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ITU-R M.1842-1, which is one of the renowned specification for VHF data exchange system (VDES) devoted to maritime mobile applications, has been standardized wireless transmission protocols according to the peculiar characteristics of a maritime communications scenario. Generally, in the Annex-4 of ITU-R M.1842-1, the VHF data link protocols for maritime mobile services are described along with a...
This paper investigates the deployment of an SDN-based UAV network providing communication service. Such a network is extremely useful in emergency scenarios. In such a network, the mobility of UAVs is minimal. We consider the placement of the SDN controller and its implications in terms of communication overhead and end-to-end delay of the control packets exchanged between the UAVs and the controller...
In this paper, we present a discussion on the congestion control for machine type communications (MTC) in long term evolution (LTE). A huge number of devices and the bursty nature of their packet arrival pattern are two important features of MTC and pose a challenge to the random access procedure of LTE. Access barring which consists of two types, access class barring (ACB) and extended access barring...
The millimeter wave bands will be used for 5G or IoT to overcome frequency insufficiency. This paper shows relations of received power, multipath delay spread and distance in urban low-rise environments at both 28 and 38 GHz. The wideband characteristics had been measured with a channel sounder, a directional antenna for transmitter, and an omni-directional antenna for receiver in Daejeon area.
WAVE(Wireless Access in Vehicular Environments) designed for vehicle communication has the features of a short initial link, low latency and high mobility. The success of data transmission in WAVE is affected by the priority and size of data and how many nodes are transmitting the data. In this paper, we tested and analyzed how the success rate of data transmission of each node varies according to...
This paper presents a mathematical analysis of the delay performance of the Appropriate Permission Probability algorithm in term of average delay time. The system performance is derived as a function of the number of users. The numerical results reveal that the Appropriate Permission Probability algorithm provides superior performance compared to the Binary tree, Ternary tree and IEEE 802.11 DCF algorithms.
We have proposed synchronized Spread-Spectrum Code-Division Multiple-Access (SS-CDMA) communication for location and short message communication system using Quasi-Zenith Satellite System (QZSS) as a safety confirmation system at the time of grade disaster. In this communication, the satellite reception timings of all uplink signals are synchronized using transmission timing control method in order...
Vehicular Ad Hoc Networks (VANET) have become one of the most important research areas for the successful and deployment of intelligent transportation system and the unmanned vehicle technologies. In VANET, Travel Prediction-based Data Forwarding (TPD) was proposed as one of novel data forwarding schemes based on road traffic statistics. However, the TPD could not guarantee good performance in the...
As an emerging technology, Mobile Edge Computing (MEC) is introduced to reduce network delay and provide context-aware services. MEC servers are located in close proximity to users, enabling users to seamlessly access services running on edge facilities. However, capacity and bandwidth constraints of MEC servers limit the number of services to be deployed. Therefore, an important problem is how to...
In this paper, we propose a tele-commanding system model based on delay tolerant network (DTN) for the space communication. For designing this model, we use asynchronous message service (AMS) which is one of application services of DTN. We propose the tele-commanding algorithm, which allows AMS messages to be recognized as a tele-commands. This enables nodes received a tele-command message to conduct...
We propose new scheduling algorithms to support low latency packet switching targeting for all-optical data center switch. Based on simulation result, our proposed scheduling algorithms significantly improve the average delay and maximum delay compared with the existing algorithms. Especially when the traffic load is very high, the average delay of our algorithm is reduced to only 10% of the existing...
In disaster situations, networks are fragmented due to the disruptions of communication infrastructure and stable connectivity between nodes is not guaranteed. Therefore, opportunistic forwarding based on delay tolerant networks (DTN) should be used for message delivery in such disaster situations. Also, information centric network (ICN) approach can be used for communication of urgent messages to...
Recently, many applications for co-operative Intelligent Transportation System (C-ITS) using wireless vehicle communication technology such as DSRC have been developed to improve traffic problems and provide user convenience. Above all, broadcast message sets such as CAM and DENM are very useful for vehicle safety. However, V2X systems must design system parameters in highly congested traffic conditions,...
The LTE system that traditionally uses the licensed band have added the new technology, licensed assisted access (LAA), that enables to use 5 GHz unlicensed band with existing licensed band. Coexistence with Wi-Fi is major part of the LAA technology and regulations relating to coexistence has been revised after LAA technology emerged in Europe. Channel occupancy time (COT) is a critical parameter...
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