• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.478-490
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• 2015

Abundant data has been generated over the internet as the arrival of information age. To share the information, Wired, wireless network are required to transmit the data. Especially, In the wireless network which is using mobile device based on battery, energy consumption is growing due to uploading, downloading the abundant data on mobile device. In order to solve the problem, This paper addresses the protocol of the modified TCP congestion control that is being used for the most network protocol to save energy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.778-798
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• 2014

This paper proposes a novel exposed-terminal-eliminated medium access control (ETE-MAC) protocol by combining channel reservation, collision avoidance and concurrent transmissions to improve multi-access performance of the multihop wireless networks. Based on the proposed slot scheduling scheme, each node senses the control channel (CCH) or the data channel (DCH) to accurately determine whether it can send or receive the corresponding packets without collisions. Slot reservation on the CCH can be simultaneously executed with data packet transmissions on the DCH. Therefore, it resolves the hidden-terminal type and the exposed-terminal type problems efficiently, and obtains more spatial reuse of channel resources. Concurrent packet transmissions without extra network overheads are maximized. An analytical model combining Markov model and M/G/1 queuing theory is proposed to analyze its performance. The performance comparison between analysis and simulation shows that the analytical model is highly accurate. Finally, simulation results show that, the proposed protocol obviously outperforms the link-directionality-based dual-channel MAC protocol (DCP) and WiFlex in terms of the network throughput and the average packet delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.1
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• pp.25-39
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• 1986

In this paper, we analyze the performance, particularly the flow control mechanism, of the CCITT X.25 protocol in a packet-switched network. In this analysis, we consider the link and packet layers separately, and investigate the performance in three measures; normalized channel throughput, mean transmission time, and transmission efficiency. Each of these measures is formulated in terms of given protocol parameters such as windos size, $T_1$ and $T_2$ values, message length, and so forth. We model the service procedure of the inpur traffic based on the flow control mechanism of the X.25 protocol, and investigate the mechanism of the sliding window flow control with the piggybacked acknowlodgment scheme using a discrete-time Markov chain model. With this model, we study the effect of variation of the protoccol parameters on the performance of the X.25 protocol. From the numerical results of this analysis one can select the optimal valuse of the protocol parameters for different channel environments. it has been found that to maintain the trasnmission capacity satisfactorily, the window size must be greater than or equal to 7 in a high-speed channel. The time-out value, $T_1$, must carefully be selected in a noisy channel. In a normal condition, it should be in the order of ls. The value of $T_2$ has some effect on the transmission efficiency, but is not critical.

• Journal of Multimedia Information System
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• v.3 no.4
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• pp.141-148
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• 2016

This paper proposes a medium access control (MAC) protocol for multiple-input multiple-output (MIMO) ad-hoc networks. Multiple-packet receptions in MIMO systems have attracted as a key technique to achieve a high transmission rate. In the conventional protocols for multiple-packet receptions, timing offsets among multiple-frame transmissions cause frame collisions induced by hidden nodes, which degrades network performance. In the proposed protocol, transmission synchronization among hidden nodes can be achieved by applying pulse/tone exchanges. By applying the pulse/tone exchanges, multiple-packet receptions among hidden nodes can be achieved, which enhances network throughputs compared with the conventional protocol. Simulation results show effectiveness of the proposed protocol.

• IEMEK Journal of Embedded Systems and Applications
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• v.10 no.6
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• pp.381-390
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• 2015

The efficient design of a transport protocol contributes to energy conservation as well as performance improvement in wireless sensor networks (WSNs). In this paper, a node-density-aware transport protocol (NDTP) for intra-cluster transmissions in WSNs for monitoring physical attributes is proposed, which takes node density into account to mitigate congestion in intra-cluster transmissions. In the proposed NDTP, the maximum active time and queue length of cluster heads are restricted to reduce energy consumption. This is mainly because cluster heads do more works and consume more energy than normal sensor nodes. According to the performance evaluation results, the proposed NDTP outperforms the conventional protocol remarkably in terms of network lifetime, congestion frequency, and packet error rate.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.423-425
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• 2007

In this paper, Medium Access Control(MAC) protocol designed for Wireless Body area Sensor Network(Bio-MAC) is proposed, Because in WBSN, the number of node is limited and each node has different characteristics. Also, reliability in transmitting vital data sensed at each node and periodic transmission should be considered so that general MAC protocol cannot satisfy such requirements of biomedical sensors in WBSN. Bio-MAC aims at optimal MAC protocol in WBSN. For this, Bio-MAC used Pattern -SuperFrame, which modified IEE E 802.15.4-based SuperFrame structurely. Bio-MAC based on TDMA uses Medium Access-priority and Pattern eXchange -Beacon method for dynamic slot allocation by considering critical sensing data or power consumption level of sensor no de etc. Also, because of the least delay time. Bio-MAC is suitable in the periodic transmission of vital signal data. The simulation results demonstrate that a efficient performance in WBSN can be achieved through the proposed Bio-MAC.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.3
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• pp.181-189
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• 2001

