• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2636-2656
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• 2013

To improve the cooperative efficiency of node cooperation and multiple access performance for multihop wireless networks, a priority-differentiated cooperative medium access control protocol with contention resolution (CRP-CMAC) is proposed. In the protocol, the helper selection process is divided into the priority differentiation phase and the contention resolution phase for the helpers with the same priority. A higher priority helper can choose an earlier minislot in the priority differentiation phase to send a busy tone. As a result, the protocol promptly selects all the highest priority helpers. The contention resolution phase of the same priority helpers consists of k round contention resolution procedures. The helpers that had sent the first busy tone and are now sending the longest busy tone can continue to the next round, and then the other helpers that sense the busy tone withdraw from the contention. Therefore, it can select the unique best helper from the highest priority helpers with high probability. A packet piggyback mechanism is also adopted to make the high data rate helper with packet to send transmit its data packets to its recipient without reservation. It can significantly decrease the reservation overhead and effectively improve the cooperation efficiency and channel utilization. Simulation results show that the maximum throughput of CRP-CMAC is 74%, 36.1% and 15% higher than those of the 802.11 DCF, CoopMACA and 2rcMAC protocols in a wireless local area network (WLAN) environment, and 82.6%, 37.6% and 46.3% higher in an ad hoc network environment, respectively.

• Journal of Communications and Networks
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• v.18 no.2
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• pp.218-226
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• 2016

Coordination among users is an inevitable but time-consuming operation in wireless networks. It severely limit the system performance when the data rate is high. We present FC-MAC, a novel MAC protocol that can complete a contention within one contention slot over a joint frequency-code domain. When a node takes part in the contention, it generates randomly a contention vector (CV), which is a binary sequence of length equal to the number of available orthogonal frequency division multiplexing (OFDM) subcarriers. In FC-MAC, different user is assigned with a distinct signature (i.e., PN sequence). A node sends the signature at specific subcarriers and uses the sequence of the ON/OFF states of all subcarriers to indicate the chosen CV. Meanwhile, every node uses the redundant antennas to detect the CVs of other nodes. The node with the minimum CV becomes the winner. The experimental results show that, the collision probability of FC-MAC is as low as 0.05% when the network has 100 nodes. In comparison with IEEE 802.11, contention time is reduced by 50-80% and the throughput gain is up to 200%.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.165-174
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• 2006

In this paper, we propose a new contention window control algorithm to increase TCP performance in wireless multi-hop networks. The new contention window control algorithm is suggested to reduce the hidden and exposed terminal problems of wireless multi-hop networks. Most of packet drops in wireless multi-hop networks results from hidden and exposed terminal problems, not from collisions. However, in normal DCF algorithm a failed user increases its contention window exponentially, thus it reduces the success probability of fined nodes. This phenomenon causes burst data transmissions in a particular node that already was successful in packet transmission, because the success probability increases due to short contention window. However, other nodes that fail to transmit packet data until maximum retransmission attempts try to set up new routing path configuration in network layer, which cause TCP performance degradation and restrain seamless data transmission. To solve these problems, the proposed algorithm increases the number of back-of retransmissions to increase the success probability of MAC transmission, and fixes the contention window at a predetermined value. By using ns-2 simulation for the chain and grid topology, we show that the proposed algorithm enhances the TCP performance.

• ETRI Journal
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• v.35 no.1
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• pp.58-68
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• 2013

Five-phase reservation protocol (FPRP) is a contention-based media access control protocol for wireless ad hoc networks. FPRP uses a five-phase reservation process to establish slot assignments based on time division multiple access. It allows a node to reserve only one slot in an information frame. Once a node has reserved a slot, it will cease contending for other slots. As a result, there may be less contending nodes in the remaining slots, so the time slots in an information frame are not fully used by FPRP. To improve time slot utilization, this paper proposes an improved pseudo-Bayesian algorithm, based on which an improved contention access mechanism for FPRP is proposed, in which nodes are allowed to contend for more than one slot in a reservation frame according to a certain probability/priority. Simulation results indicate that the proposed mechanism performs better than FPRP in time slot utilization and hence the network throughput under various scenarios.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.330-340
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• 2007

IEEE 802.11 wireless LANs employ the backoff algorithm to avoid contentions among STAs when two or more STAs attempt to transmit their data frames simultaneously. The MAC efficiency can be improved if the CW values are adaptively changed according to the channel state of IEEE 802.11 wireless LANs. In this paper, we propose a dynamic contention window control algorithm using the genetic algorithm to improve the MAC throughput of IEEE 802.11 wireless LANs.

• ETRI Journal
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• v.29 no.5
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• pp.682-684
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• 2007

A new scheme to alleviate contention in optical burst switching networks is proposed. It consists of preventively reserving resources in a node, to be used if resources are busy on the next hop node. The burst is sent back to the preceding node and then resent forward. Simulations are carried out to assess the feasibility of the proposed scheme. Its performance is compared with that of contention resolution based on deflection routing.

