Abstract
In this paper, a trade-off metric of unified energy efficiency (EE) and spectral efficiency (SE) is investigated in orthogonal frequency division multiple access downlink networks. The weighted product of the EE and SE of users is adopted to balance EE and SE. A maximization problem of the minimum weighted utility is formulated, and the original problem is divided into two sub-problems; one is a subcarrier allocation (SA) problem, and the other is power allocation (PA). For the SA problem, a sub-optimal algorithm employing a search method is utilized. To solve the PA problem, quasi-concavity of the utility function with respect to total transmit power in the PA sub-problem is shown. Based on the quasi-concavity, an iterative search algorithm of the optimal PA is developed. Through simulations, the efficiency of the algorithm is examined.
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Notes
Because bandwidth B is a common factor in both SE and EE, it can be ignored in discussions on the trade-off between SE and EE.
\(\mathcal {A}\) denotes a set of subcarriers which are not allocated to any user in a given iteration, \({\mathcal {S}}^k\) is a set of subcarriers allocated to the kth user.
Without this step, no subcarrier can be allocated to some users in the process of the iterative algorithm.
In the algorithm, \(I_{max}\) is the maximum number of iterations, \(\epsilon _{t}\) denotes convergence tolerance of the outer loop, and \(t_l\) and \(t_u\) are low and upper bounds of t.
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This work was supported by the 2016 Yeungnam University Research Grant.
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Kim, S., Yu, H. Energy- and Spectral-Efficiency Trade-Off in OFDMA Downlink Channels. Wireless Pers Commun 96, 6355–6367 (2017). https://doi.org/10.1007/s11277-017-4481-z
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DOI: https://doi.org/10.1007/s11277-017-4481-z