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Joint Transmitter and Receiver Power Allocation under Minimax MSE Criterion with Perfect and Imperfect CSI for MCCDMA Transmissions
Chirawat KOTCHASARN Poompat SAENGUDOMLERT
Publication
IEICE TRANSACTIONS on Communications
Vol.E91B
No.6
pp.19701979 Publication Date: 2008/06/01 Online ISSN: 17451345
DOI: 10.1093/ietcom/e91b.6.1970 Print ISSN: 09168516 Type of Manuscript: PAPER Category: Wireless Communication Technologies Keyword: joint transmitter and receiver power allocation, nonlinear optimization, minimax optimization, robust optimization, semidefinite programming, bilinear matrix inequality, MCCDMA,
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Summary:
We investigate the problem of joint transmitter and receiver power allocation with the minimax mean square error (MSE) criterion for uplink transmissions in a multicarrier code division multiple access (MCCDMA) system. The objective of power allocation is to minimize the maximum MSE among all users each of which has limited transmit power. This problem is a nonlinear optimization problem. Using the Lagrange multiplier method, we derive the KarushKuhnTucker (KKT) conditions which are necessary for a power allocation to be optimal. Numerical results indicate that, compared to the minimum total MSE criterion, the minimax MSE criterion yields a higher total MSE but provides a fairer treatment across the users. The advantages of the minimax MSE criterion are more evident when we consider the bit error rate (BER) estimates. Numerical results show that the minimax MSE criterion yields a lower maximum BER and a lower average BER. We also observe that, with the minimax MSE criterion, some users do not transmit at full power. For comparison, with the minimum total MSE criterion, all users transmit at full power. In addition, we investigate robust joint transmitter and receiver power allocation where the channel state information (CSI) is not perfect. The CSI error is assumed to be unknown but bounded by a deterministic value. This problem is formulated as a semidefinite programming (SDP) problem with bilinear matrix inequality (BMI) constraints. Numerical results show that, with imperfect CSI, the minimax MSE criterion also outperforms the minimum total MSE criterion in terms of the maximum and average BERs.

