Abstract
Energy-efficient resource allocation is investigated for a relay-based multiuser cooperation orthogonal frequency division multiple access (OFDMA) uplink system with amplify-and-forward (AF) protocol for all relays. The objective is to maximize the total energy efficiency (EE) of the uplink system with consideration of some practical limitations, such as the individual power constraint for the users and relays and the quality of service (QoS) for every user. We formulate an energy-efficient resource allocation problem that seeks joint optimization of subcarrier pairing, relay selection, subcarrier assignment, and power allocation. Unlike previous optimization throughput models, we transform the considered EE problem in fractional form into an equivalent optimal problem in subtractive form, which is solved by using dual decomposition and subgradient methods. To reduce computation costs, we propose two low-complexity suboptimal schemes. Numerical studies are conducted to evaluate the EE of the proposed algorithms.
Highlights
Transmit diversity generally requires more than one antenna at the transmitter and receiver
Cooperation communication is a promising solution to address this problem in various wireless systems, such as ad hoc and cellular networks [1, 2]
The delay interval between adjacent taps is equal to the inverse of the OFDM system bandwidth
Summary
Transmit diversity generally requires more than one antenna at the transmitter and receiver. Cooperation communication is a promising solution to address this problem in various wireless systems, such as ad hoc and cellular networks [1, 2]. Cooperative communication formulates a new form of space diversity to combat the negative effect of severe fading [4]. Cooperative communication can improve the overall system performance by improving the spectrum efficiency, extending the coverage area, and prolonging the network lifetime. Orthogonal frequency division multiple access (OFDMA) or multiuser orthogonal frequency division multiplexing (MUOFDM) is the preferred multiple access scheme for highspeed wireless multiuser communication networks because of its high spectrum efficiency and resistance to multipath fading [5]. To improve system performance, studying optimal resource allocation in relayassisted OFDMA communication system is important
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