• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권4호
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• pp.1884-1903
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• 2019

Device-to-Device (D2D) communications can provide proximity based services in the future 5G cellular networks. It allows short range communication in a limited area with the advantages of power saving, high data rate and traffic offloading. However, D2D communications may reuse the licensed channels with cellular communications and potentially result in critical interferences to nearby devices. To control the interference and improve network throughput in overlaid D2D cellular networks, a novel channel assignment approach is proposed in this paper. First, we characterize the performance of devices by using Poisson point process model. Then, we convert the throughput maximization problem into an optimal spectrum allocation problem with signal to interference plus noise ratio constraints and solve it, i.e., assigning appropriate fractions of channels to cellular communications and D2D communications. In order to mitigate the interferences between D2D devices, a cluster-based multi-channel assignment algorithm is proposed. The algorithm first cluster D2D communications into clusters to reduce the problem scale. After that, a multi-channel assignment algorithm is proposed to mitigate critical interferences among nearby devices for each D2D cluster individually. The simulation analysis conforms that the proposed algorithm can greatly increase system throughput.

• 한국멀티미디어학회논문지
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• 제18권12호
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• pp.1468-1474
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• 2015

Efficient spectrum sharing is an important issue in Device-to-Device (D2D) communications underlaying cellular networks as it can mitigate the interference to cellular users and improve the performance of the systems. In this paper, we formulate the radio resource allocation in D2D communications as a mixed nonlinear integer programing. We show the formulated problem is NP-hard and thus a polynomial time algorithm to solve is not possible. Since such a problem is very hard to obtain the optimal solution within a short running time, we instead propose a fast heuristic suboptimal algorithm to mitigate the interference caused to cellular users and improve the performance of the systems. Simulation results are provided to evaluate the performance of the proposed algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권3호
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• pp.1057-1073
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• 2015

In this paper, we consider cooperative D2D communications in cellular networks. More precisely, a cellular user leases part of its spectrum to facilitate the D2D communication with a goal of improving the energy efficiency of a D2D pair. However the D2D pair is untrusted to the cellular user, such resource sharing may result in the information of this cellular user unsecured. In order to motivate the cellular user's generosity, this D2D pair needs to help the cellular user maintain a target secrecy rate. To address this issue, we formulate a joint spectrum and power allocation problem to maximize the energy efficiency of the D2D communication while guaranteeing the physical layer security of the cellular user. Then, a theorem is proved to indicate the best resource allocation strategy, and accordingly, an algorithm is proposed to find the best solution to this resource allocation problem. Numerical results are finally presented to verify the validity and effectiveness of the proposed algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권11호
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• pp.5209-5228
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• 2016

Device-to-device (D2D) communication underlaying cellular networks can bring significate benefits for improving the performance of mobile services. However, it hinges on elaborate resource sharing scheme to coordinate interference between cellular users and D2D pairs. We formulate a joint mode selection, link allocation and power control optimization problem for D2D communication sharing uplink resources in a multi-user cellular network and consider the efficiency and the fairness simultaneously. Due to the non-convex difficulty, we propose a three-step scheme: firstly, we conduct mode selection for D2D pairs based on a minimum distance metric after an admission control and obtain some cellular candidates for them. And then, a cellular candidate will be paired to each D2D pair based on fairness. Finally, we use Lagrangian Algorithm to formulate a joint power control strategy for D2D pairs and their reused cellular users and a closed-form of solution is derived. Simulation results demonstrate that our proposed algorithms converge in a short time. Moreover, both the sum rate of D2D pairs and the energy efficiency of cellular users are improved.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.1841-1865
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• 2017

This paper proposes a new interference mitigation scheme for device-to-device (D2D) communications underlaying a cellular network. The object of the proposed scheme is to determine the number of data streams, a precoding matrix, and a decoding matrix of D2D networks so as to maximize the system capacity given the number of data streams of a cellular network while satisfying the constraint of the inter-system interference from D2D networks to the cellular network. Unlike existing interference mitigation schemes based on the interference alignment technique, the proposed scheme operates properly regardless of the number of data streams of a cellular network and moreover it does not require changing the precoding and decoding matrices of a cellular network. The simulation results demonstrate that the proposed scheme significantly increases the system capacity by mitigating the intra- and inter-system interference.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권3호
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• pp.872-885
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• 2015

