The Experts below are selected from a list of 23712 Experts worldwide ranked by ideXlab platform
Gerhard Fettweis - One of the best experts on this subject based on the ideXlab platform.
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energy efficient link adaptation with transmitter csi
Wireless Communications and Networking Conference, 2011Co-Authors: Christian Isheden, Gerhard FettweisAbstract:Energy-efficient link adaptation is studied based on minimizing the total energy consumption per transmitted bit in a mobile terminal. It is shown that the optimal power allocation is water-filling; the optimal energy consumption per bit is a function of the power Amplifier Efficiency, the circuit power rate dependence, and a cutoff channel to noise ratio (CNR). For a given transceiver architecture, low energy consumption per bit corresponds to a high cutoff CNR and vice versa. The optimization of the energy consumed per bit is carried out for flat fading and frequency-selective fading channels. In the former, the optimization problem is solved analytically, resulting in optimal rate, power and energy consumption per bit being expressed in terms of the cutoff CNR. In the latter, the optimal power allocation is water-filling in frequency, depending on the subcarrier noise levels. Finally, highly efficient algorithms with superlinear convergence are proposed, which are based on the Dinkelbach method for solving nonlinear fractional programs.
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energy efficient multi carrier link adaptation with sum rate dependent circuit power
Global Communications Conference, 2010Co-Authors: Christian Isheden, Gerhard FettweisAbstract:Energy-efficient link adaptation is studied for transmission on a frequency-selective parallel AWGN channel. The total power dissipation model includes a circuit power that varies with the sum rate and a power Amplifier Efficiency that varies with the bandwidth used. The mathematical analysis provides insight into how the subcarrier rates should be chosen for optimal energy Efficiency and suggests a simple fixed-point algorithm that finds the solution in few iterations. Moreover, ways of improving the energy Efficiency are discussed based on the dependence on bandwidth and distance between transmitter and receiver.
L E Larson - One of the best experts on this subject based on the ideXlab platform.
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rf power Amplifier Efficiency enhancement by envelope injection and termination for mobile terminal applications
IEEE Transactions on Microwave Theory and Techniques, 2013Co-Authors: Alireza Kheirkhahi, Jonmei J Yan, P M Asbeck, L E LarsonAbstract:An improved technique to enhance the Efficiency of the linear RF power Amplifiers (PAs) used in mobile terminal applications is proposed. The baseband load impedance is optimized, and the input envelope, along with the RF signal, is fed to the PA input. The resulting baseband modulation of the drain increases the saturated RF output power for a given dc power consumption. Digital predistortion is implemented to compensate for the linearity degradation. A 1.95-GHz heterojunction GaAs field-effect transistor PA, which in typical bias condition draws 100 mA from an 8.0-V supply and provides maximum power of 28 dBm for a continuous-wave input at 1.95 GHz, exhibits a significant improvement in peak power-added Efficiency from 40% to 56% for a two-tone input, from 33% to 42% for an uplink WCDMA with one dedicated physical data channel (DPDCH), and from 27% to 32% for an uplink WCDMA with six DPDCHs.
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design of h bridge class d power Amplifiers for digital pulse modulation transmitters
International Microwave Symposium, 2007Co-Authors: Tsaipi Hung, L E Larson, J Rode, P M AsbeckAbstract:This paper presents an H-bridge class-D power Amplifier (PA) for digital pulse modulation transmitters. The class-D Amplifier can be driven by two-or three-level digital signals generated by a delta-sigma modulator (DSM) and provides a linear microwave output after filtering. Within the Amplifier, the pull-up and pull-down devices are driven separately to improve the Amplifier Efficiency by minimizing the loss associated with shoot-through current. The H-bridge class-D PA system was tested with code-division multiple-access IS-95 signals at 800 MHz. Using binary DSM signals, a drain Efficiency of 31% was achieved with an output power of 15 dBm and an adjacent channel power ratio of -43 dBc. With three-level DSM signals, a drain Efficiency of 33% was achieved at same output power. An analysis of the factors governing Amplifier Efficiency is provided.
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a power re use technique for improved Efficiency of outphasing microwave power Amplifiers
IEEE Transactions on Microwave Theory and Techniques, 1999Co-Authors: R Langridge, P M Asbeck, T Thornton, L E LarsonAbstract:An improved power re-use technique is introduced for application to outphased microwave power Amplifiers. The technique allows a significant portion of the wasted out-of-phase components of the signal to be returned to the power supply, resulting in substantial improvements in overall power-Amplifier Efficiency. A peak re-use RF-to-DC Efficiency of 63% was obtained at 1.96 GHz.
