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A hybrid system of cellular mode and device-to-device (D2D) mode is considered in this paper, where the cellular uplink resource is reused by the D2D transmission. In order to maximize the overall system performance, the mutual interference between cellular and D2D sub-systems has to be addressed. Here, two mechanisms are proposed to solve the problem: One(More)
Device-to-device (D2D) communications have been proposed as an underlay to long-term evolution (LTE) networks as a means of harvesting the proximity, reuse, and hop gains. However, D2D communications can also serve as a technology component for providing public protection and disaster relief (PPDR) and national security and public safety (NSPS) services. In(More)
Cognitive radio makes it possible for an unlicensed user to access a spectrum unoccupied by licensed users. In cognitive radio networks, extra constraints on interference temperature need to be introduced into radio resource allocation. In this paper, the uplink radio resource allocation is investigated for OFDMAbased cognitive radio networks. In(More)
Cognitive radio makes it possible for an unlicensed user to access a spectrum unoccupied by the licensed user. In this paper, the resource allocation is investigated for OFDMA-based cognitive radio networks. Considering the characteristics of cognitive radio and OFDMA, an improved water-filling power allocation scheme is proposed under the interference(More)
This paper analyzes the maximum achievable transmission capacity of the D2D communication system under heterogeneous networks. The heterogeneous networks contain two primary systems working on independent bands and D2D communication guarantees the target outage probabilities of both systems on each band. By utilizing stochastic geometry, the effects of the(More)
In this letter, a power-control scheme for maximum sum-rate is proposed for the fading multiple access channels by considering the presence of primary users. Both the average transmit-power constraints and the peak interference-temperature constraints are considered. The interference caused by cognitive users must be under a pre-specified threshold for(More)
Cognitive radio makes it possible for an unlicensed user to access a spectrum unoccupied by licensed users. Efficient subcarricr and power allocation algorithm in CR networks is a challenging problem, especially for uplink. In this paper, an efficient multiuser water-filling algorithm is proposed under the interference temperature constraints. L'sing this(More)
Cognitive radio makes it possible for an unlicensed user to access a spectrum opportunistically. This paper addresses the problem of power control in cognitive radio networks, to maximize the system utility in the presence of interference temperature constraint. Penalty function is applied in the problem formulation to take into account the transmit power(More)
Cognitive radio makes it possible for an unlicensed user to access a licensed spectrum opportunistically on the basis of non-interfering. This paper addresses the problem of resource allocation for multiaccess channel (MAC) of OFDMA-based cognitive radio networks, taking into account of the interference temperature constraints. The objective is to maximize(More)
Device-to-device (D2D) communications as an underlay to cellular networks can not only increase the system capacity and energy efficiency, but it can also enable national security and public safety (NSPS) services. A key requirement is to provide access to cellular services when the network is available and maintain local communication in the (partial)(More)