• Journal of Korea Multimedia Society
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• v.14 no.2
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• pp.219-227
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• 2011

The superframe structure of IEEE 802.15.4, an international standard for low rate WPAN, is composed of CAP(Contention access period) and CFP(Contention free period). CAP is the contention-based access period, while CFP is contention-free access period for supporting QoS by allocating fixed bandwidth. The standard can support QoS for only a few devices, because the maximum number of GTSs is 7. Furthermore, as the value of BO (Beacon order) or SO (Superframe order) increases, the size of a time slot increases. This makes it difficult to precisely allocate bandwidth for any device, because the bandwidth is allocated by the unit of GTS. The proposed scheme of this paper can reduce the waste of BW in CFP by adaptively reducing the size of a time slot in CFP as the value of BO or SO increases and increase the number of GTSs to 127 by modifying the standard. The performance analysis shows that the proposed scheme can dramatically increase the bandwidth utilization during the CFP when comparing with IEEE 802.15.4.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11B
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• pp.967-973
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• 2004

DOCSIS and IEEE 802.16 define the usage and element of a MAP which is uplink control message. Standards does not include the details of MAP size and the number of contention slots affecting the performance of MAC protocols for DOCSIS and IEEE 802.16. In this paper, we analyzed the performance of throughput and access delay according to the MAP size and contention slot size. Based on the analytical results, we found the optimal MAP size and the number of contention slots. We found that the protocol shows best performance when the MAP size is 2msec and the number of contention slots is 8. The simulation results can apply to the network system parameters. The simulator can be used to optimize the system parameters in cable network, BWA and WiBro.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.5835-5854
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• 2017

The implementation of IEEE 802.15.6 in Wireless Body Area Network (WBAN) is contention based. Meanwhile, IEEE 802.15.4 MAC provides limited 16 channels in the Superframe structure, making it unfit for N heterogeneous nature of patient's data. Also, the Beacon-enabled Carrier-Sense Multiple Access/Collision-Avoidance (CSMA/CA) scheduling access scheme in WBAN, allocates Contention-free Period (CAP) channels to emergency and non-emergency Biomedical Sensors (BMSs) using contention mechanism, increasing repetition in rounds. This reduces performance of the MAC protocol causing higher data collisions and delay, low data reliability, BMSs packet retransmissions and increased energy consumption. Moreover, it has no traffic differentiation method. This paper proposes a Low-delay Traffic-Aware Medium Access Control (LTA-MAC) protocol to provide sufficient channels with a higher bandwidth, and allocates them individually to non-emergency and emergency data. Also, a Contention Differentiated Adaptive Slot Allocation CSMA-CA (CDASA-CSMA/CA) for scheduling access scheme is proposed to reduce repetition in rounds, and assists in channels allocation to BMSs. Furthermore, an On-demand (OD) slot in the LTA-MAC to resolve the patient's data drops in the CSMA/CA scheme due to exceeding of threshold values in contentions is introduced. Simulation results demonstrate advantages of the proposed schemes over the IEEE 802.15.4 MAC and CSMA/CA scheme in terms of success rate, packet delivery delay, and energy consumption.

• Journal of the Daesoon Academy of Sciences
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• v.33
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• pp.257-286
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• 2019

This study aims to explain theodicy in Daesoon Jinrihoe using established theodicies. Theodicy in Daesoon Jinrihoe can be described as follows: within the worldview of Daesoon Jinrihoe, the problems of evil and suffering are better addressed by analyzing the problem of mutual contention. Accordingly, theodicy in Daesoon Jinrihoe is a matter which should be discussed only in regards to the time period known as the Former World and the transition period after the Reordering Works that leads up to the Later World. The Later World does not operate under patterns of mutual contention. Consequently, there will be no suffering. Therefore, issues of theodicy are irrelevant in the Later World. Theodicy should be dealt differently as it pertains to the Former World and the previously mentioned transition period. Daesoon Thought posits that there is an underlying principle presides over the cosmos, and the divine beings act in accordance with it and perform specific duties in their own subdivisions. The cosmic principle is able to contain cycles of both Sanggeuk ('mutual destruction' in general usage, but 'mutual contention' in Daesoon Thought related to the Former World) and sangsaeng ('mutual generation' in general usage and 'mutual beneficence' in Daesoon Thought related to the Later World). Suffering came into being due to mutual contention. However, mutual contention was not set into motion maliciously, but was arranged instead to facilitate the realization of greater values such as growth and development. In other words, mutual contention are not products of a moral value the nature of which is bad or wrong. Yet, since the world has operated under mutual contention from time immemorial, a nearly incalculably vast multitude of grievances have accumulated. In addition, the divine beings who had operated under mutual contention often made mistakes and spread confusion. This extreme situation resulted in tremendous disasters breaking out all over the world. Perhaps this particular theodicy could be named "Dualistic Sanggeuk Theology (Dualistic Theodicy of Mutual Contention)." After the divine beings reported to the Supreme God that the world had fallen into a serious crisis, the Supreme God penetratingly examined the circumstances of the world and then descended to Earth as a human being named Jeungsan. As Jeungsan practiced the Reordering Works of Heaven and Earth, the Great Opening was preordained by Him. As a result, the transition period started, and from that point onward, theodicy should be described differently. It is presumed that all creatures will be judged at the time of the Great Opening. This will result in the annihilation of all wicked beings including both divine beings and humans. There will also be the establishment of an earthly paradise as well as grievance resolution for all beings prior the Great Opening. This can also be called "The Eschatological Theodicy of the Resolution of Grievances." Theodicy in Daesoon Jinrihoe adopts the two theodicies mentioned above. In addition to that, various theodicies from other traditions such as Irenaean ("soul-making") Theodicy, Free Will Theodicy, Recompense Theodicy, Afterlife Theodicy, Karma Samsara Theodicy, theodicy of participation, and Communion Theodicy can all potentially be applied on a case by case basis.