• Journal of information and communication convergence engineering
• /
• 제14권1호
• /
• pp.14-20
• /
• 2016

The AODV protocol uses many RREQ messages and one RREP message in the path-discovery process. This protocol has only one metric, the number of hops. Although it is simple, this protocol is not efficient. To avoid this problem, we propose a new AODV with two auxiliary metrics (AuM-2-AODV). The AuM-2-AODV protocol tries multiple route replies, which reduces the chance of path failure and helps the network obtain a better data rate. It has two auxiliary metrics, the remaining energy of its nodes and the number of HELLO messages received at the nodes. With these two metrics, the reliable path from the source node to the destination node will be chosen. In this paper, the performance of the AuM-2-AODV is evaluated using the NS-3 simulator. The performance results show that AuM-2-AODV provides greater throughput and packet delivery ratio by 20% and up to 50% and about 100% in some cases, respectively, than previous protocols.

• 산업공학
• /
• 제15권3호
• /
• pp.247-255
• /
• 2002

For the recent multimedia service, the network should be fast, stable, and reliable. In order to provide reliability of the network, certain survivability of the network, which guarantees it's functions even though there is some failure on the network, should be satisfied. Also, for a pair of nodes on the network, there must be paths of which numbers of hops are within a certain limit for realtime service between them. In this paper, we propose a longest shortcut method for solving the survivable network design problems with hop limit. Through the computational results, we compare the efficiency of the method with an existing shortest shortcut method and find that the proposed method is more efficient than the shortest shortcut method.

• ETRI Journal
• /
• 제30권5호
• /
• pp.663-673
• /
• 2008

The multi-scenario topology of multi-channel hybrid ubiquitous sensor networks (USNs) is studied and a novel link auto-diversity cross-layer cooperative scheduling scheme is proposed in this paper. The proposed scheme integrates the attributes of the new performance evaluation link auto-diversity air-time metric and the topology space in the given multi-scenario. The proposed scheme is compared with other schemes, and its superiority is demonstrated through simulations. The simulation results show that relative energy consumption, link reception probability, and end-to-end blocking probability are improved. The addressing ratio of success with unchanged parameters and external information can be increased. The network can tolerate more hops to support reliable transportation when the proposed scheme is implemented. Moreover, the scheme can make the network stable. Therefore, the proposed scheme can enhance the average rate performance of the hybrid USN and stabilize the outage probability.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송공학회 2010년도 하계학술대회
• /
• pp.9-11
• /
• 2010

Multiple-input multiple-output (MIMO) systems assisted by multi-relays with single antenna are considered. Signal transmission consists of two hops. In the first hop, the source node broadcasts the vector symbols to all relays, then all relays forward the received signals multiplied by each power gain to the destination simultaneously. Unlike the case of full cooperation between relays such as single relay with multiple antennas, in our case there is no closed form solution for optimal relay power gain with respect to minimum mean square error (MMSE). Thus we propose an alternative approach in which we use an approximation of the cost function based on rank-one matrix decomposition. As a cost function, we choose the trace of MSE matrix. We give several simulation results to validate that our proposed method obtains a negligible performance loss compared to optimal solution obtained by exhaustive search.

• 한국정보통신학회논문지
• /
• 제9권2호
• /
• pp.402-407
• /
• 2005

주파수 합성기로서 통신시스템에 많이 사용되어온 PLL 방식은 여러 장점을 갖고 있지만, 위상잡음 특성이 나쁘고 주파수 도약 시간이 긴 단점을 갖기 때문에 최근의 고속(l$mu$s이하)으로 주파수 호핑(Frequency Hopping)을 요구하는 차세대 이동 통신 시스템에서는 사용이 불가능하다. 본 연구는 차세대 이동통신 시스템에서 1600 hops/s 속도로 600개 이상의 랜덤한 주파수를 발생하는 주파수합성기를 CPLD를 사용하여 DDS (Direct Digital Synthesis) 방식으로 설계하였다.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2000년도 추계종합학술대회
• /
• pp.176-179
• /
• 2000

통신회로에서 많이 사용되는 PLL 방식에 의한 주파수 합성기는 여러 장점이 있지만 위상잡음 특성이 나쁘고 긴 주파수 도약 시간을 갖기 때문에, 최근의 고속(1$\mu\textrm{s}$이하)으로 주파수 호핑(Frequency Hopping)을 요구하는 디지털 통신 시스템에서는 사용이 어렵다. 본 연구는 디지털 영상 패턴 발생기에서 1600hops/s로 600개 이상의 랜덤한 주파수를 발생하는 주파수합성기를 DDS (Direct Digital Synthesis) 방식을 이용하고, CPLD에 의해 구현하였다.

• 대한전자공학회논문지SD
• /
• 제39권5호
• /
• pp.41-45
• /
• 2002

비대칭 이중층 셔플넷 토폴로지를 멀티홉 WDM cross-connect 구현을 위하여 적용하였다. 그 결과로 필요한 WDM cross connect 수가 기존의 셔플넷 토폴로지 적용에 비하여 반으로 감소하며 이로 인하여 평균 흡수가 감소하고 평균 지연 시간을 줄일 수 있다.

• International journal of advanced smart convergence
• /
• 제1권2호
• /
• pp.34-38
• /
• 2012

The recent increase in use of the IEEE 802.15.4 standard for wireless connectivity in personal area networks makes of it an important technology for low-cost low-power wireless personal area networks. Studies showed that voice communications over IEEE 802.15.4 networks is feasible by Guaranteed Time Slot (GTS) allocation; but there are some constraints to accommodate voice transmission beyond two hops due to the excessive transmission delay. In this paper, we propose a GTS allocation scheme for bidirectional voice traffic in IEEE 802.15.4 multihop networks with the goal of achieving fairness and optimization of resource allocation. The proposed scheme uses a greedy algorithm to allocate GTSs to devices for successful completion of voice transmission with efficient use of bandwidth while considering closest devices with another factor for starvation avoidance. We analyze and validate the proposed scheme in terms of fairness and resource optimization through numeral analysis.

• Management Science and Financial Engineering
• /
• 제12권2호
• /
• pp.37-62
• /
• 2006

This paper considers the problem of designing logical tunnels in virtual private networks considering QoS guarantee which restricts the number of tunnel hops for each traffic routing. The previous researches focused on the design of logical tunnel itself and Steiner-tree based solution algorithms were proposed. However, we show that for some objective settings it is not sufficient and is necessary to consider both physical and logical connectivity at the same time. Thereupon, the concept of the layered network is applied to the logical tunnel design problem in virtual private networks. The layered network approach considers the design of logical tunnel as well as its physical routing and we propose a modified branch-and-price algorithm which is known to solve layered network design problems effectively. To show the performance of the proposed algorithm, computational experiments have been done and the results show that the proposed algorithm solves the given problem efficiently and effectively.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2001년도 춘계종합학술대회
• /
• pp.443-447
• /
• 2001

통신회로에서 많이 사용되는 PLL 방식에 의한 주파수 합성기는 여러 장점이 있지만 위상잡음 특성이 나쁘고 긴 주파수 도약 시간을 갖기 때문에, 최근의 고속(l$\mu\textrm{s}$이하)으로 주파수 호핑(Frequency Hopping)을 요구하는 디지털 통신 시스템에서는 사용이 어렵다. 본 연구는 디지털 영상 패턴 발생기에서 1600hops/s 로 600개 이상의 랜덤한 주파수를 발생하는 주파수합성기를 DDS (Direct Digital Synthesis) 방식을 이용하고, CPLD에 의해 구현하였다.