Abstract
The joint scheduling of cellular and D2D communications to share the same radio resource is a complex task. In one hand, D2D links provide very high throughputs. In the other hand, the intra-cell interference they cause impacts on the performance of cellular communications. Therefore, designing algorithms and mechanisms that allow an efficient reuse of resources by the D2D links with a reduced impact on cellular communications is a key problem. In general, traditional Radio Resource Management (RRM) schemes (D2D grouping and mode selection) focus on finding the most compatible D2D pair for an already scheduled cellular User Equipment (UE). However, such approach limits the number of possible combinations to form the group (composed by a cellular UE and a D2D pair) to be scheduled in the radio resource. To overcome that, in this work a unified Joint Opportunistic Scheduling (JOS) of cellular and D2D communications, which is able to improve the total system throughput by exploiting the spatial compatibility among cellular and D2D UEs, is proposed. But more complexity is brought to the scheduling problem. Thus, a low-complexity suboptimal heuristic Joint Opportunistic Assignment and Scheduling (JOAS) is also elaborated. Results show that it is possible to reduce the computational complexity but still improve the overall performance in terms of cellular fairness and total system throughput with less impact on cellular communications.
Highlights
The joint scheduling of cellular and D2D communications to share the same radio resource is a complex task
B Y enabling direct and low-power communication among users, hereafter generally referred as User Equipments (UEs), Device-to-Device (D2D) communication leads to an improved spectrum utilization, system capacity and/or Quality of Service (QoS) levels; and at cell boundaries, D2D links may be used as relays to extend the coverage area [1], [2]
While some previous works in literature have pointed out that the overall capacity of a cellular network with underlayed D2D communications always outperforms the conventional cellular network, when cellular radio resources are reused by D2D communications in favorable conditions [1], [4], other works have proposed solutions to extend the range of situations in which D2D links are useful through Resource Management (RRM) schemes: D2D grouping, mode selection, and power allocation [5], [7], [8]
Summary
While some previous works in literature have pointed out that the overall capacity of a cellular network with underlayed D2D communications always outperforms the conventional cellular network, when cellular radio resources are reused by D2D communications in favorable conditions [1], [4], other works have proposed solutions to extend the range of situations in which D2D links are useful through RRM schemes: D2D grouping, mode selection, and power allocation [5], [7], [8]. Most of the proposed schemes for resource assignment of D2D communications have considered a pre-selected cellular UE [1], [4], [6], [7], such that the cellular scheduling runs independently of the establishment of D2D links. Since the instantaneous throughput information of all cellular UEs and D2D pairs must already be available within a cell for mode selection purposes, these measurements may be used instead in a unified framework for joint resource assignment of cellular and D2D communications. The optimization problem is decomposed into two subproblems: transmit power control for both cellular and D2D UEs, and joint mode selection and channel assignment for each D2D UE.
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