• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.3
• /
• pp.28-35
• /
• 2011

Cooperative ARQ scheme is effective for better QoS guarantee for the next generation mobile communication systems where multimedia data transmission highly increases. In this paper, we propose a cooperative ARQ strategy in ad hoc cognitive relays for mobile multimedia communication for supporting instantaneous cooperation in MANET environment. In the proposed strategy, to support real time, delay-sensitive services, whenever a frame is transmitted from the source, each relay actively senses the SINR of the signal transmitted from the source, and determine whether to propose retransmission or not before the destination transmits feedback signal. To minimize the false retransmission decision or needless retransmission, we propose an adaptive sensing threshold optimization algorithm to maintain suboptimal sensing thresholds for each relay. By computer simulation, it is shown that the proposed cooperative ARQ retransmission scheme outperforms the conventional schemes with respect to frame transmission delay and frame loss probability in real time multimedia data transmission system.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.8
• /
• pp.1561-1570
• /
• 2009

Being different from traditional mobile communication networks or wireless LAN with access points, ad hoc network can provide direct communications between homogeneous stations. Thus, it can be considered as a much advanced network. Somehow, many researches have been done to enhance system performance of ad hoc networks up to now, one of which is cooperative communications. In this paper, a cooperative MAC protocol, called CO-MAC protocol, is proposed and its performance is evaluated with a mathematical approach. Numerical results show that this scheme provides more enhanced system throughput especially when frame transmission error probability is high than DCF scheme, which is the key protocol in IEEE 802.11 standard, and rDCF scheme.

• Journal of Satellite, Information and Communications
• /
• v.7 no.3
• /
• pp.75-77
• /
• 2012

In recent years, with the development of various transportation, railway evolved a lot. With advanced rail system, efficient communication system was required. for the delivery of accurate information of railway communications systems. Accordingly, railway communication system has evolved in a variety of ways. Cooperative communication method was proposed railway minimize the effects of fading in wireless communications and more efficient communication. In this paper, we present cooperative transmission techniques and channel characteristics and examples, and simulation results.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.12 no.6
• /
• pp.251-255
• /
• 2012

In recent years, according to improvement of various vehicle instruments, railway also has been developed in various fields. As a result, to transmit accurate information to each railway system, the efficient communication system is required. In railway communication system, mitigation of wireless fading is very important. So, in this paper we introduced the cooperative relay channel model and cooperative relay scheme. Also we analyzed and simulated the cooperative relay scheme which is suitable for railway communication systems.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.52 no.10
• /
• pp.168-174
• /
• 2015

In this paper, we analyze the performance of cooperative communication techniques on an underwater channel. By analyzing the BER performance of cooperative transmission protocol and combining types ERC, FRC, SNRC and ESNRC on underwater channel, through the result, we can choose an a proper cooperative technique for an underwater channel. The analysis of BER performance is achieved by a computer simulation.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.1
• /
• pp.45-49
• /
• 2011

Cooperative multihop communications support effective transmissions over underwater acoustic channels as inferior wireless channels. But the performance of cooperative multihop systems may degrade due to the lack of cooperative nodes at the initial operation time duration. At the initial time duration, the lack of cooperative nodes causes more errors, and the multihop network propagates these errors. In this paper, we apply fountain code to the cooperative multihop system at the initial time duration, and show performance improvements by simulations.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.10A
• /
• pp.972-979
• /
• 2008

Two-way relay channel is a bidirectional cooperative communication channel that two terminals communicate each other with the help of a relay. In the previous cooperative communication schemes, a relay uses two divided resources for bidirectional transmission. When a network coding is used at a relay, the relay can transmit bidirectional data to two terminals simultaneously using one resource only. Thus the throughput of this scheme is greater than that of the previous scheme. In this paper, we showa two-way cooperative ARQ protocol using network coding and the throughput of this protocol is analyzed using a state diagram.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39C no.9
• /
• pp.789-800
• /
• 2014

In this paper, we propose a cooperative protocol of relay-based WUSB/DRD and WLP device in WSS of ship area WiMedia environment. For this purpose, we investigate a RNT table configuration and algorithm of RNS relay node used in relay-based cooperative communication. Then, we describe a device that makes up WLP network and propose a cooperative protocol for WUSB/DRD/WLP device communication. The proposed cooperative protocol can communicate with WUSB/DRD/WLP devices by using standard DRP reservation and WUSB DRP reservation.

• Journal of Satellite, Information and Communications
• /
• v.7 no.1
• /
• pp.7-12
• /
• 2012

In this paper, we proposed spectrum sensing using cooperative relay to solve problem of sensing performance degradation due to CPE (Customer-Primise equipments) which causes low SNR (signal-to-noise ratio) problem. In cooperative communication system, AF (amplify-and-forward) and DF (decoded-and-forward) is widely used for relay mechanism. Also, it is expected that cooperative relay scheme guarantees the high sensing performance by its diversity gain. Based on these backgrounds, in this paper, we apply to cooperative relay scheme to the CR (cognitive radio) system, and simulation results show comparison of the sensing performance between AF and DF.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.12 no.4
• /
• pp.31-36
• /
• 2012

In this paper, we proposed spectrum sensing using cooperative relay to solve problem of sensing performance degradation due to CPE (Customer-Premises equipments) which causes low SNR (signal-to-noise ratio) problem. In cooperative communication system, AF (amplify-and-forward) and DF (decoded-and-forward) is widely used for relay mechanism. Also, it is expected that cooperative relay scheme guarantees the high sensing performance by its diversity gain. Based on these backgrounds, in this paper, we apply to cooperative relay scheme to the CR (Cognitive Radio) system, and simulation results show comparison of the sensing performance.