• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.12
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• pp.6243-6259
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• 2019

As a foundation of next-generation air transportation systems, automatic dependent surveillance-broadcast (ADS-B) helps pilots and air traffic controllers create a safer and more efficient national airspace system. Owing to the open communication environment, it is easy to insert fake aircraft into the system via spoofing or the insertion of false messages. Efforts have thus been made in academic research and practice in the aviation industry to ensure the security of transmission of messages of the ADS-B system. An identity-based batch verification (IBV) scheme was recently proposed to enhance the security and efficiency of the ADS-B system, but current IBV schemes are often too resource intensive because of the application of complex hash-to-point operations or bilinear pairing operations. In this paper, we propose a lightweight IBV signature scheme for the ADS-B system that is robust against adaptive chosen message attacks in the random oracle model, and ensures the security of batch message verification and against the replaying attack. The proposed IBV scheme needs only a small and constant number of point multiplication and point addition computations instead of hash-to-point or pairing operations. Detailed performance analyses were conducted to show that the proposed IBV scheme has clear advantages over prevalent schemes in terms of computational cost and transmission overhead.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.40-47
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• 2006

The next-generation mobile communication system are required to provide high-data-rate and high quality transmission over hostile radio channels. Orthogonal Frequency Division Multiplexing(OFDM) technique regarded as a most promising solution in mobile environment. This paper considers the issue of efficient subcarrier allocation for OFDM system in multi-service application. Proposed algorithm can consider channel gain of each service and divide subchannel. Proposed method considers priority of service and divide more subchannels in high priority service. When proposed algorithm compares with existent algorithm, the convergence rate improves and the calculation amount is decreased.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.82-86
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• 2014

In this paper, we propose a novel modulation scheme specialized in real time broadcast system using a multicopter. Since multicopters have many advantages in aerial photography, they have been widely used in broadcasting technologies. However, because of restrictions on flight time, it is difficult to utilize multicopters in real time broadcasting systems. Therefore, video transmission using multicopter is necessary for low power communication techniques in air channel environment. Performance results of the hybrid modulation in this paper are compared to that of conventional modulations with Bit Error Rate (BER) and Signal to Noise Ratio (SNR) simulations. The results also showed that proposed system is suitable for aerial photography. Experiments demonstrated the superiority of the proposed modulation scheme by showing received symbols through an USRP equipment.

• Fire Science and Engineering
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• v.33 no.6
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• pp.186-189
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• 2019

NFSC 202 stipulates that if a loudspeaker or wiring on one floor of a building is shorted because of fire, it should not interfere with the fire notification on the other floors. To address this problem, this study proposes an ultrasonic transmitter/receiver consisting of an ADC, HPF, and LPF in an emergency broadcasting system that can operate regardless of the volume level of the amplifier output loudspeaker capacity. After transmitting the transmission frequency at -12 dB (110 kHz), it is received at -18 dB by transmitting -12 dB in case of short circuit depending on the frequency characteristics. Typically, depending on the loudspeaker capacity, it is received from -24 dB to -66 dB. In case of disconnection, it exceeds -66 dB and no data are received. It is also possible to check the track status during fire or general broadcasting. Thus, it was confirmed that the system is suitable for NFSC 202 regulations. Furthermore, as the current system is replaced, the inspection or test criteria should be amended or revised.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.5C
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• pp.454-464
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• 2002

In the ATM-PON (Asynchronous Transfer Mode-Passive Optical Network), the downstream cell transmitted by an OLT is broadcast to all ONUs. The ONU receives selectively its own cells by VP filtering. On the other hand, the upstream cell can be transmitted by ONU in the case of receiving a grant from the OLT. After providing the grant to an ONU, the OLT expects the arrival of a cell after an elapse of the equalized round trip delay. ITU-T G.983.1 recommends that one bit error is allowed between the expected arrival time and the actual arrival time at the OLT. Because the ONU processes the different delay to each type of grant (ranging, user cell, and mimi-slot grant), it is not simple to design the transmission part of ONU. In this paper, we implement a grant processor which provides the delay accurately in the ONU TC chip with the FPGA. For the given equalized delay, it deals with the delay for the cell, the byte, and the bit unit by using the shift register, the byte counter, and the D flip-flop, respectively. We verify the operation of the grant processor by the time simulation and the measurement of the optical board output.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.489-497
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• 2009

