• The KIPS Transactions:PartC
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• v.15C no.1
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• pp.45-50
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• 2008

Mobile ad hoc networks (MANETs) allow mobile nodes to communicate among themselves via wireless multiple hops without the help of the wired infrastructure. Therefore, in the MANET, a route setup mechanism that makes nodes not within each other's transmission range communicate is required and, for this, the Ad-hoc On-demand Distance Vector (AODV) was proposed as one of the reactive routing protocols well suited for the characteristics of the MANET. AODV uses the hop count as the routing metric and, as a result, a node selects the farthest neighbor node as its next hop on a route, which results in a problem of deteriorating the overall network throughput because of selecting a relatively low data rate route. In this paper, we propose an efficient reactive routing protocol based on the multi-rate aware MAC. Through the simulations, we analyze the performance of our proposed mechanism and, from the simulation results, we show that our proposed mechanism outperforms the existing mechanism.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.10
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• pp.2237-2246
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• 2010

In this paper, the performance of a RCO-MAC protocol is evaluated using a different traffic model. Data frames are assumed to generate based on an exponential distribution from one source node and then directly to be stored into the input buffer in the source node. System throughput, average access delay and average system delay are used as a performance measure. Performance evaluation is carried out by the computer simulation. Numerical results show that the RCO-MAC scheme offers 18% higher system throughput than the rDCF scheme. In addition, the numerical results show that the RCO-MAC protocol also offers the better average system delay under any traffic load than that by the rDCF scheme, which was not obtained in the previous research due to the saturated traffic model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11B
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• pp.900-910
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• 2004

Route failure is mainly caused by mobility of mobile host in ad hoc networks. Route failure, which may lead to sudden packet losses and delays, is losing the route from source to destination. In this situation, TCP assumes that congestion has occurred within the network and also initiates the congestion control procedures. Congestion control algorithm provides the means for the source to deal with lost packets. TCP performance in ad hoc environments will be degraded as TCP source cannot distinguish congestion from route failure. In this paper, we propose TCP-P as pre-detection approach to deal with route failure. TCP-P freezes TCP through pre-detection of route failure. Route failure information of the proposed mechanism is obtained not by routing protocol but by MAC protocol. The intermediated node, obtaining route failure information by its MAC layer, relays the information to TCP source and lets TCP source stop the congestion control algorithm. Results reveal that TCP-P responding with proactive manner outperforms other approaches in terms of communication throughput under the presence of node mobility.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.7
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• pp.603-611
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• 2013

In this paper, we propose a new frame structure and the underlying dynamic resource control mechanism to support an integrated service, including a real-time (RT) service that requires to serve the end-to-end delay performance, as well as non-real-time (NRT) service, using Self-Organizing Time Division Multiple Access (SO-TDMA)-based MAC protocol in a multi-hop ad-hoc maritime communication network. The underlying frame structure is dynamically configured by resource allocation to guarantee the average target outage performance of the real-time service. Toward this end, we analyze the average outage probability and its performance is verified for the proposed frame structure by simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11B
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• pp.1685-1695
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• 2010

In this paper, we propose a new reliable multicast MAC protocol over the IEEE 802.11-based tactical ad hoc networks. The major contribution compared to the previous reliable multicast schemes using consecutive CTSs/ACKs is that the proposed scheme can send multiple CTS/ACK messages concurrently assisted by MC-DS/CDMA mechanisms. When multiple receivers receive the RTS/DATA message from a sender, they respond with the CTS/ACK message spread with pre-assigned code in the same time interval. The proposed scheme can reduce the overhead of multiple CTSs/ACKs. It is also possible to alleviate the received signal strength at the enemy detector and thus it improves low probability of detection performance. Through simulations and analysis, the proposed scheme outperforms that of the multiple CTSs/ACks in terms of the throughput, transmission delay and low probability of detection.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.57-58
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• 2006

