• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1104-1113
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• 2014

Future combat systems can be represented as the NCW (Network Centric Warefare), which is based on the concept of Sensor-to-Shooter. A wireless video sensor networking technology, one of the core components of NCW, has been actively applied for the purpose of tactical surveillance. In such a surveillance sensor network, multi-composite sensors, especially consisting of image sensors are utilized to improve reliability for intrusion detection and enemy tracing. However, these sensors may cause a problem of requiring very high network capacity and energy consumption. In order to alleviate this problem, this paper proposes an image data transmission scheme based on resource reservation. The proposed scheme can make it possible to have more reliable image data transmission by choosing proper multiple interfaces, while trying to control resolution and compression quality of image data based on network resource availability. By the performance analysis using NS-3 simulation, we have confirmed the transmission reliability as well as energy efficiency of the proposed scheme.

• Journal of Information Processing Systems
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• v.5 no.4
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• pp.207-220
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• 2009

A large number of phone calls and data services will take place in indoor environments. In Long Term Evolution (LTE), femtocell, as a home base station for indoor coverage extension and wideband data service, has recently gained significant interests from operators and consumers. Since femtocell is frequently turned on and off by a personal owner, not by a network operator, one of the key issues is that femtocell should be identified autonomously without system information to support handover from macrocell to femtocell. In this paper, we propose a dynamic reservation scheme of Physical Cell Identities (PCI) for 3GPP LTE femtocell systems. There are several reserving types, and each type reserves a different number of PCIs for femtocell. The transition among the types depends on the deployed number of femtocells, or the number of PCI confusion events. Accordingly, flexible use of PCIs can decrease PCI confusion. This reduces searching time for femtocell, and it is helpful for the quick handover from macrocell to femtocell. Simulation results show that our proposed scheme reduces average delay for identifying detected cells, and increases network capacity within equal delay constraints.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.126-130
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• 1999

In packet CDMA networks, it is important to design a MAC protocol that meets the QoS requirements , of the different traffic types and allocates the radio channels efficiently. In this paper, a RRS$^2$-CDMA MAC protocol is proposed for integrating voice and data services in the microcellular packet CDMA networks. In PRS$^2$-CDMA, a voice terminal can resolve a spreading code to transmit voice packets during a talkspurt while a data terminal has to contend for a code for each packet transmission. The numerical results show that the proposed protocol can improve the system capacity, while guaranteeing the QoS of voice and data services.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.1
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• pp.16-27
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• 2012

In multi-interface multi-channel(MIMC) based tactical ad hoc networks, QoS support for required operational capacity is one of the main challenging issues for multi-hop transmissions. To support QoS in such a harsh environment, we propose a novel MAC scheme to minimize multi-hop as well as per-hop delay. The current IEEE 802.11 MAC protocols should contend to reserve the channel resource at every hop by each sender. The every-hop channel contention results in a degradation of end-to-end delay for multi-hop transmissions. The basic idea of our scheme is to make a "multi-hop reservation" at the MAC layer by using the modified RTS frame. It contains additional information such as destination information, packet priority, and hop count, etc. In addition, we differentiate the contention window area according to the packet priority and the number of hops to deliver packets in the predefined allowed latency. Our scheme can minimize the multi-hop delay and support the QoS of the critical data in real time(i.e., VoIP, sensing video data, Video conference between commanders). Our simulation study and numerical analysis show that the proposed scheme outperforms the IEEE 802.11 MAC.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.10
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• pp.33-51
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• 1997

On ATM-based wired/wireless integrated network, we apply the connection re-routing method[1] which reduced the inter-cluster handoff delay by reserving VPI/VCLs for possible inter-cluster handoff calls in advance. Additionally, we propose wired resource reservation methods, which are ausiliary method and split method, for handoff QoS guarantee of various expected services. The characteristics of these methods reserve wired connection resources based on the information on the possible inter-cluster handoff calls. With mathematical analysis, we also propose each algorithm and cost function for deciding an optimal amount in reserving resources. With numberical examples, we can see that the auxiliary method effectively reduces the cost in all cases(.alpha.>.betha., .alpha.=.betha., and .alpha.<.betha.). The split method has a little cost-reduction effects, when handoffs call does not have priority over new calls (that is, .alpha..leq..betha.) and the total capacity is relatively large. In other cases, the split method, however, has effective cost-reduction effects. The numerical resutls show that these reservation methods ca flexibly cope with the time-variant environment and meet the QoS requriements on the inter-cluster handoff calls.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.5
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• pp.55-64
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• 1996