In the 3GPP LTE and IEEE 802.16m standardizations for IMT-Advanced, the efficient transmission of multicast and broadcast data is one of the important issues to improve system performance. Especially, to guarantee each user's QoS in the multicast group, H-ARQ or adaptive modulation are considered to be adoption, however, reduction of feedback overhead is one of the most important issues. In this paper, performance of the previously proposed OOK (On-Off Keying) based common ACK/NACK feedback channel is analyzed through theoretical analysis and simulation. Based on the results, system parameter optimization methods for common feedback channel are proposed. In addition, through computer simulation, it is shown that the common feedback method according to the proposed feedback parameter optimization can feedback ACK/NACK information for multicast H-ARQ transmission, more reliably than the conventional user dedicated feedback method in 3GPP LTE systems, and can reduce the feedback overhead as well.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.10
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• pp.1312-1318
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• 2020

In this paper, we propose a video transmission scheme for exclusive OR based video streaming (XC) that can improve the efficiency of video streaming by using receivers' caches and coding of video data. Contrary to conventional streaming schemes such as multicast where video contents can be transmitted on single channel only when two clients request the same video, the proposed streaming scheme can transmit video contents on single channel conditionally according to the status of the clients' caches even though two clients request different video contents. We analyze the performance of the proposed transmission for XC in terms of the streaming efficiency through extensive computer simulations and compare it with a conventional scheme. Simulation results show that the proposed scheme can enhance the streaming efficiency by 21%, compared with the conventional scheme.

• The KIPS Transactions:PartC
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• v.14C no.7
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• pp.571-582
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• 2007

Vehicular ad-hoc networks is temporarily established through inter-vehicle communication without any additional infrastructure aids. It requires a immediate message propagation because it mainly deals with critical traffic information such as traffic accidents. The distance-based broadcast scheme is one of the representative broadcast schemes for vehicular ad-hoc network. In this scheme, a node to disseminate messages is selected based on a distance from a source node. However, a message propagation delay will be increased if the relay nodes are not placed at the border of transmission range of the source node. In particular, when the node density is low, the message propagation delay is getting longer. In this paper, we propose a time-window reservation based relay node selection scheme. A node receiving the alert message from the source node has its time-window and randomly selects its waiting time within the given time-window range. A proportional time period of the given time-window is reserved in order to reduce the message propagation delay. The experimental results show that the proposed scheme has shorter message propagation delay than the distance-based broadcast scheme irrespective of node density in VANET. In particular, when the node density is low, the proposed scheme shows about 26% shorter delay and about 46% better performance in terms of compound metric, which is a function of propagation latency and network traffic.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8B
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• pp.668-676
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• 2012

In this paper, on the assumption that MPI collective communication function is converted into a group of point-to-point communication functions in the transaction level, an algorithm that optimizes broadcast, scatter and gather function among MPI collective communication is proposed. The MPI hardware engine that operates the proposed algorithm was designed, and it was named the OCC-MPE (Optimized Collective Communication Message Passing Engine). The OCC-MPE operates point-to-point communication by using the standard send mode. The transmission order is arranged according to the algorithm that proposes the most frequently used broadcast, scatter and gather functions among the collective communications, so the whole communication time is reduced. To measure the performance of the proposed algorithm, the OCC-MPE with the Bus Functional Model (BFM) based on SystemC was designed. After evaluating the performance through the BFM based on SystemC, the proposed OCC-MPE is designed by using VerilogHDL. As a result of synthesizing with the TSMC $0.18{\mu}m$, the gate count of each OCC-MPE is approximately 1978.95 with four processing nodes. That occupies approximately 4.15% in the whole system, which means it takes up a relatively small amount. Improved performance is expected with relatively small amounts of area increase if the OCC-MPE operated by the proposed algorithm is added to the MPSoC (Multi-Processor System on a Chip).

• Electronics and Telecommunications Trends
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• v.25 no.6
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• pp.50-58
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• 2010

셀룰러 이동통신망을 이용한 멀티캐스트/브로드캐스트 전송 기술은 이미 수 년 전부터 표준화되어 왔지만 무선 전송 대역의 부족과 멀티캐스트/브로드캐스트 서비스의 필요성에 대한 문제로 상용화까지는 이루어지지 못하고 있었다. 그러나， 3GPP의 LTE와 mobile WiMAX 기술의 등장으로 인하여 전송 대역의 부족에 대한 문제가 해결되었고 스마트폰 등 첨단 기능을 가지는 이동 단말의 등장으로 인하여 멀티캐스트/브로드캐스트 서비스에 대한 요구가 증가되는 등 기술 및 시장에 형성되고 있다. 본 논문에서는 3GPP LTE에서 멀티미디어 멀티캐스트/브로드캐스트 전송 기술에 대한 표준화 동향에 대해서 살펴보고 이를 제공하기 위한 망구조에 대하여 설명한다. 그리고 3GPP LTE에서 동기화된 멀티셀 전송을 위한 전송 기술, 프레임 구조아 동기화 기술에 대해서 기술한다.