• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.9B
• /
• pp.598-603
• /
• 2007

In this paper we propose a QMAC to support QoS(Quality of Service) and to enhance the transmission throughput in Wireless Sensor Networks(WSNs). In the proposed QMAC, sender nodes send transmission request packets with QoS requirements to the receivers node using CSMA/CA MAC protocol. And the receiver node assigns slots according to the packet priority, network topology, and the amount of traffics using TDMA. Using QMAC we get the enhanced throughput and QoS support by lowering the duplicated slot assignment.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.31 no.1
• /
• pp.117-129
• /
• 2006

In this paper, we consider broadband satellite networks using MF-TDMA (Multi-Frequency Time Division Multiple Access) scheme. We analyze the number of expected lost packets in each terminal, and mathematically formulate optimal buffer and timeslot allocation model to minimize the weighted sum of the numbers of expected lost packets. We also suggest optimal buffer and timeslot allocation scheme based on Lagrangean relaxation technique to solve the proposed model in a fast time. Extensive experiments show that the proposed scheme provides encouraging results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2014.10a
• /
• pp.102-105
• /
• 2014

일반적으로 무선 센서네트워크에서 각 센서 노드들에서 생성된 데이터는 목적지 노드 즉, 싱크(sink) 노드로 전송되어진다. 본 논문에서는 이처럼 데이터 전송이 몰리게 되는 sink 노드 근처에서 노드들 사이에 전송된 데이터 패킷의 충돌을 줄임으로 에너지 효율과 지연의 성능을 향상시킬 수 있는 TDMA 기반의 MAC 프로토콜을 제안한다. 전송할 데이터를 가지는 노드들은 먼저 싱크 노드에게 자신이 전송할 데이터의 양을 포함하는 RTS 패킷을 전송한다. 이 RTS 패킷을 받은 싱크 노드는 각 노드들에게 전송할 수 있는 전송 스케줄을 노드들에게 보내고, 이 스케줄을 받은 각 노드들은 전송 스케줄에 맞추어 자신들에게 할당된 슬롯에 데이터 패킷을 전송함으로 충돌 없이 bursty데이터를 전송한다. 이 방법을 통하여 각 노드들은 동시에 멀티 슬롯을 할당 받아 여러 패킷을 전송할 수 있다. 따라서 버스티한 트래픽 전송에서 지연(Delay)을 줄이는 동시에 충돌을 없애 데이터 전송 효율을 높일 수 있다.

• Current Optics and Photonics
• /
• v.4 no.3
• /
• pp.186-192
• /
• 2020

This paper describes a real-time monitoring system in Ethernet passive optical networks (EPON) that uses burst-mode fiber Bragg grating (FBG) optical sensors. The FBG interrogation unit in the optical line terminal (OLT) transmits the monitoring wavelength to optical network units (ONUs). The FBG sensor unit in each ONU returns a burst-mode monitoring signal to the OLT. As the system applies time division multiple access (TDMA), a uniform Bragg wavelength can be used to monitor the EPON system. The FBG interrogation unit analyzes the received burst-mode monitoring signals and outputs fault information on the ONU branches in EPON. The simulation results show the effectiveness of the proposed monitoring system based on TDMA. In addition, we compared the proposed TDMA-based monitoring system with a WDMA-based monitoring system.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.2
• /
• pp.687-708
• /
• 2017

The machine-to-machine (M2M) communication is featured by tremendous number of devices, small data transmission, and large uplink to downlink traffic ratio. The massive access requests generated by M2M devices would result in the current medium access control (MAC) protocol in LTE/LTE-A networks suffering from physical random access channel (PRACH) overload, high signaling overhead, and resource underutilization. As such, fairness should be carefully considered when M2M traffic coexists with human-to-human (H2H) traffic. To tackle these problems, we propose an adaptive Slotted ALOHA (S-ALOHA) and time division multiple access (TDMA) hybrid protocol. In particular, the proposed hybrid protocol divides the reserved uplink resource blocks (RBs) in a transmission cycle into the S-ALOHA part for M2M traffic with small-size packets and the TDMA part for H2H traffic with large-size packets. Adaptive resource allocation and access class barring (ACB) are exploited and optimized to maximize the channel utility with fairness constraint. Moreover, an upper performance bound for the proposed hybrid protocol is provided by performing the system equilibrium analysis. Simulation results demonstrate that, compared with pure S-ALOHA and pure TDMA protocol under a target fairness constraint of 0.9, our proposed hybrid protocol can improve the capacity by at least 9.44% when ${\lambda}_1:{\lambda}_2=1:1$and by at least 20.53% when ${\lambda}_1:{\lambda}_2=10:1$, where ${\lambda}_1,{\lambda}_2$ are traffic arrival rates of M2M and H2H traffic, respectively.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1999.04a
• /
• pp.375-376
• /
• 1999

