• Electronics and Telecommunications Trends
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• v.21 no.3 s.99
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• pp.91-99
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• 2006

중계기(relay station)는 기존의 이동통신 시스템에서 음영 지역 해소를 위해 도입되어 현재 사용중인 기술이다. 중계기 기술은 단순히 증폭 후 전달(amplify-and-forward)방식에서 디코딩 후 전달(decode-and-forward), 재구성/재조합 후 전달(reconfiguration/reallocation-and-forward) 등 지능화된 형태로 진화하고 있다. 특히, 차세대이동통신 시스템에서 지능화된 다수의 중계기 도입은 기지국 증설 비용과 백홀(backhaul) 통신망의 유지 비용을 줄이는 동시에 커버리지 확대와 데이터 처리율 향상을 위해 불가피할 것으로 예상된다. 이에 본 고에서는 중계기 방식과 종류 등 일반적인 사항에 대해 살펴보고, 최근 표준화 활동이 시작되어 이슈화되고 있는 IEEE 802.16MMR의 동향에 관해 기술한다.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.5
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• pp.510-516
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• 2010

In this paper, a dynamic GTS allocation method of wireless control networks is proposed for the use of factory automation using IEEE 802.15.4 MAC protocol. A superframe of IEEE 802.15.4 is applied to the transmission method of real-time periodic I/O data of wireless control systems within the limited time in factory environment. The method is proposed for efficient transmission of real-time periodic I/O traffic. The simulation results show the average network utilization and available I/O node numbers could be increased by the proposed method.

• Journal of Digital Contents Society
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• v.14 no.2
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• pp.191-197
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• 2013

To complete the "anywhere" mobile service there should not be shaded areas. However, it is never economical to deploy BS's (Base Stations) in a low population density area due to the low resource utilization. We propose a design technique to install RS's(Relay Stations) which are cheaper than BS's and find the condition in which the proposed technique is acceptible. The proposed design technique aims to allocate the frequency and time resources to RS's to minimize the transmission rate degradation due to interferences between RS's as well as to maximize the parallelism in transmission. We showed by simulation that the proposed technique achieves cost benefits when the expected traffic is less than 20.32 percent of the total BS capacity. The proposed technique is compatible with the IEEE 802.16j, thus can be extended to multi-hop configuration.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.3
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• pp.477-493
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• 2011

The IEEE 802.16 mobile multi-hop relay (MMR) task group 'j' (TGj) has introduced the multi-hop relaying concept in the IEEE 802.16 Wireless MAN, wherein a relay station (RS) is employed to improve network coverage and capacity. Several RSs can be deployed between a base station and mobile stations, and configured to form a tree-like multi-hop topology. In such architecture, we consider the problem of a path selection through which the mobile station in and outside the coverage can communicate with the base station. In this paper, we propose a new path selection algorithm that ensures more efficient distribution of resources such as bandwidth among the relaying nodes for improving the overall performance of the network. Performance of our proposed scheme is compared with the path selection algorithms based on loss rate and the shortest path algorithm. Based on the simulation results using ns-2, we show our proposal significantly improves the performance on throughput, latency and bandwidth consumption.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.1
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• pp.82-91
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• 2009

Routing (or path selection) is one of the key issues of multi-hop relay networks such as the IEEE 802.16j. Moreover, the allocation of appropriate resource such as bandwidth should not only be made in accordance with the paths selected, but the utilization of radio resource of an entire cell should also be maximized. Due to this interdependency between the problems of resource allocation and routing, it is desired these two problems are addressed simultaneously. In this paper, we propose a joint resource allocation and routing scheme for an OFDMA-based multi-hop cellular system. This scheme uses a polynomial time heuristic algorithm called Multi-Dimensional Multi-choice Knapsack Problem (MMKP) in order to find an approximate solution maximizing the total downlink throughput. In the simulation results, we show that the proposed scheme finds a sub-optimal solution which is superior to a link quality-based routing scheme, but slightly worse than the optimal solution.