This paper presents performance evaluation of a new high speed inter-processor communication(HIPC) network for large capacity and high performance digitral switching system. The HIPC structure implements the fast reservation and concurrent arbitration technique (modified round-robin arbitration). The performance evaluation of HIPC was performed by not only computer simulation but also numerical approximation method which was derived for a single server multi-queue system with nonexhaustive cyclic service. The approximation results are almost same with that of computer simulation. The TDX-10 basic callscenario was applied to the HIPC netowrk and analyzed. these results were compared with TDX-10 IPC and shows that the difference of th emean waiting time in the TX buffer of NTP node increases sharply according to the increase of the message arrival rate.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.130-139
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• 2014

Due to the unpredictable nature of channel availability, carrying delay-sensitive traffic in cognitive radio networks (CRNs) is very challenging. Spectrum leasing of radio resources has been proposed in the so called coordinated CRNs to improve the quality of service (QoS) experienced by secondary users (SUs). In this paper, the performance of coordinated CRNs under fixed-rate with hard-delay-constraints traffic is analyzed. For the adequate and fair performance comparison, call admission control strategies with fractional channel reservation to prioritize ongoing secondary calls over new ones are considered. Maximum Erlang capacity is obtained by optimizing the number of reserved channels. Numerical results reveal that system performance strongly depends on the value of the mean secondary service time relative to the mean primary service time. Additionally, numerical results show that, in CRNs without spectrum leasing, there exists a critical utilization factor of the primary resources from which it is not longer possible to guarantee the required QoS of SUs and, therefore, services with hard delay constraints cannot be even supported in CRNs. Thus, spectrum leasing can be essential for CRN operators to provide the QoS demanded by fixed-rate applications with hard delay constraints. Finally, the cost per capacity Erlang as function of both the utilization factor of the primary resources and the maximum allowed number of simultaneously rented channels is evaluated.

• Journal of the Korean Operations Research and Management Science Society
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• v.31 no.3
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• pp.145-154
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• 2006

WiBro (Wireless Broadband Internet) system is going to be 9ot down to commercialization. The high portable internet system is able to be connected to the high-speed internet using 2.3 GHz frequency bandwidth, anytime and anywhere. An effective scheduling for UGS, rtPS, nrtPS and BE requiring different QoS, which are service types of the WiBro, is necessary to increase the efficiency of radio channels that are the limiting resource. This paper researches an uplink scheduling that plays a role in assignment for the radio channels from subscribers to base stations. The suggested scheduling provides priorities with each service type considering QoS of them but reserves some bandwidth for lower priory services. After deciding effective amount of bandwidth for reservation, we suggest analytical result on mean delayed time of packet transmission for each terminal, transmission rate for the data, and capacity for uplink. This research can be used as basic data for the standard in the high portable internet system and as data to predict the capacity of base stations.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.10a
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• pp.347-353
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• 2005

WiBro (Wireless Broadband Internet) system is going to be commercialized before long. The high portable internet system is abie to be connected to the high-speed internet using 2.3 CHz frequency bandwidth, anytime and anywhere. An effective scheduling for UCS, rtPS. nrtPS and BE requiring different QoS, which are service types of the WiBro, is necessary to increase the efficiency of radio channels that arc the limiting resource. This paper researches an uplink scheduling that plays a role in assignment for the radio channels from subscribers to base stations. The suggested scheduling provides priorities With each service type considering QoS of them but reserves some bandwidth for lower priory services. After deciding effective amount of bandwidth for reservation, we suggest analytical result on mean delayed time of packet transmission for each terminal, transmission rate for the data, and capacity for uplink. This research can be used as basic data for the standard in the high portable internet system and as data to predict the capacity of base stations.

• Journal of information and communication convergence engineering
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• v.12 no.2
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• pp.109-115
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• 2014

This paper presents a concurrent channel time allocation scheme used in the reservation period for concurrent transmissions in 60-GHz wireless personal area networks (WPANs). To this end, the proposed resource allocation scheme includes an efficient method for creating a concurrent transmission group by using a table that indicates whether individual streams experience interference from other streams or not. The coordinator device calculates the number of streams that can be concurrently transmitted with each stream and groups them together on the basis of the calculation result. Then, the coordinator device allocates resources to each group such that the streams belonging to the same group can transmit data concurrently. Therefore, when the piconet coordinator (PNC) allocates the channel time to the individual groups, it should allow for maximizing the overall capacity. The performance evaluation result demonstrates that the proposed scheme outperforms the random grouping scheme in terms of the overall capacity when the beamwidth is $30^{\circ}C$ and the radiation efficiency is 0.9.