributed linear dispersion code is used at the relays. The symbol (or codeword) error rate is studied in terms of upper and lower bounds through rigorous derivations, and sufficient...
This paper presents results from a novel OFDMA multi-cell mobile broadband system-level simulator. The tool is used to statistically characterize uplink and downlink inter-cell interference. Fully loaded interference studies cannot be performed on real-world networks until they have been fully deployed. As such, interference analysis and management must be accurately performed pre- deployment using...
Nonlinearities can drastically degrade the performance of OFDM (orthogonal frequency division multiplexing) based optical wireless (OW) communication systems using intensity modulation (IM) of the optical carrier. The light emitting diode (LED) transfer function distorts the signal amplitude and forces the lower signal peaks to be clipped at the LED turn-on voltage (TOV). Additionally, the upper signal...
Radio Resource Management with Inter-cell Interference Coordination (ICIC), is a key issue under investigation for next generation wireless systems such as Long Term Evolution (LTE). Although centralized resource allocation (RA) and collaborative processing can optimally perform ICIC, the overall required complexity suggests the consideration of distributed techniques. In this paper we propose and...
In this paper we consider the design of a linearly precoded MIMO transceiver based on filter bank (FB) modulation for transmission over broadband frequency selective fading channels. The modulation FB is capable of lowering the channel dispersion at sub-channel level. Nevertheless, the sub-channels experience some level of inter-symbol interference. Therefore, the pre-coder and the equalizer are designed...
A wavelet packet transceiver for spectral analysis and dynamic spectrum access is presented. The transceiver consists of a Wavelet Packet Spectral Estimator (WPSE) and a Wavelet Packet Multi-carrier Modulator (WPM). The WPSE senses the radio environment to identify Licensed Users (LU) bands and spectrum holes. This information is then used to shape the time-frequency characteristics of the WPM transmission...
This paper analyzes the system-level performance of the long term evolution (LTE)/LTE-Advanced (LTE-A). LTE/LTE-A has been considered to be a promising next generation communication system. It is proposed to ITU-R to be acknowledged as an IMT-Advanced technology. The performance of candidate technology proposals for IMT-Advanced should be evaluated to see if it satisfies the predefined minimum requirement...
Adaptive transmission in IEEE 802.11 requires rapid rate adaptation according to the variation of wireless environments. Existing rate adaptation schemes such as Automatic Rate Fallback (ARF) have been commercially implemented due to its simplicity. However, collision detection, which is an essential requirement to avoid network congestion and maintain the quality of service (QoS), is not well investigated...
For orthogonal frequency division multiplexing (OFDM) systems in multipath channels, the detection of the first path is desirable to avoid inter-symbol-interference (ISI). However, the conventional peak detection of the cyclic prefix (CP) correlation curve can detect the strongest path but not the first path, while the largest slope detection is sensitive to background noise. This paper presents a...
In this paper, a cooperative iterative water-filling approach is investigated for two-user Gaussian interference channel. State-of-the-art approaches only maximize the individual user's own rate and always model interference as noise. Our proposed approach establishes user cooperation through sharing network side information. It iteratively maximizes the sum-rate of both users subject to distributed...
By extending OFDM symbols, acceptable BER performance can be achieved at low SNRs. Two alternative differential receiver architectures are presented, a receiver based on a FX correlator (Fourier transformation before correlation) and based on an XF correlator (correlation before Fourier transformation). To reduce the complexity and hence the power consumption of both the ADC and the first digital...
Iterative receiver structures that jointly perform channel estimation and decoding promise substantial performance gains. However, these gains only materialize with sufficiently accurate initial channel estimates. In this paper, initialization by multi-objective particle swarm optimization (MOPSO) is investigated. MOPSO supports low-complexity initial channel estimation with superimposed training...
Decision directed channel estimation (DD-CE) techniques turn useful for transmissions in time-varying wireless vehicular channels. CE has to be updated several times during the transmission of long data frames. Related works assume that, for IEEE802.11p-compliant physical layer systems, DDCE is performed for every input OFDM symbol, hence independently of the experienced Doppler effect. The purpose...
Evolutionary algorithms like genetic algorithms and ACO are potential candidates for solving any NP-hard problem, because of their ability to obtain acceptable suboptimum (or sometimes could be the optimum) solutions. This paper proposes an Ant Colony Optimization (ACO) based algorithm to solve the centralized resource allocation problem of a multicell multiuser OFDMA network. The proposed ACO is...
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