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Compressive sensing is a recent technique for estimating a sparse vector from a reduced number of observations. Several algorithms have been developed and studied in this context. However, the reduction of number of samples (or the sampling rate) is one aspect of compressive sensing. In fact, the quantization of the observations, which is generally unavoidable in practice (due to the analog-to-digital...
From first principles, we show that two non-isotropic radiators with a specific and uniquely determined far-field pattern can be modeled consistently as two uncoupled isotropic radiators, provided one is willing to accept a non-linear distortion of the geometry. This shows that the, per se, non-physical model of uncoupled isotrops can have physical meaning in correctly describing the behavior of special...
We consider the downlink of a cellular network with cooperating multiple antenna base stations. On the one hand, each base stations tries to serve its associated mobile devices optimally, on the other hand, they try to minimize the interference they cause. Both goals could be achieved, if the interference channels would be zero. An adaptive beamforming based interference mitigation can only be performed...
Efficient channel estimation for signal equalization and OPM based on short CAZAC sequences with QPSK and 8PSK constellation formats is demonstrated in a 224-Gb/s PDM 16-QAM optical linear transmission system.
Heterogeneous cellular networks where conventional macro cells are overlaid with low power consumer deployed femtocell base stations are in the process of being deployed for their benefits in terms of scale, economy, and spectral efficiency. However, when femtocells operate in closed access, the problem of coverage holes for macro users needs to be solved. This paper proposes a probabilistic power...
We investigate the throughput maximizing data transmission strategy of an energy harvesting node which is able to harvest and store energy for communication. Solar cell and rechargeable battery technologies have made such nodes feasible. In addition to the energy arrival process and the battery capacity limitation, the energy consumption of the circuits of the node also plays an important role in...
We consider the scheduling and resource allocation problem in the downlink of multicarrier systems where data is processed and transmitted in unit of packets. This involves the allocation of transmit power as well as time and frequency slots to packets generated by different service flows, which consequently have various lengths and allows for various latency time in delivery. An optimization to maximize...
We report on our investigation of the capacity region of a Gaussian multiple access channel with two independent transmitters for the case where the receiver's antenna spacing is very small (compared to the wavelength). In contrast to common belief, we find that a rectangular capacity region can be maintained even as the distance of the antennas approaches zero. Moreover, the size of the capacity...
In signal processing, system theory, and in information theory signals are either complex valued waveforms or sequences of dimensionless complex numbers. The “power” of such signals is usually said to be the squared magnitude of these complex numbers. In an electrical circuit, power is always the product of voltage and current, both present at a port, i.e., at a pair of terminals. Here we ask the...
We report on our investigation of the capacity region of a Gaussian multiple access channel with two independent transmitters for the case where the receiver's antenna spacing is very small (compared to the wavelength). In contrast to common belief, we find that a rectangular capacity region can be maintained even as the distance of the antennas approaches zero. Moreover, the size of the capacity...
In a frequency division duplex system with a base station equipped with multiple antennas, the base station relies on feedback of the channel state information of the users in order to perform user selection and transmit beamforming in the downlink. Nonetheless, it is usually assumed that the feedback link is noise-free, i.e. the base station has access to error-free feedback. In practice, however,...
Based on maximizing the sum of lower bounds derived for the uplink (UL) and the downlink (DL) rates with imperfect Channel State Information (CSI), overhead optimization i.e. finding the optimum lengths of the UL and DL pilots and feedback bits, is performed. Estimated CSI and quantized Channel Direction Information (CDI), which may be received erroneously, are available at the Base Station (BS) for...
For the Multiuser Multiple-Input Single-Output (MUMISO) system in a downlink (DL) scenario, we design a non-linear precoding scheme, namely the spatial Tomlinson-Harashima precoder (S-THP) based on the total mean squared error (MSE) criterion. The channel state information (CSI) available at the transmitter for the precoding is the quantized channel direction information (CDI) relayed back in a frequency...
The study of circuits and systems requires some basic reasoning with various equivalent interconnections of components like resistors, sources, ideal opamps, ideal transistors, short and open circuits…. Students should be able to handle a rich variety of such interconnections correctly and appropriately. Special components like nullators and norators bring in some valuable insights, flexibility and...
In this work a systematic methodology is presented to design optimum chip pulse shapes for DS-CDMA systems for timing synchronization. A nonlinear bi-objective problem with additional constraints is established. The derived optimum chip pulse shapes show significant improvement in timing synchronization performance.
The availability of the Channel State Information (CSI) at the transmitter is crucial for the precoder design in Multi-user Multiple Input Single Output (MU-MISO) systems. In Frequency Division Duplex (FDD) systems, CSI can be just available at the transmitter through a limited feedback channel [1], where we assume that each user estimates, normalizes, and finally quantizes its channel direction with...
In signal processing, system theory, an in information theory signals are either complex valued waveforms or sequences of dimensionless complex numbers. The »power« of such signals is usually said to be the squared magnitude of these complex numbers. In an electrical circuit, power is always the product of voltage and current, both present at a port, i.e., at a pair of terminals. Here we ask the question:...
In this contribution we propose a simple method of obtaining a perfect reconstruction (PR) FIR prototype filter starting from a given near-perfect reconstruction (NPR) prototype filter for complex modulated filter banks. Our method consists of two steps. First, we calculate the product of a pair of polyphase components that fulfill the PR conditions, and second, we search for spectral factors that...
We consider the minimization of the overall power consumption when communicating over a noisy single-input single-output channel while satisfying a certain throughput and error rate constraint. The total power dissipation includes the radiated power as well as the circuit power consumption. In the context of battery operated short range communication, where low power, low cost and small size are key...
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