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In this contribution we study the impact of transmitter and receiver impairments on the throughput for MIMO and 64 QAM transmissions in an evolved HSDPA system. A simple additive white Gaussian noise model is used to model impairments in the transmitter and receiver chain. The investigation is performed through computer simulations both on link and system level. It is found that the impact from transmitter...
This paper deals with time-varying channel estimation in orthogonal frequency division multiplexing (OFDM) systems by means of pilot-aided strategies. A robust estimator which does not depend on the channel statistics is proposed. The derivation is based on a constrained filtering approach and particular cases are analyzed. Simulation results are provided in order to verify the better performance...
We propose a differential spatial multiplexing (SM) scheme based on complex square orthogonal designs, referred to as differential orthogonal spatial multiplexing (DOSM). The receiver of DOSM does not require estimation of channel fading coefficients, channel power, signal power, or noise power to decode the data symbols and the decision is based on the two consecutively received codewords. A constellation...
Multi-antenna systems provide advantages in terms of link quality and multiuser access capabilities, which can be achieved by using schemes as multibeam opportunistic beamforming. This scheme only requires partial channel state information at the transmitter (CSIT) in terms of the equivalent channel moduli. This paper deals with the problem of feeding back the CSI from the multiple receivers to the...
We propose a new signaling scheme for the multiple access channel (MAC) based on low-rate layered LDGM codes. The proposed scheme approaches the ergodic Rayleigh fading MAC capacity.
We consider the broadcast phase of a three-node network, where a relay node with multiple antennas establishes a bidirectional communication between the two other nodes each equipped with a single antenna using a spectrally efficient two phase protocol. In the first phase, both nodes transmit a message to the relay node, which decodes the messages. In the second phase the relay broadcasts a re-encoded...
This paper considers the transmission of a Reed-Solomon (RS) code over a binary modulated time-correlated flat Rician fading channel with hard-decision demodulation. We define a binary packet (symbol) error sequence that indicates whether or not an RS symbol is transmitted successfully across the discrete channel whose input enters the modulator and whose output exits the demodulator. We then approximate...
Interference management is one of effective means of improving system throughput, which is particularly important for the emerging 4G wireless networks that demand increasing data rates. In order to mitigate the inter-cell interference we evaluate the performance of an hierarchical centralized inter-cell scheduling method which aims at improving the system throughput. The proposed algorithm, which...
The purpose of this paper is to report on an unsuitable behavior of the constrained stochastic gradient (CSG) algorithm for adaptive beamforming in the combination of two events: one or more interference angles-of-arrival are close to the signal angle-of-arrival and the angle spreads of the involved signals are small. In this situation, the CSG algorithm stresses the co-channel interference minimization...
Future mobile communications radio networks, e.g. 3GPP long term evolution (LTE), will typically use an orthogonal frequency division multiplexing (OFDM) based air interface in the downlink. Furthermore, in order to avoid frequency planning, a frequency reuse factor of one is desirable. In this case, system capacity is limited by interference, which is particularly crucial for mobile terminals with...
We discuss approximate maximum likelihood methods for blind identification and deconvolution. These algorithms are based on particle approximation versions of the EM algorithm. We consider two different methods which differ in the way the posterior distribution of the symbols is computed. The first algorithm is based on a novel particle approximation method of the fixed-interval smoothing whereas...
An energy-efficient opportunistic collaborative beamformer with one-bit feedback is proposed for ad hoc sensor networks over Rayleigh fading channels. In contrast to conventional collaborative beamforming schemes in which each source node uses channel state information to correct its local carrier offset and channel phase, the proposed beamforming scheme opportunistically selects a subset of source...
This paper analyzes the connectivity of wireless ad hoc networks in both a non-cooperative scheme and a cooperative scheme. Assuming that nodes are randomly distributed with a Poisson process, the probability of full connectivity in a system can be raised by increasing the number of connectional trials at each node. Even though an infinite number of trials guarantee full connectivity in a system,...
Dynamic spectrum access (DSA) is an emerging notion in cognitive radio, aiming to improve the spectrum usage with reliable secondary access to the spectral resources. The main challenge in DSA is the detection of spectral opportunities and their efficient utilization without causing interference to the primary users. For this goal, we propose to make use of a reinforcement learning approach: the Multi...
An iterative joint decoding algorithm for data gathering wireless sensor networks is proposed in where the correlation between sensorspsila data is considered as a global code and iterative decoding is performed by concatenating the global decoder with the decoder of error correcting code applied to encode sensors observations. We apply this algorithm for sensor networks with binary CEO model where...
The practical use of any equalization scheme that relies on pilot-based channel estimates is often hindered by high computational requirements, especially in cases where a precise estimation criterion is crucial. The goal of this paper is to show that any pilot based scheme that is able to induce a Toeplitz structure in the channel correlation matrix, can make use of an existing class of so-called...
This paper studies the fluctuations of the post-processing SNR at the output of the linear MMSE receiver in (receive) correlated multiple input multiple output (MIMO) systems. Although it is known that asymptotically, the SNR behaves like a Gaussian random variable, this approximation may yield to inaccurate estimates for small dimension. In order to circumvent this, we use gamma and generalized gamma...
Bit error rate (BER) prediction over channel realisations has emerged as an active research area. In this paper, we give analytical signal to interference and noise ratio (SINR) evaluation of MIMO-OFDM systems using an iterative receiver. Using this analytical SINR expression, we propose an accurate BER prediction method based on effective exponential SINR mapping (EESM) method. We show by simulations...
Channel Division Multiple Access (ChDMA) is a promising multiple access scheme for Ultra-Wide Band (UWB) systems based on the use of the Channel Impulse Responses (CIR) as user signatures. In this work, we modeled the UWB-CIR as linear combinations of continuous impulses of finite duration randomly delayed. Two different channels are considered: the first, very simplistic, generates multipaths that...
In this paper, a low complexity blind synchronization algorithm is proposed for ultra wideband (UWB) communication systems in the multipath environment. Using the first order statistics of the received signal, the proposed algorithm is carried out without aided data. The synchronization parameter and nuisance ones are separated from each other on account of the structure of the Vandermonde matrix,...
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