• Journal of KIISE:Information Networking
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• v.28 no.3
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• pp.406-416
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• 2001

Single path routing schemes using dynamic routing metric amy find out the dynamic network status and recompute paths to keep the traffic from the highly loaded regions of the network. This type of routing approach, however, may lead to a routing oscillation, and further, it cannot exploit multi-paths that may frequently exist in the real network. We propose a multipath routing scheme with dynamic load balancing, called MP-DLB, which is capable of reducing the overhead incurred by the multipath routing with dynamic load balancing approach while taking advantage of the high routing performance provided by the approach. According to the analysis of Internet packet traces which show that a high percentage of network traffic is destined for a small number of networks, MP-DLB applies the multipath routing with dynamic load balancing only to a limited subset of all the destinations in the network. For the rest of the destinations, it applies traditional single path routing scheme. This approach may reduce overall routing overheads by limiting the number of destinations to apply the more complicated routing scheme while it can keep the routing performance high by providing efficient routing for the most significant traffic in the routing performance. A series of simulations are done to analyze the performance of MP-DLB. The simulation results show that MP-DLB may effectively cope with the congestion and achieve high routing performance by distributing traffic streams that are generated from varying sources and heading toward a specific hot destination over multi-paths.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.5
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• pp.424-434
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• 2017

In industrial wireless sensor networks, many applications require integrated QoS supporting. This paper proposes a reliable protocol for real-time monitoring in industrial wireless sensor networks. Retransmission is well-known to recover the transmission failure, however, this might cause the time delay to violate the real-time requirement. The proposed protocol exploits broadcasting feature of wireless networks and the temporal opportunity concept. The opportunities to relay the data packets are shared by the broadcasting feature and the temporal opportunity concept maximize the number of candidates in communication. Simulation results show that the proposed protocol is superior to the existing real-time protocols in term of real-time service and reliability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3C
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• pp.127-132
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• 2011

In this paper, we propose a cooperative communication scheme for high transmission efficiency and coverage extension under multipath fading environment of moving networks. The proposed scheme uses a Space-Time Block Code (STBC) for improvement of receiving performance by using virtual Multiple-Input Multiple-Output(MIMO) transmit diversity. It can also achieve faster transmission time than a conventional scheme by using virtual MIMO configurations. Simulation results have shown that the proposed scheme provides SNR improvement and has faster transmission time compared to the conventional scheme, since it can utilize the good properties of spatial diversity and coding gain by using virtual MIMO configuration. In this paper, we propose simulations of UWB communication system to show validity by using the MATLAB.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2008.10b
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• pp.449-454
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• 2008

Finding an energy efficient route is one of the very important issues in the wireless sensor networks. The route scheme should consider both of the energy level of sensor nodes and the number of hops at the same time. First of all, this paper proposes an optimum routes finding scheme (ORFS), which could be used in the sensor network routing protocols. The scheme uses an optimum value for the path with the considerations of both the minimum energy level of a path and the number of hops at the same time. After that, this paper proposes a routing protocol based on the ORFS for how it could be used for the multipath directed diffusion with data aggregation (MDD-A), to get the better energy efficiency. The analysis result shows that the proposed routing protocol could lengthen the network life cycle about 18.7% compared to the previous MDD-A related protocols.

• Journal of Communications and Networks
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• v.17 no.6
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• pp.656-664
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• 2015

This study analyzes the performance of power-line communications for sending open automated demand response (OpenADR) signals. In particular, we study main channel disturbances that can affect end-to-end communications and which have not been previously studied in detail. Our analysis takes into account physical phenomena, such as background and impulsive noise sources, channel attenuation, and multipath effects, and considers the physical, network, and applications layers of the communications structure. The performance of the physical layer is the basis for computing the packet error rate. In analyzing application performance, we focus specifically on the latency in several communication environments. If a channel is impaired only by background noise, latencies are less than 40 seconds. With the addition of impulsive noise in the channel, this value increases as long as 68 seconds. Using these figures, we find that power-line technology is more suitable for "slow" demand programs, such as day-ahead or day-of curtailments, rather than ancillary services markets, which require near-real-time communication.

