Adaptive Power Control for 4G OFDMA Systems on Frequency Selective Fading Channels (original) (raw)
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Power control is an efficient technique to mitigate the effect of interference, combat the Near-Far problem and conserve the battery life. Thus, an effective implementation of different power control algorithms in cellular radio communication systems can offer a significant improvement in the Quality of Service (QoS) to all the users. In this paper, increasing system capacity and using frequency reuse concept at the same cell will be investigated. That is because of the use of a new Multi-Level Power Control (MLPC) Algorithm to enhance the network performance by the ability of using the available channels in an efficient way and mitigate the interference at the same cell. System simulations are used to compare the performance of the proposed algorithm with the traditional one which done using dense Monte Carlo simulations. In addition, the effects of some system model parameters are discussed.
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Spectral efficiency is important in designing wireless broadband communication systems. This paper investigates the problem of minimizing overall transmission power while maximizing the spectral efficiency in orthogonal frequency division multiple access (OFDMA) systems. Two adaptive power allocation schemes are presented to allocate transmission power to individual sub-carriers of each user in the downlink frequencyselective fading channels. The proposed algorithms are more
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In this papel; the perjiormunce of a multiuser wireless network using OFDM, combined with Power Control and Adaptive Beamforming for uplink transmission is presented. An adaptive power control algorithm is exploited to acheive the desired Signal to Noise and Inte#erence Ratio(SINR) at each subchannel and increase the power eflceincy of the mobile transmitter In the receiver side, the base station uses an antenna array to optimize the SNR-Power efJiceincy, and attenuate the inte@erence from other users dramatically. Therefore, we can achieve a better overall error probability with a@ed total power A distributed iterative algorithm is used to jointly update the transmission power and the beamformer weights at each subchannel so that it can converge to the optimal solution for both power and beamforming vectors at each subchannel. The algorithm uses only the interjierence measured locally by the transmitter Unlike most of the loading algorithms which optimize the bit distribution and subchannel power allocation for a single transmittel; this approach tries to optimize the power allocatoin and decrease the interference for the whole network.
Dynamic Allocation of Subcarriers and Transmit Powers in an OFDMA Cellular Network
IEEE Transactions on Information Theory, 2009
This paper considers the problem of minimizing outage probabilities in the downlink of a multiuser, multicell orthogonal frequency division multiple access (OFDMA) cellular network with frequency selective fading, imperfect channel state information, and frequency hopping. The task is to determine the allocation of powers and subcarriers for users to ensure that the user outage probabilities are as low as possible. We formulate a min-max outage probability problem and solve it under the constraint that the transmit power spectrum at each base station is flat. In particular, we obtain a subchannel allocation algorithm that has complexity O(L log L) in L, the number of users in the cell. We also consider suboptimal but implementable approaches with and without the flat transmit power spectrum constraint. We conclude that the flat transmit spectrum approach has merit, and warrants further study.
Multiuser OFDM with adaptive subcarrier, bit, and power allocation
IEEE Journal on Selected Areas in Communications, 1999
Multiuser orthogonal frequency division multiplexing (OFDM) with adaptive multiuser subcarrier allocation and adaptive modulation is considered. Assuming knowledge of the instantaneous channel gains for all users, we propose a multiuser OFDM subcarrier, bit, and power allocation algorithm to minimize the total transmit power. This is done by assigning each user a set of subcarriers and by determining the number of bits and the transmit power level for each subcarrier. We obtain the performance of our proposed algorithm in a multiuser frequency selective fading environment for various time delay spread values and various numbers of users. The results show that our proposed algorithm outperforms multiuser OFDM systems with static time-division multiple access (TDMA) or frequency-division multiple access (FDMA) techniques which employ fixed and predetermined time-slot or subcarrier allocation schemes. We have also quantified the improvement in terms of the overall required transmit power, the bit-error rate (BER), or the area of coverage for a given outage probability