• Journal of Communications and Networks
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• 제10권2호
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• pp.204-212
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• 2008

We study the routing problem in all-wireless networks based on cooperative transmissions. We model the minimum-energy cooperative path (MECP) problem and prove that this problem is NP-complete. We hence design an approximation algorithm called cooperative shortest path (CSP) algorithm that uses Dijkstra's algorithm as the basic building block and utilizes cooperative transmissions in the relaxation procedure. Compared with traditional non-cooperative shortest path algorithms, the CSP algorithm can achieve a higher energy saving and better balanced energy consumption among network nodes, especially when the network is in large scale. The nice features lead to a unique, scalable routing scheme that changes the high network density from the curse of congestion to the blessing of cooperative transmissions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권8호
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• pp.3823-3840
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• 2017

This paper analyzes the nodes deployment optimization problem in energy constrained wireless sensor networks, which multi-hop cooperative beamforming (CB) based cooperative-multi-input-single-output (CMISO) transmission is adopted to reduce the energy consumption. Firstly, we establish the energy consumption models for multi-hop SISO, multi-hop DSTBC based CMISO, multi-hop CB based CMISO transmissions under random nodes deployment. Then, we minimize the energy consumption by searching the optimal nodes deployment for the three transmissions. Furthermore, numerical results present the optimal nodes deployment parameters for the three transmissions. Energy consumption of the three transmissions are compared under optimal nodes deployment, which shows that CB based CMISO transmission consumes less energy than SISO and DSTBC based CMISO transmissions. Meanwhile, under optimal nodes deployment, the superiorities of CB based CMISO transmission over SISO and DSTBC based CMISO transmissions can be more obvious when path-loss-factor becomes low.

• Journal of electromagnetic engineering and science
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• 제12권2호
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• pp.142-147
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• 2012

In this paper, we propose a novel protocol called Cooperative Multi-hop transmission using Incremental Relaying (CMIR). We evaluate the performance of the CMIR protocol by deriving expressions for the average end-to-end outage probability and the average number of transmissions. Monte Carlo simulations are presented to verify the accuracy of the theoretical analyses.

• 대한전자공학회논문지TC
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• 제48권1호
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• pp.45-49
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• 2011

협력적 다중 홉 통신은 열악한 무선 통선 환경인 수중 음향 네트워크 환경에서 보다 더 효율적인 통신을 제공한다. 그러나 이러한 협력적 다중 홉 통신은 초기 시간 구간에서 협력 노드 개수 부족으로 인하여 초기 노드에서 오류가 난 선호를 받을 확률이 높고, 오류 선호가 계속적으로 전송되므로 오류 확률증가가 예상된다. 이와같은 문제점을 해결하기 위하여 본 논문에서는 초기 시간 구간에서 파운틴 코드를 적용하여 성능을 개선시킬 수 있음을 모의실험을 통해 보인다. 또한 주파수와 거리에 따른 성능을 송신전력의 관점에서 보고 모의실험을 통해 성능을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권3호
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• pp.996-1015
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• 2016

A common concern regarding cooperative spectrum sensing (CSS) schemes is the occupied bandwidth and the energy consumption during the transmissions of sensing information to the fusion center over the reporting control channels. This concern is intensified if the number of cooperating secondary users in the network is large. This article presents a new fusion strategy for a CSS scheme, aiming at increasing the energy efficiency of a recently proposed bandwidth-efficient fusion scheme. Analytical results and computational simulations unveil a high increase in energy efficiency when compared with the original approach, yet achieving better performances in some situations, and lower implementation complexity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권7호
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• pp.2281-2301
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• 2014

In wireless ad hoc networks the nodes focus on achieving the maximum SINR for efficient data transmission. In order to achieve maximum SINR the nodes culminate in exhausting the battery power for successful transmissions. This in turn affects the successful transmission of the other nodes as the maximum transmission power opted by each node serves as a source of interference for the other nodes in the network. This paper models the choice of power for each node as a non cooperative game where the throughput of the network with respect to the consumption of power is formulated as a utility function. We propose an adaptive pricing scheme that encourages the nodes to use minimum transmission power to achieve target SINR at the Nash equilibrium and improve their net utility in multiuser scenario.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권3호
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• pp.1152-1167
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• 2018

