• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1130-1137
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• 2006

One of the important performance issues in large-scale RFID systems is to resolve collisions among responses from RFID tags. Considering two do facto anti-collision solutions, namely the binary-tree splitting algorithm and the Slotted-Aloha algorithm, we propose to use multi-packet reception (MPR) capability to enhance the RFID tag reading rate (i.e., throughput). MPR allows an RFID reader to receive multiple reponses transmitted by tags at the same time. We analyze the effect of MPR capability in the above anti-collision algorithms, which is also validated by simulation. The analysis and simulation results show that RFID reader antenna design and signal separation techniques play an important role in improving RFID system performance with MPR capability.

• Journal of Sensor Science and Technology
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• v.19 no.4
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• pp.297-305
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• 2010

A home healthcare system based wireless sensor network, which can continuously monitor and manage the elderly's electrocardiogram(ECG) signal at any space at home without space limit is proposed. The communication coverage of wireless network is expended by multi-hop wireless sensor network. In order to send the elderly's ECG data wirelessly, a small size ECG sensor node was designed to forward the ECG data over multi-hop relay network. The packet acquired by mobile ECG node is transmitted through wireless intermediate nodes to base station for analyzing the packet reception rate. Modified minimum cost forwarding(MMCF) protocol and flooding protocol are designed and implemented to check the transmission efficiency of a packet in a wireless sensor network. The developed MMCF protocol shows an advantage of high reception rate by reduced network traffic.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.455-462
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• 2009

In this paper, we propose a buffer management scheme for decreasing the packet loss due to buffer overflow and improving the packet fairness between nodes in IEEE 802.11 based multi-hop mesh networks. In the proposed scheme, each mesh router that is an intermediate node receives fairly packet sent from neighboring mesh routers and mobile nodes, and it improves the reception ratio of multi-hop traffic of neighboring mesh routers. Therefore, the proposed scheme can reduce transmission delay and energy consumption. In order to improving the packet loss and the packet fairness, the proposed scheme uses the modified RTS/CTS under the IEEE 802.11 MAC protocol and reduces the packet loss by recognizing the packet size to send to the destination in advance. By using the simulation, we evaluated the proposed scheme in terms of the packet loss ratio and the number of received packet in each mesh router, and compare it to a traditional scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.6
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• pp.446-453
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• 2013

Clustering schemes have been adopted as an efficient solution to prolong network lifetime and improve network scalability. In such clustering schemes cluster ratio is represented by the rate of the number of cluster heads and the number of total nodes, and affects the performance of clustering schemes. In this paper, we mathematically analyze an optimal clustering ratio in wireless sensor networks. We consider a multi-hop to one-hop transmission case and aim to provide the optimal cluster ratio to minimize the system hop-count and maximize packet reception ratio between nodes. We examine its performance through a set of simulations. The simulation results show that the proposed optimal cluster ratio effectively reduce transmission count and enhance energy efficiency in wireless sensor networks.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.317-329
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• 1998

In this paper, we have analyzed the packet error probability of DS/CDMA-Trellis Coded QPSK modulation signal with MRC(Maximum Ratio Combining) diversity reception in Rician fading, multi-user interferences and multipath channel. And then we have evaluated the performance and capacity of DS/CDMA-Trellis Coded QPSK system using the MRC diversity reception as a function of direct power to indirect power ratio ($K_R$), the number of diversity branch(M), the number of multi-user(U), PN chip rate(PN), the number of multipath channel($L_P$), and packet length(PL). From the results, we know that the coding gain of DS/CDMA-Trellis Coded QPSK system with 2 branch MRC diversity is about 6 dB against uncoded DS/CDMA BPSK system with 2 branch MRC diversity in Rician fading ($K_R=6dB), 5 multi-user interferences, and 3 multipath channel. And, we know that coded QPSK signal designed for the AWGN channel also perform well on a Rician fading channel with MRC diversity reception. Consequently, we expected that proposed system structure is reliable to the wireless data communication system in Rician fading, multi-user interferences, and multipath channel.

