Abstract
This paper studies the energy efficiency (EE) maximization for an orthogonal frequency division multiple access (OFDMA) downlink network aided by a relay station (RS) with subcarrier pairing. A highly flexible transmission protocol is considered, where each transmission is executed in two time slots. Every subcarrier in each slot can either be used in direct mode or be paired with a subcarrier in another slot to operate in relay mode. The resource allocation (RA) in such a network is highly complicated, because it has to determine the operation mode of subcarriers, the assignment of subcarriers to users, and the power allocation of the base station and RS. We first propose a mathematical description of the RA strategy. Then, a RA algorithm is derived to find the globally optimum RA to maximize the EE. Finally, we present extensive numerical results to show the impact of minimum required rate of the network, the user number, and the relay position on the maximum EE of the network.
Highlights
With rapid growth of multimedia services, requirements for high-speed wireless communications are growing fast
One of the main reasons behind this fact is that performance of Orthogonal frequency division multiple access (OFDMA) systems can be significantly improved by proper resource allocation (RA) when transmitter channel state information (CSI) is available [11,12,13,14,15,16]
In [30,31,32,33,34], the authors adopted more flexible transmission protocols and proposed EE maximized RA algorithms for downlink OFDMA networks when the total transmission power is constrained to be smaller than a prescribed value
Summary
With rapid growth of multimedia services, requirements for high-speed wireless communications are growing fast. When users lie outside the BS’s radio coverage, EE maximized RA problems for OFDMA networks using subcarrier-pair-based DF protocols have been addressed in [25,26,27,28,29] In these works, every subcarrier in the first time slot is paired with a subcarrier in the second time slot for the relay-aided transmission. In [30,31,32,33,34], the authors adopted more flexible transmission protocols and proposed EE maximized RA algorithms for downlink OFDMA networks when the total transmission power is constrained to be smaller than a prescribed value In this case, when the network reaches the maximum EE, the total communication rate might be too small to meet the needs of users.
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