• Annual Conference of KIPS
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• 2012.11a
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• pp.712-714
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• 2012

D2D(Device-to-Device) 통신은 이동통신망을 기반으로 동작할 경우 이동통신망의 자원을 재사용함으로써 주파수 자원사용의 효율성을 높일 수 있다. 그러나 D2D 통신 단말(DUE; D2D user equipment)이 이동통신망의 자원을 재사용하는 경우 동일자원을 사용하는 이동통신개체와 DUE 간 및 D2D 통신 쌍 간에 신호 간섭이 발생할 수 있어 이를 고려한 자원할당기법에 대한 연구가 필요하다. 본 논문에서는 다수의 DUE가 이동통신망의 상향링크 자원을 다중으로 재사용할 때 이동통신개체 및 DUE가 달성가능 한 주파수 효율을 고려하여 DUE에게 자원을 할당함으로써 셀 수율을 향상시킬 수 있는 자원할당 기법을 제안한다.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.2
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• pp.67-76
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• 2013

Under an imperfect channel estimation, a Device-to-Device (D2D) communication framework based on MIMO relay technology is presented. The model consists of a D2D pair equipped with M antennas and a relay equipped with N antennas as well as a cellular user equipped with M antennas. The outage probability under different relaying protocols (i.e. AF and DF protocol) with and without considering a direct link was derived. The actual and theoretical outage probability of the five links under different antenna numbers was emulated. The number of user antennas and channel estimation error was analyzed carefully to determine their impact on the outage probability of a system. The simulation verified the theory analyses and the results showed that MIMO relaying improves the D2D communication system performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.4
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• pp.229-239
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• 2013

Recently, device-to-device (D2D) communications have been highlighted to improve the spectral efficiency and offer various user experiences in cellular networks. In this paper, we survey standards and literatures related to the D2D technology and address various advantages of D2D technology, and the problems to be resolved before practically implemented. Especially, by considering an important interference issue between cellular and D2D links, five resource allocation and interference management scenarios are provided and their performances are evaluated through the system level simulations. The simulation results show that the use of D2D significantly improve the cell capacity and the D2D user rate due to the effects of frequency reuse and data off-loading. Notably, it is also shown that an optimal D2D communication range exists to maximize the system performance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.2
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• pp.9-16
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• 2012

In this paper, the beamforming and user scheduling scheme for device-to-device (D2D) underlaying celullar networks with partial channel state information is investigated. In the proposed scheme, cellular users whose channels are nearly orthogonal to the channel between base station and D2D receiver are selected for unitary beamforming so as to minimize the interference to the D2D receiver. The interference caused by underlaying D2D communication can be minimized by reducing the D2D transmitter's transmission power. To enhance the cellular users' throughput further, we also investigate codebook generation method in which each code vector belongs to multiple unitary code matrices. From simulation results, we show that the proposed beamforming and user scheduling scheme mitigates D2D interference to the cellular networks and the codebook generation method improves cellular users' throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.12
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• pp.729-738
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• 2014

In this paper, we propose interference avoidance resource allocation scheme based on graph-coloring algorithm to introduce performance gain using spatial reuse in D2D (Device-to-Device) system. By assigning multiple D2D pairs to a single D2D resource, interference from neighboring D2D pairs is inevitable, which leads to performance degradation. Therefore, we first introduce the feedback information and the method considering the amount of information that can be practically provided by a D2D pair. Then, we propose how to construct a graph, which is corresponding to the D2D system, using the feedback information and adopt a graph-coloring algorithm to efficiently avoid interference. Simulation results show that the proposed resource allocation scheme outperforms traditional resource allocation schemes in both overall sum rate and spectral efficiency of D2D system while reducing the outage probability. Moreover, the outage probability, which indicates a failure rate of D2D communication, can be reduced by adopting the proposed scheme.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.1
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• pp.55-61
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• 2011