• Journal of information and communication convergence engineering
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• v.10 no.3
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• pp.231-236
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• 2012

For real-time wireless sensor network applications, it is essential to provide different levels of quality of service (QoS) such as reliability, low latency, and fault-tolerant traffic control. To meet these requirements, an (m,k)-firm based real-time routing protocol has been proposed in our prior work, including a novel local transmission status indicator called local DBP (L_DBP). In this paper, a fault recovery scheme for (m,k)-firm real-time streams is proposed to improve the performance of our prior work, by contributing a delay-aware forwarding candidates selection algorithm for providing restricted redundancy of packets on multipath with bounded delay in case of transmission failure. Each node can utilize the evaluated stream DBP (G_DBP) and L_DBP values as well as the deadline information of packets to dynamically define the forwarding candidate set. Simulation results show that for real-time service, it is possible to achieve both reliability and timeliness in the fault recovery process, which consequently avoids dynamic failure and guarantees meeting the end-to-end QoS requirement.

• The Journal of the Korea Contents Association
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• v.7 no.9
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• pp.100-107
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• 2007

This paper proposes and efficient routing scheme named MP-DD(MultiPath-Direct Diffusion) which are simple enough to be applicable to the wireless sensor networks. Conventional DD(Direct Diffusion) uses only one optimal path, therefore it consumes more energy of specific nodes. MP-DD uses multiple path and has a information of hop upstream node in the direction of the base-station. Simulation results show that the proposed scheme can increase network survivability compared to conventional DD and EAR(Energy Aware Routing) schemes.

• Journal of Information Processing Systems
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• v.14 no.6
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• pp.1347-1360
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• 2018

Owing to limited energy in wireless devices power saving is very critical to prolong the lifetime of the networks. In this regard, we designed a cross-layer optimization mechanism based on power control in which source node broadcasts a Route Request Packet (RREQ) containing information such as node id, image size, end to end bit error rate (BER) and residual battery energy to its neighbor nodes to initiate a multimedia session. Each intermediate node appends its remaining battery energy, link gain, node id and average noise power to the RREQ packet. Upon receiving the RREQ packets, the sink node finds node disjoint paths and calculates the optimal power vectors for each disjoint path using cross layer optimization algorithm. Sink based cross-layer maximal minimal residual energy (MMRE) algorithm finds the number of image packets that can be sent on each path and sends the Route Reply Packet (RREP) to the source on each disjoint path which contains the information such as optimal power vector, remaining battery energy vector and number of packets that can be sent on the path by the source. Simulation results indicate that considerable energy saving can be accomplished with the proposed cross layer power control algorithm.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.319-327
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• 2003

We consider the problem of low-sampling rate high-resolution channel estimation and timing for digital ultrawideband (UWB) receivers. We extend some of our recent results in sampling of certain classes of parametric non-bandlimited signals and develop a frequency domain method for channel estimation and synchronization in ultra-wideband systems, which uses sub-Nyquist uniform sampling and well-studied computational procedures. In particular, the proposed method can be used for identification of more realistic channel models, where different propagation paths undergo different frequency-selective fading. Moreover, we show that it is possible to obtain high-resolution estimates of all relevant channel parameters by sampling a received signal below the traditional Nyquist rate. Our approach leads to faster acquisition compared to current digital solutions, allows for slower A/D converters, and potentially reduces power consumption of digital UWB receivers significantly.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.344-353
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• 2003

Ultra-wideband (UWB) technology is gaining increasing interest for its potential application to short-range indoor wireless communications. Utilizing ultra-short pulses, UWB baseband transmissions enable rich multipath diversity, and can be demodulated with low complexity receivers. Compliance with the FCC spectral mask, and interference avoidance to, and from, co-existing narrow-band services, calls for judicious design of UWB pulse shapers. This paper introduces pulse shaper designs for UWB radios, which optimally utilize the bandwidth and power allowed by the FCC spectral mask. The resulting baseband UWB systems can be either single-band, or, multi-band. More important, the novel pulse shapers can support dynamic avoidance of narrow-band interference, as well as efficient implementation of fast frequency hopping, without invoking analog carriers.