• Journal of Communications and Networks
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• v.12 no.5
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• pp.466-474
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• 2010

Various types of cooperative relaying (CR) schemes exhibit different levels of throughput and outage performance because of their inherent trade-off between diversity gain and opportunity cost; in other words, the overhead that is associated with cooperation. This article attempts to answer whether cooperative communication is beneficial or not from the system-level viewpoint and furthermore, if it is, how its average throughput can be maximized while maintaining the target outage rate. In order to improve throughput at the required outage performance, we propose a unified selection criterion to deal with different levels of combining gain and opportunity cost associated with each scheme, which allows for the employment of different CR schemes for various positions of the mobile station. Our system-level simulation results for an IEEE 802.16j multi-hop relay confirm the varying levels of trade-offs among different CR schemes and furthermore, show that CR will be a useful means of maximizing the average throughput for a multi-hop relay system as long as each type of the cooperating scheme is carefully selected, depending on the position of the mobile stations.

• ETRI Journal
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• v.33 no.4
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• pp.558-568
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• 2011

In this paper, we propose an efficient macrodiversity handover (MDHO) technique for time-division-based interference-limited IEEE 802.16j multihop wireless relay networks. In the proposed MDHO, when the diversity set members of the mobile station (MS) are a base station (BS) and relay station (RS), the MS receives the signal transmitted by the BS in the first phase. During the second phase, it also receives the simultaneous transmissions of the BS and RS. Furthermore, when the diversity set members are two RSs or two BSs, the MS receives only the simultaneous transmissions of the diversity set members. The superiority of the proposed MDHO is validated using analytical and simulation results. The performance analysis metrics are the average downlink (DL) carrier to interference and noise ratio (CINR), the average DL spectral efficiency, and the average service outage probability. Evaluation results show that the proposed MDHO significantly outperforms the conventional MDHO. The CINR gain achieved using the proposed MDHO is 4.71 dB compared to the conventional MDHO.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.2
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• pp.223-234
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• 2008

Mobile multi-hop relaying (MMR) technology is being considered as a promising solution capable to enhance coverage, user throughput, and system capacity of the current wired backbone dependent wireless access networks. Since the relaying nodes do not need a wired backbone access, MMR technology offers easy and low-cost deployment, flexible cell planning, and adaptive traffic handling performance. In this paper, we investigate performance and cost effectiveness of the MMR technology deployment in the IEEE802.16j based WiBro/WiMAX systems. We first introduce standardization activities and research issues of MMR WiBro/ WiMAX systems. Since the coverage extension problem may occur in metropolitan areas as well as suburban or rural areas where user density is relatively low or moderate, we introduce several MMR topologies and analyze cost-effectiveness of MMR based coverage extension with respect to the user traffic density. Then, we argue cost effect on MMR technology deployment and throughput performance, Finally, we introduce further study issues including sectorized base station based MMR deployment approaches and the single and multi-frame structure MMR approaches.

• Electronics and Telecommunications Trends
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• v.23 no.3
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• pp.40-52
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• 2008

무선이동통신 시스템에서 셀 용량과 셀 영역을 확장하기 위한 기술로 Mobile Multi-hop Relay 기술에 대한 연구와 표준화 작업이 한창 진행되고 있다. 특히 고속으로 이동인터넷서비스를 제공할 수 있는 WiBro(Mobile WiMAX)에 적용할 수 있는 멀티홉기술이 IEEE 802.16j에서 표준화 작업이 진행되고 있다. 본 고에서는 IEEE 802.16j에서 추진되고 있는 멀티홉릴레이 기술에 대한 동향과 이에 소요되는 핵심기술에 대해서 소개하고자 한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.154-160
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• 2005

Microwave Otters are essential device in modem wireless systems. A compact dimension BPF(Band-pass Filter) for IEEE 802.11a WLAN service is realized using LTCC multi-layer process. To extrude 2-stage band-pass equivalent circuit, band-pass and J-inverter transform applied to Chebyshev low-pass prototype filter. Because parallel L-C resonator is complicate and hard to control the inductor characteristics in high frequency, the shorted $\lambda/4$ stripline is selected for the resonator structure. The passive element is located in the different layers connected by conventional via structure and isolated by inner GND. The dimension of fabricated stacked band-pass filter which is composed of six layers, is $2.51\times2.27\times1.02\;mm^3$. The measured filter characteristics show the insertion loss of -2.25 dB, half-power bandwidth of 220 MHz, attenuation at 5.7 GHz of -32.25 dB and group delay of 0.9 ns at 5.25 GHz.