Leila Musavian - One of the best experts on this subject based on the ideXlab platform.
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tradeoff analysis and joint optimization of link layer energy Efficiency and effective capacity toward green communications
IEEE Transactions on Wireless Communications, 2016Co-Authors: Leila MusavianAbstract:A joint optimization problem of link-layer energy Efficiency (EE) and effective capacity (EC) in a Nakagami- $m$ fading channel under a delay-outage probability constraint and an average transmit power constraint is considered and investigated in this paper. First, a normalized multi-objective optimization problem (MOP) is formulated and transformed into a single-objective optimization problem (SOP), by applying the weighted sum method. The formulated SOP is then proved to be continuously differentiable and strictly quasiconvex in the optimum average input power, which turns out to be a cup shape curve. Furthermore, the weighted quasiconvex tradeoff problem is solved by first using Charnes–Cooper transformation and then applying Karush–Kuhn–Tucker (KKT) conditions. The proposed optimal power allocation, which includes the optimal strategy for the link-layer EE-maximization problem and the EC-maximization problem as extreme cases, is proved to be sufficient for the Pareto optimal set of the original EE–EC MOP. Moreover, we prove that the optimum average power level monotonically decreases with the importance weight, but strictly increases with the normalization factor, the circuit power and the power Amplifier Efficiency. Simulation results confirm the analytical derivations and further show the effects of fading severeness and transmission power limit on the tradeoff performance.
Thomas Eriksson - One of the best experts on this subject based on the ideXlab platform.
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waveforms for the massive mimo downlink Amplifier Efficiency distortion and performance
IEEE Transactions on Communications, 2016Co-Authors: Christopher Mollen, Erik G Larsson, Thomas ErikssonAbstract:In massive multiple-input multiple-output (MIMO), most precoders result in downlink signals that suffer from high peak-to-average ratio (PAR), independently of modulation order and whether single-carrier or orthogonal frequency-division multiplexing (OFDM) transmission is used. The high PAR lowers the power Efficiency of the base-station Amplifiers. To increase the power Efficiency, low-PAR precoders have been proposed. In this paper, we compare different transmission methods for massive MIMO in terms of the power consumed by the Amplifiers. It is found that: 1) OFDM and single-carrier transmission have the same performance over a hardened massive MIMO channel and 2) when the higher Amplifier power Efficiency of low-PAR precoding is taken into account, conventional and low-PAR precoders lead to approximately the same power consumption. Since downlink signals with low PAR allow for simpler and cheaper hardware, than signals with high PAR, therefore, the results suggest that low-PAR precoding with either single-carrier or OFDM transmission should be used in a massive MIMO base station.
Christian Isheden - One of the best experts on this subject based on the ideXlab platform.
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energy efficient link adaptation with transmitter csi
Wireless Communications and Networking Conference, 2011Co-Authors: Christian Isheden, Gerhard FettweisAbstract:Energy-efficient link adaptation is studied based on minimizing the total energy consumption per transmitted bit in a mobile terminal. It is shown that the optimal power allocation is water-filling; the optimal energy consumption per bit is a function of the power Amplifier Efficiency, the circuit power rate dependence, and a cutoff channel to noise ratio (CNR). For a given transceiver architecture, low energy consumption per bit corresponds to a high cutoff CNR and vice versa. The optimization of the energy consumed per bit is carried out for flat fading and frequency-selective fading channels. In the former, the optimization problem is solved analytically, resulting in optimal rate, power and energy consumption per bit being expressed in terms of the cutoff CNR. In the latter, the optimal power allocation is water-filling in frequency, depending on the subcarrier noise levels. Finally, highly efficient algorithms with superlinear convergence are proposed, which are based on the Dinkelbach method for solving nonlinear fractional programs.
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energy efficient multi carrier link adaptation with sum rate dependent circuit power
Global Communications Conference, 2010Co-Authors: Christian Isheden, Gerhard FettweisAbstract:Energy-efficient link adaptation is studied for transmission on a frequency-selective parallel AWGN channel. The total power dissipation model includes a circuit power that varies with the sum rate and a power Amplifier Efficiency that varies with the bandwidth used. The mathematical analysis provides insight into how the subcarrier rates should be chosen for optimal energy Efficiency and suggests a simple fixed-point algorithm that finds the solution in few iterations. Moreover, ways of improving the energy Efficiency are discussed based on the dependence on bandwidth and distance between transmitter and receiver.