The rapid increase of smart mobile devices and mobile applications has led to explosive growth of data traffic in cellular network. Offloading data traffic becomes one of the most urgent technical problems. Recent work has proposed to exploit opportunistic communications to offload cellular traffic for mobile data dissemination services, especially for accepting large delayed data. The basic idea is to deliver the data to only part of subscribers (called target-nodes) via the cellular network, and allow target-nodes to disseminate the data through opportunistic communications. Human mobility shows temporal and spatial characteristics and predictability, which can be used as effective guidance efficient opportunistic communication. Therefore, based on the regularity of human mobility we propose NodeRank algorithm which uses the encounter characteristics between nodes to choose target nodes. Different from the existing work which only using encounter frequency, NodeRank algorithm combined the contact time and inter-contact time meanwhile to ensure integrity and availability of message delivery. The simulation results based on real-world mobility traces show the performance advantages of NodeRank in offloading efficiency and network redundant copies.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권9호
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• pp.4166-4182
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• 2018

We consider the Device-to-Device (D2D) communications in cellular networks where each cellular user (CU) shares the same resource with multiple D2D users (DUs). In this paper, we aim to maximize the energy efficiency (EE) of the D2D networks, subject to an interference constraint required by the CU. Since the cellular and D2D communications belong to different networks, we consider to incentivize base station (BS) while assisting the DUs. To this end, we propose a Stackelberg game based interference pricing framework for the considered D2D communications in cellular networks. Unlike most of the existing methods, we use interference pricing framework to jointly address the EE resource allocation problem and the interference management in our networks rather than only improve the EE of the DUs or protect cellular networks. In particular, BS and all the users do not need all channel state information, which is more realistic in practice. In addition, two different pricing strategies are also proposed. Based on the two strategies, we analyze the equilibrium of the game. Moreover, in the first strategy, the upper and lower boundaries of the interference price are obtained. The closed-form expression is gained with a backward induction for the second strategy. Both offer valuable insights to the considered scenarios. Finally, compared with the existing work, the EE of the D2D communications is significantly improved. The advantageous performance of our scheme are demonstrated by the simulation results.

• 한국통신학회논문지
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• 제38A권10호
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• pp.898-907
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• 2013

셀룰러 네트워크에서 D2D 통신을 지원하기 위해서는 기존의 셀룰러 통신과 D2D 통신이 셀룰러 자원을 공유하므로 주파수 효율성과 간섭에 대한 고려가 반드시 필요하다. 따라서 D2D 통신을 위한 자원할당은 셀룰러 통신과의 간섭을 최소화하면서 동시에 주파수 재사용에 따른 스펙트럼 이용 효율을 최대화하는 것이 바람직하다. 본 논문에서는 D2D 단말과 기지국이 상호 협력적인 방법으로 D2D 자원을 할당하는 기법을 제안한다. D2D 단말은 스펙트럼 센싱을 통해 셀룰러 단말과 다른 D2D 단말로부터 오는 간섭을 인지하여 최적의 셀룰러 자원을 선택하여 기지국에 보고한다. 기지국은 해당 셀룰러 단말과 D2D 단말이 동일한 자원을 공유하도록 자원할당을 함으로써 간섭의 영향을 최소화한다. 3GPP LTE (Long Term Evolution)-Advanced 환경에서 모의실험을 통해 제안한 자원할당 기법의 성능을 검증한다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2004년도 추계학술발표논문집(상)
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• pp.765-768
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• 2004

IEEE 802.110e는 실시간 트래픽의 QoS를 보장하기 위해 제안되었으나 cellular ip network 망에서 발생하는 route update packet과 같은 signaling traffic에 대해서는 아무런 언급을 하고 있지 않다. 따라서 본 논문에서는 IEEE 802.11e draft가 제안하고 있는 4가지의 AC(Access Category)에 따라 signaling traffic 에 대해서도 높은 우선 순위를 할당 함으로서 handoff시 발생하는 packet drop 이 얼마 만큼 줄어드는지를 분석하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권1호
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• pp.147-161
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• 2012

In recent years, machine-to-machine (M2M) communications are under rapid development to meet the fast-increasing requirements of multi-type wireless services and applications. In order to satisfy M2M communications requirements, heterogeneous networks convergence appears in many areas, i.e., mobile cellular networks (MCNs) and wireless sensor networks (WSNs) are evolving from heterogeneous to converged. In this paper, we introduce the system architecture and application requirement for converged MCN and WSN, where mobile terminals in MCN are acting as both sensor nodes and gateways for WSN. And then, we discuss the joint optimization of converged networks for M2M communications. Finally, we discuss the technical challenges in the converged process of MCN and WSN.