Ad hoc MAC protocols using directional antennas can be used to improve the network capacity by improving spatial reuse. But, the directional MAC protocols have the problem of deafness and have a poor throughput performance. The dual-channel DMAC protocol has been proposed to mitigate deafness and improve spatial reuse. In this paper, we propose a dual-channel DMAC protocol using the omnidirectional antenna for an out-of-band tone and directional antennas for control/data channels. In the proposed MAC protocol, an omnidirectional out-of-band tone mitigates deafness and directional antennas used in control/data channels improve spatial reuse and reduce interference packets. The throughput performance of the proposed MAC protocol is confirmed by computer simulations using Qualnet ver. 3.8 simulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.827-833
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• 2011

Directional MAC protocols have drawn great attentions recently in super high speed wireless local/personal area networks due to their higher antenna gain, better spatial reuse, longer transmission range, and lower interference. Despite of these merits, directional MAC protocols suffer from deafness problem. The deafness problem occurs if a node does not answer an RTS frame addressed to it. To overcome this problem, directional MAC protocols have aimed at avoiding the deafness problem using multiple control frames or advance notice techniques or distinguishing deafness from collision. In this paper, we analyze the performance of these schemes in deafness environments with some scenarios. Through performance analysis, we compare the performance of these schemes through evaluating actual network throughput.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.213-216
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• 2007

The paper deals with a approach to underwater acoustic based Ad-hoc communication, which allows major design strategies for Media Access Control (MAC) within a group of the autonomous underwater vehicles(AUV). The proposed MAC aims at deploying AUV-centric star topology, which minimizes overhead of sensor nodes and improves energy-efficiency. Furthermore, that is also well under long and unknown propagation delays of the underwater acoustic medium. The implemented MAC protocol makes it easier to achieve frame synchronization than TDMA due to deploying localized schedule time, in addition to saving energy consumption by letting nodes sleep. It is also superior to MACA and MACAW in terms of propagation delay. This scalable centralized protocol has the potential to serve as a primer for development of MAC protocol for future underwater acoustic based ad-hoc networks.

• Journal of the Korea Society for Simulation
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• v.20 no.4
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• pp.81-89
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• 2011

Underwater wireless network can be useful in various fields such as underwater environment observation, catastrophe prevention, ocean resources exploration, ocean organism research, and vessel sinking exploration. We need to develop an efficient design for Medium Access Control (MAC) protocol to improve multiple data communication in underwater environment. Aloha protocol is one of the basic and simple protocols, but it has disadvantage such as collision occurs oftenly in communication. If there is collision occured in RF communication, problem can be solved by re-sending the data, but using low frequency in underwater, the re-transmission has difficulties due to slow bit-rate. So, Time Division Multiple Access (TDMA) based MAC protocol is going to be used to avoid collisions, but if there is no data to send in existing TDMA, time slot should not be used. Therefore, this paper proposes dynamic TDMA protocol mechanism with reducing the time slots by sending short "I Have No Data" (IHND) message, if there is no data to transmit. Also, this paper presents mathematic analysis model in relation to data throughput, channel efficiency and verifies performance superiority by comparing the existing TDMA protocols.

• Journal of KIISE:Information Networking
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• v.31 no.3
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• pp.327-334
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• 2004

In this paper, we make MAC protocol improvements for performance enhancement of multi-hop ad-hoc wireless networks. A node in ad-hoc wireless networks can transmit a packet only when the medium is available, and while a packet is being transmitted, no other nodes are allowed to transmit a packet if they are in carrier sensing range. Carrier sensing range can be divided into two disjoint areas of transmission range and carrier sensing zone(9), and we address the importance of the protocol behavior when a node is in carrier sensing zone. The characteristic of the carrier sensing zone is that a node can not know when the remaining time of the on-going transmission session expires or exactly when the media becomes available. Current MAC protocol does not behave in much different way between when a node is in transmission range and in carrier sensing zone. We have conducted a comprehensive simulation to study the performance improvements. The simulation results indicate that the performance is increased and the number of dropped packets due to collision is significantly reduced as much as a half.