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Diverse quality of service (QoS) guarantee is critical in wireless multimedia communications to fulfill the requirements of various applications. QoS with conventional single queue scenario has been very much explored but few studies were done on multiple queue system. In this paper, we propose a new multiple queue finite-state Markov chain model where multiple queues are employed at medium access...
Orthogonal Frequency Division Multiplexing (OFDM) is a robust multi-carrier modulation technique for high data rata wired/wireless transmission systems due to its good performance in multi-path channels. In this paper, a chaos-evolutionary programming (CEP) hybrid approach is proposed to achieve a minimum degradation of OFDM transmission over multi-path channels, taking into account, the Doppler effect...
In this paper, we analyze the performance of a dual- hop system with partial relay selection and feedback delay over Rayleigh fading channels in the presence of multiple identical interferers at the destination. Based on the new closed-form expressions for the cumulative distribution function of the effective signal-to-interference plus noise ratio, we present closed-form expressions for the outage...
The paper discusses the problem of location a mobile cellular terminal within an urban, multipath-rich environment, using available geographical information such as terrain and building maps. The method suggested in the paper is the use of ray tracing in order to characterize the propagation environment. The paper focuses on single antenna location, namely a trilateration — based algorithm and suggests...
Turbo codes with iterative decoding are known for its astonishing low bit error rate performance. In this paper, we investigate the performance of turbo super-orthogonal space-time frequency trellis code (TurboSOSTFTC) in orthogonal frequency division multiplexing (OFDM) system over frequency selective fading channels (FSC). The coding scheme is based on parallel concatenation of two SOSTTCs, interleaving...
This article investigates the efficacy of a joint-design of adaptive modulation and coding (AMC) at the physical (PHY) layer with an adaptive Rmax-truncated selective-repeat automatic repeat request (ARQ) protocol at the medium access control (MAC) layer to maximize the throughput of cooperative amplify-and-forward (CAF) relay networks under prescribed delay and/or error performance constraints. Specifically,...
RAKE receiver is a digital receiver that takes advantage of temporal diversity of a multipath channel in order to increase the average received signal to noise ratio (SNR). In this paper we will analyze the performances of RAKE receiver for ultra wideband system with pulse amplitude modulation and time hopping spreading technique. These ultra wideband (UWB) systems have low duty-cycle and they are...
This paper investigates how the temporal response and spatial fading statistics for mobile-to-mobile links in hilly and mountainous terrain depend on terrain variations. Fading statistics are generated from Monte Carlo simulations using several terrain databases. These simulations employ a computer code that accounts for diffraction over terrain obstacles and for non-specular scattering from terrain...
This is the second in a two-part series of papers on statistical performance analysis of a general cross-layer automatic repeat request (ARQ) cooperative diversity (ACD) system. In order to obtain the theoretical formulas of end-to-end performance parameters, we develop a time division multiple access (TDMA)-based absorbing Markov model to help find all possible transition probabilities of each transmission...
Overlap frequency-domain equalization (FDE) requires no cyclic prefix (CP) insertion. In this paper, a new minimum mean square error (MMSE) weight is derived for the overlap FDE. In the previous paper, the MMSE weight for overlap FDE is derived by approximating the IBI as a white Gaussian variable. However, the IBI is an independent colored noise. We derive a new MMSE weight by taking into account...
In this paper, a novel rapid varying doubly-selective channel estimator for OFDM systems has been proposed, in which channel is modeled by basis expansion model (BEM). Unlike traditional BEM channel estimation algorithms, in which the comb-pilot is used and the large path delay is not considered, the proposed algorithm uses firstly block-type pilot to estimate the BEM coefficients of fast-varying...
In this paper, we analyze the effective capacity gains of opportunistic spectrum-sharing with imperfect channel information. We consider that a secondary user may access the spectrum allocated to a primary user as long as the average interference power, inflicted at the primary's receiver as an effect of the transmission of the secondary user, remains below predefined power limits. We consider partial...
Under the scenario of an underlay cognitive radio network, we propose in this paper an adaptive scheme using switched transmit diversity and adaptive modulation in order to increase the spectral efficiency of the secondary link. The proposed bandwidth efficient scheme (BES) uses the scan and wait (SWC) combining technique where a transmission occurs only when a branch with an acceptable performance...
We address the analytical design of a communications system that seeks to provide timely safety information for drivers who are unaware of an imminent collision. We develop a model to characterize the delay requirements needed to prevent such collisions. By simultaneously addressing the multi-user interference and propagation effects such as path loss and fading, we then analytically derive the optimal...
Based on static outdoor channel measurements we evaluate the influence of a vehicle on the MIMO radio channel, from a base station antenna array, to a multiple antenna handset in the hand of a user placed inside a test car. The measurement scenario is chosen to mimic a 2.6 GHz (LTE) macro-cell urban or rural scenario with two locations and orientations of the car, one at an open parking lot with a...
Cooperative diversity employs relays to assist source-destination transmissions and has shown to improve link outage probability in multipath fading environments. In this paper, we model relay selection as a semi-Markov process to analyze the impact of relay selection overhead on throughput, delay, and jitter in a simple scenario. Results show that the selection overhead can significantly reduce benefits...
Different alternatives for uplink transmit diversity for HSUPA are being investigated in 3GPP. This paper compares the performance of two-antenna beamforming using closed loop feedback information against the baseline single antenna transmission. With beamforming, multiple transmit antennas are utilized and the UE transmitter applies a weight vector to the transmit antennas in order to amplify the...
This paper presents a framework for signal-level emulation of propagation effects over generalized fading channels at the scale of entire networks. Network emulation enables research into network- scale systems - which would otherwise be limited to low-fidelity network simulators and one-off field experiments - to use real radio hardware and realistic channel models. Our hardware and software architecture...
Underwater acoustic (UWA) communication researches continue to focusing on higher spectrum-efficiency. This paper proposes a low complexity spatial parallel transmitting scheme based on layered space-time coding and spectrum spreading, named LST-SS scheme, to increase spectrum efficiency of UWA communication systems. In this scheme, layered signals are spread by the spreading code. Detection of signals...
A space-time cooperative transmission scheme based on orthogonal space-time block codes (OSTBC) and single-carrier block transmission (SCBT) is proposed. The scheme can be applied to asynchronous cooperative transmission scenarios with any number of relay nodes. By simple linear combination and minimum-mean-square-error frequency-domain equalization (MMSE-FDE), the scheme can obtain full diversity...
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