In this paper, I propose an application layer cooperative congestion control scheme for safety message broadcast in vehicular networks, called CMS, that adaptively controls a vehicle's safety message rate and transmit timing based on the channel congestion state. Motivated by the fact that all vehicles should transmit and receive an application layer safety message in a periodic manner, I directly exploit the message itself as a means of estimating the channel congestion state. In particular, vehicles can determine wider network conditions by appending their local channel estimation result onto safety message transmissions and sharing them with each other. In result CMS realizes cooperative congestion control without any modification of the existing MAC protocol. I present extensive NS-3 simulation results which show that CMS outperforms conventional congestion control schemes in terms of the packet collision rate and throughput, especially in a high-density traffic environment.

• Journal of electromagnetic engineering and science
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• 제12권2호
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• pp.135-141
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• 2012

In this paper, we propose a novel cooperative routing protocol (NCRP) for wireless networks. The proposed protocol uses cooperative transmission to improve end-to-end outage probability. The broadcast nature ensures that the destination can receive a packet from the source or from the relays and if it cannot correctly decode the packet, the successful relays will start a retransmission. The NCRP protocol can skip some transmissions from the intermediate relays, thereby reducing the total power consumption. Theoretical results are derived and verified by simulation results.

• 대한전자공학회논문지TC
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• 제47권7호
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• pp.29-35
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• 2010

최근 3GPP LTE-Advanced 및 IEEE 802.16m과 같은 차세대 통신 규격에서 섹터 간 협력 전송이 중요 연구주제가 되었고, 그에 따라 기존 비협력 전송에서와 마찬가지로 섹터 간 협력 전송 시에도 최적의 안테나 틸팅 각도를 결정하는 방식의 필요성이 대두되고 있다. 본 논문에서는 섹터 간 협력 전송 및 비협력 전송 시 최적의 안테나 틸팅 각도를 결정하는 방식들을 제안한다. 제안하는 방식은 섹터 반경 내에 동일하게 분포하는 사용자의 전송률 평균인 셀 평균 전송률 또는 셀 평균 로그 전송률을 최대화하는 목적함수를 활용한다. 또한 이론적 용량인 Shannon 전송률 대신 실제 셀룰러 시스템에서 활용되는 AMC (adaptive modulation and coding) 방식을 고려한 셀 평균 AMC 전송률을 최대화하는 목적함수도 함께 활용한다. 협력 및 비협력 전송 시 셀 평균 전송률을 목적함수로 고려하는 경우에는 시스템 전송 효율성을 최대화 하며, 셀 평균 로그 전송률 및 AMC를 목적함수로 활용하는 경우에는 특히 셀 경계 사용자의 전송 효율성 증대를 크게 반영하는 최적의 안테나 틸팅 각도를 결정하는 방식을 제시한다.

• 한국인터넷방송통신학회논문지
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• 제13권4호
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• pp.17-22
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• 2013

본 논문에서는 레일리 페이딩 채널의 멀티 홉 협력 전송 프로토콜을 제안한다. 제안된 프로토콜에서, 멀티 홉 협력 전송은 시스템 성능의 향상을 위해 사용되었다. 중계라는 특성으로 인해, 전송받는 노드와 다음의 노드뿐만 아니라, 목적지와 그 사이의 전송 받는 모든 노드들이 제한되어 있지 않다. 제안된 프로토콜은 선택된 릴레이나 몇몇의 중간 노드로부터 건너 뛰어 전송되는 멀티 홉 직접 전송 프로토콜에 비해 평균 전송 전력을 절약할 수 있다. 제안하는 기법은 모바일 ad-hoc 무선 네트워크에서 시행 및 평가되어진다.