• Journal of KIISE:Information Networking
• /
• v.29 no.6
• /
• pp.595-612
• /
• 2002

One of the most important issues in guaranteeing the high degree of QoS on mobile computing is how to reduce hand-off drops caused by lack of available bandwidth in a new cell. Each cell can request bandwidth reservation to its adjacent cells for hand-off calls. This reserved bandwidth can be used only for hand-offs, not for new calls. It is also important to determine how much of bandwidth should be reserved for hand-off calls because reserving too much would increase the probability of a new call being blocked. Therefore, it is essential to develop a new mechanism to provide QoS guarantee on a mobile computing environment by reserving an appropriate amount of bandwidth and call admission control. In this paper. bandwidth reservation and call admission control mechanisms are proposed to guarantee a consistent QoS for multimedia traffics on a mobile computing environment. For an appropriate bandwidth reservation, we propose an adaptive bandwidth reservation mechanism based on an MPP and a 2-tier cell structure. The former is used to predict a next move of the client while the latter to apply our mechanism only to the client with a high hand-off probability. We also propose a call admission control that performs call admission test only on PNC(Predicted Next Cell) of a client and its current cell. In order to minimize a waste of bandwidth caused by an erroneous prediction of client's location, we utilize a common pool and QoS adaptation scheme. In order evaluate the performance of our call admission control mechanism, we measure the metrics such as the blocking probability of new calls, dropping probability of hand-off calls, and bandwidth utilization. The simulation results show that the performance of our mechanism is superior to that of the existing mechanisms such as NR-CAT2, FR-CAT2, and AR-CAT2.

• Journal of KIISE:Information Networking
• /
• v.34 no.5
• /
• pp.396-404
• /
• 2007

In this paper, an Ad-hoc Routing Protocol which works in wireless Ad-hoc communication networks with multiple radios and multiple channels, and controls call admission based on bandwidth measurement is proposed. Unlike the conventional Ad-hoc node with a single radio using a single channel, an Ad-hoc node of the protocol proposed, MCQosR(Multiple Channel Quality of Service Routing), has multiple radios and uses multiple channels, which makes full duplex transmission between wireless Ad-hoc nodes, and reduces the intra interference on a route. Also, a fixed channel only for reception at each node enables the measurement of the available bandwidth, which is used to control the call admission for QoS provision. The performance of MCQosR is verified by simulation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.3B
• /
• pp.232-238
• /
• 2006

We propose a novel call admission control scheme which improves the handoff drop and the new call block probabilities of high priority services, minimizing the negative impact on low priority services, in multimedia service cellular networks. This paper proposes three schemes to solve this problem; the packing scheme in which available channels of a cell distributed to each frequency channel are concentrated on one frequency channel and a high transmission rate service is assigned to the frequency channel; the queuing scheme in which the queue is used for high transmission rate calls; and the power reallocation scheme in which the power assigned to calls under service is temporarily reduced and a high transmission rate service is allowed. The simulation results revealed that our scheme improved the drop and the block probabilities of the high priority services compared with the conventional scheme.

• Journal of Communications and Networks
• /
• v.13 no.2
• /
• pp.102-112
• /
• 2011

In this paper, we propose a privacy-preserving emergency call scheme, called PEC, enabling patients in life-threatening emergencies to fast and accurately transmit emergency data to the nearby helpers via mobile healthcare social networks (MHSNs). Once an emergency happens, the personal digital assistant (PDA) of the patient runs the PEC to collect the emergency data including emergency location, patient health record, as well as patient physiological condition. The PEC then generates an emergency call with the emergency data inside and epidemically disseminates it to every user in the patient's neighborhood. If a physician happens to be nearby, the PEC ensures the time used to notify the physician of the emergency is the shortest. We show via theoretical analysis that the PEC is able to provide fine-grained access control on the emergency data, where the access policy is set by patients themselves. Moreover, the PEC can withstandmultiple types of attacks, such as identity theft attack, forgery attack, and collusion attack. We also devise an effective revocation mechanism to make the revocable PEC (rPEC) resistant to inside attacks. In addition, we demonstrate via simulation that the PEC can significantly reduce the response time of emergency care in MHSNs.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.13
• /
• pp.5143-5147
• /
• 2014