• The Journal of the Korea Contents Association
• /
• v.10 no.8
• /
• pp.51-58
• /
• 2010

In data collection using a mobile sink, the time that sensor nodes are included in its communication radius is not uniform. The data collection schedule in non-uniform time is needed between a mobile sink and sensor nodes for efficient data collection. The existing data collection schemes using a mobile sink considered staying time in its communication range and data collected by the mobile sink. However, they did not consider the characteristics of data collected in sensor networks. In this paper, we propose a TDMA based schedule scheme that consists of the data collection period by each sensor nodes and the data collection period between a mobile sink and sensor nodes. Moreover, we propose a data collection scheme considering the variability of data in sensor networks. The proposed data collection scheme collects only data that changed larger than the threshold set by the user. In order to show the superiority of the proposed scheme, we compare it with DWEDF that aims to collect data uniformly. As a result, our experimental results show that the proposed scheme reduces about 23% energy consumption and the data collection failure of sensor nodes over the DWEDF.

• Journal of Institute of Control, Robotics and Systems
• /
• v.15 no.8
• /
• pp.867-875
• /
• 2009

A wireless sensor network inherently comprises a plurality of sensor nodes widely deployed for sensing environmental information. To add new functions or to correct some faulty functions of an existing wireless sensor network, the firmware for each sensor node needs to be updated. Firmware update would be quite troublesome if it requires the gathering, reprogramming, and redeploy of all of already deployed sensor nodes. Over-the-air programming (OTA) facilitates the firmware update process, thereby allowing convenient maintenance of an already-deployed sensor network. This paper proposes and implements a remote firmware update mechanism for a TDMA-based wireless sensor network, in which the firmware for sensor nodes constituting the TDMA-based sensor network can be easily updated and the update process can be conveniently monitored from a remote site. We verify the validity of the proposed firmware update method via experiments and introduce three wireless sensor networks installed in outdoor sites in which the proposed firmware update mechanism has been exploited.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37C no.11
• /
• pp.1129-1137
• /
• 2012

The wireless link of tactical datalink system provides a communication network to share digitalized tactical data in real-time. Also MAC(Multiple Access Control) of this system is subject to TDMA or CSMA according to a operated circumstance of target nodes to exchange the data reliably. In this paper, we verify the operability when we use CSMA scheme based on MIL-STD-188-220 in tactical datalink system which is basically designed with TDMA, and provide a mathematical analysis scheme to verify the operability and performance. Finally, by implementing CSMA scheme to a tactical datalink equipment we obtain practical results which can be compared with theoretical results.

• Journal of the Korea Society of Computer and Information
• /
• v.15 no.5
• /
• pp.103-111
• /
• 2010

This paper proposes an efficient data transmission strategy using adaptive-tier low transmission power schedule in a TDMA-based ad hoc MAC protocol. Since the network resource of ad hoc networks has the characteristic of reassignment due to the multiple interferences and the contention-based limited wireless channel, the efficient time slot assignment and low power transmission scheme are the main research topics in developing ad hoc algorithms. Based on the proposed scheme of interference avoidance when neighbor clusters transmit packets, this paper can minimize the total energy dissipation and maximize the utilization of time slot in each ad hoc node. Simulation demonstrates that the proposed algorithm yields 15.8 % lower energy dissipation and 4.66% higher time slot utilization compared to the ones of two-tier conventional energy dissipation model.