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A precise knowledge of the electromagnetic receiving characteristics of the antenna is mandatory for a precise determination of the directions of the impinging signals. For circular arrays the phase-mode description is an effective way of approximating the receiving characteristics of the antenna elements. For antenna elements, which are mounted in front of a cone-shaped reflector, angular ranges...
To overcome performance degradation in mobile multiple input multiple output (MIMO) orthogonal frequency-division multiplexing (OFDM) spatial multiplexing downlink systems an improved channel estimation algorithm is proposed. It yields channel estimates after every OFDM symbol reflecting time-variant channel behavior and provides data with approx. 4 bit/s/Hz for a 4??4 MIMO setup due to a decision...
Having the channel state information of the channels over which the signals propagate from the transmitter to the receiver available at both sides of the transmission link is beneficial in many wireless applications. However, in frequency division duplex systems, a base station can only estimate the channel transfer function of the uplink channel based on the transmission of a-priori known training...
In this paper, the downlink power control problem in decentralized orthogonal frequency division multiple access (OFDMA) networks is addressed. First, the optimization problem which minimizes the overall transmission power subject to individual rate and power constraints in a decentralized network is considered. An optimal solution requires global link information. However, obtaining such information...
The following topics are dealt with: information theory; coding; MIMO systems; OFDM systems; antennas; telecommunication channels; relaying; channel estimation; protocols; wireless networks; resource management; beamforming; and multiuser systems.
In this paper, we propose a novel optimization-based pre-equalization filter (PEF) design for multiple-input single-output (MISO) direct-sequence ultra-wideband (DS-UWB) systems with pre-Rake combining. The key feature in our design is that we explicitly take into account spectral mask constraints which are usually imposed by telecommunications regulation and standardization bodies. This avoids the...
In this paper, an adaptive multiuser OFDMA system in the downlink with multiple antennas at the transmitter and the receivers is investigated which serves two sets of users differing in their priority regarding channel access. At the transmitter either Transmit Antenna Selection (TAS) or Orthogonal Space Time Block Coding (OSTBC) is performed. In addition, Maximum Ratio Combining (MRC) is performed...
In this paper we consider a two-way relaying system with two sources A, B and one relay R, where the two sources desire to exchange information through the relay. The transmission consists of two states: multiple access (MAC) stage, where A and B transmit the channel-coded signals to R simultaneously, and broadcast (BC) stage, where R transmits towards both A and B. One critical process at R is to...
We consider the interference channel with two transmit-receive pairs when there is a delay in receiving the desired message compared to interference. We study this channel in the weak interference regime (noisy interference), and show that delay does not affect the capacity of the interference channel in this region. This also holds for an interference channel with a more general delay, where receiving...
Accurate and efficient spectrum sensing is a critical component of cognitive radio, which is a technology poised to improve dynamic resource management in future wireless networks. Autocorrelation exploitation has been shown to provide improvements in sensing performance over simple methods like energy detection. A new upper bound on the performance of autocorrelation-based detectors based on an NP...
This paper investigates the three-dimensional passive source localization problem by a system of multiple antenna arrays. It is well-known that centralized and coherent processing of all sensor antenna outputs offers a performance benefit in comparison to decentralized processing, where the latter is easier to implement. We compare the Crame??r-Rao bound on the source locations for both cases, review...
We apply the Monte-Carlo simulation model to a frequency selective fading channel including space-variance. This model is suited to simulate the performance of a multi-antenna system for a moving receiver (or transmitter). It takes into account that the time-variance of the channel due to this motion has its origin in the space-variance. We emphasize that for such a channel, time and frequency correlations...
Based on recent results for the vector broadcast channel (BC), the feasibility of the quality of service (QoS) optimization in the multiple-input multiple-output (MIMO) BC with linear precoders and linear equalizers is investigated. Based on the observation that only single data stream transmission must be considered for feasibility, we find that the test for feasibility is the comparison of the sum...
We consider the downlink of a cellular system based on the spatial channel model of the 3GPP MIMO urban macro cell with multiple antenna base stations and single antenna mobile devices. We analyze the impact of path-loss and intercell interference and classify mobile devices according to their location in a cell. We discuss non-cooperative approaches for maximizing the network sum-rate and propose...
We analyze the outage probability of frequency domain minimum mean squared error turbo equalization over frequency-selective Rayleigh fading channels with exponential delay power profile. A correlation chart analysis is used to evaluate the convergence property of the iterative system. Based on the convergence characteristic of the equalizer and decoder, we derive a closed form approximation to the...
Motivated from results for the point-to-point block MIMO channels without channel knowledge, we investigate possible communication schemes for the non-coherent two-way relaying channel. We propose one construction where the code is constructed from packings in Grassmann manifolds and evaluate the performance of the coding scheme.
The application of space-time/frequency coding is an interesting means to mitigate fading effects in terrestrial channels. Therefore, the well-known Alamouti scheme was introduced to the DVB-T2 standard. However, there have not been any measurements so far analysing the achievable gains using MIMO-schemes for broadcasting in UHF channels. Thus, extensive measurements have been performed. The obtained...
A dynamic system level simulator for LTE networks was developed for investigating the interference behaviour of femtocells placed within macrocells. We simulate a multi-cell, multi-user and multi-carrier system in the downlink for Single-Input, Single-Output (SISO) and Multiple-Input, Multiple-Output (MIMO) antenna configurations.
R-dimensional parameter estimation problems are common in a variety of signal processing applications. In order to solve such problems, we propose a robust multidimensional model order selection scheme and a robust multidimensional parameter estimation scheme using the closed-form PARAFAC algorithm, which is a recently proposed way to compute the PARAFAC decomposition based on several simultaneous...
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