Multiuser Massive MIMO Relaying With Mixed-ADC Receiver
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In this letter, a multiuser relay network with massive multiple-input multiple-output is investigated with mixed-analog-to-digital converter (ADC) at receiver. We first characterize the uplink achievable rate by deriving a tight approximation, which embraces the conventional unquantized system as a special case. Both power scaling laws at sources and relay are presented. It is validated that the performance loss due to low-precision ADCs can be compensated by increasing the number of antennas M, obeying a logarithmical scaling law, rather than by increasing the transmit power at sources and/or relay. We show that the performance suffers from a loss factor interpreted as a nominal effective resolution of the entire mixed-ADC structure. Simulation results verify our observations.Keywords:
Transmitter power output
Analog-to-digital converter
Successive approximation ADC
In the present paper, we propose a novel high-resolution analog-to-digital converter (ADC) for low-power biomedical analog front-ends, which we call the successive stochastic approximation ADC. The proposed ADC uses a stochastic flash ADC (SF-ADC) to realize a digitally controlled variable-threshold comparator in a successive-approximation-register ADC (SAR-ADC), which can correct errors originating from the internal digital-to-analog converter in the SAR-ADC. For the residual error after SAR-ADC operation, which can be smaller than thermal noise, the SF-ADC uses the statistical characteristics of noise to achieve high resolution. The SF-ADC output for the residual signal is combined with the SAR-ADC output to obtain high-precision output data using the supervised machine learning method.
Successive approximation ADC
Flash ADC
Analog-to-digital converter
Integrating ADC
Shaping
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This paper presents the modeling and simulation of a 833.33 kS/s, 51.279μW successive approximation register(SAR) Analog to Digital Converter(ADC) using 0.18μm CMOS technology that uses internally generated signal for approximation for low power applications. The ADC is powered by single supply voltage of 1V. In our scheme, comparator output time and bit settling time of the Digital to Analog Converter(DAC) are utilized to generate a signal level such that the next step of the conversion can take place. This model is significant for Globally Asynchronous Locally Synchronous(GALS) system integration.
Successive approximation ADC
Analog-to-digital converter
SIGNAL (programming language)
Shaping
Digital-to-analog converter
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We address the problem of linear mean square error (MSE) transmitter design for point-to-multipoint multiuser systems, where the transmitter is equipped with multiple antennas and each of the independent receivers has a single antenna. This downlink scenario is more difficult to handle than its uplink counterpart, since all users are coupled by transmit filters and powers. Our main result is to show that downlink and uplink share the same normalized MSE achievable region under a sum power constraint. Thus, the problem of downlink transmitter design can be solved by focusing on an equivalent uplink problem, which has a more suitable structure and allows for efficient algorithmic solutions. As application examples, we solve the problem of minimizing the maximal normalized MSE of all users (fairness), and the problem of minimizing the sum of all normalized MSE (overall efficiency).
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This article presents analysis design of area efficient segmentation analog to digital power successive approximation analog to digital converter. A 10-bit 10-kS/s successive approximation analog-to-digital converter (SAR ADC) is designed by using 0.18 µm CMOS technology. The SAR ADC has been designed by using the segmentation technique which employed two different digital to analog converter (DAC) architectures. The proposed DAC design shows significant reduction in terms of area and better linearity. The overall speed of the ADC has greatly reduced due to lower switching activity. The supply voltage used is 1.5 V. At 10-kS/s sampling rates, the total power consumption of the whole SAR ADC is equaled to 7 nW while for DAC alone is 2.7 nW.
Successive approximation ADC
Analog-to-digital converter
Digital-to-analog converter
Linearity
Shaping
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In heterogeneous networks (HetNets), due to transmit power disparity between macro and pico base stations (BSs), the conventional strongest downlink (DL) reference signal received power (RSRP) based user association results in high uplink (UL) interference. Such interference degrades the UL performance especially in terms of energy efficiency. In this paper, we propose Joint Uplink and Downlink User Association (JUDUA) that takes both the UL and DL energy efficiencies into consideration when deciding the serving BS for user equipments (UEs). JUDUA formulates user association optimization problem as a Nash bargaining problem aiming to maximize the sum of log-scale UL and DL energy efficiencies among all UEs. Simulation results demonstrate that JUDUA improves UL and DL energy efficiencies of UEs, which in turn boosts UL and DL system capacity, reduces UL transmit power compared with the conventional user association schemes.
Transmitter power output
Bargaining problem
Macro
Association (psychology)
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In this paper we propose how to control the uplink transmit power of a mobile station (MS) during soft handoff in order to reduce the error probability of downlink transmit power control command bit without macro diversity gain at the base station controller (BSC). The uplink transmit power control is based on uplink transmit power control commands from all base stations (BS) belonging to the active set. The proposed scheme can be applied to third generation mobile communication systems since an MS receives uplink (UL) transmit power control bits (TPCB) from its base stations and sends a downlink (DL) transmit power control bit (TPCB) to them.
Soft handover
Transmitter power output
Transmit diversity
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In this paper, distributed power allocation schemes are studied for amplify-and-forward (AF) cooperative relay networks, where only partial channel state information (CSI) is available at the source and relays. Aiming at minimizing the total transmit power while providing a target outage probability, a scheme is first investigated in which the source decides transmit power and a relay-forwarding threshold, and each relay makes individually the transmit decision based on the threshold and its own CSI. Then a single relay power allocation scheme is proposed to simplify the implementation complexity, in which only one relay is selected to forward messages. Simulation results illustrate the performance improvement of the proposed schemes.
Transmitter power output
Channel state information
Outage Probability
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Fractional power control (FPC) is the simplified version of open loop power control (OLPC) in long term evolution (LTE) that relies on downlink path loss information from base station (BS). This allows user equipment (UE) to decide which power to use for uplink transmission. However, asymmetric behavior of uplink and downlink transmission in crowded network might cause unfair transmit power estimation. This motivates our investigation of implementing uplink path loss and q-learning algorithm to enable UE to decide appropriate transmit power on its own. In this study we apply the concept of FPC into q-learning, enabling UE to find suitable transmit power with respect to uplink path loss. 3GPP uplink path loss model is exploited in our study. We compare outputs between our proposed method and FPC. . From simulation, we find out that DQL performs better as compared to fractional power control in terms of signal-to-interference-noise-ratio (SINR) with average increase factor of 3.5.
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While two-way relaying is a promising way to enhance the spectral efficiency of wireless networks, the imbalance of relay-user distances may lead to excessive wireless power at the nearby-users. To exploit the excessive power, the recently proposed harvest-then-transmit technique can be applied. However, it is well-known that harvest-then-transmit introduces uplink-downlink coupling for a user. Together with the co-dependent relationship between paired users and interference among multiple user pairs, wirelessly powered two-way relay network suffers from the unique pairwise uplink-downlink coupling, and the joint uplink-downlink network design is nontrivial. To this end, for the one pair users case, we show that a global optimal solution can be obtained. For the general case of multi-pair users, based on the rank-constrained difference of convex program, a convergence guaranteed iterative algorithm with an efficient initialization is proposed. Furthermore, a lower bound to the performance of the optimal solution is derived by introducing virtual receivers at relay. Numerical results on total transmit power show that the proposed algorithm achieves a transmit power value close to the lower bound.
Transmitter power output
Initialization
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