• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4B
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• pp.192-198
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• 2008

In this paper, we propose a scheme that improves the transmission performance of realtime multimedia data in wireless Local Area Network (LAN) environment, through the dynamical control of Transmission Opportunity (TXOP) period of the IEEE 802.11e HCCA Medium Access Control (MAC). The existing schedulers which determine the frame transmission time and its duration could not appropriately cope with the change of physical transmission rate, since the TXOP period has remained unchanged with the change of transmission rate of the wireless station. Our scheme is devised to keep the transmission performance of real-time multimedia data effectively unchanged by making TXOP period be extended when the transmission rate gets reduced. The proposed scheme is experimented along with IEEE 802.11e reference model using NCTUns simulator, which shows that the multimedia data is effectively delivered with the change of transmission rate as the distance between the wireless station and its access point increases.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.4
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• pp.87-94
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• 2016

This paper proposes an energy transmission method to maximize energy efficiency of a based station. This method makes use of classification of service type to solve an inefficient use of transmission power, which is from exponential relationship between the legacy data throughput and transmission power. The proposed one is a way to find the most energy-efficiency points with the transmitted optimal amount of data on users in a base station of wireless network environment. For this, we propose EETA (Energy-Efficient Transmission Algorithm) which can control the amount of data and the holding time at the base station. As a result, the proposed method can improve the energy efficiency of about 10% compared to the legacy base station.

• Journal of Korea Multimedia Society
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• v.20 no.2
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• pp.254-260
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• 2017

Data packets from sensor nodes scattered over measuring fields are generally forwarding to the sink node, which may be connected to the wired networks, in a wireless sensor network. So many data packets are gathered near the sink node, resulting in significant data packet collisions and severe transmission latency. In an event detection application such as object tracking and military, bursty data is generated when an event occurs. So many data packet should be transmitted in a limited time to the sink node. In this paper, we present a delay efficient and bursty traffic friendly MAC protocol called DEBF-MAC protocol for wireless sensor networks. The DEBF-MAC uses a slot-reserved mechanism and sleep period control method to send multiple data packets efficiently in an operational cycle time. Our simulation results show that DEBF-MAC outperforms DW-MAC and SR-MAC in terms of energy consumption and transmission delay.

• International Journal of Computer Science & Network Security
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• v.21 no.3
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• pp.48-54
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• 2021

Security is an important issue for wireless communications and poses many challenges. Most security schemes have been applied to the upper layers of communications networks. Since in a typical wireless communication, transmission of data is over the air, third party receiver(s) may have easy access to the transmitted data. This work examines a new security technique at the physical layer for the sake of enhancing the protection of wireless communications against eavesdroppers. We examine the issue of secret communication through Rayleigh fading channel in the presence of an eavesdropper in which the transmitter knows the channel state information of both the main and eavesdropper channel. Then, we analyze the capacity of the main channel and eavesdropper channel we also analyze for the symbol error rate of the main channel, and the outage probability is obtained for the main transmission. This work elucidate that the proposed security technique can safely complement other Security approaches implemented in the upper layers of the communication network. Lastly, we implement the results in Mat lab

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.1023-1031
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• 2010

With recent advances in hardware and wireless communication techniques, wireless multimedia sensor network which collects multimedia data through wireless sensor network has started to receive a lot of attentions from many researchers. Wireless multimedia sensor network requires a research of efficient compression and transmission to process the multimedia data which has large size, in the wireless sensor network that has very low network bandwidth. In this paper, we propose PIT protocol for the transmission based on the priority that classified by the DPCM compression. The PIT protocol sets different priority to the each subbands which are divided by the wavelet transform. The PIT protocol transmits the data with higher priority to guarantee the high image quality. The PIT protocol uses the characteristic of wavelet transform that the transformed image is very insensible to the data loss. In PIT protocol, each subbands of wavelet transformed image has fair weight in the compressed image to utilize the prioriy based transmission. The experiment results show that the PIT protocol improves the quality of image in spite of data loss.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.51-53
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• 2006

This paper proposes a portable ECG monitoring system, which integrates uptodate PDA and RF communication technology. The aim of the study is to acquire the subject's biomedical signal without any constraint. It has two types of transmission mode, which are total signal transmission mode and HR(heart rate)/SC(step count) transmission mode. In audition, wireless communication technology uses Zigbee Wireless PAN and can work in low-power mode, which is one of the advantages of ZiBbee communication technology. The developed system is composed of a transmitter and a receiver. The transmitter has three-axial acceleration sensor. ECG amplifier and Zigbee communication controller. In total signal transmission mode, it can send data 50 packets per second whose transmission speed corresponds to 300 ECG samples and 60 acceleration samples. In HR/SG transmission mode, it can calculate heart rate from EEG data with 216 samples per second and step count from acceleration data and send a packet every cardiac cycle. The receiver forwards the received data to PDA, where the data can be stored and displayed. Therefore, the developed device enables to continuous monitoring for Activities of Daily Living(ADL). Also, this method will reduce medical costs in the aged society.