Cervical cancer screening in Malaysia is by opportunistic Pap smear which contributes to the low uptake rate. To overcome this, a pilot project called the SIPPS program (translated as information system of Pap smear program) had been introduced whereby women aged 20-65 years old are invited for Pap smear and receive recall to repeat the test. This study aimed at determining which recall method is most cost-effective in getting women to repeat Pap smear. A randomised control trial was conducted where one thousand women were recalled for repeat smear either by registered letter, phone messages, phone call or the usual postal letter. The total cost applied for cost-effectiveness analysis includes the cost of sending letter for first invitation, cost of the recall method and cost of two Pap smears. Cost-effective analysis (CEA) of Pap smear uptake by each recall method was then performed. The uptake of Pap smear by postal letter, registered letters, SMS and phone calls were 18.8%, 20.0%, 21.6% and 34.4%, respectively (p<0.05). The CER for the recall method was lowest by phone call compared to other interventions; RM 69.18 (SD RM 0.14) compared to RM 106.53 (SD RM 0.13), RM 134.02 (SD RM 0.15) and RM 136.38 (SD RM 0.11) for SMS, registered letter and letter, respectively. ICER showed that it is most cost saving if the usual method of recall by postal letter be changed to recall by phone call. The possibility of letter as a recall for repeat Pap smear to reach the women is higher compared to sending SMS or making phone call. However, getting women to do repeat Pap smear is better with phone call which allows direct communication. Despite the high cost of the phone call as a recall method for repeat Pap smear, it is the most cost-effective method compared to others.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.2413-2417
• /
• 2003

This paper proposes an improvement of a QoS based routing protocol. The hierarchical source routing algorithm[4] was improved by including of the Crank-Back algorithm[2]. The Crank-Back capability is the ability to solve the problem of selecting the wrong route because of using unsynchronized routing information in the ingress router. In order to reduce time of reversing the call-setup process back to the ingress router, spare-route information is included with a call-setup packet. Spare-route information could be used by every router to find the next appropriated link itself when insufficient resource of the selected link was found. The proposed algorithm improves the performance of the source routing call-setup process significantly.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.12 no.2
• /
• pp.119-131
• /
• 2008

The paper considers the computation method in the performance evaluation of cellular network in the phase-type distribution assumptions that the channel holding times induced from mobility are modeled by well-fitted distributions to reflect an actual situation. When ww consider a phase-type distribution model instead of exponential distribution, the complexity of the computation increase exponential even though the accuracy is improved. We consider an efficient numerical algorithm to compute the performance evaluations in cellular networks such as a handoff call dropping probability, new call blocking probability, and handoff arrival rate. Numerical experiment shows that numerical analysis results are well approximated to the results of simulation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.2
• /
• pp.322-330
• /
• 1994

SIBs(Service Independent Building block) are defined in CCITT advanced intelligent network concept model for supporting various services in the future. This paper describes the protocol modeling and verification for basic call process SIB. For modeling, we use Petri Net and verify this modeling by analyzing reachability tree of Petri Net. Results of this paper should be used for design and implementation of basic call process SIB.

• Journal of Electrical Engineering and information Science
• /
• v.3 no.1
• /
• pp.21-27
• /
• 1998

In this paper we apply routing algorithms in circuit switched networks to B-ISDN networks and investigate the performance. B-ISDN supports a wide range of services with hetrogeneous bandwidth requirements. We assume that the network supports D classes of traffic. It is modeled as a finite D dimensional Markov chain. A call is blocked on arrival if the required bandwidth is not available on the route. The shortest path routing, alternate routing and trunk reservation are considered for performance comparison. We also consider trunk reservation with restricted access control where the network reserves certain amount of bandwidths for one class of traffic that assumes a higher transmission priority. Through the method of successive iterations, we obtain the steady state equilibrium probabilities and call blocking probabilities for dynamic routing. The results can be used to design a B-ISDN network that improves network connection availability and efficiency while simultaneously reducing the network costs.

• Proceedings of the Korean Information Science Society Conference
• /
• 2006.10d
• /
• pp.671-676
• /
• 2006

차세대 이동 네트워크에서는 다양한 무선 접속 기술이 공존하게 된다. 이에 따라, 다양한 무선망을 지원하기 위한 분산방식의 호 수락 제어 구조인 SmartCAC를 제안한다. 우리는 네트워크간 정보 수집이 필요없는 분산방식을 위하여 모바일노드와 네트워크간의 상호동작을 이용한다. SmartCAC는 기본적으로 VHO call과 new call의 구분을 가능하도록 함으로써 VHO call에 handoff를 위해 예약된 채널을 사용할 수 있도록 한다. 또한, 이종망에서 네트워크 필터링을 할 수 있도록 모바일노드의 스피드를 이용한다. 이 때 효율적인 호 수락 제어 방식을 위하여 QoS 요구와 네트워크 사용에 대한 cost를 다룬다. 특히 우리는 이종망의 상태정보를 알 수 없는 모바일 노드가 네트워크의 상태정보를 받아 비교할 수 있도록 확장된 프로토콜을 제시하고, 시뮬레이션 연구에서 복잡도와 프로토콜 효율성에 따른 SmartCAC 평가를 수행하여 복잡도는 낮추고 효율성은 높이는 결과를 얻는다.