• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권6호
• /
• pp.2240-2254
• /
• 2021

We investigate the channel allocation problem in an ultra-dense device-to-device (D2D) enabled cellular network in underlaying mode where multiple D2D users are forced to share the same channel. Two kinds of low complexity solutions, which just require partial channel state information (CSI) exchange, are devised to resolve the combinatorial optimization problem with the quality of service (QoS) guaranteeing. We begin by sorting the cellular users equipment (CUEs) links in sequence in a matric of interference tolerance for ensuring the SINR requirement. Moreover, the interference quota of CUEs is regarded as one kind of communication resource. Multiple D2D candidates compete for the interference quota to establish spectrum sharing links. Then base station calculates the occupation of interference quota by D2D users with partial CSI such as the interference channel gain of D2D users and the channel gain of D2D themselves, and carries out the channel allocation by setting different access priorities distribution. In this paper, we proposed two novel fast matching algorithms utilize partial information rather than global CSI exchanging, which reduce the computation complexity. Numerical results reveal that, our proposed algorithms achieve outstanding performance than the contrast algorithms including Hungarian algorithm in terms of throughput, fairness and access rate. Specifically, the performance of our proposed channel allocation algorithm is more superior in ultra-dense D2D scenarios.

• 한국컴퓨터정보학회논문지
• /
• 제23권8호
• /
• pp.51-57
• /
• 2018

In this paper, we investigate the impact of channel estimation error on the D2D power control algorithm. In the previous work, D2D power control algorithm has been proposed under the assumption that the channel between the transmitter and the corresponding receiver is perfectly estimated. In reality, the channel estimation error is more often the case. The first question is that the power control algorithm designed for perfect channel estimation is still valid under the channel estimation error environment ? The second question is, if it is not valid, what could be the possible remedy for the channel estimation error ? In this paper, to answer the first question, we investigate the impact of the channel estimation error on the power control algorithm. We first review the D2D power control algorithm designed for perfect channel estimation. Then, we model the channel estimation error. Finally, we summarize the main results observed from the analysis of the simulation.

• 한국통신학회논문지
• /
• 제36권5C호
• /
• pp.317-325
• /
• 2011

OFDM (Orthogonal Frequency Division Multiplexing) 시스템에서 2-D MMSE (2-Dimensional Minimum Mean Square Error) 채널 추정 기법은 주파수/시간 선택적 특성을 가지는 채널에서 우수한 성능을 나타내는 것으로 알려져 있다. 하지만 2-D MMSE 채널 추정 방식은 주파수 축 뿐만 아니라 시간 축 까지 고려하기 때문에 행렬 크기가 커지고, 이로 인해 복잡도가 크게 증가한다는 문제점이 있다. 따라서 본 논문에서는 이러한 문제점을 해결하기 위해 l-D MMSE 채널 추정 구조를 기반으로 가중치 합을 이용하여 기존의 2-D MMSE 채널 추정 방식보다 낮은 복잡도를 갖는 방식을 제안한다. 뿐만 아니라 2-D MMSE 채널 추정을 적용하기 위해 필요한 파라미터인 RMS 지연 확산과 도플러 주파수를 추정하는 기법을 고려한다. 성능 검증 결과 제안하는 방식은 기존의 2-D MMSE 방식에 비해서 복잡도를 크게 줄일 수 있을 뿐만 아니라, 2-D MMSE 채널 추정 방법과 유사한 성능을 나타내는 것을 확인하였다.

• Journal of Multimedia Information System
• /
• 제3권4호
• /
• pp.135-140
• /
• 2016

To improve the throughput of Device-to-Device (D2D) communication, we focus on the scenario where D2D pair can reuse multi-channel of cellular communication. However, as sharing same channel with cellular communication can cause interference between D2D communication and cellular communication, a proper interference management is needed. In this paper, we propose interference-based channel allocation to select the channels to be used by D2D communication and a solution from game theory perspective to optimize the D2D communication throughput under multi-channel as well as guarantee the interference from it to cellular network. The simulation results verify the stability of the proposed method.

• 한국정보통신학회논문지
• /
• 제12권2호
• /
• pp.260-268
• /
• 2008

본 논문에서는 MCVoD system의 VoD Server Channel 할당 기법 변경을 통한 성능향상에 대해 논하고, 이에 따른 MCVoD system의 전체 성능을 분석하도록 한다. 또한 시뮬레이션을 통해, 동일한 VoD Server Channel 할당 기법을 사용하는 타 VoD system과 성능을 비교해봄으로써, VoD Server 및 Interchange Agent의 동시 사용에 따른, MCVoD system성능을 평가한다.