• Journal of Information Technology Services
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• v.9 no.2
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• pp.151-161
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• 2010

Recently, as the era of ubiquitous has arrived, an infrastructure for the short-distance wireless communication has been extended socially, and thus a variety of services are being proposed. The Multimedia Contents Delivery System using the ZigBee, in particular, has an important stance in enlargement of a variety of services in the aspect of individual-oriented service support though Wireless Personal Area Network (WPAN). Nonetheless, the ZigBee, or the IEEE 802.15.4 Standard, has many restrictions on the Multimedia Contents Delivery System due to the low data transport rate. In order to improve the ZigBee which presents a limit on the transport rate at the IEEE 802.15.4 Standard, this thesis has designed the burst mode which is a method of transmitting a certain amount of data in block units at a high speed without any stoppage until the completion of the transmission. Also, to provide a Multimedia Contents Delivery Service with an application of the normal data transmission mode, it improved the transmission performance of the ZigBee. In addition, for the Multimedia Contents Delivery Service under the ubiquitous environment, it designed and implemented a broadcasting Multimedia Contents Delivery System based on the ZigBee to conduct a comparative analysis on the data transmission performance according to the transmission method.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.10
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• pp.21-29
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• 2013

This paper proposed the architecture of the authentication and the transmission for high reliable emergency data management based on U-healthcare wireless mesh networks. In U-healthcare monitoring service, the high reliable bio data management as well as the data transmission are required because the monitoring emergency bio data is related linked to life. More specifically, the technologies of the identity authentication of the measuring bio data, the personalized emergency status diagnosis who is authenticated the bio data and the emergency data transmission are important first of all. To do this, this paper presents the structure and protocol of the identity authentication management with using the extended IEEE 11073 PHD, the structure of policy-based management of the emergency bio data for the highly reliable management and the resilient routing protocol based on wireless mesh network for the reliable data transmission.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.274-277
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• 2008

Rekeying is the process of changing the encryption key of an ongoing communication. The main objective is to limit the amount of data encrypted with the same key. The IEEE 802.11 standard defines the Wired Equivalent Privacy, or WEP, encapsulation of 802.11 data frames. MAC at sender encrypts the payload (frame body and CRC) of each 802.11 frame before transmission using RC4 stream cipher. MAC at receiver decrypts and passes data to higher level protocol. WEP uses symmetric key stream cipher (RC4) where same key will be used for data encryption and decryption at the sender and the receiver. WEP is not promising with the advancement of the wireless technology existing today. We propose to use the existing information to define the security attributes. This will eliminate the steps that regenerated keys have to be sent to each other over certain period. The rekeying scheme is according to the number of bytes transmitted. Therefore, even the attacker has recorded the packets, it will be insufficient information and time for the attacker to launch the attacks as the key is not deterministic. We develop a packet simulation software for packet transmission and simulate our propose scheme. From the simulation, our propose scheme will overcome the weak WEP key attack and provide an alternative solution to wireless packet transmission. Besides that, our solution appears to be a software approach where only driver updates are needed for the wireless client and server.

• Journal of information and communication convergence engineering
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• v.9 no.6
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• pp.676-682
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• 2011

Sybil attack can disrupt proper operations of wireless sensor network by forging its sensor node to multiple identities. To protect the sensor network from such an attack, a number of countermeasure methods based on RSSI (Received Signal Strength Indicator) and LQI (Link Quality Indicator) have been proposed. However, previous works on the Sybil attack detection do not consider the fact that Sybil nodes can change their RSSI and LQI strength for their malicious purposes. In this paper, we present a Sybil attack detection method based on a transmission power range. Our proposed method initially measures range of RSSI and LQI from sensor nodes, and then set the minimum, maximum and average RSSI and LQI strength value. After initialization, monitoring nodes request that each sensor node transmits data with different transmission power strengths. If the value measured by monitoring node is out of the range in transmission power strengths, the node is considered as a malicious node.