• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.17-26
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• 2013

ISO/IEC 29157 originally developed in the Republic of Korea and is based on commercially available PicoCast v1.0. ISO/IEC JTC1 SC6 was registered by the international standard on May 2010. A single platform for a variety of applications and media formats to support development objectives were. ISO/IEC 29157 based wireless networks, ie, Pico-net to master node periodically transmit sync signal is synchronized to the number of slave nodes have the communications structure. Pico-net also supports a variety of network topologies and direct communication between nodes(single-hop communication) and QoS is guaranteed. But Pico-net network structure has the following problems. Loss of communication problems due to mobile nodes, resulting in limitations of node mobility and wireless network operation range of conventional wireless networks operating range less than 1/4 was reduced to the problem. In this paper, a possible solution to the problems mentioned is proposed, using multi-hop communication technology and sync signal transmission technology between nodes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4B
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• pp.394-402
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• 2009

In this paper, we present a new analytical model for estimating the blocking performance of multi-fiber WDM networt:s with sparse and limited wavelength conversion (SLWC). The proposed model is a reduced-load approximation model that can obtain accurate estimates of blocking probability of such networks. Our model employs three new recurrence formulae to obtain the free wavelength distribution on a multi-fiber link, the free wavelength distribution after limited-range wavelength conversion and the end-to-end blocking probability of a multi-hop path, respectively. From the numerical results on the NSFNET, we demonstrate that the blocking performance of two-fiber NSFNET with three wavelength-convertible nodes, each of which translates an input wavelength to its adjacent output wavelengths, closely approximates the blocking performance of full wavelength conversion.

• Journal of the Korea Society of Computer and Information
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• v.14 no.11
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• pp.105-111
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• 2009

The study aims to propose the intelligent clustering technique that calculates the distance by improving the problems of multi-hop clustering technique for inter-vehicular secure communications. After calculating the distance between vehicles with no connection for rapid transit and clustering it, the connection between nodes is created through a set distance vale. Header is selected by the distance value between nodes that become the identical members, and the information within a group is transmitted to the member nodes. After selecting the header, when the header is separated due to its mobility, the urgent situation may occur. At this time, the information transfer is prepared to select the new cluster header and transmit it through using the intelligent cluster provided from node by the execution of programs included in packet. The study proposes the cluster technique of the intelligent distance estimation for the mobile Ad-hoc network that calculates the cluster with the Store-Compute-Forward method that adds computing ability to the existing Store-and-Forward routing scheme. The cluster technique of intelligent distance estimation for the mobile Ad-hoc network suggested in the study is the active and intelligent multi-hop cluster routing protocol to make secure communications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6A
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• pp.405-419
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• 2012

In this paper, we propose a joint base station(BS) and relay precoders design in multi-relay aided multi-user all-multiple-input multiple-output(MIMO) system. The design criterion is to minimize user sum mean square error(SMSE) with relay sum power constraint(RSPC) where only local channel state information(CSI)s are available at relays. Local CSI at a relay is defined as the CSI of the channel which the relay itself accesses, out of among all the 1st hop and the 2nd hop channel in the system. With BS precoder structure which is concatenated with block diagonalization(BD) precoder, each relay can determine its own precoder using only local CSI. Proposed scheme is based on sequential iteration of two stages; stage 1 determines BS precoder and relay precoders jointly with SMSE duality, and stage 2 determines user receivers. Proposed scheme can be demonstrated theoretically to be always converge. We verify that proposed scheme outperforms simple amplify-and-forward(SAF), MMSE relay, and proposed schemes in [1] in terms of both SMSE and sum-rate performances.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.4 s.346
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• pp.13-21
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• 2006

An mobile ad hoc network(MANET) is a collection of wireless computers (nodes), communicating among themselves over multi-hop paths, without the help of any infrastructure such as base stations or access points. Prior research in MANET has generally studied the routing problem in a non-adversarial setting, assuming a trusted environment. In this paper, we design and evaluate the Secure Zone Routing Protocol(T-ZRP), a secure ad hoc network routing protocol is based on the design of the hash chain. In order to support use with nodes of limited CPU processing capability, and to guard against Denial-of-Service attacks in which an attacker attempts to cause other nodes to consume excess network bandwidth or processing time, we use efficient one-way hash functions and don't use asymmetric cryptographic operations in the protocol. Proposed algorithm can safely send to data through authentication mechanism and integrity about routing establishment.

