Energy-Efficient Resource Allocation for Uplink Multi-User MIMO SC-FDMA Systems
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In this paper, joint user pairing and resource allocation is investigated for improving energy efficiency of multiuser multiple-input-multiple-output (MU-MIMO) single-carrier frequency division multiple access (SC-FDMA) systems. We first formulate an optimization problem to maximize energy efficiency with the maximum transmit power constraint and restrictions of minimum rate requirements from multiple users. To reduce computational complexity, we divide the joint optimization problem into two subproblems: energy efficient power allocation and joint user pairing and resource block allocation. For these subproblems, we develop a suboptimal algorithm with low implementation complexity. Simulation results demonstrate that the proposed scheme can achieve significant energy efficiency gain compares with conventional schemes.Keywords:
Transmitter power output
Frequency-division multiple access
Resource Management
This paper considers the problem of jointly compensating carrier frequency offsets (CFOs) and in-phase/quadrature-phase (I/Q) imbalance effects in orthogonal frequency-division multiple-access (OFDMA) or single-carrier frequency-division multiple-access (SC-FDMA) systems. Specifically, we propose a widely-linear time-varying minimum mean-output energy compensation scheme, by deriving its data-dependent frequency-shift implementation. The performance of the proposed receiver is assessed by Monte Carlo computer simulations.
Frequency-division multiple access
Carrier frequency offset
Quadrature (astronomy)
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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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In this paper, we propose a hybrid multiple-access scheme which combines IDMA (interleave division multiple access) and OFDMA (orthogonal frequency division multiple access), named OFDMA-IDMA. The advantages of this scheme are analyzed and the probable application scenarios are discussed. A scheduling method for uplink based on convergence analysis techniques is also proposed to group users to share the same time-frequency resources effectively.
Frequency-division multiple access
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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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Orthogonal frequency division multiple access (OFDMA) and Single Carrier Frequency Division Multiple Access (SC-FDMA) are the two major multiple access schemes for 4G wireless communications. In long term evolution (LTE) the downlink multiple access scheme is based on OFDMA and the uplink multiple access scheme is based on SC-FDMA. In this letter, we derive the fundamental performance difference between OFDMA and SC-FDMA, and present the general performance comparison between them. Analytical results show that OFDMA performance upper bounds SC-FDMA in the sense of capacity. The conclusion is further confirmed by numerical results.
Frequency-division multiple access
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Integrated Sensing and Full-Duplex Communication: Joint Transceiver Beamforming and Power Allocation
In this paper, we investigate the beamforming design for an integrated sensing and communication (ISAC) system involved full-duplex (FD) communications. Specifically, an FD ISAC base station (BS) performs target detection and communicates with multiple downlink users and uplink users reusing the same time and frequency resources. We jointly optimize the downlink dual-functional transmit signal and the uplink receive beamformers at the BS and the transmit power at the uplink users. The problem is formulated to minimize the total transmit power of the system while ensuring the communication and sensing requirements. The downlink and uplink transmissions are tightly coupled, making the joint optimization challenging. To solve this intractable problem, we first determine the receive beamformers in closed forms with respect to the BS transmit beamforming and the user transmit power and then suggest an iterative solution to the remaining problem. We demonstrate via numerical results that the optimized FD communication-based ISAC leads to power efficiency improvement compared to conventional ISAC with HD communication.
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Transceiver
Duplex (building)
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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
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Transmit diversity
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orthogonal frequency division multiple access (OFDMA) and single carrier frequency division multiple access (SC - FDMA) are the two kinds of 4 g wireless multiple access scheme. In the long term evolution (LTE) downlink link access scheme based on OFDMA, at the same time, the uplink access scheme based on SC - FDMA. In this article, we deduced the OFDMA and SC - FDMA basic performance difference, and then demonstrates the comprehensive performance comparisons between them. Theoretical derivation results show that the system capacity is better than that of SC - FDMA OFDMA. Then, we use the numerical simulation results confirm the conclusion. Keywords: OFDMA SC - FDMA basic capacity of the uplink transmission
Frequency-division multiple access
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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.
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