• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1216-1224
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• 2009

This paper presents cross-layer based packet scheduling and routing algorithm to effectively transmit delay-sensitive multimedia data over mobile ad hoc network. At first, packet urgency, node urgency, and route urgency are defined based on the end-to-end delay requirement of each packet and the number of hops over a route. Based on the urgency metric, the proposed transmission scheme is that packet scheduling algorithm at the MAC layer and routing algorithm at the network layer are tightly-coupled to improve the transmission performance for delay-sensitive multimedia. Finally, simulation results are provided to show the performance of proposed transmission scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.1075-1082
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• 1997

In this paper, we propose a channel assignment scheme for reducing call blocking rate in a base station(BS) of DS-CDMA cellular systems. The proposed scheme can e applied to the case where the capacity of reverse radio link is enough, but not are the available traffic channels performing the digital modulation and demodulation functions between a mobile station and the base station. The proposed scheme takes advantage of the feature of soft handoff in which a mobile station keeps its communication link even if one of the two communication links is released. The scheme estimates the mean and variance of the received power level measured at the base station before assigning a traffic channel for a new call request. The BS makes decision based on the estimated balues whether the new call request will be accepted or not. If it is decided that the capacity of reverse radio link is enough, but all traffic channels are not available, then the BS increases the soft handoff parameter T_DROP to release the traffic channels of mobile stations loactedin soft handoff area. The BS assigns the released traffic channel to anew call or a handoff call. The performance of the proposed channel assignment scheme is evaluated by computer simulation. The results show that the call blocking rate for new calls and handoff calls is reduced.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.371-376
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• 2008

In this paper, we explain the unified inter-cell interference avoidance and cancellation in OFDM mobile cellular systems. Interference avoidance is used for cell-interior or two-cell-edge users, and interference cancellation is applied to three-cell-edge users. The performance of the unified scheme is evaluated by simplified system simulation. Link simulation results are used in the interpretation of system simulation output. We compare three schemes which are "no interference management," "only interference avoidance," "both avoidance and cancellation." Primary performance measures are the data rate of the 5th percentile user and the mean data rate. Simulation results show that interference management schemes greatly improve the cell edge performance, but slightly reduce the mean data rate. Use of both avoidance and cancelaltion is better than that of only avoidance in terms of the cell edge throughput and the mean data rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.1
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• pp.34-45
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• 2013

Due to its self-configuring nature, the tactical mobile ad hoc network is used for communications between tactical units and the command and control center (CCC) in battlefields, where communication infrastructure is not available. However, when a tactical unit moves far away from the CCC or there are geographical constraints, the data link between two communicating nodes can be broken, which results in an invalid data route from the tactical units to CCC. In order to address this problem, in this paper we propose a hierarchical connectivity maintenance scheme, namely ADLCoM (Autonomous Data Link Connectivity Maintenance). In ADLCoM, each tactical unit has one or more GW (gateway), which checks the status of data links between tactical units. If there is a possibility of link breakage, GWs request ground or aerial unmanned vehicles to become a relay for the data link. The simulation results, based on tactical scenarios, show that the proposed scheme can significantly improve the network performance with respect to data delivery ratio.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.106-113
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• 2008

In this paper, we propose an Entropy-based Cooperative-Aided Routing Protocol (ECARP) in Mobile Ad-hoc fireless Sensor Networks (MAWSN). The main contributions and features of this paper are as follows. First, the entropy-based cooperative routing protocol which is based on node mobility is proposed for supporting stable routing route construction. Second, cooperative data transmission method is used for improving data transmission ratio with the improved SNR. Third, we consider a realistic approach, in the points of view of the MAWSN, based on mobile sensor nodes as well as fixed sensor nodes in sensor fields while the conventional research for sensor networks focus on mainly fixed sensor nodes. The performance evaluation of the proposed routing protocol is performed via simulation and analysis.

• Journal of Communications and Networks
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• v.7 no.4
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• pp.489-498
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• 2005

For better performance over a noisy channel, mobile wireless networks transmit packets with forward error correction (FEC) code to recover corrupt bits without retransmission. The static determination of the FEC code size, however, degrades their performance since the evaluation of the underlying channel state is hardly accurate and even widely varied. Our measurements over a wireless sensor network, for example, show that the average bit error rate (BER) per second or per minute continuously changes from 0 up to $10^{-3}$. Under this environment, wireless networks waste their bandwidth since they can't deterministically select the appropriate size of FEC code matching to the fluctuating channel BER. This paper proposes an adaptive FEC technique called adaptive FEC code control (AFECCC), which dynamically tunes the amount of FEC code per packet based on the arrival of acknowl­edgement packets without any specific information such as signal to noise ratio (SNR) or BER from receivers. Our simulation experiments indicate that AFECCC performs better than any static FEC algorithm and some conventional dynamic hybrid FEC/ARQ algorithms when wireless channels are modeled with two-state Markov chain, chaotic map, and traces collected from real sensor networks. Finally, AFECCC implemented in sensor motes achieves better performance than any static FEC algorithm.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.64-68
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• 2010

In this paper, we studied the novel synchronization algorithm for cooperative communication system over fading. We research mainly on the decode-and-forward scheme. Also, we inserted spreading sequence in origin data frame to control efficiently data synchronization. In mobile station, inserted spreading sequence in data frame passed through the corelation process. We had decide the delay value of received data through result of correlation process. In simulation, We applied that channel gain of three node had different value in various fading environment. Finally we will be possible to control the received data synchronization using result of corelation value in each node between relay to mobile station and base station to mobile station. The results of this paper can be applicable to the cooperative systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9A
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• pp.898-904
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• 2007

I must receive node discernment address for communication between node that participate to network in MANETs(Mobile Ad-hoc Networks). Address is created by node confidence or different node. I achieve address redundancy check (Duplicate Address Detection) to examine whether this address is available unique address. However, this method happens problem that MANETs' extensity drops. This paper can manage by group unit binding transfer nodes to group in MANETs. I suggest method that apply special quality of cluster that exchange subordinate decrease and mobility government official of control message are easy in address assignment protocol minimize time required in redundancy check and solves extensity problem. Method that propose in this paper shows excellent performance according to node number increase than wave and MANETConf [2] through simulation.

• Journal of information and communication convergence engineering
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• v.7 no.3
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• pp.309-313
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• 2009

In this paper, end-to-end VoIP(Voice over Internet Protocol) performance is evaluated by simulation with NS-2 simulation tool. There are many results studied and published for VoIP performance over TCP/IP networks. But, almost all of them were focused on wired or wireless Internet environments. About MANET (Mobile Ad Hoc Network), VoIP is currently studying several points of research. In this paper, analysis of VoIP performance is done with focusing on the mobility of MANETs. MOS(Mean Opinion Score), network delay, packet loss rates are considered as end-to-end QoS performance parameters.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.4
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• pp.334-342
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• 2014

Military communications for future warfare have limited resources but highly requirements. MANET has a lot of advantages for future military network due to easily deploying without infrastructure and supporting dynamic topology in restricted environments. But, one of the biggest issues for MANET is difficulty of transmitting data due to link failure in dynamic topology. Content Centric Networking is a future Internet paradigm which solves various IP network problem. In this paper, we propose a future military communication routing scheme using CCN in military tactical MANET. Simulation results show our scheme gets lower control message overhead and faster data downloads as number of node increases and mobile speed increases than other two schemes.