• Journal of Communications and Networks
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• v.6 no.3
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• pp.269-279
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• 2004

A new online multi-layer integrated routing (MLIR) scheme that combines IP (electrical) layer routing with WDM (optical) layer routing is investigated. It is a highly efficient and cost-effective routing scheme viable for the next generation integrated optical Internet. A new simplified weighted graph model for the integrated optical Internet consisted of optical routers with multi-granularity optical-electrical hybrid switching capability is firstly proposed. Then, based on the proposed graph model, we develop an online integrated routing scheme called differentiated weighted fair algorithm (DWFA) employing adaptive admission control (routing) strategies with the motivation of service/bandwidth differentiation, which can jointly solve multi-layer routing problem by simply applying the minimal weighted path computation algorithm. The major objective of DWFA is fourfold: 1) Quality of service (QoS) routing for traffic requests with various priorities; 2) blocking fairness for traffic requests with various bandwidth granularities; 3) adaptive routing according to the policy parameters from service provider; 4) lower computational complexity. Simulation results show that DWFA performs better than traditional overlay routing schemes such as optical-first-routing (OFR) and electrical-first-routing (EFR), in terms of traffic blocking ratio, traffic blocking fairness, average traffic logical hop counts, and global network resource utilization. It has been proved that the DWFA is a simple, comprehensive, and practical scheme of integrated routing in optical Internet for service providers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.9A
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• pp.801-808
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• 2011

We propose MBAP(Multi-rate Broadcast Active Probing) technique to get the right measurements for link quality in Wireless Mesh Network (WMN). Most routing protocols for WMN make use of link quality-aware routing metrics, such as ETX(Expected Transmission Count) and ETT(Expected Transmission Time), while the hop count is usually used in MANET (Mobile Ad-hoc NETwork). A broadcast based active proving technique is adopted in the previous studies to get the ETX or ETT of a link. However this technique does not reflect the multi-rate feature of WLAN because it uses a single fixed transmission rate for broadcast which usually differs from the actual rate used in data transmissions. MBAP overcomes this shortage by exploiting various rate broadcast frames for probing. We implement MBAP on linux system by modifying WLAN driver and related kernel sub-systems. Experimental results show that MBAP can capture link quality more accurately than the existing techniques.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6A
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• pp.555-567
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• 2010

Unlike single-hop systems, multi-hop systems that use relay nodes assign a part of the overall resources to relay communications. If efficient resource allocation schemes are not adopted, this leads to a loss of resources. Moreover, because we may not be able to guarantee high-link performance due to the adjacent-cell interference in relay-based cellular systems, resource efficiency can be severely decreased. In this paper, we propose efficient resource allocation schemes for downlink relay-based networks in 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution)-Advanced systems. Unlike conventional schemes that have static resource regions for each data link, the proposed schemes dynamically allocate the resources of each link to resource blocks, by considering the channel state and the capacity of each link. We also propose resource overlapping schemes in which two different links overlap at the same resource region, so as to improve cell or user throughput performance. The proposed resource overlapping schemes do not require additional processes such as interference cancellation in users, thank to considering additional interference from resource overlapping in advance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1C
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• pp.54-62
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• 2012

A Wi-Fi mesh network providing multi-hop wireless connections based on IEEE 802.11 PHY/MAC technology has recently received a significant attention as a network infrastructure that interconnects RFID systems and wireless sensor networks (WSNs). However, the current IEEE 802.11 contention-based MAC protocol cannot fully utilize the network capacity due to eithor frame collisions or unused network resources. In this paper, we propose a novel multi-channel scheduling MAC (MCS-MAC) protocol for Wi-Fi mesh networks. Under the secondary interference model of Wi-Fi mesh networks, the MCS-MAC protocol can maximize the network throughput via activation of collision-free links that has a maximal link weight. Through the simulations, we show that the throughput of the MCS-MAC protocol is at least three times higher than that of existing MAC protocols in Wi-Fi mesh networks.

• The Journal of the Acoustical Society of Korea
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• v.32 no.1
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• pp.86-94
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• 2013

In this paper, we propose a network coding scheme that is one of the most promising techniques for overcoming transmission errors in underwater acoustic communications. It is assumed that the proposed scheme operates in a Code Division Multiple Access (CDMA) network where multiple sensor nodes share the underwater acoustic channel in both the frequency and the time domains by means of orthogonal codes. The network topology deploys multi-hop transmission with relaying between multiple source nodes and one destination node via multiple relay nodes. The proposed scheme is evaluated in terms of the successful packet delivery ratio of end-to-end transactions under varying packet loss rates. A computer simulation shows that the successful delivery ratio is maintained at over 95% even when the packet loss rate reaches 50%.