• 한국컴퓨터정보학회논문지
• /
• 제25권5호
• /
• pp.65-72
• /
• 2020

본 논문에서는, 지난 연구에서 제안한 D2D 전력제어 알고리즘의 성능 개선을 위하여, 채널추정 에러를 보상하는 세 가지 수정 D2D 전력제어 알고리즘을 제안한다. 또한, 제안하는 세 가지 수정 D2D 전력제어 알고리즘을 채널추정 에러 환경에서 성능평가를 진행한다. 실제 채널환경에서는 채널추정 에러가 빈번하게 발생한다. 지난 연구에서는 채널추정 에러가 없는 환경을 가정하고 제안된 D2D 전력제어 알고리즘이 채널추정 에러 환경에서 성능 문제가 있음을 확인하었다. 세 가지 수정 D2D 전력제어 알고리즘은 1)재전송, 2)신호대 간섭비 여유, 3)재전송과 신호대 간섭비 병합을 기반으로 한다. 실험 결과 재전송과 신호대 간섭비 병합기법이 채널추정 에러를 보상하는 데 소모하는 전송전력과 지연 관점에서 가장 좋은 성능을 보임을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제16권8호
• /
• pp.2648-2665
• /
• 2022

Device-to-device (D2D) multicast has become a promising technology to provide specific services within a small geographical region with a high data rate, low delay and low energy consumption. However, D2D multicast communications are allowed to reuse the same channels with cellular uplinks and result in mutual interference in a cell. In this paper, an intelligent channel assignment algorithm is designed in D2D underlaid cellular networks with the target of maximizing network throughput. We first model the channel assignment problem to be a throughput maximizing problem which is NP-hard. To solve the problem in a feasible way, a novel channel assignment algorithm is proposed. The key idea is to find the appropriate cellular communications and D2D multicast groups to share a channel without causing critical interference, i.e., finding a channel for a D2D multicast group which generates the least interference to network based on current channel assignment status. In order to show the efficacy and effectiveness of our proposed algorithm, a novel search algorithm is proposed to find the near-optimal solution as the baseline for comparisons. Simulation results show that the proposed algorithm improves the network throughput.

• The Korean Journal of Physiology and Pharmacology
• /
• 제2권5호
• /
• pp.549-553
• /
• 1998

Using the planar lipid bilayer method, we investigated the effect of d-tubocurarine (dTC) on the extracellular side of large-conductance $Ca^{2+}-activated\;K^+$ channel from rat brain. When the initial open probability (Po) of the channel was relatively high, dTC decreased channel activity in a concentration dependent manner. In contrast, when the initial Po was lower, sub-micro molar dTC increased channel activity by destabilizing the closed states of the channel. Further addition of dTC up to micro molar range decreased channel activity. This dual effect of dTC implicates that there exist at least two different binding sites for dTC.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권3호
• /
• pp.1311-1324
• /
• 2019

In the traditional cellular network communication, the cellular user and the base station exchange information through the uplink channel and downlink channel. Meanwhile, device-to-device (D2D) users access the cellular network by reusing the channel resources of the cellular users. However, when cellular user channel conditions are poor, not only D2D user cannot reuse its channel resources to access the network, but also cellular user's communication needs cannot be met. To solve this problem, we introduced a novelty D2D communication mechanism in the downlink, which D2D transmitter users as half-duplex (HD) relays to assist the downlink transmission of cellular users with reusing corresponding spectrum. The optimization goal of the system is to make the cellular users in the bad channel state meet the minimum transmission rate requirement and at the same time maximize the throughput of the D2D users. In addition, i for the purpose of improving the efficiency of relay transmission, we use two-antenna architecture of D2D relay to enable receive and transmit signals at the same time. Then we optimized power of base station and D2D relay separately with consideration of backhaul interference caused by two-antenna architectures. The simulation results show that the proposed HD relay strategyis superior to existing HD and full-duplex (FD) models in the aspects of system throughput and power efficiency.

• 한국습지학회지
• /
• 제10권2호
• /
• pp.67-79
• /
• 2008

하천에서의 부정류 해석을 위해서 1차원 유한차분법(FDM)인 Abbott-Ionescu scheme과 2차원 유한체적법(FVM)인 근사의 Riemann solver(Osher scheme)에 대하여 살펴보았다. 두 모형은 직선 하도, 약간 굽어진 사행하도 및 사행하도에서의 흐름 문제들에 적용되었으며 결과의 비교는 균일한 직사각형 수로에 대하여 이루어졌다. 하천의 복잡한 형상의 표현하기 위해서는 이를 고려할 수 있는 유한체적법을 이용하였다. 유한차분법과 유한체적법 결과는 수위 및 유량 수문곡선에 대하여 매우 만족스러운 것으로 나타났다. 균일한 직선하도에 대해서는 1차원분석으로도 충분하다는 사실을 파악할 수 있었으며, 사행하도의 경우 흐름을 정확하게 모형화하기 위해서는 2차원 또는 3차원 모형을 사용하여야 할 것이다.