Abstract
Device-to-device (D2D) pairs are allowed to reuse the spectrum of cellular users who are in a good quality channel state with underlaying cellular network. However, cellular users usually suffer a poor performance in term of achievable rate when they are in a cell edge or in deep fading. To solve this problem, a hybrid relay-aided D2D communication scheme with a two-antenna infrastructure and using two unequal transmission slots is proposed in this paper. Different from the pure half-duplex and full-duplex D2D relay work, the hybrid-duplex relay mode that we propose enables the D2D relay to receive and transmit signals at the same time in the first time slot. Thus, it is similar to the full-duplex which could increase the spectrum efficiency. In addition, in the second time slot, the D2D relay will forward only the cellular user’s signals, thus avoiding the transmission of mixed signals which would deteriorate the system performance, similarly to the half-duplex mode. Moreover, by bringing in a slot splitting factor, the relay node in our hybrid-duplex mode is set to guarantee the matching of the transmission rate in two hops. We formulate the problem of maximizing the D2D transmission rate while guaranteeing in priority the minimum rate for the cellular user. By using the method of rate matching and linear programming, we deduce the expression of the slot splitting factor as well as the optimal power allocation for the base station and D2D relay, while guaranteeing the minimum rate requirement for the cellular user in a close form. The simulation results show that the proposed relay-based hybrid-duplex D2D scheme outperforms the existing half-duplex and full-duplex relay-based D2D communication schemes in term of achievable rate.
Highlights
In traditional cellular communication, cellular users transmit information through base stations to the core network
By bringing in a slot splitting factor, the relay node in our hybrid-duplex mode is set to guarantee the matching of the transmission rate in two hops
By using the method of rate matching and linear programming, we deduce the expression of the slot splitting factor as well as the optimal power allocation for the base station and D2D relay, while guaranteeing the minimum rate requirement for the cellular user in a close form
Summary
Cellular users transmit information through base stations to the core network. This architecture is encouraged to fulfill a ubiquitous coverage and efficient voice-oriented services [1]. How to use the limited spectrum and energy resources more effectively to improve the network capacity and improve users’ experience has become a hot topic in recent years. In response to these challenges, many solutions have been proposed by the academia and the industry to handle this explosive growth of mobile traffic in the next-generation communication network [3].
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