The software components of embedded control systems get extremely complex as they are designed into distributed systems get extremely complex as they are designed into distributed systems consisting of a large number of inexpensive microcontrollers interconnected by low-bandwidth real-time networks such as the controller area network (CAN). While recently emerging middleware technologies such as CORBA and DCOM address the complexity of distributed programming, they cannot be directly applied to distributed control system design due to their excessive resource demand and inadequate communication models. In this paper, we propose a CORBA-based middleware design for CAN-based distributed embedded control systems. Our design goal is to minimize its resource need and make it support group communication without losing the IDL (interface definition language) level compliance to the OMG standards. To achieve this, we develop a transport protocol on the CAN and a group communication scheme based on the well-known publisher/subscriber model. The protocol effectively realizes subject-based addressing and supports anonymous publisher/subscriber communication. We also customize the method invocation and message passing protocol, referred to as the general inter-ORB protocol (GIOP), of CORBA so that CORBA method invocations are efficiently serviced on a low-bandwidth network such as the CAN. This customization includes packed data encoding and variable-length integer encoding for compact representation of IDL data types. We have implemented our CORBA-based middleware on the mArx real-time operating system we have developed at Seoul National University. Our experiments clearly demonstrate that it is feasible to use CORBA in developing distributed embedded control systems possessing severe resource limitations. Our design clearly demonstrates that it is feasible to use a CORBA-based middleware in developing distributed embedded systems on real-time networks possessing severe resource limitations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.442-445
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• 2006

In Wireless Sensor Networks(WSNs), a sensor node broadcasts an acquisited data to neighboring other nodes and it makes serious data duplication problem that increases network traffic loads and data loss. This problem is concerned with the conflict condition for supporting both the reliability of data transfer and avoidance of network congestion. To solve the problem, a reliable congestion control protocol is necessary that considers critical factors affecting on data transfer reliability such as reliable data transmission, wireless loss, and congestion loss for supporting effective congestion control in WSNs. In this paper, we proposes a reliable congestion protocol, ratted HRCCP, based on hop-hop sequence number, and DSbACK by minimizing useless data transfers as an energy-saved congestion control method.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.117-128
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• 2013

u-safety service system inter-works with the diverse operation agencies, through CCTV network, such as the emergency call terminal with built-in GPS, the mobile communication network, u-safety service provider, relay system and CCTV control center. In the case of the emergency call, this service searches the location of caller in real time, and then continues to search the location of caller through the control of CCTV in the searched place, and can provide the several agencies like guardian, police office, fire station, hospitals, relief organizations and municipalities, with the diverse information necessary for the secure rescue through SMS and wired network. In this paper, a new protocol and specification for u-safety service relay system is designed and implemented. The effectiveness of presented protocol is verified by computer simulation. The designed protocol of u-safety service is applied to real 3GPP and 3GPP2 mobile communication networks to verify its performance.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.12
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• pp.1529-1538
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• 1999

광대역 액세스 망은 B-ISDN 환경에서 다양한 유형의 가입자들을 서비스 노드로 집선하는 기능을 수행한다. ITU-T의 SG13에서는 광대역 액세스 망과 서비스 노드 사이에서 ATM 자원의 동적인 할당 및 해제를 위하여 연결 제어 프로토콜의 표준화를 수행하고 있다. ATM 연결의 설정을 위한 연결 제어 프로토콜과 신호 프로토콜의 연동 기능은 서비스 노드에서 수행되며, ITU-T에서는 순차적 연동 모델을 채택하고 있다. 순차적 연동 모델은 SN에서 각 프로토콜의 절차가 순차적 방식으로 연동되므로 연결 지연이 크다. 본 논문에서는 광대역 액세스 망의 도입으로 인한 연결 설정 지연을 최소화하기 위하여 병렬형으로 수행되는 연동 모델을 제시하였다. 그리고 본 논문에서 제안한 병렬형 연동 모델의 성능 분석을 통하여 순차적 연동 모델과의 연결 설정 지연 및 완료비에 대한 비교, 분석을 수행하였다. 성능 분석에서 사용된 워크로드 파라미터는 RACE MAGIC 프로젝트의 결과를 적용하였다. Abstract In B-ISDN environment, various subscribers are concentrated into a service node via a broadband access network. The SG13 of ITU-T is standardizing a connection control protocol which provides dynamic allocation of ATM resources between an access network and a service node. To establish an ATM connection, interworking functions between the connection control protocol and the signaling protocol are performed at the service node. ITU-T adopts the sequential interworking model. In this paper, we propose the parallel interworking model which minimizes the overall connection setup delay by introducing the access network. Using the performance analysis, we compare our proposed parallel model with the existing sequential model in terms of connection setup delay and completion ratio. The workload parameters of RACE MAGIC project are applied to the analysis and simulation.