• Journal of Communications and Networks
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• v.13 no.5
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• pp.525-535
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• 2011

In this paper, we study the contribution of network coding (NC) in improving the multicast capacity of random wireless ad hoc networks when nodes are endowed with multi-packet transmission (MPT) and multi-packet reception (MPR) capabilities. We show that a per session throughput capacity of ${\Theta}$(nT$^3$(n)) can be achieved as a tight bound when each session contains a constant number of sinks where n is the total number of nodes and T(n) is the transmission range. Surprisingly, an identical order capacity can be achieved when nodes have only MPR and MPT capabilities. This result proves that NC does not contribute to the order capacity of multicast traffic in wireless ad hoc networks when MPR and MPT are used in the network. The result is in sharp contrast to the general belief (conjecture) that NC improves the order capacity of multicast. Furthermore, if the communication range is selected to guarantee the connectivity in the network, i.e., ${\Omega}$($\sqrt{log\;n/n}$)=T(n) = O(log log n / log n), then the combination of MPR and MPT achieves a throughput capacity of ${\Theta}$(log$^{\frac{3}{2}}$ n/$\sqrt{n}$) which provides an order capacity gain of ${\Theta}$(log$^2$ n) compared to the point-to-point multicast capacity with the same number of destinations.

• Journal of Information Processing Systems
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• v.13 no.5
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• pp.1229-1242
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• 2017

In this paper, an interference aware distributed multi-channel MAC (IDMMAC) protocol is proposed for wireless sensor and actor networks (WSANs). The WSAN consists of a huge number of sensors and ample amount of actors. Hence, in the IDMMAC protocol a lightweight channel selection mechanism is proposed to enhance the sensor's lifetime. The IDMMAC protocol divides the beacon interval into two phases (i.e., the ad-hoc traffic indication message (ATIM) window phase and data transmission phase). When a sensor wants to transmit event information to the actor, it negotiates the maximum packet reception ratio (PRR) and the capacity channel in the ATIM window with its 1-hop sensors. The channel negotiation takes place via a control channel. To improve the packet delivery ratio of the IDMMAC protocol, each actor selects a backup cluster head (BCH) from its cluster members. The BCH is elected based on its residual energy and node degree. The BCH selection phase takes place whenever an actor wants to perform actions in the event area or it leaves the cluster to help a neighbor actor. Furthermore, an interference and throughput aware multi-channel MAC protocol is also proposed for actor-actor coordination. An actor selects a minimum interference and maximum throughput channel among the available channels to communicate with the destination actor. The performance of the proposed IDMMAC protocol is analyzed using standard network parameters, such as packet delivery ratio, end-to-end delay, and energy dissipation, in the network. The obtained simulation results indicate that the IDMMAC protocol performs well compared to the existing MAC protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.7
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• pp.612-622
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• 2013

In this paper, we propose a coding packet group-based ARQ scheme (rNC) for file delivery in wireless networks. rNC assumes multiple network coding points between the source and the destination. Each network coding point gathers and codes a group of packets according to the queue polling system. A queue polling system makes a few or several packets available for coding in a queue while polling the other queues in the system. Thus, we assuem a queue polling system at each network coding point. We call this group of packets as coded packet group. Each coding point acknowledges the reception of every code packet group to its previous coding point for reliable delivery. Thus, the intermediate coding points including the source can release its buffer before the packet is delivered to the destination. To guarantee the ultimate file delivery to the destination, the destination sends acknowledgement to the sender. We evaluate our proposed scheme using ns-2 and compare the performance with CodeCast. The results show that rNC works better than CodeCast in terms of packet delivery ratio and control overhead in unreliable wireless networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10B
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• pp.1043-1049
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• 2009

Broadcast of sink node is used for network management, data collection by query and synchronization in wireless sensor networks. Simple flooding scheme induces the broadcast storm problem. The MPR based broadcast schemes reduce redundant retransmission of broadcast packets. MPR is a set of one hop neighbor nodes which have to relay broadcast message to cover all two hop neighbors. Though MPR can reduce redundant retransmission remarkably, it still suffers from energy waste problem caused by collision and duplicate packets reception. This paper proposes a new MPR based sink broadcast scheme using 3-channel. The proposed scheme reduces energy consumption by avoiding duplicate packet reception, while increases reliability by reducing collision probability remarkably. The results of analysis and simulation show that the proposed scheme is more efficient in energy consumption compared to the MPR based scheme. The result also shows that the proposed scheme reduces delivery latency by evading a contention with other relay nodes and improves reliability of broadcast message delivery by reducing collision probability.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.4
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• pp.1679-1691
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• 2016

Successive interference cancellation (SIC) is an effective means of multi-packet reception to combat interference at the physical layer. We investigate the joint optimization issue of channel access and power control for capacity maximization in SIC-enabled wireless networks. We propose a new interference model to characterize the sequential detection nature of SIC. Afterward, we formulize the joint optimization problem, prove it to be a nondeterministic polynomial-time-hard problem, and propose a novel approximation approach based on the genetic algorithm (GA). Finally, we discuss the design and parameter setting of the GA approach and validate its performance through extensive simulations.