In this paper, the outage probability of device-to-device (D2D) uplink communication underlaying cellular networks is analyzed over Rayleigh fading. We assume that a D2D pair and M cellular user equipments share the same frequency resources. To prevent any harmful interference from a D2D transmitter to the BS, the maximum transmit power of the D2D transmitter is strictly limited. Under these assumptions, the outage probability is represented as a function of the interference-to-signal ratio from M cellular user equipments to a D2D receiver and the number of cellular user equipments, M. In addition, the interference-to-signal ratio is represented as a function of distances among D2D equipments, cellular user equipments and the BS. Simulation results validate these analytical results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.1
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• pp.211-232
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• 2024

In this paper, we consider the resource allocation and offloading decisions of device-to-device (D2D) cooperative UAV-assisted mobile edge computing (MEC) system, where the device with task request is served by unmanned aerial vehicle (UAV) equipped with MEC server and D2D device with idle resources. On the one hand, to ensure the fairness of time-delay sensitive devices, when UAV computing resources are relatively sufficient, an optimization model is established to minimize the maximum delay of device computing tasks. The original non-convex objective problem is decomposed into two subproblems, and the suboptimal solution of the optimization problem is obtained by alternate iteration of two subproblems. On the other hand, when the device only needs to complete the task within a tolerable delay, we consider the offloading priorities of task to minimize UAV computing resources. Then we build the model of joint offloading decision and power allocation optimization. Through theoretical analysis based on KKT conditions, we elicit the relationship between the amount of computing task data and the optimal resource allocation. The simulation results show that the D2D cooperation scheme proposed in this paper is effective in reducing the completion delay of computing tasks and saving UAV computing resources.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.11
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• pp.1511-1517
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• 2018

Mobile Device-to-Device (D2D) caching networks can transmit multimedia data to users directly without passing through any network infrastructure by storing popular multimedia contents in advance that are popular among many mobile users at caching server devices (CSDs) in distributed manners. Thus, mobile D2D caching networks can significantly reduce backhaul traffic in wired networks and service latency time of mobile users. In this paper, we propose an efficient transmission scheme that can enhance the transmission efficiency of mobile D2D caching networks by using multiple CSDs that are caching the contents that are popular among mobile users. By sorting the multiple CSDs that are caching a content that mobile users want to receive according to their channel gains, the proposed scheme can reduce the complexity of algorithm significantly, compared to an optimal scheme based on Brute-force searching, and can also obtain much higher network transmission efficiency than the existing Blanket and Opportunistic transmission schemes.

• International Journal of Computer Science & Network Security
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• v.21 no.1
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• pp.152-161
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• 2021

The paper focuses on Device-to-device (D2D) Architectures evaluation frameworks. D2D communication and discovery can improve spectrum usage efficiency and optimize the tradeoffs between throughput and energy consumption. The target operation modes involve both indirect communication between two nodes via a base station or the direct communication among proximal nodes, enabling use cases that can support communications out of cellular coverage, as well as low end-end delay requirements. The paper will present the architectural evolution of D2D networks within 3GPP standardization and will highlight key network functionalities and signaling protocols. It will also identify key analytical and simulation models that can be used to assess the performance and energy efficiency of resource allocation strategies, and it will present a suitable cross-layer integrated framework.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.83-88
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• 2016

We treat device-to-device direct communication (D2D) by reusing cellular uplink resources in LTE-Advanced systems. Conventional schemes assume that D2D transmitter employs SC-FDMA scheme for the date transmission. In the conventional schemes, however, it is very difficult to reduce the interference between the users, D2D communication cannot be used when the interference caused by cellular uplink signal is high. In this paper, we propose D2D transmission scheme which employes MC-CDMA technology and D2D detection scheme which uses MMSE algorithm to reduce interference from the cellular uplink signal. Therefore, in the proposed scheme the D2D communication becomes possible even in the high interference scenario. Through simulation, we show that the proposed scheme has better BER performance than the conventional scheme.